transverse flow vs translation lift - threads merged
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Try teaching it in an R22: It might go something like this :-
1) Brief it
2) Go out and fail to demonstrate it (the aircraft will roll the wrong way)
3) Go back to the briefing room and talk about couples instead
1) Brief it
2) Go out and fail to demonstrate it (the aircraft will roll the wrong way)
3) Go back to the briefing room and talk about couples instead
Although I'm sure the actual aerodynamics are much more complicated than the simple explanation we learn.
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Changing the paradigm ?
Would not it be useful to just talk more about coned rotors as complete systems instead of always going back to all the nuts and bolts it is composed of.
The precession thing has been a very interesting topic on this forum, remember the lively discussions with Lu,
but a rotor is a lot more than that, and going each time through half of an advanced physics course to explain something is imho not always the most productive educational way. It also has a danger that by omitting the other half, wrong conclusions are drawn.
I would follow the suggestion of thecontroller and talk more about aggregate things
I would only go once thru the details of precession and blade speed differences and flap etc to explain the underlying mechanismes, but I would summarize it at an aggregate level as follows
- a rotor blows back, just like an umbrella
- the more its coned the more it blows back
- the higher the speed to more it blows back
- to compensate blow back we put the cyclic more forward, if we don't the nose goes up.
- retreating blade stall makes blow back worse
- coning provokes a blow back delay in the system resulting in a sideways tilting of the rotor that is ironed out by the rigging, so not to worry to much about.
m2c
d3
The student can then forget the details.
The precession thing has been a very interesting topic on this forum, remember the lively discussions with Lu,
but a rotor is a lot more than that, and going each time through half of an advanced physics course to explain something is imho not always the most productive educational way. It also has a danger that by omitting the other half, wrong conclusions are drawn.
I would follow the suggestion of thecontroller and talk more about aggregate things
I would only go once thru the details of precession and blade speed differences and flap etc to explain the underlying mechanismes, but I would summarize it at an aggregate level as follows
- a rotor blows back, just like an umbrella
- the more its coned the more it blows back
- the higher the speed to more it blows back
- to compensate blow back we put the cyclic more forward, if we don't the nose goes up.
- retreating blade stall makes blow back worse
- coning provokes a blow back delay in the system resulting in a sideways tilting of the rotor that is ironed out by the rigging, so not to worry to much about.
m2c
d3
The student can then forget the details.
I seem to remember it's quite easy to demonstrate in an R22, from the hover you put the stick forward a little bit and keep it there, you will get flapback, push it forward a little more and the aircraft will start to accellerate and get ETL, you get inflow roll (to the right), caused by transverse flow effect.
I once asked a rotary test pilot at Boscombe why the Lynx rolled away from the advancing side as it accelerated. He couldn't answer. He said that sometimes that they have absoloutly no idea why things happen as they do.
