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is BIRD still reliable during unreliable speed [A320]

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is BIRD still reliable during unreliable speed [A320]

Old 26th Nov 2019, 07:43
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is BIRD still reliable during unreliable speed [A320]

Hello teachers and fellow pilots!
It's ridiculous that PPRuNe is my last resort to find answers after long painful hours of shuffling through 4000 pgs of FCOM.
This is the best source I have to figure out things that I don't understand about this aircraft since nobody in my airline wants to study this damn aircraft and fully relies on Airbus aircraft flying itself.
over 80% of em just want to **** women and drink for the remainder..
just appreciate you guys here very much

so CAE instructor kept insisting on using the BIRD since it's still reliable when I am to maintain level flight after all of the memory items of unreliable airspeed indication have been done.
I was just wondering if he is correct by telling me to use the BIRD, I had the understanding that BIRD gets its information from the ADIRS. Am I wrong here?
kikwon is offline  
Old 26th Nov 2019, 08:59
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Look in FCTM, AS-BIRD, RELIABILITY.

The bird is also computed from static pressure information. Therefore, if the altitude information is not reliable, the flight crew must consider the bird as not reliable.
Fursty Ferret is offline  
Old 26th Nov 2019, 09:47
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Although I have never flown a bus, it seems logical that if you suspect corrupt data from some part of the air data system you stick to basics and use attitude + G/S + altitude (as a second order check) to keep the shiny side up and greasy side down while you work through appropriate checklists.
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Old 26th Nov 2019, 10:17
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From the FCTM AO-034,
If the FPV is reliable, or if the GPS altitude information is available:
‐ Maintain level flight (FPV on the horizon or constant GPS altitude),
‐ Adjust thrust according to the table,
‐ Observe the resulting pitch attitude, and compare it with the recommended table pitch
target:
• If the aircraft pitch necessary to maintain level flight is above the table's pitch target,
the aircraft is slow, then increase thrust,
• If the aircraft pitch necessary to maintain level flight is below the table's pitch target, the
aircraft is fast, then decrease thrust.
When the pitch required to maintain level off gets close to the table pitch target, re-adjust
thrust according to table thrust target.
This technique enables to quickly stabilize the speed, while maintaining level flight.
 If the FPV is not reliable and the GPS altitude information is not available (no means
to ensure level flight):
Adjust pitch and thrust according to table, and wait for speed stabilization. Expect a
significant stabilization time and important altitude variations
kwaiyai is offline  
Old 26th Nov 2019, 10:18
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If available TRK/FPA can be used. If it's faulty it will not appear.
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Old 26th Nov 2019, 11:38
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Originally Posted by vilas View Post
If available TRK/FPA can be used. If it's faulty it will not appear.
I would be cautious, at least in the simulator the bird is still available if baro info is wrong, but it shows incorrect information. As quoted above the FCTM advises to consider the bird as unreliable if there is a static pressure sensing problem, it is still available though. If only total pressure sensing (aka pitot) is affected it should still work though.
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Old 26th Nov 2019, 11:56
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Originally Posted by kikwon View Post
Hello teachers and fellow pilots!
It's ridiculous that PPRuNe is my last resort to find answers after long painful hours of shuffling through 4000 pgs of FCOM.
This is the best source I have to figure out things that I don't understand about this aircraft since nobody in my airline wants to study this damn aircraft and fully relies on Airbus aircraft flying itself.
over 80% of em just want to **** women and drink for the remainder..
just appreciate you guys here very much

so CAE instructor kept insisting on using the BIRD since it's still reliable when I am to maintain level flight after all of the memory items of unreliable airspeed indication have been done.
I was just wondering if he is correct by telling me to use the BIRD, I had the understanding that BIRD gets its information from the ADIRS. Am I wrong here?
Answer here
sonicbum is offline  
Old 26th Nov 2019, 14:13
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If GPS ALT in the position monitor page or whatever its called under DATA is in the ballpark with the static pressure generated altitudes on your PFDs and ISIS then I've always been taught that your static source is good and so get the bird on.
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Old 26th Nov 2019, 18:48
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Originally Posted by wtsmg View Post
If GPS ALT ...... is in the ballpark with ... altitudes on your PFDs and ISIS
Extending the above a little:

GPS and Baro altitudes need to be pretty much exactly the same - within 100 ft let's say. Adjusted for cold temps as needed.

That familiar "looks kind of similar" feeling pilots normally have in mind comes (incorrectly) when the SIM exercise is played above transition ALT/LVL, using STD as the reference for ADIRSes.

The observed difference is not any inherent inaccuracy, but rather the delta between QNE and QNH instead.
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Old 26th Nov 2019, 22:18
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In cruise, around the area we fly at least, the GPS alt is always about 2000 ft above pressure altitude. Anyone knows the exact reason for this?
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Old 26th Nov 2019, 22:38
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https://support.garmin.com/en-US/?fa...i18S6eC2vGMpz9
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Old 27th Nov 2019, 04:25
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Originally Posted by dream747 View Post
In cruise, around the area we fly at least, the GPS alt is always about 2000 ft above pressure altitude. Anyone knows the exact reason for this?
Do you mean pressure altitude (QNE reference), or baro-derived altitude (QNH)?
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Old 27th Nov 2019, 10:13
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The UAS procedure in the A380 states: FPV Avail

Normally the FPV uses ADIRS info, with all 3 ADR’s off it’s a GPS / IR hybrid, however when there is a static problem it displays incorrect information in the SIM, and I assume it is the same on the actual aircraft.

Maybe the catch is the word “Avail” as opposed to “Reliable” for instance. Equally the FCOM mentions its display with the ADR’s is available, not accurate.


Last edited by PGA; 27th Nov 2019 at 10:19. Reason: Extra info
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Old 27th Nov 2019, 11:05
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Originally Posted by PGA View Post
The UAS procedure in the A380 states: FPV Avail

Normally the FPV uses ADIRS info, with all 3 ADR’s off it’s a GPS / IR hybrid, however when there is a static problem it displays incorrect information in the SIM, and I assume it is the same on the actual aircraft.

Maybe the catch is the word “Avail” as opposed to “Reliable” for instance. Equally the FCOM mentions its display with the ADR’s is available, not accurate.

Answer here
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Old 27th Nov 2019, 16:01
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PGA
 
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Originally Posted by sonicbum View Post
That doesn’t quite answer it though, although it’s a hybrid and accordingly doesn’t use air data, either the sim is wrong, or it needs static pressure somehow otherwise isn’t reliable.

I have tried it in the sim multiple times and the FPV is incorrect when I insert a static problem with all ADR’s off.

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