A320 tailstrike after radalt failures
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neville_nobody
Agreed!
I have flown with B707 (freighters) guys who could land a B707 with the stick shaker rattling away just before a perfectly smooth touch down at Max LDG WGT! No rad alt call outs either. Share flying skills came to the fore. Yes they were good flyer's.
Where have all the skills gone? Where has the marvelous simplicity of a real aircraft gone??
Agreed!
I have flown with B707 (freighters) guys who could land a B707 with the stick shaker rattling away just before a perfectly smooth touch down at Max LDG WGT! No rad alt call outs either. Share flying skills came to the fore. Yes they were good flyer's.
Where have all the skills gone? Where has the marvelous simplicity of a real aircraft gone??
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Okay, so if you know the AB really well, you're more likely to arrive in similar condition as you left. I keep reading accident reports here and there, they start to run together, but sure read my fill of Normal Law, Alternate Law, Direct Law and rapid changes from one mode to the next, apparently overwhelming even the most rootin-tootin, knowledgable pilots... lets say stall protection "practice" in the landing pattern for one example.
And which Airbus incident/ crash was the one where bogus flight recorders were turned over to authorities???
How about Captain Sully of supreme aviator skill....he tried to command the aircraft to trade a little more energy to lessen his rate of descent in the final few feet of flare.... but OH NO Captain, the magic computer here won't allow you to finesse the last few feet of your flight, for it knows better than you the energy state of the airplane.... yes a successful outcome, but had Sully been permitted to actually fully command the controls.....
Curious about the tailstrike aircraft of this thread... Is it one of the AB that makes throttle movements, but doesn't bother to actually move the levers on the flight deck? I am not saying it has anything to do with the incident, just wondering.
And which Airbus incident/ crash was the one where bogus flight recorders were turned over to authorities???
How about Captain Sully of supreme aviator skill....he tried to command the aircraft to trade a little more energy to lessen his rate of descent in the final few feet of flare.... but OH NO Captain, the magic computer here won't allow you to finesse the last few feet of your flight, for it knows better than you the energy state of the airplane.... yes a successful outcome, but had Sully been permitted to actually fully command the controls.....
Curious about the tailstrike aircraft of this thread... Is it one of the AB that makes throttle movements, but doesn't bother to actually move the levers on the flight deck? I am not saying it has anything to do with the incident, just wondering.
SKS777FLYER;
No, not the energy state of the airplane....it knows the AoA.
As the report states, the aircraft was in "AlphaProt" mode from 150' to touchdown, (it would not have entered this mode below 100' as the mode is inhibited below that height). This provided maximum protection against stalling the aircraft in from a substantial height while maintaining sufficient energy to do so while using full back-stick.
From the Report:
"[B]elow 50', the alpha-protection threshold value increased from 14.5deg to 15.5deg. - p.48
"The airplane touched down....at an AoA of between 13deg and 14deg, ..." - p.48
So the aircraft was close to the stall. To your point then, how much more energy, for how long, did this aircraft have?
The question is open for debate but I'm not sure what the point would be. I agree with you that the discussion could be fine-tuned to argue possibility, - that an aircraft (B737, MD80, Embraer, Bombardier, etc) without such protection may have had very slightly more to contribute to arrest the final rate of descent, (12.5fps, essentially the high side of normal, but touchdown without the flare) but then again, maybe not, and pulling back would just have increased the rate of descent with a much higher pitch angle and far harder touchdown especially for the forward section of the fuselage. To my knowledge, no one has run such a scenario.
No one can argue with the outcome even if a finely-tuned argument may say that less fuselage damage may have provided longer flotation, etc, etc, but the outcome is what it is.
Cheers,
PJ2
but OH NO Captain, the magic computer here won't allow you to finesse the last few feet of your flight, for it knows better than you the energy state of the airplane....
As the report states, the aircraft was in "AlphaProt" mode from 150' to touchdown, (it would not have entered this mode below 100' as the mode is inhibited below that height). This provided maximum protection against stalling the aircraft in from a substantial height while maintaining sufficient energy to do so while using full back-stick.
From the Report:
"[B]elow 50', the alpha-protection threshold value increased from 14.5deg to 15.5deg. - p.48
"The airplane touched down....at an AoA of between 13deg and 14deg, ..." - p.48
So the aircraft was close to the stall. To your point then, how much more energy, for how long, did this aircraft have?
The question is open for debate but I'm not sure what the point would be. I agree with you that the discussion could be fine-tuned to argue possibility, - that an aircraft (B737, MD80, Embraer, Bombardier, etc) without such protection may have had very slightly more to contribute to arrest the final rate of descent, (12.5fps, essentially the high side of normal, but touchdown without the flare) but then again, maybe not, and pulling back would just have increased the rate of descent with a much higher pitch angle and far harder touchdown especially for the forward section of the fuselage. To my knowledge, no one has run such a scenario.
No one can argue with the outcome even if a finely-tuned argument may say that less fuselage damage may have provided longer flotation, etc, etc, but the outcome is what it is.
Cheers,
PJ2
SKS777FLYER;
No, not the energy state of the airplane....it knows the AoA.
As the report states, the aircraft was in "AlphaProt" mode from 150' to touchdown, (it would not have entered this mode below 100' as the mode is inhibited below that height). This provided maximum protection against stalling the aircraft from a substantial height while maintaining sufficient energy to control the touchdown using full back-stick.
From the Report:
"[B]elow 50', the alpha-protection threshold value increased from 14.5deg to 15.5deg. - p.48
"The airplane touched down....at an AoA of between 13deg and 14deg, ..." - p.48
So the aircraft was close to the stall. To your point then, how much more energy, for how long, did this aircraft have?
The question is open for debate but I'm not sure what the point would be. I agree with you that the discussion could be fine-tuned to argue possibility, - that an aircraft (B737, MD80, Embraer, Bombardier, etc) without such protection may have had very slightly more to contribute to arrest the final rate of descent, (12.5fps, essentially the high side of normal, but touchdown without the flare) but then again, maybe not, and pulling back would just have increased the rate of descent with a much higher pitch angle and far harder touchdown especially for the forward section of the fuselage. To my knowledge, no one has run such a scenario.
No one can argue with the outcome even if a finely-tuned argument may say that less fuselage damage may have provided longer flotation, etc, etc, but the outcome is what it is.
Cheers,
PJ2
but OH NO Captain, the magic computer here won't allow you to finesse the last few feet of your flight, for it knows better than you the energy state of the airplane....
As the report states, the aircraft was in "AlphaProt" mode from 150' to touchdown, (it would not have entered this mode below 100' as the mode is inhibited below that height). This provided maximum protection against stalling the aircraft from a substantial height while maintaining sufficient energy to control the touchdown using full back-stick.
From the Report:
"[B]elow 50', the alpha-protection threshold value increased from 14.5deg to 15.5deg. - p.48
"The airplane touched down....at an AoA of between 13deg and 14deg, ..." - p.48
So the aircraft was close to the stall. To your point then, how much more energy, for how long, did this aircraft have?
The question is open for debate but I'm not sure what the point would be. I agree with you that the discussion could be fine-tuned to argue possibility, - that an aircraft (B737, MD80, Embraer, Bombardier, etc) without such protection may have had very slightly more to contribute to arrest the final rate of descent, (12.5fps, essentially the high side of normal, but touchdown without the flare) but then again, maybe not, and pulling back would just have increased the rate of descent with a much higher pitch angle and far harder touchdown especially for the forward section of the fuselage. To my knowledge, no one has run such a scenario.
No one can argue with the outcome even if a finely-tuned argument may say that less fuselage damage may have provided longer flotation, etc, etc, but the outcome is what it is.
Cheers,
PJ2
Originally Posted by A4
Double RA failure means you go from "normal law" to " direct law" when the gear is lowered. Usually the sequence is NORM-ALTN-DIRECT.
Originally Posted by DC-ATE
I'm curious as to WHY, in the Airbus, a double radar altimeter failure causes the aircraft to change 'laws' ?!
Originally Posted by Rananim
IF I have dual RA fail on Boeing,its a total non-event.I fly the plane.No this law or that law.
Boeings FBW aircraft have 3 flight control laws as well, normal, secondary, and direct.
Originally Posted by neville_nobody
And Qantas had the same failure in a 737 and it resulted in a normal landing because the pilots knew what they were doing and can actually hand fly an aeroplane. The issue at play here is the Airbus system and the change of flight laws in a very critical stage of flight.
What happens to thrust in the reported scenario? Landing is usually a combination of pitch and thrust.
If in auto thrust, does the RA trigger a thrust reduction for the flare? If so, and if this was early due to a malfunction or failure, then the crew if unaware of the situation could end up slower than they might expect resulting in a slow/nose high landing?
What triggers the ‘Retard’ call? If this involves the RA, then would a malfunction lead the crew, by habit, to move the thrust levers to idle earlier than normal, again encouraging to a slow/nose high arrival?
If in auto thrust, does the RA trigger a thrust reduction for the flare? If so, and if this was early due to a malfunction or failure, then the crew if unaware of the situation could end up slower than they might expect resulting in a slow/nose high landing?
What triggers the ‘Retard’ call? If this involves the RA, then would a malfunction lead the crew, by habit, to move the thrust levers to idle earlier than normal, again encouraging to a slow/nose high arrival?
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Autothrust is still available, and when the autopilot is disconnect will never command idle thrust no matter what law the FBW is in (assuming no exotic failure combination).
If you flare and leave the thrust levers where they are they will happily give you more power and you'll fly along the runway at 10'.
The thrust levers are normally closed before you hear the 'Retard' call which is triggered by the Radalt, so you would get neither the 50,40 etc nor 'Retard'.
Possible distraction in this scenario could be an autothrust increase/decrease leading to an unexpected pitching moment.
If you flare and leave the thrust levers where they are they will happily give you more power and you'll fly along the runway at 10'.
The thrust levers are normally closed before you hear the 'Retard' call which is triggered by the Radalt, so you would get neither the 50,40 etc nor 'Retard'.
Possible distraction in this scenario could be an autothrust increase/decrease leading to an unexpected pitching moment.
Ut Sementem Feeceris
swh said:
I'd be interested in your source for this. Are you referring to Airbus narrow body or 330/340?
I have the A320 FCOM infront of me and for RA1+2 Fault it clearly states:
Both RA FAULT:
When L/G DN: DIRECT LAW
At landing gear extension, flight controls revert to direct law in
pitch, as well as in roll (see DIRECT LAW procedure 3.02.27).
CAT 1 ONLY
ILS APPR mode cannot be engaged; LOC mode is available via
the FCU LOC pushbutton.
A4
No, when gear is selected down, it will transition to flare law without the nose down bias.
I have the A320 FCOM infront of me and for RA1+2 Fault it clearly states:
Both RA FAULT:
When L/G DN: DIRECT LAW
At landing gear extension, flight controls revert to direct law in
pitch, as well as in roll (see DIRECT LAW procedure 3.02.27).
CAT 1 ONLY
ILS APPR mode cannot be engaged; LOC mode is available via
the FCU LOC pushbutton.
A4
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CONF iture,
I have many times and have also spoken to several people involved in the investigation.
arba,
I am NOT commenting on the jetBlue incident until the investigation is done and the report is out. So NO, I do not agree with you.
G
I have many times and have also spoken to several people involved in the investigation.
arba,
I am NOT commenting on the jetBlue incident until the investigation is done and the report is out. So NO, I do not agree with you.
G
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And.....could someone point me to a link regarding the 737 crash because of a radar altimeter failure?
http://www.onderzoeksraad.nl/docs/ra...TA_ENG_web.pdf
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Hudson report page 97
The A320 alpha-protection mode incorporates features that can attenuate pilot sidestick pitch inputs. Because of these features, the airplane could not reach the maximum AOA attainable in pitch normal law for the airplane weight and configuration
The A320 alpha-protection mode incorporates features that can attenuate pilot sidestick pitch inputs. Because of these features, the airplane could not reach the maximum AOA attainable in pitch normal law for the airplane weight and configuration
I think this characteristic of the Airbus is pretty obscure to everyone, except maybe to the Airbus engineering.
Sully would have had a much better flare without that intervention of additional features built into the system which attenuate pilot sidestick pitch inputs, preventing the airplane from reaching the maximum AOA.
His speed was low, but as proved by AoA + attitude data, there was ample space for touchdown improvement as requested by the pilot.
There was still a margin of 3.5 degrees to reach alpha max, and probably 3 additional degrees to reach the AoA for a stall.
The features prevented the pilot to flare the airplane as he would have loved.
For a ditching, Airbus recommends a touchdown with approximately 11 degrees of pitch and minimum aircraft vertical speed, but despite the full backstick, the protections did not allow more than 9.5 degrees and the pilots could do nothing to decrease that impressive vertical speed of 750 feet a minute.
I believe Sully would have obtained a better touchdown on his own without the protections interfering with his experience.
Originally Posted by guiones
and have also spoken to several people involved in the (Habsheim) investigation.
For the record :
What was "V alfa MAX" ?
What was the corresponding AoA ?
Quotes from the report will be appreciated.
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CONF iture
http://www.bea.aero/docspa/1988/f-kc...f-kc880626.pdf
Estimated weight 59 to 60 Tons P. 8
Minimum speed 112 Kts P. 10, 37
VLS from AFR QRH (Rev 42, Sec 020, MSN 0003-0019) 60 Tons 140 Kts
Estimated V Alpha Max 110 Kts. Within acceptable margin.
As you know AoA would vary to maintain V Alpha Max with engines at idle.
G
http://www.bea.aero/docspa/1988/f-kc...f-kc880626.pdf
Estimated weight 59 to 60 Tons P. 8
Minimum speed 112 Kts P. 10, 37
VLS from AFR QRH (Rev 42, Sec 020, MSN 0003-0019) 60 Tons 140 Kts
Estimated V Alpha Max 110 Kts. Within acceptable margin.
As you know AoA would vary to maintain V Alpha Max with engines at idle.
G
Originally Posted by A4
I'd be interested in your source for this. Are you referring to Airbus narrow body or 330/340?
Your reference to FCOM 3 does not show direct law in all 3 axis (like triple IR), and in pitch you still have pitch rate feedback.
This is an excerpt from the Airbus A320 instructors manual.
9 - DOUBLE RADIO ALTIMETER FAILURE
The double Radio Altimeter (R/A) failure has various consequences on many systems of the a/c, since the R/A information is used to switch flight control laws or AP - ATHR modes etc. or in auto call outs and warnings. It is clearly materialized by RA red flag on PFD (just underneath the horizon).
The procedure is simple, since the ECAM provides all required information. However, the consequences of such malfunction affect the a/c normal operations in many directions.
Consequences upon Fly by Wire systems:
Rather than using R/A information, the FBW systems use the LGCIU outputs for most of the logics.
a. APPROACH
- The flare law (usually blended in at 50 ft) engages when the landing gear is extended.
- The warning USE MANUAL PITCH TRIM comes up few seconds later on PFD, in order to remind the crew that the remainder of the approach is to be flown in a comfortable direct law (with pitch rate feed back).
b. LANDING
- The ground law engages when MLG is compressed and pitch attitude is less than 2.5°.
- The ground spoilers extend using wheel speed information.
c. WARNINGs
- The low energy warning is lost in case of double R/A malfunction.
Consequences for FMGC:
Basically LAND modes do not engage, since it ensures that (for autoland) subsequently FLARE and ROLLOUT will engage which is not possible as the R/A information is missing.
Consequently (landing gear extended):
- FD basic modes available only,
- approach modes are not available (no LOC, no G/S),
- autoland modes are not available (no LAND, no FLARE, no ROLLOUT),
- ATHR remains in speed mode, in approach (no RETARD),
- APs are lost.
Consequences for GPWS / EGPWS:
Most functions require R/A signal information. Therefore GPWS and EGPWS, if applicable, are lost.
The double Radio Altimeter (R/A) failure has various consequences on many systems of the a/c, since the R/A information is used to switch flight control laws or AP - ATHR modes etc. or in auto call outs and warnings. It is clearly materialized by RA red flag on PFD (just underneath the horizon).
The procedure is simple, since the ECAM provides all required information. However, the consequences of such malfunction affect the a/c normal operations in many directions.
Consequences upon Fly by Wire systems:
Rather than using R/A information, the FBW systems use the LGCIU outputs for most of the logics.
a. APPROACH
- The flare law (usually blended in at 50 ft) engages when the landing gear is extended.
- The warning USE MANUAL PITCH TRIM comes up few seconds later on PFD, in order to remind the crew that the remainder of the approach is to be flown in a comfortable direct law (with pitch rate feed back).
b. LANDING
- The ground law engages when MLG is compressed and pitch attitude is less than 2.5°.
- The ground spoilers extend using wheel speed information.
c. WARNINGs
- The low energy warning is lost in case of double R/A malfunction.
Consequences for FMGC:
Basically LAND modes do not engage, since it ensures that (for autoland) subsequently FLARE and ROLLOUT will engage which is not possible as the R/A information is missing.
Consequently (landing gear extended):
- FD basic modes available only,
- approach modes are not available (no LOC, no G/S),
- autoland modes are not available (no LAND, no FLARE, no ROLLOUT),
- ATHR remains in speed mode, in approach (no RETARD),
- APs are lost.
Consequences for GPWS / EGPWS:
Most functions require R/A signal information. Therefore GPWS and EGPWS, if applicable, are lost.
Originally Posted by CONF iture
His speed was low, but as proved by AoA + attitude data, there was ample space for touchdown improvement as requested by the pilot.
There was still a margin of 3.5 degrees to reach alpha max, and probably 3 additional degrees to reach the AoA for a stall.
The features prevented the pilot to flare the airplane as he would have loved.
For a ditching, Airbus recommends a touchdown with approximately 11 degrees of pitch and minimum aircraft vertical speed, but despite the full backstick, the protections did not allow more than 9.5 degrees and the pilots could do nothing to decrease that impressive vertical speed of 750 feet a minute.
There was still a margin of 3.5 degrees to reach alpha max, and probably 3 additional degrees to reach the AoA for a stall.
The features prevented the pilot to flare the airplane as he would have loved.
For a ditching, Airbus recommends a touchdown with approximately 11 degrees of pitch and minimum aircraft vertical speed, but despite the full backstick, the protections did not allow more than 9.5 degrees and the pilots could do nothing to decrease that impressive vertical speed of 750 feet a minute.
You assertions that a higher attitude or AoA would have resulted in a better outcome are not based upon any fact. Vertical speed is the killer, and I have yet to see a single aerodynamics text that states that minimum vertical speed is only achieved at maximum AoA or maximum pitch angle.
Even on the 777/787 (QRH Ditching checklist) they say to maintain VREF+30 until touchdown and flare to achieve the minimum rate of descent. Even Boeing does not advocate maximum AoA or pitch attitudes, they advocate minimum ROD.
Fact is the aircraft landed intact, and all passengers and crew walked away without a single loss of life, something that is very rare with any forced landing on water, regardless of the aircraft size.
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As we all know, a water landing requires a precise attitude at touchdown that doesn't put the airplane in a stall before touchdown in the water. Sully did it perfectly so even though I hate Airbuses and give no credit to Airbus for his successful ditching I think he did a wonderful job of saving those passengers.
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I dont know if you guy have a "special" model 320, But as per our FCOMs for the (319,320,321) 3.02.34 below is a snipit,
Both RA FAULT
When LG down: Direct law. At landing gear extension flight controls revert to direct law in Pitch as well as in roll (see direct law procedure 2.02.27)
Dunno if that will clarify, But I agree a dual Ra fault in the Flare would not be a fun situation!
Both RA FAULT
When LG down: Direct law. At landing gear extension flight controls revert to direct law in Pitch as well as in roll (see direct law procedure 2.02.27)
Dunno if that will clarify, But I agree a dual Ra fault in the Flare would not be a fun situation!
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so, the magic plane has lost its charm.
spending so much time making a plane that does so much for you instead of building a strong, reliable, SIMPLE plane...tsk tsk tsk.
more pilot training...more simple planes that don't have bad habits.
spending so much time making a plane that does so much for you instead of building a strong, reliable, SIMPLE plane...tsk tsk tsk.
more pilot training...more simple planes that don't have bad habits.
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1)my understanding is that flare law on A320 is a variation of normal law, pitch attitude at 50 feet is memorised and at 30 feet is reduced -2 degrees over 8 seconds to create an artificial feel. Other than above, I have never heard of entering flare law with gear down or alternate flare law and wonder whether they relate to a different type.
2) it is easy to confuse alpha-prot (an angle of attack protection) with alpha-floor (an auto thrust function not available below 100 feet)
3) In the simulator, I find setting, trimming and holding an accurate pitch attitude in direct law is quite tricky as there is no "feel" .It is not like a 737 and for those who suggest this scrape is due to lack of skill, a late change to direct law would make it very easy to over control during the flare.
2) it is easy to confuse alpha-prot (an angle of attack protection) with alpha-floor (an auto thrust function not available below 100 feet)
3) In the simulator, I find setting, trimming and holding an accurate pitch attitude in direct law is quite tricky as there is no "feel" .It is not like a 737 and for those who suggest this scrape is due to lack of skill, a late change to direct law would make it very easy to over control during the flare.