Naval Air: The Melting Deck Problem


May 7, 2009: The U.S. Marine Corps has admitted that it sent its new MV-22 into combat too soon. The marines began using the MV-22 in Iraq in late 2007, and were satisfied with how the aircraft performed, but had problems getting enough spare parts to keep up with those that were wearing out. There were unexpected problems were engine durability. That's a common problem in the "sand box." Every other vehicle that uses a gas turbine engine in Iraq (from M-1 tanks to C-17 jet transports) reported increased wear on their engines because of the copious and continuous dust and sand in Iraq.

Another problem was that even frequent inspections won't always catch an engine that's about to die from too much dust and sand. Several MV-22s in western Iraq (Anbar province, where marine MV-22s were operating) experienced engine failures. There were no crashes, but there were emergency landings (followed by quick engine changes so the $70 million, 20 ton aircraft could get home under its own power). The Rolls Royce T-406 engines weigh about a ton each, and put out 6,000 horsepower. Marine maintenance crews are trained to put a spare engine inside a V-22, along with needed tools, fly out to where another V-22 has made an emergency landing, do the engine change quickly, and get back to base in one piece.

If the marines had gone "by the book", they would have waited another year, and had MV-22s fly more training missions in desert areas similar to those found in Iraq. That would have revealed some of the dust and sand problems with the engine. However, the marines are also aware that different desert areas often have very different types of sand. The stuff in Iraq is very fine, and this is not as troublesome as the grittier stuff found in North American deserts. In any event, the marines wanted to get their MV-22s into action as soon as possible, in order to discover and fix additional problems, and make sure Congress was suitably impressed to keep supplying money to build more.

The MV-22s sent to Iraq moved there by ship. They could have flown themselves, but that would have meant organizing aerial tankers, and dealing with possible icing problems over the North Atlantic. Plus it would have put more wear and tear on the aircraft. It was only recently that the marines based an MV-22 squadron on an amphibious ship, instead of just using these vessels as aircraft transports. VMM-263 recently shipped out, with ten MV-22s, on the 41,000 ton LHD USS Bataan. Shipping out with the USS Bataan will expose the aircraft to more saltwater (which, so far, has not been a problem), and ample opportunity to operate over water. The Bataan also has CH-53E, AH-1Z and UH-1N helicopters on board, plus some AV-8B jets.   One new problem was discovered. The heat from the MV-22's gas turbine engines, which blow their exhaust right on to  the deck of the LHD while waiting to take off, caused high enough temperatures to the steel under the deck plates, to possibly warp the understructure. This was already a known potential problem with the new F-35B. So now the navy has two hot new aircraft that require an innovative solution to the melting deck problem. 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 MV-22s used by the marines can carry 24 troops 700 kilometers (vertical take-off on a ship, level flight, landing, and return) at 390 kilometers an hour. The V-22 is replacing the CH-46E helicopter, which can carry 12 troops 350 kilometers at a speed of 135 kilometers an hour. The V-22 can carry a 10,000-pound external sling load 135 kilometers, while the CH-46E can carry 3,000 pounds only 90 kilometers.





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