P36/P40 landing gear, top speed and weight penalty

[pinsog]

What was the weight penalty of the landing gear on the P36 and P40 over a standard inward retracting setup?

What was the top speed penalty for the P36? For the P40?

What advantage did the P36/P40 landing gear have over a standard inward retracting landing gear?

 

[tomo pauk]

What was the weight penalty of the landing gear on the P36 and P40 over a standard inward retracting setup?

P-39 (complete tricycle): ~620 lbs, might not include 'doors' for all 3 U/C members; for max TO weight of ~8450 lbs
P-40B/C: ~650 lbs, max TO weight I was able to find just above 8000 lbs. P-40 D introduced shorter U/C (legs?), max TO weight for later P-40s went a bit over 8500 lbs. I don't have max TO weight for ferry with 2 x 225 gal tanks for later versions.
P-51B/C: 781 lbs, max TO went above 12000 lbs for the P-51D/K, and just above 10000 ft for Allison-engined Mustangs.

All in all, the weight of the U/C does not look excessive for either of the three.

What was the top speed penalty for the P36? For the P40?

Who knows? My guess is 10 mph. Neither P-36 nor early P-40s were know as slow fighters per HP installed and with regard to their size.

What advantage did the P36/P40 landing gear have over a standard inward retracting landing gear?

That type of landing gear was not used just on those Curtiss fighters.
The F4U, F6F, AD-1 Skyrider, XF8B also used it. Benefits were more pronounced if tge idea was to carry many racks for bombs/rockets/drop tanks both under fuselage and under wing. It can also be used as dive brake, at least that is how the F4U used it.

 

[MIflyer]

Putting the MLG near the wing root on the P-40 and P-36, as well as on the Spitfire and BF-109, meant that the wing did not have to handle the weight and loads of a gear out on the wing, and did not have to accommodate the gear, actuators, and pivots inside the wing further out, where the wing was thinner.

For the P-36 it also meant it was easier to have a fixed gear version, such as the Hawk 75M/N/O, without more extensive redesign.

Of course the rotate and fold back gear was pretty much a necessity with the F4U, given the inverted gull wing, and on the F6F made it much easier to have folding wings.

The folding back wings of the F4F, FM-1/2, and TBF/TBM took up less room on the hangar deck, an important consideration on RN carriers where the armored flight decks led to lower ceilings. For the F4U the British versions had to have their wing tips clipped to fit in the hangar decks.

 

[pinsog]

Thank you both. Just wondering about eliminating the big gear bulges on the front of the wing to give the P36/P40 more speed. I thought there might also be a weight saving by using a more standard landing gear but maybe not. If they could both have gained 10-15 mph with different gear it would have made them both much more competitive.

F6F and F4U both had gear completely in the wing and more than enough power so it was fine for them

 

[MIflyer]

The P-35 had just about the worst retractable MLG of anything. The gear just came straight back and the wheel did not rotate as on the P-36. The MLG wheel fairings were huge and its hard to see how they could not have adversely affected the handling. Look at the XP-41 and P-43 and and its hard to believe they were from the same company a few years later.

But the P-35 and P-36 were hardly any different when it came to top speed.

 

[pinsog]

Yeah the P35 is a head scratcher for sure. Amazing that landing gear disaster could get through a company and get produced.

I think the P36 was 30 mph faster than a P35, something like 300 to 270. Although top speed for the P36 runs from 295-323 mph depending on who you believe. The official British test of a French Hawk75A-4 would do 302 mph at 14,000 feet with a Wright Cyclone engine.

 

[Shortround6]

The landing gear used on the P-36/P-40 and others was actually a Boeing patent and royalties were paid to Boeing

The Landing gear used on the P-35 wasn't actually all that unusual at the time. It was claimed to have the advantage of minimal damage if the plane was landed with the landing gear up, either due to mechanical failure or pilot error.

as Used by Curtiss the landing gear strut lay along the OUTSIDE of the wing and required no cut-outs/recesses in the wing structure.

When you are designing your first monoplane fighter with retracting landing gear you may want to keep the design of the wing a simple as possible and not be cutting to many holes or discontinuities in it.

 

[pinsog]

And things in the aircraft world from 1935-1940 were moving very fast and we are looking back with hindsight while they were trying to see the future.

 

[RpR]

As far as speed penalty, the P-36 and xp-40 had wheel spats that covered the tires in flight.
This may have made a difference in top speed in the long run.

 

[MIflyer]

That P-36 and P-40 gear looks pretty robust. I don't recall reading of too many collapses.

 

[tomo pauk]

They certainly weren't flimsy. Pic of the P-40N with 2 x 225 gal drop tanks (~2700 lbs + empty tank weight; metal tanks) is attached. Appologies for the bad pic from the manual, people that have the 'America's hunderd thousand' book, pg. 260, can take a look at what is probably the same pic, but of far better quality.
P-40 was capable to carry the heavy US torpedo, weight-wise

 

[yulzari]

The landing gear used on the P-36/P-40 and others was actually a Boeing patent and royalties were paid to Boeing

The Landing gear used on the P-35 wasn't actually all that unusual at the time. It was claimed to have the advantage of minimal damage if the plane was landed with the landing gear up, either due to mechanical failure or pilot error.
View attachment 476379

The Fairey Battle design allowed for in wing bomb cells but was also handy for Fairey's repeated offer to the Ministry to use twin engines in which the wheels would have been hidden behind the engine nacelles.

There was a brief moment when the Ministry was so hot for the next generation super engines that they considered the Merlin to be too intermediate and twin Peregrines would offer super engine power in present airframes until the Sabre/Vulture/Centaurus came to fruition. The Tornado/Typhoon was seen as the canine scrota of the future at the time and they would have been right bar the thick wing decision.

 

[MIflyer]

True. At the beginning of 1942 everyone knew that a single-engined fighter with less than say, 2100 cu in, was not going to hack it. The future was twin V-1710's, the V-3420, the R-2800, the Sabre and Centaurus, twin R-2800's and even twin V-4320's. The Germans were already there with the BF-109 and FW-190.

Then the two stage supercharged Merlin came along, unexpectedly, and changed everything.

 

[tomo pauk]

Re. the drag of P-40's U/C: the tail wheel was retractable, unlike in many Bf 109s and Spitfires. The XP-40Q was about as fast as the sometimes much vaunted Bf 109G10/K4 or Fw 190D-9.

True. At the beginning of 1942 everyone knew that a single-engined fighter with less than say, 2100 cu in, was not going to hack it. The future was twin V-1710's, the V-3420, the R-2800, the Sabre and Centaurus, twin R-2800's and even twin V-4320's. The Germans were already there with the BF-109 and FW-190.

Then the two stage supercharged Merlin came along, unexpectedly, and changed everything.

'Everyone expected', rather than 'everyone knew'?
There was also the turbo V-1710 around, making more power at altitude than engines on the Bf 109 or Fw 190.

 

[chuter]

The gear extending forward, retracting aft also allowed the aircraft to operate in flight with a slightly more aft CG (less drag but less stable) than pilots might have liked for airport operations while still allowing the aircraft to operate acceptably with gear down while taking off and landing. Even if the designer doesn't attempt to push the CG further aft to take advantage of this characteristic the aircraft will still gain additional stability with the gear down. A modern example of shifting CG would be the 747-400 which has (had) a fuel tank in the stabilizer into which fuel would be pumped to trim the airplane for climb and cruise rather than doing so aerodynamically which is drag inducing.

 

[pinsog]

Chuter, very nice. Learned something today.

Tomo Pauk, nice pic of the P40 with the giant wing tanks. I never heard of a P40 lifting that much, just a 500 pound or maybe a 1,000 pound bomb.

 

[tomo pauk]

P-40N was rated for heavy lifting:

 

[pinsog]

Wow. I had no idea. We all know of the P47, Corsair, P38 and Hellcat but I had never seen anything on the P40 for heavy lifting.

 

[tomo pauk]

On merely 1200 HP for take off for the P-40N.
Granted, the P-38 or P-47 will carry much more, 4000 lbs + full internal fuel and ammo

 

[GregP]

If any in here don't know how the gear pivoted 90° on the P-40, the main leg has a toothed quarter gear built into it and there is another quarter gear fastened to the wing underside with bolts. The two gears simply mesh as the gear moves backward, rotating the gear leg, without a drag link.