twin props

[Falcon500]

I just read an article (well more of a verbal battle) in another forum in which they were struggling with the fight of "critical engines" and torque. they couldnt figure out why the pre-production model of the P-38 had inward turning props and the production model had outward turning props. They spoke of CoG and
tail-planes in propwash and what not. I sat in my chair confused, wondering.

All i could come up with is, when your engines are mounted outboard from centerline, like the P-38, the torque on the whole plane is going to be pretty influencial. I always picture CoG like a bubble, im not sure why, i guess because it changes and moves. anyway if you are turning in a tight turn to the left, if you slow the engine that is closer to the ground that should pull plane tighter, right? at least with outturning props, so that would give you tighter turning, with both left and right, intsead of left or right like most single engine fighters.

so in the P-38 i see the CoG bubble kinda like an egg in frying pan, not quite a half oval, its a sphere with a disk shape, and when you change the speed of one of the engines i picture the center sphere shift and the whole bubble stretch out. making the bird laterally more unstable.

I was just questioning my knowledge of physics and MY OWN piloting knowledge. not that i have a whole lot of either.

Comments welcome

[jimclarke]

I believe it had something to do with airflow.  One export version for Britain had engines that turned the same direction.  It also lacked superchargers.  This version was rejected by the British because of the adversely affected performance.  If I could just find my P-38 book I'd probably find the answer on the changed direction of rotation.

Jim

[james007]

Falco I posted a list on historical on general information on World two related history and its planes. I"am not saying the answer is there. But check it out and maybe you will there.


1.http://www.simviation.com/cgi-bin/yabb/ ... 9;start=45

James007

[jimclarke]

OK, I found my P-38 book (P-38 in Action by Larry Davis-squadron/signal publications).  Here is an exerpt:

"The original C series engines had the propellers rotating inward toward the fuselage while the F series engines had the propellers turning outward.  The use of the outward turning propellers eliminated a downwash which disturbed the airflow across the center wing section and eased the problem of tail buffet."

Jim

[Falcon500]

Ha Ha! I knew it!  I was not even close