Murphy's Law: Britain Confronts The F-35B Heat Demon

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July 5, 2014: Britain, aware of the exhaust heat problem with the new F-35B vertical take-off jet, is spending several million dollars to build three small special landing pads where the F-35B may land vertically without damaging the normal air strip used for conventional takeoffs and landings. The U.S. did not originally note this heat problem for prospective buyers but by 2008 it was obvious that the high heat means the F-35B can’t use its vertical landing capability in most places.

Britain is buying fourteen F-35Bs for use on its two new Queen Elizabeth class aircraft carriers. These two ships are still under construction and the Royal Navy expects that the flight decks of those ships will be suitably equipped to handle the F-35B exhaust. In the meantime there needs to be a land facility for training British F-35B pilots and that’s what these new heat resistant “landing pads” are for. 

The U.S. was embarrassed when it first discovered that the new MV-22 and F-35B created "heat management" problems. At first there was an effort to redesign the exhaust but that did not reduce the heat enough for the F-35B. It was still more than 920 degrees Celsius (over 1,700 Fahrenheit). That was enough to cause heat resistant concrete to spall (come apart in flakes) and the heat resistant portable matting the U.S. Navy developed did not always prevent spalling when installed over concrete. Moreover the special matting was expensive and time-consuming to install.

Since 2008 the U.S. Navy has been furiously working on a solution to the fact that the engine exhaust heat from the tilt-rotor MV-22 and the vertical takeoff F-35B's. The temperatures were too hot for the deck plates on some of the carriers these aircraft would operate from. The gas turbine engines of both aircraft, which blow their exhaust right on to the deck of the carrier while waiting to take off, caused high enough temperatures for the steel under the deck plates to possibly warp the understructure. The navy also discovered that the exhaust heat problem varied in intensity between different classes of helicopter carriers (each with a different deck design.) The navy sought a solution that would not require extensive modification of current carrier decks. This included a lot of decks, both the eleven large carriers, and the ten smaller LHAs and LHDs.

Back in 2010 the navy thought it had found a way to handle the heat. For the MV-22 the navy developed portable heat shield mats that the deck crew could drag into place under the exhausts of the MV-22s if these aircraft were expected to be sitting in one place for a while with the engines on. For the F-35B, the heat shield mats didn't work as well because the F-35B engines put out more heat. So the exhaust nozzle on the F-35B engine was redesigned, to spread the exhaust over a larger area, thus lowering the peak heat build up to the deck plates. This was to also help solve the problem of the F-35B turning asphalt surfaces to a liquid state. But the “nozzle mod” did not completely solve the problem

This turned into another multi-billion dollar "oops" moment as the melting deck problem was never brought up during the long development of either aircraft. Previously, the British designed Harrier was the only aircraft to put serious amounts of heat on the carrier deck, but not enough to do damage. But when you compare the Harrier engine with those on the V-22 and F-35B, you can easily see that there is a lot more heat coming out of the two more recent aircraft. Someone should have done the math before it became a real problem.

 

 


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