Virgin ATR grounded in Albury
ATSB is clear:
“The limit load for the:
- vertical load on the horizontal stabiliser was exceeded
- vertical load on the wing was reached
- bending moment on the wing was exceeded
- engine mounts were exceeded.
The ultimate load, in terms of the asymmetric moment on the horizontal stabiliser, was exceeded.
ATR’s analysis found that the maximum load on the horizontal stabiliser coincided with the maximum elevator deflection that occurred 0.125 seconds after the elevators uncoupled. At that point, the ultimate load was exceeded by about 47 per cent, and the exceedance lasted about 0.125 second.”
I suspect that the aircraft survived because the load exceedance was so short. Also surplus static strength can arise from meeting fatigue durability requirements and from aeroelastic stiffness requirements. For whatever reason, the passengers were very lucky.
“The limit load for the:
- vertical load on the horizontal stabiliser was exceeded
- vertical load on the wing was reached
- bending moment on the wing was exceeded
- engine mounts were exceeded.
The ultimate load, in terms of the asymmetric moment on the horizontal stabiliser, was exceeded.
ATR’s analysis found that the maximum load on the horizontal stabiliser coincided with the maximum elevator deflection that occurred 0.125 seconds after the elevators uncoupled. At that point, the ultimate load was exceeded by about 47 per cent, and the exceedance lasted about 0.125 second.”
I suspect that the aircraft survived because the load exceedance was so short. Also surplus static strength can arise from meeting fatigue durability requirements and from aeroelastic stiffness requirements. For whatever reason, the passengers were very lucky.
I had downloaded the pdf before posting.
Components have multiple load cases they are designed to under the certification requirements. They are designed for the ground loads, vertical load factor, braking, bumps, turns, rejected takeoff, incomplete gear extension, ground winds, and break away. In flight they are designed for maneuver, gust, control deflection (normal and failure abnormal cases), buffet, inertia, vibration, aeroelastic/flutter loads. Additionally there are the other requirements such as jacking, pressurization, crash-worthiness, bird strike, lightning strike, hail, power plant failure, fire, fatigue, damage tolerance, fail safety, acoustics, and ground handling/towing.
Aircraft are designed so that the most limiting design case has 150% safety margin. Other non-limiting load cases at ultimate design load can have a additional margin of safety from a different load case which overlaps that component. For example the skin on the wing may need a ultimate load of X for bending moment, however requires 10 times X for crash worthiness. If the skin sees 2 times X bending moment load is is not going to fail as it still has significant margin for the crash worthiness requirement.
If we only had to look at 5 load cases when designing an aircraft we could do that in the afternoon, in reality it takes years because the task is a smidge more complicated.
Components have multiple load cases they are designed to under the certification requirements. They are designed for the ground loads, vertical load factor, braking, bumps, turns, rejected takeoff, incomplete gear extension, ground winds, and break away. In flight they are designed for maneuver, gust, control deflection (normal and failure abnormal cases), buffet, inertia, vibration, aeroelastic/flutter loads. Additionally there are the other requirements such as jacking, pressurization, crash-worthiness, bird strike, lightning strike, hail, power plant failure, fire, fatigue, damage tolerance, fail safety, acoustics, and ground handling/towing.
Aircraft are designed so that the most limiting design case has 150% safety margin. Other non-limiting load cases at ultimate design load can have a additional margin of safety from a different load case which overlaps that component. For example the skin on the wing may need a ultimate load of X for bending moment, however requires 10 times X for crash worthiness. If the skin sees 2 times X bending moment load is is not going to fail as it still has significant margin for the crash worthiness requirement.
If we only had to look at 5 load cases when designing an aircraft we could do that in the afternoon, in reality it takes years because the task is a smidge more complicated.
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those are not the facts.
the aircraft was flown in turbulence on descent at Vmo (maximum operating speed) the turbulence penetration speed is some 50 knots slower than Vmo.
the pilots did not realise that the aircraft was being structurally damaged by the descents.
aircraft continued in service until a bird strike caused a mechanic to have a look at what the damage was.
the inspection showed structural damage that had escaped the manufacturers inspection procedures, (built as they were on slower speed assumptions and lesser structural loads.)
there is obviously more to it than this potted history.
two of the manufacturer's test pilots flew that repaired aircraft back to Toulouse. presumably this will allow the designers to investigate what will be needed in the design to prevent a recurrence.
your mileage may vary.
have a safe flight.
W8
the aircraft was flown in turbulence on descent at Vmo (maximum operating speed) the turbulence penetration speed is some 50 knots slower than Vmo.
the pilots did not realise that the aircraft was being structurally damaged by the descents.
aircraft continued in service until a bird strike caused a mechanic to have a look at what the damage was.
the inspection showed structural damage that had escaped the manufacturers inspection procedures, (built as they were on slower speed assumptions and lesser structural loads.)
there is obviously more to it than this potted history.
two of the manufacturer's test pilots flew that repaired aircraft back to Toulouse. presumably this will allow the designers to investigate what will be needed in the design to prevent a recurrence.
your mileage may vary.
have a safe flight.
W8
That being said, it appears from the report that the captain applied a significant amount of pull force into the control column. I suspect that once the disconnect happened the application of force of both pilots was no longer meeting the resistance from each other allowing their input to have a sudden increased effect in terms of elevator deflection at a relatively high speed with the resulting structural effect.
It would be interesting to see what was actually written in the logbook(and verbalized to maintenance, if anything) to get an idea of what the maintenance person would be triggered to specifically look for. If it was just about the pitch disconnect which was quite possible that this was the area of concentration. There must have been several walkarounds done by pilots during the following flights that did not detect the visual structural damage although the distortion damage was probably much less noticeable from close up than from a distance while the cracking and wrinkling would not be visible from walkaround distance. An example of how giving an overall look at an aircraft from a distance as it is approached could catch a defect.
I looked up the pitch disconnect procedure from my old ATR notes from several years ago and see nothing about any advisory about possible damage from this sort of scenario. Over 3g was applied to the aircraft. I wonder if this could happen while attempting to disconnect from a jam. If so, something to consider when attempting to do this and how it will affect the people in the back although in a jammed flight control situation, aircraft control is obviously the priority.
Last edited by JammedStab; 12th Sep 2016 at 23:09.
Today, 5 May 2017, ATSB published a second interim report into the pitch disconnect and serious in-flight damage to an ATR 72 in February 2014.
It's at http://www.atsb.gov.au/media/5772731...rim-report.pdf
The horizontal stabilizer was overloaded well beyond design capability and visibly twisted. The weakened aircraft stayed in service for five days until the damage was found almost by chance.
At first read ATSB has done a thorough job and confronted ATR and EASA with design and certification issues as bluntly as it can.
However it should not take ATSB over three years just to reach a second interim report. And ATSB has yet to address local issues that put so many passengers at risk.
It's at http://www.atsb.gov.au/media/5772731...rim-report.pdf
The horizontal stabilizer was overloaded well beyond design capability and visibly twisted. The weakened aircraft stayed in service for five days until the damage was found almost by chance.
At first read ATSB has done a thorough job and confronted ATR and EASA with design and certification issues as bluntly as it can.
However it should not take ATSB over three years just to reach a second interim report. And ATSB has yet to address local issues that put so many passengers at risk.
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So if the the ATSB is saying that until they get further data from ATR they can not guarantee the aircraft meets certification, does Virgin have any other option then to ground the fleet?
Flight has a clear and forthright report at https://www.flightglobal.com/news/ar...ntrols-436908/
“The Australian Transport Safety Bureau (ATSB) has called on ATR to quickly complete an engineering assessment of the type's pitch control system, amid possible concerns that a serious design flaw may be present in the ATR 42 and 72 series.”
“The Australian Transport Safety Bureau (ATSB) has called on ATR to quickly complete an engineering assessment of the type's pitch control system, amid possible concerns that a serious design flaw may be present in the ATR 42 and 72 series.”
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See what happens when we let these low cost carriers from South East Asian countries (with their poor crew coordination and lax maintenance oversight) fly in our airspace!! CASA should ban them!
Oh, hang on...
Oh, hang on...
It’s shameful that ATSB took five years to investigate a potentially deadly structural failure of Virgin’s ATR 72. And all that’s been done to stop recurrence is tell pilots to be more careful!
By comparison Indonesia completed its investigation of AirAsia 8501 break-up within a year; including wreckage retrieval. Likewise we want Indonesia and Ethiopia to complete their investigations of 737 MAX accidents within a year.
By comparison Indonesia completed its investigation of AirAsia 8501 break-up within a year; including wreckage retrieval. Likewise we want Indonesia and Ethiopia to complete their investigations of 737 MAX accidents within a year.
Another serious one that I’ve been waiting for.
I wonder if they are consulting and communicating with the said operators during the investigation? Or waiting 3-5 years then at fault company implementing said ‘safety alerts’. In which time the same problem could have occurred again and again.
https://www.atsb.gov.au/publications...r/ao-2016-084/
I wonder if they are consulting and communicating with the said operators during the investigation? Or waiting 3-5 years then at fault company implementing said ‘safety alerts’. In which time the same problem could have occurred again and again.
https://www.atsb.gov.au/publications...r/ao-2016-084/
Hi das,
Whilst this incident (the mishandling, collapse of crew coordination in flight) in itself appears to be an "isolated time", the investigation revealed an endemic, systemic FAILURE of the entire maintenance system supporting the ATR fleet. In my opinion, absolutely appalling and the sort of behavior that many contributors to these Aussie forums (often rightfully) sling mud towards some of our northern neighbours, when they are found lacking in the same way.
Hence my (admittedly sarcastic) post...
Whilst this incident (the mishandling, collapse of crew coordination in flight) in itself appears to be an "isolated time", the investigation revealed an endemic, systemic FAILURE of the entire maintenance system supporting the ATR fleet. In my opinion, absolutely appalling and the sort of behavior that many contributors to these Aussie forums (often rightfully) sling mud towards some of our northern neighbours, when they are found lacking in the same way.
Hence my (admittedly sarcastic) post...
https://www.afr.com/business/transpo...20140114-iya4s
Yeah, must have been a singular event, CASA and the ATSB don't seem to agree and the Virgin Board as well...... anyone else I have left out?
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Engineering aspects post event aside and purely from the piloting standpoint, I was hopeful what I would consider the actual root cause for the event in flight would at least be listed as a contributing factor - but sadly no and so a huge learning point is lost for the industry.
The answer lies in the question - why would a pilot respond in that way to what would have a been a minor over speed event?
From the report it seems to me the 'distraction' element (still valid but to a far lesser extent) was a far easier and more politically safe factor, instead of scrutinising the bigger issue.
In any event, some other good lessons were learned and I'm very glad (the tragic CC injury notwithstanding) it didn't take more severe consequences as is often the case.
The answer lies in the question - why would a pilot respond in that way to what would have a been a minor over speed event?
From the report it seems to me the 'distraction' element (still valid but to a far lesser extent) was a far easier and more politically safe factor, instead of scrutinising the bigger issue.
In any event, some other good lessons were learned and I'm very glad (the tragic CC injury notwithstanding) it didn't take more severe consequences as is often the case.
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The answer lies in the question - why would a pilot respond in that way to what would have a been a minor over speed event?
One single reason.....punitive action! Every single pilot knows that a transgression in SOP's means " you are in trouble"This mentality is on every cockpit on every flight, we carry it around with us like a loaded gun!
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Yep pretty much. And did the ATSB read the letters MM mailed directly to every VARA pilot (prior to the pitch disconnect event) telling them they’d be punished if they kept being naughty. I’ve heard the culture was at an all time low with pilots scared to slip up. Could that have been the real reason for the overreaction in the flight deck that day?
One single reason.....punitive action!
As far as experience goes it looks like from the ATSB report the FO was a former overseas ATR Captain with thousands of hours of ATR experience who was relegated to the right seat. Whilst the Captain (who surprisingly joined the company after the FO) was a former Australian military pilot who seems to have gained a direct entry command with zero ATR or commercial flying experience. Given it seems the inadvertent control movement emanated from the Captain it seems that's where the experience gap was.
Last edited by dr dre; 31st May 2019 at 04:20.
