opposite aileron? wouldn't cause a problem, unless you have stalled the wing..

Conceded.

Another point to make is the aileron goes to mushy feel which further adds to the distress and confusion, rather than triggering an alert that a stall then spin is about one or two seconds away.

Sadly this pilot was just not aware of what was happening and the alerts that were being supplied were not registering.

Forgive my inability to express myself here, but there was enough indication, that something needed to be done and the pilot just did not twig, forgive that expression, that all sorts of hell was less than five seconds away, unless he took prompt corrective action.

unless you have stalled the wing.. exactly. Now the opposite aileron instead lifting the wing as it normally does, further slows that wing increasing the stall and wing drop. The pilot is going a bit fuzzy in the head and doubts what is happening is real, the aileron is mushy and does not work which further adds to the fuzz. If the pilot goes to full extent with aileron, that makes the wing drop further .. by now ... the pilot is confused and sadly doomed by the unexpected.

Which I suppose leads to my previous of doing training with flying near the stall for a hour or three with gliders and doing a few dozen spins ... thus a stall will be instantly recognised and corrected.

If you've got full aileron applied in an attempt to prevent the roll, therefore it's against the stops - so how can it be "mushy"?

Could I also suggest that flying a glider near the stall would be very different situation to a heavier and highly wing loaded type such as the Mallard?

So many posters here with psychic powers!

:rolleyes:

The ATSB will be contacting you soon!

There is a very important demonstration for glider pilots who winch.
Nose up 40 degrees.
simulated cable break.
nose to recovery attitude of 30 degrees nose down.
initiate turn without waiting for airspeed to recover using aileron and balancing rudder whilst looking over your shoulder at the airfield.
Add more rudder to "increase" the turn rate.
Nose starts dropping
Heave back on stick
Still killing pilots but not so many as part of the annual flying checks in the UK.

As to ground speed verses airspeed...spun a paraglider three times now on a steep slope with the wind partially across the slope giving both upwind and downwind beats added to wind gradient....and I've got fifty years of flying...there but the grace of Dog...

Said this before on another thread. The Americans have/had a saying.''Watch him spin, watch him burn, he took off bank in a low speed turn''.
Ha this effect demonstrated to me in a T.21 Sedburgh when I was in the Air Training Corps in England. When I went on to a PPL I NEVER forgot that demonstration.
ULTRALIGHT. It WILL stall the wing if already very close to the stall!.

JEM60, I was taught that when I was very young, it was then, "hold off bank in a gliding turn and you will surely crash and burn." I believe it related to the fact that the Austers, Tigers and Chipmunks all had Gypsy engines turning back to front from modern engines. Also some of the Auster variants had heavy wooden cruise props, one of which I recall, mk 3? would smartly turn sharply if you closed the throttle without leading with a lot of rudder. You would have to try very hard to get into trouble but I suppose the possibility existed that you could end up with crossed controls at low level combined with a windshear. I was young and silly then and I am still here, so it couldn't have been too bad but all of those old sayings obviously existed because someone had died proving them.

A few accidents of note https://aviation-safety.net/database...ard/statistics

Total of crashes: 15
Total of fatalities: 59
Worst crash: Dec 19, 2005 with 20 fatalities

From http://www.baaa-acro.com/

ATSB - Collision with water involving Grumman American Aviation Corp G-73, registered VH-CQA, 10 km WSW of Perth Airport, Western Australia on 26 January 2017

Investigation Title - Nothing much at present.

Perhaps I should say mass and density instead of mass and drag...but you will appreciate the relationship between the two.

The answer to the downwind turn lies in whether the aircraft has high mass and high density at one end of the scale or has low mass and low density at the other end of the scale.

Consider a rubber-band-powered balsa wood toy aircraft of a few grams turning downwind...yep, no easily measurable change in IAS. But a huge change in groundspeed.

Now consider a ballistic bullet fired in a straight line through a multitude of wind velocity changes. When the bullet experiences a headwind or a tail wind change, does the IAS of the bullet remain fairly constant or does the groundspeed remained constant?

Those who have experienced operating high mass and high density aircraft at low airspeed and rapid maneuvering at low altitude in high winds have a tale to tell...but only to those who might listen.

Vincent Chase's comments about his flying in a fully loaded cropduster indicate that he has experienced the phenomena causing him to crash. But he survived and has learned the bitter lesson of the downwind turn. He has a tale to tell...but only to those who might listen.

Good luck to the other Sky Gods.

In a previous life I use to drop bombs using a manual aiming system. The bombs pretty much fell to earth in accordance with the laws of Newton.

Unfortunately, the air mass velocity at the altitude at which they were released was always different from the many changes in wind velocity that the bomb saw on the way down. This would cause the bomb to miss the target. Therefore we had to compensate with an offset aim point by calculating an average wind velocity.

The offset was determined by applying the average wind velocity to the drift acceptance factor of the weapon. Heavy and high density weapons had a smaller drift acceptance factor than lighter and low density weapons which were obviously more affected by wind velocity changes.

Be careful when you think that you know everything about aviation...

I'm not really convinced that the aircraft in question was looking to bomb anything but I'm option to a reasonable argument.

Neither. In target shooting, it's all about ballistic coefficient vs velocity - and nothing to do with mass.

Once fired, a projectile's BC (and longitudinal axis stability, which affects BC) - otherwise known as its drag profile - will determine how quickly its velocity and kinetic energy are lost, as its mass remains constant.

A headwind will cause the projectile to strike the target lower, as it has more air mass to cover, more time to reach the target, more time for drag and gravity to act. A tailwind will move the point of impact up. A crosswind will move the POI to the side and down, as it increases the distance the projectile must cover. In all scenarios, the groundspeed differs in relation to nil-wind conditions.

Compare two projectiles of equal mass and velocity, but high and low BC ("pointy" versus "blunt" bullets). The more aerodynamic projectile is less affected by wind (in all conditions), and it's POI does not shift as much . . . which, as you can see, has nothing to do with mass.

Neither does gravity, for that matter - if a feather were as aerodynamic as a bomb, they would both fall at the same speed.

Where I think some are getting confused with mass and inertia is in relation to changing constants.

Why is a turn into downwind at low level a potential hazard? Because of the wind-direction. No, not the direction of the constant air mass, but the direction of any gusts or other changes in wind velocity (vectors) which are more likely to happen close to the ground due to friction and other variables, and are generally (but not always) in line with the prevailing wind direction.

If you are turning into a constant tailwind at a constant airspeed, and that wind suddenly gusts, your airspeed will instantly decay in direct proportion to the suddenly increasing tailwind component (vector). This is where mass (inertia) affects how long it takes for airspeed to recover and stabilise.

An aircraft in a constant air mass will not suddenly change direction in relation to the earth if that air mass suddenly changes direction. It takes time for the aircraft to accelerate, decelerate or otherwise change direction in line with the new constant (vector) due to its inertia (which has everything to do with mass).

This is basic aerodynamics that we learned in PPL. Maybe we should all read some Bob Tait?

Bob Tait's Aviation Theory School - Wind Shear - Bob Tait's Aviation Theory School Forums

Totally agree...

...and vice versa...a rapid air mass direction change...or a rapid aircraft direction change.

ed. (my bold)

Thanks for the help in explaining.

Cheers!

Re... it was then, "hold off bank in a gliding turn and you will surely crash and burn." I believe it related to the fact that the Austers, Tigers and Chipmunks all had Gypsy engines turning back to front from modern engines.

HA HA HA ...!!!

NO CHEERS....NOPE....NONE AT ALL...!!!

Wot utter B/S......:{:=:sad:

Except the aircraft eventually does change direction with the changing air mass, and not the other way around. After all, the air mass is supporting the aircraft - not vice versa.

Imagine a motorcycle being ridden in a straight line on an aircraft carrier. If the aircraft carrier turns left, so does the motorcycle (in relation to the earth) - even though it's still driving straight. Now, put the same motorcycle on a runway and ask the rider to make a left turn. The motorcycle again turns left (in relation to the earth) - but the runway hasn't moved.

In both cases, the rider feels centrifugal force as the motorcycle banks left due to their combined inertia and needs to use the same leaning force into the same rate of turn to remain astride - even when he's riding "straight".

So you'll forgive me if I don't fully understand what other forces are at work to change the direction (air speed) of an aircraft in a constant angle of bank in a constant air mass.

Assuming drag, lift, thrust and weight don't change in a constant turn (in a constant air mass and density), what other force is there to upset the lift-weight/drag-thrust equation to cause velocity (air speed) to suddenly change?

Thank you ExFSO for your thoughtful and well reasoned comment.

So you have two bomb shaped objects of identical shape. One is made of graphene and filled with feather fibres (ie really light) the other normal alloys and explody-bits in the middle.

Both are dropped from a B1. Which hits the ground first?

There is a great video on youtube of a feather and bowling ball being dropped in a vacuum and both falling at the exact same speed (as you would expect with no air resistance).

In your example CS that's a hard one to work out. With inertia, air resistance etc all factored in I suspect the heavier bomb first but I am not really sure.

Someone took me on on this subject after the MH17. If you have any doubt about which falls faster, get a basketball filled with concrete and a balloon the same size and roll them off a tabletop with your feet below. (Do this at home, not in a vacuum satellite testing silo with Brian Cox, nor on Mare Ibrium with David Scott).

But this is a digression from the real task at hand. I posted it as it does show that there are a lot of poor analogies, mistaken arguments and confused points scattered through this thread (not directed in particular about the poster above whom I quoted).

We've had standard turns in uniform parcels of air mixed with zoom climbing turns, windshear, non uniform air movement, gradient winds.

People talking about frames of reference, maybe, but its the terms of reference of the question that need clarifying before any answer.

You can't disprove the downwind turn theory (or lack of) in a uniform parcel of air by using examples of climbing turns in gradient wind.

Do FW students get taught to fly attitude in the same way as RW students?

Seems to have worked well in avoiding dropping out of ETL for all these years.....

In my post #207, I said...

In relation to the currently discussed vexing question of an aircraft turning downwind, I should really have said:

Inertial mass is earth/time dependent for frame of reference.

I hope I didn't annoy anyone out there who have an in-depth knowledge of the theory of Inertial Reference Units systems fitted to aircraft.

I apologise for oversimplifying.

Ballistic Coefficient is the ratio of sectional density to coefficient (aerodynamic) form. It's effectively a combination of streamlining and inertia, which are both used to overcome the forces of wind resistance (friction). The reason a feather and a bowling ball both fall at the same rate in a vacuum is because gravity is a constant in relation to the earth's mass (9.8ms/s) acting on all atoms (regardless of mass): https://web.stanford.edu/dept/news/p...ity990825.html

Once wind resistance (friction) enters the fray, then something is needed to overcome that resistance for an object to continually accelerate at 9.8ms/s - an equal force to the opposing wind resistance.

A body in motion will not alter its course unless acted upon by an external force.

The body in motion has kinetic energy - 1/2 mass x velocity squared. Therefore, a proportional force is needed to slow its acceleration from 9.8 ms/s. That force increases as the kinetic energy of the object increases. However, the forces of wind resistance (friction) increase with air density (more atoms per equal volume = great frictional force) and the surface area of the moving object they are acting on. The square-cube law dictates that volume - and all other things being equal, mass - increases faster than surface area. So if two moving objects have the same density and form (both spherical, for example), the larger object will have more kinetic energy in relation to wind resistance. The same equation can be applied to two moving objects of the same form but different densities (mass/volume).

That answers your question as to why greater density of equal form can overcome the frictional forces of wind resistance when accelerated by the same force (gravity).

My question is, if two objects - regardless of size and mass - are moving within a constant air mass, and are not subject to wind resistance or any other physical force within that air mass, what force will cause those objects to alter their velocity?

Did anyone else here go out to the low flying area on a windy day and conduct "Constant radius turns about a fixed point on the ground" training as part of their CPL?

Apart from the obvious real life applications it was also a good way to train people to not kill themselves in the "air/ground interface".

You know, teach them not to be fooled into thinking their ground speed was actually their airspeed and other such strong illusions.

As usual, this has gone totally away from the very sad event that claimed 2 lives. If I was to take note of half the crap that is being spruiked on this thread I'd stop flying now and hand in my licence. One thing's for sure.... so many faceless experts, not all, and at least one admitted he wasn't a pilot, wonder how many others there are?

It's true that inertial mass can be framed in terms of the earth's rotational axis - I concede your point. However, both the aircraft and its supporting air mass are subject to the same forces (coriolis, centrifugal, gravitational), and are therefore in the same inertial frame of reference to the earth. To all intents, the supporting air mass is the frame of reference for the aircraft.

That aside, if I read correctly, what you are saying is that, as soon as an aircraft changes direction, there is a change in inertial frames of reference between the aircraft and its supporting air mass. If so, then that inertial change must be measurable in relation to the air mass, and therefore show up as a change in airspeed.

I do not doubt there is such a change.

But in terms of the measurable difference between the two frames of reference of the aircraft and air mass, is it enough to stall a wing?

We are talking about an aircraft flying at circuit speed at 1000', and not the Space Shuttle, after all.

OK, megan posted this in another thread. IMO, it appears to be exactly what happened on Australia Day.

In defence of this thread, if we can't learn from others' mistakes, we're destined to make the same.

Nope I cant recall doing that though my Oz CPL would have been back in the 80's. But did some glider thermalling at 200-300 feet sometimes in wind. Was only grounded once when allegedly below tree top height but I was a teenager back then. And the many glider cable break training flights were good practice for low level tight turns with wind to consider.

Chris I would imagine glider flying would give you an intimate knowledge of exactly what is actually going on.

That you or others have not come across this in the training phase certainly clears up some misconceptions I had.

Another exercise was to handrail along a line feature at low level (maybe a bit lower than 200ft this time) and become proficient at overcoming the lag in controls and inertia of the aircraft. Becomes quite apparent when you come to a bend in said line feature and try to follow it. Need to act a fair way ahead of time to make that bend.

flywatcher; I suggest that you think very carefully about the main thrust re ExFSO Groffo's post.

What he was alluding to was the your proposition that the aforementioned engines rotating in the reverse to modern engines may have some significance.

The proposition is false! The direction of rotation of the engine has no significance! Or, as Griffo puts it; BS!

Griffo; I really wonder how many posters on this thread really are Pilots, let alone have CPL's!:hmm::ugh::*

And for reference; The old saying amongst WWII RAAF Pilot trainees went;
I saw him crash, I saw him burn! He held off bank in a Gliding turn!

Related to me many times by my late Father; 39814 Baum; Ronald Wilhelm, Warrant Officer 1, 461 Sqn RAAF. 1st Solo in DH 82 AN 624 August 9th 1943 at No 1 EFTS Parafield South Australia.

Never had a cpl, sorry, not even a ppl, but I used to have a glider pilot's license.
We were never taught to fly circles around a fixed point in strong wind, except we tried it, to show us that that wasn't the way to do it.
We were taught to fly constant bank and speed, and didn't feel the "downwind turn syndrome" no matter the speed or bank angle, which was just what the practice was all about, even though the wind was enough to "park" the K13, about 63 km/h. yes, we flew metric, it is close to 35 kts.
We didn't use winch start but a trusty Super Cub for launching.

Yes, it was part of my training syllabus for either the NZ PPL or CPL (can't remember which). It was also part of the check ride. This was in the early 1990s.

We followed line features and flew constant radius turns at 200' as well as setting up for precautionary landings. All good fun and educational.

Ironically, P51D, you have not stated which side of the argument you support and you would probably find that both sides are reading your post, nodding sagely, and saying to themselves "yes, yes, quite right!" :ok:

All I would say is that those who believe that a turn from headwind to tailwind in a steady airmass (i.e., no gusts/turbulence/shear) will cause a loss of airspeed should be preparing their Nobel Prize acceptance speech because their assertion, based on only the best anecdotal "data" of course, invalidates all of the hard work that physicists have been doing for the last hundred years! Einstein would have been very interested to learn that one of his two main postulates on which he formulated the special theory of relativity, that the laws of physics are identical in all inertial frames of reference (i.e., that there is no preferred frame of reference), has been proved wrong by some half literate "pilots" on the internet.

No-one is saying the laws of physics change from one frame of reference to another. But there are forces that act on an inertial mass in relation to its position in reference to the earth (and other gravitational fields), so that when an aircraft changes direction in a constant air mass, the two inertial masses (air mass and aircraft) initially diverge in terms of reference. The sum of the difference can be calculated, but makes no appreciable difference to the air speed of an aircraft close to the earth's surface. That is my understanding.

Virtually There - There is not such thing as an INERTIAL MASS. :ugh: There is just MASS. Good ole Newton came up the relationship - F (Force) = M (mass) x A (acceleration).

(Einstein refined it for relativistic speeds to include a correction factor based on the speed of light)

You can chuck the Inertial term out the window, its bulls.t

Lift is the Force that keeps the wings aloft, and the same thing that generates the turn.

Lift (Force) is generated by the air moving over the wings. FULL STOP. In a steady state air mass, the aircraft wings do not know if that airmass is doing 0 knots or 200 kts relative to the ground.

You can do 360 deg orbits all day, clockwise and anti clockwise in a steady state jet stream and you will never see one iota of IAS difference when turning.

Its not that hard.

Quote:

---

What he was alluding to was the your proposition that the aforementioned engines rotating in the reverse to modern engines may have some significance.
The proposition is false! The direction of rotation of the engine has no significance! Or, as Griffo puts it; BS!

---

Pinky, if you take off in a tail dragger with American engine, right rudder. If you take off in a early aircraft with Gipsy engine, left rudder. The fin is offset in opposite direction. In all over paddocks, circuits were left hand. Think about it before you call BS

If you are implying I don't have a CPL I can assure you I have, with about 20,000 hr attached to it, some thousands at or below 200ft low speed small radius turns over fishing nets so I have a vague understanding of the effects of wind at low level.

Quote:

---

Related to me many times by my late Father; 39814 Baum; Ronald Wilhelm, Warrant Officer 1, 461 Sqn RAAF. 1st Solo in DH 82 AN 624 August 9th 1943 at No 1 EFTS Parafield South Australia.

---

Related to me by my late father, first solo 1938, Cirrus Moth, Mascot, before my first landplane solo, Tiger Moth VH-AZP, Bairnsdale 1958

Well I did not know that there was a requirement to have a minimum ppl but preferred Cpl to comment!

This high standing opinion of many pilots is what kills so many.

The amount of times over my +30 years in aviation I have been asked by very high time and including ATPL pilot , what does this do or how does this work on a basic system is amazing. Many tech logs/MR,s entries cleared with "tested no fault found" should also include "Pilot trained to use it properly".

It is simple, this Mallard stalled. There is no evidence of any external or mechanical factor that assisted in the stall. There are whiteness and video footage in abundance - The ATSB should not need a year to do this report.

P.S. sorry to all the PPL, CPL & ATPL holders that do know others in the industry also know how aircraft work and fly.

Condolences to those poor kids.

As Clare Prop said "Looking at the size of the display box, how did anyone think a 5700 MTOW kg aeroplane could fit into that area? "

The pilot also appeared to obey the 600 meter rule for 'built up' areas, with his downwind track being well out over the water and further reducing his available space.
Questione: Would a PPL ever be trained to do a right hand tear drop timed circling approach, to enable a tighter radius by turning into wind, away from the obstructions in the CDB and away from the low sun ? Would the air display organiser want to see a plan including that, for what was probably one of the few low level displays (a landing) of the day ?

I posted the following back at #147. Flying helicopters in the offshore world it was not uncommon to have 60 knots of wind when taking off from a platform. Climb speed in our particular aircraft was 75 knots and the turn to downwind while holding climb speed was visually spectacular if not seen previously. Ground speed went from 15 knots into wind to 135 knots downwind, all the while maintaining 75 knots IAS. The point is, the aircraft doesn't care what the wind is, and if you are flying by reference to instruments you would have no idea what the strength of the wind is, or indeed, if there is any wind, save for the fact that you already have 60 knots airspeed prior to commencement of the take off.

It was said :E that in sports mode you could make the turn at 60° of bank for a really spectacular visual illusion. The airspeed didn't move, and the ball remained centred. How can all this be? Where were all these inertial effects? Why didn't we crash and burn?

I'm not sure how to even answer that. If you don't understand the difference between a non-inertial (accelerating) mass and an inertial (moving or stationary, depending on frame of reference) mass, then it is likely me who will be :ugh: in trying to explain.

But here's the tip (if you don't know how to use Google - that's a good start): lift opposes gravity - gravity is a (relatively weak) force that acts on all mass and varies with the formula

Fg = M1M2m/R2

Where gravitational force is the sum of Mass 1 multiplied by Mass 2 multiplied by the gravitational constant (m = 6.67 x 10 to the minus-eleventh) divided by distance squared.

Note the "distance squared" part - any time Mass 1 and 2 diverge, the gravitational forces between them change exponentially.

Secondly, kinetic energy is relative to where it is being measured. That is to say, it is relative to the frame of reference.

If the frame of reference is Planet Earth - which is circling the sun at 30km/s, in a solar system travelling at 230km/s, in a galaxy moving at 5833km/s in a universe that may or may not be moving (we think it spins, hence why it is flat) - and you are flying along in your little 172 at 110kt (51m/s), what is your kinetic energy?

EK = 1/2m V2

How do you measure the velocity in the above equation without a frame of reference?

BTW, if you'd actually read my posts, you'd realise that I completely agree with everyone else that there is absolutely no discernible difference in airspeed (induced drag aside) when turning in any direction in a constant airmass . . . but that doesn't mean there is no difference. ;)

My argument with FlexibleResponse is that inertial frames of reference have no real bearing on air speed turning upwind, downwind or cross wind - the velocity change is so miniscule as to be insignificant

Virtually there - I think we are virtually there on agreeing. Thank you, for clarifying your position.

This is the key point in this thread discussion.

"Masses have inertia", that is a better way to say it, then talk about "inertial masses". "Inertial frames of reference" is the best way of saying it.

Yes you are right. But the differences you are referring to are the ones due to relativity, and the relativistic adjustments aren't going to be the cause of a stall in a Mallard.


ps (I have a BSc in physics) :)

That's OK, I have a CPL :} That means I know more about physics than Newton. Apparently. After all, he never flew ;)