The hard work of evaluating the suitability of the CF-35A

Professor Michael Byers of the University of British Columbia has produced a report for the Canadian Centre for Policy Alternatives on the presumed preference of Harper Government for the F-35A Lightning II as the next fighter jet for the Royal Canadian Air Force. The title summarizes the argument: “One Dead Pilot: Single-Engine F-35 a Bad Choice for Canada’s Arctic”. This issue of the appropriate number of engines for any plane has been around a long time. Today, the presumed safety of two engines remains a significant argument for proponents of several types of twin-engined fighters, including Boeing’s Super Hornet, Dassault’s Rafale, and Eurofighter’s Typhoon. As Byers’ paper has received considerable attention in the press, it’s worth critiquing.

There are a lot of minor problems with this work. Perhaps the most egregious is the reference (pp. 19–20) to American F-16s flying off aircraft carriers. While that looks foolish, deleting it doesn’t hurt the argument. Somewhat less painful, but also unhelpful, is the recounting (pp. 14–16) of the fabulous mechanical record of Boeing’s twin-engined 777 jetliner. But as there are no single-engined jetliners, it’s hard to say where he’s going with this point. There’s also an expression of concern about bird strikes on “the F-35, which will be flown fast and close to the ground” (p. 19). As the concept of operations for the F-35 generally calls for high-altitude operations, this seems truly no more important than for any other aircraft.

There are also a few red herrings. The background to the argument is set by Byers’ recounting the very high loss rates amongst the RCAF’s F-104 Starfighters. This is actually misleading. That airplane’s J79 engine made its first run in 1955. If we’re going to discuss the reliability of a 59 year-old design, we might as well discuss loss rates amongst the Royal Flying Corps’ Sopwith Camels. The joke about the early nickname for the single-engined F-16—the Lawn Dart—remains entertaining, if a bit macabre. But it’s hardly analytical.

The core of the argument is found in two charts from the US Air Force Safety Center, comparing Class A engine-related flight mishap (ERFM) rates for two sets of USAF jet fighters—single and twin-engined—with particular engine types. (Class A mishaps are those involving the loss of either the plane or a crew member.) Have a look—the charts appear to confirm that twin-engined fighters have long had, and still have, lower engine-related loss rates than single-engined fighters, at least in US service. But the summary statistics cited are not so cleanly interpreted.

Consider how Byers concedes that the F-16 with Pratt & Whitney’s F100-229 engine has never had a Class A mishap due to engine failure. He admits the same about Saab’s JAS39 Gripen, which has had “not one engine-related crash” in over 120,000 flight hours since 1997. But focusing on the F-16, he asserts that this “can be at least partly explained by the late-production version having accumulated just 327,587 EFH” (engine flight hours), a third to a tenth that of earlier models. He appears to be saying that a shorter operating record increases the likelihood of a lucky streak. 

Blaming good luck seems more than plausible, but is there a reasonably direct comparison to make? If we throw out the ancient examples, and stick to aircraft-and-engine combinations from the past 30 years, yes. Using the same sets of summary statistics from the USAF, we can look at the same series of engines aboard two relatively contemporaneous aircraft, the twin-engined F-15 and the single-engined F-16, at least for the models on which the USAF has supplied enough information:

Aircraft and engine # of engines year first flown ERFMs per 100,000 EFH
Total EFH
F-16 with F110-100 1 1984 1.12 3,573,187 40
F-16 with F100-220 1 1986 1.02 2,251,895 23
F-15 with F100-220 2 1986 0.24 3,713,111 9
F-16 with F100-229 1 1989 0.00 327,587 0
F-15 with F100-229 2 1989 0.50 1,005,782 5
F-16 with F110-129 1 1992 0.91 1,095,298 10
Overall for F-15s 2   0.30 4,718,893
Overall for F-16s 1   1.01 7,247,967

Taking this difference as the estimate, what would be the effect for Canada? If the planned fleet of 65 CF-35As will have an expected average operating life of 8,000 hours per plane, the RCAF will be getting 520,000 jet fighter flight hours. With the comparative loss rates of F-15s and F-16s—a much more easily defended comparison than anything involving the F-104—the RCAF could anticipate over that time 1.56 serious mishaps with a twin-engined fighter, versus 5.25 with a single-engined fighter. That is, not “one dead pilot”, but an extra 3.69 pilots who may or may not be able to eject.

All things being equal, that would decide the matter, no? But as the saying sometimes continues, all things are never equal. A fighter with one engine of a certain type is almost certainly less expensive to procure and operate than a fighter with two of that type, and safety is not a good for which anyone has an infinite willingness to pay. If there are other reasons to procure the F-35A, is the expectation of a few extra lost aircraft—and possibly lost pilots—worth the difference?

Fairly, even this isn’t the right comparison to make. This approach arguably handicaps the single-engined concept, as it does not account for engine reliability improvements in combinations like the Gripen with the Volvo/GE F404, the Super Hornet with the GE F414, or the Typhoon with the Eurojet EJ200. Indeed, as noted, the JAS39 is jet to suffer an engine-related crash. That could be luck, or it could be exquisitely good design and manufacturing. The question really should not turn on whether two engines are theoretically better than one, but whether one or two engines in whatever plane might Canada want is actually better than the one Pratt & Whitney F135 in the F-35. Thats the analysis Canada needs, and like all things with jet fighters, it takes a lot of work.

James Hasik is a senior fellow at the Brent Scowcroft Center on International Security.