762 ON ONE ENGINE (maybe)
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762 ON ONE ENGINE (maybe)
Need 762 expert please, friend has just flown down to tabago on a 767-200, stated whilst flying down the east coast of the USA he noticed that the fan blades where vertually stationery and that it was quiet on the starboard side of the aircraft. PS, please dont shoot the messenger... I Did point out that it seems strange but im no 762 expert. Your thoughts please.....................
Even a engine not running on its own will have its fan blades windmilling so fast that they are just a blur. Now if he was looking out the left window at a GE or Pratt engine then perhaps what he saw not turning was the stator behind the fan. For a Rolls powered machine you have to look out the right window to see the stator behind the fan.
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You don't really need an expert.
On any twin engine airliner if an engine fails or needs to be shut down then it would result in a diversion to the nearest suitable airport. That is because you have utilized the redundancy. There are an awful lot of suitable airports down the Atlantic coast of the USA.
As has already been pointed out the fan is not stationary on a windmilling engine. If you look at the fan on an aircraft that is shut down and parked into the wind you will see it rotating, often at quite a high rate. Given the speed of rotation they might have appeared stationary to your friend, but even on a failed engine it is extremely unlikely that they would have been. Even if the fan had been subject to an extreme event that resulted in total seizure, the vibration would not have likely been a situation where "it seemed a bit quiet on the starboard side."
Ask your friend if he still had the headphones in his right ear?
On any twin engine airliner if an engine fails or needs to be shut down then it would result in a diversion to the nearest suitable airport. That is because you have utilized the redundancy. There are an awful lot of suitable airports down the Atlantic coast of the USA.
As has already been pointed out the fan is not stationary on a windmilling engine. If you look at the fan on an aircraft that is shut down and parked into the wind you will see it rotating, often at quite a high rate. Given the speed of rotation they might have appeared stationary to your friend, but even on a failed engine it is extremely unlikely that they would have been. Even if the fan had been subject to an extreme event that resulted in total seizure, the vibration would not have likely been a situation where "it seemed a bit quiet on the starboard side."
Ask your friend if he still had the headphones in his right ear?
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Rainboe, what a wierd comment, get a new friend because he commented about what he percieved to have seen?
Are you offering your services as a learned friend? Anyone would be delighted to have you over for tea and buns and a boring chat.
On thread - yes of course its possible for your friend to have witnessed the fan blades stationary in flight in a failed turbine (siezed) situation. Whilst uncommon, not impossible.
In the following incident to a British Airways 767 the engine suffered a 'bird strike' that caused the unusual fracturing of the fan blade and detachment of the accoustic lining. The fan was seized on landing.
See the article here
Boeing 767-336, G-BNWM
Hope that explains how (possibly) your friend could be right, though i would agree with earier poster that in this situation a diversion would have been enacted.
Maybe ask him how many blades did he count?
Are you offering your services as a learned friend? Anyone would be delighted to have you over for tea and buns and a boring chat.
On thread - yes of course its possible for your friend to have witnessed the fan blades stationary in flight in a failed turbine (siezed) situation. Whilst uncommon, not impossible.
In the following incident to a British Airways 767 the engine suffered a 'bird strike' that caused the unusual fracturing of the fan blade and detachment of the accoustic lining. The fan was seized on landing.
See the article here
Boeing 767-336, G-BNWM
Hope that explains how (possibly) your friend could be right, though i would agree with earier poster that in this situation a diversion would have been enacted.
Maybe ask him how many blades did he count?
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I'm no expert by any means but have spent a couple of hundred hours behind single engine props and twins. I do know when the RPM of the blade matches the frequency of the light around it, the blade will 'appear' to disappear completely. Maybe the same sort of thing happens here.
There is a scientific formula to work out when this occurs, but its been so long since I did my exams.. Not exactly something you need to remember for everyday use.
There is a scientific formula to work out when this occurs, but its been so long since I did my exams.. Not exactly something you need to remember for everyday use.
Last edited by Mike The pom; 15th Oct 2008 at 03:20. Reason: Spelling
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It's the well-known "strobe" effect - the rotor doesn't "disappear", it merely appears to stand still if the flashing light is synced with the rotor speed.
Also appears in movies when wagon wheel spokes - or propeller blades - match the frame rate of the camera. If speed is slightly mismatched, the rotor can appear to turn slowly backwards.
But I don't see that this answers ukdean's question.
Also appears in movies when wagon wheel spokes - or propeller blades - match the frame rate of the camera. If speed is slightly mismatched, the rotor can appear to turn slowly backwards.
But I don't see that this answers ukdean's question.
