The Rumble of Thunder in the Sky, 1HP per LB

Date:         11 Feb 98 04:26:39 
From:         National Aero Safety <>
Organization: Aviation / Industrial Safety Services
Followups:    1 2
Next article
View raw article
  or MIME structure

(This is the second try at posting this article, as Dejanews is getting

There have been many Great Radial Aero Engines produced around the world
beginning about the second decade after the turn of the century, and
continuing into the present.

Of all the examples constructed by various Manufacturers, to include
BMW, Pratt & Whitney, Wright Aeronautical, and others, the most
noteworthy of the lot are probably the P&W R-4360, the Wright R-3350,
and the P&W R-2800.

To concentrate on the largest Engines, both the 4360, and the 3350 could
be considered Monsters in comparison to other "Round" Engines of the

The designations of piston Aero engines are confusing to some, but quite
simply, the numbers are Cubic Inches.  Therefore the R-4360 is an air
cooled radial designed power plant, having 28 cylinders comprising 4,360
Cubic inches, producing 3,500 Horse Power while weighing in at at trim
3,500 Pounds(1,575 KG).

The Wright R-3350 Cyclone & Turbo Cyclone, came in various Horse Power
ranges from 3,250 to over 3,400 HP.  It was, and is, a twin row design,
of 18 cylinders(9 per row), comprising 3,350 cubic inches, producing the
enormous Horsepower range outlined above.(I don't know the weight,

Of the two Monster Engines, the Pratt & Whitney 4360 was said to be the
most Technically Advanced and complex reciprocating aircraft engine that
was ever produced in large numbers.  I would imagine that experienced
mechanics may argue that the Turbo Compound version of the Wright 3350
was more complex, or at least was more prone to break-down? Regardless,
these great machines were magnificent at hauling large Airframes into
the Sky for various purposes.

R-4360's were found on B-50's; KB-50's; B-36's; C-97's; KC-97's; Boeing
377 Airliners; Douglas C-124 GlobeMasters; and later versions of the

R-3350's were found on the B-29's; C-121's; P-2 Neptunes; early C-119's;
The DC-7 Airliner; The Lockheed Super Constallation 1049 Airliner; and
the Douglas A-1 SkyRaider.

Believe it or not, these were not the largest Radial engines ever built!
That honor goes to "Lycoming", who designed and tested the XR-7755.  The
XR-7755 had 36 cylinders, 9 overhead camshafts, weighed 6,050
Pounds(2,713kg), was liquid cooled, and produced 5,000 HorsePower when
the project was terminated.  The engine was designed with "7,000
HorsePower" in mind, but the Government Funded Project was dropped
before those numbers could be obtained.

By comparison with Liquid cooled in-line, or "V"-in-line Aero Engines,
there is NO COMPARISON!  The Allison V-1710-G6 weighs approximately
1,600 Pounds(717kg), and produces only 1,250 HP.  The Rolls Royce Merlin
is roughly the same weight and produces only 30 HP more.

[As a side note, as of 1995, Rolls Royce has wholely Owned the Allison
Engine Company in the US.  Of course the BMW Organization holds the
Majority Interest in BMW-Rolls Royce GmbH, which is the principle "Risk
Partner" on the Trent Engine and others, in addition to the BR-700
Series that it produces in Germany. Pratt & Whitney still builds Aero
Engines(Jets), and Curtiss Wright manufacturers Control and actuation
systems for the AeroSpace Industry Worldwide.]

If someone would care to discuss the Propellers used by these engines
and others, please step right up and Post!