SWA1380 - diversion to KPHL after engine event
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The windmilling vibration loads are still tremendous - the FAA has made Boeing show that the rest of the aircraft can readily handle the blade out vibrations for an extended ETOPS diversion - it wasn't trivial.
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Given the lack of vibration depicted in video of the SW1380 incident, I'd say the engine wasn't windmilling at all. The first two videos below show what it's like inside an airplane with a windmilling but unbalanced engine.
As seen in previous catastrophic engine failure events, often the initial shaking caused by an unbalanced high speed rotating mass is so strong that the engine simply sheds its exterior components (see the third video), if it isn't ripped from the pylon altogether. Even when blades remain within the containment ring, and even if friction prevents the engine from windmilling, it certainly seems possible for a piece of the cowling to catch the airflow at just the right angle to lead it directly into the side of the plane and damage a window as the engine winds down.
AirAsia X D7237:
United 1175:
Exterior shot of United 1175:
Last edited by PineappleFrenzy; 21st Apr 2018 at 23:36.
tdracer
The FAA also included all other plane manufacturers as well in the assessment. Tis true some interesting windmill events did occur but they were all associated with the loss of the engine front shaft support and did not otherwise degrade other critical structures or the ability to fly the aircraft.. Nevertheless the loads developed were well within the design loads for manuever and gust loading in the aircraft certification base.
The worst part of it was that the passengers were not happy as the aircraft went through a critical windmill speed range while landing.
As for reading the flight deck instrumentation we confirmed that the crews could fly the aircraft with no problem. We got one famous chap to sit on a laboratory shake table and cranked it up to the expected frequency and amplitude for a time and he had no complaints and slept for days afterwards.
the FAA has made Boeing show that the rest of the aircraft can readily handle the blade out vibrations for an extended ETOPS diversion - it wasn't trivial.
One story was that after a blade out event on a 747, the aircraft vibrations were so severe the crew had difficulty reading the flight deck gauges (one variation of the story - perhaps antidotal - was that there was a Boeing exec on the flight - after the flight he promptly asked engineering to go make sure the aircraft could handle that level of vibration..)
One story was that after a blade out event on a 747, the aircraft vibrations were so severe the crew had difficulty reading the flight deck gauges (one variation of the story - perhaps antidotal - was that there was a Boeing exec on the flight - after the flight he promptly asked engineering to go make sure the aircraft could handle that level of vibration..)
The worst part of it was that the passengers were not happy as the aircraft went through a critical windmill speed range while landing.
As for reading the flight deck instrumentation we confirmed that the crews could fly the aircraft with no problem. We got one famous chap to sit on a laboratory shake table and cranked it up to the expected frequency and amplitude for a time and he had no complaints and slept for days afterwards.
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Insight on Acting Gov Managers...
The FAA has an "acting" -
Administrator
Deputy Administrator
Chief of Staff
Associate Administrator Airports
Assistant Administrator Finance and Management
Assistant Administrator Next Gen
And on and on. The previous manager for Engines and Propeller Standards died a couple years ago. Ms Grant has been in that office all this century. They probably don't want to make her position official as she'd go up a notch in pay.
Administrator
Deputy Administrator
Chief of Staff
Associate Administrator Airports
Assistant Administrator Finance and Management
Assistant Administrator Next Gen
And on and on. The previous manager for Engines and Propeller Standards died a couple years ago. Ms Grant has been in that office all this century. They probably don't want to make her position official as she'd go up a notch in pay.
Gov employee here (not FAA or NTSB, but another federal safety regulator). While 17+ years seems kind of long in my experience (has she really been an actor in that role for that length of time, or are you extrapolating her time in service with the FAA to that one position - people do move around a lot in Fed agencies), acting managers are a fact of life in government service. It takes time to post, interview, hire (most often from within) for a management position in a Fed agency. Also, there are generally time limits on how long one can act in a higher-graded position without receiving the higher-grade pay.
Most of us - even the managers - are competent professionals just trying to do our part to serve the public. This even applies to the political appointees (although I'll grant it 's become more of an exception in the last year or so
). I thought Chairman Sumwalt did a fine job in the media briefing posted earlier.Back to lurking. Thanks to the many professionals who make this site such an engaging read for this wanna-be aviator.
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PineappleFrenzy.
“Given the delay between the initial blade failure and the window failure, I think the evidence available supports the hypothesis that pieces of the cowl, or other secondary debris struck the window as the unbalanced engine wound down...”
Wound down sure. Absent a shaft brake or lock, what does windmilling do in such a circumstance?
“Given the delay between the initial blade failure and the window failure, I think the evidence available supports the hypothesis that pieces of the cowl, or other secondary debris struck the window as the unbalanced engine wound down...”
Wound down sure. Absent a shaft brake or lock, what does windmilling do in such a circumstance?
Unless they find the pieces (highly unlikely), I doubt if they will ever determine exactly what caused the damage.
It should be fairly straightforward to determine if the damage around the paint marks correlates with the window failing.
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FWIW my money is still on the fan cowl..
Given the lack of vibration depicted in video of the SW1380 incident, I'd say the engine wasn't windmilling at all. The first two videos below show what it's like inside an airplane with a windmilling but unbalanced engine.
AirAsia X D7237:
https://www.youtube.com/watch?v=_J5QsbA_QzQ
United 1175:
https://www.youtube.com/watch?v=f2TEJbm-HE4
AirAsia X D7237:
https://www.youtube.com/watch?v=_J5QsbA_QzQ
United 1175:
https://www.youtube.com/watch?v=f2TEJbm-HE4
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PineappleFrenzy
yes it's hard to believe
The blade loss video show large motions at the inlet, but motion alone is not enough. You have to couple it with mass and rate of change.
The even more challenging forces are gust loads in extreme turbulence or aircraft upsets and these don't end up like what you see in the pictures. As long as the inlet remains a box structure designed to aircraft principals it will hold up through all types of loadings.
yes it's hard to believe
The blade loss video show large motions at the inlet, but motion alone is not enough. You have to couple it with mass and rate of change.
The even more challenging forces are gust loads in extreme turbulence or aircraft upsets and these don't end up like what you see in the pictures. As long as the inlet remains a box structure designed to aircraft principals it will hold up through all types of loadings.
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In this news article http://www.bbc.com/news/world-us-canada-43804253
I saw this quote:
Does that sound right? Haven't seen it mentioned in this thread or anywhere else. If true it seems like quite a significant roll. What would cause that?
I saw this quote:
For a few seconds, the aircraft rolled to an angle of 41 degrees before levelling out and starting an emergency descent, federal investigators said on Wednesday.
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NTSB board member Robert Sumwalt said during one of the briefings that the bank angle reached 41.3 degrees (or was it 41.5?). He then proceeded to say that your first reaction would be to grab the yoke and correct it. Since he was an airline pilot for 24 years, I doubt he would have confused bank angle with yaw. Certainly one of the staffers may have given him misinformation, but it doesn't sound like it. (Edit: I misunderstood Chesty's terse answer. My apologies.)
Link to relevant portion of briefing
Then during the Q&A one of the reporters asked him about the roll and he elaborated:
Link to relevant portion of briefing
The aircraft began a rapid uncommanded left roll of about 41 degrees of bank angle. So usually when you're flying on an airliner you rarely get over about 20-25 degrees of bank. This went over to 41 degrees. The pilots leveled the wings.
Last edited by core_dump; 22nd Apr 2018 at 10:01.
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[QUOTE= Since he was an airline pilot for 24 years, I doubt he would have confused bank angle with yaw. But certainly one of the staffers may have given him misinformation.
I found that tidbit during the briefing very interesting as well.[/QUOTE]
following the question
"If true it seems like quite a significant roll. What would cause that? "
and answer "yaw"
What Chesty Morgan (of few words) probably meant was that engine failure causes asymmetric loss of thrust which causes yaw towards the failed engine, and the yaw coupled with wing sweepback causes significant ROLL
QED
I found that tidbit during the briefing very interesting as well.[/QUOTE]
following the question
"If true it seems like quite a significant roll. What would cause that? "
and answer "yaw"
What Chesty Morgan (of few words) probably meant was that engine failure causes asymmetric loss of thrust which causes yaw towards the failed engine, and the yaw coupled with wing sweepback causes significant ROLL
QED
How many of those result in rolling almost halfway to the vertical ?
While Chesty's succinct responses are always to be admired, in this case a few more words of explanation might have helped ...
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With those big fat dumpsters out on the wing, the drag, assuming the fan stopped fairly quickly, could be a tremendous yaw/roll.
On takeoff, your concern is complete control if such an event happens at low speed, as the ground is right there waiting, so hands and feet at literally on or near the controls on both sides. At altitude, the crew thought process is much more relaxed.
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He is probably the best chairman the NTSB has had. He was elevated to chairman by the present administration. Bob is a former airline pilot and ALPA safety rep. He also has an abundance of common sense and tact.
TNX for the education Chesty and others.
I was surprised at the amount of roll, but I guess with the motors at near-full thrust that the lack of thrust on one as well as increased drag from the damage was enuf. Also was prolly a fairly low "q" so aero authority of vertical stab likely low.
Yaw can cause significant roll even in straight wing planes depending on engine alignment with the aerodynamic longitudianl axis and not necessariy the physical. So you can get decent roll even on symmetrical thrust twins, and I flew one that required immediate full rudder and pulling the good engine back from mil thrust. Lost two folks on single engine go arounds because of that, especially if they were pullng back on the stick to get the nose up.
On the bent wing planes, the roll due to yaw can be extreme. Flying some fighters, we used nothing but rudder for roll when at high AoA, with stick locked between your knees. But 41+ degrees of roll within seconds at that stage of flight would sure get my attention, heh heh.
Gums sends...
I was surprised at the amount of roll, but I guess with the motors at near-full thrust that the lack of thrust on one as well as increased drag from the damage was enuf. Also was prolly a fairly low "q" so aero authority of vertical stab likely low.
Yaw can cause significant roll even in straight wing planes depending on engine alignment with the aerodynamic longitudianl axis and not necessariy the physical. So you can get decent roll even on symmetrical thrust twins, and I flew one that required immediate full rudder and pulling the good engine back from mil thrust. Lost two folks on single engine go arounds because of that, especially if they were pullng back on the stick to get the nose up.
On the bent wing planes, the roll due to yaw can be extreme. Flying some fighters, we used nothing but rudder for roll when at high AoA, with stick locked between your knees. But 41+ degrees of roll within seconds at that stage of flight would sure get my attention, heh heh.
Gums sends...
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Dangerous, but I'm going to make some assumptions. Engine failure, yaw, roll, autopilot tries to keep wings level with ailerons and control column goes to full scale PDQ. No doubt there was quite a bang. Autopilot lets go and a/c rolls. That would happen in only a few seconds. The startle factor must have been severe.
I wonder who was PF, but if I was captain I think I would have my hands and feet doing their thing. That in itself would be interesting if F/O (as PF) was also doing his thing. Knowing who had control would be essential, quickly.
One engine out FL325 means immediate descent, perhaps at idle to help control the yaw/roll. That needs ATC coordination/communication. A drift down in the scenario was highly unlikely.
Somewhere during the analysis of the engine bang they were then presented with the cabin ALT warning, then emergency descent.
This is worse than a bad hair day, and indeed at Gums says, idle thrust on the live makes life easier. They did have lots of height.
I'll be curious when/if they re-engaged the autopilot to reduce work load. The idle thrust on live + drag on sev damage engine would still give some yaw/roll problems, but rudder trim should have been enough to help the autopilot.
This really would have been a scenario of ANC & priorities.
I was curious, in the NTSB briefing, how he mentioned, and repeated the landing speeds for F30/40 landing; explaining their F5 landing was 30kts faster than normal. Difference between F5 & F15 is 10kts.
Good to hear the CVR/FDR and crew debriefing is underway expeditiously.
I wonder who was PF, but if I was captain I think I would have my hands and feet doing their thing. That in itself would be interesting if F/O (as PF) was also doing his thing. Knowing who had control would be essential, quickly.
One engine out FL325 means immediate descent, perhaps at idle to help control the yaw/roll. That needs ATC coordination/communication. A drift down in the scenario was highly unlikely.
Somewhere during the analysis of the engine bang they were then presented with the cabin ALT warning, then emergency descent.
This is worse than a bad hair day, and indeed at Gums says, idle thrust on the live makes life easier. They did have lots of height.
I'll be curious when/if they re-engaged the autopilot to reduce work load. The idle thrust on live + drag on sev damage engine would still give some yaw/roll problems, but rudder trim should have been enough to help the autopilot.
This really would have been a scenario of ANC & priorities.
I was curious, in the NTSB briefing, how he mentioned, and repeated the landing speeds for F30/40 landing; explaining their F5 landing was 30kts faster than normal. Difference between F5 & F15 is 10kts.
Good to hear the CVR/FDR and crew debriefing is underway expeditiously.
Dangerous, but I'm going to make some assumptions. Engine failure, yaw, roll, autopilot tries to keep wings level with ailerons and control column goes to full scale PDQ. No doubt there was quite a bang. Autopilot lets go and a/c rolls. That would happen in only a few seconds. The startle factor must have been severe.