Why do we Lose Airspeed in a Turn and What Causes This?
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"Genghis, would you care to comment on John Farley's paragraph which I quoted? I believe that he knows what he's talking about more than most."
Yes, certainly. He is incorrect on this point ;-)
Would you care to comment on the logic of the steady state turn example?
Yes, certainly. He is incorrect on this point ;-)
Would you care to comment on the logic of the steady state turn example?
Mike,
Care to comment on my Coffee cup?
You continue to insist kinetic energy is ONLY relative to the Earths surface.
The Earths surface is a very small piece of the universe where, I believe, universal laws of physics still apply.
And how about my Goldfish? You seem to br selectively ignoring arguments which clearly dis-prove your case.
Don't believe I'M saying this but, yes, Johm Farley is wrong on this occasion.
You were also pretty selective in your googling. I've just done the same and come up with a myriad of articles de-bunking the myth-
Heres a few-
http://www.x-plane.com/myths.html
http://www.aeroexperiments.org/brainteasers.shtml
http://www.djaerotech.com/dj_askjd/d.../downwind.html
Can you also answer me this? If the effect is small in the light winds at the surface, it must be proportionally greater in strong winds. Iv'e been in holding patterns in 120kt winds and, guess what? turning downwind the aircraft did no fall out of the sky.
Care to comment on my Coffee cup?
You continue to insist kinetic energy is ONLY relative to the Earths surface.
The Earths surface is a very small piece of the universe where, I believe, universal laws of physics still apply.
And how about my Goldfish? You seem to br selectively ignoring arguments which clearly dis-prove your case.
Don't believe I'M saying this but, yes, Johm Farley is wrong on this occasion.
You were also pretty selective in your googling. I've just done the same and come up with a myriad of articles de-bunking the myth-
Heres a few-
http://www.x-plane.com/myths.html
http://www.aeroexperiments.org/brainteasers.shtml
http://www.djaerotech.com/dj_askjd/d.../downwind.html
Can you also answer me this? If the effect is small in the light winds at the surface, it must be proportionally greater in strong winds. Iv'e been in holding patterns in 120kt winds and, guess what? turning downwind the aircraft did no fall out of the sky.
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Not going to comment on the logic of the arguments, but for anyone interested in experimental evidence (we had this discussion at work a little while ago)….
FL 250, wind 244/70, 300 KDAS, smooth air, GPS pod, instrumented ac, autopilot (height hold) and autothrottle engaged.
Did a bunch of 720’s at various AoBs and then looked at the traces afterward*. No temporary loss of speed, no increase in fuel flow (thrust) as you went into/down wind.
*And for the ‘concerned’, it was done at ‘no cost’ while I had to hang around for another asset to appear.
Ray ;-)
FL 250, wind 244/70, 300 KDAS, smooth air, GPS pod, instrumented ac, autopilot (height hold) and autothrottle engaged.
Did a bunch of 720’s at various AoBs and then looked at the traces afterward*. No temporary loss of speed, no increase in fuel flow (thrust) as you went into/down wind.
*And for the ‘concerned’, it was done at ‘no cost’ while I had to hang around for another asset to appear.
Ray ;-)
I don’t think I’ve ever seen so much horses**t written in a thread before regarding the ‘effects’ of groundspeed. . Your aircraft flies in a (relatively) steady state air mass, so you should always fly with regard to your IAS – Indicated AIR Speed, and it matters not if that air mass is still or moving at 10kts, 50kts or even 200kts. Your VMax remains the same and your stalling speed even more so. If you are above 4000ft or in cloud you wouldn’t even notice changes in ground speed.
Unfortunately as you get lower you start becoming aware of groundspeed, and sadly one of the physiological aspects of flying as you get lower is that your eyes start to look outside more than inside, and by about 500ft or so you subconsciously start flying relative to groundspeed. That is all very well if you are already downwind (in your steady state air mass), because if you turn into wind using your visually assessed groundspeed your IAS will increase. Unfortunately if you turn downwind ……….! Again, no problem if you have a lot of speed on already, but if your IAS is relatively slow – ie you’re looking at something specific on the ground – the principles of flight will win out and stalling speed will catch you very quickly. Now the only way out is to stuff the nose forward (if you can) and open the throttle, and even more unfortunately the terra firma magnet is there waiting for you. If you want a classic case of relatively inexperienced pilot flying groundspeed instead of airspeed look at the police Optica, crash, which unfortunately killed not only the crew but also a very promising aircraft project.
One of the first things we teach during the low flying intro to all military rotary pilots is how easy it is to get suckered into flying groundspeed instead of airspeed, and just how easy it is to be bitten when you’re heavy, low and slow.
As an aside, a few years ago I was diverted to pick up a microlight pilot with a serious back injury who had stalled in from about 200ft. It was a windy day and he was at the top of a ridge line, along with about 30 – 40 other microlights and hang gliders. As we sat waiting for him to be stabilised and stretchered into the aircraft we watched these ac launching off the top of the ridge into the updraughting wind and getting plenty of lift as well. Over 50% of these pilots turned back over the ridge once they were above it and got quite a fright, ‘cos they lost AIRSPEED by maintaining groundspeed, with the ensuing incipient stall. Most recovered, but by the time we lifted we had four more patients for Swindon hospital!
WRT to the original question - go look at your PoF notes re Lift and Weight
Unfortunately as you get lower you start becoming aware of groundspeed, and sadly one of the physiological aspects of flying as you get lower is that your eyes start to look outside more than inside, and by about 500ft or so you subconsciously start flying relative to groundspeed. That is all very well if you are already downwind (in your steady state air mass), because if you turn into wind using your visually assessed groundspeed your IAS will increase. Unfortunately if you turn downwind ……….! Again, no problem if you have a lot of speed on already, but if your IAS is relatively slow – ie you’re looking at something specific on the ground – the principles of flight will win out and stalling speed will catch you very quickly. Now the only way out is to stuff the nose forward (if you can) and open the throttle, and even more unfortunately the terra firma magnet is there waiting for you. If you want a classic case of relatively inexperienced pilot flying groundspeed instead of airspeed look at the police Optica, crash, which unfortunately killed not only the crew but also a very promising aircraft project.
One of the first things we teach during the low flying intro to all military rotary pilots is how easy it is to get suckered into flying groundspeed instead of airspeed, and just how easy it is to be bitten when you’re heavy, low and slow.
As an aside, a few years ago I was diverted to pick up a microlight pilot with a serious back injury who had stalled in from about 200ft. It was a windy day and he was at the top of a ridge line, along with about 30 – 40 other microlights and hang gliders. As we sat waiting for him to be stabilised and stretchered into the aircraft we watched these ac launching off the top of the ridge into the updraughting wind and getting plenty of lift as well. Over 50% of these pilots turned back over the ridge once they were above it and got quite a fright, ‘cos they lost AIRSPEED by maintaining groundspeed, with the ensuing incipient stall. Most recovered, but by the time we lifted we had four more patients for Swindon hospital!
WRT to the original question - go look at your PoF notes re Lift and Weight
Any reference to helicopter aerodynamics (if that isn't an oxymoron) is, in any case, irrlevant. Everone knows that the only reason they stay airborne is because they are so ugly that the earth repels them.....
Ray,
"FL 250, wind 244/70, 300 KDAS, smooth air, GPS pod, instrumented ac, autopilot (height hold) and autothrottle engaged."
"...no temporary loss of speed"
No $hit, Sherlock!
Ray,
"FL 250, wind 244/70, 300 KDAS, smooth air, GPS pod, instrumented ac, autopilot (height hold) and autothrottle engaged."
"...no temporary loss of speed"
No $hit, Sherlock!
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"...no temporary loss of speed"
No $hit, Sherlock!
Yes - the autothrottle in the aircraft is so amazing that it can hold the EXACT airspeed and never lets it drop by even a knot...
No $hit, Sherlock!
Yes - the autothrottle in the aircraft is so amazing that it can hold the EXACT airspeed and never lets it drop by even a knot...
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None of the grandiose 'energy concept' bolleaux is worth a rat's
Thing is Beags, since energy is a scalar rather than a vector, and scalars are much easier to work with than vectors, there are a quite a few things in the universe that are a hell of a lot easier to comprehend by looking at the energy changes involved rather than by looking at the forces involved.
Mike
None of which detracts from the fact that while you have a better grasp of some parts of basic Physics than most of the folk here, you have lost the plot. Educational qualifications not withstanding, please examine the possibility that you are muddling your frames of reference. The fact that there are many others on this thread who are revealing varying degrees of Physics non-comprehension does not automatically make you correct on this point. The turning effect you describe does not exist, (and yes, your quote reveals JF to have been having a bad day as well).
pb
I have to say that I have never heared such rubbish spoken on the subject of Aerodynamics. The reason for the effect you describe is as follows:
Lift on an aircraft's wing is purely a result of the presence of Lift Pixies. Whilst they are best known for their elevative powers, Lift Pixies also have the notable properties of being invisible to the sober and having an extreme aversion to peace and quiet.
When a pilot begins the take off roll, the throttle is opened and 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.
When an aircraft enters a turn some of the Lift Pixies lose their footing and fall off the aircraft's wing. This causes a loss of lift and unless the pilot takes immediate action the aircraft will descend. By adding more power, the engine makes more noise and entices the Lift Pixes back onto the wing and lift is restored.
Simple.
Lift on an aircraft's wing is purely a result of the presence of Lift Pixies. Whilst they are best known for their elevative powers, Lift Pixies also have the notable properties of being invisible to the sober and having an extreme aversion to peace and quiet.
When a pilot begins the take off roll, the throttle is opened and 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.
When an aircraft enters a turn some of the Lift Pixies lose their footing and fall off the aircraft's wing. This causes a loss of lift and unless the pilot takes immediate action the aircraft will descend. By adding more power, the engine makes more noise and entices the Lift Pixes back onto the wing and lift is restored.
Simple.
Last edited by Arty Fufkin; 12th May 2007 at 14:01. Reason: spooling
you with the most accurate and easy to understand answer so far. Well done, have 5 house points and a free pizz at the next dining in night!
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I am sorry I don't agree with you Arty about the use of lift pixies. Lift pixies are really only good for civilian aircraft as they usually require payment in cakes, flowers or nice thoughts. These are usually sourced either from the in-flight catering companies, or provided cost-free by the passengers who fly on civilian carriers.
As you can see this would not work well within the operational military environments that the RAF work in. RAF In-flight baking is not renowned for the "light and fluffy texture" that the lift Pixies demand and the availability of in season flowers might be a problem in desert operations, also nice thoughts may be hard to find during times of active operations.
As you can see this would not work well within the operational military environments that the RAF work in. RAF In-flight baking is not renowned for the "light and fluffy texture" that the lift Pixies demand and the availability of in season flowers might be a problem in desert operations, also nice thoughts may be hard to find during times of active operations.
Lift Pixies work out of area too !!
I'm sure we have all noticed a shortfall in aircraft performance when operating in theatres such as Iraq or Afghanistan. Some bloke once tried to explain it all to me by using terms such as ISA Deviation, Density Altitude, Pressure Altitude etc......... amateur!
Don't worry, Lift Pixies can be found all over the world and can co-exist with the most miserable of people as is proved by the commercial sucess of Ryanair.
The reason for the slugish performance of aircraft in operational theatres is as follows :
Lift Pixies don't wear shoes (obviously) hence they easily fall off wings in turns. Your average airframe parked in the sun gets pretty hot so its unsuprising thst the little fellas are reluctant to jump onto the wing's surface. The only way to entice them onboard is more noise hence more power. Either that or put up with a longer take off run.
Hope that helps.
Don't worry, Lift Pixies can be found all over the world and can co-exist with the most miserable of people as is proved by the commercial sucess of Ryanair.
The reason for the slugish performance of aircraft in operational theatres is as follows :
Lift Pixies don't wear shoes (obviously) hence they easily fall off wings in turns. Your average airframe parked in the sun gets pretty hot so its unsuprising thst the little fellas are reluctant to jump onto the wing's surface. The only way to entice them onboard is more noise hence more power. Either that or put up with a longer take off run.
Hope that helps.
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Arty
As you seem to be PPrune's resident Lift Pixie SME, could you explain how they work in helicopeters? How do they ever manage to stay on the fast-whirling blades - do they perhaps wear little velcro booties? Obviously from what you have already said, the traditional teachings of rotary P of F are just pure bunkum...
Yours in anticipation,
ProStu
As you seem to be PPrune's resident Lift Pixie SME, could you explain how they work in helicopeters? How do they ever manage to stay on the fast-whirling blades - do they perhaps wear little velcro booties? Obviously from what you have already said, the traditional teachings of rotary P of F are just pure bunkum...
Yours in anticipation,
ProStu
Last edited by ProfessionalStudent; 12th May 2007 at 18:24.
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It is an oft quoted "twitcher" observation that many bird species tend to scatter in panic when a "goroundoscope" approaches.
Perhaps they know something............
Perhaps they know something............
Helicopters
Pro - Stude,
Thank you for your enquiry regarding so called "helicopters." I must admit that I don't agree with them personally, never have!
As for how they manage to thrap themselves into the air, I'm afraid i simply have no idea. It is safe to say that no self respecting Lift Pixie would be seen dead clinging onto one of those ungodly contraptions. I can only imagine that some form of static-charge repulsion is responsible. Either that or the work of the devil.
Hope that helps
Dr A Fufkin
Thank you for your enquiry regarding so called "helicopters." I must admit that I don't agree with them personally, never have!
As for how they manage to thrap themselves into the air, I'm afraid i simply have no idea. It is safe to say that no self respecting Lift Pixie would be seen dead clinging onto one of those ungodly contraptions. I can only imagine that some form of static-charge repulsion is responsible. Either that or the work of the devil.
Hope that helps
Dr A Fufkin
Last edited by Arty Fufkin; 12th May 2007 at 19:19. Reason: grammar
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I think you will find that the complex aerodynamics involved in rotary flight do not rely on pixie power, but on the sheer will of the occupants for it to remain in the air
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As I said earlier lift pixies are not suited to military operations, however Thrust demons are. They are a nasty bunch who require payment in blood or souls something that most airlines would not be able to supply.