The P-36 "Grand-Daddy" of modern fighters circa 1941 ...

[CORSNING]

I have tried to bring up recent topics in order to engage in conversation.
No luck so far. I am constantly (in perpetual motion) researching WW2
fighter aircraft performance. I have just begun to surf this site....cool.
Anyway, any help would be appreciated.
Thank all in advance, Jeff

[airnutz]

I have tried to bring up recent topics in order to engage in conversation.
No luck so far.

Welcome CORSNING! Saturdays are generally pretty quiet...folks are out flying or in the hangar doing schtuff. Things pick up during the week quite a bit. To answer your question on the previous page...All Nubes get the "former lurker" tag. It's a heading that comes automatic with your first posts...it's part of the program. It just means if you had been passivley following the discussions, "or lurking", you are now formerly one of those.. Have fun and I hope you enjoy your experience here...

[Dave Hadfield]

Don Berlin got a lot of things right with the P-36, and P-40. Not the landing gear of course, that's a disaster, but the wing is really excellent.

I've never flown the P-36 or Hawk, but I have 150 hours in the P-40. I love the way it rolls and maneuvers. I understand the P-36 is even better.

For a 1934 design, it really was a ground-breaker.

[Rick65]

Dave
I always enjoy your "hands on" comments
Would you clarify what is so disastrous about the landing gear, apart from lack of streamlining?
The P-40 operated out of a lot of rudimentary strips and I haven't read many reports of undercarriage failure.
Wasn't the system a Boeing concept that Curtiss had to pay royalties on?

[CORSNING]

Welcome CORSNING!


Thank you airnutz.

Mark,
Very nice P-36 pictures sir.

Joe,
Once again, from what information did you derive the conclusion that the P-36
could outturn a Ki.43???

[Dave Hadfield]

There is no visual or auditory indication of gear downlock. There are indicators that the gear is extended, but not whether actually locked.

Pictured abound of P-40s on their bellies by the side of the runway. That is why.

To lock the gear requires movement of a hydraulic valve, pumping the hand pump until it is rigid, then selecting that valve to OFF, not leaving it in DOWN. Not intuitive.

Plus the Flap valve is on the same mixing-box as the gear valve. It is VERY easy to raise the gear instead of the flaps after landing.

But the wing is lovely. I'd much rather do an aerobatic display in the P-40 than the Mustang. It rolls faster and can be kept tighter to the crowd.

[Rick65]

Thanks Dave.
With all the risks that a WW2 pilot faced it is sad that such a key system as undercarriage control was set up to add to them.
I guess this sort of issue on the P-40 and similar ones on others led to the end of war/post war research on human factors and ergonomics ie designing controls to make it easier for the pilot to get it right in all circumstances.

[Dave Hadfield]

Yes, quite right. But it started even earlier. By the time the 2nd generation WW II fighters were designed, like the Mustang and I presume the Hellcat, they made the gear operation much simpler. (Because there had already been gear accidents.)

One lever or switch, in a different location than the flap lever, with a simple movement, then wait for a green light (s). Or red.

Don't forget that when they were designing the P-36, starting in 1934, the whole idea of a high-speed all-metal, pursuit ship; with retractable gear, controllable pitch and enclosed cockpit, was brand new.

They got a lot of things right.

Dave

[CORSNING]

Gives a good appreciation of Nikolay Polikarpov's TskBK-12 (I-16) which first flew
on 30 December 1933, doesn't it?

Hi guys, Jeff

[Deuelly]

There is no visual or auditory indication of gear downlock.

Dave, most models of the P-40 had a gear horn or gear light to indicate down and locked.

Brandon Deuel

[Dave Hadfield]

Brandon -- you'd think so! It makes sense, right? If the dial says "Gear Down", then it's down-and-locked!

Except it ain't!

All the gear indicators do in a P-40 is tell you that the gear is extended. They do NOT tell you if it's locked.

Most gear systems have an over-center link, or a strut, or some external physical barrier that deploys at the end of the gear-down cycle to prevent it collapsing. The P-40 doesn't.

The actual locking mechanism is inside the hydraulic cylinder. An inner ram pushes a circle of teeth/cogs into crenellations, which lock the parts of the cylinder together, which is the only method of gear-lock.

Since this happens inside the cylinder, there is no way to put a micro-switch in it.

Here's a slide from my P-40 Groundschool, showing the parts.



The only way to confirm that the gear is locked down in a P-40 is to extend it normally via the electric pump, then swap hands and pump the hand-pump handle until it is rigid, then immediately move the gear lever upwards from the DOWN position to OFF.

If you allow the hydraulic pressure to bleed away within that cylinder, then the pawls retract from the crenellations, and you have no way of knowing about it until you touch the brakes and the gear collapses.

[Dave Hadfield]

Hey, Brandon, I should have done a search on your name before I posted. Sorry for the lecture. I see you've helped build P-40s. I remember that Oshkosh Grand Champion one from 2009 very well.

But maybe the info will help someone else avoid making a mistake.

Dave

[Deuelly]

No problem Dave I understand. I do feel however that someone may have misinformed you regarding the P-40 gear lock system. The plunger that locks the gear pawls into place effectively locking the gear also pushes a pin in the cap of the gear actuator when it is fully locked. That pin triggers a switch though a paddle mechanism. The switch is wired into the gear horn/light circuit and gives you indication of positive lock of the gear system.

[Dave Hadfield]

Interesting.

We don't have that in our "N-1". We have the paddle-switch, which is activated by the final movement of the gear, and connects to the light and horn, but it doesn't bear any relation to what's happening inside the cylinder -- the actual lock -- as far as I know.

This is the switch you mean, right?

[Dave Hadfield]

The other aspect of using that as a gear-down check is that you only know about it when you pull the throttle back to nearly idle. If you wait until the flare it's too late, and if you do it in the downwind leg, it's a bit hard on the engine and prop.