Jetrader - July/August 2008 - 28

aviation history The Piston Engine – Part 1 By Bill Bath A The dynamo that started it all. Shown below, the engine that powered the Wright Brothers’ 1903 Wright Flyer 1. t this year’s ISTAT Annual Conference in Orlanyear do, Fla., J Johannes Einarsson introduced me to Joe Sutt as we sat down to lunch and menSutter tioned that I had been a ﬂight engineer on tion tioned t oned the Boeing Stratocruiser in the 1950s. Bo Joe’s ﬁrst words were to ask how many Jo times I had landed with all four engines time running. “Not too bad, actually,” I rerunn plied, between feathering an engine I p plie averaged 236 hours, though on most av Atlantic crossings at least one backA ﬁred. That sounds like a lot, but think of the shutdown rate of the Wright Aeronautical Corporation’s R-3350 Turbo-Compound engine on the Douglas7C. In 1958 Pan Am had 38 with failed pistons waiting at Heathrow for shipping to the Miami engine shops. Today, many pilots go though their whole career without experiencing a shutdown, as engine types with failure rate intervals better than 100,000 hours on twins are now common and have no cruise-time limit to the nearest airﬁeld on one engine. The R-3350 Turbo-Compound engine was the last of the big piston engines to power airliners that could cross the Atlantic regularly without an interim fuel stop—besides the DC7C, which entered service with Pan Am June 1, 1956, Lockheed’s 1649A Constellation, with the same basic engine and was placed in direct competition by TWA in May 1957. The writing was already on the wall; not only was Boeing’s ﬁrst 707 in the process of being assembled and Douglas was manufacturing the initial parts of the DC8, but BOAC had already been ﬂying its faster turboprop Britannia-100 on its routes to Tokyo and Sydney for more than a year and was preparing to ﬂy the stretched -300 with 130 seats nonstop and the one stop DeHavilland Comet IV jet to New York in 1958. New Developments Prior to the Wright Turbo Compound engine, which ﬁrst entered service in 1953 on the L1049C, the massive Pratt & Whitney R4360 had been in service on the Boeing B377 Stratocruiser since April 1, 1949, and both engines had terrible reliability problems, as their manufacturers struggled to squeeze a quart out of a pint pot. The turbo compound engine had three turbines driven by the exhaust gas and were connected to the crankshaft by ﬂuid couplings. Recovering the exhaust heat in this manner increased power by almost 20 percent. On the DC7C the land between the top piston ring and the piston crown would break off with distressing frequency. The P&W’s R4360’s cylinder head-heating problem with bank number four of seven cylinders was never solved satisfactorily. As a result, the ﬂight engineer was continuously faced with four sets of cylinder-head temperature gauge needles on the red line and had a ﬁnely tuned ear listening for the inevitable, almost inaudible backﬁre. So, how did aviation get from the 12hp of the 1903 Wright Flyer to the 3,500bhp of the 1943 P&W 4360 and 3,250bhp of the turbo compound engines in just 40 years? Like the engines, we are trying to squeeze a quart of history out of a pint of space. There were a number of milestones during the intervening years, particularly in the 1930s and ’40s, when research in the national wind tunnels, advances in metallurgy, isooctane parafﬁn and 115/145 octane fuel with tetra-ethyl lead, permitted the development of high powerto-weight ratio engines for combat aircraft ﬂying at high altitudes. Boeing’s upgraded B29 (B50), with the turbo-supercharged R4360 engine, had 28 The ofﬁcial publication of the International Society of Transport Aircraft Trading

Jetrader - July/August 2008

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