A320 FPV
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A320 FPV
Can anyone help with this conundrum please?
In the context of UAS, the FCTM tells us that if altitude info is suspect not to use the FPV. My understanding has always been (wrongly perhaps) that the FPV is purely inertial. In the sim, with all ADRs switched off, it still works.
Also, it tells us that in ac without the BUSS, we have to keep at least 1 ADR ON to allow stall warning - which is AoA related. Why do we need an ADR to allow stall warning.
As usual the FCOM DSC is next to useless.
In the context of UAS, the FCTM tells us that if altitude info is suspect not to use the FPV. My understanding has always been (wrongly perhaps) that the FPV is purely inertial. In the sim, with all ADRs switched off, it still works.
Also, it tells us that in ac without the BUSS, we have to keep at least 1 ADR ON to allow stall warning - which is AoA related. Why do we need an ADR to allow stall warning.
As usual the FCOM DSC is next to useless.
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A320 FPV
Hello my orange friend,
FPV is actually a derivative of Vzbi. Vzbi is baro-inertial vertical speed, i.e.: the one we see indicated in normal conditions.
FPA is derived using GS and Vzbi.
In conditions where Vzbi is not available FPA is derived from the difference between pitch and AoA, this is however a degraded FPA, relative to the air only!!!!
FPV is actually a derivative of Vzbi. Vzbi is baro-inertial vertical speed, i.e.: the one we see indicated in normal conditions.
FPA is derived using GS and Vzbi.
In conditions where Vzbi is not available FPA is derived from the difference between pitch and AoA, this is however a degraded FPA, relative to the air only!!!!
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This is very interesting. Out of yet more interest, does anybody know of situations where under normal operation the FPV would be spitting out nonsense? One of our aircraft gets the lateral trajectory wrong pretty consistently in light to medium crosswinds. After flying a couple of visuals I had a hunch, so the other day I flew a raw data ILS and found that every time I placed the tail of the bird on the blue line (once LOC initially centred), I'd be off the LOC pretty quickly with an undesired trend forming. Flying "close" to the blue line (3-4 degs) resulted in a better profile (Yes, runway track was correct)
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I had a case when the 2 FPV showed a different picture: one was left on the PFD and the other one symmetrically right. We both had at the same time different crosswind indications. There was no ECAM message.
After landing we had a PFR printed with ADR 1,2,3 disagree.
After landing we had a PFR printed with ADR 1,2,3 disagree.
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IRS drift
superpilot
How long was the flight. I bet you had a large IRS drift.
You know when you park and you see a residual GS or 7 kts or whatever?
In approach, a few knots of drift at right angles with the LOC will give a drift of say 1º or maybe more, so each time you center the bird, you deviate. So what you do, is when you see that the LOC is being maintained well with the bird 1º to the right, that is your target. It is like correcting the shooting with a rifle...
How long was the flight. I bet you had a large IRS drift.
You know when you park and you see a residual GS or 7 kts or whatever?
In approach, a few knots of drift at right angles with the LOC will give a drift of say 1º or maybe more, so each time you center the bird, you deviate. So what you do, is when you see that the LOC is being maintained well with the bird 1º to the right, that is your target. It is like correcting the shooting with a rifle...
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Originally Posted by mcdhu
In the sim, with all ADRs switched off, it still works.
Originally Posted by Superpilot
That does make sense
Originally Posted by mcdhu
[Can anyone help with this conundrum please?
In the context of UAS, the FCTM tells us that if altitude info is suspect not to use the FPV. My understanding has always been (wrongly perhaps) that the FPV is purely inertial
[...]
Also, it tells us that in ac without the BUSS, we have to keep at least 1 ADR ON to allow stall warning - which is AoA related. Why do we need an ADR to allow stall warning.
As usual the FCOM DSC is next to useless.
In the context of UAS, the FCTM tells us that if altitude info is suspect not to use the FPV. My understanding has always been (wrongly perhaps) that the FPV is purely inertial
[...]
Also, it tells us that in ac without the BUSS, we have to keep at least 1 ADR ON to allow stall warning - which is AoA related. Why do we need an ADR to allow stall warning.
As usual the FCOM DSC is next to useless.
That thread is just terrifying .
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Testing a simulator is more complicated than testing the simulated system (metalanguage).
Add to that, if you trust only to the simulator to test your system, your system may be - and probably will be - false too.
Testing is a difficult art, only feasable by the person who elaborates the system (beancounters may contest that !)
Add to that, if you trust only to the simulator to test your system, your system may be - and probably will be - false too.
Testing is a difficult art, only feasable by the person who elaborates the system (beancounters may contest that !)
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Hi mcdhu,
From the fcom
The ADR (Air Data Reference) part which supplies barometric altitude, airspeed, Mach, angle of attack, temperature and overspeed warnings. • The IR (Inertial Reference) part which supplies attitude, flight path vector, track, heading, accelerations, angular rates, ground speed and aircraft position.
From the fcom
The ADR (Air Data Reference) part which supplies barometric altitude, airspeed, Mach, angle of attack, temperature and overspeed warnings. • The IR (Inertial Reference) part which supplies attitude, flight path vector, track, heading, accelerations, angular rates, ground speed and aircraft position.
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A320 FPV
Hi MCDHU
I am quite sure that on our fleet AoA will continue to be used for computation of FPAair even when all ADR's are OFF.
As for the poster quoting FCOM, the FCOM is greatly simplified.
The vertical part of the FPV (fpa) is computed using both air and inertial data, same as for the normal baro-inertial vertical speed (Vzbi). Simplified: Baro for long term changes, inertial for short term and damping.
F.P.A. = arc tan(Vzbi/GS).
Hope it helps
I am quite sure that on our fleet AoA will continue to be used for computation of FPAair even when all ADR's are OFF.
As for the poster quoting FCOM, the FCOM is greatly simplified.
The vertical part of the FPV (fpa) is computed using both air and inertial data, same as for the normal baro-inertial vertical speed (Vzbi). Simplified: Baro for long term changes, inertial for short term and damping.
F.P.A. = arc tan(Vzbi/GS).
Hope it helps
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mcdhu
Pre BUSS aircraft AOA info comes through ADR so you need one for stall warning which is always correct. BUSS aircraft have modified ADIRU in which AOA info comes through IR. So in these aircrafts you switch off all three ADRs to get BUSS on the PFD.
Pre BUSS aircraft AOA info comes through ADR so you need one for stall warning which is always correct. BUSS aircraft have modified ADIRU in which AOA info comes through IR. So in these aircrafts you switch off all three ADRs to get BUSS on the PFD.
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There's some nice concise info on this earlier thread:
http://www.pprune.org/tech-log/53169...h-angle-2.html
http://www.pprune.org/tech-log/53169...h-angle-2.html
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AF447 A330 had not BUSS.
f-cp090601e1.en.pdf BEA interim report , Page 50/128, §1.16.2.4 Analysis of the messages received, shows the 4 raw ACARS messages sequence :
* 02:11:49 Loss of probe-pitot
* 02:11:55 ADIRU failure Hard
* 02:12:10 flag CAPT PFD FPV
* 02:12:16 flag F/O PFD FPV
If your FPV works ADRs off in your simulator without BUSS it is not the same in your Aircraft ; it would be a simulation failure.
f-cp090601e1.en.pdf BEA interim report , Page 50/128, §1.16.2.4 Analysis of the messages received, shows the 4 raw ACARS messages sequence :
* 02:11:49 Loss of probe-pitot
* 02:11:55 ADIRU failure Hard
* 02:12:10 flag CAPT PFD FPV
* 02:12:16 flag F/O PFD FPV
If your FPV works ADRs off in your simulator without BUSS it is not the same in your Aircraft ; it would be a simulation failure.
Last edited by roulishollandais; 23rd Jul 2014 at 15:53. Reason: times
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