Helicopter Flight Information

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High Risk Areas of Operation for Helicopter Pilots

I recently finished a study of 205 accidents that occurred In a 12-month period beginning 11/1/02, and ending 11/3/03. The statistics are outlined below.

Injuries

Relative to the injuries, it must be understood this actually means. You can be sure, that in most cases there are some injuries however minor. Many people state that they are uninjured when in fact they should be examined. Most of these people will experience some amount of soreness for a period of time just from being violently shaken during the accident. In some rare cases, it is possible that there were no injuries at all. In some cases the injuries were ground personnel, and further, we have no way of knowing the actual number of persons involved, or if they were on the ground or in the aircraft.

Of the 205 accidents, 235 people reported no injuries, while 106 people reported injuries from minor to serious, and another 73 people were fatally injured. Of the 73 fatalities, 2 were ground crew, one of which was performing hot fueling operations, and came into contact with the main rotor. In another accident, an observer / ground crew was struck and killed by flying debris when the main rotor contacted a building during a landing.

Types of Operations

The types of operations were widely varied. 27 were instructional flights, and of those, 5 were with check pilots, or examiners. 20 accidents were during Agriculture part 137 operations. Another 8 were during off-shore (oil support) operations, and 5 were fire fighting operations. The remaining 145 accidents occurred during all types of commercial and personal operations.

Causes

In the majority of cases, the pilot simply failed to maintain control of the helicopter. 40 cases were of undermined loss of control, and most usually while landing or departing, this indicates poor technique, and usually low time pilots.

Surprisingly enough, 32 of the accidents were ultimately caused by engine failures. 15 of the accidents occurred during low altitude operations other than agriculture. 13 were rotor strikes with buildings, trees etc. 12 were VFR flight into IMC. 10 were a loss of tail rotor effectiveness (LTE). 9 were wire strikes.  Another 8 were tail rotor failures. 7 were a loss of rotor rpm. 5 were ground resonance. 2 were fuel exhaustion. 2 were undermined mechanical failures. 2 were during off-airport landings. 2 were conducted by non-rated pilots operating without instructor sign-offs, one of which resulted in a fatality. 1 was due to carburetor icing. 1 was a mast bumping accident. 1 was dynamic rollover.

Some were of uncommon causes such as; a broken tail boom attachment bolt (Enstrom), a broken drive belt (Robinson), Broken belt tensioner (hughes-schwiezer), Broken tail rotor control cable (Sikorsky S61).

In one case, a down force (downdraft) of winds were encountered, and in yet another case, a cable tangled on a skid during a deer netting operation which resulted in a loss of control.

Of the 8 tail rotor failures, 3 were caused by the long line becoming tangled in the tail rotor, while 2 were tail rotor breakups. 3 of the tail rotor failures were caused by foreign objects. In one case, the baggage door was left open, and a blanket became tangled in the tail rotor, in another a flashlight was left on the tail boom, and flew into the tail rotor during takeoff, and yet another was caused by a flight jacket that was left draped over the tail boom.

Of the 32 engine failures, twenty were turbine engines. Of the accident aircraft, 109 were turbine powered while 96 were piston powered. This would seem to indicate a higher number of turbine engine failures relative to piston engine failures overall. This is not likely, as there are probably far more turbine engine operations conducted overall than piston powered operations.

Model Specific Accidents

There were several accidents that were caused by the pilots failure to maintain rpm control in the Hughes-Schwiezer 269 helicopters, and at least 3 of those resulted in ground resonance.

There were 2 cases where a broken alternator belt took out the main rotor drive belts in the Robinson R22.

There were 2 cases of the engine over-running the clutch on the Bell 47.

There were 2 cases of tail rotor blade failures on the Augusta 109.

Unusual events

Actually all accidents are unusual. It is a matter of fact however that if you fly enough hours, sooner or later something will occur with you as the pilot.

In one case, a student (on his first solo) took his hand off of the collective with full rpm, and the collective suddenly popped up and the helicopter rolled over onto it side (dynamic rollover). This can occur in any helicopter any time the rpm is up. The pilot should NEVER remove his or her hands from any of the controls once rpm is up, and the altitude is lower than 300 feet AGL. I teach my students to land, and close the throttle completely if they need to remove the collective hand for some reason. It is never, never, never acceptable to remove the right hand from the cyclic once the rotor is turning. See this page.

A significant number of the accident flights were conducted by low time pilots/students, and that would indicate a level of incompetence not necessarily to the fault of the pilot or student. This incompetence comes from the lack of knowledge in most cases. 

There is another issue that is shown as well, and that is over-confidence. Some of these accidents were clearly caused by the pilots actions, or is that inaction? Take the rotor contact accidents; in 2 cases, the pilot was landing to close to a building. This cost 2 persons their lives, was this demonstration of over-confidence worth it? Will it be worth it in the future.

Ultimately all this means is that pilots should exercise caution at all times, especially when their time (experience) is low.

Aviation is safe. Compared to automobile accidents; 149 people are killed on American roads every single day, while in general aviation, we lose on average slightly greater than 1 person everyday.

Accident break-down by model

Robinson R22 - 36,  Bell 206 - 32, Bell 47 - 22, Hughes-Schweizer 269 - 20, Hughes 369 - 15, A-Star - 13, Enstrom - 9, Augusta 109 - 7, Sikorsky - 7, Other Eurocopter - 6, Robinson R44 - 6, Bell 407 - 6, Other Bell - 6, Rotorway - 5, Hughes 500 - 4,  Hiller - 4, Twin Star - 3, BO 105 and BK 117 - 2, Brantley - 2, Kaman - 1, MD - 1.

Notes: The above results show some interesting facts. There is no doubt that the Bell 206 is the most common commercial helicopter in the world. The Robinson R22 likewise is the most popular training helicopter in the world. The A-Star / Twin-Star is rapidly gaining popularity in the commercial market, and the Bell 47 is one of the most popular Agriculture spray helicopters.

Some of the statistics do seem out of balance however. The Augusta 109, and the Hughes 369 have a comparatively high accident rate. A large number of accidents in the 269 are due to ground resonance.

Follow the links below, and at the left for more information.

Weather

Continued VFR flight into IMC conditions remains one of the highest cause of accidents related to weather.

Rotor Strikes

As surprising as it may seem, rotor contact as a result of landing to close to buildings and other obstacles is more common than one might think.

Fuel Starvation

Many aircraft are run out of fuel resulting in fatalities completely unnecessarily.

Off-Airport Landings

Hazards and legal issues that arise as a result of off airport landings.

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Last modified: 01/19/08