Re: Status of Maine 1649 Connies?

From:         Steve Lacker <>
Organization: applied research laboratories
Date:         16 Jul 96 13:59:52 
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  or MIME structure (Tim Takahashi) wrote:
>The Hercules was well under way by 1955; there was no
>serious attempt at making a turboprop Starliner..
>It seems that turbo-compound piston engines were
>maintenence headaches - any ideas for the popularity
>of piston engines?

I've wondered about that myself. The "popularity of piston engines" in the 50's
and early 60's was certainly a purely *American* phenomon. The British
developed the RR Dart, Bristol Proteus, and RR Tyne turboprops among others)
and flew them on some successful airliners (eg. the Vickers Viscount, Bristol
Britannia, and Vickers Vanguard respectively). Also, one extremely popular
American short-haul liner (the Convair 240/340/etc.) was re-engined with
British turboprops (the Napier Eland and the RR Dart) as well as with the only
American turboprop I can think of which gained wide popularity (the Allison
501, as used on the Electra and Hercules).

In the same time frame, the American companies were pushing piston engines to
their very limits, and at the same time developing turbojets. With the
exception of Allison, turboprops didn't seem to be a priority. Pratt & Whitney
and Curtiss Wright both produced piston engines on the high side of 3000 HP
(Pratt by going for large displacement in the R4360, CW by going with
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.

>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.

Steve Lacker	/	Applied Research Laboratories, The University of Texas
512-835-3286	/	PO Box 8029, Austin TX 78713-8029