Mallard Down in Perth
Joined: Jul 2005
Posts: 555
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From: South Island
Imagine a 150kt wind (constant airmass, no gusts or wind shear).
Imagine a hot air balloon sitting in that wind. A far as the pilot is concerned there is no 'wind'. It's completely calm sitting there in the balloon. The ground is rushing by at 150kts.
Imagine a Cessna doing orbits around the balloon.
The Cessna is also not feeling the 'wind', other than the 90kts or so that it's flying through the airmass at.
There is no increase or decrease in IAS as it completes the orbit - a nice round orbit completed with a constant angle of bank.
No falling out of the sky.
Yes, it's a bit of a mind bender the first time one thinks about it - hopefully at the PPL training stage.
That is the "downwind turn" concept regarding the visual illusion due to changes in the relative movement of the ground.
Wind changes and wind shear are a completely different issue.
Imagine a hot air balloon sitting in that wind. A far as the pilot is concerned there is no 'wind'. It's completely calm sitting there in the balloon. The ground is rushing by at 150kts.
Imagine a Cessna doing orbits around the balloon.
The Cessna is also not feeling the 'wind', other than the 90kts or so that it's flying through the airmass at.
There is no increase or decrease in IAS as it completes the orbit - a nice round orbit completed with a constant angle of bank.
No falling out of the sky.
Yes, it's a bit of a mind bender the first time one thinks about it - hopefully at the PPL training stage.
That is the "downwind turn" concept regarding the visual illusion due to changes in the relative movement of the ground.
Wind changes and wind shear are a completely different issue.
Joined: May 2007
Posts: 191
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From: Australia
There was a sou'-wester (left crosswind), which meant he turned through true downwind on to base. It was also a bit gusty at the time. I live up the road from where it happened and we were on our way down to the river just prior to the accident.
Joined: Dec 2000
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From: Sydney NSW Australia
The Mallard wasn't "turning downwind", but was turning "into wind", was it not?
Joined: Jun 1999
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From: Queensland
There are quite a few on this thread who obviously think that flying in moving or stationary air is irrelevant to the flight of the aircraft. This is a reflection of what they have been taught and their opinion that very experienced low level pilots are idiots.
I was interested to read a reference to wind shear (highly relevant) and Regulated Ground Speed, a concept selected by significant airlines, mainly prior to glass cockpits. Certainly used by Ansett, TAA & Qantas.
I was interested to read a reference to wind shear (highly relevant) and Regulated Ground Speed, a concept selected by significant airlines, mainly prior to glass cockpits. Certainly used by Ansett, TAA & Qantas.
Joined: Jun 2006
Aviation Qualifications: ATP+Mil
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From: Terra Firma
There are quite a few on this thread who obviously think that flying in moving or stationary air is irrelevant to the flight of the aircraft. This is a reflection of what they have been taught and their opinion that very experienced low level pilots are idiots.
I was interested to read a reference to wind shear (highly relevant) and Regulated Ground Speed, a concept selected by significant airlines, mainly prior to glass cockpits. Certainly used by Ansett, TAA & Qantas.
I was interested to read a reference to wind shear (highly relevant) and Regulated Ground Speed, a concept selected by significant airlines, mainly prior to glass cockpits. Certainly used by Ansett, TAA & Qantas.
Joined: Nov 2008
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From: The Shire
An airbus has ground speed mini. It calculates the current wind compared to the tower wind and changes the approach speed to maintain a constant energy level with reference to the ground.
It works quite well in ordinary circumstances. It's a right pain in the backside in gusty strong wind conditions. Particularly if you're high and turning into a strong headwind on final.
As for physics, mallards and flaps. If you don't have a lot of experience, you have a lot of money and you buy an aeroplane which requires some experience, but lots of ongoing recurrency training - the result is you'll probably make a spectacle of yourself one way or another.
It works quite well in ordinary circumstances. It's a right pain in the backside in gusty strong wind conditions. Particularly if you're high and turning into a strong headwind on final.
As for physics, mallards and flaps. If you don't have a lot of experience, you have a lot of money and you buy an aeroplane which requires some experience, but lots of ongoing recurrency training - the result is you'll probably make a spectacle of yourself one way or another.
Joined: Apr 2008
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From: Australia
The physics are exactly the same, irrespective of whether there is no wind, there is a constant wind, or if the wind is gusting and variable.
The different winds makes for differing conditions, not different physics. The laws of motion are the same, therefore the physics must be too!
The different winds makes for differing conditions, not different physics. The laws of motion are the same, therefore the physics must be too!
Joined: Jun 2006
Posts: 265
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From: Brisbane
Exactly, Nev.
The confusion from some low-level pilots arises from the fact that the aircraft only knows about the air-mass it is flying in, but the pilot can't see that air-mass, and so is navigating and assessing aircraft performance by reference to the ground.
Rate of climb or descent won't change whether turning upwind or downwind.
Angle of climb (relative to the ground) will change, and this is why the low-level pilot "feels" that his aircraft is under-performing or over-performing respectively.
Radius of turn (relative to the ground) will also be affected, hence tempting the untrained to increase angle of bank turning downwind, reducing aircraft performance potentially to the point of stall, simply attempting to achieve a ground-based goal.
These matters of physics should be compulsory learning for low-level endorsements, but obviously they are not.
Perhaps we have uncovered one reason for QF mandating Year 12 for it's applicants. Although I don't know that completing Year 12 necessarily prepares one to understand the above. It should be part of the pilot training syllabus for all pilots, and particular emphasis for low-level endorsements.
The confusion from some low-level pilots arises from the fact that the aircraft only knows about the air-mass it is flying in, but the pilot can't see that air-mass, and so is navigating and assessing aircraft performance by reference to the ground.
Rate of climb or descent won't change whether turning upwind or downwind.
Angle of climb (relative to the ground) will change, and this is why the low-level pilot "feels" that his aircraft is under-performing or over-performing respectively.
Radius of turn (relative to the ground) will also be affected, hence tempting the untrained to increase angle of bank turning downwind, reducing aircraft performance potentially to the point of stall, simply attempting to achieve a ground-based goal.
These matters of physics should be compulsory learning for low-level endorsements, but obviously they are not.
Perhaps we have uncovered one reason for QF mandating Year 12 for it's applicants. Although I don't know that completing Year 12 necessarily prepares one to understand the above. It should be part of the pilot training syllabus for all pilots, and particular emphasis for low-level endorsements.
Joined: Jun 2006
Posts: 265
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From: Brisbane
A great thought experiment for the doubters goes as follows:
You are flying an aircraft in level flight at 60 knots in a 30 knot headwind.
You decide to fly an orbit, still in level flight, at 60 knots, at 30 degrees angle of bank.
You put in the 30 degrees angle of bank, and increase power to maintain your 60 knots. You also increase your pitch attitude to maintain your altitude.
During the complete orbit, will you have to change your power or pitch attitude due to the wind?
You are flying an aircraft in level flight at 60 knots in a 30 knot headwind.
You decide to fly an orbit, still in level flight, at 60 knots, at 30 degrees angle of bank.
You put in the 30 degrees angle of bank, and increase power to maintain your 60 knots. You also increase your pitch attitude to maintain your altitude.
During the complete orbit, will you have to change your power or pitch attitude due to the wind?
Joined: Jun 2006
Aviation Qualifications: ATP+Mil
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From: Terra Firma
Yes I poorly worded that statement. Physics is universal. What I meant to say is that the equations of motion are different. The classic example is the marble rolling across a frictionless rotating disc. Viewed from an inertial frame of reference it travels in a straight line at constant speed (Newton's First Law). But viewed from the non-inertial frame of reference (the rotating disc) it travels in a curved path. To describe the curved path a 'fictious' force (Coriolis) is invoked. Two very different equations of motion describing the same event.
Last edited by Bleve; 13th February 2017 at 15:15.
Joined: Dec 2010
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From: Goolwa
I think the missing link with all of the above is Time and Rate of Change. When doing a normal turn i.e 60secs to turn180deg (rate 1) or even 30secs for 180deg, the rate of change is comparatively slow so, in a steady mass of air, effectively reducing any inertial effects to zero (velocity vectors and all that). Whereas with wind shear and gusts the rate of change is rapid, over a couple of seconds, therefore mass and inertia will be more prevalent.
Certainly IF you could somehow manage to turn your aircraft 180deg in 2 seconds inertia would have an effect. And conversely if windshear/gusts occurred over 30-60 seconds you wouldn't really notice them.
Certainly IF you could somehow manage to turn your aircraft 180deg in 2 seconds inertia would have an effect. And conversely if windshear/gusts occurred over 30-60 seconds you wouldn't really notice them.
Joined: Jul 2008
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From: Australia
Possibly the pilot was trying to work out the physics involved in a downwind turn and in the process completely forgot to put the flaps out which is more than likely what really caused the accident.
Joined: Jun 2006
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From: Brisbane
Possibly the pilot was trying to work out the physics involved in a downwind turn and in the process completely forgot to put the flaps out which is more than likely what really caused the accident
The understanding of the physics of low flying takes place prior to one's flight.
The application of such physics happens in-flight.
There is a difference.