Utterly pointless, tenuous and hypothetical arguement
Joined: Jan 2006
Posts: 25
Likes: 0
From: Sydney, Australia
My earlier posts certainly didn't mention keeping station, and they certainly do mention that the helicopter will initially move backwards - it has to in order for the movement relative to the air to induce the "flapback" and attitude change.
The stability of these little helicopters is a velocity stability - they will tend to reduce their translational velocity to zero (or close to zero, it does depend a bit on the centre of gravity position). Thus if they are disturbed from an equilibrium state they will tend to reduce their velocity to zero, but certainly not over the same spot.
As regards the question of the additional lift required, my calculations suggest that if the plane accelerates at 0.4 G, then the apparent, tilted gravity seen by the helicopter is sqrt(1^2 + 0.4^2) which is about 1.08. Thus the helicopter would require about 8% greater lift to remain in a hover. I haven't measured this, but given the performance of these helicopters when fully charged, I think that they would easily be able to cope with the additional lift required.
Nick,
Matthew's suggestion of getting yourself one of these little helicopters is a great one. They are pretty cheap these days, and a lot of fun to fly about the house.
Daniel
The stability of these little helicopters is a velocity stability - they will tend to reduce their translational velocity to zero (or close to zero, it does depend a bit on the centre of gravity position). Thus if they are disturbed from an equilibrium state they will tend to reduce their velocity to zero, but certainly not over the same spot.
As regards the question of the additional lift required, my calculations suggest that if the plane accelerates at 0.4 G, then the apparent, tilted gravity seen by the helicopter is sqrt(1^2 + 0.4^2) which is about 1.08. Thus the helicopter would require about 8% greater lift to remain in a hover. I haven't measured this, but given the performance of these helicopters when fully charged, I think that they would easily be able to cope with the additional lift required.
Nick,
Matthew's suggestion of getting yourself one of these little helicopters is a great one. They are pretty cheap these days, and a lot of fun to fly about the house.
Daniel
Joined: Feb 2006
Posts: 53
Likes: 0
From: Frozen North
The balloon
The helicopter, I was sure about (I'm glad that Nick has finally caught up).
The ballon I'm not quite so certain of but I believe that assuming no deformation of the bus, all the air would have a tendency to accelerate forwards and compress that at the front so, given a sufficiently long bus and prolonged acceleration, there would be movement of the air towards the front. Since the density of the balloon is lower, it would be forced rearwards. In practice, deformation of the space would, I am sure mask this effect.
OA
The ballon I'm not quite so certain of but I believe that assuming no deformation of the bus, all the air would have a tendency to accelerate forwards and compress that at the front so, given a sufficiently long bus and prolonged acceleration, there would be movement of the air towards the front. Since the density of the balloon is lower, it would be forced rearwards. In practice, deformation of the space would, I am sure mask this effect.
OA
Joined: Jun 2006
Posts: 60
Likes: 0
From: between rocks and hard places
Fascinating, all the arguments. Perhaps its time to do what the great uncle Igor Sikorsky said: "Gentlemen, if fact and theory are at odds, I implore you to consider the facts!" So, has anyone actually tried the experiment yet?
