it was said before that the change of the direktion horizontal vers vertical cost an extra portion energie.... so the calculation was not much/exact valid it was under a limit value view, and yes it is possible to climb with an bird and change Ekin into Epot... (in detail the pressure on the water-surface deep under the bird has to rise a little bit, and the earth will change her position on her way round the sun also a liiiiitle bit)

a calculation just to control the plausibility of datas

and due to the lots of lessknown faktors (AoA, Cl, Cd, Cm, temp. density, spezific weight, reynold.....) it is just a practician desicion of the calculator if he will more talk over the marginal conditions or over the basic applications

and yes the used calculations of Ekin has some mistake in turbulence conditions with changes in the airspeed, this mostly cost a second portion of energie....

One last admission from my side to end this energy discussion:
When I simply enter the 275 kts into the simplified formula of an E6B calculator I get 467,5 kts as TAS.
When calculating considering the Mach values I get between 475 kts (M0,80) and 490kts (M0,82) for an ISA temperature of -54,3° (ISA standard atmosphere at 35000 feet).

Depending on the real temperature this value can vary significantly and therefore the TAS can probably have been easily been 460kts as well as 500kts. We shouldn't read too much into it without knowing OAT.


Mach dependent TAS:
a0*M*sqrt(T/T0)
where
a0: speed of sound at S/L
M: actual Mach number
T0: ISA temperature at sea level in Kelvin
T: actual temperature.

henra, you're making a mistaek....
Your aircraft has mass/inertia, so it will not be instantly dragged along by your 100 kts tailwind. Your airspeed will now be 0 kts. Not a healthy situation....
Read up about windshear (not exactly the same, but similar).

That is EXACTLY the point I was trying to make.

It was my point about change of state of the reference system in reply to his remark:
My point being that for the problem of loss of effective Ekin to trade for altitude it makes no difference if you have a headwind of 100kts while flying 100kts, i.e. being at a standstill with regard to the ground and the wind suddenly stopping or
you are flying at 100 kts and are suddenly hit by a 100kts tailwind. In the latter case you have no airspeed left to fly after being hit by the wind either.

Seems my explanation was a bit brief last time..


Edit:
To give another example:
You have a Microlight tied to the ground and the wind is blowing at 70kts. What will happen if you cut the ties?
It will lift off and start to fly backwards with regard to the ground. You have traded speed for altitude at that moment. And it had kinetic energy with regard to the air at that moment although with regard to the ground it didn't. It's all about relevant reference systems....

henra,
Sorry, I dropped into the Ekin discussion halfway. I agree with your point of view.

At post #657 HN39 made the following "tongue in cheek" comment -I don't think that everyone picked up on what he said, but the discussion over KE principles has been interesting and informative.:ok:

henra;
I believe the forecast temperature was -46°C at FL350, and I wouldn't be surprised if it was even warmer where AF447 was, e.g. -42/-43°C.

Thanks mm43 !

That would give us a TAS of 489kts at M0,80 and 500kts at M,82.
Looking at the setting of the RTLU at the time of the beginning of UAS a Mach speed of roughly M0,80 seems likely. So we would be back somewhere around the 490kts and ~4000ft.

a) PROBE-PITOT fault seems to be the relevant ACARS, by logic priority, over ADR faults which should have been compiled under the same ATA 341.
b) ADR fault is not self detected (there is no ADR internal failure) ; monitored channels (airspeed, Mach,...) are declared faulty by FMGCs and FCDCs, but they are still displayed.

@HazelNuts39
Yes, that is also one of the aspects I considered, though did not have enough time to dive into. Though 2 aspects might be relevant in this:
- Speeds are relatively low, glider speed and "jetstream".
- An important control target is the constant airspeed. Small rudder changes and/or differences in thermal-absorbing might hide the effects in speed changes.
- An experiment might be to circle around and measure the pitch angle and rudder usage during the circles. I would expect a somewhat sinus shaped change in rudder/pitch position.

Let me change the challenge a little:
- Land your glider with a airspeed of 30.25 m/s and a headwind of 30 m/s (just enough to move a little bit related to the ground).
- The presumed TAS based Ekin would be 0.5xmx915 =458 m J
- The moment the glider does touch down, everything becomes ground speed based and the ground speed based Ekin would be 0.5xmx0.25x0.25 = 0.03 m J.

Where did the Ekin of (458 - 0.03) m J go ?????

It got nowhere. The only energy that got converted into heat was the 1/2*m*(0,25m/s)^2 during braking on the ground.
With regard to the air the remaining 1/2*m*(30m/s)^2 is still in the glider. Being fixed on the ground it is effectively being towed through the air at 30m/s by the ground with regard to the air. See my example of the microlight.
If the wind breezes up by 1m/s to 31 m/s it will lift off again. Or push it forward at 1m/s and it will take off.
If the air is still you will have to push at 31m/s. Big difference for you, no difference for the glider for its ability to lift off and fly. The difference for the glider is how it will move in relation to the 'other' reference system, i.e. the ground.
That's why aircraft prefer to take off and land against the wind. Mother Earth gives a certain amount of kinetic energy to fly to the Aircraft for free. For the same Aircraft you need less energy (thrust*distance) to leave the ground. And upon landing you have to dissipate less energy in your brakes. Still in between you were equally able to fly as if you took off and landed with the wind.

The trick is that you need to understand that for an Aircraft once it has left the ground, the movement of the ground below is totally irrelevant for the ability to stay in the air. And it stays irrelevant until it contacts the ground again. In between only its relative movement through the air is relevant.

I did, but I don't have all the answers, and formulas, and figures, at my fingertips any more...

To stir up the discussion, what about a 'breakdown' of the Ekin of a Fieseler Storch (or similar) flying at about 50kts in a 50kts headwind ?

@CONF iture

Sure, but the remark is, the airspeed should change when the inertial speed stays the same, whereas the airspeed is perceived to be constant (which in effect isn't, but this is masked by other factors).

@rudderrudderrat

Unfortunately it isn't. See my example about the landing glider, a few posts back. The airframe can't be the reference point for conservation of energy.

New report
 

The BEA to publish another report on Friday?
Link

@henra

Yes, the ability to stay in the air is a function of airspeed.
The inertial Kinetic energy is not a function of airspeed, a very subtle difference......

So the amount of speed which can be bled of is related to the min. airspeed to stay in the air. The actual amount of Ekin released is depending on the absolute speed compared to the fixed reference. The reference should at least be earth (-surface). (And when you get convinced of that, you will also understand the earth rotation stuff).

@ChristiaanJ

Let's extend this: Headwind 49.99 kts and the Storch is having a collide with a tower, best would be just above a platform.

What would happen: A very gentle little bump against the tower and then the subtle drop/land on the towers' platform. Nothing bent.

How to enter a deep stall
 

I am amazed at all the kinetic energy and OAT and such discussion here for last two days.

The profile of AF447, as we know it, and regardless of control laws or pilot inputs, resembles the classic manner of getting the Viper into a deep stall. You simply climb at a fairly steep attitude, fairly level roll attitude, and at low AoA until you run outta energy, then sit there and watch the jet try to nose over too late. AoA increases rapidly, and with little or no "nose down" pitch moment available from the flight controls, you are there!!

The jet's "protections" (or limits, as I prefer) are fooled. We simply fly past the jet's control authority to provide the so-called "protections". Worse, and in the case of the Airbus, we have a myriad of reversion "laws" that could cause the crew to do something worse than just sit there and hold attitude/power. The overspeed warning is what I am concerned about, as that could explain either pilot or computer commands, or both.

I refuse to believe that the Airbus is a poorly-designed jet from the aerodynamic aspect. I truly believe you could exceed the mach "protections" until reaching maybe 0.95M or so with no ill effects. I truly believe that you could fly the jet at 10 or 15 degrees AoA. I truly believe you could pull 3 gees without the wings falling off. I truly believe the jet has exceptional lateral stability, or we would not see a proflile with a slow rotation versus a tendency to enter a spin.

What I do see is an embedded "autopilot" influence that changes control laws depending upon flight phase ( and Viper had some of those, but not to the extent of the Airbus). I see confusing cockpit warning/caution indications. I see no firm "hang your hat on the jet's capabilities" control law that the human crew can use when things go to hell in a handbasket. Worst of all, I see no aspect of the system that acknowledges loss of air data and simply reverts to a basic control law while the crew and HAL figure things out.

You'd be disappointed. The point is - if the wind speed is horizontal and constant in magnitude and direction, there is absolutely no effect on the airplane, except that the center of the circles moves over the earth surface at the speed of the wind. Except for that, the airplane flies perfect circles at constant airspeed, bank angle, pitch angle, angle of attack, and control surface positions.

Another matter entirely is a vertical wind component, or changes of wind speed or direction, but let's keep that for next year ...

the Old Chestnut ,wind effect when circling
 

That Old Chestnut

I had it beaten out of of me when learning pattern B instrument flying on a Harvard "circling upwind or downwind has no effect on your airspeed as you are only flying/ circling with respect to the airmass"
I was convinced I had to keep adjusting power as I went round the 360 degrees maintaining an exact height
However we were also warned to be careful turning downwind near the ground for fear of stalling due to visual illusions of speed
In gliding, circling on the ridge, if one correctly maintains airspeed there seems to be a need to speed up/nose down turning downwind, and there is surge of lift as you turn back into the headwind .Though the detail effects are distorted by the changes of updraft and windspeeds near the hill .
Nevertheless there is a loss of height turning downwind, and a regain height as you turn into wind.
It is also interesting how the angle of bank changes as you fly elliptically over the ground while performing a supposed perfect circle in the airmass?
Swirlyflier

Hello henra
And that was the only Kinetic Energy that it had left, when it crossed the virtual border between the two reference systems - air, and ground.

Then, when I am standing watching kids playing in the yard, under a breeze of 0.5m/s, I must have a 0.5m/s corresponding Kinetic Energy.... even though I don't move... ;)

The glider at this time does not move, so it has 0 kinetic energy. (relative to the ground, just to be accurate).

Kinetic Energy goes beyond Aerodynamics, and thus, similar examples are abundant in various other fields of the Dynamics, some involving wheels and legs, instead of air, and wings....

For instance the example of a train at a certain speed, and a passenger walking on the train: if the passenger hits an object on the train, his pain is going to be relatively little, when compared with the pain he would have if he hit somehow, an object on the ground - classic comedy films with guys walking on the top of the train, while the train goes under a very low overpass bridge, come to mind.

The passenger Kinetic Energy relative to the train is given by his walking speed, measured by the little pain of hitting an object on the train, while his Kinetic Energy relative to the ground, is augmented by the train's Kinetic Energy, measured by considerable more pain, and possible destruction in the second case..

With that, back to the glider example, the Kinetic Energy corresponding to the 30m/s speed wind, is the air's Kinetic Energy, not the glider's.

The glider on the ground, is like the passenger off the train - no Kinetic Energy from the air, none from the train. Put the glider on the air - push it to make it fly - it's like having the passenger back on the moving train.

All of these examples contain momentum, and inertia aspects, which may add to the fun, or to the confusion....

After these examples it is also clear that it's good to keep the Energy Conservation equation pure, in its General and Universal aspects, which transgress the specifics of the Dynamics fields, like Aerodynamics.

Hi Dutch M,

I didn't say use the aircraft airframe as the reference - use the moving Air Mass as your inertial reference frame.
I seem to remember a certain Mr. A. Einstein wrote a special paper about it.

Your first sentence reminds me of D.P.Davies: "If you can choose between stalling and something else, choose something else" (IIRC). IMHO your second sentence needs to be qualified: At M.82 the airplane can be considered stalled at about 8 degrees, at M.6 (the speed at apogee, see the graph I posted recently) at about 11 degrees, whereas 15 degrees may be just flyable at Mach 0.2 - 0.3.

Thanks for this update, and recent posts with sharing more info on the TAS calculations.

I have not checked, but it is probably the case, that you've calculated with an unchanged TAS at FL375 of 390knots....

Hi,

Gums
Domaine-de-vol-A330.pdf

Yeah, 'nuts, the stall AoA for the Airbus may have something more to do with mach than I am familiar with. Most jets I flew stalled at an AoA, whether supersonic or subsonic. The supersonic regime is more complicated, but big deal. Only problems I ever saw with a subsonic design had to do with shock waves over the wings, ailerons and HS that caused neat things like control reversal and a nose down "tuck" that required you to reduce speed real quick using spoilers, speed brakes, reduced thrust, etc.

My point is that it is possible to "zoom" at a "comfortable" gee and AoA and then run outta energy and control surface authority, passing thru all the "limits" and "protections" that the system is supposed to provide. We proved the point back in the late 1970's in my little jet.

Can't get the download JC. Will try later. Is the point that the Airbus has crappy aero characteristics?

Respectfully,


P.S. I agree that avoiding a stall is a sound procedure. We can worry about pieces falling off later due to high speed or gee.

Hi,

Weird ... Mediafire is reliable host and work great here ...
You can try this multi links host ... (make your choice :) )
Multiupload.com - upload your files to multiple file hosting sites!

But are not NAV ADR FAULT and faulty ADR two different species ?

• NAV ADR FAULT is the result of an ADR internal failure or a manual switch OFF.
• faulty ADR provides erroneous information but is not an ADR failure.

Le Figaro set the table to kill the pilots a second time :
Do not expect anything different from the BEA on Friday ...

Hi,

Not particulary the "Le Figaro" but instead the "aviation expert" of "Le Figaro" I quote Fabrice Amedeo
Note that this journalist is firstly a leasure sailor :)
Maybe better for him to comment BEA Mer reports ....
BEAmer : Bureau Enquêtes Accidents de mer : Rapports d'Enqutes

So it looks like the report will confirm that the intial climb wasn't briefed to the Captain on his return and that the word 'stall' was not uttered, as the Chief Engineer stated some time back. I hope that the 60kt inhibit of the stall warning gets the attention it deserves.

You are semantically right concerning internal/external faults but what matter is that those erroneous informations won't be used by the flight systems but still be displayed to the crew for information and troubleshooting. All relevant systems based on erroneous outputs would be declared inop during the fault isolation sequence (AP/FD, A/THR, PROT, RTLU, WINDSHEAR, SPD LIM, TCAS)

Concerning FMGCs and FCPCs monitoring, the effect is a rejection of the faulty sources (channel); in our case, all 3 ADRs are declared faulty by them and rejected. There is no cockpit circuit breaker at probe-pitot level and what could be displayed is a fault on ADR pannel; one may want to turn it off.

Until all ADRs are turned off, the stall warning based on Alpha is still working (if at least one AOA channel is not declared faulty), but it's computed differently as this function use a Mach correction and Mach is replaced by a default value. On the other hand, the computed stall warning based on Low Speed (VSw) is lost. Concerning Overspeed warning, it is lost as this function is based on faulty ADR channels, as well as VMax which is not displayed.

You need to keep your reference axes the same, moving at the same constant initial velocity then there is no change in Kinetic energy - but OK "v" is no longer airspeed, if windspeed changes.

WRONG. Of course you have to make assumptions about constant windspeed, thrust=drag, g constant etc but correctly applied the maths/physics works, in 3-d vector co-ordinates - until you get close to speed of light!

And back to the point, the reference points quoted for AF447 are consistent with a zoom-climb trading speed for altitude. AF447 did not get caught up in 7000ft/min updraught where an external force supplied the work done to increase the gravitational potential energy.

Note - a zoom climb was discussed on these forums as soon as the wreckage position reported, way before the BEA confirmed it - it was the most obvious way AF447 could shed horizontal speed so quickly and end up so close to its last transmitted position.

Indeed, to confirm, the drag curve consists of profile drag + induced drag + Mach drag. The absolute value of the sum of these can indeed increase below a minimum drag speed, particularly approaching a stall, but between the normal cruise and maneouvring speed unlikely to increase much if any at all.

== DutchM ==

I really dont think you need ground speed for calculating those energy exchanges, TAS is fine surely... Unless you state you are allowing for windshear of thermal gusts , which we aren't are we, because we can't can we, because we don't know the figures do we. So we do the basic steady state air-mass TAS calculations, and bear in mind some variations may occur in practice... but if we're within the right cricketpitch, then fine.. that's what engineers do, get in the right region, check they've got the order of magnitude correct and then use some commonsense to make further deductions and corrections!

===========
Possibly worth consideration (as airline pilots seem increasingly unfamiliar these days with hand-flying through heavy thermal activity, wicked windshear or terrible turbulence - ?)

Flying in a +ve going thermal, with increasing x and z wind-vector components, glider pilots can find that stick back for extended periods is quite OK, with an almost unstallable feel to the aircraft (for reasons possibly explained some while ago)
Conversely, when this 'free energy' phase is exited, you are effectively in heavy adverse windshear, known to some as 'going over the falls' for obvious reasons! It's a horrible feeling, as if your very lifeblood was being drained... and if you don't respond, it may well be. (I've heard hang-gliders say they've had to hand-stand on the bar to prevent -ve 'g' tuck during some exits from the back-side of thermals.
Now, I'm definitely not comparing a 300 kt IAS airliner with an 80 lb hang-glider, even though the latter does have a sensible AR (8 to 10), span as big as a Spitfire and several hundred square feet of wing.

Only by strong pitch stability or quick and considerable ND inputs, is a very quiet & lonely sensation avoided, with a subsequent stall or wing drop...

So, it is interesting that a strong right wing drop seems to have had to be countered early on in this series of events, around when the climb started (strong and persistent wing drop, is frequently one wing entering quite different air than another). Then after quite safely holding NU (and a high angle of attack) for some time, we have the new THS* position... and a quite telling one I'm sure the report will atest to.

It is this * that our (hypothetical) glider pilots wouldn't have had to deal with... just a firm but controlled ND to accelerate back down through dirty colder slow air (!)

The way I read Dutch M's reference to Ek and Ep exchange, is that the Ek - or speed vector - need to have a vertical component (direction of height), for the energy conservation exchange to take place. Which is CORRECT.

With no vertical component, there is no height gained/lost, and no potential energy change, or exchange. An object that goes horizontally, from zero speed, all the way to a certain speed, will not get potential energy regardless of how slow, or fast.

Hi gums;

IIRC, Tubby Linton provided a set of AoA graphs two or three threads ago, (now ancient history, at this pace!), repeated below, which show quite clearly, the effects of Mach, and of slats/flaps at lower speeds.

I had a long and very productive discussion with HN39 in the third thread earlier this year on "stall AoA". Davies discusses AoA's of 15deg and very early (Private Licence time in the '60's), I was left with the impression that "the" stall angle for transport aircraft was "15deg" (or so), altitude and Mach not considered; of course, this is not so but I never encountered a correction to that impression in my career...high altitude stalls were simply never done and never discussed, I think, with legitimate reason given limited sim time and expanding items to cover over the decades.

One can see the effects of extended slats and flaps and the AoA's are in accord with Davies' "approach case". IIRC he doesn't discuss high altitude stall in detail, even in his section on "jet upset". With increased Mach, I learned that the stall AoA reduces substantially - in the neighbourhood 4deg, not 15!, etc, as can be calculated from the tables below which are employed by the A330 FWC [Flight Warning Computer] to trigger the Stall Warning in other than Normal Law. In Normal Law, the Stall Warning will trigger, but only at an AoA > 23deg, as described in the chart.

HN39, it was indeed Davies who said, "...choose any other alternative...", etc.

PJ2


http://www.smugmug.com/photos/i-Qr5x...Qr5xMMw-XL.jpg

Hi airtren,

We are not considering ballistics.
Aeroplanes convert P.E. to K.E. on every descent by simply using the wings.

I think PF's initial ss back is starting to gel into the 'climb command', once again. Nothing about BEA suggests that is so.

As to Harry Mann's 'wing drop', as far as it may be the result of airmass flow, it may well indicate a very robust 'up elevator'.

Between the first NU and the second STALL WRN. , only Nose Down inputs are mentioned.

Roll excursions are mentioned. The a/c is climbing rapidly, rolling, and losing energy.

At the 'top' of climb, the AoA decreases, (6?), and there are STALL wrns.


Harry. Climbing, unstable in Roll (with corrections), and losing energy, would not the a/c STALL with increasing loss of altitude due loss of energy, regardless of pitch commands? as the a/c loses energy in climb, the AoA is affected as much by arrival at apogee as Pitch, perhaps more?

In a serious updraft, the correct input, (perhaps other than none!) might be Nose Down? Hold Altitude? Lose as little as possible?

BEA report seems to suggest that PF was not reacting to the climb. Too many here seem to assume the PF was "along for the ride".

Again, I think the source of the STALL was timed to the loss of the autopilot and autothrust. If in an uncommanded climb, of course the PF would not advance the Throttles. He would input ND, and BEA have not said he did not.

With the loss of 'g' at the top, TOGA and "back pressure" relief would be correct? Especially if associated with STALL WARN?

Hi ruderruderrat,
An airplane descent implies a speed spacial vector that has a vertical component (vertical speed component), and so the Ep to Ek conversion takes place. And that is true in general with any descent, involving airplanes and wings or not.

If the airplane flies flat, horizontally, the vertical speed component is NULL, and there is no Ep change/exchange. An Ep to/from Ek conversion starts as soon as there is a non-NULL vertical speed component (up, or down) of the speed vector.

If unaccelerated?

The aerodynamic braking during airplane controlled descent consumes the gain of Kinetic Energy, resulted from the Ep to Ek conversion, resulted from the loss of height/elevation. Slowing down for landing, means decreasing the Ek. What is left of the Ek, at touch down, is consumed (converted into other forms of energy) further through aerodynamic and mechanical braking.

The Ep to Ek conversion takes place regardless of controlled descent, or free fall. The difference is that in a free fall the Ek gain (or most of it, to be accurate) is not consumed/converted until the very end of the descent.

The airplane case is not different than a car descending a hill, from the generic Ep to Ek conversion perspective.

A car's free hill descent, will mean gain of speed - Ek not consumed. A controlled descent at constant speed, or decreased speed, requires different degrees of braking. The braking is consuming the Ek gain through friction, converting into Thermal Energy - brakes are quite hot at the bottom of the hill.

Stall warnings started 15 seconds before the top of the climb, at 0210:51, when Alpha reached 6° (BEA).
0210:05 = 0210:05 => 275 kt; FL350; Alpha was about 3° (estim.)
0210:16 < 0210:50 => 215 kt; FL375; Alpha was about 4° (BEA)
0210:51 = 0210:51 => Stall Warnings; Alpha was about 6° (BEA)
0211:06 ~ 0211:06 => 185 kt; FL380; Alpha was about 16° (BEA)
During those 15 seconds at the beginning of the stall warning sequence (stall warning only stopped 35+ seconds later, after 0211:40)... the AOA increased by 10°.