Why did the Brits order the P-38s without counter rotating engines?

[Randy1]

I am sure they had a good reason.  Anybody know why they would have made this decision?

[Randall172]

one problem with the counter rotating props, is that the engines are essential the same except exactly opposite, so many parts are not interchangeable. This causes supply problems.

[nrshida]

Logistics more than likely. Early Whirlwind prototypes had contra-rotation props too which was even easier with the Peregrine engines. They dropped that too.

[bozon]

I am surprised that the RAF did not order P38s with two reversed engines.
That sounds a very English thing to do.

[FLS]

They wanted to use the same engines they already had for the P-40 Tomahawks so they also skipped the turbosuperchargers.

[Greebo]

Weren't the turbochargers in short supply or export restricted? Seem to recall something to that effect.

Having the whole engine rotate the opposite way was a pain for supply reasons. So the two counter-rotating Rolls Royce Merlin engines fitted to the DH Hornet fighter were identical apart from the propeller reduction box fitted to the front. One of these had an extra idler gear that reversed the propeller shaft rotation. This proved useful when it was found the Hornet prototype was laterally unstable. The problem was the prop wash creating a low pressure area around the vertical stabiliser. So DH spent a couple of hours swapping the two gearboxes and props over to reverse the prop wash direction. This created a high pressure area over the stab which fixed the problem.

[bustr]

Wouldn't the extra idler in the reduction box create a slight time differential for harmonizing rpm's?

[Ack-Ack]

They wanted to use the same engines they already had for the P-40 Tomahawks so they also skipped the turbosuperchargers.

[Greebo]

Wouldn't the extra idler in the reduction box create a slight time differential for harmonizing rpm's?

I would have thought the difference would be negligible, probably less than that between engines of varying ages. Twins generally had a control to let the pilot tune out the variation.

[Randy1]

They wanted to use the same engines they already had for the P-40 Tomahawks so they also skipped the turbosuperchargers.

I wonder then when they ordered the P-38s, what role did they have in mind for the plane?

Thanks for the replies.

[Ack-Ack]

I wonder then when they ordered the P-38s, what role did they have in mind for the plane?

Thanks for the replies.

Evaluation as a fighter.

[Randy1]

Evaluation as a fighter.

Must have been evaluated for low altitude interceptions I would guess.

[FLS]

Must have been evaluated for low altitude interceptions I would guess.

The aircraft was likely evaluated against the current threat and compared to the current available fighter inventory. WW2 started with biplane fighters still in service and finished with jets. Early orders didn't anticipate the rapid pace of development.

[Ack-Ack]

The aircraft was likely evaluated against the current threat and compared to the current available fighter inventory. WW2 started with biplane fighters still in service and finished with jets. Early orders didn't anticipate the rapid pace of development.

Damn, you're on a roll!  You explained it pretty well.

[LCADolby]

Damn, you're on a roll!  You explained it pretty well.

  Go FLS