Difference in P-51B/C Landing Gear vs P-51D/K

[Chris]

No problem Visaliaaviation. I know many of the people on this site are really into details and such. Some folks think a gloss OD paint job detracts from the restoration because it's not "authentic" as an example. It's just easier to keep clean. Personally I take care of a D model and I didn't even notice the difference in cowling. I just think it looks really cool and I think it's up to the guy paying the bills to paint it in whatever scheme he wants it. I'm just glad it can fly. My glass is always half full and it's never swill. I know we're all fans of warbirds and there's no way to agree on everything and my "picky" comment was not intended to scorn anyone, I just think it's really neat when someone takes the time, effort and BIG bucks to try and do something as accurately as possible even though that is not always possible. Sorry if I offended.

[warbird1]

Just curious, I've always wondered why the inner gear door on the Mustang has the different piece of metal on it? Is it a structural thing or what?

Is it where the tire would rub on the way up? thats what I have always thought...............good question,

Can somebody confirm that this is the reason for the extra piece of metal on the inner gear door - for the rubbing of the tire?

[51fixer]

Just curious, I've always wondered why the inner gear door on the Mustang has the different piece of metal on it? Is it a structural thing or what?

Is it where the tire would rub on the way up? thats what I have always thought...............good question,

Can somebody confirm that this is the reason for the extra piece of metal on the inner gear door - for the rubbing of the tire?

Yes, that is what that is. It is a piece of stainless steel mounted to the alum inner skin. The tire rubs on extension, when the uplock hook is released the tire will drop onto the door as it opens. When retracting the inner doors will not close until both MLG struts are fully up as there is a valve that must be pushed on by both before the inner doors will close.
Rich

[warbird1]

Just curious, I've always wondered why the inner gear door on the Mustang has the different piece of metal on it? Is it a structural thing or what?

Is it where the tire would rub on the way up? thats what I have always thought...............good question,

Can somebody confirm that this is the reason for the extra piece of metal on the inner gear door - for the rubbing of the tire?

Yes, that is what that is. It is a piece of stainless steel mounted to the alum inner skin. The tire rubs on extension, when the uplock hook is released the tire will drop onto the door as it opens. When retracting the inner doors will not close until both MLG struts are fully up as there is a valve that must be pushed on by both before the inner doors will close.
Rich

Thanks for the confirmation, Rich. So, tell me about the MLG strut and the inner gear doors. Which are hydraulic powered, which are gravity when extending?

How about the tailwheel, same question?

[bdk]

Actually the hooks go opposite each other. 1 forward and 1 aft so a torque tube wouldn't work.

Thanks Rich. Didn't remember a torque tube on the D, but did remember about the Vise Grips! The B arrangement is more similar to the T-6, but still quite different.

[51fixer]

Just curious, I've always wondered why the inner gear door on the Mustang has the different piece of metal on it? Is it a structural thing or what?

Is it where the tire would rub on the way up? thats what I have always thought...............good question,

Can somebody confirm that this is the reason for the extra piece of metal on the inner gear door - for the rubbing of the tire?

Yes, that is what that is. It is a piece of stainless steel mounted to the alum inner skin. The tire rubs on extension, when the uplock hook is released the tire will drop onto the door as it opens. When retracting the inner doors will not close until both MLG struts are fully up as there is a valve that must be pushed on by both before the inner doors will close.
Rich

Thanks for the confirmation, Rich. So, tell me about the MLG strut and the inner gear doors. Which are hydraulic powered, which are gravity when extending?

How about the tailwheel, same question?

The landing gear has devices to lock the gear in the up and down positions. On the MLG the down lock is spring operated to latch down and hyd to release. The uplock is spring operated to latch up and mechanical to release. The movement of the gear leg and the inner door are by hyd actuators. To control how the gear is synchronized there are valves and plungers with cable and linkages. In essence the timing of the operation of the components is important. With the gear up in flight the MLG is locked up by a hook and the inner door is shut and also locked by 2 hooks. By selecting gear down the latches on the inner door release and the uplock hook is released. This is by mechanical linkage which also moves the gear selector valve to provide hyd pressure from the up system to the down system. Pressure is ported to the timing valve which directs the pressure to the inner doors to open them. The MLG will free fall at 1st pushing against the rub strip on the inner door as they fully open. When the inner door fully open pressure will build in the MLG actuators pushing the MLG to the down position. Also small hyd actuators will extend allowing the spring in the MLG downlock to push against the lock plunger. The plunger will be pushed in as the MLG trunion pushes past and the plunger spring will push the lock into place when the gear is fully extended. When both MLG are extended cables at the top of each will pull the timing valve the other way which will provide pressure to close the inner doors. Then you have gear down and inner doors closed.
To raise the gear the gear handle is placed in up. The linkage moves the selector valve to the up system and also the uplock hooks move from the released position to up position where the uplock rollers will push them out of the way but springs will pull them back to capture the gear when it is at the top of its retraction travel. Pressure then is ported thru the timing valve to the inner doors to open them. When open, pressure will build in the system pulling the MLG downlocks and then porting pressure to the MLG actuator up side which moves the gear. When each gear is up they will lock into the uplock and push on a plunger. Both plungers are tied into a linkage which again will pull the timing valve to close the inner doors. Gear up and inner doors closed.
The tail has mechanical up and down locks which are connected by cables to a bellcrank connected to the gear handle in the cockpit. There is a hyd actuator to move the tailgear up and down using the same hyd selector mentioned above to port pressure to the needed side. The tail gear moves pretty fast compared to the MLG. The tail gear doors open and close by a mechanical linkage which is connected to the tailwheel. As one moves the other follows.
Emergency gear extension utilizes a hyd bypass valve which is connected to a T handle in the cockpit. The linkage also connects to the uplocks on the inner gear doors. Pull the T handle and the inner door hooks are released and any hyd pressure is released and all hyd fluid will flow into the hyd tank. Then placing the gear selector down releases all uplocks on all 3 gears. Gravity will pull the gear down and a slight yawing and the side load of air will lock the gear down.
Kinda long and probably confusing.
Rich

[warbird1]

The landing gear has devices to lock the gear in the up and down.........

No, that was exactly what I was looking for! Thanks for the excellent explanation!

One more question regarding the gear. Why is it that the inner gear doors are retracted in flight, when the MLG is extended? You would think that they would just leave it extended to prevent wear and tear on the retraction system. NAA engineers weren't stupid, so there must be some reason for that.

[51fixer]

The landing gear has devices to lock the gear in the up and down.........

No, that was exactly what I was looking for! Thanks for the excellent explanation!

One more question regarding the gear. Why is it that the inner gear doors are retracted in flight, when the MLG is extended? You would think that they would just leave it extended to prevent wear and tear on the retraction system. NAA engineers weren't stupid, so there must be some reason for that.

They interrupt the flow of air into the scoop. The scoop houses the radiator and oil cooler. The coolant temp will rise when flown with the doors extended.
Rich

[Jim Beasley]

D parts hard to find? I know weve' been over this before but the upper cowl is off a D and lacks the characteristic hump of the B/C's. Also obvious is the lack of canted panel line in the A frame location.

Not knocking the "restoration" in anyway and I too would rather see it back in Shangri-La colors or how about an accurate "Bald Eagle" scheme?

I think what Rich means is that there are still a few -D parts on her but they're not outwardly visible.

I would LOVE to find the proper cowling -- with the access door too like this photo -- but even -D cowls are apparently made of unobtanium. If/when we redo her I'd like to keep the cowl with the Princess lettering so if anyone knows where we can get proper cowl Rich and I'd love to grab it. jb

[Glenn Wegman]

Jim,

Why not just make new stainless and incorporate the carb heat duct door? You would then have to make the correct cowl former, but it's fairly straight foreword too.

I work on two airplanes that have early top cowl panels on them with the small oil filler access door as in your pic. Both want me to modify them to late style doors to acces the dip stick.

You could also get an early tail cone to replace your late style one. They are not too uncommon either.

Glenn

[Bradburger]

Thanks for posting this Rich - very interesting!

There was quite a detailed write up in the Flying Legends Programme from a couple of years ago by former TFC engineer Joe Kennedy. He was reponsible for the 're-rebuild' of PE, and he told what was required to bring her back to P51B/C status. IIRC, this and the front lower firewall was one of the main areas were there was a lot of work required during the rebuild

I'll try and find it.

Cheers

Paul

[visaliaaviation]

The cowling , taller firewall and the hump of B/C are quite visible differences IF one one takes the time to compare. Once noticed in one clear P-51B or C photo, the hump will be seen nearly EVERY time in most others. Also the door on the side of the cowl (right behind the exhaust in PE photo above) was not typical of most B's. How about a "plant on" door to simulate?

BTW- complete p-51B fuselage loft (including cowl) is available , if your are interested.

[51fixer]

Kinda long and probably confusing.
Rich

To clarify some-

P-51C L/H wheel well.
L/H edge shows the Inner Door hyd actuator (chrome shaft) and the linkage rod to the door. About 1/2 way from right to left along bottom is a bulge with a silver arm. This is the landing gear selector valve and the linkage that connects it to the cross tube. Above that is the inner door timing valve. This controls when the inner doors open and close in relation to the MLG struts. The small black square on the lower R/H corner is a hyd pressure gauge which you read the accumulator pressure in the R/H well. To the right of the gauge the black hoses are from the main fuel cells. They feed into the fuel selector. The larger black hose going to the left from the selector feeds the fuel to the engine. In the middle of the photo is the MLG uplock. To the right is the plunger that the gear pushes on when retracted which will close the inner doors. On the R/H side of the photo is a light Green vertical channel. This is the wing attach fitting and it extends above to join the wing to the fuselage. At the bottom there is a cable which stops the inner door from traveling to far open. On the far right the small black box is a micro switch which is part of the gear warning lights displayed in the cockpit. The silver unit behind the switch is the inner door lock.
Rich

[airnutz]

Kinda long and probably confusing.
Rich

To clarify some-

The small black square on the lower R/H corner is a hyd pressure gauge which you read the accumulator pressure in the R/H well.
Rich

It looked like a gauge from the back side in port well..I almost asked the question..until your starboard well
photos answered my question. Very nice thread..great to have the owner and the wrench-burner
sharing the what's-n-why's answers..quite a team and family, Thanks for sharing!

[drgondog]

The reason for the change was on the early D models, several airplanes crashed because the clam shell opened slightly in flight because the gear leg was tapping on it. At high speed, it would open slightly, the slip stream would catch it, rip it open and the wind would catch the exposed gear and wrench it out of the wing, causing the wing to be ripped off.

Matt - are you sure it wasn't pure 'aero' cause, basically same at the ammo access door? How would they suspect or prove gear leg 'play' as the cause? Then, if true what did NAA do to prevent play in the gear leg?

IIRC all the aforementioned failures due to clam shell opening at very high speed - normally near compressibility. I know there was a dive test at RAE in which the test pilot observed the 'bulge'/deflection on the ammo access door in a .82-85. Ultimate dive test... but that was on the Mustang IV, after they beefed up the door from the B to D/K