B777 Procedure Blocked AOA Probes
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Originally Posted by A33Zab
But the T7 will sense the same -wrong- information, like the EVA A330 did, because the 3rd comparable value is the average of both sensors.
3 identical AoA is accepted as GOOD information.
3 identical AoA is accepted as GOOD information.
Last edited by CONF iture; 1st Jan 2013 at 20:04.
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@CONF iture:
AoA protect is there for a reason, don't have to explain you that, unfortunally it was activated when not appropriate, fortunately there was and is a solution to overcome.
Question: what will be the instinctive reaction of the PF when stickshakers are suddenly activated?
Both JTSB as ASC did not initiated an investigation, although you say the control was 'kidnapped',
nobody - on this forum -seems to be concerned about that one.........shouldn't we?
@Kimon:
I admit the dual ADIRUs/SAARUs concept in B will be more robust against multiple failures compared to the 3 ADIRUs concept of A.
In single failure and in case of similar but - wrong data - it will not make any difference.
FWIW:
In A350 airbus will supply the ISIS (optionally a repeater for RH seat) with its dedicated pitot and static ports.
The triple ADIRUs concept will remain however with dedicated multifunctional probes (MFP) and slideslip sensors.
Only ADIRU#1 will be equipped with an additional normal AoA sensor.
Question: what will be the instinctive reaction of the PF when stickshakers are suddenly activated?
Both JTSB as ASC did not initiated an investigation, although you say the control was 'kidnapped',
nobody - on this forum -seems to be concerned about that one.........shouldn't we?
@Kimon:
I admit the dual ADIRUs/SAARUs concept in B will be more robust against multiple failures compared to the 3 ADIRUs concept of A.
In single failure and in case of similar but - wrong data - it will not make any difference.
FWIW:
In A350 airbus will supply the ISIS (optionally a repeater for RH seat) with its dedicated pitot and static ports.
The triple ADIRUs concept will remain however with dedicated multifunctional probes (MFP) and slideslip sensors.
Only ADIRU#1 will be equipped with an additional normal AoA sensor.
Last edited by A33Zab; 2nd Jan 2013 at 03:56.
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Originally Posted by A33Zab
Question: what will be the instinctive reaction of the PF when stickshakers are suddenly activated?
Some serious questions need to be asked why investigation bodies do not investigate a loss of control leading the EASA to publish an EMERGENCY AIRWORTHINESS DIRECTIVE and Airbus to modify its Flight Manual ...
That the event was "unfortunate" seems good enough for you to keep it quiet ... I just don't follow you on that path.
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Hopefully an initial push ... until, still hopefully, things point to the undue stickshaker activation and therefore the possibility to stabilize the situation, possibility refused to an Airbus crew before he shut a few computers down.
most probably they will (ICW OCC!) continue in Direct and silence the shackers with CB. also dual - non procedural - action required.
Some serious questions need to be asked why investigation bodies do not investigate a loss of control leading the EASA to publish an EMERGENCY AIRWORTHINESS DIRECTIVE and Airbus to modify its Flight Manual ...
That the event was "unfortunate" seems good enough for you to keep it quiet ... I just don't follow you on that path.
That the event was "unfortunate" seems good enough for you to keep it quiet ... I just don't follow you on that path.
The only 'excuse' I can imagine is that the source of this INCIDENT was that obvious (mechanical blockage) they left it to EVA QA - as first in line - to investigate.
In the EAD it is not mandated to remove the conical plates or replace the AoA sensors in factory delivered airbii.
Last edited by A33Zab; 3rd Jan 2013 at 13:37.
Yes, Kimon, the static ports have been known to freeze up.
No big deal until you climb or descend, and then altimeter doesn't change but the CAS/IAS does. With all the stuff we now have and a knowledge of power and pitch for various flight conditions you're usually in good shape.
Having the AoA sensors freeze at identical angles could be tricky, as you might lose some "protections" at higher true AoA.
Several here have experienced static system problems and are still here to contribute.
No big deal until you climb or descend, and then altimeter doesn't change but the CAS/IAS does. With all the stuff we now have and a knowledge of power and pitch for various flight conditions you're usually in good shape.
Having the AoA sensors freeze at identical angles could be tricky, as you might lose some "protections" at higher true AoA.
Several here have experienced static system problems and are still here to contribute.
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Originally Posted by A33Zab
Just like the A330 did, but they have to overcome the increased force to stabilize and keep the continuing stickshackers.
- 777 - It is possible to override the unjustified protection.
- 330 - It is NOT.
The only 'excuse' I can imagine is that the source of this INCIDENT was that obvious (mechanical blockage) they left it to EVA QA - as first in line - to investigate.
In the EAD it is not mandated to remove the conical plates or replace the AoA sensors in factory delivered airbii.
In the EAD it is not mandated to remove the conical plates or replace the AoA sensors in factory delivered airbii.
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If people think the T7 won't behave strangely or contrary to pilot command if given duff data, have a look at this article (h/t Clandestino - my bold):
What happened on flight MH124 - Nation | The Star Online
EDIT - Clarification: Clandestino mentioned the incident, not the article itself.
What happened on flight MH124 - Nation | The Star Online
According to the report by the Australian Transport Safety Bureau released on its website last Friday, the pilots were alerted to a low airspeed warning at an altitude of 11,582m.
At the same time, the primary flight display indicated that the plane was turning left, while the speed display showed that the plane was “going too fast and too slow simultaneously”.
The plane then pitched up to 12,497m and the indicated airspeed decreased from 500km/h to 292km/h.
At this point, the stall warning and stick shaker devices were activated.
...
The report revealed that Capt Norhisham then disconnected the autopilot and lowered the plane’s nose to prevent the stall.
However, the aircraft’s automatic throttle, which should have been off, came on again and compensated by increasing speed.
Capt Norhisham countered this by pushing the thrust levers to the idle position but the aircraft pitched up again and climbed another 610m.
At the same time, the primary flight display indicated that the plane was turning left, while the speed display showed that the plane was “going too fast and too slow simultaneously”.
The plane then pitched up to 12,497m and the indicated airspeed decreased from 500km/h to 292km/h.
At this point, the stall warning and stick shaker devices were activated.
...
The report revealed that Capt Norhisham then disconnected the autopilot and lowered the plane’s nose to prevent the stall.
However, the aircraft’s automatic throttle, which should have been off, came on again and compensated by increasing speed.
Capt Norhisham countered this by pushing the thrust levers to the idle position but the aircraft pitched up again and climbed another 610m.
Last edited by DozyWannabe; 4th Jan 2013 at 18:28.
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Originally Posted by DOZY
If people think the T7 won't behave strangely or contrary to pilot command if given duff data
- Strangely YES
- Contrary to pilot command NO
Show me the data of the elevator down when the pilot commands it up ... ?
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In the case of Airbus Alpha prot (as you well know), elevator down in response to a nose-up command is to maintain the aircraft at the alpha prot AoA, because to follow the pilot's command directly would result in an imminent stall.
Last edited by DozyWannabe; 4th Jan 2013 at 17:53.
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Quote:
Originally Posted by A33Zab
Just like the A330 did, but they have to overcome the increased force to stabilize and keep the continuing stickshackers.
Originally Posted by A33Zab
Just like the A330 did, but they have to overcome the increased force to stabilize and keep the continuing stickshackers.
- 777 - It is possible to override the unjustified protection.
- 330 - It is NOT.
Last edited by A33Zab; 5th Jan 2013 at 00:08.
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By T.S.
Are the following statements true on the B777 if it were an AF447?
1) Turning off the ADRs so as to force it in Secondary Mode à la A330 Alternate 1?
No. You can't turn the ADRs off in flight on a 777. The only way I know to force Secondary Mode is to open the pitot probe heat circuit breakers (which a normal flight crew should NEVER do).
2) B777 is w/o aural SW only yokeshakers so it is not subject to the 60KNS / 30 KNS cut-out set-up?
I *think* (but am not positive) that the shaker would cutout when the airspeed when too low, for the same reasons that the Airbus aural cuts out.
3) B777's equivalent of THS AutoTrim is that trims for speed only not pitch.
Not exactly. The 777 uses elevator for fast commands then trims the stabilizer to offload the elevator. 'Trim" on a 777 is really an aerodynamic state that's a combination of current elevator and stab positions, not an explicit state of either one individually.
4) Pitch authority is always driven via the elevators that command the stabs as opposed to the A330's separate - "divorced" - authority i.e. THS AutoTrim is separate entity that does not rely on elevator authority at all?
Both systems rely on both. AutoTrim and 777 stab trim are both composite systems that work together with the elevators to give the pilots what they ask for with minimum drag. The 777 has speed stability as part of the control law but, depending on the flight regime, the actual pitch command trying to return the airplane to trim speed might be elevator, stab, or both.
1) Turning off the ADRs so as to force it in Secondary Mode à la A330 Alternate 1?
No. You can't turn the ADRs off in flight on a 777. The only way I know to force Secondary Mode is to open the pitot probe heat circuit breakers (which a normal flight crew should NEVER do).
2) B777 is w/o aural SW only yokeshakers so it is not subject to the 60KNS / 30 KNS cut-out set-up?
I *think* (but am not positive) that the shaker would cutout when the airspeed when too low, for the same reasons that the Airbus aural cuts out.
3) B777's equivalent of THS AutoTrim is that trims for speed only not pitch.
Not exactly. The 777 uses elevator for fast commands then trims the stabilizer to offload the elevator. 'Trim" on a 777 is really an aerodynamic state that's a combination of current elevator and stab positions, not an explicit state of either one individually.
4) Pitch authority is always driven via the elevators that command the stabs as opposed to the A330's separate - "divorced" - authority i.e. THS AutoTrim is separate entity that does not rely on elevator authority at all?
Both systems rely on both. AutoTrim and 777 stab trim are both composite systems that work together with the elevators to give the pilots what they ask for with minimum drag. The 777 has speed stability as part of the control law but, depending on the flight regime, the actual pitch command trying to return the airplane to trim speed might be elevator, stab, or both.
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Originally Posted by A33Zab
IMO in A330 it is also 'overridable'.......manual pitch trim (to level off), I know....it's not in the procedures.
MANUAL PITCH TRIM ONLY TO FIGHT ELEV
but I love your optimism ...
