Re: Status of Maine 1649 Connies?

From:         falke@pweh.com ( 0 Falke_Charlie phone dist )
Date:         17 Jul 96 04:05:34 
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Steve Lacker <slacker@arlut.utexas.edu> wrote:

> turbo-compounding in the R-3350). I remember reading once that Pratt was
> developing a turbo-compound R4360 for a B-36 follow-on, which would probably
> have passed 5000-6000 HP rather easily. Of course, it would have probably
> suffered the maintenance/reliability headaches that the R-3350TC had.

The R4360 had sufficient maintenance headaches as it was.

> >From an engineering standpoint, turbo-compound engines are truly amazing, and
> an interesting thing to study. They also were so complex and stressed that they
> beg the question "why bother?" in comparison to a turboprop. A friend once
> described a night takeoff on a DC-7C with R3350TC engines: during climb, the
> exhaust turbine plumbing glowed not a dull red, but a bright yellow, visible
> through the cowl flaps. During cruise (after a pause to shift the blowers) the
> plumbing "only" glowed red! If you look at photos of DC-7C's and turbo-compound
> powered Starliners, you'll notice that even on ships with shiny paint jobs, the
> area of the cowling from the cowl flaps aft is cooked black from the heat (and
> no doubt the typical radial engine oil leakage/burning). If I sound a little
> amazed that they flew at all, much less on schedule, its because I am.

The answer to "why bother?" is specific fuel consumption.  The
recovered energy in the exhaust put the fuel efficiency of turbo
compounds in a class by themselves among aircraft engines. They were
almost as good as diesels!

   As far as why there weren't more American large turboprops, the
main answer is the same, the poor SFC of the early turboprops wasn't
offset by their lighter weight, in comparison to recips, nor were they
that much faster than the best recip powered airliners.

Charlie Falke
System Test Team Leader         Pratt & Whitney Aircraft
203-565-9063 desk 1261 fax      m.s. 121-05
203-565-6462 x286a stand        400 Main St.
203-565-1261 Fax, PW office,    East Hartford, Ct 06108