landing gear operation

anyone here can teach me about the full sequence and operation of the landing gear when it take off to the air.

if could show me the picture or video would be more appreciated.

does the landing gear door lock after the landing gear retracted and how does it lock ?

Gear handle is placed up, hydraulic pressure from B sys is ported via the Landing Gear Control valve to the retract side of the MLG and NLG downlocks, MLG and NLG retract actuators, prebrake pressure is also applied to MLG brakes to stop rotation, once gear is fully retracted pressure is allowed via the L/G sequence valves to all 3 door actuators to close. Once all 3 doors are closed L/G goes into ISO relieving Hyd pressure from landing gear, main gears rests on uplock hooks and nose gear rests on the locking cams in the nose retract actuator and nose gear door. When gear handle is placed down pressure is applied to all 3 door actuators opening them. Pressure is also applied to extend side of NLG retract actuator and all 3 downlock actuators main gears freefall with wind pressure, presto 3 Green No Red. This is a pretty basic concept and pretty much the norm for all 3 fighters i have worked.

the pre brake pressure is given by the pilot when he put the landing to UP right ??

inside the downlock spring, there is a pipeline, what does this pipeline do ??

after the landing gears retracted, the wheel hub is facing downwards right ??

noobkupo wrote:the pre brake pressure is given by the pilot when he put the landing to UP right ??

inside the downlock spring, there is a pipeline, what does this pipeline do ??

after the landing gears retracted, the wheel hub is facing downwards right ??

1- Yes
2- Not sure what your talking about here, are you talking about internally?
3-No http://www.f-16.net/gallery_item46236.html
http://www.f-16.net/gallery_item105083.html

yeah internally, there is this pipeline in the drag brace.

then there is also 2 of these pipelines cover with blue cloth like, what does this 2 pipelines supply ??

thanks a lot for the answer, need to learn about the landing gear retract sequence and operation, is there any clip on how it retract ??

There are no internal lines in the dragbrace, the blue lines you are talking about are the hyd lines for the extend and retract pressure for the downlock actuator. I dont kow of any clips though im sure that there are some, somewhere. Read the 32GS it gives very detailed info on sequence and operation.

Why are you so interested in this?......All fighters are different.....and then again the same....

I may be wrong, but I think pre-brake pressure is automatic, not applied by the pilot. There is one item of main gear retract that is not obvious unless you watch carefully. (It's obvious to the ground grew swinging the gear, but not from th ground watching a takeoff.) That is the retract rate, or how fast the gear moves. There is a spec which says the gear and doors must be up and locked within seven seconds from raising the handle. To meet that spec, the main gear has to move so fast, it impacts the uplocks so hard it would soon suffer fatigue damage. So the gear moves at two rates, very fast over the first half of its travel upward, then much more slowly on up to the uplock. That way it can meet the spec, yet not damage the uplock.

What about the F-16 because I work on it and want to learn more about it.

johnwill wrote:I may be wrong, but I think pre-brake pressure is automatic, not applied by the pilot. .

Well yes your right pre brake is a result of the gear handle being placed up, not as a result of him specifically selecting it. It is indirectly selected by the pilot.

Then what thing causes the brake to automatically stop the wheel spinning? Is it at certain speed or what then the brake stop the wheel?

noobkupo wrote:then what thing causes the brake to automatically stop the wheel spinning ?? isit at certain speed or what then the brake stop the wheel ?

When the gear hadle is placed up along with all the other functions of the gear retraction, a reduced amount of Hyd pressure is applied via the brake control valve to one circuit on both the left and right brake to stop main mount rotation during retraction. That pressure stays there untill the gear is full retracted and the gear goes into ISO releving all Hyd pressure on the L/G. This all automatically happens when the pilot places the gear up, the nose gear has no such function and its rotation is stopped with the use of two bumpers in the NLG wheel well.

noobkupo wrote:what about f16?? cuz i work on it. want to learn more about it.

What air force are you with? Are you a student at Shepperd? I'm not trying to sound like a jerk. The landing gear sequence is something learning in tech school.

I might be able to dig out my old study guide from tech school(if i can still read it) I remember it having the Theory of Operation in it.

Theory of Operation.

Landing gear operation is controlled from either of the crew stations by the LG handle for normal operation and by the ALT Gear handle for emergency extension.

Main and Nose Landing Gear Normal Retraction.

Landing gear normal retraction is initiated by positioning the LG handle in up. This supplies 28V DC electrical power to the landing gear selector valve witch positions a valve to let hydraulic pressure to the following components:

-Spin down restrictor valve (actuates the brakes while the gear retracts)
-NLG Downlock actuator.
-NLG retract actuator.
-MLG downlock actuators.
-MLG retract actuators.

After the electrical sequence valves:

-NLG door actuator.
-MLG door actuators.

The nose and main gear retract seperatly:

Main landing gear.

The MLG downlock actuators unlock the MLG downlocks and allows the MLG retract actuators to retract the MLG. As the gear reaches the UP position, the uplock rollers on the shockstruts engages the uplock hooks. Because of this uplock switches is actuated and electrical sequence valves are actuated. These valves now lets the pressure flow to the retract side of the MLG door actuators which causes the doors to close. The uplock hooks are coupled to the MLG doors so closing the door results in that the gear is lock in it’s up and locked position. The door actuators are locked in their closed position by a internal lock in the door actuator.

Nose landing gear.

The NLG downlock actuator unlocks the NLG downlocks and alows the NLG retract/extend actuator to retract the NLG. As the NLG reaches it’s up position the uplock switch is actuated and operates the NLG door sequence valve. Now this valve is actuated pressure is supplied to the retract side of the NLG door actuator and the door closes. Both the retract/extend and the door actuator are internally locked in the closed postition.

Clear enough?

Landing gear up sequence:



for a larger view: http://img166.imageshack.us/img166/5599/vlb025cg7.jpg

noobkupo wrote:inside the downlock spring, there is a pipeline, what does this pipeline do

This should clear things up for you:


http://img292.imageshack.us/img292/7414/vlb018xn3.jpg