P-38 question

[supercub]

Why did the props on a P-38 turn outward instead of inward to minimize the assymetric thrust if you lost an engein?
Brian

[Race5]

Re: P-38 question

It was for aerodynamic issues. Airflow generated by inwardly counter rotating props adversary affected airflow over the center section of the wing, and horizontal tail.

[Airrace7]

Re: P-38 question

The P-38 was powered by two liquid cooled, Allison V-1710 engines turning 11 1/2 foot Curtiss Electric, inward turning, counter-rotating propellers. The propellers rotated outward negating torque when both engines were operating. I am only aware of a few that were ordered by Britain that did not have counter-rotating propellers.

[JET1]

there were several experiments

..and the conclusion was that the opposing engines gave the best flying characteristics. The brits even mounted merlins on a couple of test mule early 38's...there are a couple of pics in the rolls royce heritage merlin book series.

[Skyracer]

Re: P-38 question

The simple answer is that outward turning prop's create less drag from interference with the fuselage and tail surfaces than do inward turning prop's, and either of those is more efficient than both prop's turning in the same direction. A simple aerodynamic explanation could get quite long so maybe this is best left with the "simple" answer.

P.M. me if you need the long answer.

[AAFO_WSagar]

Re: P-38 question

P.M. me if you need the long answer.

Hey Sky... you're an extremely respected member here and, if you feel like typing, I'd LOVE to read the answer here!

I'll call you and transcribe (I hate transcribing!) the process but this stuff is EXTREMELY interesting! (don'tcha just wanna type the answer!! )

Wayne

[AirDOGGe]

Re: P-38 question

The blades rotating outwards (away) from the cockpit to improve aerodynamics and the aircraft's stability for better gun accuracy.

This came with a negative effect. If an engine was lost, the torque of the remaining engine would push the wing with the dead engine downward. And if the pilot tried applying full power on the good engine to compensate for loss of total power, the aircraft would yaw/roll into the dead engine, often resulting in a crash.

[dvddude]

Re: P-38 question

The blades rotating outwards (away) from the cockpit to improve aerodynamics and the aircraft's stability for better gun accuracy.

This came with a negative effect. If an engine was lost, the torque of the remaining engine would push the wing with the dead engine downward. And if the pilot tried applying full power on the good engine to compensate for loss of total power, the aircraft would yaw/roll into the dead engine, often resulting in a crash.

A P-38 pilot once told me that, depending on airspeed, if you lost an engine on takeoff, the first thing you might have to do is reduce the power on the good engine - something that is entirely counter-intuitive to a lot of airplanes because of what you are talking about.

[dvddude]

Re: P-38 question

Hey Sky... you're an extremely respected member here and, if you feel like typing, I'd LOVE to read the answer here!

I'll call you and transcribe (I hate transcribing!) the process but this stuff is EXTREMELY interesting! (don'tcha just wanna type the answer!! )

Wayne

I too would like to hear a very long and detailed aeronautical explanation of what happens. I heard it long ago, but forgot all but the basics of it.

[supercub]

Re: P-38 question

Depending on airspeed, on any conventional twin if you loose an engine, you may have to reduce power on the good engine......if not, you'll do what's called a Vmc roll.........ie, yaw, roll, crash....happened at our local airport a few years ago, with a very inexperinced multi engine instructor......she allowed the student to turn off the fuel on one engine and elected to do a go around....when they pushed both throttles up........only one powered up and they were slow.....below Vmc......correct response should have been to reduce power on the good engine.....lower the nose to obtain single best rate of climb......but they didn't and the plane yawed, rolled and crashed and burnt, killing the student.....instructor survived but was badly burned.......basically nothing left of the airplane.

[JET1]

yep...we lost one in SLC due to that

engine failed on takeoff due to carb blockage and it snapped into the ground killing the pilot and destroying the aircraft. Lefty used to tell me that you had maybe 1 to 2 seconds at most to do everything right to save the plane in that scenario.

[KAHNZILLA]

Re: P-38 question

I understood it caused bad elevator flutter and all the engineers did was swap 1 for 2 and 2 for 1 engine, now they turn outside. Thanks, KC