Aviation Safety Letter 4-2003
This section contains reports on accidents and incidents involving recreational aircraft. The purpose of these reports is to inform you about the circumstances that led some of our fellow pilots to deviate from their flight plan, in some cases with tragic results. The information provided here is based on reports published by the Transportation Safety Board.
British Columbia — Chinook Birdman — Always check the propeller drive belt for wear.
The aircraft appears to have stopped climbing at an altitude of about 200 ft, even though the engine throttle had been set to maximum power at takeoff. A forced landing followed, causing damage to the airframe. The pilot, who had logged only six hours of flying time since the start of the year, believes that the loss of pulling power from the propeller was caused by insufficient tension in the belt connecting it to the engine. This belt had been in service for seven years. During the pre-flight inspection, the pilot had checked this mechanism and found that he could displace this belt by about ? in. by applying 10 lbs of pressure at a specific point. After the forced landing, the pilot checked the belt's displacement again and found that it was between ¾ and 1 in. Rubber dust was visible under the lower pulley of the belt mechanism, indicating that the belt had been subjected to rubbing and premature wear. Once the aircraft had been brought back to the hangar and the propeller drive mechanism had cooled down, the belt tension was checked again, and the displacement had returned to ? in. In preceding flights, the ambient temperature had been low, which was surely what had prevented the belt from slipping in the drive pulley mechanism. Pilots of ultralight aircraft equipped with Rotax engines recommend that this belt be replaced approximately once every 8 to 10 years. The pilot in question has decided to replace this belt every two years from now on, as a safety precaution. After this incident, he said that he should have paid attention to the sound of his engine during takeoff, because the problem with the belt likely caused the engine to run louder than usual. If the pilot had noticed this noise, then cut the engine power back, he might have been able to keep flying longer and return to his departure point without incident. Inspector Pete Firlotte, of the Prairie and Northern Region, reminds readers that belts adjust themselves when necessary and sometimes sag and weaken with age, so that they can no longer do their job as well as before-just like some pilots. It is far better to replace a belt at regular intervals than to have to make a forced landing!
Quebec — Motorized paraglider — Unapproved modification
The student pilot had motorized his paraglider by adding an engine and propeller, but because the surface area of the paraglider wing was not designed for this additional weight, the aircraft became harder to control. An instructor who was making a pleasure flight in the area saw his student who, unbeknownst to him, was preparing to take off. A few minutes later, the instructor saw that the student had taken off and had put his aircraft into a spiral at an altitude far too low for this manoeuvre. The instructor made several attempts to contact the student by radio to advise him of the risk he was running and to tell him to land immediately, but in vain; the student pilot never responded. The aircraft crashed in a field not far from where it had taken off, and the student pilot did not survive the crash.
To build aircraft that meet very specific flight requirements, manufacturers spend thousands of hours designing and testing their components and systems. When you make modifications to your aircraft's structure or control systems, you run a high risk of compromising its structural integrity and your own safety. Your aircraft's flight characteristics are closely determined by its original components, and it can be dangerous or even fatal to modify them. If you do so, you and your aircraft become an experimental system, subject to all the difficulties that this entails. Do you really think that you are qualified to be a test pilot?
Alberta — RAF 2000 Gyroplane — Let's stick to approved manoeuvres!
The pilot had qualified as a gyroplane instructor and had logged many, many hours of flying time on this type of aircraft. He had assembled his new gyroplane himself and was about to make his first flight. The weather was clear, and the takeoff went without a hitch. After making a few manoeuvres in the airport circuit, the pilot decided to make a high-speed pass. At that precise moment, witnesses on the ground heard a muffled noise and saw the aircraft break apart in the air. The pilot lost his life. The cause of this accident is hard to determine, but the high-speed pass may have imposed an excessive load on the airframe, causing a major failure of its components. As you can see, in some cases, one overload is all it takes to cause an accident, even with a brand-new aircraft. So make sure to always comply with the manufacturer's specifications. How long has it been since you reviewed the flight manual for your aircraft? Can you state with assurance that you are familiar with all its contents? Do you perform a weight and balance analysis regularly, or only following a good scare?
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