Jump to content
Aero Precision provides OEM part support for military aircraft operators across more than 20 aircraft
Sign in to follow this  
NATOPS1

Nose Landing Gear retraction

Recommended Posts

OK here is one for you...

Statement during FCF...

(Nose Landing Gear must take at least 3 seconds to retract.)

I remember something about the down switches not being the actual "position" of the strut but the position of the actuator...

Any ideas on this?

The flow regulator controls speed in both directions but the note only mentions retract.

My recollection (clouded as it may be) is the LG handle will route power to the up switch and show up instantaneously.

Share this post


Link to post
Share on other sites

I don't have schematics, but isn't the up switch in the uplock? Both mains and nose gear should "barberpole" in transit.

Share this post


Link to post
Share on other sites

The switch is located at the uplock.

They (should) show barberpoles when the gear is slected up and the gear is not in the selected position. (up)

Share this post


Link to post
Share on other sites

The (UP) switch is located at the uplock. (orginal post has been corrected)

They (should) show barberpoles when the gear is slected up and the gear is not in the selected position. (up)

Share this post


Link to post
Share on other sites

On the down switch; a pin protrudes out the back of the actuator piston. That pin has a visual color band of red and maybe white, which is a backup to a failed switch. The pin pushes the switch for the down indication. If the pin doesn't pop out all the way, you shouldn't be able to put in the downlock pit-pin for the nose gear. Good memory drill!

Share this post


Link to post
Share on other sites

On the down switch; a pin protrudes out the back of the actuator piston. That pin has a visual color band of red and maybe white, which is a backup to a failed switch. The pin pushes the switch for the down indication. If the pin doesn't pop out all the way, you shouldn't be able to put in the downlock pit-pin for the nose gear. Good memory drill!

NLG 'Down and Locked'

Share this post


Link to post
Share on other sites

Yes, Yes and Yes... The question is; Why is there a 3 second min retraction speed... The flow regulator is a two way so it should regulate the speed in both directions...

Share this post


Link to post
Share on other sites

Yes, Yes and Yes... The question is; Why is there a 3 second min retraction speed... The flow regulator is a two way so it should regulate the speed in both directions...

Maybe to limit the speed at which the NG hits the uplock? Seems that the MLG has a reduction in speed for the last few moments, 3/4"?

Share this post


Link to post
Share on other sites

Been a long time but seems to me the light in the gear handle should be on while the gear is in transit as well as B/P indication.Also 3 second for retraction is FAST.Phantoms had the fastest gear I've ever seen and it wasen't that fast.

Share this post


Link to post
Share on other sites

My guess is to give the mechanical linkage on the NLG time to close the doors without binding.

The time limit I believe is being misinterpreted. It is meant to say the time the gear takes to retract should be no longer then 3 seconds otherwise you may have a potentially bypassing actuator or a flow restriction in the hyd. lines. The main landing gear also has a time limit in the JG during retraction test. This is for a given pressure (3000PSI) and a given flow rate (16GPM I believe). This tests the efficiency of the actuator or the MLG HYD motors for bypassing, mechanical binding or a restriction in the hyd. system.

The Nose gear doors are all mechanically actuated by the NLG actuator thru the NLG strut at the fulcrum area. Front to rear door timing is set by shims between the forward and aft. actuating arms.

MLG retraction:

Power is applied to the up or down switches by the position of the MLG

control handle. All 6 MLG switches provide 2 ground paths, one for the MLG

indication and one for the red light in the handle. The up switches are

powered when the handle is place in the up position and the down switches

are powered when the handle is placed in the down position.

At any given time, only one ground is set. If the gear is selected up and

the MLG is currently in the down position, the up switch ground for the red

light is already closed and the up indication is open. The red light should

come on immediately and the position indicator has no ground and seeks a

neutral position (barber pole). When the gear is retracted the switch is

depressed, that opens the ground for the red light and closes the ground for

the MLG indicator and the indicator is powered and indicates up.

The operation is the same for down indications when the down switches are

selected by the MLG control handle. (indicator indicates wheels)

If the up indication indicates up immediately when the MLG control handle

place to the up position and the gear is currently down, this indicates a

problem with the up switch internally (most common) or a short circuit. The

same is true for down indication malfunctions.

All open grounds show up as a barber pole (most common, broken during acft.

Wash or recent MLG maintenance, stuck switch plunger, shorted switch).

Testing of the red light in the handle requires each gear position to be

tested one at a time, and from both the up position and the down position.

There are other warnings that tie into the MLG control system also ( warning

horn, flap and throttle position switches, squat switches) so be familiar

with the Job guide.

I also remember a TCTO or a instructions some years ago to paint the NLG mechanical down indicator fluorescent orange. It did not matter if the factory color was red or white, it was to be painted fluorescent orange.

I hope this helps.

Share this post


Link to post
Share on other sites

Ramrod, thanks for clearing up the time to retract should be ‘no longer than’ a fixed time.

Also GVS may be correct that 3 seconds is fast (not the correct limit). The attached YouTube video shows an example of C-130J NLG retraction and extension.

Share this post


Link to post
Share on other sites

Ramrod, thanks for clearing up the time to retract should be ‘no longer than’ a fixed time.

Also GVS may be correct that 3 seconds is fast (not the correct limit). The attached YouTube video shows an example of C-130J NLG retraction and extension.

I kind of think that the video was slowed down somewhat, Nevertheless 3 seconds is too fast for a 130 N/G.I'd like to hear from a pilot or F/E on this just to see if my memory is correct.

Speaking of N/G swings,how many of you guys pulled the duty of being in the N/W/W during a swing?Take one nose tire off and hope the gear didn't hang up on extension!

Share this post


Link to post
Share on other sites

Retraction times from down to full up taken from the Job guide. Same for J model.

NLG 13 to 19 seconds

MLG 15 to 19 seconds.

I do not have access to a H-6CF-1 to read the 3 second statement. Nothing in the J books say anything about 3 seconds that I could find.

Share this post


Link to post
Share on other sites

The "NLG must take at least 3 seconds to retract" changed to "No LESS than 3 SECs to retract" and has been in the NAVY AND USMC NATOPS all the way back to the 70's...

Share this post


Link to post
Share on other sites

As a flight engineer with sufficient flying hours, I never experience any figure close to the 3 seconds.

The shortest transition of all gears is normally around the 10 seconds.

The 3 seconds is mentioned in our flight manual only on the following case which is totally out of NATOPS question. The quoting note is from section 3 (emergency procedures) on the case of take-off continued after engine failure.

Quoting:

If obstacle clearance is critical, landing gear retraction should be initiated within 3 seconds after take-off and propeller feathering within 6 seconds after take-off ….etc.

So, the 3 seconds and the 6 seconds is an action required by flying crew to perform, and sure the 3 seconds is not the transition time for the gears.

Share this post


Link to post
Share on other sites

NATOPS1, We used our own version of the FCF in the USCG based upon the USAF TO. 3 seconds sure seems fast on the jack stands let alone in the air. It's been a good system review, though!

Share this post


Link to post
Share on other sites

I agree with tenten- this makes perfect sense. If after takeoff you lose power in one engine and have not reached obstacle clearance altitude and speeds, the crew action is to retract the gear with in 3 seconds and feather the prop within 6 seconds to reduce drag and attain better climb and acceleration performance. None of this is intended to state that the gear or NLG is to be fully retracted with in 3 seconds. Normal gear retraction time is 13 to 19 seconds, MLG 15 to 19 seconds.

Share this post


Link to post
Share on other sites

Has anyone experienced this defect;

After the take-off when gear lever is shifted up the nose gear position indicator keeps displaying down and lock indication, though actually(visually) the nose gear traveled to up and locked position.

NLG down and up switches electrical circuit been checked, no abnormality found.

NLG Down switch replaced, and adjusted with no effect.

When aircraft on jack we noticed that when gear is retracting the NLG actuator pin is not retarded back, which I believe it should go either fully "IN" or at least partially IN to release the down position switch.

The questions:

Mechanically: Is the malfunction of the internal locking mechanism within the actuator on the pin mechanism only or the down locking totally is at fault? (note: during ground the safety pin can be easily inserted)

Electrically: Why when the gear lever is selected up and the gear is up and locked does not give the indication of up?

Operationally: Is it safe to fly the aircraft to home station with this defect? If yes, is there any precaution during landing?

Appreciate any input to the subject.

Share this post


Link to post
Share on other sites

Has anyone experienced this defect;

After the take-off when gear lever is shifted up the nose gear position indicator keeps displaying down and lock indication, though actually(visually) the nose gear traveled to up and locked position.

NLG down and up switches electrical circuit been checked, no abnormality found.

NLG Down switch replaced, and adjusted with no effect.

When aircraft on jack we noticed that when gear is retracting the NLG actuator pin is not retarded back, which I believe it should go either fully "IN" or at least partially IN to release the down position switch.

The questions:

Mechanically: Is the malfunction of the internal locking mechanism within the actuator on the pin mechanism only or the down locking totally is at fault? (note: during ground the safety pin can be easily inserted)

Electrically: Why when the gear lever is selected up and the gear is up and locked does not give the indication of up?

Operationally: Is it safe to fly the aircraft to home station with this defect? If yes, is there any precaution during landing?

Appreciate any input to the subject.

When you position the MLG control handle to up, power is removed from the all the down switches and the applied to the up switches. Since the up switch ground contact is already closed, the red light in the handle should come on immediately. Power removed from the down switches now provides an open circuit to the indicator and the indicator should move to barber pole. Once the gear is fully retracted, then up switch is depressed opening the ground for the red light in the handle and the red light goes out and at the same time the up switch ground for the indicator is closed to complete the circuit and the indicator moves to up.

Your problem seems to be the indicator its self. It should go to barber pole when you turn off acft. power. A MLG control panel replacement should fix this problem. The NG indicator seems to be stuck or burned out.

Share this post


Link to post
Share on other sites

Ramrod; let me highlight some points noticed during ground check with aircraft on jack, it may help in finding the defective component;

1- During ground with electrical power turned off ALL landing gears position indicators are showing "barber pole" which is a normal condition.

2- With power ON and gears down all indicators showing down. (Also normal)

3- When LG control handle is selected UP and all gears start the transition; mean gears only will show "barber pole" during the transition but the nose will remain showing down indication

ALL the gears will retract normally to up the main gears will show up indications, while the nose will keep showing down indication.

With this condition (NLG up, control handle up) when removing/sliding back the down switch the nose gear then will show UP indication.

Therefore it seems that keeping the down switch under the depressing of the NLG actuator pin is the main cause of not seeing the barber pole" during transition nor seeing the UP indication when the NLG is at up and locked position.

And it seems that the up electrical contact of LG control lever has nothing to do with the position indicators if the down position switch contact is not at first released by the pin retraction.

Share this post


Link to post
Share on other sites

Ramrod; let me highlight some points noticed during ground check with aircraft on jack, it may help in finding the defective component;

1- During ground with electrical power turned off ALL landing gears position indicators are showing "barber pole" which is a normal condition.

2- With power ON and gears down all indicators showing down. (Also normal)

3- When LG control handle is selected UP and all gears start the transition; mean gears only will show "barber pole" during the transition but the nose will remain showing down indication

ALL the gears will retract normally to up the main gears will show up indications, while the nose will keep showing down indication.

With this condition (NLG up, control handle up) when removing/sliding back the down switch the nose gear then will show UP indication.

Therefore it seems that keeping the down switch under the depressing of the NLG actuator pin is the main cause of not seeing the barber pole" during transition nor seeing the UP indication when the NLG is at up and locked position.

And it seems that the up electrical contact of LG control lever has nothing to do with the position indicators if the down position switch contact is not at first released by the pin retraction.

If the down lock switch is properly adjusted as per the Job Guide, and the switch mount bracket has never been damaged or locally manufactured and replaced with a non LMCO part or suitable spare, then the only thing left is the actuator down lock internals. There is a emergency spring that also works with the HYDs in the down lock pin that could be defective in someway. I tried to look for a actuator overhaul book, but could not find one. By backing off the down lock switch and the indications operate correctly substantiates your theory of the down lock pin in the actuator having the problem. Only a actuator replacement will fix it unless you can overhaul it yourself.

I stand corrected on the power for the up and down lock switches. Power is applied directly from the buss to the indicators and red light and only needs a selected ground to complete the circuit to the light or the indicator. The MLG handle controls the MLG selector valve.

A 4.Adjust NLG down lock switch (2) as follows:

a. With NLG down and locked, position down lock

switch (2) to just contact indicating plunger (7)

then seat jamnuts (3, 5) against support assembly.

b. Backoff jamnut (3) two to two and one half

turns.

c. Push switch forward and tighten jamnut (5).

Safetywire jamnuts (3, 5) together.

32-24-

Share this post


Link to post
Share on other sites

Thanks Ramrod for your help and clarification, as for the down lock switch it is LMCO part, and as for switch adjustment we have tried all setting of adjustment, but none of them worked.

At present our intention as you state in your post is to replace the NLG actuator, but we are facing some difficulties on doing the task out of home base, we are trying to bring the aircraft under "Exceptional Release" and deal with it at home station.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Sign in to follow this  

×
×
  • Create New...