(UNISIM(BEHAS) - Introduction to Aerospace)-EAS105 -Lab5

8/7/2019 (UNISIM(BEHAS) - Introduction to Aerospace)-EAS105 -Lab5

http://slidepdf.com/reader/full/unisimbehas-introduction-to-aerospace-eas105-lab5 1/13



2

Table of Contents

ABSTRACT .................................................................................................................. 3

INTRODUCTION.........................................................................................................4

OBJECTIVES................................................................................................................6

EXPIREMENT PROCEDURE.....................................................................................7

DISCUSSION OF RESULT..........................................................................................9

REFERENCE .............................................................................................................. 13

APPENDIX..................................................................................................................14



IntroductiontoAerospaceEngineeringLab5

3

Abstract

This lab work is concerned with the experimental studies of the aircraft landing gear

system and demonstrate the landing gear and flap operations using hand operated and

electrically driven hydraulic pumps.



4

Introduction

Landing Gear of aircraft of an aircraft serves a number of very important functions.

It supports the aircraft weight during ground operation, dampens vibration when

aircraft is being towed or taxied and cushions the landing impact. The landing gear

must be constructed and maintained in a manner that provides the strength and

reliability needed to meet all the probable landing conditions.

Most aircraft are equipped with landing gears either as Tricycle Landing gears and

Conventional-Geared Aircraft.

Figure1-BasictypesofLandingGearsArrangement

Landing gear design for aircraft vary from simple, fixed arrangement(non retractable)

to very complex retractable system involving hundreds of part.

Figure2-FixedLandingGear

Landing gears are the most importance

mechanical assembly on aircraft, usually includes wheels, brakes, shock absorbers,

such as oleo strut to take on the landing weight of the aircraft.

The retraction systems of the landing gear can consist of mechanical system, electrical

system and hydraulic system. For this experiment we would concentrate on the

retractable landing gear operated by hydraulic system.

Figure3-RetractableLanding

Gear




5

During the operation of aircraft with retractable landing gears, the system must raise

and lowers the gears without fail. Warning horn and position indicator in the form of

coloured light will inform the pilots whether the landing gears has been raised or not.

In the case of an emergency when the landing gears cannot be extended by normal

operation, either of the four methods must work

1) Air bottle to “blow” the gears down

2) Mechanical system where operation of a hand crank or ratchet perform the

extension operation.

3) Separate hydraulic system powered by other methods. (Example : Hand pump)

4) The use of mechanical system to release the up lock allowing the gear to free

fall into the down- and – lock position.

[Please note that the landing gears need to be down- and – lock position before

landing can take place]



6

Objectives

Todemonstratethelandinggearoperationsusinghandoperatedand

electricallydrivenhydraulicpumps.

Todemonstratetheflapoperationsusinghandoperatedandelectricallydriven

hydraulicpumps.




7

Experimental Procedure

Setupprocedure

1.MakesurethatACmaster,andcontrolpanelmasterswitchesareintheoff

positionbeforeconnectingtoACpowersource.

2.CheckthatGearandFlapselectorsaretheirneutralposition.

3.Checkhydraulicfluidlevel,brakemastercylinderlevel.

4.ConnecttrainertoACpowersource.Landinggearoperations

1.Movethelandinggearleverandflaplevertotheneutralposition.

2.Pushthethrottleleverforward.[i.e.awayfromyou]

3.Turncontrolpanelmasteron.(Thepushbuttonswitchontherighthandsideof

themasterswitchshouldalsobedepressed.)Agreenlightindicatingthatthegearis

downandlockedwillilluminate.[Ifgreenlightdoesnotcomeout,makesurethegearisdownandlocked.]

4.Cleartheareaofpersonnelandanyobjectthatwouldinterferewithmovementof

gearorlap.

5.Select‘gearup’byplacingthegearleverup.

6.Pullthehandleofthehandpumpout.Operatethehandletopumpthehydraulic

fluidtoretractthelandinggearmanually.

7.Whengearisfullyretracted,thered‘gearup’lightilluminate.

8.Totestgearwarninghornpullthrottleback,hornwillsound.[Tosilencehorn

movethrottleforwardforthisexperiment.]

9.Toextendgear,placegearleverinthedownposition.Gearwillfreefallpartially.

Ifthethrottleispullback,whathappen?10.Usethemanualhandpump,untilthegearisdownandlockedcompletely.‘Gear

downandlocked’light(green)willilluminate.[Whathappenstothewarninghorn?]

11.Pushbackthehandleofthehandpumpandmovelandinggearlevertothe

neutralposition.Also,pushthethrottleleverforward.

12.Turnonhydraulicpump.

13.Select‘gearup’byplacingthelandinggearleverup.Checkforsmoothoperation

andgearuplight(red)turningon.

14.Select‘geardown’byplacingthelandinggearleverdown.Gearshouldextend

and‘Geardownandlocked’light(green)willilluminate.

15.Turnmotorizedpumpoff.

Flapoperation1.Select‘flapdown’.Extendmanualpumphandleandmanuallypumpflaptothe

‘downposition’.

2.Select‘flapup’andusingthemanualpumpreturnflaptothe‘upposition’.

3.Turnonmotorizedpump.Raiseandlowerflapandcheckforsmoothoperation.

4.Turnmotorizedpumpoff.

Shutdownprocedures

1.Makesurelandinggearisdownandlocked.

2.Makesurethatflapisup.

3.TurnswitchesoffanddisconnectsACpowercord.



8

LEADINGPARTICULARS,HYDRAULICPOWERPAK

OperatingPressure.....................................................1150psi

MainReliefValveCrackingPressure………………………………………….1250-1300psi

ThermalReliefValvesCrackingPressure..............................2000-2050psi

HydraulicFluidRequired.............................................MIL-H-5606

ReservoirCapacity(full)…………………………………………………….4.5pints(approx.)

ReservoirCapadty(emergency)..........………............................0.95pint

DetentReleasePressure

LandingGear(RH)…………………………………………………………...1150psi

Flap…………………………………………………………………………1150psi

Weight(dry)…………………………………………………………………………….8.25lb




9

Discussion of Result

Reports:I.Observations

1.Comparethesizesoftheinletlinetothehydraulicpumpandthepressureline

fromthepump.Writedowntheadvantage(s)ofthistypeofarrangement.

Thesizeoftheinletlinetothehydraulicpumpislargerthanthepressurelinefrom

thepump.

Theadvantageoftheinletlinetobelargerbecauseitensuresthehighflowvolume

rateattheinletlinedoesnotgetjammed.Theadvantageofthepressurelinetobe

smallissothatitcanenableahigh-pressureflowattheoutlet.Usingthefomular

(Pressure=Force/Area)ifwedecreasethearea,werequirelesserforcetoachieve

thesameamountofpressure

2.Isthereservoirusedinthesystemanon-pressurizedorpressurizedtype?Justify

youranswerfromyourobservation.

The reservoir used in the system is a non-pressurized type as there’s an air vent tube

on the top of reservoir

3.Inthegearupposition,thelandinggearactuatorisinthe retractedposition.

4.Thelandinggearisequippedwithdown-lockmechanisms.

5.Thelandinggearisequippedwitha lowbrakepressuresystemusingthedisk

typebrake.

6.Thehydraulicsystemisopensystem.

7.Howisthehydraulicpumpunloadedinthesystem?

Thehydraulicpumpisunloadedinthesystemthroughtheselectorvalve.The

hydraulicpumpdrawsfluidfromthereservoirandpumpsitthroughthepressure

portofthehydraulicpowerpact,whichisthecontrolfboththesystems.

8.Whenusingthehandpump,doyouobserveanydifferenceinpumpingwhenthe

selectorvalveisinthe(i)neutralpositionand(ii)gearupposition?Giveareason

forthisdifference.

I. Inneutralpositionthepumpingofthehandpumpismucheasier

becausethereisnopressurebuildupandthehydraulicfluidis

allowedtopassfromthepressurechambertoneutralchamberand

backtothereservoir.(Camlobe8willopenthepoppetvalve3(see

diagramatQ4))

II. Ingearupposition,thepumpingofthehandpumpismuchharder

comparedtotheactionwheninneutralposition.Inupposition

poppetvalve1and4willopenandotherwillbeclosed.Thefluid

thereforeflowthroughpoppetvalve4andtotherodendofthe

actuatingcylinder.Thepistonwillretractandforcethefluidfromthe



10

cpendofthecylinderthroughpoppetvalve1andbacktothe

reservoir.

9.Whenusingthehandpump,afteroperatingthelandinggeartotheupposition

(steps5–7),theselectorvalveisthenshiftedtotheneutralposition.Thelanding

gearisobservedtocreep.Giveareasonforthisobservation.

The reason for the landing gear to creep downward is because when there is no

pumping action the hydraulic fluid is not pressurized and there is no up-lock

mechanism to lock secures the gear in up position.

10.Whenusingthehandpump,afteroperatingthelandinggeartotheupposition

(steps5–7),stoppumpingandwiththeselectorvalveremainingearupposition.

Thelandinggearisobservedto slidedownafterafewminutes.Giveareasonfor

thisobservation.

The design of this landing gear system has no up lock mechanism that will secure and

lock the landing gear strut when it is in the up position.

11.Thewarninghornisasafetyfeatureincludedinthelandinggear.

(i)Whenyouareonsteps8–10,whatdidyouobserve?

(ii)Whatconclusioncanyoumakefromtheobservations?

a) The warning horn will sound when the the throttle is pulled back(reduce

speed) when the landing gear is not lowered.

b) It is a saftey feature to prevent the pilot to land the aircraft (bellydown)when the landing gear is not fully extended and not in the down-

lock configuration.

12.Anindicatingsystemisusedtoprovideapositiveindicationonthepositionof

thelandinggearandoperationoflocks.Whatisthesystemprovidedinthistrainer?

Greenlightindicates landinggeardownandlocked

Redlightindicateslandinggearisup.




11

II.Writedowntheanswerstothefollowingquestions:

1.Writedownthetype,colourandnameofthehydraulicfluidusedinthesystem?

ThehydraulicfluidusedinthesystemisaMineralBaseFluid(MIL-H-5606).It

consistsofhigh–qualitypetroleumandusuallydyedredcolour.

2.Nametwoothertypesofhydraulicfluidsthatwecanuse?

VegetablebasedFluid(MIL-H-7644),usuallymixturescontainingcastoroiland

alcoholandcolouredblueorblue-greenoralmostclear.

Phosphateester-basefluid(MIL-H-8446).Itissyntheticfluidutilizedinmost

transportaircraftbecauseofit’sfireresistanceproperties.Thecontinual

modificationtotheformulationofPhosphatebasedfluidhasresultedinutilization

ofTypeI,II,III,IV.CurrentexampleoftypeIVareSkydrolLD-4andSydrol500B-4,

andarecolouredpurple.

3.Writedownthefullnameofthisselectorvalveusedinthesystem.

TheselectorvalveusedthissystemisthePoppettypefourwayvalve.

(SeediagramBelow)

4.Withreferencetothesectionalviewofthistypeofselectorvalve(given),explain

howitcontrolsthepositionsofthelandinggearactuatorwhen:

(a)Selectorvalveinthegearupposition.

(b)Selectorvalveinthegeardownposition.

(a)WhentheLandingGearselectorvalveismovedtotheupposition,poppetvalve

1andpoppetvalve4willopenandtheotherswillbeclosed.Fluidwilltherefore

flowthroughthepoppetvalve4andtotherodendoftheactuatingcylinder.The

pistonwillretractandforcingthefluidfromthecapendofthecylinderthrough

poppetvalve1andbacktothereservoir.

(b)WhentheLandingGearselectorvalveismovedtothedownposition,poppet

valve2andpoppetvalve5willopenandtheotherswillbeclosed.Fluidwill

thereforeflowthroughthepoppetvalve2andtothecapendoftheactuating

cylinder.Thepistonwillextendandforcingthefluidfromtherodendofthecylinder

throughpoppetvalve5andbacktothereservoir.



12

5.Nametwoothertypesofselectorvalveswhichmayuseintheaircrafthydraulic

system.

Selectorvalveareusedtodirecttheflowofhydraulicfluidtoorfromacomponent

andachievethedesiredoperation.

ThetwoothertypesareRotaryValveandSpoolorPistonSelectorValve.

III.FromtheInternetoranyotherappropriatesource,findoutwhatarethenew

Developmentsinaircraftbrakingtechnology.

(Newmaterialforbrake,newmethodofbrakeactuation)

The latest and most advance in brake material are the new Carbon Composite

Brakes. They weigh 40 % less and yet can function in even higher temperature with

more reliability than the conventional steel segment rotor brakes. Carbon composite

brakes have become a long-life, lightweight alternatives to steel brake since their

introduction to commercial aviation first used on the Concorde.

Carbon fibers are molded into a precise shape and the resulting disks are then bakedin special ovens, which introduce natural gas. The brakes material absorbs the carbon

given out by natural gas, making the brakes even denser with carbon. It can take up to5 months to produce each carbon disk.

When rubbed against itself, carbon composite can perform excellently as a friction

material. Carbon also offers reduced maintenance cost as they would last longer (1200-1500 landing) compared to the normal conventional steel brakes (about 1000

landings).They are 40 % lighter than conventional brakes. At the present time, it ismore expensive to produce the carbon composite disk brakes.

The latest in brake actuating technology is being implemented on the new Boeing 787

“Dreamliner”. It has decided to adopt the electrical system than the hydraulic system

(now most common) because it attempt to eliminate the potential delays associated

with leaking hydraulic fluid, leaking valve and other hydraulic failure. Brake

actuating technology using electrical system are much easier to monitor the brakes

and system status. Other advantage also include

Fault Detection and isolation.

Electrical monitoring of brake wear.

Ability to eliminate schedule visual brake wear inspection.




13

Reference

1. Micheael J. Kroes, Willism A. Watkins, Frank Delp. Aircraft Maintenance &

Repair. Sixth Edition. Macmillan/McGrraw-HillSchool Publishing Company,

1993.

2. “Undercarriage.” Wikipedia <http://en.wikipedia.org/wiki/Undercarriage>.

1st October 2008.

3. “Landing Gear” FIU Education

<http://www.allstar.fiu.edu/aero/flight14.htm.> 2nd October 2008.

4.

(UNISIM(BEHAS) - Introduction to Aerospace)-EAS105 -Lab5

Documents

Transcript of (UNISIM(BEHAS) - Introduction to Aerospace)-EAS105 -Lab5