Serious question for a QFI
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The sum of all lift in straight and level flight (positive and negative, from all parts of the plane) = gravity, otherwise you would be going up or down.
The sum of all lift in straight and level flight (positive and negative, from all parts of the plane) = gravity, otherwise you would be going up or down.
Back to Sir Isacc Newton.
Lightning Mate is right.
Lift is defined as a force.
However, formally, 'g' is referred to as the "acceleration due to gravity" to avoid this kind of argument.
The force on a mass caused by the acceleration due to gravity is, formally, weight.
The forces on an aircraft are in balance in straight, UNACCELERATED flight, which fits a constant rate of climb or descent as well as straight and level.
I haven't seen anyone correctly use momentum yet.
If you want a clear physical explanation of any of this, please PM me. I do this for a living.
Now, can we get back to interesting stuff like victory roll trimming and LL jokes?
F3WMB
MRAeS, MInstP
Lift is defined as a force.
However, formally, 'g' is referred to as the "acceleration due to gravity" to avoid this kind of argument.
The force on a mass caused by the acceleration due to gravity is, formally, weight.
The forces on an aircraft are in balance in straight, UNACCELERATED flight, which fits a constant rate of climb or descent as well as straight and level.
I haven't seen anyone correctly use momentum yet.
If you want a clear physical explanation of any of this, please PM me. I do this for a living.
Now, can we get back to interesting stuff like victory roll trimming and LL jokes?
F3WMB
MRAeS, MInstP
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Lightning Mate is right.
Fox3, ffs no more of that, it will go to his head and then we'll be right in the deep end.
SI Units. (Expressions to make you sigh)
The way I was tought is that Isaac Newton discovered Gravity when an Apple fell on his head. Four Apples = 1 Pound therefore 1 pound = four Newtons.
Kilowatts is what the Electric fire used to run on and a Litre's like a Metre only better 'cause it's wetter.
The dear old Frightening was so ancient that its ASI was calibrated in 'furlongs per fortnight'....
Is there any truth in the story that the fuel gauge read 'Empty....Fumes....Not enough....Still Not Enough....All you're getting but really not enough'
Or that the altimeter read 'Ground pounders....Mud movers....Learning Command....Truckies....Air Defence Sky Gods and V-bombers only'?
Is there any truth in the story that the fuel gauge read 'Empty....Fumes....Not enough....Still Not Enough....All you're getting but really not enough'
Or that the altimeter read 'Ground pounders....Mud movers....Learning Command....Truckies....Air Defence Sky Gods and V-bombers only'?
From what I've seen, the Altimeter should be
Groundpounders, Buccaneers, War, Falkland Islands, and then a biiig gap before mud movers. Americans are somewhere above Learning Command.
Lightning top speed 4 million furlongs per fortnight (though that's an awful lot of AARs in a fortnight!)
Groundpounders, Buccaneers, War, Falkland Islands, and then a biiig gap before mud movers. Americans are somewhere above Learning Command.
Lightning top speed 4 million furlongs per fortnight (though that's an awful lot of AARs in a fortnight!)
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I think.... momentum is mass x velocity. Velocity is a vector, thus momentum is a vector too, i.e. it has both magnitude and direction.
What this means is that, even at constant "speed" momentum changes around the loop (it swings around with the aircraft's velocity). Newton said roughly that "the rate of change of momentum is directly proportional to the applied force and takes place in the direction of that force".
To loop the loop, we need an extra bit of force perpendicular to the momentum vector to unbalance the forces on the aeroplane, i.e. to accelerate the aircraft mass towards the centre of the loop. This is produced by pulling back on the stick to increase angle of attack, increasing the lift generated by the wings, whilst maintaining airspeed with the throttle.
What this means is that, even at constant "speed" momentum changes around the loop (it swings around with the aircraft's velocity). Newton said roughly that "the rate of change of momentum is directly proportional to the applied force and takes place in the direction of that force".
To loop the loop, we need an extra bit of force perpendicular to the momentum vector to unbalance the forces on the aeroplane, i.e. to accelerate the aircraft mass towards the centre of the loop. This is produced by pulling back on the stick to increase angle of attack, increasing the lift generated by the wings, whilst maintaining airspeed with the throttle.
Last edited by FCSoverride; 31st Aug 2011 at 17:22. Reason: attempting more clarity!
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my go at answering.
FCSOveride has a great answer for you right there.
I always like to relate answers to real world examples. Therefore: talk to your son next time you go around a roundabout. Ok, it's lateral 'g', but the principle is the same (get him to lean 90 degrees to the right if it helps).
Before you his the roundabout, there is no lateral 'g', right? Start going round it and he will be thrown to the outside of the car. Keep going round, and the 'g' force will remain. A loop or a break is similar.
In the case of a loop though, we already at 1 (not zero) 'g'. If I pull up into a loop with 4 'g', then that's what I will feel (initially). At the top of the loop I will be doing the same thing with my aircraft but now the plus 1 'g' I would normally feel is acting the other way so I would feel about 2 'g'. (3 'g' in the vertical). You need to picture "plus 1 'g'" acting vertically downwards at all times.
In truth no-one flies constant 'g' loops - it wouldn't look like a loop. A barrel roll is different.
For breaks, if you have the power, 4 'g' will remain the same forever. Depending on aircraft type and power available, it may reduce as, has already been pointed out, increased lift increases drag, reducing speed (unless you have more power).
I always like to relate answers to real world examples. Therefore: talk to your son next time you go around a roundabout. Ok, it's lateral 'g', but the principle is the same (get him to lean 90 degrees to the right if it helps).
Before you his the roundabout, there is no lateral 'g', right? Start going round it and he will be thrown to the outside of the car. Keep going round, and the 'g' force will remain. A loop or a break is similar.
In the case of a loop though, we already at 1 (not zero) 'g'. If I pull up into a loop with 4 'g', then that's what I will feel (initially). At the top of the loop I will be doing the same thing with my aircraft but now the plus 1 'g' I would normally feel is acting the other way so I would feel about 2 'g'. (3 'g' in the vertical). You need to picture "plus 1 'g'" acting vertically downwards at all times.
In truth no-one flies constant 'g' loops - it wouldn't look like a loop. A barrel roll is different.
For breaks, if you have the power, 4 'g' will remain the same forever. Depending on aircraft type and power available, it may reduce as, has already been pointed out, increased lift increases drag, reducing speed (unless you have more power).
Gentleman Aviator
And if, by chance, you have a helium balloon in the back of the car as you drive your son around the roundabout (traffic circle), he (and you) may be surprised at the way IT leans.........