Hey,
I’m a fixed wing PPL. I’m studying a university paper on accident investigation.
This assignment has me really stumped, and was wondering if anyone could point me in the right direction.
A Robinson R22 helicopter was operating some 10 nm east of the aerodrome with a flying instructor and student on board. During the flight the aircraft was seen to break apart and fall to the ground. No one saw the aircraft in flight immediately before the accident sequence began but several persons saw the aircraft descend in a flat attitude and pieces fall from it after the pilots were in trouble. Witnesses also observed that the main rotor was stationary and the blades were coned. At the accident site the first persons to arrive encountered a strong smell of fuel. Both occupants were killed in the accident but no fire occurred.
RELEVANT FACTS.
This was the instructor’s first flight with a student after qualifying as an instructor.
The instructor had flown 3000 hours on helicopters, held a CPL(H) and an R22 rating.
More than half of the instructor’s helicopter flying was in the Robinson R22 and R44 helicopters.
Both pilots passed a medical within the last 30 days and the autopsies after the accident revealed no medical factors which might have contributed to the accident.
The weather conditions observed at the aerodrome were:
Wind 270◦/12 knots gusting to 18 knots
Visibility: 25 nm
Cloud: Scattered at 2500 feet broken at 5000 and 20 000 feet
Ambient temperature at sea level: 14◦C dew point 5◦C
The helicopter had sufficient fuel for 2 hours flying [13gallons] when it took off 20 minutes before the accident.
There were indications that the carburettor heat was “OFF” when the aircraft collided with the ground with little forward motion.
The main rotor blades were bent into a “tulip” shape but still attached on impact.
The main rotor had flapped down in flight and chopped off the tail boom in the vicinity of the anti-collision light, at low rpm.
The aircraft was close to it maximum permitted all up weight when it took off.
REQUIREMENT.
Explain with the aid of diagrams two possible explanations for this accident which are in keeping with the facts listed above.
I can come up with one explanation. That is carburetor icing has caused the engine to fail, has gone unrecognized, leading to a blade stall, and chopping off the tail boom.
Can anyone else think of any other ideas that does not involve a blade stall?? Maybe the failure of a certain component, that would cause the rotor to strike the tail boom at slow RRPM?
Thank You!