December 1, 1995
By Bruce Landsberg
The world's most popular airplane, not surprisingly, has a great safety record. Safety and simplicity sell. In its latest safety review, the AOPA Air Safety Foundation looked at all the Cessna 172 accidents that occurred from 1982 through 1988 — more than 1,600 of them. With 24,130 Skyhawks in the fleet, that's a good record, but it is sobering to think that every year about 237 Skyhawks are involved in reportable accidents — that's more than four per week. Happily, most of the accidents result in little or no injury to the occupants.
The Cessna was compared to other light four-place aircraft that make up the bulk of the training and entry-level transportation fleet. Included in the comparative aircraft group were the Beech Musketeer series, the fixed-gear Cessna Cardinal, the Piper Cherokee, the Gulfstream American AA-5 Traveler, and the Aerospatiale Tobago.
In terms of overall accidents per 100 aircraft in the fleet and per 100,000 hours of flight, the 172 had a very slight edge over the comparative aircraft. But there are some significant differences in other areas. The Skyhawk has fewer serious accidents, which may be attributed to its almost universal use as a trainer. Instructional flying is proportionately much safer than personal flying. Pilots are less prone to fall victim to the high-risk accident areas when under an instructor's supervision.
The 172 is involved in accidents in instrument meteorological conditions (IMC) about half as often as other light singles. This is not because of any inherent differences in the stability of the various aircraft, but probably in how they are used. The Gulfstream Traveler and Beech Musketeer are not used widely by flight schools. Individual owners are more likely to use these aircraft in cross-country flight with more chances to encounter adverse weather.
The same thinking applies to the 172s' having lower accident involvement on IFR flight plans and at night. As with many of the other aircraft we have studied, night flying shows a high degree of risk relative to the hours actually spent aloft after dark. Night accident rates are estimated for the Skyhawk at 7.65 per 100,000 hours, compared to its 6.17 overall accident rate.
In keeping with the role of a training aircraft, the primary accident cause about 85 percent of the time is the pilot, just slightly more than the 82.9 percent of the comparison group. The simplicity of the 172 also shows up, with the aircraft being identified as the problem source less than 7 percent of the time. There's not much to fail on a 172 if one maintains it properly.
When studying the pilots of accident flights, some interesting patterns emerge. Sixteen percent of the serious accidents occur in the pilot's first 100 hours of total time. The rate jumps to 23 percent for the next 100 hours and then drops sharply after that. This indicates that as new pilots begin to enjoy the freedom of their certificates, they also encounter some situations that exceed their experience level or defy good judgment.
For example, a 23-year-old private pilot with 164 hours total time was observed performing terrain-following flight at altitudes ranging from 50 to 300 feet. A collision with electrical transmission lines 100 feet above the ground ended the joyride.
A 19-year-old private pilot with 71 hours total time and only seven in the 172 took off with three passengers from El Paso, Texas. The density altitude was calculated to be 6,400 feet when the pilot was asked by ATC to make a turn just after liftoff to make way for a departing jet. The overloaded Cessna had climbed to about 300 feet when, after entering the turn, it was observed to nose over and lose about half its altitude. A witness stated that the aircraft climbed and dipped two more times before crashing in a steep bank into the desert. No pre-impact malfunction was noted.
A question that always comes up after an accident of this type is whether the pilot has ever had a full-load checkout. The 172 has four seats; but unless the fuel load is light, the odds are that the aircraft will be overloaded when the seats are filled — unless you're carrying munchkins. Climb performance is anemic at sea level under this load condition, let alone at high density altitudes. Stalls tend to occur more easily and the recovery takes longer.
Half the pilots involved in serious accidents in both the Cessna and comparison aircraft had fewer than 100 hours in type. This is not unique to light training aircraft and indicates that pilots are attempting operations beyond the skill level to which they were trained. Either the pilots should restrict their activities until they have more time in various conditions or the checkouts need to be more rigorous. A combination of the two is the most desirable solution.
Of the 107 accidents occurring in IMC, almost three quarters involved non-instrument-rated pilots. In perusing some of the briefs, located in the second section of the review, it may be stretching credibility slightly to refer to these crashes as "accidents." One scenario involved a 184-hour private pilot with three passengers on board who departed on a night cross-country. The flight encountered rain and low clouds, and the pilot attempted to file an IFR flight plan and follow radar vectors. The pilot informed the controller that he had only 35 minutes of fuel remaining. The impending exhaustion became a moot point after the pilot became spatially disoriented and spiraled into the ground.
Not surprisingly, the 172 had about one third the number of fuel starvation accidents, compared to the other airplanes, all of which require tank switching. Fuel exhaustion and weather-related accident rates were also significantly lower in the 172, again probably related to heavy instructional use, compared to personal use.
A few operations stand out as moderately risky. Takeoffs and landings during high winds resulted in many damaged aircraft but not many injuries. Many low-time pilots do not get enough instruction in the fine art of high-wind flying, with predictable results.
Go-arounds are another area where problems occur. The Cessna is blessed with exceptionally effective flaps. This characteristic allows for short landings but also mandates that the pilot retract the flaps to no more than 20 degrees on a missed approach. In an attempt to reduce this problem, Cessna reduced the maximum deflection from 40 degrees to 30 degrees on later models. The accident data used to compile this safety report do not specify year of manufacture.
As with many other single-engine, fixed-gear aircraft, maneuvering was the leading phase of flight for serious 172 accidents. Most of these mishaps involved low-level flight interrupted by terrain, obstacles, or water. While flying close to the ground may give a great sensation of speed, the sudden stop that frequently ensues is usually lethal.
Included in the review is a complete training syllabus for pilots and flight instructors that covers ground orientation, general flight operations, IFR operations, and cross-country flight. There is also a quiz to test your basic knowledge of the aircraft systems and performance.
The Cessna 172 is probably as docile and easy to fly as an aircraft can be. It's a simple airplane, with simple systems and simple procedures. If pilots maintain a modicum of skill and avoid the big judgment errors, the 172 is about as safe as they come.
The Cessna 172 Safety Review is available through Sporty's Pilot Shop for $22.95 by calling 800/SPORTYS.
See also the index of "Safety Pilot" articles, organized by subject. Bruce Landsberg is executive director of the AOPA Air Safety Foundation.
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