Embry Riddle Aeronautical University
Aircraft Crash Survival Analysis and Design
The Cessna 172 has been a reliably made airplane since the 1950's and it continues to hold its reputation in today's environment. This paper discusses the Cessna 172 and some of the specific safety features concerning the aircraft. This paper mentions some similar aircrafts with similar flight characteristics and as well some methods for possible success. It also states in detail some of NRI flying club's experiences as well as some of Airworthiness Directives put out by Cessna. Over all this is a reliably safe airplane for students, instructors, and old time pilots to enjoy and fly.
The first fatal airplane crash was in 1908, a wreck which killed one passenger, that passenger was Orville Wright. Aviation safety has come a long way since then.
"In fact, the odds of dying on a commercial airline flight are as low as 11 million to 1! That said, a lot can go wrong at 33,000 feet above the ground, and if you're unlucky enough to be aboard when something does, the decisions you make could mean the difference between life and death.
Keep in mind that about 90% of airplane crashes have survivors, so even if the worst does happen, your odds aren't as bad as you might think" (wikihow.com).
A typical Cessna 172 is a four-seat, single engine, tricycle gear, high wing airplane. More Cessna 172s have been built than any other Western aircraft. It is also probably the most popular flight training aircraft in the world. "The Cessna 172 is without doubt the most successful mass produced light aircraft in history. The first production models were delivered in 1956 and it is still in production in 2007; more than 35,000 have been built" (wikipedia.com).
C-172 has best G.A. fatal accident record at .56 per 100,000 flight hours. This figures out to one accident for every 18,000 hours of C-172 flight. Using the figure that the average serious injury/fatal accident occurs in only one of every six accidents, we find that an injury accident will occur 110, 000 hours of flight time. Not long ago I saw four people get into the C-172. I questioned the pilot regarding weight and he said that he was in limits. When the heavyweight of the group got into the back seat, I again approached the pilot and suggested that balance might be a problem. What can be done? First, I don't believe anyone deliberately and knowingly damages an aircraft or exposes passengers to danger. A pilot may have erroneous perceptions as to what makes a good landing. Maybe, there is a problem with knowing aircraft attitudes. Is establishing a stabilized approach at a constant airspeed the problem? Very possibly, it is caused by a situation beyond the pilot's experience. Instructional flying is five times safer than other G.A. flying. Since so much instruction is done in the C-172 it is logical to expect that the C-172 has an excellent safety record when compared to complex-high-performance aircraft. A single pilot in a C-172 with his seat well forward; the C-172 with a full radio stack; and the aircraft is within C.G. limits presents a potential flying control problem. A final approach at 60 knots will give the elevators enough authority to round out. As the aircraft decelerates below 60 knots the elevator loses authority and may well be unable to raise the nose, even if full back and up. This is especially true if the power has been taken off. Under these conditions, what should the pilot do? If you can't arrange to get one passenger in the back seat, you should plan to leave at least 1200 rpm. The power will help hold the nose up and give the elevator the authority required for a full stall landing. Very careful energy management will be required to avoid a balloon. It can be done to a full stall landing every time. You will not be able to see the runway. The nose wheel will remain well clear of the ground. Power can be applied for the takeoff and the flaps removed without the nose wheel ever touching the ground. Alternatively, the power can be taken off as the nose wheel touches. Aircraft damage due to landings is mostly accumulative. Occasionally damage happens all at once but usually it is accumulative. The gearbox can take thousands of average landings without any damage. The spring gear can take a heck of a beating. The severe damage to Cessna's is to the gearbox underneath the seats. One falling out of the sky from 20' can break the box. Repair or replacement of a C-172 gearbox can cost $9,000. The nose gear is attached to the firewall. A very hard landing on the nose wheel can damage the firewall. Flying an aircraft with a bent firewall is enough to trigger an FAA investigation. Try to inspect the firewall of a C-172 or C-182 without removing the cowling. Is the nose wheel fork bent? Inadequate preflight the FAA calls it. Many differences have been made to the C-172 from 1955 to 1986. 36,000 C-172s have been manufactured since the first one in June of 1955. The C-172 has the best safety record of aircraft in its class. The 1956 model had a 145 hp Continental. The 1960 model had a swept tail. In 1963 a rear window appeared as well as single piece windshield and longer elevator. The 1956 to 60 C-172 had a low panel that allowed the pilot to 'look down' over the 145 H.P. engine. Over 30,000 C-172s have been built in 43 years. 1960-63 enter the swept tail and no-window fuselage. Enter the window in the back and then we have a series of changes in engine, landing gear, and cockpit but essential things remained the same. The 1964 model had electric flaps instead of the Johnson Bar. 1968 models switched to Lycoming 150 hp engines. In 1971 the spring steel gear was changed to tubular. In 1972 the dorsal fin was extended to correct pitch problems during slips. 1973 changed the wing leading edge to a droop as well as a shorter propeller. An engine change in 1972 was a disaster due to inadequate lubrication. 1978 saw the 24-volt electrical system and better seats. 1981 gave a 160-hp engine and gross weight of 2400lbs but reduced flap travel of 30 degrees. 1986 changed the angle of the horizontal stabilizer to improve pitch authority. Popular modifications include such things as 180 hp engines and possibly constant speed props. Sound reduction through use of thicker windshield, long range tanks and electronic upgrades are common. The large slotted flaps in older Cessna's can a nose down pitch in forward slips. A cautionary warning is in many POH's indicating that slips should be avoided when using maximum flaps. The pitching motion is the result of the difference between a strong wing downwash over the tail in straight flight to a reduced downwash influenced by a raised aileron in slipping flight. This restriction does not apply to the wing-low drift correction used in crosswind landings.
"Over sixteen C-172s are involved in accidents every month", say's (whittsflying.com). That's about one accident every two days. This gives a rate per 100,000 flight hours of 1.46. Prior to 1977 the C-172 "engine failure rate was one per every 5.6 million hours of operation", whittsflying.com. Only one in six of these accidents result in personal injury. Night accidents in C-172 occur at nearly a 20% higher rate than day accidents. The NRI flying club states the following, "85% of all C-172 accidents are due to pilot error. This is more accidents than in other types. The aircraft has been deemed responsible in 7% of the accidents. The percentage of C-172 accidents is highest when the pilot involved has between 100 and 200 hours of flight time. 50% of the accidents occurred when the pilot had less than 50 hours in the C-172 type aircraft. A high percentage of C-172 accidents have been attributed to inadequate checkouts. C-172s have twice as many hard landings as a PA-28 (Cherokee) per aircraft. The C-172 is four times as likely to have a wind related accident. It has twice as many go-around accidents. NRI Flying Club has spent no less than $4,500.00 in the last two years on just nose-strut repair and nose gear rebuilding of one of their Cessna's," (http://www.nriflyingclub.com). This is certainly indicative of a problem in piloting, checkouts, and instruction. Making flat landings or nose wheel first touchdowns first could indicate the problem. Significant fuel imbalance has been explained away as due to overflow venting pipes being pressurized by air in flight. However, it has been found to be due to fuel tank sealant obstructing fuel tank vent lines as well. See Cessna service bulletin SEB 99-18. The C-172 has half as many fuel exhaustion accidents as like powered low-wing aircraft. Other facts stated by the NRI flying club presented that, crosswind takeoff and landing accidents were relatively frequent and attributable to inadequate checkouts. The second major area of accident was the go-around, which has been partially corrected by Cessna by reducing flap extension to only 30 degrees on later models. Serious C-172 accidents were generally related to controlled flight into terrain or obstructions. (Low level flight) To fly the C-172 you must practice landing in different flap configurations and power settings. You must know how to hold the control for taxiing. The C-172 go-around requires anticipation and attention to the procedures for flap removal. It takes practice of the right kind to bring an improvement and a change in our maintenance costs. "Years ago the Club lost a C-172 because the pilot attempted to make a go-around without removing at least partial flaps" (nriflyingclub.com). Airworthiness Directives are less common to the C-172 than other aircraft. Check the security of the aileron counterbalance weights, seat tracks for locking, flaps for smoothness of jack screw, and the panel lighting rheostat and that's most of the AD's covered for the Cessna 172.
Spins are the least of the problem if you are looking at the relative safety of a type of airplane. Both the 152 and the 172 have a long list of airworthiness directives. Most of these directives were probably issued as a result of some fatal accidents. Yet these planes have a fatal accident rate per 100,000 hours that rivals that of airliners.
Of total accidents both fatal and nonfatal caused by a stall (including spins), the 172 has almost the best rate of any plane, with 0.77 accidents per 100,000 hours. The 150/152 is about twice that at 1.42; still very good when you consider that both these planes are used extensively as trainers. Considering the people who fly them, the 152 does very well indeed, as does the Tomahawk and other 2 seat trainers of the period. They were a tremendous improvement over the Cubs which had accident rates that were more than five times greater. All the planes that are better than the 172 are also Cessna's, except for the Bellanca 14-19 and the Piper PA-32. "The plane with the best record in stalls is the Cessna 182 at only 0.36 accidents caused by stalls per 100,000 hours, followed by the 195 at 0.47 and the 206 at 0.54. Compare this to the Aeronca 7's rate of 22.47 and a rate of around 5.0 for most Piper tail draggers"(whittsflying.com). Both the 150/152 and the 172 generally are near the top of the class in any category of accident, whether engine or airframe failure or bounced landing. The 172 probably has the best safety record of any general aviation plane ever built, but the 152 and the Piper PA-28 are not far behind. When these planes do have accidents their fatality rate is exceptionally low. The huge majority of accidents in these planes are simple fender bender types, with a good sprinkling of botched landings -- these planes are trainers after all. Many people believe that trainer aircraft such as the 152, the 172, the PA-28, the PA-38, etc., were made deliberately hard to fly in order to make better pilots. I would like to see some evidence of this. These planes are so easy to fly that they have made pilots of many people who would never have otherwise been able to fly. Until these planes were introduced only an elite few had the talent necessary to make the cut. They put flying in reach of everyone, and for awhile up through the 1970s it looked like aviation had reached a critical point where someday learning to be a pilot would be an expected skill of everyone, like driving a car. Many factors conspired to end that dream, and the number of pilots being produced today is only a fraction of what we once turned out. Our numbers are increasing, but it will probably be many years before we return to anything like those days.
Cessna 172, wikipedia website, 2007, viewed 2/27/2007, http://en.wikipedia.org/wiki/Cessna_172
Cessna service bulletin SEB 99-18, FAA website, 2007, viewed 2/27/2007, http://www.faa.gov/aircraft/safety/alerts/saib/media/CE-03-43.pdf
NRI Flying Club website, 2005, viewed 2/27/2007, http://www.nriflyingclub.com/defaultw.asp
Surviving Crashes website, 2007, viewed 2/27/2007, http://www.wikihow.com/Survive-a-Plane-Crash
Whittesflying website, 2006, viewed 2/27/2007, http://www.whittsflying.com/page5.64C-172_Techniques.htm