February 1994 Volume 37 / Number 2
Bonanza Safety Review
The Beech Bonanza ranks as one of the most popular aircraft ever built, so it was with great interest that the AOPA Air Safety Foundation tackled the safety record of this perennial favorite to see how it has performed in that arena. This is the third safety review the foundation has done (the first two reviews were of the Cessna P210 and 182). This latest analysis included the V-tail Bonanzas, the BE33 Debonair/F33 Bonanza, and the BE36 models.
The Bonanzas were compared to the Cessna 182RG, Cessna Centurion, Mooney M20, Piper Comanche, Piper Cherokee Six/Lance/Saratoga PA-32R, and the Rockwell Commander 112 and 114. Because we felt that there might be some differences between the V-tail and straight-tail versions, they were analyzed separately. Five hundred twenty-three Bonanza accidents occurring between 1982 and 1989 were compared to 1,419 accidents of other aircraft.
As has been the case with all the other aircraft we have reviewed thus far, Bonanza pilots have been their own worst enemies. The V-tail pilots were responsible for about 73 percent (248 accidents) of accidents, and the straight-tail pilots weighed in at a whopping 83 percent (154 accidents). Aircraft-related causal factors contributed about 15 and 11 percent, respectively. Compared to other aircraft in this study, Bonanzas have a lower overall accident rate — and that speaks well of this high-performance single.
Looking at accidents that occurred in instrument meteorological conditions, the overall rate for the Bonanzas was slightly better than the comparison aircraft. Not surprisingly, it was much safer if Bonanza pilots were instrument rated and on an IFR plan.
A substantial number of the VFR V-tail pilots involved in accidents came to grief in mountainous terrain in IMC, and all the IMC accidents involved serious or fatal injury. The following scenario was typical:
A 400-hour non-instrument-rated pilot received a weather briefing that predicted an 8,000-foot overcast, rain, and mountain obscuration for the following day. The flight departed Corona, California, enroute to Carson City, Nevada, the next morning, apparently without the pilot obtaining an updated briefing.
The wreckage was found in a box canyon at an elevation of 6,200 feet msl. A witness at the bottom of the canyon (4,000 feet msl) reported the visibility as 100 feet in fog and rain at the time of the accident. Weather conditions were worse than forecasted the day before, with the destination airport reporting a quarter-mile in snow. However, weather on the day of the accident was accurately reported in information that was available, had the pilot asked for it.
The profile was different for the BE33/36 in that almost three quarters of the IMC accidents involved instrument-rated pilots on IFR flight plans. This still left about 25 percent of the accidents due to VFR pilots continuing into IMC.
Airframe icing was involved in about 20 percent of the cases. A typical encounter involved a 600-hour instrument-rated pilot who ignored several pireps on moderate to severe icing in freezing rain and in the clouds. At the destination, which was reporting 500 overcast and 2.5 miles in freezing rain, the pilot made a circling approach but crashed when the left wing stalled during a turn toward the runway.
Thunderstorm accidents claimed four straight-tail Bonanzas. It is interesting to note that in our database, there were no BE36 accidents after 1986 involving convective weather. One can speculate that better weather avoidance gear, such as radar and lightning detection equipment, made a difference, or it may be that BE36 pilots took the warnings about thunderstorms to heart. It's hard to know precisely.
V-tail and straight-tail Bonanzas had an identical accident record after dark. The study showed night flying to be riskier than during the day, even when flying IFR in IMC. Incidentally, this same pattern applies to the P210, 182, and PA-28 series (the Cherokee analysis will be released in the spring). Both VFR and instrument-rated pilots had more accidents at night relative to the number of hours flown. It's an area where we don't get much practice. If night flight is in your plans and you're not proficient at it, it is strongly suggested that you get some dual instruction and be extra cautious about the weather conditions.
The leading factor in Bonanza IFR/IMC accidents was improper procedure during instrument approaches. Nothing in the accident profiles suggests an inherent fault or flaw in the aircraft that would contribute to difficulty in flying instrument approaches. Descent below minimums or failure to follow the procedural track almost guarantees an audience with St. Peter. This is a clean mandate for a higher level of training and proficiency in this critical area.
The V-tail Bonanza came under close scrutiny in the mid-1980s following a series of in-flight breakups. Several airworthiness directives were issued and a special study was done by the FAA and the Department of Transportation, which resulted in a stabilizer reinforcement kit at the root of the V-tail. After the installation of the kit, the in-flight breakups decreased dramatically.
It should be noted that the V-tail Bonanza's center-of-gravity envelope is relatively narrow, and loss of control with aft CG in IMC conditions could be contributing factors in several of these accidents. Additionally, the balancing of the tail control surfaces is critical to avoid aerodynamic flutter. Unbalanced control surfaces continue to cause problems, so it is essential, after the aircraft is painted or work done on the tail, to check that the surfaces are exactly in tolerance.
One area where the Bonanza does not shine is in the nonstandard placement of the landing gear switch, which is on the right side of the throttle quadrant. This has led to a significant number of gear retractions when the pilot really intended to raise the flaps. This design quirk was rectified in 1984 for the A36 and B36TC aircraft when the gear switch was moved to the left side of the throttle. Additional squat switches and a throttle position switch have been added to all late-model Bonanzas to help prevent that low-down feeling. A squat switch is designed to prevent gear retraction when the weight of the aircraft is on the landing gear. As many Bonanza owners have discovered, a single squat switch doesn't always work. Adding to the belt-and-suspenders approach, the throttle position switch prevents gear retraction at reduced power settings.
The gear-up landing accident record on the nonstandard versions, however, is about 40 percent higher than for the comparison aircraft. I expect to receive at least a few letters extolling the virtues of the old arrangement and the importance of pilot familiarization. Human beings do make mistakes, and when the statistics indicate that there is a problem that can easily be fixed with human-factors engineering, it should be done.
I fly both versions of the Bonanza — non-standard and standard gear and flap switch position — and have given my passengers strict orders to break my arm if there is an attempt to reach for any switches during the landing roll. It's a procedure that serves well in all aircraft.
In summary, the review contains a statistical analysis of BE35 and BE33/36 aircraft, with a generous selection of briefs of various categories of accidents. Additionally, there is a recommended training syllabus to guide pilots and instructors through a thorough transition or refresher program. It addresses the problems identified in the first two parts of the book. Finally, there is a selection of Bonanza articles from AOPA Pilot, dating from the present back to the early 1980s. You won't want to look at the purchase prices back then (they were low compared to today) unless you bought one.
See also the index of "Safety Pilot" articles, organized by subject. Bruce Landsberg is executive director of the AOPA Air Safety Foundation.