Colibri49
22nd Apr 2012, 21:05
Please would those of you who still believe that when any helicopter loses all engine power to the rotors, it will fall straight down like a brick, help me to quash this fallacy. Even after more than 30 years of offshore helicopter flying, I still occasionally hear this nonsense.
Most recently I shut down offshore for a minor engine problem which necessitated an engineer being flown out to investigate. As usual and understandably, there were the usual questions about "what if both engines were to fail?" Even the oil company's safety representative had difficulty accepting the concept of autorotation.
In the extremely unlikely event that this should happen on a large twin-engined helicopter, or a little more frequently on a small single-engined helicopter, the aircraft descends under the law of gravity. The descent angle is something less than 45 degrees and the relative airflow "rushes up" from below and forward.
This airflow passes through the main rotor and causes it to "windmill" (autorotate) resulting in the rotors maintaining approximately their normal rpm. Although the rate of descent is about 4 times greater than that of an aeroplane, in the last couple of hundred feet the pilot flares (raises the nose) of the helicopter which reduces the rate of descent to near zero and reduces the forward speed to something like 20 mph.
The flaring manoeuvre causes the rotor to increase rpm, which gives extra inertia (stored energy) in the rotor for a few seconds, allowing the pilot to cushion the touchdown to a very gentle bump, possibly as gentle as a normal landing.
Which would you prefer; a gentle bump with very low forward speed, or being in an aeroplane in a similar situation and arriving on the surface with forward speed in the region of 100 mph?
I'm no hero and I wouldn't dream of flying anything which just falls vertically as soon as all power is lost. My flying experience spans 45 years and I've flown single-engined military aeroplanes and helicopters, as well as single- and twin-engined helicopters for my civilian career.
Please, please use whatever channels you have to pass this on to offshore workers. Perhaps it will help to reduce some of the apprehension which they might feel and let them understand that if one of the two engines in offshore helicopters should fail, then they aren't suddenly in serious danger.
Here's a link to a good Youtube video of what I'm talking about http://www.youtube.com/watch?v=phaWRjAVnes.
Perhaps offshore workers don't realise that when considering offshore helicopter accidents in the UKCS only (no single-engined, no onshore, no private flights) then the accident statistics are closer to large airliners than to helicopters in general.
Most recently I shut down offshore for a minor engine problem which necessitated an engineer being flown out to investigate. As usual and understandably, there were the usual questions about "what if both engines were to fail?" Even the oil company's safety representative had difficulty accepting the concept of autorotation.
In the extremely unlikely event that this should happen on a large twin-engined helicopter, or a little more frequently on a small single-engined helicopter, the aircraft descends under the law of gravity. The descent angle is something less than 45 degrees and the relative airflow "rushes up" from below and forward.
This airflow passes through the main rotor and causes it to "windmill" (autorotate) resulting in the rotors maintaining approximately their normal rpm. Although the rate of descent is about 4 times greater than that of an aeroplane, in the last couple of hundred feet the pilot flares (raises the nose) of the helicopter which reduces the rate of descent to near zero and reduces the forward speed to something like 20 mph.
The flaring manoeuvre causes the rotor to increase rpm, which gives extra inertia (stored energy) in the rotor for a few seconds, allowing the pilot to cushion the touchdown to a very gentle bump, possibly as gentle as a normal landing.
Which would you prefer; a gentle bump with very low forward speed, or being in an aeroplane in a similar situation and arriving on the surface with forward speed in the region of 100 mph?
I'm no hero and I wouldn't dream of flying anything which just falls vertically as soon as all power is lost. My flying experience spans 45 years and I've flown single-engined military aeroplanes and helicopters, as well as single- and twin-engined helicopters for my civilian career.
Please, please use whatever channels you have to pass this on to offshore workers. Perhaps it will help to reduce some of the apprehension which they might feel and let them understand that if one of the two engines in offshore helicopters should fail, then they aren't suddenly in serious danger.
Here's a link to a good Youtube video of what I'm talking about http://www.youtube.com/watch?v=phaWRjAVnes.
Perhaps offshore workers don't realise that when considering offshore helicopter accidents in the UKCS only (no single-engined, no onshore, no private flights) then the accident statistics are closer to large airliners than to helicopters in general.