Landing

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netLANDING GEAR

LANDING GEAR SYSTEMS Learning Objective: Identify the various types of landing gear systems used on fixed-wing and rotary-wing aircraft. Every aircraft maintained in today is equipped with a landing gear system. Most aircraft also use arresting and catapult gear. The landing gear is that portion of the aircraft that supports the weight of the aircraft while it is on the ground. The landing gear contains components that are necessary for taking off and landing the aircraft safely. Some of these com-ponents are landing gear struts that absorb landing and taxiing shocks; brakes that are used to stop and, in some cases, steer the aircraft; nosewheel steering for steering the aircraft; and in some cases, nose catapult com-ponents that provide the aircraft with carrier deck takeoff capabilities. FIXED-WING AIRCRAFT Landing gear systems in fixed-wing aircraft are similar in design. Most aircraft are equipped with the tricycle-type retractable landing gear. Some types of landing gear are actuated in different sequences and directions, but practically all are hydraulically operated and electrically controlled. With a knowledge of basic hydraulics and familiarity with the operation of actuating system components, you should be able to understand the operational and troubleshooting procedures for landing gear systems. Main Landing Gear The typical aircraft landing gear assembly consists of two main landing gears and one steerable nose landing gear. As you can see in figure

Figure 12-1.Tricycle landing gear. is installed under each wing. Because aircraft are different in size, shape, and construction, every landing gear is specially designed. Although main landing gears are designed differently, all main gear struts are attached to strong members of the wings or fuselage so that the landing shock is distributed throughout the main body of the structure. The main gears are also equipped with brakes that are used to shorten the landing roll of the aircraft and to guide the aircraft during taxiing. Nose Landing Gear On aircraft with tricycle landing gear, the nose gear is retracted either rearward or forward into the aircraft fuselage. Generally, the nose gear consists of a single shock strut with one or two wheels attached. On most aircraft the nose gear has a steering mechanism for taxiing the aircraft. The mechanism also acts as a shimmy damper to prevent oscillation or shimmy of the nosewheel. Since the nosewheel must be centered before it can be retracted into the wheel well, a centering device aligns the strut and wheel when the weight of the aircraft is off the

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netgear. Flight instruments Most aircraft have these flight instruments: Altimeter

The altimeter shows the aircraft's altitude above sea-level by measuring the difference between the pressure in a stack of aneroid capsules inside the altimeter and the atmospheric pressure obtained through the static system. It is adjustable for local barometric pressure which must be set correctly to obtain accurate altitude readings. As the aircraft ascends, the capsules expand as the static pressure drops therefore causing the altimeter to indicate a higher altitude. The opposite occurs when descending. Attitude indicator

The attitude indicator (also known as an artificial horizon) shows the aircraft's attitude relative to the horizon. From this the pilot can tell whether the wings are level and if the aircraft nose is pointing above or below the horizon. This is a primary instrument for instrument flight and is also useful in conditions of poor visibility. Pilots are trained to use other instruments in combination should this instrument or its power fail.

Schempp-Hirth Janus-C glider Instrument panel equipped for "cloud flying". The turn and bank indicator is top center. The heading indicator is replaced by a GPS-driven computer with wind and glide data, driving two electronic variometer displays to the right. Airspeed indicator

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The airspeed indicator shows the aircraft's speed (usually in knots ) relative to the surrounding air. It works by measuring the ram-air pressure in the aircraft's pitot tube. The indicated airspeed must be corrected for air density (which varies with altitude, temperature and humidity) in order to obtain the true airspeed, and for wind conditions in order to obtain the speed over the ground. Magnetic compass

The compass shows the aircraft's heading relative to magnetic north. While reliable in steady level flight it can give confusing indications when turning, climbing, descending, or accelerating due to the inclination of the Earth's magnetic field. For this reason, the heading indicator is also used for aircraft operation. For purposes of navigation it may be necessary to correct the direction indicated (which points to a magnetic pole) in order to obtain direction of true north or south (which points to the Earth's axis of rotation). Heading indicator

The heading indicator (also known as the directional gyro, or DG; sometimes also called the gyrocompass, though usually not in aviation applications) displays the aircraft's heading with respect to geographical north. Principle of operation is a spinning gyroscope, and is therefore subject to drift errors (called precession) which must be periodically corrected by calibrating the instrument to the magnetic compass. In many advanced aircraft (including almost all jet aircraft), the heading indicator is replaced by a Horizontal Situation Indicator (HSI) which provides the same heading information, but also assists with navigation Turn indicator

The turn indicator displays direction of turn and rate of turn. Internally mounted inclinometer displays 'quality' of turn, i.e. whether the turn is correctly coordinated, as opposed to an uncoordinated turn, wherein the aircraft would be in either a slip or a skid. The original turn and bank indicator was replaced in the late 1960s and early '70s by the newer turn coordinator, which is responsive to roll as well as rate of turn, the turn and bank is typically only seen in aircraft manufactured prior to that time, or in gliders manufactured in Europe. Vertical speed indicator

The VSI (also sometimes called a variometer). Senses changing air pressure, and displays that information to the pilot as a rate of climb or descent in feet per minute, meters per second or knots.

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netAdditional panel instruments that may not be found in smaller aircraft include: Course deviation indicator

The CDI is an avionics instrument used in aircraft navigation to determine an aircraft's lateral position in relation to a track, which can be provided by a VOR or an Instrument Landing System. This instrument can also be integrated with the heading indicator in a horizontal situation indicator. Radio Magnetic Indicator

An RMI is generally coupled to an automatic direction finder (ADF), which provides bearing for a tuned Non-directional beacon (NDB). While simple ADF displays may have only one needle, a typical RMI has two, coupled to different ADF receivers, allowing for position fixing using one instrument. Layout

Six basic instruments in a light twin-engine airplane arranged in a "basic-T". From top left: airspeed indicator, attitude indicator, altimeter, turn coordinator, heading indicator, and vertical speed indicator Most aircraft are equipped with a standard set of flight instruments which give the pilot information about the aircraft's attitude, airspeed, and altitude. T arrangement Most aircraft built since about 1953 have four of the flight instruments located in a standardized pattern called the T arrangement. The attitude indicator is in the top center, airspeed to the left, altimeter to the right and heading indicator under the attitude indicator. The other two, turn-coordinator and vertical-speed, are usually found under the airspeed and altimeter, but are given more latitude in placement. The magnetic compass will be above the instrument panel, often on the windscreen centerpost. In newer aircraft with glass cockpit instruments the layout of the displays conform to the basic T arrangement. Basic Six In 1937 the Royal Air Force (RAF) chose a set of six essential flight instruments which would remain the standard panel used for flying in Instrument Meteorological Conditions (IMC) for

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netthe next 20 years. They were: airspeed indicator (knots) attitude indicator vertical speed indicator (rate of climb) altimeter directional gyro (compass) turn and bank indicator (aircraft attitude) This panel arrangement was incorporated into every RAF aircraft, from the light Tiger Moth, to the heavy Avro Lancaster, and minimized the type-conversion difficulties associated with Blind Flying, since a pilot trained on one aircraft could quickly become accustomed to any other if the instruments were identical. This Basic Six set, also known as a six pack[1], was also adopted by commercial aviation. After the Second World War the arrangement was changed to: (top row) airspeed, artificial horizon, altimeter, (bottom row) radio compass, direction indicator, vertical speed.

AIRCRAFT HARDWARE What You Need To Know By Ron Alexander The quality of our workmanship in building an airplane is very important. We all take the needed time and spend the necessary money to ensure we have a high quality airplane. We want it to not only look attractive, but also to be safe. But what about the materials that hold the airplane together the aircraft hardware? Do we try to cut expenses by using questionable bolts or used nuts? Is it really necessary to spend money on high quality aircraft hardware? Absolutely! The hardware used to assemble your airplane should be nothing but the best. Why take the time to build a perfect wing only to attach it to the fuselage with used hardware. It makes no sense. To quote the Airframe and Powerplant Mechanics General Handbook . . . "The importance of aircraft hardware is often overlooked because of its small size; however, the safe and efficient operation of any aircraft is greatly dependent upon the correct selection and use of aircraft hardware." Very well stated. The same book also provides us with a very good definition of aircraft hardware. "Aircraft hardware is the term used to describe the various types of fasteners and miscellaneous small items used in the manufacture and repair of aircraft." The subject of aircraft hardware can certainly be confusing. Thousands upon thousands of small items are used on a typical airplane. What does the custom aircraft builder really need to know about hardware? Where do you find the information? What reference is really the end authority on proper installation? What do all of those AN numbers mean and do I have to know them? What types of hardware should I really learn more about in order to build my own airplane? These questions will be answered in this series of articles on aircraft hardware. I hope to eliminate some confusion over what type of hardware to use and how to properly install it. To begin our discussion, it is absolutely imperative that you use nothing but aircraft grade hardware. Commercial grade hardware found in hardware or automotive stores is legal to use on an experimental airplane but should not be considered for even a moment. Why? Let's look at bolts as an example. Common steel bolts purchased from a hardware store are made of low carbon steel that has a low tensile strength usually in the neighborhood of 50,000 to 60,000 psi. They also bend easily and have little corrosion protection. In contrast, aircraft bolts are made from corrosion resistant steel and are heat treated to a strength in excess of 125,000 psi.

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netThe same comparison applies to most hardware items. So, use only aircraft quality hardware on your airplane. Save the other hardware for your tractor. If aircraft hardware is special, then there must be a standard against which it should be measured and manufactured. That standard was actually developed prior to World War 11, but became more definitive during that war. Each branch of the military originally had its own standard for hardware. As time went on these standards were consolidated and thus the term AN which means Air Force-Navy (some prefer the older term Army-Navy). Later the standards were termed MS which means Military Standard and NAS which means National Aerospace Standards. Thus, the common terms AN, MS and NAS. Together they present a universally accepted method of identification and standards for aircraft hardware. All fasteners are identified with a specification number and a series of letters and dashes identifying their size, type of material, etc. This system presents a relatively simple method of identifying and cataloging the thousands and thousands of pieces of hardware. Several pieces of hardware will have both an AN number and an MS number that are used interchangeably to identify the exact same piece. A cross reference exists that compares these two numbers. So in the end, you are able to read your plans or assembly manual and identify, by number and letter, each piece of hardware on your airplane. You can then obtain that piece and properly install it in the right place. Imagine trying to do that without a system of numbers. The specifications for each piece of hardware also define the strength, tolerance, dimensions, and finish that is applied. If you would like further information on this numbering system, you can contact the National Standards Association in Washington, DC.

FIGURE 1 Out of all the thousands of hardware pieces manufactured, which ones are important to the custom aircraft builder? The following types and categories of hardware will be discussed: Bolts Nuts Washers Screws Cotter pins and safety wire

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netRivets Turnlock fasteners Miscellaneous items such as 0-rings, crush washers, etc. Control cable hardware Fluid lines and fittings Electrical wiring and connectors Where do you find information concerning aircraft hardware? Your aircraft plans or assembly manual should provide you with a general overview of hardware used on your project. Use the hardware the aircraft designer or kit manufacturer recommends. Do not substitute with your own ideas. This can be dangerous. The manufacturer has tested the design and its safety is dependent upon the proper pieces of hardware. FAA Advisory Circular 43-13-IA is an excellent reference source. The Airframe Mechanics General Handbook also has a very good section on the selection and use of hardware. These two books are considered the primary authority on the proper use of hardware. In addition, I would recommend two other small reference books: the Standard Aircraft Handbook and the Aviation Mechanic Handbook. Both of these provide a good reference source. The Aircraft Spruce & Specialty catalog also contains good reference material on hardware. If you have any doubts about the quality of the aircraft hardware you are purchasing, request a copy of the manufacturer's specifications. These specifications along with a specific manufacturer's lot number should be available. BOLTS Bolts are used in aircraft construction in areas where high strength is needed. Where this strength is not necessary screws are substituted. Aircraft quality bolts are made from alloy steel, stainless or corrosion resistant steel, aluminum alloys and titanium. Within our industry the first two are the most common. Aircraft bolts will always have a marking on their head. If you see no markings at all on the head of a bolt, do not use it. It is probably a commercial grade bolt. The markings on bolts vary according to the manufacturer. You should see an "X" or an asterisk along with a name, etc. If you purchase a corrosion resistant (stainless steel) bolt, the head of that bolt should have one raised dash. An aluminum bolt will have two raised dashes on its head. Aluminum bolts have limited use. They should not be used in tension applications or where they will be continuously removed for maintenance or inspection. A chart of typical bolt heads is presented in Figure 1. NAS bolts have a higher tensile strength (usually about 160,000 psi) and can be identified by a cupped out head. Close tolerance bolts are machined more accurately than general purpose bolts and they are used in applications requiring a very tight fit. Close tolerance bolts can be either AN or NAS and typically have a head marking consisting of a raised or recessed triangle. The standard bolts used in aircraft construction are AN3 through AN20. Each bolt typically has a hexagon shaped head and a shank that fits into the hole. The shank is threaded on the end and the unthreaded portion of the bolt is termed the grip. The diameter of a bolt is the width of the grip. The shank of a bolt will be either drilled to accept a cotter pin or undrilled. Another option is to purchase a bolt that has the head drilled for the purpose of accepting safety wire. Clevis bolts are manufactured with a slotted head and are used for control cable applications. The size, material, etc. of a bolt is identified by an AN number. A breakdown of a typical bolt AN number follows: AN4-8A AN means the bolt is manufactured according to Air Force-Navy specs. 4 identifies the diameter of the bolt shank in 1/16" increments 8 identifies the length of the shank in 1/8" increments

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netA means the shank of the bolt is undrilled (no letter here means a drilled shank) So, this particular bolt is a 1/4 inch diameter AN bolt that is 1/2 inch long measured from just under the head to the tip of the shank. The bolt also has an undrilled shank which means it cannot accept a cotter pin. Also, bolt length may vary by +1/32" to -1/64". If the letter "C" follows the AN designation (ANC) that identifies a stainless steel bolt. The letter "H" after AN (ANH) identifies a drilled head bolt. FIGURE 2: AN Aircraft Bolt Dimensions In constructing you airplane, you will not encounter many bolts larger than an AN8 (1/2 inch diameter). To add a bit more confusion, if the dash number defining the length of the bolt has two digits, the first digit is the length in whole inches and the second number the length in additional 1/8" increments. In other words, an AN514 bolt would be I- 1/2 inches long. Now that you are totally confused let me recommend a hand tool to simplify bolt selection and sizing. An AN bolt gauge is available that will assist you in identifying a bolt (click on the above link to Figure 2). If you need to determine the proper size of a bolt, the length must be sufficient to ensure no more than one thread will be inside the bolt hole. This is the grip length of the bolt and it is measured from the underneath portion of the head to the beginning of the threads (see Figure 3 below). The grip length should be equal to the material thickness that is being held by the bolt or slightly longer. A washer may be used if the bolt is slightly longer. A piece of welding rod or safety wire can be used to measure the length of the hole. In his book titled Sportplane Construction Techniques, Tony Bingelis shows a simple tool that can be made for this purpose.

FIGURE 3 It is important that you do not "over tighten" or "under tighten" a bolt or the nut attached to a bolt. Under torque or under tightening results in excessive wear of the hardware as well as the parts being held. Over tightening may cause too much stress on the bolt or nut. The best way to avoid this is to use a torque wrench. AC43-13 presents a table of torque values for nuts and bolts. It shows fine thread and coarse thread series with a minimum and maximum torque limit in inch pounds. I recommend using a torque wrench whenever possible, at least until you get an idea as to the amount of force required. Of course, critical installations should definitely be torqued to proper values. A torque wrench is not that expensive and will be a worthwhile investment for a custom builder. Basics of Bolt Installation Certain accepted practices prevail concerning the installation of hardware. A few of these

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netregarding bolt installation follow: 1. In determining proper bolt length - no more than one thread should be hidden inside the bolt hole. 2. Whenever possible, bolts should be installed pointing aft and to the center of an airplane. 3. Use a torque wrench whenever possible and determine torque values based on the size of bolt. 4. Be sure bolt and nut threads are clean and dry. 5. Use smooth, even pulls when tightening. 6. Tighten the nut first - whenever possible. 7. A typical installation includes a bolt, one washer and a nut. 8. If the bolt is too long, a maximum of three washers may be used. 9. If more than three threads are protruding from the nut, the bolt may be too long and could be bottoming out on the shank. 10. Use undrilled bolts with fiber lock nuts. If you use a drilled bolt and fiber nut combination, be sure no burrs exist on the drilled hole that will cut the fiber. 11. If the bolt does not fit snugly consider the use of a close tolerance bolt. 12. Don't make a practice of cutting off a bolt that is too long to fit a hole. That can often weaken the bolt and allow corrosion in the area that is cut. AIRCRAFT NUTS Aircraft nuts usually have no identification on them but they are made from the same material as bolts. Due to the vibration of aircraft, nuts must have some form of a locking device to keep them in place. The most common ways of locking are cotter pins used in castle nuts, fiber inserts, lockwashers, and safety wire. The aircraft nuts you will most likely encounter are castle nuts, self-locking nuts, and plain nuts. Wing nuts and anchor nuts are also used. Castle Nuts AN310 and AN320 castle nuts are the most commonly used (see Figure 4). Castle nuts are fabricated from steel and are cadmium plated. Corrosion resistant castle nuts are also manufactured (AN310C and AC320C - remember, when you encounter a "C" it will designate stainless). Castle nuts are used with drilled shank bolts, clevis bolts and eye bolts. The slots in the nut accommodate a cotter pin for safetying purposes. The thinner AN320 castellated shear nut has half the tensile strength of the AN310 and is used with clevis bolts which are subject to shear stress only. The dash number following the AN310 or AN320 indicates the size bolt that the nut fits. In other words, an AN310-4 would fit a 1/4 inch bolt.


FIGURE 4 Self-Locking Nuts Self-locking nuts, as the name implies, do not need a locking device. The most common method of locking is derived from a fiber insert. This insert has a smaller diameter than the nut itself so that when a bolt enters the nut it taps into the fiber insert producing a locking action. This fiber insert is temperature limited to 250-deg. F. The designation of these nuts is AN365 and AN364. This brings us to an example of a cross-reference MS number. An AN365 is also termed MS20365 with the AN364 being MS20364. Both of these nuts are available in stainless. The AN364 is a shear nut not to be used in tension. An all metal locking nut is used forward of the firewall and in other high temperature areas. In place of a fiber insert, the threads of a metal locking nut narrow slightly at one end to provide more friction. An AN363 is an example of this type of nut. It is capable of withstanding temperatures to 550-deg. F. The dash number following self-locking nut defines the thread size. Self-locking nuts are very popular and easy to use. They should be used on undrilled bolts. They may be used on drilled bolts if you check the hole for burrs that would damage the fiber. One disadvantage, self-locking nuts should not be used on a bolt that is connecting a moving part. Am example might be a clevis bolt used in a control cable application. Plain Aircraft Nuts Plain nuts require a locking device such as a check nut or lockwasher. They are not widely used in most aircraft. AN315 is the designation used for a plain hex nut. These nuts are also manufactured with a right hand thread and a left hand thread. The check nut used to hold a plain nut in place is an AN316. If a lockwasher is used a plain washer must be under the lockwasher to prevent damage to the surface. Other Aircraft Nuts There are a number of other aircraft nuts available. Wing nuts (AN350) are commonly used on battery connections or hose clamps where proper tightness can be obtained by hand. Anchor nuts are widely used in areas where it is difficult to access a nut. Tinnerman nuts, instrument mounting nuts, pal nuts, cap nuts, etc. are all examples of other types that are used. Basics of Aircraft Nut Installation 1. When using a castle nut, the cotter pin hole may not line up with the slots on the nut. The Mechanics General Handbook states "except in cases of highly stressed engine parts, the nut may be over tightened to permit lining up the next slot with the cotter pin hole." Common sense should prevail. Do not over tighten to an extreme, instead, remove the nut and use a different washer and then try to line the holes again. 2. A fiber nut may be reused if you are unable to tighten by hand.

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.net3. At least one thread should be projecting past the fiber on a fiber nut installation. 4. No self-locking nuts on moving part installations. 5. Do not use AN364 or AN365 fiber nuts in areas of high temperature - above 250' F. 6. Shear nuts are to be used only in shear loads (not tension). 7. Plain nuts require a locking device such as a lockwasher or a check nut. 8. When using a lockwasher, place a plain washer between the surface of the airplane part and the lockwasher. 9. Shear nuts and standard nuts have different torque values. 10. Use wing nuts only where hand tightness is adequate. WASHERS Finally, a hardware item that is simple. You are likely to encounter only a couple of different types of washers AN960 and AN970. The main purposes of a washer in aircraft installation are to provide a shim when needed, act as a smooth load bearing surface, and to adjust the position of castle nuts in relation to the drilled hole in a bolt. Also, remember that plain washers are used under a lockwasher to prevent damage to a surface. AN960 washers are the most common. They are manufactured in a regular thickness and a thinner thickness (one half the thickness of regular). The dash number following the AN960 indicates the size bolt for which they are used. The system is different from others we have encountered. As an example, an AN960-616 is used with a 3/8" bolt. Yet another numbering system. If you see "L" after the dash number, that means it is a thin or "light" washer. An AN960C would be - yes, a stainless washer. I can tell you are getting more familiar with the system so I will throw another wrench into the equation - an AN970 washer has a totally different dash number system. I am not even going to tell you what it is. I will tell you that an AN970 is a larger area flat washer used mainly for wood applications. The wider surface area protects the wood. There are other types of washers. I mentioned lockwashers that are made several different ways. They are often split ring, they are sometimes internal tooth and even external tooth (see Figure 5). You will also find nylon washers and finishing washers that usually have a countersunk head. So, as you can see, washers are not quite as confusing as other hardware even though we can make ft difficult if we wish.

FIGURE 5 COTTER PINS AND SAFETY WIRE The cotter pins mostly used on custom aircraft are AN380 and AN381. Cadmium plated cotter pins are AN380 and stainless are AN381. Cotter pins are used for safetying bolts, screws, nuts and other pins. You will normally use them with castle nuts. The MS number you may see is MS24665. The dash numbers indicate diameter and length of the pin. As an example,

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netAN380-2-2 would be a cadmium plated pin 1/16" in diameter and 1/2" long. All supply companies will have charts showing the various sizes versus the reference number. Safety wire is also widely used. The most used sizes in diameter are .020, .032 and .041 or small variations thereof. The material is usually stainless steel or brass. The easiest method of installation is acquired by using safety wire pliers (see Figure 6). The pliers are used to twist the wire. The wire is installed so that if the nut or bolt begins to loosen it will increase the tension on the wire. Be sure you do not overtwist the wire - doing so will weaken the safety wire. Leave about 36 twists and then cut off the excess wire and bend its end so you do not snag it with your hand at a later time.

FIGURE 6 I want to emphasize the major point of this article. USE ONLY AIRCRAFT QUALITY HARDWARE. Do not assume the engineer role by using hardware types or sizes that are contrary to your plans or assembly manual. In future articles I will discuss the other hardware items including control cable installation, screws, rivets, turnlock fasteners, etc.

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DATE:05/10/10 SOURCE:Flight International APU: Unsung hero of the engine world By John Croft


Auxiliary power units (APUs) do their dull and dirty work hidden away in aircraft tailcone compartments, unlike their turbine engine brethren connected to the wings or empennage. On occasion however, the tables get turned. On a bitterly cold Thursday in January 2009, the Honeywell 131-9A APU in the tailcone of a US Airways A320 that had just departed New York's LaGuardia airport came to the rescue after the aircraft struck a flock of geese. With both CFM56 turbofans damaged and the associated electrical generators eventually knocked off line, the APU during the final seconds of the ditching provided the power needed to keep the flight controls, displays and envelope protections in place to allow the pilot to touch down in the Hudson River in control and at the lowest possible airspeed.


APUs such as Honeywell's 331-200ER in this Continental 767 are meant to be out of sight, out of mind. Picture: Ed Croft That the APU was available so quickly was testament to a well-trained crew. During the final hearing earlier this year on the successful, fatality-free ditching, a National Transportation Safety Board official asked the captain: "According to the [cockpit voice recorder] transcript, immediately after the bird strike, you called for the ignition to 'on' and to start the APU. This was before beginning the checklist. Can you explain your decision to do this?" To which Captain Sullenberger replied: "From my experience, I knew that those two steps would be the

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netmost immediate help to us in this situation." That the APU was able to start and perform without question when needed was testament to the pedigree of these small compact turbine engines. The two primary manufacturers of the engines, Honeywell and Hamilton Sundstrand, continue to refine the devices and are preparing a raft of new technologies aimed at boosting reliability and "on-tail" time while decreasing emissions and fuel burn. APUs are generally used to provide cabin air on the ground, pneumatic pressure for engine starts and primary or back-up electrical power for environmental, cockpit and hydraulic systems. They use the same fuel as the aircraft's engines and generally account for about 2% of the total fuel burn on a given mission. Market leader Honeywell, whose APUs are standard on all Boeing 737NG models and have been selected as an option on 60% of Airbus A320s, is readying its most advanced APUs to date for the new Comac 919 single-aisle jet and the Airbus A350. Both APUs are derivatives of the company's popular 131-9 model, which is also on tap for the new Bombardier CSeries narrowbody line. A near-term technology focus for Honeywell has been extending the life of the gas turbine wheels in the APU by moving to a one-piece turbine wheel rather than a hub with replaceable blades. Both Honeywell and Hamilton Sundstrand use a single-spool engine architecture with a single-stage centrifugal compressor, combustors and two-stage high-pressure turbine. Overall pressure ratio is approximately 11:1 with peak temperatures in the neighbourhood of 2,000F (1,090C) for Honeywell's Airbus A350 design. The spool also drives an electrical generator and a compressor for pneumatic air flow to the aircraft's environmental control system and engine start system. The 131-9 typically drives a 90kV or 120kV generator and provides up to 168lb/min (76kg/min) pneumatic pressure, says Steven Chung, vice-president for marketing and product management for the APU line at Honeywell. Chung says the company has shipped more than 6,000 131-9 series APUs since 1991, when it was first developed for the McDonnell Douglas MD90.

LIFE INCREASE Honeywell says the dual-alloy one-piece turbine wheels will provide some operators with a 10-20% increase in APU life, which for the 131-9 is on average about 12,000h time before overhaul (TBO). Interim maintenance typically includes replacing certain line replaceable units

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.net(LRU) during the life of the APU in part due to internal wearing of valves, mating materials and springs. Replacement parts include igniter plugs and filters. "In hot climates with lots of pollution, particularly India and the Middle East, sulphur was building up on the blades and corrosion was an issue," says Mike Madsen, vice-president of airlines for Honeywell. "This change eliminates that issue." Madsen explains that the dual alloy turbine wheel is fabricated with a hub that is fused to a ring of integral blades, an optimal design that, he says, eliminates potential for certain failures, thereby decreasing removal by 10-20% in regions such as China, India and the Middle East, where APUs are operated "pretty consistently" on the ground due to a lack of land-based electrical power service. "It really attacks the potential failure modes you can experience," says Madsen. "One of the challenges you have with an APU is that it operates on the ground and ingests air that is not as clean as the air at altitude. This can lead to accelerated wear on engine." He says the one-piece design eliminates the nooks and crannies where corrosion from salts and other contaminants can begin. Like Hamilton Sundstrand, Honeywell offers an option to customers to monitor APUs in the field using temperature and vibration measured on board the aircraft at certain times and sent to the ground via the aircraft communications addressing and reporting system. "In some cases, this allows airline to change out the questionable unit with an operational APU and get the other fixed," says Madsen. Airlines in some cases own their own spares and in other cases, purchase an integrated service solutions programme, whereby Honeywell manages the spares and provides them to the carriers when a failed unit is returned. Honeywell also has a rental bank and aircraft-on-ground (AOG) units available. Madsen says about 60-70% of customers contract with Honeywell for full support of their APUs on a cost per hour basis. Along with licensed maintenance providers, customers can obtain services at the company's facilities in Germany, Singapore and at Honeywell's home base in Phoenix, Arizona. Many airlines, typically the legacy carriers, have their own APU maintenance facilities. "We are in the process of facilitating Air China, China Eastern and China Southern to do their own maintenance on APUs," says Madsen, adding that the company also has an APU maintenance facility in China.

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netCARE PROGRAMME Hamilton Sundstrand offers a power-by-the-hour care programme, with the main company-owned maintenance centre in San Diego, a facility in Northern France and a sister company (Pratt & Whitney) facility in Singapore. Third-party provider, StandardAero, also performs maintenance on the units. "We set up many airlines that want to do their own in-house repair," says Danny Di Perna, vice-president and general manager of Hamilton Sundstrand Auxiliary Power Systems. "We provide them tooling and documents and we can set up the operation as turnkey if desired." A network of field service representatives help with AOG situations but Hamilton Sundstrand does not maintain a pool of spares. The company has increased its warranty up to four years or 4,000h, up from the typical three-year warranty of legacy systems. Like Honeywell, Hamilton Sundstrand's APUs are maintained on-condition and tend to last 12,000hr or more. Hamilton Sundstrand says it has 5,000 APUs in total for the commercial aircraft market in operation, including 1,600 APS3200 APUs for single-aisle aircraft. Di Perna says 60-70% of the airline customers are using the data trending service. To better keep track of APU performance and potential problems in the field, Hamilton Sundstrand is building a 253m2 (2,720ft2) customer response centre for its APUs in Windsor Locks, Connecticut. The facility will be completed later this year. Madsen says Honeywell has 20 APUs retrofitted with the dual alloy turbine wheel in the second-stage turbine slot flying as part of an evaluation - 10 on Boeing aircraft and 10 on Airbus aircraft. As of mid-September, the units had accumulated 20,000h operating time in total with no failures. Honeywell plans to have accumulated 50,000h operating time on the 20 units by mid-2011. Starting in June 2011, the company will introduce the new turbine wheels for both high-pressure stages for new and aftermarket models. For overhauls, where the existing units will receive the new turbine wheels, Honeywell says turn-time will be reduced about half a day since the single-piece wheels will be pre-balanced at the factory. Turn time in total for an APU is 20-25 days, says Madsen. Major drivers for next-generation APUs include cutting weight and improving reliability, along with reducing fuel burn and lowering emissions. Chung says goals for the Bombardier APU include a 15% reduction in overall fuel burn over a mission profile, a design driver that stems from desired sales in European markets. For the Airbus A350, Honeywell's HGT1700 APU will be its largest unit to date, delivering an equivalent power of 1,300kW (1,700shp) but cutting fuel burn and nitrogen oxide emissions with a new variable speed controller, also to be included in the APUs for the CSeries and Comac C919. The variable speed controller runs the APU at an optimal speed based on ambient temperature, altitude and bleed air or generator demands, says Honeywell's Chung. For the 131-9, the controller will vary the speed of the APU within 10% of its nominal run speed of 48,800rpm. Quieter APUs are also in demand, particularly in Europe and for East and West Coast US airports, says Chung. He says many airlines are asking for APUs that generate 3-10dB less than current international noise standards. "A lot of the noise has to do with APU emissions," says Chung. "That's where we come in with installation kits for the air inlet and exhaust to quieten it down." Other means of cutting noise include choosing blade counts for the compressor and turbines to push the noise above the audible range, he says. For the C919, Honeywell has a patented tailcone muffler design that quietens the overall noise of the APU when integrated to the aircraft. Hamilton Sundstrand is introducing its first variable speed APU to the commercial market in the Boeing 787 with its APS5000. Unlike traditional APUs, the APS5000 drives two 225kV generators only, making it the first "all-electric" APU, says Hamilton Sundstrand. "It's remarkably quiet," says Di Perna. "There's no bleed-air provided." Di Perna says testing of the APS5000 is "just about wrapping up" and certification is expected in November. Other new

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netcommercial aircraft wins include the ARJ21, Mitsubishi Regional Jet and Irkut MC21. Beyond the 787, Hamilton Sundstrand plans to take advances from the 787 programme into a new line of single-aisle APUs, a strategy aimed at taking market share from its competitor. Di Perna says Honeywell is dominant in the single-aisle market, with a 75-80% share compared with Hamilton Sundstrand's 20-25%. "We're trying to get 35-45% market share in the next seven years," says Di Perna. He says both companies have approximately 40% market share in military APUs and 50% each for regional aircraft.

Aircraft Procedure - Introduction Pilots are highly trained professionals who fly airplanes and helicopters to carry out a wide variety of tasks. Except on small aircraft, two pilots usually make up the cockpit crew. Generally, the most experienced pilot, the captain, is in command and supervises all other crew members. The pilot and copilot share flying and other duties, such as communicating with Air Traffic Controllers and monitoring the instruments. Some large aircraft have a third pilotthe flight engineerwho assists the other pilots by monitoring and operating many of the instruments and systems, making minor in flight repairs, and watching for other aircraft. (but nowadays this duty is performed by pair of computers) New technology can perform many flight tasks, however, and virtually all new aircraft now fly with only two pilots, who rely more heavily on computerized controls. As older, less technologically sophisticated aircraft continue to be retired from airline fleets, the number of flight engineer jobs will decrease.

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netBefore departure, pilots plan their flights carefully. They thoroughly check their aircraft to make sure that the engines, controls, instruments, and other systems are functioning properly. They also make sure that baggage or cargo has been loaded correctly. They confer with flight Dispatchers and aviation weather forecasters to find out about weather conditions en route and at their destination. Based on this information, they choose a route, altitude, and speed that will provide the fastest, safest, and smoothest flight. When flying under instrument flight rulesprocedures governing the operation of the aircraft when there is poor visibilitythe pilot in command, or the airline dispatcher, normally files an instrument flight plan with air traffic control so that the flight can be coordinated with other air traffic. Takeoff and landing are the most difficult parts of the flight, and require close coordination between the pilot and first officer. For example, as the plane accelerates for takeoff, the pilot concentrates on the runway while the first officer scans the instrument panel. To calculate the speed they must attain to become airborne, pilots consider the altitude of the airport, outside temperature, weight of the plane, and speed and direction of the wind. The moment the plane reaches takeoff speed, the first officer informs the pilot, who then pulls back on the controls to raise the nose of the plane. Unless the weather is bad, the actual flight is relatively easy. Airplane pilots, with the assistance of autopilot and the flight management computer, steer the plane along their planned route and are monitored by the air traffic control stations they pass along the way. They regularly scan the instrument panel to check their fuel supply, the condition of their engines, and the air-conditioning, hydraulic, and other systems. Pilots may request a change in altitude or route if circumstances dictate. For example, if the ride is rougher than expected, they may ask air traffic control if pilots flying at other altitudes have reported better conditions. If so, they may request an altitude change. This procedure also may be used to find a stronger tailwind or a weaker headwind to save fuel and increase speed. Pilots must rely completely on their instruments when visibility is poor. On the basis of altimeter readings, they know how high above ground they are and whether they can fly safely over mountains and other obstacles. Special navigation radios give pilots precise information that, with the help of special maps, tells them their exact position. Other very sophisticated equipment provides directions to a point just above the end of a runway and enables pilots to land completely blind. Here the air traffic engineers play major role to keep the ground equipment to their absolute specification for "blind" landing. Once on the ground, pilots must complete records on their flight for their organization and the FAA. report. Although flying does not involve much physical effort, the mental stress of being responsible for a safe flight, no matter what the weather, can be tiring. Pilots must be alert and quick to react if something goes wrong, particularly during takeoff and landing.

Simple lesson plan to fly Flight Plans Pilots wishing to fly under IFR rules must first file a flight plan with Air Traffic Control, before departure. Calling the Aeronautical Information Office can do this. The flight plan contains the aircraft identification, or callsign, the type of aircraft, planned speed (true airspeed, or speed across the ground without wind), requested route of flight (from VORTAC to VORTAC), planned cruising altitude, and sometimes other information such as color of aircraft, and number of people on board. We will discuss all these later and for the time being have these in mind.

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netThis flight plan information goes into the Air Traffic Controllers and they prepare a strip of paper called a flight progress strip. After that, controllers can review the proposed route of flight and make changes as necessary to conform to local procedures and routings. When the aircraft is ready to depart, the pilot calls either the control tower and requests clearance. The controller checks the flight strip, and clarifies the routing and any changes to the routing with the pilot, so both pilot and Air Traffic Control know the exact route the pilot will fly. The controller also tells the pilot his flight plan code number, and the pilot sets an instrument on his aircraft called a transponder to transmit this code. This beacon code transmission is picked up by radar, allowing the ATC computer to know exactly which aircraft it is, and which flight plan it corresponds to. Getting started Imagine you enter the cockpit of a parked A340 - everything is ready except that all systems are shut down. APU (Auxiliary power unit) and engines are also switched off. Now both batteries are switched on at the Overhead ELEC panel.

Overhead ELEC (electrical) panel The next thing to do is to check the APU fire warning. To do this, the TEST button on the APU fire panel is depressed and released when the fire light illuminates.

APU fire warning Now the APU is switched on by pushing the MASTER switch on the APU panel.


APU panel When the "FLAP OPEN" message appears on the ECAM (Electrical Contactor and Management Unit) the APU start switch is depressed. When the AVAIL light illuminates, the APU bleed push button on the AIR panel is pushed to supply the air conditioning and other systems with air. Check the all panels for white lights out and turn the three IR switches to NAV for the alignment process. Refer to the following MCDU (Multifunction Control Display Unit) programming procedure. STATUS PAGE (PS) The DATA BASE validity must be checked at first, as well as the navaids and waypoints. FLIGHT PLAN Should be completed thoroughly. It includes data like: Take off runway, SID with ALT/SPD data, expected take off time, course, waypoints and the expected step climbs descents SEC FLIGHT PLAN Must be filled in when ever a specific condition is likely to happen such as take off runway change, alternative SID etc. RAD NAV (Radio and Navigation) Any required Navaids manually entered using ident. INIT Winds, expected ZFWCg (Zero Fuel Weight Center of Gravity / ZFW (Zero Fuel Center of

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netGravity), Fuel planning: The FMGS (Flight Management Guidance System) calculation the minimum required fuel this value must confirmed. After that, the DATA page is selected and the preflight data is printed out using the ACARS (Aircraft Communications Addressing and Reporting System). The printed sheet must be kept as it gives the required fuel for each waypoint of the Flight Plan. PERF (Performance) The derated climb and descents and speeds are typed in - this is necessary. Flight plan checked: MCDU: FPLN page ND (Navigation Display) in plan mode: range as required, with CSTR selected on EIS CTLE panel. ALT/SPD checked, Distance to successive waypoint is provided. The overall distance of the route is indicated in the 6th line of the MCDU Now the before Start Checklist (written on the table) can be completed. Before starting the engines, turn the beacon light on and seat belts to on. ATC communication Now check your departure time and you are ready for startup. Before that, contact the control tower (Aerodrome) for clearance for startup and pushback the aircraft to taxiway. Engine Start up The normal engine start procedure is the AUTO START procedure. In this case the FADEC prevents start malfunctions like hot start, stall etc. It recognizes all of these and takes appropriate actions for instance reducing fuel flow, cranking the engine, attempting new starts or cutting fuel flow. The air from the APU (APU bleed) allows to start 2 engines simultaneously.

The engine start up sequence is simple: 1 and 2 are started firstly to pressurize the green and blue system which supply the parking brakes and hydraulic actuators. An actuator is a little box that converts the electrical inputs to real rudder movements. The Boeing B707 for instance doesn't have this system. Engine 1 and 2 first, followed by 3 and 4. Check thrust levers idle.

Engine Start Then set IGN/START to START - now an eye must be kept on the ECAM to check if APU bleed is stable. ENG1 Master switch is set to ON followed by ENG 2 when N2 of Engine 1 has reached 10%. Now monitor and check in the right order: Start valve open (now high pressure bleed air (minimum 30psi) air is blown into the engine), N2 IGN A or B, Fuel flow, EGT OIL PRESS ignition rising. FADEC (Full Authority Digital Engine Control) closes the start valve

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netwhen N2 reaches 50%, now monitor EGT and ENG Vibration and the engine AVAIL which illuminates when the start sequence is over. Now the same is repeated for ENG 3 and 4. When all engines are running stable set the IGN / START switch back to NORM which automatically switches the Packs back ON. If, for any reasons, there is an abnormal start DO NOT interrupt the FADEC protective and just follow the ECAM instructions if they appear. Another procedure to start the engines is the MANUAL START, which is only used in exceptional cases, like high altitude airports or subsequent low APU bleed pressure or to CRANK the engine dry prior opening the fuel flow.


Overhead Panel Taxi When all engines are running check both left and right side for any obstacles let the tore bar to pull the aircraft on to the correct path from the apron. Again, contact the tower and get the

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netclearance to enter the taxiwayan most of the time you will be asked to enter the taxiway either to runway 22 or 04 and hold short of runway. Now, smoothly move the thrust levers forward only a few centimeters as otherwise you would blow everything away that is standing behind you and therefore you do not exceed N1 40% during taxi. The APU bleed should be turned off to avoid ingestion of exhaust gases by the passengers. On straight taxiway and shallow turns the pedals are used to steer the aircraft but the hand is kept on the steering tiller is used in sharp turns. Be careful with that - it is very sensitive so move this wheel very slowly. Also, when on the ground do not start turns too early. Remember that the nose gear on the A340 is far back (4 meters), this means that the cockpit has to be over the grass in an intersection. If you turn too early the main gear can end up in the grass so make sure to over steer significantly. Slowly move the thrust lever 1 (left one) slightly forward to make a right turn and use the right lever for number 4 engine slightly forward to make a left turn. It is not recommended to use differential braking to avoid gear stress. The speed shouldn't exceed 10 knots in turns also if brake temperature exceeds 150 degrees the brake fans (not installed in all aircraft) must be switched on. Remember to taxi slowly at about 10-12 knots. You usually do not use thrust reverser during taxi and it is used on old 737-200s or MD80s but not on the newer aircrafts. Extend the flaps to 1 + F the lever is located on the center panel and you simple pull the handle up and move it down one step. Make sure the stabilizer trim is in the green range and the rudder trim at zero. Take off Here you have come most critical point of your adventure. Contact the tower again and request for take off. You will be cleared to enter the runway and takeoff. When turning onto the runway, switch on the strobes and landing lights and align the aircraft on the center line and select Auto Brake MAX on the main instrument panel (below the gear indicator)In case of an engine failure the aircraft stops automatically when the thrust levers are moved to IDLE. Then push the CONFIG test on the ECAM so as to insure that the ECAM take off check list items are all green. If everything is set the thrust levers are moved slowly to 50% N1 and when all engines are running stable at 50% move the levers the stops (TOGA). A yellow arrow appears on the PFD indicating the acceleration. Now full concentration is needed to monitor speed, engine gauge and the aircraft on the centerline. At 90 knots, the rudder has to be used to keep the aircraft aligned with the centerline as at 100 knots the nose gear steering disconnects from the nose gear. This is actually the most tricky part of the take off run and in case of an engine failure it is difficult to keep the aircraft aligned with the center line as the airspeed is still to low for an effective rudder and the nose gear steering is disconnected. This is why much attention has to be paid on the engine gauges at this stage to react as early as possible. At 140 knots smoothly move the side stick backwards to gain a pitch attitude of 8 to avoid tail strike and then to 12-15 (depending on weigh). The Autopilot is available 5 seconds after take off. CLB/CRZ/DES(Climb/ Cruise/ Descend) When a stable positive rate of climb is established the gear is selected up and thrust reduced

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netto CLB at 1500feet. The flaps are retracted at 200kts but as this only a traffic pattern they are set to 1. In case of a traffic pattern, usually you maintain 1500 feet above ground. You can use the autopilot for the traffic pattern. Just press AP1 and Pull + rotate the altitude knob to 1500 and then pull it. Now select your desired heading - simply add 180 to your current heading to make a 180-degree turn to fly the downwind leg of the traffic pattern. From now on, until landing, the aircraft is under observation of the Air Traffic Control system. After departure, ATC issues altitudes, speeds, headings, and sometimes re-routes as necessary, and assumes responsibility for separating the aircraft from all known traffic. Landing Put the FLAP lever to 2 and select 160 knots airspeed. Now put the gear lever to down and the FLAP lever to 3. Select 140 knots speed. Before turning on final extend the flaps to FULL and arm the spoilers and push the Autobrake switch to Medium - you do not use Autobrake max during landing. Now the aircraft should be aligned with the runway centerline with the localizer display indicator and have an airspeed of 140 knots with the gear down and flaps set to FULL and a rate of descent of 700-800 feet per minute and a pitch angle of 4-5(but the actual landing angle should be 3). These parameters need to be monitored constantly - never fix your eyes on one parameter always keep all parameters in view. The PAPI will help you to establish the correct glide path. The PAPI (Precision Approach Position Indicator) consists of 4 lights which can illuminate red or white. If you see 2 red and 2 white lights than the glide path is correct - if 3 reds and 1 white is seen than slowly add power and smoothly pull the stick backwards to reduce the ROD. But most of you will know how this works either from real life or from the flight simulator. When passing 500 feet a voice message is heard indicating 500ft so monitoring altitude above ground does not have high priority. It is very important to keep the speed at 140 knots and if it is below 140kts then in most cases this will result in a hard landing if the speed is to high the aircraft will climb during the landing flare. Switch the Autopilot off by pressing the red side stick button twice and press one of the red buttons twice on the thrust levers to disengage the outthrust system. A short aural warning will be hared. Continue descent at 700 feet per minute until reaching 30 feet. Now reduce rate of descent to half and count slowly 1, 2, 3 while retarding the thrust lever to idle when the retard call is heard. Avoid push the stick forward if not absolutely necessary and this will increase the rate of descent and result in a hard landing. To make it correct always give very little side stick inputs and monitor what happens and if descending to fast pull the stick back again but always small inputs and monitor speed. Also remember a nice approach is almost a nice landing so if you monitored all parameters well a soft landing is not guaranteed. When the forward boogie touches the ground move the thrust reverser levers upwards and the spoilers will be extend automatically. Now the landing is not over at all and the nose gear has to be landed as well and if you keep it up to long it will just fall down and this is not very comfortable therefore, slowly move the side stick forward and give a little input and just see what happens. Shut down Take the next intersection and taxi to the apron. Push the spoiler lever down, retract the flaps to zero, switch off the strobes and landings lights and reduce speed to 10-12 knots. Make sure the APU is on when parking position is reached. Set parking brake and move the Engine Master switches to OFF one after another. Turn of the beacon light and seat belts. After the

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netaircraft lands, the flight plan is closed, and the pilot turns off his transponder.

How do they start jet engines on airplanes? Gas turbine engines come in many shapes and sizes. One type discussed in How turbine engines work includes a normal "jet" engine on an airplane. The hot gases produced by the burning fuel drive vanes in exactly the same way that wind turns a windmill. The vanes connect to a shaft that also spins the turbine's compressor. Another type of gas turbine engine, popular in tanks and helicopters, has one set of vanes for driving the compressor, as well as a separate set of vanes that drive the output shaft. In both of these types of engines, you need to get the main shaft spinning to start the engine. This starting process normally uses an electric motor to spin the main turbine shaft. The motor is bolted to the outside of the engine and uses a shaft and gears to connect to the main shaft. The electric motor spins the main shaft until there is enough air blowing through the compressor and the combustion chamber to light the engine. Fuel starts flowing and an igniter similar to a spark plug ignites the fuel. Then fuel flow is increased to spin the engine up to its operating speed. If you have ever been at the airport and watched a big jet engine start up, you know that the blades start rotating slowly. The electric starter motor does that. Then you (sometimes) hear a pop and see smoke come out of the back of the engine. Then the engine spins up and starts producing thrust. On smaller turbine engines (especially home-built models), another way to start the engine is to simply blow air through the air intake with a hair dryer or leaf blower. This technique has the same effect of getting air moving through the combustion chamber, but does not require the complexity or weight of an attached starter motor. Besides the starter shaft, most big jet engines include another output shaft for driving things like electrical generators, air conditioning compressors, etc. needed to operate the plane and keep it comfortable. This shaft can connect to the main turbine shaft at the same point the starter does or elsewhere. Some jet airplanes have a separate turbine (sometimes in the tail cone of the plane) that does nothing but generate auxiliary power. It is more efficient to run this smaller turbine when the plane is sitting on the tarmac.


Engine Lubrication, Part I With the correct oil friction losses in an engine are reduced to a minimum. This is done by taking into consideration circumstances as engine usage, ambient temperature, time of year and climate, location and engine design. The engine manufacturer usually recommends a certain type of oil to use regarding different circumstances.


Landing Gear Configurations Two main types: Conventional, and Tricycle

Tricycle Has nose wheel, which may be steerable Main gear, on either side Example: Cessna Keeps aircraft level during take-off and landing The most important advantage is its ease of ground handling.

Conventional Two main wheels One tail dragger wheel Reduced drag in the air

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netReduced landing gear weight Requires more skill in ground taxiing The most important advantage is the ability to operate the aircraft over rough terrain.

Classification of Landing Gear

Main landing gear Cushions landing impact Heavily stressed area Main Landing Gear consists of the main weight-bearing structure Auxiliary landing gear includes tail wheels, skids, nose wheels, etc. Nonabsorbing Landing Gear

Includes Rigid landing gear, Shock-cord landing gear, Spring landing gear Rigid: helicopters, sailplanes. No flexing other than the structure. Shock cord system: uses Bungee cords Spring type uses spring steel (some Cessnas)

Shock-Absorbing Landing Gear Dissipates landing energies by forcing fluid through a restriction This fluid generates heat, dissipated into the atmosphere Two types: Spring Oleo, and Air-Oil Oleo Spring Oleo is history by now Air Oleos are all very similar: a needle valve restricts fluid flow Air in the oleo holds the weight of the a/c on the ground Air Oleos present in both retractable and fixed gears

Fixed Gear Non retractable, usually bolted on to the structure Often uses fairings or wheel pants

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netCessna 152 Advantages: Lighter weight Less compex Least costly

Retractable Gear Designed to eliminate drag (the greatest advantage) Can be either fully or partially retractable Direction of retraction depends on airframe model Methods of retraction: hydraulic, electric, mechanical, pneumatic Critical area of aircraft maintenance for safety reasons

Hulls and Floats Can be single float, or multiple Definition may include floating hulls (ex. Lake aircraft) Floating hulls may only require wing tip floats Skis used for snow and ice (wood, metal, composites) Skis may use shock cord to assist angle of ski attack Skis are mounted on the same strut as tires

Landing Gear Components Exact definitions of some components will vary The Oleo strut is the widely used form of shock absorption on aircraft landing gear.

Trunnions Portion of the landing which attaches to the airframe Supported at the ends by bearings

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netLanding gear traditionally extends from the center

Struts Vertical member, contains the shock absorbing mechanism Top of the strut mounts onto the trunnion Strut forms the cylinder for the oleo (outer cylinder) Piston is the moving portion (aka piston rod, tube or inner cylinder) Oil is forced from the lower portion of the strut to the upper Oil flow is restricted or varied according to a metering pin Final weight of a/c rests on air in the top of the strut Snubbers are used to prevent a sudden dropping of gear on takeoff Metering pin controls the flow of fluid between the chambers. The shock of landing is absorbed by the fluid being forced through a metered orifice. The metering pin gradually reduces the size of the orifice as the shock strut extends, which avoids a rapid extension after the initial shock of landing and related bounce. Chevron seals are used in shock struts to prevent the oil from escaping On nose wheel struts, a cam is built into the strut for the purpose of straightening the nose wheel before retraction. Filling a shock strut: exercise the strut in order to seat the seals, and remove air bubbles from the fluid. Most shock strut oil levels are checked by releasing the air, bottoming the strut, and checking to see if the oil is at the level of the filler plug. Information about shock struts: see: Manufacturers maintenance manual Information decal located on the strut Mfrs overhaul manual

Torque Links Also called scissors assembly Two A-frame members Connects and aligns upper and lower cylinders

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netConnects the strut cylinder to the piston Restricts extension of piston during retraction Correctly aligns axle to the strut

Trucks Located at the bottom of the strut piston Axles are mounted on the truck Trucks can tilt fore or aft to allow for a/c attitude changes

Drag Links Stabilizes landing gear longitudiannly May be hinged to allow retraction Also called a drag strut

Side Brace Links Stabilize gear laterally May be hinged to allow retraction Can be called a side strut

Overcenter Links (aka downlock mechanism) Use to apply pressure to the center pivot joint in a drag or side brace link Overcenter link is hydraulically retracted to allow gear retraction Also called a downlock, and/or a jury strut

Swivel Glands Flexible joint with internal passages Route hydraulic fluid to the wheel brakes Used where space limitation eliminate flex hoses

Shimmy Dampers

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netHydraulic snubbing unit Reduces tendency of nose wheels to oscillate

Piston type dampers Piston and rod filled with hydraulic fluid Piston has an orifice restricting speed of travel Slow movement has no restriction Large shimmy dampers incorporate temperature compensation

Vane type dampers Employ stationary vanes and rotating vanes Small passages restrict fluid movement Central shaft rotation is restricted from moving quickly

Damper Inspections Check for leakage & effectiveness of operation Check mounting bolts and hardware Most dampers are fairly reliable

Steering Systems Some a/c have free castering nose wheels; most have steerable.

Mechanical Steering Systems Uses foot power to steer the aircraft no assistance Some types will disengage when the gear is retracted Some types have an automatic centering device when weight is off the a/c

Tail Wheel Conventional gear use the tail wheel to steer May be a castering type with no steering capabilities (rudder steers)

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netMay be lockable, for parking purposes

Power Steering Systems Used where large amounts of force are required to steer Controlled by pilots rudder pedals, OR By a steering wheel, OR By a combination of both Most will require a towing bypass valve which allows Ground crews to to the a/c without damaging the system

Retraction Systems Purpose: reduce drag, or adapt a/c for landing on different surfaces (consider retractable wheels on float systems)

Mechanical Systems Crank mechanism, or uses a lever pulled by the pilot This method may use a mechanical latch system to lock wheels up No emergency backup available for this system

Electrical Retraction Systems Uses a central motor and push-pull rods Uses microswitches to detect when gear is down/locked, or up/locked

Hydraulic Retraction Systems Most common system of retraction for most sizes of a/c Used exclusively where landing gear is too large to be retracted by other methods May use ED pumps, electric pumps, hand or wind-driven pumps

Emergency Landing Gear Systems 4 possible methods of dropping gear when hydraulics are lost:

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netair bottle blows the gear down hand crank or ratched separate hydraulic system (may be hand pump) mechanical system which releases UP locks, and gear free-falls

Landing Gear Operation 4 main components: shock strut the wheel the brake assembly the trunnion and side/drag brace scissors (torque links) actuating cylinder down & up locks the bungee system

Using hydraulics, landing gear retraction requires greater energy than lowering Gear rotates on the trunnion pin Extending landing gear requires a release of the UP lock first, then The gear can begin free falling, slowed by the snubber in the orifice check valve Final few degrees of travel may require hydraulic pressure assistance Bungee system is used for emergency operation:

Gear doors must be operated before extension & after retraction

Landing Gear Position Indicator Systems Positive indication must be provided to the pilot that gear is down & locked Safety system includes squat switches and other microswitches Squat switches tell pilot when weight of a/c is on the wheels

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netSquate switches are electrically open when on the ground Some a/c use warning horns: they sound when: If gear is retracted, and throttle retarded to below cruise Landing gear position indicators: show position of Landing gear May use a system of different color indicator lights

Transport Aircraft Landing Gear Systems

Corporate Jets and Dual-Wheeled Transports Most have retractable tricycle-type gear, 2 wheels on each Nose gear will probably be a dual-wheel steerable type Gear will become completely enclosed when retracted

Helicopter Landing Gear Basic skid gear is common for small & mediums Wheel gear is used on sikorsky aircraft Retractable or cushioning gear may impart ground resonance Skid tubes are replaceable, and repairable Bending and deforming limits are established, and occasionally liberal Skid protectors are available, as are bear paws snow shoes Ground handling wheels are bolt-on towing additions

Inspection and Maintenance of Landing Gear The following must be carefully inspected: Attachments to fuselage or wings Struts Wheels

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netBrakes Actuating mechanisms for gear Hydraulic systems Gear doors

Fixed Gear Inspection Inspect for wear, deterioration, corrosion, alignment Jack up the aircraft to relieve the weight on the gear Shock cord should be inspected for age & fraying (5 years, retire) Shock Cord MIL-C-5651A. See diagram for year and quarter. Check oleos for bottoming: air charge has been lost.

Retractable Landing Gear Inspection Similar to fixed gear inspection, but add inspections for: Wear or looseness in joints or trunnions Leakage of fluids Smoothness of operation Operational check performed by jacking the airplane & operating gear Check for clearance of new tires in the wheel wells Check for operation of gear doors Check operation and adjustment of microswitches

If a oleo bottoms upon initial landing, but operates normally during taxiing, it is likely an indication of low fluid. Check your fluid levels.

Alignment of Main Gear Wheels Check for Camber and Toe-in. Camber is the tilt of the top of the wheel inboard or outboard Toe is the angling of the forward edge of the tire

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netOleo type gear often use angled shims or washers A common Toe setting is 0, with a tolerance of Some a/c may require alignment to be set while weight is on the gear. Use grease plate for this

Inspection of Floats and Skis Consider pop out floats and fixed floats (helicopters) Standard float assemblies for small a/c are sensitive to salt water Check for corrosion thoroughly Use standard sheet metal repair techniques Check for leaks See powerpoint slides for float parts familiarization diagram

Tires and Wheels

Aircraft Tire Operation Characteristics Tires for aircraft must endure higher loads and higher speeds than automobiles and trucks; the safety issue is much higher as well. Heat generation is higher in aircraft tires Rubber, the major material used, dissipates heat slowly Underinflating or overinflating increases shear forces in between the plies: tension will be higher in outer plies than in inner.

Type I tires: smooth contour Type II tires: high pressure III: low pressure IV: extra low pressure

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netV: not applicable VI: low profile VII: tires are constructed for extra high pressure; jet aircraft. VIII: extra high pressure, low profile, low speed or high speed.

Types I, II, IV and VI are being phsed out.

Aircraft Tire Nomenclature Tire ply rating refers to the maximum static load and its inflation pressures Tire markings: manufacturer, country of mfr, design type, load rating, tube or tubeless, tire size, part number, ply rading Number of recaps used to be stamped on the sidewall, but not all models have provision for this. Chafers are used to protect the wheel rim-to-tire bead chafing. The most important part of an aircraft tire is the bead. A tire with smooth tread is used for very light aircraft, grass runways, and locations where braking is only used as an aid to taxiing. Ribbed tread tires are used for directional stability, good tread wear, and to allow water to escape from between the tire tread and runway. A Chine sided tire is used to deflect water or slush away from the intake of the jet engines. Double or single chine wheels exist. Inboard halves of an aircraft wheel are different from the outboard by the provisions made for mounting & securing the disk brake assembly, and the presence of fusible plugs. The fusible plug is used to prevent tire blow-out due to heat build-up. The plug has a low melting point core which melts under high temperatures which may build up during heavy braking.

Tire Structure Steel wire beads form the inner diameter Plies are diagonal layers of rubber coated nylon cord fabric Chafers protect the tire during mounting/demounting. They also provide a good seal between tire and wheel.

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netBreakers are used to increase structural strength Inner liner acts as a built-in tube; prevents air from seeping through the casing plies. Beads anchor the plies and provide mounting surfaces for the wheel Tread is the surface of the tire for runway contact Most treads have groove patterns with 3 6 ribs, depending on size and type of service The light point on a tire is indicated by a red dot on the tire.

Tire Storage Tires should be stored vertical, in racks, in cool dry places. Ensure there are no sources of light or electrical appliances (for the ozone) nearby. Same with chemical fumes.

Tubes Made of rubber sections vulcanized together. Air valve is vulcanized to the tube for inflation/deflation Tubes can be checked for leaks by immersing in a water trough with a light inflation pressure applied.

Aircraft Wheel Construction Aircraft tires are too stiff to stretch over wheel rims. Damage will occur to the bead of the tire Split rims are used, and the two halves are sealed with an O-ring Most wheels are constructed of forged aluminum or magnesium alloys Wheels rotate on two tapered roller bearings; the cups are shrink fitted into the hub. Wheels are constructed with three fusible plugs, equally spaced around the wheel. The bead seat area is strenthened by rolling: it pre-stresses the surface Nose wheels are smaller in diameter and width than mains: rarely have brakes

Demounting and Mounting Tires Safety procedures: Deflate the tire beforee loosening the axle nut. This must occur in case the rim is cracked or the wheel bolts fail.

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netBefore we loosen the wheel half retaining bolts, we must deflate the tire, and remove the valve stem. Break the tire beads away using a bead breaker do not use sharp tools Then dismantle the wheel halves & inspect the bolts Always use a safety cage when inflating a tire. Bearings are generally a tapered roller bearing in hubs. Grease seals are used to prevent foreign material from entering and contaminating the wheel bearing grease. Stuck wheel bearing? Dont beat it to death with a hammer & punch ~ use a bearing puller. The only place to obtain proper inflation pressures is in the A/C M/M. That manual will quote pressures for the aircraft when loaded. (all-up weight) Installing tubes requires a dusting of talc into the tire for lubrication purposes. Tube should be placed so that the yellow strip (the heavy spot) is adjacent to the red dot (the light spot) on the tire. If using a tubeless tire; inspect the new tire to make sure it is a tubeless type. Install bolts and nuts ensuring they are installed in the correct direction. Use an alternating sequence to tighten. Only partially inflate the first time to allow the tire bead to seat to the wheel. A strap around the surface of the tread may be used to prevent the tire from expanding radially. Nitrogen is preferred, but not always necessary. Tires should be allowed to set for 12 to 24 hours before being installed. This allows for growth and natural stretch, and the air pressure to settle. Do not use soap/water installation liquids; may cause slippage of tire on the rim during landing.

Tire and Wheel Inspection Inspect outer tread while mounted on the a/c. Certain types of landing gear wear the tread unevenly (spring gear) Check for over or under-inflation, damage to sidewalls, cracks, weather checking, flat spots, chafing, thinning, valve stem movement (indicator slip marks) Dye Penetrant is not always the best answer: in some cases a crack may not show up because of the extreme pressures imposed by inflation and a/c weight. When the tire is deflated & inspected, some cracks will close up, and not show with Dye Penetrant. The most corrosion prone area of a wheel is any area which is exposed to the direct entry of moisture. This includes split lines, cavities, milled areas.

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netAny fuse plugs showing deformation must be replaced. All of em. The most critical areas on the wheel bolts is where the shank joins the head, or where the shank joins the threads. Pressures of a tire/wheel that is NOT installed on the a/c should read 4% below the recommended pressure. Any single burned patches on a tire tread would likely indicate hydroplaning. Wheel Installation

If the Mfrs wheel balance weights have to be removed for any reason, you must mark their position, and replace the same weight in the same place.

Aircraft Brake Assemblies

Light a/c can use simple shoe brakes or single discs; low weight & speed

Internal Expanding Shoe Brakes Older a/c and home-builts One-way (single servo type), or Two way (dual servo) Can be similar to automotive types

Expander Tube Brakes Four parts: brake frame, expander tube, return springs, and brake blocks Older aircraft Hydraulically operated Each brake block is independent; no tendency to grap

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netSingle Disk Brakes One of the most popular types Disk held in the wheel by teeth or keys Linings on either side of the disk; compressions forms braking action One lining is attached to axle structure, the other moves according to hydraulic pressure May have multiple pistons (& therefore multiple linings) Cleveland is one type of popular manufacturer Removal of air requires a brake bleeder valve

Multiple Disk Brakes Used where a substantial amounf of braking force is required Typically will have multiple rotors and pistons, stator plates, a pressure plate and a torque tube (see page 9-22 in Jeppesen) Wear indicators are often included in this design

Segmented Rotor Disk Brakes Heavy duty brakes design for use with high pressure systems using power brake control valves, or power boost master cylinders Uses stationary high-friction linings with rotating rotor segments

Carbon Composite Brakes Weigh 40% less than conventional steel segmented rotor brakes. Natural gas is used in forming the brake discs to add carbon Strength does not decrease at elevated temps Carbon against carbon performs excellent as a friction material Carbon brakes can exceed 3000 degrees F

Braking Heat Energy Huge amounts of heat energy on braking Pilots figure out gross weight of aircraft to establish a ground cooling time for brakes

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netSomewhat reduced by using thrust reversers

Troubleshooting Pilot reports excessive brake pedal travel. Check the brake fluid level. Which way should the chevron seals face? The inside of the chevron should face the pressure. An aircraft is reported as having excessive brake travel, but the brakes are still hard and effective. The probable cause is worn brake linings.

Aircraft Brake Systems Modern aircraft brakes are classified as single or multiple disk Mechanically operated, or hydraulically operated, or pneumatically operated Mechanical is the older smaller systems, using pulleys, cables, bell cranks. Many a/c use hydraulic system pressures to actuate their brakes. Some have an entirely independant system. Pneumatic brake systems use air only; some hydraulics use air as a backup pressure supply.

Independent Brake Systems Basic systems require a reservoir, a master cylinder actuated by pedal or handle, a brake assembly at the wheel, and all related hosing/tubing. Master cylinder is the energizing unit, usually one for each main gear wheel. Parking brakes are often a simple ratchet affair for holding the pedal or handle in place, which continues to supply pressure to the brakes. Various models of master cylinders; some mount on top of the rudder pedals. Function remains the same. Heel operated brakes or hand-brakes. Parking brake mechanism may be interrelated with the main brakes, but setting of parking brakes when hot may be an issue.

Power Boost Systems Power boost systems are used on a/c with high landing speeds. Power boost is halfway between manual brakes and power brakes. Power boost uses hydraulic pressure from the main system to the brakes via a check

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netvalve. May use a shuttle valve to route emergency air pressure. Larger aircraft require more braking power than can be applied through a master cylinder. Extra pressure can be exerted on the brake system by allowing hydraulic system pressures to act through a spool valve. A Brake Debooster serves the purpose of decreasing system pressure to a useable level in the brake system. It also has the effect of increasing the volume of hydraulic fluid flowing.

Power Brake Systems Used where manual and boosted brakes are not adequate. Uses a power brake control valve to direct hydraulic system pressure to the brakes. Power brake control valve is also called a brake metering valve; generally one for each main landing gear brake. Typical system has four lines to each valve; pressure, return, brakes, and automatic braking. Automatic braking is used to stop wheel rotation during retraction on take-off. Sources pressure from the landing gear UP position in hydraulic system.

Debooster Valves Used to reduce the system hydraulic pressure to a lesser pressure in the braking system. Generally exchanges High Pressure/Low Volume into Low Pressure/High Volume.

Multiple Power Brake-Actuating Systems Brake actuation systems get very complex at this level. Requires a lot of research and careful work on the AMEs part to learn these individual systems Brakes are operated by 2 independent systems. (#1, and #2) Each systems consists of daul-brake-control valves, pressure accumulators, brake-pressure transmitters and indicators, brake quantity-limiter valves, a skid-control manifold for each gear, and a parking-brake valve. All contribute the actuation of the independent cylinders in the eight main wheel brakes. Either system is capable of stopping the airplane on a maximum gross-weight landing.

Construction of Brakes Sintered brake linings are another term for metallic linings. Segmented rotor discs produce three benefits: Eliminate heat buildup in the disc

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netProduce more efficient braking Allow for longer braking action. Floating calipers are used to adjust for brake lining wear. Those types of aircraft which use a large amount of fluid to operate the brakes will incorporate a power brake control valve. Carbon disk brake lining material is usedfor light weight, better wear resistance, and better heat resistance. Automatic adjusters are installed in modern systems to maintain a set clearance between the disc and brake lining. Heavy steel plates called Pressure Plates are used to act as a backing against which the linings are forced by the pistons.

Brake Temperature Certain a/c have brake temperature readouts in the cockpit Temp ranges are relative to a scale of 0 to 9 Brake temperatures can increase even after brakes have been applied and released due to heat soaking Temp values above a 5 illuminates a BRAKE TEMP light

Brake Maintenance Some types of bonded linings are not fully cured at the time they are installed. The curing process requires they be installed and then used in a moderate-to-heavy application of the brakes. BCIT students will learn more about curing processes in the a/c composites section of level 3. For routine maintenance, check indicator pins for brake pad wear. Check lugs or keys holding rotor disks Check fusible plugs in the wheels for yeilding or cracks Examine fittings for leakage Ensure you are servicing the brakes with the appropriate fluids. Inspect hoses fro swelling, leakage, sponginess Check for reports of dragging brakes, fading brakes, excessive pedal travel, pedal creep or non responsive braking. Dragging brakes? Check for air in the system, sticking valves, and weak or worn return

( Word to PDF Converter - Unregistered ) http://www.Word-to-PDF-Converter.netsprings Grabbing brakes? Check for oil or FOD on linings. Fading brakes? Check for overheated linings and glazing Excessive travel? Check for lining wear limits, lack of system fluid, air in the system, or maladjusted brakes. Pedal creep? Inspect for leaks in a master or slave cylinder

Brake Bleeding Purpose is to remove any air from the braking fluids system and all related valve

Landing

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