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Michael Byers holds the Canada Research Chair in Global Politics and International Law at the University of British Columbia.

The F-35 and its powerful single engine were supposed to be the highlight of this week's Farnborough International Airshow, the world's coming-out party for new models of aircraft. Instead, the aprons at this executive airport near London are occupied by the F-35's twin-engine competitors, all of them proven and ready to fly.

The F-35 is absent because an engine broke apart and caught fire during the takeoff phase of a training flight in Florida last month. The entire fleet of 100 aircraft – which are still under development and used for testing and training only – was grounded while Pratt & Whitney, the engine maker, scrambled to identify the specific problem.

Sadly, the general problem with the F-35's engine is well known and impossible to fix.

Two decades ago, the U.S. government decided to develop an aircraft that could serve the Marines, Air Force and Navy – in three different versions built around a common airframe.

The needs of the Marines included a short takeoff and vertical landing capability, and therefore a centrally located lift fan, which could be provided only through a single-engine design and a wider-than-normal fuselage.

The single engine has to produce more total thrust than both engines on competitor twin-engine jets, which are more aerodynamic than the F-35. Generating all that thrust produces an enormous amount of heat, to the extent that the exhaust from an F-35 can melt asphalt runways. It also exposes the internal components of the engine to extraordinarily high temperatures and pressures, creating a situation where the slightest manufacturing fault can cause catastrophic failure.

Quality control was a concern even before last month's engine fire. Last year, the F-35 fleet was grounded due to a cracked turbine blade. In April, General Christopher Bogdan, the head of the program, told the U.S. Congress that "far too often, engine deliveries are interrupted by technical issues and manufacturing quality escapes resulting in product holds and material deficiencies that increase overall risk to meeting future production goals."

In early June, before the engine fire, the F-35 fleet was grounded briefly due to an in-flight oil leak that was serious enough for the pilot to declare an emergency.

The fire itself is now being attributed to a cracked turbine blade, which fractured after excessive rubbing against a stationary element inside the engine caused it to grow even hotter than usual.

Although the U.S. military says the problem was confined to just one plane, it is not yet prepared to risk flying F-35s over the North Atlantic, where an engine failure would result in the loss of a plane and necessitate the rescue of an ejected pilot. This is why the aircraft is not at Farnborough.

The message to Canadians couldn't be clearer. Back in 1980, Canada chose the F-18 over the F-16 because of the protection that a second engine provides to pilots over an ocean or in the Arctic.

As General Paul Manson, the head of the procurement team, said at the time: "If you have a flameout while on patrol with the F-18, at least you can be sure of getting home on the other engine."

Unfortunately, the Harper government seems blind to the problem. In 2010, then-defence minister Peter MacKay was asked whether he was concerned about buying a jet with just one engine, which could fail and force pilots to eject. He replied in just two words: "It won't."

Two years later, Auditor-General Michael Ferguson criticized the government for failing to "exercise due diligence in managing the process to replace the CF-18 jets." The government responded by suspending its F-35 procurement and ordering an "options analysis" to compare the F-35 to alternative aircraft. Significantly, all of the alternative aircraft considered have twin engines.

The options analysis was completed earlier this year, but has not been made public. It may or may not address the single-engine issue.

Either way, the F-35's absence from the Farnborough Air Show should alarm anyone who is concerned about the safety of Canada's military aviators. As one former CF-18 pilot told FrontLine Defence magazine in 2011: "A single engine is stupid. There's no backup. If it fails, you're dead."

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