NTSB General Aviation Safety Enquiry

Why so many light aircraft? Why so many lives lost? The NTSB research data supplied to AADR Quarterly pulls no punches; it lists makes, types, and makes guarded conclusions.

Here are some of the findings of those four years’ research: The most frequent accident listed and reported involved engine failure, followed by collisions with obstacles – and ground loops, hard landings, undershoots and overshoots.

The most significant fatal accident usually followed impact with either ground or water; stalls and on occasion, inflight airframe failure.

The engine failure section included, in addition to actual powerplant failures, fuel starvation and exhaustion, carburettor icing and induction system icing.

Perhaps understandably, the high accident group lists five older types – Luscombe 8, Cessna 195, Stinson 108, Globe GC-1 and Aeronca 11. Understandably again, these types feature tailwheels.

The five lowest accident rates (taking into account the numbers of each type flying plus annual flying times) are Beech 33, 35 and 36; Cessna 172; Cessna 150; Piper PA-28, the Mooney M-20.

In summary, and after interpolating the tables in our document, some startling facts come to light:

• Older model light aircraft with tailwheel configuration are prevalent in the high-accident group where collision with obstacles are featured, also the stall, stall-spin, stall-spiral and stall-mush initial manoeuvres leading to accidents.
• The high-rate accident group of light aircraft all had a weight-to-horsepower ratio of 16. 7, almost 30 per cent higher than the 13. 0 power loading of the low-rate accident group.
• A relationship thus clearly exists between increasing rate of stall accidents and decreasing rate of engine power-to weight figures.
• Ninety-seven of the 196 light aircraft logged as being involved in mid-air collisions were either Cessna 150s of Piper PA-28s largely due to their being used widely as trainers which spend much of their time in a circuit environment.
• As expected, ground loops were associated with older, tailwheel types. The Board which conducted this four-year study came up with some alarmingly stark facts; all data was fed into a computer and thus man-made errors during tabulation en route were eliminated.

A total of 185 light aircraft were selected for analysis after airframe failures in flight. Here are the main groupings: • Bellanca 14-19; 10 failures; mean rate 1. 49 per cent.

Beech 33, 35, 36; 40 failures, mean rate 0. 58 per cent.

Piper PA-24, 11 failures; mean rate 0. 42 per cent.

(Mean rate was assessed after correlating the number of hours flown by all aircraft of that type. ) Among the conclusions drawn by the Board was that all 40 in-flight airframe failures in the Beech category involved the V-tail Beech 35.

Among findings after lengthy expert and professional study of the data supplied, were:

• Aircraft with tailwheels figured in more than double the number of accidents using a mean rate, than tricycle aircraft.
• The mean accident rate for tail-draggers was especially high for ground loops, stalls and collision with obstacles.
• The mean fatal accident rate per 1000 hours of Cessnabuilt aircraft included in the study (1. 65) was significantly lower than the other five manufacturers still producing aircraft: Beech (2. 54); Bellanca (4. 84); Grumman (4. 13); Mooney (2. 50) and Piper (2. 48).
• The Bellanca 14-19, Beech 35 V-tail and Piper PA-24 accounted for about one-third of all in-flight airframe failures of the selected group of light aircraft.

Cessna 150s and Piper PA-28s accounted for nearly half the mid-air collisions involving the selected group of aircraft under study. Older model aircraft appear to be associated with many accidents involving stall accidents, especially if they’re tail-draggers, because of high power loading problems. What about pilot error? The Board findings indicate that pilots with one to 50 hours’ time are prone to be an accident statistic through ground looping, followed in prevalence by hard landings and engine failures.

For pilots with more than 500 hours, engine failures come first in the accident prevalence list, followed by collision with obstacles, then ground loops.

For pilots with between one and 25 hours of type, ground loops come first, with engine failures and hard landings second and third.

We publish some of the more significant tables in this admirable document – . and wish the Department of Transport would come up with something similar, even in a Ministerial annual report tabled in Parliament.