A321 tailstrikes - Airbus/AAIB analysis
Guest
Posts: n/a
A321 tailstrikes - Airbus/AAIB analysis
This from Air Transport Intelligence, their copyright:
Airbus to update tailstrike guidance after A321 incidents
Kieran Daly, London (16May01, 16:41 GMT, 917 words)
Airbus Industrie is to issue renewed guidance to pilots on avoiding tailstrikes after seeing the rate of incidents on its
narrowbody family increase markedly following the introduction into service of the longer A321.
It stresses that the rate of such incidents on the type remains acceptable but is anyway to revise its earlier bulletin on the
subject in an effort to highlight the lessons of recent years.
Following two incidents at London Heathrow Airport last year, the UK Air Accidents Investigation Branch (AAIB) reports that
there have now been 12 A321 tailstrikes – making the rate three times that on the A320.
At 44.51m (146ft) the A321 is 6.94m (23ft) longer than the A320 and the AAIB says that, with the main landing gear oleos compressed, aft fuselage contact occurs on the A321 at a pitch attitude of 9.7° compared to 11.7° on the A320.
Conforming that the A321 has had “12 or 13” tailstrikes, Airbus director of flight safety in charge of in-service and incident
investigation Jean Daney says: “We have to be careful with this figure - what is important is the rate. This number is 12 per million departures which is well inside the normal. For example the [Boeing] 757 has a rate of higher than 50 per million and the [Boeing] MD-11 is also close to 50. It is not alarming but it is higher than the A320 mainly because the aircraft is longer.”
Airbus’ analysis has thrown up certain significant factors in the incidents, he says, explaining: “In the majority of cases we have had the common factor that the aircraft went above the glidepath at low altitude and the sidestick was pushed
forward leading to a high rate of descent and a very positive flare leading to a tailstrike.”
In the most recent incident a Lufthansa A321 (D-AIRE) suffered a tailstrike on London Heathrow’s runway 27L while landing in gusty crosswinds and rain on the afternoon of 9 October 2000.
The AAIB report describes how the aircraft descended below the glidepath at about 500ft (150m) then flew back through it, reached a rate of descent of 1,100ft/min (5.6m/s) as the pilot tried to recover the situation, and finally touched down hard before bouncing and incurring a tailstrike on the second touchdown. The aircraft suffered only “severe abrasion” to its skin.
In a second report just released, the AAIB details a 21 June 2000 incident also at Heathrow, but on 27R, in which an Aer Lingus A321 (EI-CPE) underwent a similar sequence of events.
In that case windshear of +/-10kt (+/-18km/hr) was reported and the final seconds of the approach were marked by the
aircraft moving above the glidepath at around 200ft followed by a descent of up to 900fpm leading to a bounce with a tailstrike on the second touchdown. The damage in that instance was somewhat worse and included minor penetrations of the skin.
The aircraft in both cases were being flown by the first officer; the Aer Lingus pilot had only 274hr flying experience with 82hr on type, and the Lufthansa pilot had 1,236hr on the Airbus narrowbody family.
Also in both cases the commanders made last-second control inputs - in the Aer Lingus incident after the bounce - but did
not press the takeover button that overrides the other sidestick controller.
Daney says Airbus first issued a bulletin addressing tailstrikes in 1992 and revised that in the light of experience in April
1999. Then in flight safety conferences last year it discussed the issue with operators and the International Federation of Air Line Pilots Associations (IFALPA) once more.
In January this year, he says, Airbus discussed the question again with the AAIB in the light of the A321 service history. “We are very close to issuing a new document. It is of course repeating and emphasising what we have said before but there are also new points. In 1992 it addressed the main causes that we had at that time but now we have new results,” he says.
In its latest reports the AAIB looks at the question of whether Airbus’ use of sidestick controllers and fly-by-wire played a role, noting that that the system allows both pilots to make control inputs, that the first officer’s control inputs are not directly
visible to the captain, and that the captain is required to press the ‘takeover’ button if he wants to override the first officer.
Its comments are inconclusive, noting that in neither of the Heathrow incidents did the captain use the takeover button or say ‘I have control’, but also that in both cases the approach instability developed at very low altitude leaving little or no time for
the captain to intervene usefully.
Daney argues that Airbus’ design remains the best solution: he explains that even on a “classical yoke” the pilots can effectively apply dual input – although in a somewhat different sense – because the controls are mechanically linked, and that Airbus pilots receive visual and aural warnings when both sidesticks are operated simultaneously. He concedes, however, that each pilot’s actions may be less obvious to the other than on a non-fly-by-wire design.
But Daney suggests that there is another crucial advantage to the sidestick design – and that is the ability to record digitally
the control inputs for analysis as part of airline flight operations quality assurance (FOQA) programmes using quick access recorders (QAR) or digital flight data recorders (DFDR) when appropriate. On conventional yokes only the yoke position can
be recorded, giving restricted insight into the pilots’ intentions.
Source: Air Transport Intelligence news
Airbus to update tailstrike guidance after A321 incidents
Kieran Daly, London (16May01, 16:41 GMT, 917 words)
Airbus Industrie is to issue renewed guidance to pilots on avoiding tailstrikes after seeing the rate of incidents on its
narrowbody family increase markedly following the introduction into service of the longer A321.
It stresses that the rate of such incidents on the type remains acceptable but is anyway to revise its earlier bulletin on the
subject in an effort to highlight the lessons of recent years.
Following two incidents at London Heathrow Airport last year, the UK Air Accidents Investigation Branch (AAIB) reports that
there have now been 12 A321 tailstrikes – making the rate three times that on the A320.
At 44.51m (146ft) the A321 is 6.94m (23ft) longer than the A320 and the AAIB says that, with the main landing gear oleos compressed, aft fuselage contact occurs on the A321 at a pitch attitude of 9.7° compared to 11.7° on the A320.
Conforming that the A321 has had “12 or 13” tailstrikes, Airbus director of flight safety in charge of in-service and incident
investigation Jean Daney says: “We have to be careful with this figure - what is important is the rate. This number is 12 per million departures which is well inside the normal. For example the [Boeing] 757 has a rate of higher than 50 per million and the [Boeing] MD-11 is also close to 50. It is not alarming but it is higher than the A320 mainly because the aircraft is longer.”
Airbus’ analysis has thrown up certain significant factors in the incidents, he says, explaining: “In the majority of cases we have had the common factor that the aircraft went above the glidepath at low altitude and the sidestick was pushed
forward leading to a high rate of descent and a very positive flare leading to a tailstrike.”
In the most recent incident a Lufthansa A321 (D-AIRE) suffered a tailstrike on London Heathrow’s runway 27L while landing in gusty crosswinds and rain on the afternoon of 9 October 2000.
The AAIB report describes how the aircraft descended below the glidepath at about 500ft (150m) then flew back through it, reached a rate of descent of 1,100ft/min (5.6m/s) as the pilot tried to recover the situation, and finally touched down hard before bouncing and incurring a tailstrike on the second touchdown. The aircraft suffered only “severe abrasion” to its skin.
In a second report just released, the AAIB details a 21 June 2000 incident also at Heathrow, but on 27R, in which an Aer Lingus A321 (EI-CPE) underwent a similar sequence of events.
In that case windshear of +/-10kt (+/-18km/hr) was reported and the final seconds of the approach were marked by the
aircraft moving above the glidepath at around 200ft followed by a descent of up to 900fpm leading to a bounce with a tailstrike on the second touchdown. The damage in that instance was somewhat worse and included minor penetrations of the skin.
The aircraft in both cases were being flown by the first officer; the Aer Lingus pilot had only 274hr flying experience with 82hr on type, and the Lufthansa pilot had 1,236hr on the Airbus narrowbody family.
Also in both cases the commanders made last-second control inputs - in the Aer Lingus incident after the bounce - but did
not press the takeover button that overrides the other sidestick controller.
Daney says Airbus first issued a bulletin addressing tailstrikes in 1992 and revised that in the light of experience in April
1999. Then in flight safety conferences last year it discussed the issue with operators and the International Federation of Air Line Pilots Associations (IFALPA) once more.
In January this year, he says, Airbus discussed the question again with the AAIB in the light of the A321 service history. “We are very close to issuing a new document. It is of course repeating and emphasising what we have said before but there are also new points. In 1992 it addressed the main causes that we had at that time but now we have new results,” he says.
In its latest reports the AAIB looks at the question of whether Airbus’ use of sidestick controllers and fly-by-wire played a role, noting that that the system allows both pilots to make control inputs, that the first officer’s control inputs are not directly
visible to the captain, and that the captain is required to press the ‘takeover’ button if he wants to override the first officer.
Its comments are inconclusive, noting that in neither of the Heathrow incidents did the captain use the takeover button or say ‘I have control’, but also that in both cases the approach instability developed at very low altitude leaving little or no time for
the captain to intervene usefully.
Daney argues that Airbus’ design remains the best solution: he explains that even on a “classical yoke” the pilots can effectively apply dual input – although in a somewhat different sense – because the controls are mechanically linked, and that Airbus pilots receive visual and aural warnings when both sidesticks are operated simultaneously. He concedes, however, that each pilot’s actions may be less obvious to the other than on a non-fly-by-wire design.
But Daney suggests that there is another crucial advantage to the sidestick design – and that is the ability to record digitally
the control inputs for analysis as part of airline flight operations quality assurance (FOQA) programmes using quick access recorders (QAR) or digital flight data recorders (DFDR) when appropriate. On conventional yokes only the yoke position can
be recorded, giving restricted insight into the pilots’ intentions.
Source: Air Transport Intelligence news
Guest
Posts: n/a
Interesting article...
Goes to show:
1. Aircraft need airframe strike protection (tail as well as wingtips or engine nacelles). It might be a good idea for Airbus to integrate an attitude limiter below a certain radalt -say 30 feet e.g.- into their control laws. But I can imagine that would be hard to certificate since you need to protect it well against radalt faults (wouldn't want the attitude to be blocked to say 10 deg pitch/5 deg bank during a GPSW/TCAS avoidance manoever.)
But there could at least be a warning when you're reaching the limits.
2. Basic flying skills are still of major importance, FBW aircraft or not. Seems the strikes on the 321's where the result of an approach gone wrong. Why didn't they go around? Having said that we're all only human beings so there are those who have and those who will... But nevertheless more attention should be paid to basic flying in all levels of training.
Goes to show:
1. Aircraft need airframe strike protection (tail as well as wingtips or engine nacelles). It might be a good idea for Airbus to integrate an attitude limiter below a certain radalt -say 30 feet e.g.- into their control laws. But I can imagine that would be hard to certificate since you need to protect it well against radalt faults (wouldn't want the attitude to be blocked to say 10 deg pitch/5 deg bank during a GPSW/TCAS avoidance manoever.)
But there could at least be a warning when you're reaching the limits.
2. Basic flying skills are still of major importance, FBW aircraft or not. Seems the strikes on the 321's where the result of an approach gone wrong. Why didn't they go around? Having said that we're all only human beings so there are those who have and those who will... But nevertheless more attention should be paid to basic flying in all levels of training.
