5-1 Landing Gear

8/20/2019 5-1 Landing Gear

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AMS 5 - 1

Landing Gear



AMS 5 Part 1

AMS 5.1 Describe the constructional features,

explain the function and maintenance

procedures of landing gear components.



Landing Gear

Configurations

ric!cle landing gear



Landing Gear Configurations

Con"entional landing gear



Classification of Landing Gear

The landing gear of an aircraft serves a numberof very important functions.

It:

Supports the aircraft during ground operations,Dampens vibrations when the aircraft is being

taxied or towed, and

Cushions the landing impact.



Classification of Landing Gear

ften involves stresses far in excess of what

may be considered normal.The landing gear must be constructed and

maintained to provide the strength and

reliability to meet all probable landing

conditions.

The landing gear of an aircraft consists of

main and auxiliary units, either of which may

be fixed !non"retractable# or retractable.



The main landing gear provides the main support of

the aircraft on land or water.It may include a combination of: wheels, floats, s$is,

shoc$ absorbing e%uipment,‑

bra$es, retracting mechanism, controls,

warning devices, cowling, fairing and structural members needed for

attachment to the primary structure of the aircraft.

Main Landing Gear



The auxiliary landing gear

consists of:

Tail or nose landing wheel

installations, including steering

mechanisms&

s$ids& and

outboard pontoons, etc., with

the necessary cowling and

reinforcements.

Auxiliar! Landing Gear



'on"absorbing landing gear includes those types oflanding gear that do not dissipate the energy of the

aircraft contacting the ground during landing.

They only store the energy to return it to the aircraft

at a later time.

These types of gear include:

rigid landing gear,

shoc$ cord landing gear, and‑

spring type gear.‑

#on$Absorbing Landing Gear



%igid Landing Gear

Commonly found on helicopters and sailplanes.

(igidly mounted to the aircraft with no specific

component to cushion the ground contact other

than through the flexing of the landing gear or

airframe structure.



Spring !pe Landing Gear



Shoc$ absorbing landing gear dissipates the impact‑

energy of landing by forcing a fluid through a

restriction.

)ost of these types of landing gear do this

The movement of this fluid generates heat, and theheat is radiated into the surrounding atmosphere,

dissipating the landing energy.

There are two types of shoc$ absorbing landing‑

gear commonly used, these are the:

spring oleo and‑

air"oleo types

Shoc& Absorbing Landing Gear ‑



Spring 'leo Struts Consist of a piston type structure and a heavy,

coiled spring.

The piston and cylinder arrangement provides an

oil chamber and an orifice through which oil is

forced during landing.

*hen the aircraft is airborne,the strut is extended,

and the oil flows by gravity to the lower chamber.

*hen the plane lands, the piston with the orificeis forced downward into the cylinder and the oil is

forced through the orifice into the upper chamber.

This action provides a cushioning effect to absorb

the primary shoc$ of landing.

+s the strut collapses, the coil spring iscompressed, thus providing additional cushioning.

The spring supports the aircraft weight on the

ground and during taxiing.

The oleo strut absorbs the shoc$ of landing.



'il and Air 'leo Struts he c!linder is di"ided into t(o

compartments b! a piston tube

he piston fits into the c!linder around the

tube.

A tapered metering pin stic&s through the

hole in the bottom of the piston tube.

o fill the strut, the piston is pushed all of

the (a! into the c!linder, (hich is filled

(ith h!draulic fluid to the le"el of the

charging "al"e.

)ith the (eight of the aircraft on the

(heel, enough compressed air or nitrogen

is pumped through the charging "al"e to

raise the aircraft until the piston stic&s out

of the c!linder for a specified distance.



'il and Air 'leo Struts )hen the (eight is remo"ed from the landing

gear, the piston extends the full amount

allo(ed b! the torsion lin&s and the fluiddrains past the metering pin into the fluid

compartment in the piston.

)hen the (heels contact the ground on

landing, the piston is forced up into the

c!linder.

he metering pin restricts the flo( of fluid

into the c!linder, and much of the energ! of

the impact is absorbed b! forcing the fluid

through this restricted orifice.

he taper of the metering pin pro"ides a

graduated amount of opposition to the flo(

and smoothl! absorbs the shoc&.

he cushion of compressed air abo"e the oil

ta&es up taxi shoc&s.



leo pneumatic undercarriages should be examined‑

for& crac$s or damage to mounting structure,

corrosion, and

wear at pivot points.

In addition, the following maintenance is necessary: )achined surfaces of the strut inner cylinder should

be wiped free of dust or dirt at fre%uent intervals, to

prevent damage to the lower cylinder seals.

+ lint free cloth, soa$ed in the fluid used in the strut,‑

should be used for this purpose.

Maintenance



he extension of the inner c!linder, i.e. the

length of the "isible portion of the inner

c!linder,should be chec&ed fre*uentl! against the

centre of gra"it!+loading graphs pro"ided in

the appro"ed Maintenance Manual.

Note:

Because of the tightness of the sealing glands in

the strut, it may be necessary to rock the

aircraft to free the inner cylinder and obtainthe true extension

Maintenance



he strut should be inspected fre*uentl! for fluid

lea&s. f lea&s are due to fault! glands the glands ma! be

replaced,

f the! are due to a scored inner c!linder, the strut

should be changed. or*ue lin&s, steering arms, and damper

attachments should be chec&ed for securit!, and

for crac&s, (ear or an! other damage.

All mo"ing parts of the undercarriage should belubricated on assembl!, and at the inter"als

specified in the appro"ed Maintenance Schedule.

Maintenance



DC tail wheel assembly

The tail wheel is mounted on

a short spring, oleo, or other

assembly on the bottom of

the fuselage near the rudder.

The tail wheel may be fixed in

alignment with the fuselagelongitudinal axis, or it may be

designed to rotate, allowing

the aircraft to turn easily.

ail )heel



-ixed Alignment ail )heels

-ixed alignment tail (heels are found onl! onaircraft such as gliders, (hich are not normall!

taxied.

ail )heel

Mo"able ail )heelsA tail (heel that can rotate ma! be steerable,

full s(i"elling, and loc&able.

A steerable tail (heel responds to cabin ruddercontrols to aid in controlling aircraft direction of

mo"ement on the ground.



*essex helicopter - degree swivel tailwheel assembly.

ail )heel

A full$s(i"elling tail (heel is not controllable

and pi"ots freel! on its mounting.

Most (heeled helicopter (ith a tail (heel (ill

be a full s(i"elling t!pe arrangement.

Additionall! the! include

a loc&ing mechanism

that pre"ents

uncontrolled !a( during

rotor engagement.



-ixed Alignment ail )heels

/ Most steerable tail (heels incorporate afree$s(i"el capabilit! (hen the pilot

ma&es "er! tight turns using the main

(heel bra&es.

/ A loc&able mechanism is used (ithsome tail (heels to aid in directional

control during ta&eoff and landing.

/ Mechanism loc&s the tail (heel in

alignment (ith the aircraft longitudinalaxis.

/ )hen the loc& is disengaged, the tail

(heel returns to its full s(i"el or‑

steerable operation.

ail )heel



ails&ids

ll d -l t



ulls and -loats

f an aircraft is afl!ing boat, it has a

hull for flotation and

then ma! need onl!

(ing$tip floats.

Amphibious aircraft

ha"e floats or a hull

for operating on

(ater and

retractable (heels

for land operation.

Aircraft operated from (ater

ma! be pro"ided (ith either a

single float or a double float,depending upon the design and

construction/

ll d -l t



ulls and -loats

f an aircraft is afl!ing boat, it has a

hull for flotation and

then ma! need onl!

(ing$tip floats.

Amphibious aircraft

ha"e floats or a hull

for operating on

(ater and

retractable (heels

for land operation.

Aircraft operated from

(ater ma! be pro"ided

(ith either a single floator a double float,

depending upon the

design and construction/

S&i



S&is

S&i



S&isS$is are used for operating on snow and

ice.

The s$is may be made of wood, metal, orcomposite materials.

There are three basic styles of s$is.

Conventional s$i,

*heel s$i, and‑

(etractable wheel s$i.‑

S&i



Fwd

S&isA con"entional s&i,replaces the (heel on the axle.

he shoc& cord is used to hold the toe of the s&i up (hen

landing.

he safet! cable and chec& cable pre"ent the s&i frompi"oting through too great an angle during flight.

S&i



S&isA con"entional s&i,replaces the (heel on the axle.

he shoc& cord is used to hold the toe of the s&i up (hen

landing.

he safet! cable and chec& cable pre"ent the s&i frompi"oting through too great an angle during flight.

S&i



S&is

he s&i has a portion cut out that allo(s the

tire to extend slightl! belo( the s&i so that the

aircraft can be operated from con"entional

run(a!s (ith the (heels or from sno( or ice

surfaces using the s&i.

he (heel s&i is designed to mount on the aircraft along (ith the tire.‑

S&i



S&is

his arrangement has a small (heel mounted on the heel of the

s&i so that it does not drag on con"entional run(a!s.

S&i



S&is

%etractable (heel s&i arrangements ha"e the‑s&i mounted on a common axle (ith the (heel.

he s&i can be extended belo( the le"el of the

(heel for landing on sno( or ice.

he s&i can be retracted abo"e the bottom ofthe (heel for operations from con"entional

run(a!s.

A h!draulic s!stem is commonl! used for the

retraction s!stem operation.

nspection And %epair



Inspection of floats and s$is involves examinationfor damage due to&

corrosion,

collision with other ob0ects,

hard landings, and

other conditions that may lead to failure.


'f -loats And S&is

ubular StructuresTubular structures may be repaired using standard

welded repair procedures for tubular structures.




1loats and 2ulls

1loats should be carefully inspected for corrosion

damage at periodic intervals, especially if the aircraft

is flown from salt water.

If small blisters are noticed on the paint, either insideor outside the float, the paint should be removed and

the area examined.

If corrosion is found to exist, the area should be

cleaned thoroughly, and a coat of corrosion inhibiting‑

material applied.

If the corrosion penetrates the metal to an appreciable

depth, it is advisable that a patch be applied in

accordance with approved practice.


'f -loats And S&is




-loats and ulls

Special attention should be given to brace wire fittings and

water rudder control systems.

If the floats or hull has retractable landing gear, a retraction

chec$ should be performed along with the other

recommendations mentioned for retractable landing gearsystems.

Sheet metal floats should be repaired using approved

practices,

the seams between sections of sheet metal should bewaterproofed with suitable fabric and sealing compound.

+ float that has undergone repairs should be tested by filling it

with water and allowing it to stand for at least 34 hrs to see if

any lea$s develop.


'f -loats And S&is




S&is

S$is should be inspected for general condition of the s$i,

cables, bungees, and fuselage attachments.

If retractable s$is are used, chec$s in accordance with

the general practices for retractable gear should be

followed.

1or repair of s$is, the manufacturers furnish approved

repair instructions.


'f -loats And S&is

Main Landing Gear



Single +xle,

Dual +xle,

Single Tandem, and

Dual Tandem !Truc$ or 5ogie#.

Main Landing Gear

The ma0or design types:



railing Lin& Main Landing Gear



g g

The trailing lin$ design provides a softer

landing as the trailing arm is able to pivot up

around the forward landing gear strut. This

action provides more oleo travel than the

vertical oleo used with the Cessna Citation

II, shown on the previous page.

Photographs co rtes of



Left:

DC3 main landing gear.

Note large balloon tire for

rough strip operations and

foreword folding

arrangement.

Right: Fairy Gannet

main landing gear,

designed for airraftarrier operations.

Retrats outboard

into the wing.

Left: Light

heliopter main

landing gear.

!he upper strut is

an air"oil oleo

strut.

Photographs courtesy of

Sycamore - Australian

Fleet Air Arm Museum



Dual #$le

!he dual a$le type main landing gear

again may be fi$ed or retratable

%semi or full&.'t will tend to be used with medium

weight airraft, medium to larger

orporate (ets " airliners and larger

wheeled heliopters.

!he primary seletion is based on

weight and the desire to spread the

landing and ta$iing loads o)er a

greater area. 'n the ase of retratable

gears, a)ailable storage area when

retrated is also a onsideration.

Single 6 Dual Tandem 7anding 8ears



ruc& 0ogie2 Main Landing Gear 0oeing 3432

comprise a single

or dual tandem arrangement

Single 6 Dual Tandem 7anding 8ears

* + h i l D l i di tLanding Gear Components



* +ehanial Downlo indiator

- #ir al)e

3 /lumbing to wing

0 Retration #tuator

1 Conduit to wing %Ref&

2 /lumbing

#ft trunnion pin

4 /lumbing support braet

5 6trut eletrial pin

*7 #tuating ylinder pin

** 6ho strut

*- +anifold

*3 Clamp

*0 !ru eletrial 8 bo$

*1 9rae lin

*2 Co)er, weight and balane sensor

* plo snubber

*4 !ru attahmnet pin

*5 !ru positioner

-7 Lower tor;ue arm

-* 9rae

-- pper tor;ue arm

-3 6ide brae nut

-0 Downlo spring %- plaes&-1 Lower side brae

-2 pper (ury brae

- Lower (ury brae

-4 Lower side brae pin

-5 Forward trunnion pin

37 Lateral brae

3* pper side brae

3- pper side brae pin

Landing Gear Components

runnion



runnion

The portion of the landing"gear assembly that isattached to the airframe

Supported at its ends by bearing assemblies that

allow the gear to pivot during retraction and extension

The landing"gear strut extends down from the

approximate centre of the trunnion

Strut



Piston

The vertical member of the landing gear assembly

that contains the shoc$ absorbing mechanism.

The top of the strut is attached to or is an integral partof the trunnion.

The strut forms the cylinder for the air"oleo shoc$

absorber.

+lso called the outer cylinder.

Strut

iston



Piston

The moving portion of the

air oleo shoc$ absorber.‑

1its inside of the strut, and

The bottom of the piston is

attached to the axle or other

component on which the axleis mounted.

ther terms used for the

piston are

piston rod,piston tube, and

inner cylinder.

iston

or*ue Lin&s



+re the +"frame type membersused to connect the strut cylinder

to the piston and axle.

(estrict the extension of the

piston during gear retraction and

hold the wheels and axle in a

correctly aligned position in

relation to the strut.

The upper tor%ue lin$ is

connected to a clevis fitting on

the lower forward side of the

shoc$ strut.

or*ue Lin&s

Piston

iston



Piston

The lower tor%ue lin$ is

connected to a clevis fitting onthe axle.

The upper and lower tor%ue

lin$s are 0oined together by a

bolt and nut spaced with

washers. 9ach lin$ is fitted with flanged

bushings.

+ washer ta$es up the gap

between the flanged ends of

the bushings.n a number of aircraft, these

washers allow minor

ad0ustments to the wheel

alignment.

iston

ruc&



7ocated on the bottom of

the piston

2as the axles attached to

it.

sed when wheels are tobe placed in tandem !one

behind the other# or in a

dual tandem arrangement.

ruc&

Can tilt fore and aft at the piston connection to allow for

changes in aircraft attitude during ta$eoff and landing

and during taxiing.

+lso called a bogie.



Shimm! Dampers



/iston !ype

Dampener

ane !ype Dampener

Shimm! Dampers

2ydraulic snubbing unit,

reduces the tendencyof the nose and tail

wheel6s to oscillate

from side to side.

two general designs,: piston"type and vane"type.

5oth types may be modified to provide power steering

as well as shimmy damper action.

iston$!pe Dampers



iston !pe Dampers



6ane$!pe Designed with a set of moving vanes

d f i



6ane !pe

Dampers

and a set of stationary vanes.

The moving vanes are mounted on a

shaft that is turned, the chambers

between the vanes changed in si;e,

forcing hydraulic fluid from one to the

other.

The fluid must flow through restricting

orifices, providing a dampening effect to

any rapid movement of the vanes in thehousing.

The body or housing of the vane"type

damper is usually mounted on a

stationary part of the nose 6 tail landing

gear. The shaft lever is connected to the

turning part, usually the wheel rim.

+ny movement of the wheel alignment to

the right or left causes a movement of

the vanes in the shimmy damper.

Damper nspections



Damper nspections

Shimmy dampers do not re%uire extensive maintenance.

Chec$ for lea$age and effectiveness of operation.

If the damper has a fluid replenishment reservoir,

the fluid %uantity should be chec$ed periodically and

fluid of the specified type added if necessary.

*hen inspecting shimmy dampers, the mount bolts and fittings should be chec$ed

closely for any evidence of wear.

)any aircraft use bushings in the fittings so that the fit of

the bolts in the fittings can be renewed by replacing the

bolts and bushings.

If these mountings are allowed to become worn, the

damper will be loose on the nose 6 tail wheel, allowing

wheel assembly shimmying to occur .

# L di G



#ose Landing Gear

The tricycle landing gear is the most common arrangement

due to& improved vision for the pilot and

the reduction in gyroscopic effect from propeller fitted

aircraft over the tail draggers.

The nose wheel installation tends to be more complex thanthe tail wheel layout due to added re%uirements such as

a steering system.

The nose wheel assembly for most aircraft fall into two

categories: Single axle !fixed or retractable# and

Dual axle !normally retractable#.

Si l A l # L di G



Single Axle #ose Landing Gear

1ixed tricycle type landing gear system

with a steerable nose landing gear

Controlled by the rudder pedals.

1ixed or (etractable type

'ormally fitted to lightweight aircraft

%etractable #ose Landing Gear



The nose landing gear shares many of

the components associated with the

main landing gear& Trunnion&

+ir 6 oil oleo assembly !upper and

lower cylinders, piston#&

Tor%ue lin$s&

2ydraulic retraction 6 extension

actuator, also serving as the drag

brace.

The nose landing gear also has a

steering mechanism and shimmydamper assembly.

The axle is a for$ end type arrangement

providing support to the mounting of

the nose wheel on both sides.

%etractable #ose Landing Gear

Cessna Citation 'ose 7anding 8ear



g

+ssembly " Components





<. (od, steering

3. =am nut

. 5olt and nut assembly

4. Steering bellcran$

>. 5ushing, steering arm

-. 1or$?. 5olt, washer, nut, @ cotter

pin

A. Cap, air valve

B. 5ody, air valve

<. Safety wire

<<. Cap bolt @ washer

<3. (oller, aligner guide

<. 5olt, washer, nut @ cotter

pin

<4. 5rac$et, aligner

<>. Spring, inner

<-. +rm, steering

<?. Spring, outer

<A. 5olt, washer, nut @ cotter pin

<B. 7in$, upper

3. (od, piston

3<. 5olt, washer, nut, @ cotter pin33. 7in$, lower

3. *heel

34. Tire

3>. 2ousing, strut

3-. Shimmy dampener

3?. 5olt, washer, nut, @ cotter pin

3A. 5rac$et, shinny dampener

3B. 5olt, washer, nut @ cotter pin

. =am nut

<. (od end bearing

3. Drag lin$, lower

. 5olt, washer, nut @ cotter pin

4. 5olt, washer, nut @ cotter pin

>. Drag l in$, upper

-. 5olt @ nut assembly?. 5olt, washer, and nut

A. =am nut

B. Spring, downloc$

4. 2oo$, downloc$

4<. (od, actuator

43. Cylinder, hydraulic

4. +rm, spring

44. 9ngine mount

4>. +rm spring

Right: Nose landing gear

installation for the 9oeing *



installation for the 9oeing *.

!his assembly retrats forward.

Left: Dual a$le assembly for the Grumman

!raer.

!he gear retrats aft into a wheel beneath the

opit floor.

Note the long tra)el oleo, whih allowed the

airraft to ondut airraft arrier operations

assoiated with de hoo landings.



Documents

5-1 Landing Gear