A320 Wind Indication on PFD during Takeoff-Roll
Oh come on fellas...
It's on the ND but the direction CANNOT be correct, it will jump around depending on the sensed track and heading changes on the roll.....
Half the time the left and right ND wind displays are different on the Airbus anyway!! Not just a little either.....
It's on the ND but the direction CANNOT be correct, it will jump around depending on the sensed track and heading changes on the roll.....
Half the time the left and right ND wind displays are different on the Airbus anyway!! Not just a little either.....
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Careful study of this in my twighlignt years of flying (now retired but active in th sim) revealed that, as CS says above, there is no way the ADIRSs can work out the S/W between 100kts and getting airborne. All you get is a head or tail component which is influenced by 'drifting' left or right of the C/L.
The subject is further confused by th fact that the Thomson/Thales/L3 sim that I sometimes use does display the S/W while still on the RW while the CAE sims only display the head/tail component.
Careful monitoring of the ND wind indication during asymm flying will reveal all sorts of 'strange' winds brought about by unbalanced flight which the IRSs see as drift.
I hope this helps.
mcdhu
The subject is further confused by th fact that the Thomson/Thales/L3 sim that I sometimes use does display the S/W while still on the RW while the CAE sims only display the head/tail component.
Careful monitoring of the ND wind indication during asymm flying will reveal all sorts of 'strange' winds brought about by unbalanced flight which the IRSs see as drift.
I hope this helps.
mcdhu
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One poster says this is displayed >100kts. Some questions: I can understand the curiosity of how this vector is calculated, but why are you looking at it? ATC have given you the wind in the takeoff clearance. During takeoff roll you PF is concentrating on the centreline and far end of the runway and speed. Rudder input will tell you which side the wind is coming from.
So my question is, what useful information, at 100kts, is this vector giving you? I also ask the question as to why AB created it rather than inhibit it until wheels up?
So my question is, what useful information, at 100kts, is this vector giving you? I also ask the question as to why AB created it rather than inhibit it until wheels up?
I also ask the question as to why AB created it rather than inhibit it until wheels up?
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I would pick that up as a stagnation in IAS. Not by looking at the wind vector.
Read the manuals. Does anyone's manual suggest looking at the wind vector during takeoff? Mine doesn't, but it does tell me what to do if the IAS stagnates.
Don't make **** up.
Read the manuals. Does anyone's manual suggest looking at the wind vector during takeoff? Mine doesn't, but it does tell me what to do if the IAS stagnates.
Don't make **** up.
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If you knew there was a risk of a microburst and you started picking up a massive tailwind, it may make you think twice about continuing the T/O?
As for the aircraft displaying wind direction with any degree of accuracy while on the ground - it's poppycock!
Interesting OP.
The only wind data available to the aircraft on the runway is pitot pressure and air density. So, it can only calculate a head or tail wind component. As for wind direction, my guess is that it must take an average measurement of the rudder angle trend which would enable it to give an estimation of wind direction left or right. Combine that with the head/tail component calculation, and you can give an estimate of the wind vector.
I notice the A380 has AoA style vanes mounted vertically on the nose - presumably to actually measure the crosswind?
@RAT5 On take-off, when looking in to confirm and crosscheck your airspeed reading at 100 kts, it's always worth a quick glance to the wind vector to confirm that the tower wind was reasonably correct. I had a very interesting departure from the Caribbean once because the wind they gave us was incorrect.
A tailwind greater than 10 kts would clearly be a cause for concern, but when spotted at 100 kts, the T/O can be abandoned. (Well ANY unexpected tailwind not allowed for is a potential problem of course, as we almost found out that day)
The only wind data available to the aircraft on the runway is pitot pressure and air density. So, it can only calculate a head or tail wind component. As for wind direction, my guess is that it must take an average measurement of the rudder angle trend which would enable it to give an estimation of wind direction left or right. Combine that with the head/tail component calculation, and you can give an estimate of the wind vector.
I notice the A380 has AoA style vanes mounted vertically on the nose - presumably to actually measure the crosswind?
@RAT5 On take-off, when looking in to confirm and crosscheck your airspeed reading at 100 kts, it's always worth a quick glance to the wind vector to confirm that the tower wind was reasonably correct. I had a very interesting departure from the Caribbean once because the wind they gave us was incorrect.
A tailwind greater than 10 kts would clearly be a cause for concern, but when spotted at 100 kts, the T/O can be abandoned. (Well ANY unexpected tailwind not allowed for is a potential problem of course, as we almost found out that day)
Last edited by Uplinker; 9th Oct 2015 at 13:14.
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The A380 has beta vanes. Does the A320 have these or can it detect sidewinds by comparing left/right AOA angles as mentioned in this PPRuNe thread?
SIDE SLIP ANGLE [Archive] - PPRuNe Forums
SIDE SLIP ANGLE [Archive] - PPRuNe Forums
Only half a speed-brake
Contrary to some above (most actually 
) I do sometimes look at the wind readout on ND and find it useful with reasonable values. How is it calculated - no idea, I wondered myself. Best I could come up with was differentail readings between static ports L/R, but...
) I do sometimes look at the wind readout on ND and find it useful with reasonable values. How is it calculated - no idea, I wondered myself. Best I could come up with was differentail readings between static ports L/R, but...
Last edited by FlightDetent; 10th Oct 2015 at 21:59.
Best I could come up with was differential readings between static ports L/R, but...
Which in turn might explain why it is suppressed until 100 kts - when the airflow over the fuselage has stabilised?
Edit:
Checked my old paper FCOM and it just says "wind speed and direction arrow [on the ND] is provided by the ADIRS", but it doesn't say which elements of air data are used.
Last edited by Uplinker; 10th Oct 2015 at 16:30.
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Next question. Can you trust it? Really trust? If not then using it as a decision to RTO is an interesting one. In the normal takeoff brief about reasons to RTO it mentions a/c unfit to fly. Are you linking this scenario under that heading? Remember most takeoffs are at reduced power; all takeoffs assume loss of 1 engine. So, an increase in tailwind, or loss of headwind should be coped with by an increase in thrust on ALL engines. It would really be a very bad hair day to have a sudden shift in wind AND an engine failure.
I remember at Mombasa B757. Naturally a warm day and a gentle breeze from somewhere. Off we went at reduced thrust. I thought I saw the far end of the runway getting closer than expected and we were still <V1. Push up to full power and we rolled through the mirage and lifted off in half the runway. A pilot colleague in the cabin, during our long missed en-route cockpit visit/chat, asked about the sudden power bump during the roll. I explained and he understood, fully.
Like many have said, IAS readout plus looking at the far end might give more an accurate picture than a tiny wind arrow display. What does AB say about using it and its authority to make RTO decisions? Is it a nice toy put there without any particular guidance how to use it. The same is true for FPV on B737, but that's another story. If anyone wants to go down that route please one a new topic.
I remember at Mombasa B757. Naturally a warm day and a gentle breeze from somewhere. Off we went at reduced thrust. I thought I saw the far end of the runway getting closer than expected and we were still <V1. Push up to full power and we rolled through the mirage and lifted off in half the runway. A pilot colleague in the cabin, during our long missed en-route cockpit visit/chat, asked about the sudden power bump during the roll. I explained and he understood, fully.
Like many have said, IAS readout plus looking at the far end might give more an accurate picture than a tiny wind arrow display. What does AB say about using it and its authority to make RTO decisions? Is it a nice toy put there without any particular guidance how to use it. The same is true for FPV on B737, but that's another story. If anyone wants to go down that route please one a new topic.
For those suggesting that the wind ector could be used as information for an RTO, consider Airbus' advice for windshear:
The takeoff should only be rejected if significant air speed variations occur below indicated V1 and the pilot decides that there is sufficient runway remaining to stop.
I'd suggest tea and bickies if you'd aborted for an indicated wind vector change with no airspeed variation.
The takeoff should only be rejected if significant air speed variations occur below indicated V1 and the pilot decides that there is sufficient runway remaining to stop.
I'd suggest tea and bickies if you'd aborted for an indicated wind vector change with no airspeed variation.
Well perhaps, but how significant an airspeed variation would you chose to abort at and how much time would you want to spend watching the speed tape and trend to assimilate it while taking off? Have you ever briefed how much trend variation and in which direction it would have to be for you to stop or go? I am happy to have the ADIRS calculate it and give me a wind vector. Any unbriefed tail wind (or more than 10 kts tail if allowed for), would be a no brainer - either abort, or TOGA, depending on where you were on the runway.
A couple on here have spoken about the 'small size of the wind readout', but the '320/12' takes up more space than the speeds on the speed tape, and together with the arrow indication is not that small really, and you only need to glance at the arrow.
I don't think I would get tea and biscuits for being careful.
A couple on here have spoken about the 'small size of the wind readout', but the '320/12' takes up more space than the speeds on the speed tape, and together with the arrow indication is not that small really, and you only need to glance at the arrow.
I don't think I would get tea and biscuits for being careful.
Next question. Can you trust it? Really trust? If not then using it as a decision to RTO is an interesting one.
Can you give a citation for that claim ZeBedie?
If, as it seems, some of you don't trust a head/tail wind display, what makes you trust an IAS, N1 or EPR display? (also provided by engineers).
If, as it seems, some of you don't trust a head/tail wind display, what makes you trust an IAS, N1 or EPR display? (also provided by engineers).
So Uplinker,
You're on a Runway where perf figures suggest a 500m margin for takeoff.
Figures predicated on 5 kt headwind. Vr is 140.
Passing 110kts your eagle eyed PM takes his eyes off the engine display and notices a 7 kt tailwind on the wind readout. Neither of you had noticed anything untoward on the speed trend vector or tape.
What would you (or your captain expect you to) do?
I can't believe I'm answering this. You have a split second to look at the size of the arrow and the movement of the tape before back outside or to the engine parameters. You don't need to process a value or compute anything. Just long enough to get a feel as to how long until the next speed (100 or v1).
Unless your ND arrow increases in size with the wind direction you need to read the speed too. If youve seen the arrow going all over the place when the outside wind is vrb at 1-2 kts at altitude you'll understand. How do you know if that sudden tailwind is 1 kt or 10?
To look at the wind vector (which is of dubious reliability anyway) gives you no extra information, takes your eyes away from other more important items, and distracts with the cognitive awareness for other decisions.
The second of time that the PM spends trying to work out if the wind has backed or veered, and what the subsequent headwind component has done would be much better spent looking at the engine parameters.
And regarding unexpected tailwinds on departure, thats what the windsocks are for. If it's saying something you dont like on a marginal runway when you're lined up exit and recalculate with conservative estimated figures.
You're on a Runway where perf figures suggest a 500m margin for takeoff.
Figures predicated on 5 kt headwind. Vr is 140.
Passing 110kts your eagle eyed PM takes his eyes off the engine display and notices a 7 kt tailwind on the wind readout. Neither of you had noticed anything untoward on the speed trend vector or tape.
What would you (or your captain expect you to) do?
How much time would you want to spend watching the speed tape and trend to assimilate it while taking off?
You only need to glance at the arrow.
To look at the wind vector (which is of dubious reliability anyway) gives you no extra information, takes your eyes away from other more important items, and distracts with the cognitive awareness for other decisions.
The second of time that the PM spends trying to work out if the wind has backed or veered, and what the subsequent headwind component has done would be much better spent looking at the engine parameters.
And regarding unexpected tailwinds on departure, thats what the windsocks are for. If it's saying something you dont like on a marginal runway when you're lined up exit and recalculate with conservative estimated figures.
Last edited by compressor stall; 14th Oct 2015 at 22:48.
So Uplinker,
You're on a Runway where perf figures suggest a 500m margin for takeoff.
Figures predicated on 5 kt headwind. Vr is 140.
Passing 110kts your eagle eyed PM takes his eyes off the engine display and notices a 7 kt tailwind on the wind readout. Neither of you had noticed anything untoward on the speed trend vector or tape.
What would you (or your captain expect you to) do?
You're on a Runway where perf figures suggest a 500m margin for takeoff.
Figures predicated on 5 kt headwind. Vr is 140.
Passing 110kts your eagle eyed PM takes his eyes off the engine display and notices a 7 kt tailwind on the wind readout. Neither of you had noticed anything untoward on the speed trend vector or tape.
What would you (or your captain expect you to) do?
Quote:
How much time would you want to spend watching the speed tape and trend to assimilate it while taking off?
I can't believe I'm answering this. You have a split second to look at the size of the arrow and the movement of the tape before back outside or to the engine parameters. You don't need to process a value or compute anything. Just long enough to get a feel as to how long until the next speed (100 or v1).
How much time would you want to spend watching the speed tape and trend to assimilate it while taking off?
I can't believe I'm answering this. You have a split second to look at the size of the arrow and the movement of the tape before back outside or to the engine parameters. You don't need to process a value or compute anything. Just long enough to get a feel as to how long until the next speed (100 or v1).
Quote:
You only need to glance at the arrow.
Unless your ND arrow increases in size with the wind direction you need to read the speed too. If youve seen the arrow going all over the place when the outside wind is vrb at 1-2 kts at altitude you'll understand. How do you know if that sudden tailwind is 1 kt or 10?
You only need to glance at the arrow.
Unless your ND arrow increases in size with the wind direction you need to read the speed too. If youve seen the arrow going all over the place when the outside wind is vrb at 1-2 kts at altitude you'll understand. How do you know if that sudden tailwind is 1 kt or 10?
To look at the wind vector (which is of dubious reliability anyway)...
... gives you no extra information, takes your eyes away from other more important items, and distracts with the cognitive awareness for other decisions.
The second of time that the PM spends trying to work out if the wind has backed or veered, and what the subsequent headwind component has done would be much better spent looking at the engine parameters.
As for the size of the wind readout; the arrow is thicker than the V/S arrow, and bigger than the beta target indicator; surely you can see those? The numerical element of the wind readout is a similar size to ALT CRZ on the FMA - you can see that surely?
Windsocks. Hmmmm. So you are complaining about glancing at a processed readout which tells you the actual value of the wind, yet you advocate looking outside the cockpit, finding the windsock (at night - is it lit?), and assessing a head or tail wind from that. Is it more than 10 kts? And won't the windsock be behind you by the time you are into the take off roll?
And in what state are the windsocks in some second/third world airports?
I think I would rather rely on the on-board multi-thousand dollar measuring and processing equipment and computation power fitted to the plane.
(Remember, I am talking about the wind not being what it was after the tower passed it to you and you lined up, or the tower passing an incorrect wind. This actually happened to me and getting a heavy A330 airborne with an unannounced tailwind, was a moment of extreme concentration, I can tell you! - for a second or two I thought one or both elevators had failed. I now always glance at the wind readout on take-off)
Last edited by Uplinker; 20th Oct 2015 at 11:48.
