A320 Unreliable Airspeed Actions
Joined: Jan 2012
Posts: 510
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From: Not far from the edge of the Milky Way Galaxy in the Orion Arm.
Unreliable Airspeed -
Narrow (I think I can guess who you fly for by your T/O brief)
Why have you all missed the standby airspeed indicator? Why did you bug this before departure in the first place?
Why is there a V1? Therefore why, if indeed this is the case, do you want to continue boyond V1 if a fault dictates (as per yer SOPs[maybe]) that you would reject <V1 in the event of . . .?
Why not scrape the rubber and burn the paint off and stop?
If continuing (as you are the Captain) then back to my first question, the standby airspeed indicator - thats what it is there for. Will, the FMGS airspeed calcs still give accurate enroute ETAs etc., etc? I mean, will you still get there?
Also, and with prescence of mind presently flying a coffee cup on my desk, why brief `this` and then go and do `that`?
Surely, if you have said, either of us can call stop <V1 for this and that, does that part of the pre-departure brief include Unreliable Airspeed Indication? I think not.
Which gives this thread much validation and value. Ton pied.
But if it does (which is does not) then surely the answer is to stop and vacate.
My point? Unless not otherwise stipulated (in the brief) why be creative?
Or, in the words of Narrow:
Why have you all missed the standby airspeed indicator? Why did you bug this before departure in the first place?
Why is there a V1? Therefore why, if indeed this is the case, do you want to continue boyond V1 if a fault dictates (as per yer SOPs[maybe]) that you would reject <V1 in the event of . . .?
Why not scrape the rubber and burn the paint off and stop?
If continuing (as you are the Captain) then back to my first question, the standby airspeed indicator - thats what it is there for. Will, the FMGS airspeed calcs still give accurate enroute ETAs etc., etc? I mean, will you still get there?
Also, and with prescence of mind presently flying a coffee cup on my desk, why brief `this` and then go and do `that`?
Surely, if you have said, either of us can call stop <V1 for this and that, does that part of the pre-departure brief include Unreliable Airspeed Indication? I think not.
Which gives this thread much validation and value. Ton pied.
But if it does (which is does not) then surely the answer is to stop and vacate.
My point? Unless not otherwise stipulated (in the brief) why be creative?
Or, in the words of Narrow:
STOP!!!
Joined: May 2012
Posts: 30
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From: Malaysia
Unreliable Airspeed
Im new and under training. In my company, at 100kts PNF will call out "100KTS" for a speed check with the PF. Therefore, in this situation on the T/O roll with one of us having an unreliable airspeed or if both PFD speeds are not sync, below V1, we would stop. In my humble opinion, i totally agree with this policy of my company because i don't see any good reason to get off the ground with such an abnormal situation prior to V1, let alone, V1 has been calculated to provide you with sufficient distance to abort the T/O. Also, like Slasher said, it ain't so easy no more in a dark night with poor weather conditions if you decided to continue. But, thats just my opinion.
Joined: Mar 2005
Posts: 1,338
Likes: 1
From: Uh... Where was I?
very true.
The problem is if you have red flags after that.
The problem of Unreliable speed is that it is Unreliable. You don't know which speed is good. STBY ASI is as unreliable as any other speed indication.
From the moment you come to the conclusion that speed is Unreliable (which is the most difficult thing) then you trust no indication at all and manually fly pitch and thrust or pitch and flight path, depending on the circumstances.
If it happens at high speed in the middle of the take of run, well, it is a tricky situation which has not been foreseen in the procedure. What if you STOP and it happens that actual speed is very high and it is long time you passed V1? Then you will overrun the runway, that's what will happen. What if you continue? At what speed do you rotate?
there is no way to make a 100% safe decision. Probably in this case pilot instinct will make the decision. If the pilot feels that he can stop within remaining runway, he will stop. It he feels he will not, he will continue and rotate when he feels he can. And then apply the procedure
The problem is if you have red flags after that.
The problem of Unreliable speed is that it is Unreliable. You don't know which speed is good. STBY ASI is as unreliable as any other speed indication.
From the moment you come to the conclusion that speed is Unreliable (which is the most difficult thing) then you trust no indication at all and manually fly pitch and thrust or pitch and flight path, depending on the circumstances.
If it happens at high speed in the middle of the take of run, well, it is a tricky situation which has not been foreseen in the procedure. What if you STOP and it happens that actual speed is very high and it is long time you passed V1? Then you will overrun the runway, that's what will happen. What if you continue? At what speed do you rotate?
there is no way to make a 100% safe decision. Probably in this case pilot instinct will make the decision. If the pilot feels that he can stop within remaining runway, he will stop. It he feels he will not, he will continue and rotate when he feels he can. And then apply the procedure
