Aviation Mythology and Misconceptions
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I think the highlighted part of that myth is most dangerous when believed by those who are airline VPs because Daddy was a millionaire and bought them a Harvard or LSE MBA.
One of my favourites which is particularly prevalent in corporate aviation - the suit at interview glibly announces
"in our company, safety is our absolute priority"
- then they make a derisory daily freelance offer contingent on you first paying for your own type-rating, ditching training, fire-fighting certificate, hazardous cargo certificate, and annual recurrent, and be available 24/365 at one hour notice, and then add that if you don't accept the conditions, there are "plenty of others who will"....
"in our company, safety is our absolute priority"
- then they make a derisory daily freelance offer contingent on you first paying for your own type-rating, ditching training, fire-fighting certificate, hazardous cargo certificate, and annual recurrent, and be available 24/365 at one hour notice, and then add that if you don't accept the conditions, there are "plenty of others who will"....
hawk 37
One definition of Power is that it is the 'rate of doing work'.
Work = Force x Distance
If the aircraft's engines do not apply their force (thrust) through a distance, then no work is being done. Ergo, no power is being produced.
(To be honest, I've never heard this 'myth' being expounded anyway, but then I should get out more...........)
If an aircraft is not moving (stopped on a taxiway for example), then its not producing any power.
Work = Force x Distance
If the aircraft's engines do not apply their force (thrust) through a distance, then no work is being done. Ergo, no power is being produced.
(To be honest, I've never heard this 'myth' being expounded anyway, but then I should get out more...........)
Originally Posted by wilyflier
Just you try the difference between a downwind turn and an into wind turn when you are near enough to the ground to detect it, i.e. on a hang glider.
Its no myth. Its all about energy states between aircraft and ground.
Its no myth. Its all about energy states between aircraft and ground.
Originally Posted by Clandestino
Never heard of this one. Methinks original myth was "It is under no circumstances safe to cross the pond on three out of four engines"
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Youngsters who love flying (nowadays) think they'll satisfy this desire and become an airline pilot. (Better to get another job and become involved with an aerobatic/tourer.)
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Youngsters who love flying (nowadays) think they'll satisfy this desire and become an airline pilot. (Better to get another job and become involved with an aerobatic/tourer.)
Temperature of fuel has no effect on volume uploaded
Obviously the mass of fuel and hence the total calorific content of the fuel per unit volume will vary with temperature. Are you making assumptions about the fuel measurement, i.e. the bowser's flow measurement device also takes account of fuel density, or the aircraft's fuel quantity indicating system is making an adjustment for fuel density?
Apart from the actual expansion of the aircraft fuel tank with temperature, its volume will stay the same. The volume of fuel that can be put into it will stay the same if we assume no tank expansion, but the mass will depend on fuel density.
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Eckhard,
Heat energy, and kinetic energy (exhaust) come to mind.
Power plants use turbines to produce electrical power, however of course, like the stopped aircraft, the power plants are not moving.
I'm sure the quote/myth is really meant to mean "there is no power (ie energy) gained by the aircraft" (except possibly warmer brakes).
However I've seen it referred to as "the aircraft is producing no power", clearly incorrect.
Hawk
Heat energy, and kinetic energy (exhaust) come to mind.
Power plants use turbines to produce electrical power, however of course, like the stopped aircraft, the power plants are not moving.
I'm sure the quote/myth is really meant to mean "there is no power (ie energy) gained by the aircraft" (except possibly warmer brakes).
However I've seen it referred to as "the aircraft is producing no power", clearly incorrect.
Hawk
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Killer downwind turn.
This one came about because of slow-speed aircraft turning downwind shortly after takeoff, while simultaneously climbing through a stiff wind gradient. Obviously the climbing into a tailwind will decrease your airspeed, resulting in a possible stall (and the turn itself will further degrade your speed).
Likewise, another glider hazard is the 'clutching hand' effect of descending to land and transiting from a stiff headwind into a nil headwind area (over the top of trees, for instance, into the calm region in front of the trees). As soon as you lose your headwind, you lose your airspeed and drop rather rapidly (feels like a hand dragging you downwards).
But obviously if there is no wind gradient, the windspeed and direction is irellevant to your flight control.
.
This one came about because of slow-speed aircraft turning downwind shortly after takeoff, while simultaneously climbing through a stiff wind gradient. Obviously the climbing into a tailwind will decrease your airspeed, resulting in a possible stall (and the turn itself will further degrade your speed).
Likewise, another glider hazard is the 'clutching hand' effect of descending to land and transiting from a stiff headwind into a nil headwind area (over the top of trees, for instance, into the calm region in front of the trees). As soon as you lose your headwind, you lose your airspeed and drop rather rapidly (feels like a hand dragging you downwards).
But obviously if there is no wind gradient, the windspeed and direction is irellevant to your flight control.
.
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In hindsight, my comment was made too simply. I should have included, volume required.
Exactly this-
We need fuel by mass, despite delivery by volume. I flew with a fella who had difficulty accepting density values. When I tried to explain to him, it went straight over his head. His 'assumption' generally being that there must be more fuel on board, despite what the gauges say, because the book says the tanks hold x lbs.
I hope that makes sense.
Exactly this-
Originally Posted by mechta
The volume of fuel that can be put into it will stay the same if we assume no tank expansion, but the mass will depend on fuel density.
I hope that makes sense.
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Thank God windspeed has nil to do with lift. Wind shear is a lie. Does it matter then, if it is the a/c or the airmass doin' the turn?
I think elapsed time has sumpin' to do with it?
I think elapsed time has sumpin' to do with it?
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downwind turn
Sorry checkerboard
I doubt you have spent any time doing such manoeuvres in a low mass aircraft with a high wind speed and airspeed ratio, where it is obvious.
Its NO illusion
The visible effect is that you have to lose height as you turn downwind or your airspeed decays.
Even more noticeable is how suddenly you regain that airspeed and height as you turn back into wind
There is another factor involved which could explain it, but I'll leave that for you to find out from your gliding experience
Strata,
(I think you got your take-off wind gradient inverted)
Sorry, forget I said that, I misunderstood that you were climbing through gradient on take off, but actually you referred to wind gradient climbing down wind. In the cases I quote the aircraft were descending downwind, no engine power
Funnily enough I detected the biggest changes occur During the turn , not once youve settled straight downwind
I doubt you have spent any time doing such manoeuvres in a low mass aircraft with a high wind speed and airspeed ratio, where it is obvious.
Its NO illusion
The visible effect is that you have to lose height as you turn downwind or your airspeed decays.
Even more noticeable is how suddenly you regain that airspeed and height as you turn back into wind
There is another factor involved which could explain it, but I'll leave that for you to find out from your gliding experience
Strata,
(I think you got your take-off wind gradient inverted)
Sorry, forget I said that, I misunderstood that you were climbing through gradient on take off, but actually you referred to wind gradient climbing down wind. In the cases I quote the aircraft were descending downwind, no engine power
Funnily enough I detected the biggest changes occur During the turn , not once youve settled straight downwind
Last edited by wilyflier; 4th Nov 2011 at 21:48.
Wilyflier, You could be doing your downwind turn through some hilltop rotor, or getting your inboard wing into lower, slower moving air. The wing only 'sees' the air surrounding it. As you can see the ground directly beneath you from a hang glider, it is very difficult to avoid slowing the glider down as the ground rushes below at a rate of knots.
Sliverstrata is correct in saying that climbing into a tailwind can decrease your airspeed. It is the same effect as decending into a headwind,only the wind gradient is has the opposite direction as your height changes.
If you watch, from the ground, a free flight model aeroplane circling, as it drifts downwind, it will appear to slow down as it turns into wind and speed up as it turns down wind. If you were to observe the same model from above, for example, from a hot air balloon, it would appear to fly a perfect circle.
Sliverstrata is correct in saying that climbing into a tailwind can decrease your airspeed. It is the same effect as decending into a headwind,only the wind gradient is has the opposite direction as your height changes.
If you watch, from the ground, a free flight model aeroplane circling, as it drifts downwind, it will appear to slow down as it turns into wind and speed up as it turns down wind. If you were to observe the same model from above, for example, from a hot air balloon, it would appear to fly a perfect circle.