Downwind turn discussion
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how many can hang vertically on the propeller thrust?
Helicopters do it every day on every flight, and not only hang, but climb.
Helicopters do it every day on every flight, and not only hang, but climb.
if an aircraft accelerates there will be an incremental difference seen between the body frame and air mass frame due the change in AoA. The point I obviously did not make well enough is that, there will be no acceleration sensed in the longitudinal axis, with respect to either the body or air mass plane in an aircraft making a turn from upwind to downwind while maintaining a constant ASI
What's an "air mass plane"? Is it an aeroplane made out of thin air? Maybe made from a mass of air? Can you make it plain for the masses? We're not on the same plane, that's plain! It's Sunday, I'm off to mass. Err!
It beautifully sums up the total confusion some seem to have about a simple concept when they try to over-think it and end up over complicating it when trying to explain their confusion to others!
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It beautifully sums up the total confusion some seem to have about a simple concept when they try to over-think it and end up over complicating it when trying to explain their confusion to others!
If we all stick to using the ASI to tell us how fast we are flying instead of looking at the ground all will be well.
But:
I do look at the ground to judge height - a necessity for a field landing in a glider, and indeed for the variation in the circuit between windy and still days.
Megan
I really do think that you need to go back and read your posts throughout this thread and see what impact they have had on the readers. The exasperation registered by some contributors should make it obvious to you that many of your comments have added nothing to the general understanding of this subject.
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And therein lies the risk. It is quite natural for a pilot to want to monitor his/her height, position and trajectory over the ground. But unless he/she is aware of the wind conditions and fully understands the effects that this will have on his/her ground speed and direction, he/she may misinterpret the signs. If this causes him/her to and bank too far into the turn or use too much rudder, the consequences may be fatal.
However why is a well-banked turn dangerous in a Cessna (for example) and not in a glider? Simple answers only please!
In gliding though we're taught that a well banked turn increases the stall speed but decreases the spin risk. It reduces the speed differential between the wing tips, and the pilot is less able to over-rudder. In a slow, shallow turn, particularly if being blown downwind or running low on height, the pilot may be tempted to try and use rudder to increase the rate of turn.
I was doing a standard BGA exercise in a Puchacz (which has a reputation for spinning) a couple of weeks ago. At 20, 40 and 60 degrees of bank the glider was stalled and the airspeed noted. Stall speed increased significantly at 60 degrees, but it showed no inclination to spin. A slow shallow turn with a little extra rudder and it won't hesitate.
I was doing a standard BGA exercise in a Puchacz (which has a reputation for spinning) a couple of weeks ago. At 20, 40 and 60 degrees of bank the glider was stalled and the airspeed noted. Stall speed increased significantly at 60 degrees, but it showed no inclination to spin. A slow shallow turn with a little extra rudder and it won't hesitate.
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A well banked turn is no more dangerous in a Cessna than a glider, provided the ball is kept in the middle. But glider pilots are more familiar with turning at high bank angles and what to do with the rudder.
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A well banked turn is no more dangerous in a Cessna than a glider, provided the ball is kept in the middle. But glider pilots are more familiar with turning at high bank angles and what to do with the rudder.
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And I can tell you that more often than not, the average ga pilot, when invited to demonstrate a steeply banked turn (at altitude) during a biennial flight manages about 30degrees of bank maximum. Glider pilots have to be comfortable at much higher angles for continuous turning in thermals.
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It wasn't me that first invited the comparison between Cessna pilots and glider pilots. I'm assuming we meant Cessna to be shorthand for 'the average ga pilot flying for leisure on a ppl'.
Brian Abraham, as you appear to be wading in to defend some of the mixed up nonsense that megan comes out with, and you boldly state that this mysterious "air mass plane" that megan refers to is:
Please explain EXACTLY what - in your own words - an "air mass plane" is, and what its relevance - if any - is to this discussion about aircraft turning in 3D space.
I'm sure the Wiki page you referenced will help to remind you that a plane in this context is a 2 dimensional flat surface. How does any such 2D plane become an "air mass plane", and what EXACTLY is the significance of the "air mass" label given to any such 2D plane? What relevance is any "AIR MASS" to any of the infinite number of 2D planes in space? What is this "Plane of reference" you take his "air mass plane" to be?
Probably, both megan and you are confusing the notion of a 2D PLANE with an inertial FRAME of reference, which could be a valid starting point for a sensible discussion to start from. Other than both words happening to rhyme, there is no connection between any such inertial FRAME of reference and any PLANE that you and megan seen keen to claim has any relevance.
A few contributors to this thread make accurate, valid scientific statements and give equally valid answers and facts; Keith W and PaulisHome to name just two. They are outnumbered by others who like to mix up jumbles of half-truths and myths using occasional precise scientific terms in inappropriate, inaccurate and confusing ways, which unfortunately spreads their own confusion to others.
Unless you can justify your bold claim that you cannot understand how the term "air mass plane" could be confused by anybody, then you are placing yourself squarely in the latter category, along with megan.
Keith W and PaulisHome are correct in what they say. In contrast, the repeated offerings from megan contain little of substance, and much of it is simply wrong. How odd that you should come out in support of some of megan's muddled nonsense, whilst apparently ignoring Keith W's very valid reprimand to megan that their contribution adds little, if anything of value to the discussion.
Edited - it appears that Brian Abraham has chosen to delete his post in support of megan's nonsense rather than try to explain his theories about a "Plane of reference" being an "air mass plane". Pity, I was looking forward to the explanation.
Plane of reference I take it to be. Don't know how anyone could assume anything else from my reading
I'm sure the Wiki page you referenced will help to remind you that a plane in this context is a 2 dimensional flat surface. How does any such 2D plane become an "air mass plane", and what EXACTLY is the significance of the "air mass" label given to any such 2D plane? What relevance is any "AIR MASS" to any of the infinite number of 2D planes in space? What is this "Plane of reference" you take his "air mass plane" to be?
Probably, both megan and you are confusing the notion of a 2D PLANE with an inertial FRAME of reference, which could be a valid starting point for a sensible discussion to start from. Other than both words happening to rhyme, there is no connection between any such inertial FRAME of reference and any PLANE that you and megan seen keen to claim has any relevance.
A few contributors to this thread make accurate, valid scientific statements and give equally valid answers and facts; Keith W and PaulisHome to name just two. They are outnumbered by others who like to mix up jumbles of half-truths and myths using occasional precise scientific terms in inappropriate, inaccurate and confusing ways, which unfortunately spreads their own confusion to others.
Unless you can justify your bold claim that you cannot understand how the term "air mass plane" could be confused by anybody, then you are placing yourself squarely in the latter category, along with megan.
Keith W and PaulisHome are correct in what they say. In contrast, the repeated offerings from megan contain little of substance, and much of it is simply wrong. How odd that you should come out in support of some of megan's muddled nonsense, whilst apparently ignoring Keith W's very valid reprimand to megan that their contribution adds little, if anything of value to the discussion.
Edited - it appears that Brian Abraham has chosen to delete his post in support of megan's nonsense rather than try to explain his theories about a "Plane of reference" being an "air mass plane". Pity, I was looking forward to the explanation.
Last edited by pilotmike; 14th Feb 2017 at 11:48. Reason: Brian Abraham's post has since been deleted
Has anyone mentioned 'Momentum' yet..?
Consider two cases... Airplane flying North at ASI of 100 kts with 99 kt tailwind, and second Airplane flying North at 100 kts into a 99kt headwind.
This makes the ground speeds 199 kt and 1 kt, respectively.
The first has considerable Momentum (Mass x Velocity) the second has almost none.
So if they are both disturbed by a similar force (a gust of wind, or a control movement.) The first aircraft will be deflected from its course by one or two degrees, whereas the second will change its direction vector by a very large amount.
.
Consider two cases... Airplane flying North at ASI of 100 kts with 99 kt tailwind, and second Airplane flying North at 100 kts into a 99kt headwind.
This makes the ground speeds 199 kt and 1 kt, respectively.
The first has considerable Momentum (Mass x Velocity) the second has almost none.
So if they are both disturbed by a similar force (a gust of wind, or a control movement.) The first aircraft will be deflected from its course by one or two degrees, whereas the second will change its direction vector by a very large amount.
.
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No they won't. Because they only have the momentum of their individual 100knots in their individual air mass.
You will see things differently because you are still on the ground.
I'm goin up the pub!!!!
You will see things differently because you are still on the ground.
I'm goin up the pub!!!!
Hi Boss Eyed... No I think you have got it completely the wrong way round...
If you are going North downwind at GS = 199 kts a small control input could change your course by one degree... (your still effectively going North.)
But going into wind at Ground Speed =1 kt, the same control input could make your course change by 90 degrees (i.e. you fly west.)
In both cases your heading remains about the same, but the Course works out very differently.
For those not familiar with the Jargon, 'Course' is the track over the ground.
'Heading' is the way the front of the aircraft is pointing.
.
If you are going North downwind at GS = 199 kts a small control input could change your course by one degree... (your still effectively going North.)
But going into wind at Ground Speed =1 kt, the same control input could make your course change by 90 degrees (i.e. you fly west.)
In both cases your heading remains about the same, but the Course works out very differently.
For those not familiar with the Jargon, 'Course' is the track over the ground.
'Heading' is the way the front of the aircraft is pointing.
.