Tracked landing gear ...

[Mark Allen M]

In the 1940's and 1950's, there were several tracked landing gear systems developed for the purpose of allowing landing on soft ground and/or using particularly heavy aircraft such as the B-36. For the first half century of manned flight, landing gears overwhelmingly had only a single, large wheel per leg. This was the cheapest and simplest way to ensure ground mobility, but ran into trouble when aircraft grew in size. When the XB-36 prototype started testing in 1946, only three airfields in the US were able to tolerate the 156 psi pressure of its single main wheels.For operating from unprepared surfaces, tracked gears were the straightforward transfer from tank experience to landing gear design.

However, another route which was tried at about the same time was to increase the number of wheels the aircraft rests upon. With hindsight, the multi-wheel way was the better solution and has prevailed. When used with large, low-pressure tires it does not exert significantly more ground pressure than a tracked gear.

A couple of youtube clips.
A-20 testing
https://www.youtube.com/watch?v=X9vmamugkI4
XB-36
https://www.youtube.com/watch?v=eDCgMlomhvM

Below A few photos of the Convair XB-36 with experimental tracked landing gear, to reduce ground pressure for soft-field use. The original B-36 landing gear consisting of a giant tire weighed way more than the tracked version and was such a point load that the gear was prone to sink right thru any but the thickest concrete of the day. The B-36 was actually designed before WWII but was completely impractical because there was no landing gear that could support it and no engines powerful enough to lift it. That changed after the war with the P&W R4360 engine of 4000+ HP and new tire technology. However the idea of one main gear wheel was from the '30s and soon the main gear had 4 wheels of smaller size.

Last edited by Mark Allen M on Mon Jul 02, 2018 1:58 pm, edited 1 time in total.

[Mark Allen M]

Below a Boeing B-50B-40-BO Superfortress 47-118 c/n 15802 as EB-50B, tested with caterpillar track undercarriage

[Mark Allen M]

Below a Douglas Havoc TA-20H 44-466 with experimental tracked landing gear, 1943

[Mark Allen M]

Here's a P-40 below with an attempt at main tracks for gear.



Same goes for the C-82 below.

[Mark Allen M]

And finally something a bit different. Wondering how common it was to move large airplanes around with this system.

[C VEICH]

Were the tracks ever used operationally on any airplane? Seems like they tried it on everything.

[JohnB]

I believe the complete story on USAF interest in the immediate post-war years goes something like this...
In the early days of SAC, the plan was to have B-29/50s land on remote Alaskan airfields/ice pack/tundra for refueling and to get their (nuclear) bombs, which were then centrally housed at places like Medina AFS (Lackland) and Deep Creek AFS (Fairchild) by the AEC
The support aircraft were to be C-82s and possibly C-97s.
The tracks were considered a key part of that plan.

I think the B-36 just tried them in an attempt to lower the weight of its footprint.
Notice the AC shown is the prototype which first flew with massive single wheel main gears (like the XB-19) which placed so much stress on the pavement, it was limited to a few airfields...

Last edited by JohnB on Mon Jul 02, 2018 6:17 pm, edited 1 time in total.

[Taigh Ramey]

And finally something a bit different. Wondering how common it was to move large airplanes around with this system.

This B-29 looks like it was a mother ship for the X-1 or other experimental aircraft. Take a look at the bomb bay doors. I bet the method of moving it at this 45 degree angle was to get it positioned over the aircraft in the pit to load up in the bomb bay.

[DB2]

Here's a P-40 below with an attempt at main tracks for gear.

My grandfather was the flight test engineer for the P-40 project. In fact he took that photo of the P-40. He said they flew the P-40 once around the pattern, and he thought he held his breath the whole time. But it worked. The idea was to operate P-40s off beaches. He said a general showed up and said if they need to fly planes off beaches, they'll call the Navy. End of project.

[Randy Wilson]

I think Taigh is on the right track and this document about modifications to the B-29 to carry the Tallboy 12,000 pound bomb may be of interest. The copies of the photos are all binary B&W and not of much help. This loading setup may be a later development. Found by searching on the aircraft serial number 42-63577. Just FYI.
http://www.dtic.mil/dtic/tr/fulltext/u2/b972848.pdf

Randy

[HMFischer]

The band brakes on the McCormick I9 were not that good with just the tractor. It doesn't look the there are any brakes on the dollies and I don't think the little aircraft tug would help much either. Don't go down hill or go very fast!

[sandiego89]

I believe I recall reading that the track gear on the XB-36 was also very noisy- if 6 droning 4360's wasn't enough already. SAY WHAT???

Good essay Mark.

Good link Randy, found the report on the Tall Boy interesting. The hole in the bomb bay doors left after the tall boy release resulted in 11% range reduction- lots of drag with the hole. They recommended some type of covering to fill the hole- exactly the type of fit they devised for the similar cut out in the GRB-36/RF-84 Fighter Conveyor program.

Imagine the Tall Boy may have gone into use for the invasion of Japan.

[Chris Brame]

Here's a P-40 below with an attempt at main tracks for gear.

My grandfather was the flight test engineer for the P-40 project. In fact he took that photo of the P-40. He said they flew the P-40 once around the pattern, and he thought he held his breath the whole time. But it worked. The idea was to operate P-40s off beaches. He said a general showed up and said if they need to fly planes off beaches, they'll call the Navy. End of project.

DB2, do you have any more info on this P-40 and where this was taken? Notation on the cowl reads "Engine sprayed 1-1-44" and "Don't turn" on the prop; was this plane also being used to test a preservative oil? Very unusual for an early model (B or C?) to still be in use at that late date. Do you have a larger copy of the photo?

[Dan K]

No tracks, but the thread brought to mind the recent conversion of Legacy Flight Museum's O-1 to "Whitaker wheels".

Does any warbird with a tracked gear system survive in a museum?


(Hope I didn't digress too much.)






https://www.facebook.com/LegacyFlightMuseumRexburg/

[carseneau]

Were these prototype gears even able to retract? Track life must have been seen to be very short. A lot of mass to get turning upon touch down. Looks risky to land on even slightly slippery surfaces.