A look at the MU-2's Reputation

 - September 15, 2006, 8:44 AM

In his review of the MU-2 accident data, Greg Feith, a former NTSB investigator and aircraft safety consultant, tried to validate or dispel the following perceptions about the MU-2.

• Spoilers kill lift. The perception is that the spoilers used to roll the MU-2 (it has no ailerons) kill lift to a greater degree than ailerons. The spoilers are three inches high, Feith said. “You’re not killing lift; you’re reducing the efficiency of the wing. That’s it.”

• The MU-2 has high wing loading. The MU-2 wing loading in takeoff and landing configuration is lower than that of the King Air 350. In clean configuration, MU-2 wing loading is within 10 pounds per square foot of King Air 200 wing loading.

• The airplane has more single-engine climb performance. A Prop video showed tests of MU-2 single-engine climb performance using spoilers for roll control without rudder input, then with rudder input. The difference was noticeable. Without rudder input, using spoilers, the descent rate was 700 to 800 feet per minute. Once the pilot stepped on the rudder, which negated the need for spoilers and the drag they cause, the MU-2 climbed at 500 feet per minute.

• The landing gear causes a large drag penalty during retraction, which is detrimental if an engine fails on takeoff. More videotaped tests showed what happens as the gear retracts on an MU-2. Gear retraction on an MU-2 takes 15 to 17 seconds, but the period during which the gear causes a drag penalty is only six seconds, as the gear doors open and close. With the gear down and one engine out, the MU-2 descends at 50 fpm, but with the gear up, it climbs at 300 feet per minute. “The airplane does not come screaming out of the sky [during engine failure],” Feith said. MHIA recommends retracting the gear right away instead of waiting until reaching 400 feet, as some suggest.

• The MU-2 has a high roll rate. Spoilers do help increase roll rate, but in the MU-2 this shows up only at cruise speeds, where the roll rate is about a third higher than that of a King Air. At approach speeds, their roll rates are nearly the same. Feith flew the MU-2 into full stalls and was able to roll 20 degrees each way while in the stall. “This airplane does not stop flying at 100 knots,” he said. “The fact is, it didn’t do anything dramatic.”

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