A320 and the Miracle on the Hudson
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@ I-2021
We still need Hyd actuators to move the surfaces (G/Y for THS and G/Y/B for Rudders). This is unlikely in this scenario. However, if you have Hyds going, the Bus can be flown. I actually managed to "get her down" on one of the two occasions attempted during sims.
We still need Hyd actuators to move the surfaces (G/Y for THS and G/Y/B for Rudders). This is unlikely in this scenario. However, if you have Hyds going, the Bus can be flown. I actually managed to "get her down" on one of the two occasions attempted during sims.
the question raised was about a total loss of electrical power, not hydraulic power.
What in my mind demonstrates Captain Sullenberger's professionalism aside from his flying of the aircraft is that he knew, from studying and knowing his aircraft, that the correct ditching attitude was 11 degrees. A very small note in the QRH states this. Any more than that and the aircraft would have slammed down on the water, any less and the engines would have "bit" into the water and caused a break-up.
For those who start waffling on about Alpha floor look at Fatflyers post.
For those who start waffling on about Alpha floor look at Fatflyers post.
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Originally Posted by Lookleft
What in my mind demonstrates Captain Sullenberger's professionalism aside from his flying of the aircraft is that he knew, from studying and knowing his aircraft, that the correct ditching attitude was 11 degrees. A very small note in the QRH states this. Any more than that and the aircraft would have slammed down on the water, any less and the engines would have "bit" into the water and caused a break-up.
The 11 degrees attitude was refused to the pilot even if adequate margin in the AoA before attaining alpha max was available ...
He could not pull more than 9.5 degrees attitude in the flare due to obscure system restriction.
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thanks in advance
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Sully could have landed any airliner in the Hudson that day. He was an excellent pilot. He was restricted on how much he could pull up but he still planned the glide to a picture perfect ditching. His speed control kept the computer from screwing up his flare otherwise the computer would have put him in the Hudson at a high sink rate breaking up the airplane and costing many lives. If you can not flare beyond a certain AOA you can not break your descent rate.
Thanks for the correction CONF but my point was he knew what body angle he was after. Not sure if you are familiar with the Airbus QRH but the 11 degrees is a very small note in the ditching checklist. The main reason all survived was because of the experience and professionalism of the crew.
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Sully could have landed any airliner in the Hudson that day. He was an excellent pilot. He was restricted on how much he could pull up but he still planned the glide to a picture perfect ditching. His speed control kept the computer from screwing up his flare otherwise the computer would have put him in the Hudson at a high sink rate breaking up the airplane and costing many lives. If you can not flare beyond a certain AOA you can not break your descent rate.
FDR data indicated that the airplane was below green dot speed and at VLS or slightly less for most of the descent, and about 15 to 19 knots below VLS during the last 200 feet.
The NTSB concludes that the captain’s difficulty maintaining his intended airspeed during the final approach resulted in high AOAs, which contributed to the difficulties in flaring the airplane, the high descent rate at touchdown, and the fuselage damage. (See additional discussion in section 2.7.1.)
The NTSB concludes that the captain’s difficulty maintaining his intended airspeed during the final approach resulted in high AOAs, which contributed to the difficulties in flaring the airplane, the high descent rate at touchdown, and the fuselage damage. (See additional discussion in section 2.7.1.)
Note: before deciding I or NTSB are criticising the crew: Could it have been done better ? Sure - if flying an armchair with plenty of time to read up on it and a few goes to practice (and BA38 could have made the runway too...). On the day - excellent decision making, CRM and airmanship and the right result. Hampered by a checklist designed for use at 20000ft, he got the speeds a bit wrong and bent the airframe a bit more than he might have. I'll take that any day given those circumstances.
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Sully could have landed any Boeing in the Hudson as well as the Airbus. Don't give credit for his skillfull landing to a machine because Sully did it with his skill and nothing else. Airbus has a lot of automatic features but none of those helped him that day. His talent as a pilot saved all of those people, nothing else. We are all very proud of him.
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I hate to break up the mutual back slapping party, but just what were Sully's options?
- Slam into a skyscraper
- Do a 180 Glide back to the airport
- Make a left turn and land on miles of calm water.
He's not the first guy to ditch a plane, nor will he be the last, nor is he the first guy to have only one option and not be so stupid as to not take it.
- Slam into a skyscraper
- Do a 180 Glide back to the airport
- Make a left turn and land on miles of calm water.
He's not the first guy to ditch a plane, nor will he be the last, nor is he the first guy to have only one option and not be so stupid as to not take it.
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Sure, Sully did not go by the book when he speed was below Vls. However, he was smart enough to start the APU out of sequence. I think that was the single key event which most influenced the outcome as it kept the aircraft in normal law for the flare. (The NTSB has since recommended revamping the checklists and introducing ditching training with dual-engine failure.)
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Originally Posted by IF789
The computer didn't stop him flaring, or restrict him - his difficulty maintaining airspeed did that. He didn't have enough enegry to flare when he needed it.
He did have enough energy, not a ton, but enough to improve the touchdown. The system had decided otherwise.
Originally Posted by P98
The Airbus simulation indicated that the captain’s aft sidestick inputs in the last 50 feet of the flight were attenuated, limiting the ANU response of the airplane even though about 3.5° of margin existed between the airplane’s AOA at touchdown (between 13° and 14°) and the maximum AOA for this airplane weight and configuration (17.5°).
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From the NTSB report pages 97/98
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; however, the airplane did provide maximum performance for the weight and configuration at that time.
So the aircraft gave Sully the max performance that it could. A very different picture to the one presented if you only refer to the aircraft limiting AOA.
F speed for Config 2 was around 150kts and IAS was 125kts when he ditched (NTSB). So he was very close to the stall and was in fact in Alpha Protection from 150' rad alt. So far from the aircraft being at fault I would say that it perhaps saved them at this stage. Sully pulled full aft stick (in order to flare) close to the stall, had it been a Boeing it may well have stalled with disasterous consequences. Of course had it been a Boeing Sully may well have chosen not to pull full aft stick.
The key was his decision to start the APU which kept the aircraft in Normal Law. The aircraft looked after him and gave him the maximum performance it could while preventing a stall. Well done Sully and well done Airbus in my view.
So we can say Sully could have done better with his airspeed and that Airbus could have done better with their checklist but the end result was the best that could be hoped for. Sully looked after the jet and it looked after him.
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; however, the airplane did provide maximum performance for the weight and configuration at that time.
So the aircraft gave Sully the max performance that it could. A very different picture to the one presented if you only refer to the aircraft limiting AOA.
F speed for Config 2 was around 150kts and IAS was 125kts when he ditched (NTSB). So he was very close to the stall and was in fact in Alpha Protection from 150' rad alt. So far from the aircraft being at fault I would say that it perhaps saved them at this stage. Sully pulled full aft stick (in order to flare) close to the stall, had it been a Boeing it may well have stalled with disasterous consequences. Of course had it been a Boeing Sully may well have chosen not to pull full aft stick.
The key was his decision to start the APU which kept the aircraft in Normal Law. The aircraft looked after him and gave him the maximum performance it could while preventing a stall. Well done Sully and well done Airbus in my view.
So we can say Sully could have done better with his airspeed and that Airbus could have done better with their checklist but the end result was the best that could be hoped for. Sully looked after the jet and it looked after him.
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Originally Posted by Ashling
From the NTSB report pages 97/98
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; however, the airplane did provide maximum performance for the weight and configuration at that time.
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; however, the airplane did provide maximum performance for the weight and configuration at that time.
It did performed as designed, but that’s not necessarily the performance the pilot was after for working the flare.
So the aircraft gave Sully the max performance that it could.
What is a flare Ashling ?
So far from the aircraft being at fault I would say that it perhaps saved them at this stage. Sully pulled full aft stick (in order to flare) close to the stall, had it been a Boeing it may well have stalled with disastrous consequences.
Please, would you address it directly to Sully, I think he might put its politically correct discourse aside for the reply …
The key was his decision to start the APU which kept the aircraft in Normal Law. Beyond that the aircraft looked after him and gave him the maximum performance it could while preventing a stall.
Where published figures say otherwise … ?
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Sully, and his crew, did a great job on the day. No one, least of all me, wants to take away from that. However that does not mean they did everything perfectly and so it is perfectly reasonable to look at the report and draw lessons from it. That does not amount to a personal attack on Sully. It is the NTSB that draw our attention to the issue of speed control and the effect it had. They also qualify their comments by explaining the effects of task saturation etc.
You quoted my comments re Sully rather selectively. Here is what I said
"So far from the aircraft being at fault I would say that it perhaps saved them at this stage. Sully pulled full aft stick (in order to flare) close to the stall, had it been a Boeing it may well have stalled with disasterous consequences. Of course had it been a Boeing Sully may well have chosen not to pull full aft stick."
I said "perhaps saved them" which is very different to saying did save them. It is fact that Sully pulled full aft stick close to the stall. He was trying to cushion the impact perhaps in the knowledge that he could not stall the aircraft in Normal Law. I went on to say that had it been in a Boeing he might have flown it differently.
Sully's 2 key decisions, to start the APU and to Ditch allied to his leadership and the teamwork of his crew is why they all survived. No one can take that away. However there were issues. A few quotes from the NTSB report.
Despite not reaching this portion of the Engine Dual Failure checklist, the captain stated during postaccident interviews that he thought that he had obtained green dot speed immediately after the bird strike, maintained that speed until the airplane was configured for landing, and, after deploying the flaps, maintained a speed “safely above VLS,” which is the lowest selectable airspeed providing an appropriate margin to the stall speed. However, FDR data indicated that the airplane was below green dot speed and at VLS or slightly less for most of the descent, and about 15 to 19 knots below VLS during the last 200 feet.
The NTSB concludes that the captain’s difficulty maintaining his intended airspeed during the final approach resulted in high AOAs, which contributed to the difficulties in flaring the airplane, the high descent rate at touchdown, and the fuselage damage. (See additional discussion in section 2.7.1.)
The NTSB concludes the captain’s difficulty maintaining his intended airspeed during the final approach resulted, in part, from high workload, stress, and task saturation.
The airplane’s airspeed in the last 150 feet of the descent was low enough to activate the alpha-protection mode of the airplane’s fly-by-wire envelope protection features. The captain progressively pulled aft on the sidestick as the airplane descended below 100 feet, and he pulled the sidestick to its aft stop in the last 50 feet, indicating that he was attempting to raise the airplane nose to flare and soften the touchdown on the water. 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; however, the airplane did provide maximum performance for the weight and configuration at that time.The Airbus simulation indicated that the captain’s aft sidestick inputs in the last 50 feet of the flight were attenuated, limiting the ANU response of the airplane even though about 3.5° of margin existed between the airplane’s AOA at touchdown (between 13° and 14°) and the maximum AOA for this airplane weight and configuration (17.5°). Airbus’ training curricula does not contain information on the effects of alpha-protection mode features that might affect the airplane’s response to pilot sidestick pitch inputs. The flight envelope protections allowed the captain to pull full aft on the sidestick without the risk of stalling the airplane.
14. Despite being unable to complete the Engine Dual Failure checklist, the captain started the auxiliary power unit, which improved the outcome of the ditching by ensuring that a primary source of electrical power was available to the airplane and that the airplane remained in normal law and maintained the flight envelope protections, one of which protects against a stall.
16. The captain’s difficulty maintaining his intended airspeed during the final approach resulted in high angles-of-attack, which contributed to the difficulties in flaring the airplane, the high descent rate at touchdown, and the fuselage damage.
17. The captain’s difficulty maintaining his intended airspeed during the final approach resulted, in part, from high workload, stress, and task saturation.
So airspeed control was an issue.
Starting the APU played a key part in the successfull outcome
The aircraft Max Performed when asked to. Had it given him more alpha the performance wouldn't have changed and they would have been closer to the stall. Note that Airbus are only told to highlight this more in training. No where does it say that they need to change the control logic or that the aircraft failed to give maximum performance when asked. You should know that you can raise the nose more to no effect.
Had Sully been able to carry more speed into the flare, F speed or at least VLS he would have found the flare much easier in any control law.
Sorry for all the quotes but you did ask.
Sully, and his crew, did a great job on the day. No one, least of all me, wants to take away from that. However that does not mean they did everything perfectly and so it is perfectly reasonable to look at the report and draw lessons from it. That does not amount to a personal attack on Sully. It is the NTSB that draw our attention to the issue of speed control and the effect it had. They also qualify their comments by explaining the effects of task saturation etc.
You quoted my comments re Sully rather selectively. Here is what I said
"So far from the aircraft being at fault I would say that it perhaps saved them at this stage. Sully pulled full aft stick (in order to flare) close to the stall, had it been a Boeing it may well have stalled with disasterous consequences. Of course had it been a Boeing Sully may well have chosen not to pull full aft stick."
I said "perhaps saved them" which is very different to saying did save them. It is fact that Sully pulled full aft stick close to the stall. He was trying to cushion the impact perhaps in the knowledge that he could not stall the aircraft in Normal Law. I went on to say that had it been in a Boeing he might have flown it differently.
Sully's 2 key decisions, to start the APU and to Ditch allied to his leadership and the teamwork of his crew is why they all survived. No one can take that away. However there were issues. A few quotes from the NTSB report.
Despite not reaching this portion of the Engine Dual Failure checklist, the captain stated during postaccident interviews that he thought that he had obtained green dot speed immediately after the bird strike, maintained that speed until the airplane was configured for landing, and, after deploying the flaps, maintained a speed “safely above VLS,” which is the lowest selectable airspeed providing an appropriate margin to the stall speed. However, FDR data indicated that the airplane was below green dot speed and at VLS or slightly less for most of the descent, and about 15 to 19 knots below VLS during the last 200 feet.
The NTSB concludes that the captain’s difficulty maintaining his intended airspeed during the final approach resulted in high AOAs, which contributed to the difficulties in flaring the airplane, the high descent rate at touchdown, and the fuselage damage. (See additional discussion in section 2.7.1.)
The NTSB concludes the captain’s difficulty maintaining his intended airspeed during the final approach resulted, in part, from high workload, stress, and task saturation.
The airplane’s airspeed in the last 150 feet of the descent was low enough to activate the alpha-protection mode of the airplane’s fly-by-wire envelope protection features. The captain progressively pulled aft on the sidestick as the airplane descended below 100 feet, and he pulled the sidestick to its aft stop in the last 50 feet, indicating that he was attempting to raise the airplane nose to flare and soften the touchdown on the water. 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; however, the airplane did provide maximum performance for the weight and configuration at that time.The Airbus simulation indicated that the captain’s aft sidestick inputs in the last 50 feet of the flight were attenuated, limiting the ANU response of the airplane even though about 3.5° of margin existed between the airplane’s AOA at touchdown (between 13° and 14°) and the maximum AOA for this airplane weight and configuration (17.5°). Airbus’ training curricula does not contain information on the effects of alpha-protection mode features that might affect the airplane’s response to pilot sidestick pitch inputs. The flight envelope protections allowed the captain to pull full aft on the sidestick without the risk of stalling the airplane.
14. Despite being unable to complete the Engine Dual Failure checklist, the captain started the auxiliary power unit, which improved the outcome of the ditching by ensuring that a primary source of electrical power was available to the airplane and that the airplane remained in normal law and maintained the flight envelope protections, one of which protects against a stall.
16. The captain’s difficulty maintaining his intended airspeed during the final approach resulted in high angles-of-attack, which contributed to the difficulties in flaring the airplane, the high descent rate at touchdown, and the fuselage damage.
17. The captain’s difficulty maintaining his intended airspeed during the final approach resulted, in part, from high workload, stress, and task saturation.
So airspeed control was an issue.
Starting the APU played a key part in the successfull outcome
The aircraft Max Performed when asked to. Had it given him more alpha the performance wouldn't have changed and they would have been closer to the stall. Note that Airbus are only told to highlight this more in training. No where does it say that they need to change the control logic or that the aircraft failed to give maximum performance when asked. You should know that you can raise the nose more to no effect.
Had Sully been able to carry more speed into the flare, F speed or at least VLS he would have found the flare much easier in any control law.
Sorry for all the quotes but you did ask.
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The aircraft Max Performed when asked to. Had it given him more alpha the performance wouldn't have changed and they would have been closer to the stall. Note that Airbus are only told to highlight this more in training. No where does it say that they need to change the control logic or that the aircraft failed to give maximum performance when asked. You should know that you can raise the nose more to no effect.
It is not something you sustain in the time.
It is only a transitory phase very limited in the time.
The potential to improve the touchdown was in the aerodynamics.
The electronic prevented the pilot to get it.
Where published figures say otherwise ?
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I've in excess of 12,000 hrs, flown Mil Fast Jet, instructed, and flown civil Boeing and Airbus. I think I know what a flare is by now. Thank you very much.
The aircraft max performed, there was nothing more it could do aerodynamically. You need to appreciate that more backstick does not always mean less rate of descent or a gentler touchdown. In fact it may mean the opposite. The aircraft certainly knew this hence why it attentuated the inputs to give max performance.
We won't agree so I'll leave it there except to say that Sully, his crew and the Jet did a fine job that day.
I've in excess of 12,000 hrs, flown Mil Fast Jet, instructed, and flown civil Boeing and Airbus. I think I know what a flare is by now. Thank you very much.
The aircraft max performed, there was nothing more it could do aerodynamically. You need to appreciate that more backstick does not always mean less rate of descent or a gentler touchdown. In fact it may mean the opposite. The aircraft certainly knew this hence why it attentuated the inputs to give max performance.
We won't agree so I'll leave it there except to say that Sully, his crew and the Jet did a fine job that day.
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Having viewed the landing on the water many times, I can say that the AoA looked highly appropriate, and the "Rollout" proceeded quite well. Again, in viewing the Ditch, I couldn't see much to criticize.
Absent deployed landing gear, she flew somewhat "different", I would say, than in an ordinary TouchDown.
Nose High, what if the Tail Holed? Nose High, what if the Nose planted, instead of skipped? Fatalities, perhaps many. Perhaps all.
You know, data can be a fluffy pillow for those who weren't there, but make a living crunching others' work.
Flare? On a water Landing? Hmm......
Absent deployed landing gear, she flew somewhat "different", I would say, than in an ordinary TouchDown.
Nose High, what if the Tail Holed? Nose High, what if the Nose planted, instead of skipped? Fatalities, perhaps many. Perhaps all.
You know, data can be a fluffy pillow for those who weren't there, but make a living crunching others' work.
Flare? On a water Landing? Hmm......
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In 11 of the 12 runs, the touchdown flightpath angle ranged between -1.5° and -3.6° (the touchdown flightpath angle achieved on the accident flight was -3.4°). In 1 of these 12 runs, a -0.2° touchdown flightpath angle was achieved by an Airbus test pilot who used a technique that involved approaching the water at a high speed, leveling the airplane a few feet above the water with the help of the radar altimeter, and then bleeding off airspeed in ground effect until the airplane settled into the water.
Interesting technique and not one I would have thought of before reading it.
Interesting technique and not one I would have thought of before reading it.