November 11, 2009
Feb. 1 - How safe is the V35 Bonanza? Since it was announced that a Beech V-tail Bonanza was going to be AOPA's 2001 Sweepstakes airplane, more than one member has written in suggesting that the Bonanza airframe, in particular the tail section, may not be structurally sound. Specific questions were raised about the integrity of the stabilator spars, with members suggesting that AOPA take special steps to not only install all available strengthening kits, but that taking steps to devise and install additional strengthening modifications might be appropriate.
It's understandable that members might be concerned with the tail structures of the V-tailed Bonanza series, since there is evidence that failure of the stabilator spars were determined to be the cause of some fatal accidents.
Since 1957, there have been four airworthiness directives that address the tail area. The first, AD 53-11-01, was superseded by AD 57-18-01. This AD required that, within 100 hours, and at every 100 hours after the initial inspection, that there be an inspection of the stabilizer front and rear spar attachment bulkheads for cracks, buckles, or distortion, and associated cracks or buckles in the fuselage skin in the area of the bulkheads. In addition, within 100 hours, and every time the ruddervators were repaired or painted, the ruddervators of certain Bonanzas and Super V aircraft had to be checked to insure the static balance was within certain limits.
In 1987, AD 87-20-02 was issued against all V-tail Bonanzas. According to the AD it was issued to, "minimize the possibility for in-flight failures due to inadequate strength of the V-tail, and/or adverse flight characteristics resulting from operation outside the aft limit of the center of gravity envelope." This AD required early Bonanzas (models up through the G35) to be placarded to limit V NE speeds to a maximum of 125 knots IAS; and all other models to be limited to 171 knot IAS. In addition, copies of pertinent AD notes were required to be inserted into the pilot's operating handbooks or aircraft flight manuals; and the airplanes were limited to normal category operation only (no utility category).
Owners were given 12 months to comply with improvements including reinforcement of the stabilizer spars, checking the ruddervator balance, again revising the POH/AFM, resetting nose down trim limits, and installing later diameter ruddervator trim cables for earlier models. In addition, within the next 12 months, owners were required to determine the accuracy of the airplane basic empty weight and balance information using one of three listed methods. Only after all the provisions of the AD were accomplished, could the restrictive V NE speed limitations be lifted.
In late 1994, another AD, 94-20-04, was issued directing attention toward the V-tails. This AD superseded both of the preceding AD notes, and was written to clarify, update and incorporate the actions of the two earlier AD notes into one. The requirement for repetitive 100-hour inspections for cracks on tail bulkheads 256.9 and 272 was expanded to include all V-tailed models. Except for that change, this AD merely combined the two older AD notes into one. This is the AD that is current on all V-tailed Bonanzas.
In an effort to determine the effectiveness of this program, a search of the NTSB's accident Web site was undertaken, and all fatal Beech 35 series accidents from January 1, 1994 until January 31, 2001 were reviewed. There were 62 accidents during that seven-year period. In contrast, during the preceding seven years, 1986 through the end of 1993, showed that there were 109 fatal accidents.
While there were three or four accidents that appear to been the result of in-flight breakup since the latest AD was issued, all of these accidents appear to be the result of continued flight into instrument conditions by noninstrument-rated pilots, or flight into areas of known thunderstorm activity. Much more common during the same period are accidents that seem to be the result of fuel mismanagement, overloading and loading aft of the approved CG range, scud running, and stall/spin accidents during go-around or low altitude maneuvering. The accident records can be viewed at www.ntsb.gov/aviation/Accident.htm.
The AOPA Air Safety Foundation completed a Safety Review on the Beechcraft Bonanza/Debonair series of airplane in 1994. This study reviewed accidents from 1982 through 1989. The report comes to the conclusion that V-tail in-flight breakups have decreased drastically since the incorporation of the modifications required by AD 87-20-02. The NTSB study mentioned earlier supports this conclusion. The V-tail Bonanza is strong and robust high-performance airplane that is safe when flown by proficient pilots. Copies of this report can be ordered from Sporty's Pilot Shop at 800/SPORTYS or see the Web site www.sportys.com.
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