F-35 Joint Strike Fighter

KEN POLE

Jan 15, 2012

A common knock on the Lockheed Martin F-35 that the Royal Canadian Air Force wants for its next-generation fighter is that it has only one engine, albeit a robust one. The Pratt & Whitney F135-PW-100 turbofan in the conventional variant of the Joint Strike Fighter is a development of the F-119 engine that went into the F-22 Raptor stealth aircraft.

Pratt & Whitney engines generate all the thrust necessary.

Assembled in Middletown, Connecticut, and including parts from the Pratt & Whitney Canada subsidiary in Longeuil, Quebec, the beast generates a dry thrust of 28,000 pounds, enabling the aircraft to “supercruise” in sustained supersonic flight up to Mach 1.6 without afterburner. Firing up the Raptor generates 43,000 pounds of thrust.

But the fact that there is only one engine prompted one retired CF-18 Hornet pilot with thousands of hours in various types, to grumble that because the Joint Strike Fighter is an “all electric airplane,” engine loss guarantees a crash. However, Stephen O’Bryan, a U.S. Air Force veteran with extensive aircraft carrier experience through exchanges with the U.S. Marine Corps, begs to differ.

During a recent Lockheed Martin event attended by FrontLine, O’Bryan, now Vice-President of F-35 Program Integration and Business Development, was asked whether the aircraft’s control surfaces would still function in the event of an engine failure.

“Let’s be honest: it is a single-engine airplane,” he acknowledged. “You have two choices there: you’ve got to restart the engine or you have to glide it in … and that’s been done a number of times. So there’s enough power to do both.”

The key is that the F-35 features an Integrated Power Package (IPP), manufactured by Honeywell Aerospace. Part of the aircraft’s Power Thermal Management System, the IPP ((which is approximately 40 inches long (101 cm) and weighs approximately 220 pounds (100 kg)) is housed in a belly bay near the left vertical stabilizer. It provides electrical power and cooling to aircraft subsystems for main engine start and ground maintenance.

Comprised of a power turbine, cooling turbine, compressor, starter/generator, combustor, valves and heat exchangers, it also can provide emergency electrical power in the event of an in-flight emergency.

“I know there are concerns about single engines,” O’Bryan continued, “but I think we’ve kind of conquered all those fears.”

Improved engine reliability is the principal reason, he noted, recalling a time when all commercial airliners had to have four engines for transoceanic service. “We all don’t have a problem with two any more,” he said.

When it was mentioned that the single-engine scenario is significantly different, he pointed out key redundancies on the F-35, including two fuel pumps and two generators. Citing his F-18 experience, he then explained that when a fuel pump goes on a Hornet engine, the backup is the pump on the other engine. “You have those redundancies and they carry them around for the safety.”

O’Bryan said the major factor overall is the cost of having a second engine – and the associated maintenance and other issues. “Because of the capabilities of the engine and the thrust you get out of it, [having another engine] doesn’t really provide any operational advantage.”

He also noted that the U.S. had sold 4,500 F-16 Fighting Falcons – which were developed and initially manufactured by General Dynamics, which sold its aircraft business in 1993 to the Lockheed Corporation and which, in turn, merged six years later with Martin Marietta. Although the F-16 is a single-engine aircraft, he said it has a much lower accident rate than the twin-engine F-18.

The number of engines was “not a driver in the overall safety of a fighter airplane,” he said, adding that it was time to “move on” from that debate.

“The Navy, the Marine Corps, the Air Force – all are comfortable with single engines and the capabilities we have. It’s really the experience they have with single-engine airplanes and the reliability we’ve proved.”