PPL 3.1 Takeoff&Landing,Enroute Performance

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FLYBEST FLIGHT ACADEMY

PASSION DRIVES OUR PROFESSION


Private Pilot Ground

MODULE 2 / LESSON 5

MODULE 3 / LESSON 1Takeoff, Enroute & Landing Performance

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PASSION DRIVES OUR PROFESSION

MODULE 3 / LESSON 1
Takeoff, Enroute & Landing Performance

Objective: For the student to have a practical understanding of take off, landing, and enroute performance.

To Be Reviewed:

Factors affecting Takeoff Performance.

Factors affecting Landing performance.

Enroute Performance.

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Factors Affecting Takeoff Performance

1. Weight.2. Increased Takeoff Speed.3. Air Density.4. Head/Tail winds.5. Crosswinds.6. Runway surface/Slope.7. Flaps.8. Using the Takeoff Distance Graph/Table.

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NOTE:It is important to remember Performance data in the AFM/POH or other sources may be presented on the basis of standard atmospheric conditions, pressure altitude, or density altitude. The performance information in the AFM/POH has little or no value unless the user recognizes those variations and makes the necessary adjustments.

The effect of gross weight on takeoff distance is significant. It can be considered to have a threefold effect on Takeoff Performance:

Higher Liftoff Speed Becomes necessary.

Greater Mass to accelerate: Reducing acceleration.

Increasing ground friction and drag.

The minimum takeoff distance is of primary interest in the operation of any aircraft because it defines the runway requirements.

An excessive airspeed at takeoff may improve the initial rate of climb and feel of the aircraft, but will produce an undesirable increase in takeoff distance.

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WEIGHT:A greater speed is necessary to produce the greater lift necessary to get the aircraft airborne at the takeoff lift coefficient. A 10 percent increase in takeoff gross weight would cause: A 5 percent increase in takeoff velocity. At least a 9 percent decrease in rate of acceleration. At least a 21 percent increase in takeoff distance.For Example:With ISA conditions, increasing the takeoff weight of the average Cessna 182 from 2,400 pounds to 2,700 pounds (11 percent increase) results in an increased takeoff distance from 440 feet to 575 feet (23 percent increase).

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The overall effect of a 10% increase in weight may be to increase the takeoff distanceby 25%.

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Air Density

Engine performance reduces with thinner air. This occurs at airports with higher elevations, high surface temperatures and high humidity.

At higher density altitudes, the aircraft must accelerate to a higher TAS and ground speed to achieve the liftoff IAS, hence a longer takeoff run is needed.

The aircraft will take off at the same indicated airspeed (IAS) as at sea level, but because of the reduced air density, the TAS will be greater.

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Effects of Wind:

A normal takeoff is made as closely as possible into the wind because it gives: the shortest ground run; the lowest ground speed for the required takeoff airspeed; the best directional control, especially at the start of the ground run, when there isnot much airflow over the control surfaces; no side forces on the landing gear (as in a crosswind); the best obstacle clearance because of the shorter ground run and the steeper flightpath over ground; and the best position in the climb-out from which to make an up-wind landing straightahead (or slightly to one side) in the case of engine failure immediately after takeoff.

A tail wind of ten knots increases the landing distance by about 21 percent. An increase of landing speed by ten percent increases the landing distance by 20 percent

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Effects of wind on takeoff distances.

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Crosswinds

The airplane must not be taken off in a crosswind that exceeds the maximum crosswind

limit for the airplane.Directional control is a problem.The aerodynamic force from the rudder is potentially not sufficient to overcome the effect of the keel surfaces wanting to weathercock the airplane into the wind.Lateral control is an additional problem, because the crosswind will generally try to lift the into the upwind wing, which then has to be held down with aileron.

The approximate values of headwind and crosswind are: if the wind is 30 off the runway heading, then the crosswind component is . the wind strength; if the wind is 45 off the runway heading, then the crosswind component is the wind strength; if the wind is 60 off the runway heading, then the crosswind component is the wind strength; if the wind is 90 off the runway heading, then it is all crosswind.

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The most critical conditions of takeoff performance are the result of some combination of high gross weight, altitude, temperature, and unfavorable wind.In all cases, the pilot must make an accurate prediction of takeoff distance from the performance data of the AFM/POH, regardless of the runway available, and strive for a polished, professional takeoff procedure

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Runway Slope

Takeoff distance is calculated for a level runway, and some takeoff charts allow for theeffect of runway slope..Runway slope is calculated using the elevations at either end. Therefore a runway with down slope may have a hump (involving upslope) somewhere along its length.

A downslope of 2-in-100 or 2% down will allow the airplane to accelerate faster and so will decrease the ground roll.

An upslope of 2-in-100 or 2% up will make it more difficult for the airplane to accelerate and so the ground roll will be greater.

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Flaps

The use of small flap settings decreases the length of the ground run.

Flaps have the effect of lowering the stall speed, which reduces the liftoff speed.

While the ground run will be less when small flap settings are used, the takeoff distance to clear a 50-foot obstacle may not be reduced significantly.

This is because flaps, as well as increasing lift, increase drag, thus reducing the excess thrust and thereby the angle of climb..

A larger flap setting, even though it might reduce the stall speed,would greatly increase the aerodynamic drag during the ground run, causing a slower acceleration and then, once airborne, would significantly degrade the climb-performance.

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Using Takeoff Flaps Decreases Ground Roll

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Factors Affecting Landing Performance

Weight

Air density

Effect of wind

Runway surface/slope

Flaps

Fast approach speeds

Landing distance graph/table

Wake Turbulence

Ground Effect

Windshear

Taxiing

Note: The total landing distance is the distance established from a point where the airplane is 50 feet over the runway threshold (assumed to be a paved, level dry runway) to the point where the airplane reaches a full stop, assuming a steady, full flaps approach, with power off at 50 feet and maximum braking once the wheels are on the ground .This is the certification techniqueyou are not required to carry out all landings and stops exactly like this in practice.

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A heavier airplane will need a greater ground roll and total landing distance.

A heavier weight has a number of effects:

the stall speed is increased, so the approach speed must be greater.

The higher approach speed results in the airplane possessing greater kinetic energy which has to be absorbed by the brakes, increasing the length of the landing run. (There will, however, be a slight increase in the retarding friction force because of the extra weight on the wheels.)

The minimum landing distance will vary in direct proportion to the gross weight. For example, a ten percent increase in gross weight at landing would cause a:

Five percent increase in landing velocity. Ten percent increase in landing distance.

Weight

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Air Density

An increased density altitude results in a longer landing distance.

At high density altitudes the true airspeed will be greater than for lower density altitudes, and the touchdown groundspeed will be higher.

Therefore the amount of kinetic energy to be dissipated in the ground roll is greaterhence a longer ground run and total landing distance is required.

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The Effect of Wind

A headwind reduces the landing distance because the groundspeed is reduced by the headwind for the same true airspeed (V).

A tailwind means that the groundspeed will exceed the true airspeed, and so the touchdown speed relative to the ground is higher and a longer landing distance will be required.

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runway surface/slope

A downslope will result in a longer total landing distance. It will take longer for theairplane to touch down from 50 feet above the runway threshold, because the runwayis falling away beneath the airplane, and airplane braking while going downhill willnot be as effective as on a level or upward sloping runway.

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Flaps

Higher flap settings reduce the stall speed and therefore the approach speed, (which provides a 30% buffer over the stall speed), is lower.

High flap settings also give additional aerodynamic drag that helps to slow the airplane down, but only in the initial stages of the landing roll, after which they lose their effect.

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Fast Approach Speeds

Landing performance charts are based on specified approach speeds.

At a speed higher than that specified, the landing distance will exceed that predicted by the chart.

This is because of the greater kinetic energy of the airplane and the tendency of the airplane to float at the round-out because of ground effect.

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Wake Turbulence

As a wing produces lift, the higher static pressure area beneath the wing causes an airflow around the wingtip to the lower pressure area above.

The greater the difference in pressure, the greater the flow around the wingtips.

At the high angles of attack necessary to produce the required lift force at low speeds, very large and strong trailing vortices are formed.

To minimize the chances of flying through an aircrafts wake turbulence: Avoid flying through another aircrafts flightpath. Rotate prior to the point at which the preceding aircraft rotated, when taking off behind another aircraft. Avoid following another aircraft on a similar flightpath at an altitude within 1,000 feet. Approach the runway above a preceding aircrafts path when landing behind another aircraft, and touch down after the point at which the other aircraft wheels contacted the runway.

Pilots of small aircraft should avoid a hovering helicopter by at least three rotor disc diameters to avoid the effects of this down wash. In forward flight this energy is transformed into a pair of strong, high-speed trailing vortices similar to wing-tip vortices of larger fixed-wing aircraft. Helicopter vortices should be avoided because helicopter forward flight airspeeds are often very slow and can generate exceptionally strong wake turbulence.

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Wind is an important factor in avoiding wake turbulence because wingtip vortices drift with the wind at the speed of the wind.

If a pilot is unsure of the other aircrafts takeoff or landing point, approximately 3 minutes provides a margin of safety that allows wake turbulence dissipation.

Wingtip vortices tend to lose height slowly (typically at approximately 500 fpm), slowly move apart and drift downwind.

When taking off behind a large airplane which has itself just taken off, commence your takeoff at the end of the runway so that you will become airborne in an area well before where the heavy airplane rotated, or to where its vortices may have drifted with the wind.

If in doubt, delay your takeoff. Once airborne, maneuver to avoid the vortices in flight by turning away from where you think the wake turbulence is.

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Ground Effect

It results from a reduction in upwash, downwash, and wingtip vortices, and provides a corresponding decrease in induced drag.

The condition of slightly increased air pressure below an airplane wing or helicopter rotor system that increases the amount of lift produced.

Ground effect is greatest when the aircraft is just airborne and least when the aircraft is at an altitude above the ground approximately one wingspans distance.

If,during the landing phase of flight, the aircraft is brought into ground effect with a constant AOA, a floating effect may occur.

Because of the reduced drag and power-off deceleration in ground effect, any excess speed at the point of flare may incur a considerable float distance.

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CAUTION :

Due to the reduced drag in ground effect, the aircraft may seem capable of takeoff well below the recommended speed.

As the aircraft rises out of ground effect with a deficiency of speed, the greater induced drag may result in marginal initial climb performance. In extreme conditions, such as high gross weight, high density altitude, and high temperature, a deficiency of airspeed during takeoff may permit the aircraft to become airborne but be incapable of sustaining flight out of ground effect.

In this case, the aircraft may become airborne initially with a deficiency of speed, and then settle back to the runway.

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Windshear

Wind shear is a sudden, drastic change in wind speed and/or direction over a very small area.

While wind shear can occur at any altitude, low-level wind shear is especially hazardous due to the proximity of an aircraft to the ground.

Directional wind changes of 180 and speed changes of 50 knots or more are associated with low-level wind shear.

Low-level wind shear is commonly associated with passing frontal systems, thunderstorms, and temperature inversions with strong upper level winds (greater than 25 knots).

During a wind shear situation, the effects can be subtle or very dramatic depending on wind speed and direction of change

A tailwind that quickly changes to a headwind causes an increase in airspeed and performance.

Conversely, when a headwind changes to a tailwind, the airspeed rapidly decreases and there is a corresponding decrease in performance.

There are many causes of windshear. They include: obstructions and terrain features which disrupt the normal smooth wind flow; localized vertical air movements associated with thunderstorms, cumulonimbus and large cumulus clouds; low-level temperature inversions; and sea breezes

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One critical type of shear associated with convective precipitation is known as a microburst.

When encountered close to the ground, these excessive downdrafts and rapid changes in wind direction can produce a situation in which it is difficult to control the aircraft.

It is important to remember that wind shear can affect any flight and any pilot at any altitude.

While wind shear may be reported, it often remains undetected and is a silent danger to aviation.

Always be alert to the possibility of wind shear, especially when flying in and around thunderstorms and frontal systems.

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Taxiing :

Taxiing is the controlled movement of the airplane under its own power while on the ground.

An awareness of other aircraft that are taking off, landing, or taxiing, and consideration for the right-of-way of others is essential to safety.

When taxiing, the pilots eyes should be looking outside the airplane, to the sides, as well as the front.

Steering is accomplished with rudder pedals and brakes. To turn the airplane on the ground, the pilot should apply rudder in the desired direction of turn and use whatever power or brake that is necessary to control the taxi speed.

The rudder pedal should be held in the direction of the turn until just short of the point where the turn is to be stopped. Rudder pressure is then released or opposite pressure is applied as needed.

When first beginning to taxi, the brakes should be tested for proper operation as soon as the airplane is put in motion.

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Control Positions when taxiing with strong winds:

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Enroute performance:

Factors Affecting Cruise/Enroute Performance:

The incorrect selection of power settings, cruise speed, and cruise altitudes can significantly affect the efficiency and economics of operating your airplane.

Cruise altitude

To level off at cruise altitude leave climb power set until the airplane has accelerated to the desired cruise speed in level flight.

Power settingThe power is then reduced to cruise power, and the mixture is leaned as recommended in the Pilots Operating Handbook. The cruise speed maintained is determined by the power set.

Fuel consumption/requirements

first find the flight time by dividing the flight distance by the TAS. For example,

to cover 240 nautical miles (NM) at 90 KTAS will take = 2.67 hours; and find the fuel consumption by multiplying the flight time by the fuel flow. For example, if the fuel flow was 6.6 gph over 2.67 hours the fuel consumption would be 6.6 2.67 = 17.6 gallons.

Effects of wind

If there is a headwind, the air in which the airplane is flying will be moving backward over the ground and therefore in a given time the ground distance covered, measured in nautical air miles (NM), will decrease. Conversely a tailwind will increase the ground distance covered in a given time. However the distance flown through the air, measured in nautical miles (NM), will remain the same.

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Manufacturers present performance data in different ways, the most common being tables and graphs. The following examples are typical of the data for Piper and Cessna airplanes.

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Takeoff and landing are perhaps two of the most labor intensive tasks involved in piloting an airplane, and they start long before the wheels leave the ground.

Takeoffs involve much more than smooth piloting skills; they involve careful planning and preparation.

The takeoff performance of the airplane needs to be matched to the runway and the surrounding obstacles prior to actually taking off.

Your choice of cruise altitude depends on: distance to destination. terrain. airplane gross weight. weather (visibility and cloud base). wind at various altitudes, and ATC and airspace requirements.

This Module has introduced you to the various factors affecting the performance of the Aircraft,how to use the performance figures in the POH/AFM to predict the performance the aircraft is capable of doing.

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For more information read:

FAA-H-8083-2A Pilot Handbook of Aeronautical Knowledge Ch10.

FAA-H-8083-3B Airplane Flying Handbook Ch2, Ch5 & Ch8.

The Pilot's manual Ground School Ch9 & Ch10.

Cessna Aircraft, C172P PIM

Piper Aircraft Corporation, Pa28-161 PIM

PPL 3.1 Takeoff&Landing,Enroute Performance

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