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P-38 engine / prop & other details

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  • Member since
    December 2002
Posted by Bossman on Saturday, November 22, 2003 9:46 AM
Thanks so much for the feedback Melgyver & Stinger !

It's "good news - bad news" for me. The good news is that I will know what to do next time and I found out interesting stuff in the process. The bad news is that Murphy's law rules over my model building and I'll have to switch the spinners in addition to correcting the bad blade. Oh well - One of the spinners wasn't spinning totally freely anyway.

Thanks again !
  • Member since
    March 2003
  • From: Lafayette, LA
Posted by Melgyver on Friday, November 21, 2003 11:09 PM
This is where good research comes into model building. Stinger was close, but it was actually buffeting of the elevators that caused the counter rotation of the engines to be reversed causing both to be critical in an engine out situation. Check out Squadon Signal's In Action # 1109, Detail and Scale Vol. 57 on the P-38, XP-38 through P-38H, or Wings 1976 April issue, The XP-38's. In normal twin engine aircraft both rotate clockwise when view from the rear of the engine. If you lose the right engine you can firewall the left and the resulting torgue will help lift the "dead" right side. If you lose the left and increase the right too fast the torque will push the left wing down and you are going to roll. So initially the the inboard counter rotation of the XP-38 would illiminate a "critial" engine. However they both became critical when they were changed to outboard rotation and that is when losses of pilots and planes became a reality. My father was an aircraft mechanic with the 5th AAF in the Pacific Theater and wittnessed more than a few P-38 crashes due to an engine out during take off and the resulting roll or belly landing on full external fuel tanks. The P-38 "Scatter Brain Kid" was lost here in Lafayette in 1974 due to an engine out because of fuel starvation on take off and resulted in a slow roll and stall with fatal consequences. He was used to flying a normal twin engine. Hope that answers the counter rotation question.

Clear Left!

Mel

  • Member since
    January 2003
  • From: Everywhere
Posted by stinger on Friday, November 21, 2003 9:04 PM
Bossman - The easy way to remember port and starboard is that port is left, and both words have four letters.
Regarding the rotation of twin engines, the P-38 has unique story to it. When the first prototypes were introduced, the props rotated inwards(such as from the top downward, or, viewed from the pilot, left - clockwise, right - counterclockwise). The resultant propwash outboard of the engines caused an increase in the "apparent" angle of attack of the wingtips pushing toward a stall. As long as both engines were running, both wings would lift equally, but if an engine went out, the wing on the bad side would suddenly have more apparent lift, and coupled with the immense torque of the good engine would flip the plane on its back in a heartbeat. The P-38 had a very bad initial reputation because of this, but once the engine rotation was reversed, it became a very well behaved and formidable aircraft. for some bizarre reason I happen to know this about the P-38. Probably from years ago when I built the old Monogram kit.
As for other twin engined aircraft, I cannot tell you. But now you've got me thinking about it myself. I'll see what else I can find out.

May an Angel be your wingman, and the Sun be always at your six

  • Member since
    December 2002
P-38 engine / prop & other details
Posted by Bossman on Friday, November 21, 2003 11:43 AM
I'm working on a 1/72 scale P-38 and had a little mishap - one of the prop blades broke off the left spinner (from the pilots point of view - I can never remember the port or starboard deal). I was all proud of myself about the way I was able to make well alligned pin drill holes in the spinner and in the blade - stretch some sprue and use it as a pin to hold it back on, etc... I got it pefectly alligned (or so I thought). Two days later when I returned to work on it, I realized what a bonehead mistake I made. I used the right side prop blade to guage how much of an angle to set the prop blade at. The problem is that they are counter-rotating engines, so now the left spinner has a single blade that is angled the wrong way. This is the long way of leading to the question that popped up in my head after that...

Which way do the props rotate on a dual engine aircraft ? Is it Left Engine - counterclockwise, Right Engine - Clockwise (from the pilot's point of view) Or is it the other way around ? I didn't even think about it when I was doing the assembly. I just picked the first prop I had in my hand and put it on the first side that was available. Imagine the pilot's surprise if I were building the real thing - A real noisy plane that taxi'd backwards ! I should probably stay away from building R/C aircraft.

If anyone can shed some light on this - I would certainly appreciate it
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