Air Safety Week: A Good Grounding in Grounding

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A Good Grounding in Grounding

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.

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."

AD 2006-13-15 (effective 11 Aug 06 - accomplish within 200 flight hrs or 12 months)

Detect and correct cracks, corrosion, fractures, and incorrect torque values in the wing attach barrel nuts, which could result in failure of the wing barrel nuts and/or associated wing attachment hardware. This failure could lead to in-flight separation of the outer wing from the center wing section and result in loss of controlled flight.

AD 2006-14-08 (21 Aug 06) - flight idle blade angles (thrust asymmetry)

AD 2006-15-07 (24 Aug 06) - improper rigging or adjustment of the propeller feathering linkage

AD 2006-17-05 (22 Sep 06) - improper adjustment of the flight idle fuel flow

AD 2006-17-01 (22 Sep 06) - uncalibrated eng torque indicators

If nothing else is accomplished, the attention focused on the issue means that pilots or firms purchasing MU-2s should be very much aware of the aircraft's unforgiving reputation. Moreover, the cumulative cost of implementing the current crop of palliative measures, including enhanced pilot training, are bound to prove a definite deterrent for those wishing to pick up a high performance cheapie.

In Aug. 2005, Rep. Tancredo's current letter was citing 187 MU-2 accidents since 1962, with 234 persons dying in 74 different fatal accidents. Compared to similar twin-turboprop aircraft introduced in the same era of the 1950s, the FAA says the MU-2B has an accident rate about twice as high and an overall fatality rate that is about two-and-a-half times as high. But when specifically compared to the accident rate of the Super King Air 200, another twin-turboprop of comparable size, in terms of accidents per 100,000 hours flown, the MU-2 accident rate over a 38 year period (1964-2002) is in fact five times higher than the King Air, and about seven times higher in terms of fatal accidents.

Twelve months ago, the FAA sent out a Flight Standards Letter, dated Sept. 30, 2005, exhorting MU-2 pilots and maintenance technicians to be aware of all the issues that had caused problems and were continuing to keep the type's accident rate high. The FAA letter also cited the alarming accident statistics for the previous 18 months. The letter concluded: "...the goal in this case is to identify the root cause, or causes, of MU-2 aircraft accidents and to identify interventions that will save lives."

Rep. Tancredo seems to have decided that the only intervention that will do that is not a good grounding for MU-2 pilots and mechs, but a permanent grounding of the aircraft. It's fair to say that few pilots flying the beast would be unaware of its daunting reputation, but equally of concern is the fact that many prospective passengers wouldn't be. That is the real issue.

Of course, the MU-2 has its advocates as well as its critics. However, between the two camps there are an increasing number of pragmatists who want to get across a constructive message of universal application. One suggestion: a basic requirement for any aircraft to be certified is that its flying characteristics allow it to be safely flown by an average pilot.

There's no point in religiously pointing the finger at pilot error if the error was in certifying the MU-2 in the first place. If you sawed 6 feet off each wing of a Cessna 172 and certified it, would it be fair to classify each subsequent accident as pilot error - notwithstanding that a few above average pilots manage to always "get by"?

For an aircraft to be safe, there must be forgiving latitude in both its handling and condition. MU-2 handling is an area where the scope for error is extremely limited, particularly in non-normal operation. That's not "safe", in any rational definition of the word.