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A Good Grounding in Grounding

Air Safety Week, Sept 18, 2006

A Political Windstorm Continues to Engulf the MU-2 "Widowmaker"

On Sept. 9, U.S. Rep. Tom Tancredo (R-CO) once again took up the cudgel on behalf of all those who have died in the MU-2 -- and all those destined to die aboard one -- by calling for the resignations of FAA Administrator Marion C. Blakey and her responsible deputy.

Tancredo's trigger was two loss-of-control crashes within the same week (N6569L on Sept. 1 and N171MA on Aug. 25), on top of the FAA's continuing reluctance to do anything tangible about the type's abysmal fatal accident record. The two crashes were apparently heavy weather related, typical of the MU-2 fatal accident genre and easy enough to just blame on the weather and pilot judgment.

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Tancredo seems to have a genuine gripe against the high performance Mitsubishi twin turboprop, as well as being well versed in his subject. Together with four other congressmen and a senator, he has been waging a war against the deadly record of the airplane for some years and has been successful, insofar as making the FAA carry out a recent in-depth Airplane Safety Evaluation of the MU- 2.

A much earlier Special Certification Review (SCR) in 1997, and another in 1983, had already examined the safe operation of the MU-2 and concluded that pilots operating the demanding airplane required a very high level of skill and currency, regular flight reviews and a comprehensive initial training program.

Unlike its regulatory counterpart in Canada, the FAA has so far resisted any mandated type rating for the MU-2. Canada enjoys a much lower accident rate for the type. Issues of Air Safety Week as far back as 2002 have analyzed and commented on the type's ever spottier record. However, to be fair, the record shows a melange of pilot error, maintenance error and aircraft idiosyncrasy.

Part of the problem has been the fact that as the aircraft's record accumulates ever greater blemishes, its ill-repute makes it easier to acquire at a cost incomparable to its high performance. Less charitable persons might say that the situation is akin to selling second-hand snub-nosed .38s to teenagers for a dollar a pop -- and mandating target practice.

Single pilot IFR operation in all-weathers and at night in a high performance turboprop is approaching the province of the accomplished fighter jock, but unfortunately without the sturdy mount or ejection seat. The MU-2 is not only high performance, it is also "different" (see ASW Oct. 24, 2005). Most MU-2 loss-of-control crashes exhibit an early shedding of airframe components. This probably doesn't suggest that it's underbuilt, just that it is a very aerodynamically slippery mount that can easily accelerate through its limits into overstress country.

The MU-2's problems seem to stem from a few known handling vices as well as some mechanical defects. The FAA's safety evaluation results were posted in mid 2006 and claimed to have "used a data-driven approach to analyze the design, operation, and maintenance of the MU-2B series airplanes in order to determine their safety." In other words, they pulled the accident stats and pored over those a good while, comparing them to other airplanes of a similar ilk. A major finding said: "Field reports indicate an unsafe condition of improper rigging and/or adjustment of the propeller feathering linkage. Service centers found the unsafe condition during inspections. An AD was issued to detect and correct improper rigging of the propeller feathering linkage that, if uncorrected, could result in degraded performance and poor handling qualities with consequent loss of control of the airplane."

In fact, South Dakota Governor George Michelson and seven others died in an April 19, 1993 crash that involved a prop hub separation that invaded the cabin. Propeller control problems are a common theme.

Another FAA finding, more or less common to many higher performance turboprops, was that the aircraft was very susceptible to high icing accumulation rates. Their NPRM proposed solutions included such unnecessary and expensive modifications as installing an icing detector.

As the AOPA pointed out, the very first indication of icing was always a buildup on the windshield wiper post in front of the pilot, prop spinner and tip-tank nose. Measures finally adopted included auto-ignition, a trim-in-motion alert, an automatic autopilot disconnect and a pneumatic de-ice monitor. These were all designed to prevent departure from controlled flight in icing conditions. In addition, mandatory "Icing Awareness Training" was required by AD 2003-22-07 "in order to decrease the incidence of icing-related accidents due to pilot error".

Whether or not those measures were effective is a fairly subjective call - in light of the continuing weather related crashes. Another highly relevant issue might be the following very recent AD 2006-13-15 issued as a result of the 2005 Review. Indeed, all the ADs below contain the "could result in" caveat of: "...with consequent loss of control of the airplane in certain situations."

Government Industry

A Good Grounding in Grounding

Air Safety Week, Sept 18, 2006

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