1951 Pontiac Chieftain

[Hooli]

Ahh so I've got a P38 XJR too.

[mercrocker]

Anything that cracks and goes rusty is codenamed P38 so you know which Holts product to buy.

Well, hopefully not everything....

p-38-lighning-in-flight.jpg.pc-adaptive.1920.medium.jpg (259.01 KiB) Viewed 2278 times

[Hooli]

Anything that cracks and goes rusty is codenamed P38 so you know which Holts product to buy.

Well, hopefully not everything....

p-38-lighning-in-flight.jpg.pc-adaptive.1920.medium.jpg

Well the early ones had the tails fall off due to compressibility in dives.

[mercrocker]

Didn't know that! Phil was right, then.

[LynehamHerc]

There's actually a 133 page and growing P38 thread that covers this and other things on an Alternate History forum that I read.
Compressibility issues were an absolute bastard for planes of that performance, locked ailerons, reversed controls etc..

[PhilA]

20210213_121747.jpg (409.67 KiB) Viewed 2255 times

Bought a new radiator cap that actually holds pressure.

Found a leak or two. That crack goes further than I thought.

[LynehamHerc]

Anything that cracks and goes rusty is codenamed P38 so you know which Holts product to buy.

Well, hopefully not everything....

p-38-lighning-in-flight.jpg.pc-adaptive.1920.medium.jpg

Well the early ones had the tails fall off due to compressibility in dives.

I just came across this.
It's certainly too much information but you don't have to read it:

To properly understand the compressibility problem in the P-38, one has to understand that the lockup was primarily elevators and not ailerons in that aircraft. This was another problem that aerodynamicists had trouble visualizing. There was AIRLERON lockup, but this was not a main wing problem as it was a HAMMER coming off the pilot pod on the horizontal stabilizer problem, and by hammer I mean a harmonic effect that forcefully oscillated the elevators (flutter) as the shock waves hit until pressure equalized and the control surfaces exceeded both the mechanical control forces available to move them and the tensile strength of the aircraft structure. The tail tore off and that indicated to "Kelly" Johnson, that he had the "tail control" issue. It was in the main wing spar that the "hammer" was set up, but it was definitely a tail control issue. He had to stop that hammer from forming in the first place. It was the era of "intuition", and he mentally visualized the wind flow pattern and had NACA and test pilots test for it to determine if his hunches were correct; to put numbers to the concept he imagined. My guess is that Stack beat him to the root cause, but it was Johnson who figured out where the "unstick at the upper boundary layer occurred. What I do not understand, is why Johnson missed the wing sweepback solution, which was the other way to deform the shock wave?

Sorry for the serious divergence Phil.

[Hooli]

Well, hopefully not everything....

p-38-lighning-in-flight.jpg.pc-adaptive.1920.medium.jpg

Well the early ones had the tails fall off due to compressibility in dives.

I just came across this.
It's certainly too much information but you don't have to read it:

To properly understand the compressibility problem in the P-38, one has to understand that the lockup was primarily elevators and not ailerons in that aircraft. This was another problem that aerodynamicists had trouble visualizing. There was AIRLERON lockup, but this was not a main wing problem as it was a HAMMER coming off the pilot pod on the horizontal stabilizer problem, and by hammer I mean a harmonic effect that forcefully oscillated the elevators (flutter) as the shock waves hit until pressure equalized and the control surfaces exceeded both the mechanical control forces available to move them and the tensile strength of the aircraft structure. The tail tore off and that indicated to "Kelly" Johnson, that he had the "tail control" issue. It was in the main wing spar that the "hammer" was set up, but it was definitely a tail control issue. He had to stop that hammer from forming in the first place. It was the era of "intuition", and he mentally visualized the wind flow pattern and had NACA and test pilots test for it to determine if his hunches were correct; to put numbers to the concept he imagined. My guess is that Stack beat him to the root cause, but it was Johnson who figured out where the "unstick at the upper boundary layer occurred. What I do not understand, is why Johnson missed the wing sweepback solution, which was the other way to deform the shock wave?

Sorry for the serious divergence Phil.

Interesting that they got the same issue as Typhoons with I think a different cause. The Typhoon was traced to something to do with the elevator balance weights causing tail flutter till the tail fell off.

Sorry Phil.

[LynehamHerc]

Is it worth setting up an aircraft saddoes thread and transferring these into it?

[Hooli]

Could be, I think we had a 'things wot fly' thread once. I'll look for it later.