Why do we Lose Airspeed in a Turn and What Causes This?
the engine makes a lot of noise. This noise attracts any Lift Pixies in the area and they jump on the wing thus creating lift and raising the aircraft into the air.
Thank you Arty Fufkin, I stand totally corrected. I have never heard such an erudite and comprehensive reason for the way things work,
The only item missing is of course the Gremlin, which I assume is 'anti-pixie' and more prevalent in hot, high and/or dusty places (and middle earth) and the reason for so many things falling out the sky.
I'm now wondering how to make my whirly-whirly helicopeter thing more attractive to pixies!
The only item missing is of course the Gremlin, which I assume is 'anti-pixie' and more prevalent in hot, high and/or dusty places (and middle earth) and the reason for so many things falling out the sky.
I'm now wondering how to make my whirly-whirly helicopeter thing more attractive to pixies!
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Mike O: Can I humbly suggest you get yourself into a heavy jet and go and fly some orbits at F300 in a nice steady 150 kt wind? If your theory is correct then you should alternate between stalling and dropping sonic booms, as the headwind/tailwind component changes dramatically.
The vagaries of ATC and traffic flow cause me to do this (ie the orbiting thing, not the stalling/sonic boom thing) on an all too regular basis and I can happily report that as long as the wind is steady, so is the airspeed - with basically no change in thrust whatsoever.
The vagaries of ATC and traffic flow cause me to do this (ie the orbiting thing, not the stalling/sonic boom thing) on an all too regular basis and I can happily report that as long as the wind is steady, so is the airspeed - with basically no change in thrust whatsoever.
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Very interesting debate on the finer points of lift etc. I am afraid I only agree with the latter drift of the thread concerning Lift Pixies. My own experience is confined to the lesser known Thrust demons as found on rotary craft.
They too are atracted by noise and vibration hence the inherent clattery nature of all things rotary. However Thrust demons also like thrills and the ability to show off. The challenge of whirling round and around while holding on and avoiding hitting the fuselage is candy for them. It may be noted that the tips of the roto5 blades move faster through the air hence the bigger stronger thrust demons can be found here. Unfortunately being demons they also like hot sandy places, it is like home. They therefore need more noise vibration etc to entice them to play. Note that the chinook lift is very good and this maybe due to the added danger to a Thrust demon of dodging his mates on the other blades as they barely miss each other. Thrust Demons are, I am told, closely related to Gremlins. As they get alond well this probably explains the higher maintenance and lower serviceability in general of RW ac.
Gliders and lift pixies. I assume some are initially attracted due to the winch noise or fall off the towing ac. Once released the noise goes away and the pixies get bored and go off, hence ac descends.
parachutes and bang seats probably work in a similar way. Initial noise and screams of "oh my god i'm going to die" attract pixies for the initial deceleration and then a gentle fall.
However I am no expert.
They too are atracted by noise and vibration hence the inherent clattery nature of all things rotary. However Thrust demons also like thrills and the ability to show off. The challenge of whirling round and around while holding on and avoiding hitting the fuselage is candy for them. It may be noted that the tips of the roto5 blades move faster through the air hence the bigger stronger thrust demons can be found here. Unfortunately being demons they also like hot sandy places, it is like home. They therefore need more noise vibration etc to entice them to play. Note that the chinook lift is very good and this maybe due to the added danger to a Thrust demon of dodging his mates on the other blades as they barely miss each other. Thrust Demons are, I am told, closely related to Gremlins. As they get alond well this probably explains the higher maintenance and lower serviceability in general of RW ac.
Gliders and lift pixies. I assume some are initially attracted due to the winch noise or fall off the towing ac. Once released the noise goes away and the pixies get bored and go off, hence ac descends.
parachutes and bang seats probably work in a similar way. Initial noise and screams of "oh my god i'm going to die" attract pixies for the initial deceleration and then a gentle fall.
However I am no expert.
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I love the way this thread has developed. It's refreshing to find a thread on Prune that hasn't developed into a inter-service/inter-type/international willy waggling contest.
And it's edumacational too
Though I still like the "so you lift the lever up, science occurs, and the helicopter lifts to the hover" approach to rotary PofF. All this talk of pixies and demons is all a bit A level for me....
And it's edumacational too
Though I still like the "so you lift the lever up, science occurs, and the helicopter lifts to the hover" approach to rotary PofF. All this talk of pixies and demons is all a bit A level for me....
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Speed changes in the turn
Turns out that every aircraft will be different. The fast jets hardy ever notice it as they have lots of power, lower drag and go fast. The heavy, draggy, propeller driven, slower transports however are much more aware of it.
In a turn going into the wind the airspeed will gradually increase, but so will the effect of drag, slowing you down. In a turn going with the wind the airspeed will slowly drop, but the reduction in drag will allow the thrust to increase the air speed.
The heavier you are the more inertia you have and the slower you can recover. The faster you turn the less time there is for the air speed to recover.
SG
In a turn going into the wind the airspeed will gradually increase, but so will the effect of drag, slowing you down. In a turn going with the wind the airspeed will slowly drop, but the reduction in drag will allow the thrust to increase the air speed.
The heavier you are the more inertia you have and the slower you can recover. The faster you turn the less time there is for the air speed to recover.
SG
Last edited by Soft Ground; 14th May 2007 at 08:21.
Soft Ground,
No it doesn't. It will increase if you try to fly (whether you mean to do it or not) a constant groundspeed, but that is because you have made it happen, not simply because you have turned. However,
is right but not for the reasons you give.
It has all been explained very clearly above:
As you put on bank, the vertical component of lift is reduced, so more angle of attack is needed to generate the extra lift required to maintain altitude. An increase in AoA gives more lift but also more drag, so the ac slows down.
It has nothing to do with into wind/downwind or indeed breaking wind.
This bit:
is equally as wrong, unless you are trying to fly a constant groundspeed.
Perhaps they were simply being polite!
In a turn going into the wind the airspeed will gradually increase
but so will the effect of drag, slowing you down.
It has all been explained very clearly above:
As you put on bank, the vertical component of lift is reduced, so more angle of attack is needed to generate the extra lift required to maintain altitude. An increase in AoA gives more lift but also more drag, so the ac slows down.
It has nothing to do with into wind/downwind or indeed breaking wind.
This bit:
In a turn going with the wind the airspeed will slowly drop, but the reduction in drag will allow the thrust to increase the air speed
Was never implemented though as they couldn't afford the solution!
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I am aware that lift is the main cause, but that has already been explained.
SO I did not repeat it.
I was only referring to the effect of turning into a head or tail wind.
Speed will be lost because of the increased drag caused by the higher angle of attack needed to generate the extra lift.
Inertial will try to maintain ground speed, not the pilot. But the drag/thrust balance of the aircraft will try and maintain airspeed.
Simple physics.
In practice the pilot will make small adjustements to thrust to maintain airspeed. You dont need to understand this to fly, but in some circumstances it may help.
SG
SO I did not repeat it.
I was only referring to the effect of turning into a head or tail wind.
Speed will be lost because of the increased drag caused by the higher angle of attack needed to generate the extra lift.
Inertial will try to maintain ground speed, not the pilot. But the drag/thrust balance of the aircraft will try and maintain airspeed.
Simple physics.
In practice the pilot will make small adjustements to thrust to maintain airspeed. You dont need to understand this to fly, but in some circumstances it may help.
SG
I was only referring to the effect of turning into a head or tail wind.
When flying on instruments, and you make a turn, a little extra power is needed to keep the airspeed. If you do a 360 degree turn, by your argument, you would be increasing and decreasing pwr all the time as you turn with and against the wind, but that simply doesn't happen. The extra bit of power is added at the beginning to maintain the airspeed, and is left there until the aircraft is rolled out again.
This may not be in accordance with your "simple physics", but it is what actually happens!
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...........the engine makes a lot of noise. This noise attracts any Lift Pixies in the area and they jump on the wing thus creating lift and raising the aircraft into the air.
In fact, with the right conditions and a Pixie filter, you can photograph Lift Pixies. They don’t like it – but you can; they're only little.
PS. What Arty didn't mention, and perhaps should have done, is thrust reversers.
They're there to blow the Lift Pixies off the wing.
Last edited by forget; 13th May 2007 at 14:54.
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Soft Ground, me'old, wind is the movement of air relative to the ground. If you are not on the ground, or fixed to it, you will not feel the wind. Go up in an air balloon and you will travel with the wind but your scarf will not fly like biggles and your airspeed will be zero.
I believe you are confusing wind shear with the problem. Wind shear occurs when the aircraft encounters 2 or more air masses that are not moving in the same direction or at the same speed; ie turbulence.
Turning into a headwind is an expression to describe an aircraft that turns within an air mass such that the aircraft's new direction is opposite to the direction that the air mass is moving relative to the ground.
Wind is irrelevant in aerodynamics, but is everything in navigation. You only need to ask the lift pixies....
I believe you are confusing wind shear with the problem. Wind shear occurs when the aircraft encounters 2 or more air masses that are not moving in the same direction or at the same speed; ie turbulence.
Turning into a headwind is an expression to describe an aircraft that turns within an air mass such that the aircraft's new direction is opposite to the direction that the air mass is moving relative to the ground.
Wind is irrelevant in aerodynamics, but is everything in navigation. You only need to ask the lift pixies....
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In practice the pilot will make small adjustements to thrust to maintain airspeed. You dont need to understand this to fly, but in some circumstances it may help.
Do tell us which renowned school of aviation taught you this totally incorrect theory.