TransAsia in the water?
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Correct me if I'm wrong, but don't high aspect ratio aerofoils normally exhibit benign drag curves, resulting in a low Vimd and making it difficult to get on the wrong side of the curve? I've tried to find an example of the ATR72 drag curve, but can't.
If the above is correct, the speeds shown on the trace, plus a margin for headwinds, shouldn't have put the a/c on the wrong side of the curve. Even after levelling off, there wasn't enough power available to maintain speed, and eventually height.
Any ATR72 drivers want to comment on what the Vimd might be?
Whatever the root cause, if my first para is correct, it seems like there was more going on here than a single engine failure....
If the above is correct, the speeds shown on the trace, plus a margin for headwinds, shouldn't have put the a/c on the wrong side of the curve. Even after levelling off, there wasn't enough power available to maintain speed, and eventually height.
Any ATR72 drivers want to comment on what the Vimd might be?
Whatever the root cause, if my first para is correct, it seems like there was more going on here than a single engine failure....
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I fly a similar profile wing and it gets draggy as hell below 160knts. Sweet spot is about 180-190 depending on weight.
S & L clean you will use the same power at 130 knts as you do at 165knts. 120 its the same as 190knts.
S & L clean you will use the same power at 130 knts as you do at 165knts. 120 its the same as 190knts.
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Mad Jock, even if the same applies to the ATR, it still appears that they didn't have the power to maintain speed, even after levelling at only 1350-ish ft - Given that they ought to have been able to control an eng fail right back at V1, and safely climb away, this suggests that at this point they had somewhat less than 1 engine's worth of power available...?
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Autofeather at lift off under t/o power would be quite an event. Mind blowing confusion with Nh, TGT, FF all in t/o range. Hydraulics unlikely to have caused or contributed, it is the contradictory indications of a sudden and unexpected autofeathering that are a handful.
A good example is the accident report for Lockheed L188C G-FIZU, AAIB bULLETIN 5/2008.
For those interested:
http://www.aaib.gov.uk/cms_resources...ZU%2005-08.pdf
A good example is the accident report for Lockheed L188C G-FIZU, AAIB bULLETIN 5/2008.
For those interested:
http://www.aaib.gov.uk/cms_resources...ZU%2005-08.pdf
Last edited by Chronus; 5th Feb 2015 at 19:39.
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I'm sure I'm not the only one who has viewed the video clip numerous times. One of the things I have noticed is that the ailerons are not deflected ,if your aircraft banks suddenly to port wouldn't it be natural to throw the wheel to starboard to counter it - try and lift the port wing? So far as I can see the ailerons are flush with the wings - I'd expect to see some serious ailerons movement - there is non. PE
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It all comes down to the prop on the failed being secured.
On one engine with the prop secured your down to 40-45% effective power performance.
If your zero thrust torque is 15-20% on an engine to simulate feathered and the engine isn't feather that then brings you down to 20-25%% effective power. Which just isn't enough to keep you S & L and speed stable.
Its why we have NTS and auto feather in TP's if you don't get rid of the drag of the failed prop you have the flights dynamics of a brick.
There are a few types which are not in that situation which is the SAAB 2K and Q400, from mates that fly them they are that well endowed in the engine dept even at a full load they have to be careful of overspeeding on single engine.
The SAAB 2K on a single engine a FL250 will quite happily overspeed.
Some of us have to deal with drift down alts in the region of 5-6k ft single engine and a full load.
On one engine with the prop secured your down to 40-45% effective power performance.
If your zero thrust torque is 15-20% on an engine to simulate feathered and the engine isn't feather that then brings you down to 20-25%% effective power. Which just isn't enough to keep you S & L and speed stable.
Its why we have NTS and auto feather in TP's if you don't get rid of the drag of the failed prop you have the flights dynamics of a brick.
There are a few types which are not in that situation which is the SAAB 2K and Q400, from mates that fly them they are that well endowed in the engine dept even at a full load they have to be careful of overspeeding on single engine.
The SAAB 2K on a single engine a FL250 will quite happily overspeed.
Some of us have to deal with drift down alts in the region of 5-6k ft single engine and a full load.
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itsmepaul57
Hi, I have looked at the video and about 2 seconds prior to hitting the bridge I do notice that the right aileron is up, trying to level the plane. It is hard to see and you have to go frame by frame.
Hi, I have looked at the video and about 2 seconds prior to hitting the bridge I do notice that the right aileron is up, trying to level the plane. It is hard to see and you have to go frame by frame.
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Jock Indeed
If the ambient temps are high and your good engine is cooking itself your drift down alt maybe be sea level or below, certainly if the dead prop doesn't feather.. Keep it flying.
The above illustrates why a TP is more demanding than a turbo fan to fly.
If the ambient temps are high and your good engine is cooking itself your drift down alt maybe be sea level or below, certainly if the dead prop doesn't feather.. Keep it flying.
The above illustrates why a TP is more demanding than a turbo fan to fly.
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I looked at the temps on the day and they were within 5 deg of ISA.
Vmca increases with temperature decreasing. It also increases when you put the gear up.
The book Vmca's are only valid in the TO configuration. After you get the gear up V2 is meant to keep you safe and then Vyse once clean. But if you stray away from the book configurations and limitations ie use more than 5 deg of bank engine not feathered you don't have a clue what the Vmca is.
Which is another issue I have with some of these noise abatement procedures requiring sometimes a 90 deg + turn left or right before the acceleration phase.
25-30 deg bank angle at 1000ft and the inside engine goes and your a smoking hole in the ground even with the auto feather or NTS working at V2 +10
Vmca increases with temperature decreasing. It also increases when you put the gear up.
The book Vmca's are only valid in the TO configuration. After you get the gear up V2 is meant to keep you safe and then Vyse once clean. But if you stray away from the book configurations and limitations ie use more than 5 deg of bank engine not feathered you don't have a clue what the Vmca is.
Which is another issue I have with some of these noise abatement procedures requiring sometimes a 90 deg + turn left or right before the acceleration phase.
25-30 deg bank angle at 1000ft and the inside engine goes and your a smoking hole in the ground even with the auto feather or NTS working at V2 +10
According Taiwan CAA an instructor/examiner with 16,121 hours total occupied the observer's seat.
Last edited by JanetFlight; 6th Feb 2015 at 07:37.
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Quote:
A grounding of Taiwan's 22 ATR aircraft
A grounding of Taiwan's 22 ATR aircraft
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Cheers for the info MJ. I'm a TP man, but only have extensive experience handling 4's (Hercs) - we would regularly practice 2 engine overshoots in the ac and MOS EFATOS in the sim (climbout below Vmca1) so I'm generally aware of how tricky it can get... and how quickly. Still though, something doesn't add up with those speed / alt plots.
Forgive the ignorance of more modern types... but when you say 'secured', do you mean feathered AND braked, or just feathered? From the vids & subsequent recovery pics, the left prop seems feathered, but still turning.
I think we may be missing a vital piece of info somewhere?
Forgive the ignorance of more modern types... but when you say 'secured', do you mean feathered AND braked, or just feathered? From the vids & subsequent recovery pics, the left prop seems feathered, but still turning.
I think we may be missing a vital piece of info somewhere?
I hope it's not an issue in this case, but sometimes the presence of checking authorities in a real emergency can be a serious inhibition, particularly where sticking to the book in fine detail is unwarranted by lack of time or other confounding factors. Often there is an awareness of the checker's idiosyncrasies by reputation that modifies one's instinctive response.
On the other hand, if time is not of the essence, they can be a valuable additional resource. It just depends on the particular circumstances.
On the other hand, if time is not of the essence, they can be a valuable additional resource. It just depends on the particular circumstances.
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Difficult to get that wrong on a TP twin though... the failed side becomes self-evident very quickly indeed at low speeds - 'dead leg, dead engine' is how I was taught. Unless yaw dampers / autotrim muddle the issue?
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To me as a twin TP pilot of a barely enough powered auld heap.
Apart from the speeds which some are interpreting as airspeeds which I believe are ground speeds it seems to be not to bad.
The crux is the engine securing. I have done a feather failure only a couple of times in 10 years and never on departure below 1k in the sim. Its not required as part of the LPC.
From doing OPC's in the aircraft and the TRE not setting zero simulated thrust after you have identified the engine with everything spot on 5 deg of bank, bang on Vyse she will descend with quarter tanks and just two of you onboard and 200kg of ballast in the boot and you will be at the control limits of both rudder and aileron. This I might add is the same in both TP types that I fly.
Put the "dead" engine up to 10% simulated and she will climb at 1000ft per min and regain both rudder and aileron to about 50% max travel.
With a full load of freight on we get 500ft/min climb rate in that config (don't ask we had a TRE that used to do that sort of thing when there was no pax on, to be honest looking back it was superb training if not a bit dodgy. I was doing single engine work with him every empty or freight flight sometimes 3-4 times a month for nearly 2 years)
If they had pulled the wrong engine it would have dropped out the sky pretty much vertically.
Secured as I use it just means the appropriate shutdown checklist has been completed or if not at least the memory items completed. I believe only one engine on the ATR's has a brake for hotel mode but I doubt its used in the event of a shut down. Windmilling on those dagger type props I think has a limit of 5% rpm if it gets above 10% it causes problems with fire drills as your meant to wait until the rpm is below 10% before firing the fire bottle. I am not a ATR driver so any that are can say if I am talking mince or not. They can adjust the windmilling speed but its extremely rare that its ever checked the faster it windmills the more drag you get.
Apart from the speeds which some are interpreting as airspeeds which I believe are ground speeds it seems to be not to bad.
The crux is the engine securing. I have done a feather failure only a couple of times in 10 years and never on departure below 1k in the sim. Its not required as part of the LPC.
From doing OPC's in the aircraft and the TRE not setting zero simulated thrust after you have identified the engine with everything spot on 5 deg of bank, bang on Vyse she will descend with quarter tanks and just two of you onboard and 200kg of ballast in the boot and you will be at the control limits of both rudder and aileron. This I might add is the same in both TP types that I fly.
Put the "dead" engine up to 10% simulated and she will climb at 1000ft per min and regain both rudder and aileron to about 50% max travel.
With a full load of freight on we get 500ft/min climb rate in that config (don't ask we had a TRE that used to do that sort of thing when there was no pax on, to be honest looking back it was superb training if not a bit dodgy. I was doing single engine work with him every empty or freight flight sometimes 3-4 times a month for nearly 2 years)
If they had pulled the wrong engine it would have dropped out the sky pretty much vertically.
Secured as I use it just means the appropriate shutdown checklist has been completed or if not at least the memory items completed. I believe only one engine on the ATR's has a brake for hotel mode but I doubt its used in the event of a shut down. Windmilling on those dagger type props I think has a limit of 5% rpm if it gets above 10% it causes problems with fire drills as your meant to wait until the rpm is below 10% before firing the fire bottle. I am not a ATR driver so any that are can say if I am talking mince or not. They can adjust the windmilling speed but its extremely rare that its ever checked the faster it windmills the more drag you get.
Last edited by mad_jock; 5th Feb 2015 at 21:39.
