enginehistory.org

[tfey]

I've been studying the XF-12 via Mike Machat's very nice book (Specialty Press), and I'm thinking some of the information in the literature may be incorrect. Machat's book says the exit shutters on the bottom of the nacelle are the exhaust exits for the turbos. There is even a pencil drawing by Machat showing smoke billowing from one of the ventral shutters on start up. The books also describe all the design work involved in getting the exhaust to come out of the very back of the nacelle for 250 HP worth of thrust recovery per nacelle.

In looking at the pictures, I see no stainless steel in the ventral shutter doors, ducting, or the nacelle panels near the exits. The shutters are adjustable, but shaped more like a curved P-51 duct than anything else, and nothing like the flight hoods on the XF-11 or a P-47 for that matter. And even more indicative is that there is no exhaust staining, soot, or oil streams from the ventral shutters. If there was engine exhaust coming out of these openings, there would be some sooting.

My guess is that one shutter/exhaust in each nacelle is for the intercooler, and the other shutter/exhaust is for the oil cooler. I'm guessing the turbo exhausts are collected and ducted out the aft end of ther nacelle. A close examination of the upper nacelles shows two beveled, flush exhausts with some downstreaming soot, and I'm betting these are the waste gates for the dual turbos.

I'd love to see a a picture of an open nacelle, or some pics or film showing engine start up, but haven't even seen such documents. The short XF-12 film on youtube is no help. I bet no smoke is coming out of the ventral nacelles on start-up, but maybe from the upper waste gates and the exit at the rear of the nacelle.

Or I could be all wet on this.

Anybody have pictures or knowledge, one way or the other?