P-51D maneuvrability - what it was in reality ...

[GrauGeist]

The CW-21 had more issues with it's landing gear than anything else.

This was something that plagued many Curtiss types, too.

 

[GregP]

The CW-21 had more issues with it's landing gear than anything else.

This was something that plagued many Curtiss types, too.

The only Curtiss airplane I have personal experience with is the P-40. It has a very robust landing gear rotating mechanism that almost cannot fail to work unless the gear itself fails to retract. I haven't heard of ANY P-40 landing gear issues in the last 18+ years of warbirds every weekend.

That's not to say SOMEONE hasn't had an issue. Undoubtedly, they have.

 

[SaparotRob]

But nothing on CW-21 tails falling off?

 

[GrauGeist]

But nothing on CW-21 tails falling off?

Nope.

Even the Reggiane Re.2000 never lost a tail.

 

[GregP]

There's one of these at the Evergreen Museum in MacMinville, OR. Makes you want to get in and go fly it.

 

[GrauGeist]

The only Curtiss airplane I have personal experience with is the P-40. It has a very robust landing gear rotating mechanism that almost cannot fail to work unless the gear itself fails to retract. I haven't heard of ANY P-40 landing gear issues in the last 18+ years of warbirds every weekend.

That's not to say SOMEONE hasn't had an issue. Undoubtedly, they have.

CAF's P-40 ad a gear failure about five years ago.

The BF2C had gear problems, so did the P-36 (which the P-40 inherited).

The XP-55 "ass ender" also suffered gear issues and even the C-46 experienced maingear failures.

 

[SaparotRob]

There's one of these at the Evergreen Museum in MacMinville, OR. Makes you want to get ina fly it.

View attachment 739243

Beautiful.

 

[Shortround6]

I believe the P-36/P-40 was to a Boeing patent.
Not sure if that was the gear mechanism or if it was the rotation of the wheel into the wheel well.

 

[GrauGeist]

To be fair to Curtiss, a great many aircraft manufacturers, Allied and Axis alike, had landing gear issues with their types at one point or another.

 

[GregP]

CAF's P-40 ad a gear failure about five years ago.

The BF2C had gear problems, so did the P-36 (which the P-40 inherited).

The XP-55 "ass ender" also suffered gear issues and even the C-46 experienced maingear failures.

The BF2C looks like it SHOULD have gear problems. That does not excuse actual gear issues, and I am not aware of the significant gear issues on it. That is, I KNOW it had gear issues, but I do not know what the issue was. Did it fail to lock up or down? Did it fail to retract or extend properly? I know it was manually-operated, but do not know the mechanics of the actual gear issue. Was it chain-and-sprocket, worm-and-roller, or what? They only made 164 production airplanes and 2 prototypes. So, I'd guess the issue made itself known decently early.

The XP-55 was a one-off type setup. Landing gear can be tricky to make positively lock up or down. Considering the XP-55, I'd say the gear was the least-important problem it had. Staying in controlled flight seems like the real weakness that needed work. They never did really figure it out. It flew OK when staying near straight and level flight, but it seems like it had issues when pushed into hard maneuvering and particularly when stalling and recovering from same.

The P-40 doesn't look to have gear problems that are systemic. An individual airplane might have an issue, but the system is decent. It well might have had a gear fail to retract or fail to extend, but it almost can't fail to rotate when retracting or extending. The main gear, tail wheel, and flaps are hydraulic, driven off an electrically-driven hydraulic pump with a manual, hand-operated backup.

It doesn't HAVE weaknesses. I suppose the hydraulic line COULD rupture, rendering it non-operative. But that would likely be the fault of whoever replaced the original lines with something not strong enough. It's only a 3,000 psi system, and it's about as foolproof as you can get. The valves COULD malfunction, but the ones in the P-40s I have seen were Parker valves ... about as good as you can procure anywhere in the world. The main gear shock absorption is pretty standard, too. Nothing innovative or stupid as far as I could see.

It IS tricky to connect the gear mechanism inside the wing but, once connected, it seems decently foolproof. By "tricky," I mean you can see the connection or you can put your hand on it, but you can't do both at the same time since your hand would block any vision of the connection by virtue of being in the same access point as your sight line. So, you can see it or touch it, but not both at the same time.

I really don't know of a systemic P-40 landing gear problem and find it hard to imagine it has one after seeing it.

Would be interested to find out about the CAF P-40 gear problem, though.

 

[pbehn]

Wiki says this "Pilots used to British fighters sometimes found it difficult to adapt to the P-40's rear-folding landing gear, which was more prone to collapse than the lateral-folding landing gear of the Hurricane or Supermarine Spitfire. In contrast to the "three-point landing" commonly employed with British types, P-40 pilots were obliged to use a "wheels landing": a longer, low angle approach that touched down on the main wheels first." But that is the early versions, it is not beyond the wit of any company to improve a design, most had their landing gear strengthened in some war.

 

[GregP]

So, the issue might be the down-lock?

To me, a 3-point would put WAY less stress on the down-lock for a rear-folding gear than a wheel landing, but I also wasn't there. We have had no issues with the landing gear on our P-40 or any of the P-40s in our airshows.

The only outside-of-normal issue I can recall in 18+ years was worn brushes on a Curtiss-Electric prop pitch control that was solved with new brushes on a visiting P-40. The symptom was failure of the prop pitch in crusie setting. That doesn't really cause an issue in cruise or when landing, but could make for a longer takeoff run if forced to fly again before being fixed.

 

[GrauGeist]

Going by memory, the P-36 and P-40 had a delayed or asymmetric retraction/extention with the gear and it was most often the left (port) one that caused problems.

 

[GregP]

It is a simple one-valve hydraulic system. When you select, "gear up," the system pressurizes and both gears usually initially start up. The airflow helps. Whichever gear has less friction comes up first. The two gears are not connected together in any way except by a hydraulic oil lines, pressure and return. When the first gear is up but not necessarily locked up, the rest of the fluid concentrates on the other gear. When they are both up, the pressure sets both uplocks.

In order to retract symmetrically, you need to design the system to do that. Otherise, it basically operates like a single-source for both gears.

Interestingly, if you have a P-40 up in jack stands and use the manual pump, you can get under it and hold onto the gear leg that moves first and, if you restrain it enough, the other one will start up. Works the same in any single-source, two-load system. But, if you design for two gears to work simultaneously, then they retract together always.

 

[GrauGeist]

Vought's F4U used a similar system, too.

 

[GregP]

I asked at the museum today and talked with a couple of guys who fly P-40s. Both say it is a slightly weird gear system, but it has no systemic weaknesses. That is, it has no tendency to collapse or malfunction if it is adjusted correctly. The brakes are likewise pretty decent if you keep up with things.

Like ANY retractable gear, if the down or up locks are not properly engaged, it will collapse.

They were doing regular, normal P-40 maintenance today and setting the gear door closure links, looking at the Allison, changing spark plugs, etc. Our P-40N was loving the TLC ... I'm sure. It's a solid airplane.

 

[Greyman]

So, the issue might be the down-lock?

The gear for the earlier versions (Mohawk and Tomahawk) were operated by a pushbutton that had to be held down the entire time you were operating the gear. I don't see a lowering time listed but one British trial mentioned 40-45 seconds to raise the gear and understandably described this process as 'annoying'.

The Tomahawk pilot's notes also say 'In order to ensure positive engagement of the locks the push button must remain depressed for a few seconds after checking the indicator. The hand pump should then be operated until it goes solid as a second check for locking, and the selector lever then returned to NEUTRAL.'

Considering this, I could definitely see pilots transitioning from Hurricanes running into trouble while learning to fly the new type (while on combat operations no less).

 

[GregP]

The gear for the earlier versions (Mohawk and Tomahawk) were operated by a pushbutton that had to be held down the entire time you were operating the gear. I don't see a lowering time listed but one British trial mentioned 40-45 seconds to raise the gear and understandably described this process as 'annoying'.

The Tomahawk pilot's notes also say 'In order to ensure positive engagement of the locks the push button must remain depressed for a few seconds after checking the indicator. The hand pump should then be operated until it goes solid as a second check for locking, and the selector lever then returned to NEUTRAL.'

Considering this, I could definitely see pilots transitioning from Hurricanes running into trouble while learning to fly the new type (while on combat operations no less).

That DOES seem annoying.

Later systems were MUCH easier to operate. You put the gear handle to "up" and watch for the up and locked indicator, or to down and watch for the down and lock indicator.

The manual hand pump is annoying and tiring if you do use it but, fortunately, you don't have to use it very often. Also unfortunately, that comes every time you have the P-40 jacked up and are checking the gear. SOMEONE has to play "hydraulic pump," and sometimes it was me. Whoever it is, they usually want the gear to move about two more times than you have arm strength.

Sort of like the proper torque for a head bolt is usually 20 foot-pounds before the bolt snaps off ...