AF 447 Search to resume
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PJ2 (responding to an aparently deleted post)
I apologize for being unclear.
As I understand it, there is no full time indication of engine thrust in the form of EPR, Fuel Flow, or RPM and that this data is relegated to a page of the multifunction display. Any one of these would probably be sufficient to clue a pilot to a power setting problem. If this is a correct understanding, then it could interfere with an aircrew rapidly assimilating this data in the presence of other cockpit warnings. The other two items are of course Angle of Attack and Trimmable Horizontal Stabilizer position.
Thanks for any input provided, even if you tell me I'm out in left field.
Machinbird
I apologize for being unclear.
As I understand it, there is no full time indication of engine thrust in the form of EPR, Fuel Flow, or RPM and that this data is relegated to a page of the multifunction display. Any one of these would probably be sufficient to clue a pilot to a power setting problem. If this is a correct understanding, then it could interfere with an aircrew rapidly assimilating this data in the presence of other cockpit warnings. The other two items are of course Angle of Attack and Trimmable Horizontal Stabilizer position.
Thanks for any input provided, even if you tell me I'm out in left field.
Machinbird
Last edited by Machinbird; 14th Mar 2010 at 19:57.
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RE: Machinbird #498
Thanks for elaborating on the lost high-AoA protections in Alternate and Direct flight control laws. I had not fully appreciated it was that bad. As to your question:
I'm sorry I cannot be of much help. I have never been in an A330 cockpit, and all I know about it is from contributions on this and the previous thread. From these I understand that AoA is not available, engine parameters are available by selecting a particular page on the ECAM, and about THS I know nothing. I would expect that display of engine parameters is automatic in some abnormal conditions, but don't know if A/THR OFF is one of these.
regards,
HN39
Thanks for elaborating on the lost high-AoA protections in Alternate and Direct flight control laws. I had not fully appreciated it was that bad. As to your question:
Would you care to comment on the availability of the following 3 parameters in the A330 cockpit.
regards,
HN39
Machinbird;
The following are images of the two ECAM pages which are always default-visible during the Cruise phase of the flight.
System pages may be viewed at any time on the bottom ECAM display by selecting that system from a panel on the pedestal, just below the ECAM displays. Should an abnormality occur, the affected system page is displayed automatically.
A very brief description:
The E/WD appears on the upper ECAM display unit (DU).
– The upper part of this DU displays :
• Engine parameters (refer to 2.71.90)
• Fuel on board (FOB) (refer to 2.28.20)
• Position of slats and flaps (refer to 2.27.40)
– The lower part of this DU displays messages generated by the FWC :
• Warning and caution messages when a failure occurs
• Memos when there is no failure
The lower part, which is dedicated to ECAM messages, is divided into two parts of several lines each.
Left part :
– Primary or independent warnings and cautions, or
– Memo information
Right part :
– Title of system affected by a primary or independent warning or caution in case of overflow on the left part, or
– Secondary failure, or
– Memo, or
– Special lines (such as “AP OFF”, “LAND ASAP”)
As soon as the FWC detects a failure, and if there is no flight phase inhibition active, the E/WD displays the title of the failure and actions to be taken.
The action line clears automatically when the flight crew has executed the required action.
A picture is worth a thousand posts. Top ECAM E/WD, Engine and Warning Display:
The Lower ECAM, SD - Status Display.
The THS setting is not displayed but the GWCG (Gross Weight CofG) is. The THS setting is available on the F/CTL - Flight Control ECAM page; note that the bottom section of the display remains the same:
Below is a clearly-visible mechanical indication of the actual THS position right beside the mechanical THS trim wheels on the pedestal. the small pointer below the scale is the position of the THS. Along with the indication on the ECAM and in the MCDU, (Multi-Purpose Control and Display Unit -the interface keyboard with the FMGEC), it is checked for correctness on takeoff after the T/O data is received and the THS manually set (using the trim wheel).
Trim is otherwise automatic in flight.
The photo is taken from the F/O's seat.
Below is a very good image of an A330 cockpit at night. Notice the center ECAM screens in the standard cruise configuration; the THS actual position is visible in the green band beside the THS wheels on the thrust lever quadrant.
If I may offer a thought on this, what you're describing is a masking effect of an autoflight system; in such a scenario, the aircraft is assumed to be seriously out of trim but the autoflight system is masking the circumstances causing the mis-trimming by deflecting the flight controls or trimming to extreme positions. Across-wing fuel imbalances are thought to be one example.
The trim tank on the A330 holds about 4200kg of fuel, taking the CofG further aft to off-load the horizontal stabilizer from the traditional work it must do to during flight. The CofG is usually run between 29 and 37% MAC with a max after CofG, if I recall from a previous post, of around 39%.
That the THS began to trim NU to the point of "deep stall" (once the autopilot disconnected?) as a result of erroneous data signaling lower airspeed (requiring more NU trim) was not observed/noted in the other thirteen pitot/airspeed events which are listed at the end of the BEA Interim Report 2. I don't believe that the THS would be trimmed NU, while on autopilot, to the point where a deep stall condition would be latent with a resulting LOC once the autopilot disengaged. Just a thought....I may be misunderstanding your thought however!
We don't know anything about the THS setting for AF447 and so anything is conceivable. Whether it is probable, meaning that the possibility is within the design scope of the airplane, is, up to a point, a discussable matter. In the end, I believe that software engineers of extremely sophisticated systems such as exist in aircraft, will tell us that all possible modes of response can be known or tested nor can software be validated for all existing possibilities (whether they have occurred or not). I believe the QF A330 experience was like this; the BEA Report 2 does observe however that the QF event bears no similarity to AF447.
Hope this helps, Machinbird. It is far more difficult to explain the airplane in a typed discussion than by either flying it or even talking about it.
PJ2
The following are images of the two ECAM pages which are always default-visible during the Cruise phase of the flight.
System pages may be viewed at any time on the bottom ECAM display by selecting that system from a panel on the pedestal, just below the ECAM displays. Should an abnormality occur, the affected system page is displayed automatically.
A very brief description:
The E/WD appears on the upper ECAM display unit (DU).
– The upper part of this DU displays :
• Engine parameters (refer to 2.71.90)
• Fuel on board (FOB) (refer to 2.28.20)
• Position of slats and flaps (refer to 2.27.40)
– The lower part of this DU displays messages generated by the FWC :
• Warning and caution messages when a failure occurs
• Memos when there is no failure
The lower part, which is dedicated to ECAM messages, is divided into two parts of several lines each.
Left part :
– Primary or independent warnings and cautions, or
– Memo information
Right part :
– Title of system affected by a primary or independent warning or caution in case of overflow on the left part, or
– Secondary failure, or
– Memo, or
– Special lines (such as “AP OFF”, “LAND ASAP”)
As soon as the FWC detects a failure, and if there is no flight phase inhibition active, the E/WD displays the title of the failure and actions to be taken.
The action line clears automatically when the flight crew has executed the required action.
A picture is worth a thousand posts. Top ECAM E/WD, Engine and Warning Display:
The Lower ECAM, SD - Status Display.
The THS setting is not displayed but the GWCG (Gross Weight CofG) is. The THS setting is available on the F/CTL - Flight Control ECAM page; note that the bottom section of the display remains the same:
Below is a clearly-visible mechanical indication of the actual THS position right beside the mechanical THS trim wheels on the pedestal. the small pointer below the scale is the position of the THS. Along with the indication on the ECAM and in the MCDU, (Multi-Purpose Control and Display Unit -the interface keyboard with the FMGEC), it is checked for correctness on takeoff after the T/O data is received and the THS manually set (using the trim wheel).
Trim is otherwise automatic in flight.
The photo is taken from the F/O's seat.
Below is a very good image of an A330 cockpit at night. Notice the center ECAM screens in the standard cruise configuration; the THS actual position is visible in the green band beside the THS wheels on the thrust lever quadrant.
Originally Posted by Machinbird
I also suspect that the A-330 can be held in a deep stall by full nose up trim and an aft CG and yet be stabilized in a relatively stable normal flight attitude by the flight control system.
The trim tank on the A330 holds about 4200kg of fuel, taking the CofG further aft to off-load the horizontal stabilizer from the traditional work it must do to during flight. The CofG is usually run between 29 and 37% MAC with a max after CofG, if I recall from a previous post, of around 39%.
That the THS began to trim NU to the point of "deep stall" (once the autopilot disconnected?) as a result of erroneous data signaling lower airspeed (requiring more NU trim) was not observed/noted in the other thirteen pitot/airspeed events which are listed at the end of the BEA Interim Report 2. I don't believe that the THS would be trimmed NU, while on autopilot, to the point where a deep stall condition would be latent with a resulting LOC once the autopilot disengaged. Just a thought....I may be misunderstanding your thought however!
We don't know anything about the THS setting for AF447 and so anything is conceivable. Whether it is probable, meaning that the possibility is within the design scope of the airplane, is, up to a point, a discussable matter. In the end, I believe that software engineers of extremely sophisticated systems such as exist in aircraft, will tell us that all possible modes of response can be known or tested nor can software be validated for all existing possibilities (whether they have occurred or not). I believe the QF A330 experience was like this; the BEA Report 2 does observe however that the QF event bears no similarity to AF447.
Hope this helps, Machinbird. It is far more difficult to explain the airplane in a typed discussion than by either flying it or even talking about it.
PJ2
Last edited by PJ2; 14th Mar 2010 at 23:09.
Superstall?
Having had the opportunity to look at the B747 and MD11 stall, and additionally B737 stall behavior, I would be surprised if the spanwise flow of the A330 wing caused any aberrant pitch effects in the stall, and would expect that the aircraft would respond in time to a nose down elevator input if introduced, if the elevator authority has not been reduced by the stabiliser setting. In cruise flight, notwithstanding the use of fuel trimming tanks, the stabiliser setting is NOT a high nose up position. For the B744 (44%MAC, way outside limits...)and B777 (42%MAC) with aft CG, this still is not the case. The washout and engine pylons act to reduce the spanwise flow effect which is otherwise the principle cause of premature tip stalling.
The A310 AFL593 accident was a stall/spin event;
The CAL140 A300-600R event at NGO was due to engine thrust pitch up moment coupling with the nose up trim of the autopilot in opposition to the pilots nose down elevator response.
"* The F/O inadvertently triggered the Go lever. It is considered that the design of the GO lever contributed to it: normal operation of the thrust lever allows the possibility of an inadvertent triggering of the GO lever.
* The crew engaged the APs while GO AROUND mode was still engaged, and continued approach.
* The F/O continued pushing the control wheel in accordance with the CAP's instructions, despite its strong resistive force, in order to continue the approach.
* The movement of the THS conflicted with that of the elevators, causing an abnormal out-of-trim situation.
* There was no warning and recognition function to alert the crew directly and actively to the onset of the abnormal out-of-trim condition.
* The CAP and F/O did not sufficiently understand the FD mode change and the AP override function.
It is considered that unclear descriptions of the AFS (Automatic Flight System) in the FCOM (Flight Crew Operating Manual) prepared by the aircraft manufacturer contributed to this.
* The CAP's judgment of the flight situation while continuing approach was inadequate, control take-over was delayed, and appropriate actions were not taken.
* The Alpha-Floor function was activated; this was incompatible with the abnormal out-of-trim situation, and generated a large pitch-up moment. This narrowed the range of selection for recovery operations and reduced the time allowance for such operations.
* The CAP's and F/O's awareness of the flight conditions, after the PlC took over the controls and during their recovery operation, was inadequate respectively.
* Crew coordination between the CAP and the F/O was inadequate.
* The modification prescribed in Service Bulletin SB A300-22-602 1 had not been incorporated into the aircraft.
* The aircraft manufacturer did not categorise the SB A300-22-6021 as "Mandatory", which would have given it the highest priority. The airworthiness authority of the nation of design and manufacture did not issue promptly an airworthiness directive pertaining to implementation of the above SB."
There was no stall related pitch up...
The CAL676 A300-600R event at TPE was due to an out of trim stabiliser and thrust pitch up moment not being countered by the pilot.
"The investigation team determined that the the following factors combination caused the accident:
1. during all the descent and the approach, the aircraft was higher than the normal path;
2. the crew coordination between the captain and the first officer was inadequate.
3. during 12 seconds, the crew did not counteract the pitch up tendency due to the thrust increase after go around, and then the reaction of the crew was not sufficient.
As a consequence the pitch up increased until the aircraft stalled."
there was no stall related pitch up....
AFL593 pitch was responsive to elevator throughout the upset, even when the aircraft remained in stall and post stall autorotation.
There have been numerous pitch up events with the A310 and A300-600, as well as some with the A320, such as Interflug @ UUEE, YouTube - Blackbox - 05 - Blaming the Pilot - Part 5 of 5 TAROM at CDG, http://www.bea.aero/docspa/1994/yr-a...r-a940924a.pdfUSAir @ Washington Reagan. They have invariably been the result of out of trim condition of the stabiliser ("THS" - Airbus...) and rapid pitch up trim related to the application of full TOGA thrust. Numerous of these resulted in aerodynamic stall, none resulted in stall related pitch up.
The A330 has (and it pains me to say so
) a beautifully designed wing. Doesn't look like it but it truly is a great bit of aerodynamics. It is a far better wing than the A300/310/320. The leading edge radius is much larger than any Boeing design, and promotes a gentle aerodynamic stall break.
I have only ever looked at one stall event of an A330, which resulted from an overspeed causing a FCS related uncommanded pitch up which also exceeded max operating altitude of the aircraft, and resulted in a short duration of the aircraft being below VS1g, with varying gz causing short period stall. The recovery was normal, and I cannot recall any evidence of a further uncommanded pitch moment developing. Don't try this at home, but the A330 is a docile handling aircraft. (I remain unconvinced about the justification of having a full rating TOGA setting for day to day go arounds)
This is not Airbus bashing; I have seen B744 events where the crew have ended up in a fairly spectacular unusual attitude through the application of TOGA x2 pushes, and getting full TOGA thrust on a light weight go around. As good as an airshow, and the pax don't have to pay extra!
At altitude, the AFR447 engines would not generate that much thrust, a little over 50% of sea level rated thrust, so the potential for pitch up resulting from thrust couple is reduced, but still exists to an extent.
The touchdown attitude some minutes after the precipitating event does not necessarily bear any direct relation to the initial upset.
regards,
FDR
The A310 AFL593 accident was a stall/spin event;
The CAL140 A300-600R event at NGO was due to engine thrust pitch up moment coupling with the nose up trim of the autopilot in opposition to the pilots nose down elevator response.
"* The F/O inadvertently triggered the Go lever. It is considered that the design of the GO lever contributed to it: normal operation of the thrust lever allows the possibility of an inadvertent triggering of the GO lever.
* The crew engaged the APs while GO AROUND mode was still engaged, and continued approach.
* The F/O continued pushing the control wheel in accordance with the CAP's instructions, despite its strong resistive force, in order to continue the approach.
* The movement of the THS conflicted with that of the elevators, causing an abnormal out-of-trim situation.
* There was no warning and recognition function to alert the crew directly and actively to the onset of the abnormal out-of-trim condition.
* The CAP and F/O did not sufficiently understand the FD mode change and the AP override function.
It is considered that unclear descriptions of the AFS (Automatic Flight System) in the FCOM (Flight Crew Operating Manual) prepared by the aircraft manufacturer contributed to this.
* The CAP's judgment of the flight situation while continuing approach was inadequate, control take-over was delayed, and appropriate actions were not taken.
* The Alpha-Floor function was activated; this was incompatible with the abnormal out-of-trim situation, and generated a large pitch-up moment. This narrowed the range of selection for recovery operations and reduced the time allowance for such operations.
* The CAP's and F/O's awareness of the flight conditions, after the PlC took over the controls and during their recovery operation, was inadequate respectively.
* Crew coordination between the CAP and the F/O was inadequate.
* The modification prescribed in Service Bulletin SB A300-22-602 1 had not been incorporated into the aircraft.
* The aircraft manufacturer did not categorise the SB A300-22-6021 as "Mandatory", which would have given it the highest priority. The airworthiness authority of the nation of design and manufacture did not issue promptly an airworthiness directive pertaining to implementation of the above SB."
There was no stall related pitch up...
The CAL676 A300-600R event at TPE was due to an out of trim stabiliser and thrust pitch up moment not being countered by the pilot.
"The investigation team determined that the the following factors combination caused the accident:
1. during all the descent and the approach, the aircraft was higher than the normal path;
2. the crew coordination between the captain and the first officer was inadequate.
3. during 12 seconds, the crew did not counteract the pitch up tendency due to the thrust increase after go around, and then the reaction of the crew was not sufficient.
As a consequence the pitch up increased until the aircraft stalled."
there was no stall related pitch up....
AFL593 pitch was responsive to elevator throughout the upset, even when the aircraft remained in stall and post stall autorotation.
There have been numerous pitch up events with the A310 and A300-600, as well as some with the A320, such as Interflug @ UUEE, YouTube - Blackbox - 05 - Blaming the Pilot - Part 5 of 5 TAROM at CDG, http://www.bea.aero/docspa/1994/yr-a...r-a940924a.pdfUSAir @ Washington Reagan. They have invariably been the result of out of trim condition of the stabiliser ("THS" - Airbus...) and rapid pitch up trim related to the application of full TOGA thrust. Numerous of these resulted in aerodynamic stall, none resulted in stall related pitch up.
The A330 has (and it pains me to say so
) a beautifully designed wing. Doesn't look like it but it truly is a great bit of aerodynamics. It is a far better wing than the A300/310/320. The leading edge radius is much larger than any Boeing design, and promotes a gentle aerodynamic stall break. I have only ever looked at one stall event of an A330, which resulted from an overspeed causing a FCS related uncommanded pitch up which also exceeded max operating altitude of the aircraft, and resulted in a short duration of the aircraft being below VS1g, with varying gz causing short period stall. The recovery was normal, and I cannot recall any evidence of a further uncommanded pitch moment developing. Don't try this at home, but the A330 is a docile handling aircraft. (I remain unconvinced about the justification of having a full rating TOGA setting for day to day go arounds)
This is not Airbus bashing; I have seen B744 events where the crew have ended up in a fairly spectacular unusual attitude through the application of TOGA x2 pushes, and getting full TOGA thrust on a light weight go around. As good as an airshow, and the pax don't have to pay extra!
At altitude, the AFR447 engines would not generate that much thrust, a little over 50% of sea level rated thrust, so the potential for pitch up resulting from thrust couple is reduced, but still exists to an extent.
The touchdown attitude some minutes after the precipitating event does not necessarily bear any direct relation to the initial upset.
regards,
FDR
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PJ2
Thank you for a very detailed answer. I understand the difficulty in explaining these systems in a clear and succinct manner. The paper manuals for the aircraft are hundreds of pages long. I'm going to take a little time to be sure I understand the available aircrew information. At this point, it appears that Airbus did an admirable job in their cockpit design save for the typical airliner aversion for displaying AOA. Can I assume that the manual trim wheel turns as the automatic system trims the aircraft?
Actually, the thought runs a bit differently.
If the initial airspeed errors generated were to the high side of the true value and did not yet exceed rejection criterea, the autothrottle system would throttle back to bring the aircraft back on calculated target speed. As the aircraft slowed, the auto flight system would trim nose up to keep the elevator centered and the aircraft on altitude. Suppose the aircraft lost perhaps 30 knots actual IAS before the airspeed rejection criterea activated and thrust lock activated, throwing the aircraft into alternate law. As long as the aircraft was in alternate law the THS would continue to autotrim and the flight control system would maintain aircraft attitude absent an input from the aircrew, however the aircraft would be seriously under-throttled and decelerating. When the aircraft then transitioned to Direct Law, auto trim would stop, but by then THS position could be very nose up. Of course, Airbus may very well have written protecting limits into their software that would stop this sequence before it progressed this far.
(Note: writing this at work so I don't have references at hand)
Thank you again PJ2 for your response. After all the posts on this and related threads, it is probably hard not to say, "Oh No! Here is another one of those."
Machinbird
Thank you for a very detailed answer. I understand the difficulty in explaining these systems in a clear and succinct manner. The paper manuals for the aircraft are hundreds of pages long. I'm going to take a little time to be sure I understand the available aircrew information. At this point, it appears that Airbus did an admirable job in their cockpit design save for the typical airliner aversion for displaying AOA. Can I assume that the manual trim wheel turns as the automatic system trims the aircraft?
That the THS began to trim NU to the point of "deep stall" (once the autopilot disconnected?) as a result of erroneous data signaling lower airspeed (requiring more NU trim) was not observed/noted in the other thirteen pitot/airspeed events which are listed at the end of the BEA Interim Report 2. I don't believe that the THS would be trimmed NU, while on autopilot, to the point where a deep stall condition would be latent with a resulting LOC once the autopilot disengaged. Just a thought....I may be misunderstanding your thought however! PJ2
If the initial airspeed errors generated were to the high side of the true value and did not yet exceed rejection criterea, the autothrottle system would throttle back to bring the aircraft back on calculated target speed. As the aircraft slowed, the auto flight system would trim nose up to keep the elevator centered and the aircraft on altitude. Suppose the aircraft lost perhaps 30 knots actual IAS before the airspeed rejection criterea activated and thrust lock activated, throwing the aircraft into alternate law. As long as the aircraft was in alternate law the THS would continue to autotrim and the flight control system would maintain aircraft attitude absent an input from the aircrew, however the aircraft would be seriously under-throttled and decelerating. When the aircraft then transitioned to Direct Law, auto trim would stop, but by then THS position could be very nose up. Of course, Airbus may very well have written protecting limits into their software that would stop this sequence before it progressed this far.
(Note: writing this at work so I don't have references at hand)
Thank you again PJ2 for your response. After all the posts on this and related threads, it is probably hard not to say, "Oh No! Here is another one of those."
Machinbird
Machinbird;
Airbus did a brilliant job. The ECAM warnings and drills are extremely well thought out and works providing the crew are very strictly disciplined and follow the ECAM drills to the letter, and right to the very end of the drill. Great confusion/wrong airplane system responses can occur if the crew doesn't do this.
The THS trim wheel moves and is very visible in it's motion in the cockpit, day or night. The only thing it's missing is the noise from the B727's trim wheel. It just goes silently about its business. Trimming using manual trim in an emergency (loss of all electrics - the motors still require hydraulics), is not difficult, (in the sim).
Some research done into speeds may be helpful here plus some understanding of Airbus Reversion Laws when speeds change from computed/commanded for whatever reason. Let's look at the speeds then your assumptions.
Assuming AF447 weights or a bit heavier:
A330-200, 211T, 25%CofG, FL350 (FuelOB 64.9T), Cruise M0.81
TAS..........................................469kts
CAS..........................................274kts
VMO.........................................292kts
Green Dot, (best L/D)...............249kts
Vls, (lowest selectable speed)...214kts
AlphaProt.................................203kts
AlphaMax.................................196kts
In Normal Law, AlphaMax is the maximum angle of attack that can be flown. The airplane can be flown with full backstick and will not stall (go below AlphaMax).
In Alternate Law the airplane will go below this speed without automatic response from the engines but the crew can apply TOGA thrust and execute the standard response to the stall. The stall characteristics are benign although at altitude it can take a lot of sky to ensure recovery and avoid a secondary (to quick to increase AoA) stall.
To your example then, assuming normal cruise speed of 274kts CAS, the airplane is almost 80kts away from AlphaMax speed and 60kts away from the lowest selectable speed. In fact in your 30kts-lost example we can see that the best L/D speed is just under 30kts away from the cruise CAS.
So, to the point, it isn't a matter of 30kts away from difficulty even this early in the flight, (some have suggested the airplane was very close to "coffin corner" - not the case, as shown here). The airplane is no different than any other - the trim does respond to reductions in airspeed as does the autothrust - one sees this especially in mountain waves and while the point is understood, the numbers don't bear out the theory and Airbus has indeed built protections in as described.
One important point which seems to be at odds with your scenario is, the airplane does not revert to Alternate then Direct law merely as a function of reduced speed. Reverting to Alternate Law or Direct law means a loss of data references has occurred and the airplane has no target speeds to maintain. The airplane is a DC8, etc and one must be a pilot, not a manager.
Airbus speed reversions are much less interventionist than Alternate/Direct law. In cruise flight, the a/t maintains speed very tightly. One rarely seems the trim wheel move a great deal.
However, (and only if flying manually) and in a climb or descent and one does not follow the flight directors and either pitches NU beyond commands or levels off before capturing the set altitude without intervening in any other way, the speed will indeed bleed off (because there are no FCU/Autoflight conditions to be satisfied) until about 4kts or so above Vls at which time the a/t reverts to "SPEED" or "MACH" and the engine power increases to regain the last set speed. It can be exciting...but in normal law the airplane will not go below Vls unless in Alternate or Direct Law.
In Alternate 1 or 2 laws or Direct law, it is a "normal" airplane like a DC8 etc and one must fly it incuding the engine thrust.
In short, even in very low speed circumstances as described and with the standard CofG with trim tank full, I think the THS would be a long way from a setting which would take the airplane into a deep/super stall as per Davies' description, all on its own, beyond the control of the crew.
fdr's comments are well worth reviewing, especially regarding the power available....the engines are running at 93% in cruise most of the time. Max CL N1 is around 104% if I recall...there just isn't much more available to either pitch up with or overspeed with (on engine power alone).
PJ2
Airbus did a brilliant job. The ECAM warnings and drills are extremely well thought out and works providing the crew are very strictly disciplined and follow the ECAM drills to the letter, and right to the very end of the drill. Great confusion/wrong airplane system responses can occur if the crew doesn't do this.
The THS trim wheel moves and is very visible in it's motion in the cockpit, day or night. The only thing it's missing is the noise from the B727's trim wheel. It just goes silently about its business. Trimming using manual trim in an emergency (loss of all electrics - the motors still require hydraulics), is not difficult, (in the sim).
If the initial airspeed errors generated were to the high side of the true value and did not yet exceed rejection criterea, the autothrottle system would throttle back to bring the aircraft back on calculated target speed. As the aircraft slowed, the auto flight system would trim nose up to keep the elevator centered and the aircraft on altitude. Suppose the aircraft lost perhaps 30 knots actual IAS before the airspeed rejection criterea activated and thrust lock activated, throwing the aircraft into alternate law. As long as the aircraft was in alternate law the THS would continue to autotrim and the flight control system would maintain aircraft attitude absent an input from the aircrew, however the aircraft would be seriously under-throttled and decelerating. When the aircraft then transitioned to Direct Law, auto trim would stop, but by then THS position could be very nose up. Of course, Airbus may very well have written protecting limits into their software that would stop this sequence before it progressed this far.
Assuming AF447 weights or a bit heavier:
A330-200, 211T, 25%CofG, FL350 (FuelOB 64.9T), Cruise M0.81
TAS..........................................469kts
CAS..........................................274kts
VMO.........................................292kts
Green Dot, (best L/D)...............249kts
Vls, (lowest selectable speed)...214kts
AlphaProt.................................203kts
AlphaMax.................................196kts
In Normal Law, AlphaMax is the maximum angle of attack that can be flown. The airplane can be flown with full backstick and will not stall (go below AlphaMax).
In Alternate Law the airplane will go below this speed without automatic response from the engines but the crew can apply TOGA thrust and execute the standard response to the stall. The stall characteristics are benign although at altitude it can take a lot of sky to ensure recovery and avoid a secondary (to quick to increase AoA) stall.
To your example then, assuming normal cruise speed of 274kts CAS, the airplane is almost 80kts away from AlphaMax speed and 60kts away from the lowest selectable speed. In fact in your 30kts-lost example we can see that the best L/D speed is just under 30kts away from the cruise CAS.
So, to the point, it isn't a matter of 30kts away from difficulty even this early in the flight, (some have suggested the airplane was very close to "coffin corner" - not the case, as shown here). The airplane is no different than any other - the trim does respond to reductions in airspeed as does the autothrust - one sees this especially in mountain waves and while the point is understood, the numbers don't bear out the theory and Airbus has indeed built protections in as described.
One important point which seems to be at odds with your scenario is, the airplane does not revert to Alternate then Direct law merely as a function of reduced speed. Reverting to Alternate Law or Direct law means a loss of data references has occurred and the airplane has no target speeds to maintain. The airplane is a DC8, etc and one must be a pilot, not a manager.
Airbus speed reversions are much less interventionist than Alternate/Direct law. In cruise flight, the a/t maintains speed very tightly. One rarely seems the trim wheel move a great deal.
However, (and only if flying manually) and in a climb or descent and one does not follow the flight directors and either pitches NU beyond commands or levels off before capturing the set altitude without intervening in any other way, the speed will indeed bleed off (because there are no FCU/Autoflight conditions to be satisfied) until about 4kts or so above Vls at which time the a/t reverts to "SPEED" or "MACH" and the engine power increases to regain the last set speed. It can be exciting...but in normal law the airplane will not go below Vls unless in Alternate or Direct Law.
In Alternate 1 or 2 laws or Direct law, it is a "normal" airplane like a DC8 etc and one must fly it incuding the engine thrust.
In short, even in very low speed circumstances as described and with the standard CofG with trim tank full, I think the THS would be a long way from a setting which would take the airplane into a deep/super stall as per Davies' description, all on its own, beyond the control of the crew.
fdr's comments are well worth reviewing, especially regarding the power available....the engines are running at 93% in cruise most of the time. Max CL N1 is around 104% if I recall...there just isn't much more available to either pitch up with or overspeed with (on engine power alone).
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PJ2
Thank you again for a thoughtful and careful response. The scenario described was intended to be AF447 specific, ie. impending loss of all ADRs. Once you have a double ADR fault, autopilot and autothrottles drop out. With ADR disagreement, you have ALT 2 flight control laws which also means loss of Alpha Prot. in this case. When 3 PRIMs drop out, which appears to have happend in AF447, you have Direct Law. The 30 knot suggested hidden airspeed dropoff would have been just the beginning. The cavalry charge alarm would announce the remainder.
What ECAM procedure would have priority on the display in this situation? Logically UAS should be, but are their exceptions in the logic?
Thanks and best wishes,
Machinbird
Thank you again for a thoughtful and careful response. The scenario described was intended to be AF447 specific, ie. impending loss of all ADRs. Once you have a double ADR fault, autopilot and autothrottles drop out. With ADR disagreement, you have ALT 2 flight control laws which also means loss of Alpha Prot. in this case. When 3 PRIMs drop out, which appears to have happend in AF447, you have Direct Law. The 30 knot suggested hidden airspeed dropoff would have been just the beginning. The cavalry charge alarm would announce the remainder.
What ECAM procedure would have priority on the display in this situation? Logically UAS should be, but are their exceptions in the logic?
Thanks and best wishes,
Machinbird
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RE: Machinbird #498
There is also Stall Warning and Stall Ident. To get a feel for the deck angle variation I have estimated the AoA for the speeds given in PJ2’s #507 in the table below (deck angle equals AoA in level flight):
A330-200, 211T, 25%CofG, FL350 (FuelOB 64.9T), Cruise M0.81
............................................................ ............. AoA (deg)
TAS..........................................469kts
CAS..........................................274kts ............. 2.9
VMO.........................................292kts ............. 2.0
Green Dot, (best L/D)...............249kts ............. 4.4
Vls, (lowest selectable speed)...214kts ............. 7.3
AlphaProt.................................203kts .............. 8.5
AlphaMax.................................196kts .............. 9.3
regards,
HN39
The only clue would be an increasing deck angle and reduced power settings..
A330-200, 211T, 25%CofG, FL350 (FuelOB 64.9T), Cruise M0.81
............................................................ ............. AoA (deg)
TAS..........................................469kts
CAS..........................................274kts ............. 2.9
VMO.........................................292kts ............. 2.0
Green Dot, (best L/D)...............249kts ............. 4.4
Vls, (lowest selectable speed)...214kts ............. 7.3
AlphaProt.................................203kts .............. 8.5
AlphaMax.................................196kts .............. 9.3
regards,
HN39
Last edited by HazelNuts39; 1st Apr 2010 at 21:58. Reason: AoA corrected for Mach with P.-G.
HazelNuts39;
I wonder if you meant pitch attitude? The AoA at stall is, just guessing, going to be around 14 to 18deg perhaps a bit higher given the wing.
Again, for everyone's information, none of these images "points to cause" - I am providing them only for demonstration and understanding and not for speculation or investigating:
For 212k kg, FL350 the pitch attitude at AlphaProt is almost 9deg; the CBT autoflight software doesn't simulate Alternate law and remains in Normal Law so it correctly pitches down at AlphaProt engaging the autothrust Alpha mode and won't give the pitch attitude at AlphaMax. Snapshot below:
Machinbird;
If I am understanding correcly are you suggesting that crews would not notice (because AoA is not annunciated or THS setting etc?) a 30kt drop in airspeed and "the cavalry charge alarm would announce the remainder"? That's what I'm reading in between the lines. If this is not the thinking perhaps I have misread.
Notwithstanding the one glaring example of a crew not paying attention to airspeed while flying the airplane on approach, a 30kt loss of airspeed in cruise is HUGE; ten knots and the crew is all over it monitoring autothrust response. It's not that uncommon and mountain wave activity is a primary example; speed variations of that order (10 to 15kts sometimes more but less so) are not uncommon in heavy turbulence, but again the crew would be all over it. I've disconnected the autothrust many times and left it at one thrust setting and let the speed wander up and down, within reason of course. In rare, serious displacements such as in substantial up/down drafts in convective or mountain wave activity, one lets the altitude wander just to ensure that a reasonable pitch attitude is maintained; otherwise large excursions and the scenarios outlined by fdr above can develop. And all this would be open to professional discussion and perhaps disagreement as others may have slightly different approaches but the essentials are what I'm trying to convey here.
In the scenario you're positing, the cavalry charge would signal disconnection of the autopilot long before speed was lost simply because of the loss of the PRIMs. The single chime would announce the disengagement of the autothrust and would also be continuously sounding, announcing new ECAM messages which would be appearing on the lower ECAM and which would be continuously re-prioritizing. As to which ECAM procedure would be prioritized, I have no idea but there would be a lot of them but that's what we train for.
To this end, as I have described before, great discipline would be required under such circumstances waiting until the airplane and warnings settled down so one could do the drills. The absolute first priority is flying the airplane by pitch attitude (which they had) and power both of which should instantly be in the hands of the PF; that is what the Unreliable Airspeed drill is all about. BTW, the unreliable airspeed abnormal does not come up on the ECAM - the first few items are memorized, (which should be obvious) and the entire drill is in the QRH. Examples of the AF drill are shown in the Appendices of the BEA 2nd Interim Report.
PJ2
I wonder if you meant pitch attitude? The AoA at stall is, just guessing, going to be around 14 to 18deg perhaps a bit higher given the wing.
Again, for everyone's information, none of these images "points to cause" - I am providing them only for demonstration and understanding and not for speculation or investigating:
For 212k kg, FL350 the pitch attitude at AlphaProt is almost 9deg; the CBT autoflight software doesn't simulate Alternate law and remains in Normal Law so it correctly pitches down at AlphaProt engaging the autothrust Alpha mode and won't give the pitch attitude at AlphaMax. Snapshot below:
Machinbird;
The 30 knot suggested hidden airspeed dropoff would have been just the beginning. The cavalry charge alarm would announce the remainder.
Notwithstanding the one glaring example of a crew not paying attention to airspeed while flying the airplane on approach, a 30kt loss of airspeed in cruise is HUGE; ten knots and the crew is all over it monitoring autothrust response. It's not that uncommon and mountain wave activity is a primary example; speed variations of that order (10 to 15kts sometimes more but less so) are not uncommon in heavy turbulence, but again the crew would be all over it. I've disconnected the autothrust many times and left it at one thrust setting and let the speed wander up and down, within reason of course. In rare, serious displacements such as in substantial up/down drafts in convective or mountain wave activity, one lets the altitude wander just to ensure that a reasonable pitch attitude is maintained; otherwise large excursions and the scenarios outlined by fdr above can develop. And all this would be open to professional discussion and perhaps disagreement as others may have slightly different approaches but the essentials are what I'm trying to convey here.
In the scenario you're positing, the cavalry charge would signal disconnection of the autopilot long before speed was lost simply because of the loss of the PRIMs. The single chime would announce the disengagement of the autothrust and would also be continuously sounding, announcing new ECAM messages which would be appearing on the lower ECAM and which would be continuously re-prioritizing. As to which ECAM procedure would be prioritized, I have no idea but there would be a lot of them but that's what we train for.
To this end, as I have described before, great discipline would be required under such circumstances waiting until the airplane and warnings settled down so one could do the drills. The absolute first priority is flying the airplane by pitch attitude (which they had) and power both of which should instantly be in the hands of the PF; that is what the Unreliable Airspeed drill is all about. BTW, the unreliable airspeed abnormal does not come up on the ECAM - the first few items are memorized, (which should be obvious) and the entire drill is in the QRH. Examples of the AF drill are shown in the Appendices of the BEA 2nd Interim Report.
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quote PJ2
Unless you encounter a double engine failure/flame out, where Airbus instructs NOT to follow ECAM, as it could lead to wrong decisions/switchings!!
In such a high risk upset you have to grab the QRH in the semi-dark and start reading and acting .......
Brilliant job indeed.
Airbus did a brilliant job. The ECAM warnings and drills are extremely well thought out and works providing the crew are very strictly disciplined and follow the ECAM drills to the letter, and right to the very end of the drill.
In such a high risk upset you have to grab the QRH in the semi-dark and start reading and acting .......
Brilliant job indeed.
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BEA - Press Release 15 March 2010
Flight AF 447 on 1st june 2009
A330-203, registered F-GZCP
Information, 15 March 2010
The arrival of the « Anne Candies » from the United States has been delayed, as the BEA announced in a previous release. Arrival in Recife is now planned around 24 March, depending on the sea conditions encountered. It will join the « Seabed Worker » there.
A stopover is planned for the transfer of the equipment transported by the « Anne Candies » onto the « Seabed Worker », and to take on fuel. During this short stopover, the BEA will hold a press conference in the presence of the teams of investigators and those involved in the sea and undersea search operations.
Given the uncertainties surrounding the date of arrival of the « Anne Candies » and the length of the stopover, the date of this press conference cannot be set until Friday 19 March at the earliest.
Link to above - Information, 15/03/2010
-------------------
mm43
A330-203, registered F-GZCP
Information, 15 March 2010
The arrival of the « Anne Candies » from the United States has been delayed, as the BEA announced in a previous release. Arrival in Recife is now planned around 24 March, depending on the sea conditions encountered. It will join the « Seabed Worker » there.
A stopover is planned for the transfer of the equipment transported by the « Anne Candies » onto the « Seabed Worker », and to take on fuel. During this short stopover, the BEA will hold a press conference in the presence of the teams of investigators and those involved in the sea and undersea search operations.
Given the uncertainties surrounding the date of arrival of the « Anne Candies » and the length of the stopover, the date of this press conference cannot be set until Friday 19 March at the earliest.
Link to above - Information, 15/03/2010
-------------------
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Does anyone other that me get the idea that perhaps the airplane etc does not want to be found. From where I sit, the delays are dumb founding, and the silence deafning. The longer the procrastination, the more likely, no airplane, leaving the way to determine what ever cause seems to fit the situation. Hello Concord.
ww
ww
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Originally Posted by PJ2
I wonder if you meant pitch attitude? The AoA at stall is, just guessing, going to be around 14 to 18deg perhaps a bit higher given the wing:
Never been there by chance but would be very surprised by such AoA figures ... !?
For 212k kg, FL350 the pitch attitude at AlphaProt is almost 9deg
I believe the numbers produced by HN39 for the AoA make more sense, I would be interested to know how he did estimate them ?
ww, you're pretty close ...
AoA
Probably been said before better.
FWIW, clean, the wing will stall between 11-12 alpha, without the activity of autoslats (don't know if the A330 would have that at FL350...).
What the crew face is a known area of turbulence, likely causing variations of ATT, Mno, THR, and some short period variations of IVSI & ALT. At some point in the encounter, the pitots fail causing erroneous CAS data, which upsets the PFD CAS/Mno displayed, and would affect the ATR THR settings by altering the targets. (IIRC, the EPRL will still be correctly set though using the engines own P1/T1 probes). The only real indication of speed for the crew is the ATT of the aircraft which is being affected by turbulence... and so is difficult to evaluate. The alpha is not displayed on the PFD's as a discrete display, (on Boeing's the AoA vanes provide one of the inputs to the minimum speed displayed on the PFD... don't know about A330's)
The stall warning would still be valid if occurring, but may occur at the same time that the crew get ambiguous warnings such as overspeed etc. Coupled to all of this is that until the PRIM/SEC detect that sensor error(s) exists, the flight controls are getting inputs from false data, including potentially both high and/or low CAS conditions where FBW envelope protections occur.
This condition is bad enough in day/VMC conditions, in night/IMC/turbulence, distinguishing what the error is and what valid sources exist would be challenging.
This event also follows the QFA072 A330 upset where the causal factor was the AoA vane data to the ADIRS.
The final indicator of performance remaining to the crew was the pitch ATT (theta) relative to the horizon, which infers the AoA, and therefore CAS. This is functionally removed due to the turbulent state as being accurate information.
IMHO, what is surprising is that on numerous occasions previously, this form of ADIRS data failure has not caused an accident.
The recovery from an upset without valid primary data is at best difficult, and in night/IMC I would wager improbable for the first crews to encounter such a case. Would the next crew fare better? I would hope so.
[note: if the A330 does have autoslat capability at altitude, the potential for aggravation of the flightpath management exists, they cause no end of problem at high mach... I don't have the books here with me at home to check the AI systems...]
regards,
FDR.
FWIW, clean, the wing will stall between 11-12 alpha, without the activity of autoslats (don't know if the A330 would have that at FL350...).
What the crew face is a known area of turbulence, likely causing variations of ATT, Mno, THR, and some short period variations of IVSI & ALT. At some point in the encounter, the pitots fail causing erroneous CAS data, which upsets the PFD CAS/Mno displayed, and would affect the ATR THR settings by altering the targets. (IIRC, the EPRL will still be correctly set though using the engines own P1/T1 probes). The only real indication of speed for the crew is the ATT of the aircraft which is being affected by turbulence... and so is difficult to evaluate. The alpha is not displayed on the PFD's as a discrete display, (on Boeing's the AoA vanes provide one of the inputs to the minimum speed displayed on the PFD... don't know about A330's)
The stall warning would still be valid if occurring, but may occur at the same time that the crew get ambiguous warnings such as overspeed etc. Coupled to all of this is that until the PRIM/SEC detect that sensor error(s) exists, the flight controls are getting inputs from false data, including potentially both high and/or low CAS conditions where FBW envelope protections occur.
This condition is bad enough in day/VMC conditions, in night/IMC/turbulence, distinguishing what the error is and what valid sources exist would be challenging.
This event also follows the QFA072 A330 upset where the causal factor was the AoA vane data to the ADIRS.
The final indicator of performance remaining to the crew was the pitch ATT (theta) relative to the horizon, which infers the AoA, and therefore CAS. This is functionally removed due to the turbulent state as being accurate information.
IMHO, what is surprising is that on numerous occasions previously, this form of ADIRS data failure has not caused an accident.
The recovery from an upset without valid primary data is at best difficult, and in night/IMC I would wager improbable for the first crews to encounter such a case. Would the next crew fare better? I would hope so.
[B]"Learning is not compulsory... neither is survival" [/B
]W.Edwards Deeming (1900 - 1993)
[note: if the A330 does have autoslat capability at altitude, the potential for aggravation of the flightpath management exists, they cause no end of problem at high mach... I don't have the books here with me at home to check the AI systems...]
regards,
FDR.
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Does anyone other that me get the idea that perhaps the airplane etc does not want to be found. From where I sit, the delays are dumb founding, and the silence deafning. The longer the procrastination, the more likely, no airplane, leaving the way to determine what ever cause seems to fit the situation. Hello Concord.
ww
ww
Could you please start your own AF447-bat thread, and take your ignorance there, rather than act the fool here?
By the way, there once was an aircraft called Concorde... but I suppose you are referring to the battle of Concord?
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Originally Posted by fdr
FWIW, clean, the wing will stall between 11-12 alpha, without the activity of autoslats (don't know if the A330 would have that at FL350...)
The alpha is not displayed on the PFD's as a discrete display, (on Boeing's the AoA vanes provide one of the inputs to the minimum speed displayed on the PFD... don't know about A330's)
CONF iture;
Well, I hesitated using the CBT for this very reason but did so because these speeds (but not the pitch although I have no basis to doubt it) were independently verified as accurate from book sources.
For clarity, the term "Angle of Incidence" is sometimes used instead of "Angle of Attack". I know also "incidence" means the angle at which the wing is mounted on the fuselage, (chord vs longitudinal axis).
Of course, pitch attitude and AoA are entirely independent of one another.
Recovery from the stall is part of the script for initial conversion. From simulator experience during initial training on the airplane the pitch attitudes described and on the CBT are in the ball park, perhaps higher.
(To get the simulator to actually stall, a failure has to occur so the airplane is in Alternate (or Direct) Law. It takes a great deal of back-stick pressure to get the airplane to stall. In my recollection it was very docile, at low altitude, (14,000ft AGL, anyway.)
We don't know what the AoA was during the exercise of course because there is no cockpit indication of such. Traditionally the industry has never used AoA because for any specific weight there is a direct, corresponding relationship between CAS and AoA regardless of altitude. "For every air speed - as indicated on the Air Speed Indicator - there is a corresponding angle of attack at which level flight can be maintained (provided the weight of the aeroplane does not change)" - Kermode, Mechanics of Flight, 1962.
The actual VS is not displayed in the A330. AlphaMax is VS 1.0g and is slightly higher than VS, (explained below). VLS is 1.23 VS 1.0g for the approach phase. Vapp is VLS +5kts plus FMGC-added wind to maintain the energy of the aircraft in strong winds and/or shear conditions.
From actual experience with flight data, for Vref +5kts (which is "Vapp" in the A320), on approach we will typically see AoA's of 5 to 6deg with pitch attitudes of 2 to 3 degrees at 1.23VS 1.0g. So "6deg of AoA" is not close to the stall.
On my "guess" regarding the AoA, I thought of Davies' diagram, (Davies uses the term, "Angle of Incidence" or just plain "incidence"), in which the C/Lmax occurs at around 18deg AoA or incidence. Now I fully realize that Davies' work is dated and the diagram is (necessarily) generic but in the absence of solid information anywhere, I posited the notion that an AoA for a swept wing on a transport to stall would be around 14-18 degrees. It's not 6 or 7.
The following is from the FCOM regarding VS:
So regarding AoA, this leaves us with an open question which may or may not be thread drift depending upon what the recorders have to say. If they are found...
As always I am happy to be corrected in any of this, with information or data that supports the opposite view. I'm posting for learning, not to be right or "win the debate".
PJ2
Originally Posted by CONF iture
At FL350 ?
Never been there by chance but would be very surprised by such AoA figures ... !?
To me your CBT autoflight software is not really representative performance wise, a simulator would be a better reference.
I believe the numbers produced by HN39 for the AoA make more sense, I would be interested to know how he did estimate them ?
Never been there by chance but would be very surprised by such AoA figures ... !?
Originally Posted by PJ2
Quote:
For 212k kg, FL350 the pitch attitude at AlphaProt is almost 9deg
For 212k kg, FL350 the pitch attitude at AlphaProt is almost 9deg
I believe the numbers produced by HN39 for the AoA make more sense, I would be interested to know how he did estimate them ?
For clarity, the term "Angle of Incidence" is sometimes used instead of "Angle of Attack". I know also "incidence" means the angle at which the wing is mounted on the fuselage, (chord vs longitudinal axis).
Of course, pitch attitude and AoA are entirely independent of one another.
Recovery from the stall is part of the script for initial conversion. From simulator experience during initial training on the airplane the pitch attitudes described and on the CBT are in the ball park, perhaps higher.
(To get the simulator to actually stall, a failure has to occur so the airplane is in Alternate (or Direct) Law. It takes a great deal of back-stick pressure to get the airplane to stall. In my recollection it was very docile, at low altitude, (14,000ft AGL, anyway.)
We don't know what the AoA was during the exercise of course because there is no cockpit indication of such. Traditionally the industry has never used AoA because for any specific weight there is a direct, corresponding relationship between CAS and AoA regardless of altitude. "For every air speed - as indicated on the Air Speed Indicator - there is a corresponding angle of attack at which level flight can be maintained (provided the weight of the aeroplane does not change)" - Kermode, Mechanics of Flight, 1962.
The actual VS is not displayed in the A330. AlphaMax is VS 1.0g and is slightly higher than VS, (explained below). VLS is 1.23 VS 1.0g for the approach phase. Vapp is VLS +5kts plus FMGC-added wind to maintain the energy of the aircraft in strong winds and/or shear conditions.
From actual experience with flight data, for Vref +5kts (which is "Vapp" in the A320), on approach we will typically see AoA's of 5 to 6deg with pitch attitudes of 2 to 3 degrees at 1.23VS 1.0g. So "6deg of AoA" is not close to the stall.
On my "guess" regarding the AoA, I thought of Davies' diagram, (Davies uses the term, "Angle of Incidence" or just plain "incidence"), in which the C/Lmax occurs at around 18deg AoA or incidence. Now I fully realize that Davies' work is dated and the diagram is (necessarily) generic but in the absence of solid information anywhere, I posited the notion that an AoA for a swept wing on a transport to stall would be around 14-18 degrees. It's not 6 or 7.
Originally Posted by CONF iture
Not on the 330 but from memory, the AoA will trigger the stall warning.
For a conventional aircraft, the reference stall speed, VSmin, is based on a load factor that is less than 1g. This gives a stall speed that is lower than the stall speed at 1g. All operating speeds are expressed as functions of this speed. (For example, VREF = 1.3 VSmin).
Because the aircraft has a low-speed protection feature (alpha limit) that the flight crew cannot override, the airworthiness authorities have reconsidered the definition of stall speed for this aircraft.
All the operating speeds must be referenced to a speed that can be demonstrated by flight test. This speed is designated VS1g.
Airworthiness authorities have agreed that a factor of 0.94 represents the relationship between VS1g for this aircraft and VSmin for conventional aircraft types. As a result the authorities allow this aircraft to use the following factors:
V2=1.2 * 0.94 VS1g = 1.13 VS1g
VREF=1.3 * 0.94 VS1g = 1.23 VS1g
These speeds are identical to those that the conventional 94% rule would have defined for this aircraft. The aircraft has exactly the same maneuver margin that a conventional aircraft would have at its reference speeds.
The AOM uses VS for VS1g.
Because the aircraft has a low-speed protection feature (alpha limit) that the flight crew cannot override, the airworthiness authorities have reconsidered the definition of stall speed for this aircraft.
All the operating speeds must be referenced to a speed that can be demonstrated by flight test. This speed is designated VS1g.
Airworthiness authorities have agreed that a factor of 0.94 represents the relationship between VS1g for this aircraft and VSmin for conventional aircraft types. As a result the authorities allow this aircraft to use the following factors:
V2=1.2 * 0.94 VS1g = 1.13 VS1g
VREF=1.3 * 0.94 VS1g = 1.23 VS1g
These speeds are identical to those that the conventional 94% rule would have defined for this aircraft. The aircraft has exactly the same maneuver margin that a conventional aircraft would have at its reference speeds.
The AOM uses VS for VS1g.
As always I am happy to be corrected in any of this, with information or data that supports the opposite view. I'm posting for learning, not to be right or "win the debate".
PJ2
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Anne Candies
To view an Atlantic significant wave direction and height animation for H to H+180 hours, go to -
North Atl Animation
The predominate wind and sea conditions along the northern South American coast are 060°T/20KTS height 9FT/2.5M becoming 090°T/5-10TS height 3FT/1M in next 5 days.
It would seem the vessel is not handling the conditions that well, and the North Brazilian current is very strong at this time of the year, which wont be helping. An approximate position for the vessel at 1200z 16 March 2010 is 4°45N 49°00W. The distance from Grand Isle to Recife is 3976NM.
mm43
North Atl Animation
The predominate wind and sea conditions along the northern South American coast are 060°T/20KTS height 9FT/2.5M becoming 090°T/5-10TS height 3FT/1M in next 5 days.
It would seem the vessel is not handling the conditions that well, and the North Brazilian current is very strong at this time of the year, which wont be helping. An approximate position for the vessel at 1200z 16 March 2010 is 4°45N 49°00W. The distance from Grand Isle to Recife is 3976NM.
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AoA etc.
RE: CONF iture #514
The numbers are based on the relation between Liftcoëfficient and AoA which I derived from FDR data on an unvoluntary pitch-down/pitch-up maneuver of an A330 in flight QF72 as reported by the australian ATSB. Unfortunately the report does not provide the weight of the airplane and the ambient temperature at the time of the upset, which are essential parameters for this derivation. I have mailed a request for these data to the ATSB but got no reply. The derivation is based on my best estimate for these two numbers and I would be most grateful to anybody having more accurate information.
regards,
HN39
I believe the numbers produced by HN39 for the AoA make more sense, I would be interested to know how he did estimate them ?
regards,
HN39
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Interesting HN39, thanks.
Regarding QF72, for the temp I don't know, but for the weight, my guess would be somewhere between 187 and 185T ? as the event happened after 3:10 of flight time and TOW was at 207T.
That's the part in red I'm not sure about, but I don't have the knowledge so I'll keep it quiet, maybe someone would explain more ... ?
The best would be to flight test these lower speeds during a ferry at FL something, but I still need/like my job.
Regarding QF72, for the temp I don't know, but for the weight, my guess would be somewhere between 187 and 185T ? as the event happened after 3:10 of flight time and TOW was at 207T.
Originally Posted by PJ2
We don't know what the AoA was during the exercise of course because there is no cockpit indication of such. Traditionally the industry has never used AoA because for any specific weight there is a direct, corresponding relationship between CAS and AoA regardless of altitude. "For every air speed - as indicated on the Air Speed Indicator - there is a corresponding angle of attack at which level flight can be maintained (provided the weight of the aeroplane does not change)" - Kermode, Mechanics of Flight, 1962.
The best would be to flight test these lower speeds during a ferry at FL something, but I still need/like my job.