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Fukushima Prefecture AW139 crash land, no immediatefatalities

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Fukushima Prefecture AW139 crash land, no immediatefatalities

Old 7th Feb 2020, 09:33
  #41 (permalink)  
 
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I heard ( remember this is a RUMOUR network) - unconfirmed.... that the pilots were putting it down to turbulence, and there was no mechanical issue with the helo. Read in to that what you like.
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Old 8th Feb 2020, 20:38
  #42 (permalink)  
 
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eh, you Jimmy: "How almost zero airspeed "flare" could increase NR?" You can actually flare from a dive to horizontal, it works.

Crab ..... wrt "he has lowered the lever to reduce tq reaction and lowered the nose to gain speed."
please see my previous post:
"to gain airspeed in a rotating helicopter ideally the cyclic needs to move in the cockpit at (negatively) the same rotational rate, ie constant bearing."
If you just hold it forward in the helicopter cockpit it doesn't give the helicopter horizontal airspeed, just makes 'a funnel', just like Lake Vyrnwy, and this one.

A lowered lever and a constant bearing cyclic position, from that height would get most helicopters to arrest yaw.
Not without a change of trousers though. Still well done for surviving, that's what counts, too many airmchair 'experts'.
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Old 9th Feb 2020, 00:21
  #43 (permalink)  
 
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Originally Posted by AnFI View Post
eh, you Jimmy: "How almost zero airspeed "flare" could increase NR?" You can actually flare from a dive to horizontal, it works.
But in a dive I presume a pitch down that results in some airspeed, right? Descending at very low airspeed and low pitch down, doesn't make sense to me some aft cyclic increase NR or even arrest the rate of descent. If I'm missing something, please let me know.
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Old 9th Feb 2020, 10:02
  #44 (permalink)  
 
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AnFI - you do come up with some odd things sometimes - if the aircraft was descending vertically and spinning about the rotor axis, your theory (have you practised that technique) might be valid - BUT, in both the 139 video and the Welsh Lake (Not Vyrnwy but LLyn Peris) the aircraft had forward speed so pushing forward on the cyclic would assist.

I know you are an expert on all things aviation (you keep telling me so) but I knew the pilot in the Wessex and visited the crew in hospital the next day so I have a pretty good idea about what did and didn't work in that case.

Do you do much currency training in a twin simulator? Plenty of us here do and have done countless TR drive failures from different speeds and heights - moving the cyclic in a circular fashion to match the rate of rotation is not a recognised or even slightly valid technique.

Last edited by [email protected]; 9th Feb 2020 at 11:42.
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Old 9th Feb 2020, 10:42
  #45 (permalink)  
 
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"to gain airspeed in a rotating helicopter ideally the cyclic needs to move in the cockpit at (negatively) the same rotational rate, ie constant bearing
Not how it worked in the sim, just shove the stick forward accepting whatever rotation until airspeed obtained with the relevant sideslip, then fly to a suitable landing spot. Mind you, sims are not necessarily representative of the real thing, but that's what was being taught by a world preeminent sim training organisation.
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Old 9th Feb 2020, 10:45
  #46 (permalink)  
 
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Originally Posted by [email protected] View Post
...Plenty of us here do and have done countless TR drive failures from different speeds and heights - moving the cyclic in a circular fashion to match the rate of rotation is not a recognised or even slightly valid technique.
That's right.
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Old 9th Feb 2020, 14:23
  #47 (permalink)  
 
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"match the rate of rotation is not a recognised or even slightly valid technique."
Originally Posted by gulliBell View Post
That's right.
souldn't mix recognised and valid here. maybe not recognised but obviously valid.

if, by yaw, one keeps the horizontal component of thrust vector directed towards the center of a turn then the acceleration is towards the center of the turn.
no overall horizontal speed increase will occur. The bearing of the main rotor thrust needs to not be allowed to change (too much) with yaw if horizontal airspeed is desired, otherwise the new direction of mr thrust will negate some/most/all the speed increase.

seperately: the increased power consumption comes either from the engine (a move sometimes referred to as a 'sexy mushroom', if height is maintained) or in this case a higher rate of descent than would otherwise by the case. the measurement of speed in a steep nose down attitude is slightly confused by the rate of descent counting as speed wrt the longditudinal axis of the disc plane. that is why a flare is (effectively) possible at the bottom of a steep (funnel like) dive with very little horizontal speed.

i hope that answers the points about recognised methods, physics and flare from dive.


i am intruiged by Scorpygixxer skadi and Non-PC Plod posts, they do point to some other kind of confusion in this case. I suspect they are right.
Do we think this was a straight forward TR loss of thrust? Does seem strange as these 3 point out.
ShyTorque do you think this kind of helicopter has so little 'weather cocking' that it would go to 90 degrees from the cruise? Difficult to believe.
Hands off on autopilot i can see the pilots might get a bit behind events, especially if accustomed to YStab system dealing with normal yaw variations, but surely a pretty modest reduction in lever and a stick displaced to the right would preserve out of balance controlled flight.
Maybe they retarded the engines (classic mistake) as Scorpygixxer implies? (I cant really make out the coning angle on my screen, anyone?)

Can't wait to see the report (bets on 2 years plus?), maybe they just did what their sim instructor showed them after he'd talked to a pilot that once did the same mistake method?

["(Not Vyrnwy but LLyn Peris)" Not LLyn Peris either but Llyn Padarn according to the MOD report. Appendix A, Page 28, of this CAPAP2003_01.PDF is worth a read eg this: "
  • Shortly after the aircraft appeared to achieve stabilised flight, the nose began to rise and the aircraft decelerated. The aircraft was now close to its critical yaw angle, beyond which airflow separation over the rear fuselage/tail pylon occurs, thereby removing its yaw stabilising, ‘weather-cock’ effect. This angle appears to have been reached after 13 seconds of stable flight, when the yaw began to increase significantly.
" and "that there was a lack of adequate training for such an emergency" (in the RAF? surely not?)]
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Old 9th Feb 2020, 14:36
  #48 (permalink)  
 
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I am so glad to learn something new....after being involved in the helicopter business since 1967.....and always being a proponent of being able to learn from anyone and everyone no matter their experience level or background....I have to admit AnFi has come up with a new one on me.

Not a single book, article, training course, first hand experience or bar story ever surfaced anything remotely akin to what AnFi is telling us.

I can be convinced of new and innovative techniques.....but it does require some proving.

AnFi ain't there yet.

Care to lay it all out for us?
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Old 9th Feb 2020, 14:59
  #49 (permalink)  
 
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Originally Posted by SASless View Post
I am so glad to learn something new....after being involved in the helicopter business since 1967.....and always being a proponent of being able to learn from anyone and everyone no matter their experience level or background....I have to admit AnFi has come up with a new one on me.

Not a single book, article, training course, first hand experience or bar story ever surfaced anything remotely akin to what AnFi is telling us.

I can be convinced of new and innovative techniques.....but it does require some proving.

AnFi ain't there yet.

Care to lay it all out for us?
I think he's just stirring the pot and has a devious sense of humor. It does seem to rattle the cages of the regulars though and they really should know better to respond.
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Old 9th Feb 2020, 15:05
  #50 (permalink)  

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ShyTorque do you think this kind of helicopter has so little 'weather cocking' that it would go to 90 degrees from the cruise? Difficult to believe
Yes. If the tail rotor drive fails, anything might happen unless the correct immediate actions are taken.
Regarding the Wessex accident mentioned, I do know for a fact that RAF crews did not receive detailed simulator training for tail rotor malfunctions on that type (I flew it early in my career). I later became one of the staff who were tasked to develop a full motion sim. syllabus for training RAF helicopter pilots how to deal with T/R malfunctions on another type. Unfortunately there was no simulator that could be used for the Wessex and no interest, probably because the aircraft was approaching the end of its service life.
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Old 9th Feb 2020, 17:40
  #51 (permalink)  
 
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As ever AnFI - lots of wordy theory backed up with no practical experience.

Glad you spotted my red herring of the wrong Llyn At least it made you read the accident report.

The pilot attempted to regain speed - they were doing 60 kts when the driveshaft failed (due to the recoupling of the disconnect coupling and now vastly differing speeds of TR driveshaft and TR) - using forward cyclic but the only way to reduce the rotation was to chop the throttles (you can see in the video that the rate of rotation decreases).

The difficult bit was then judging the point to pull collective to cushion the touchdown whilst spinning - he got it close enough that the impact was survivable for all except, sadly, for some cabin occupants.

I would love to see you you use your 'theory' in a similar situation and manage to be even half as skillful as the pilot was that day.

BTW - who on earth refers to 'a sexy mushroom'????????
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Old 9th Feb 2020, 18:52
  #52 (permalink)  

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I've never heard that phrase before. Maybe a sexy mushroom is a toad's tool?
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Old 9th Feb 2020, 19:54
  #53 (permalink)  
 
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SASless
OF COURSE you already know that you need to point the stick in the direction you want to go !!!
Some people here seem to think you point the stick forward in the cockpit, and put the nose down, that is not the same thing when yawing.


We are all open to learning though, but I feel fairly certain that you must already understand this.
Full credit to you if you only just learned this and have the humility to admit it.
Maybe you would explain it for me to some of the Sim instructors here??

SirK
"rattle the cages of the regulars"
Not really. Or at least I don't mean to, other than perhaps with humour and goodwill.
There's one guy in particular here using underhand and unethical means to try to intimidate/insult me etc.
so when he wrongly corrects me I like to point out that he is wrong.
Flight is a science as well as an art.
Some people don't like when their PoF shortfall is exposed.
In the RAF I guess he would just order peoiple to "shut up, that's an order!".
I prefer reasoned physics and logic than the sniping.

Do we really want an echo-chamber of NorthSea, exRAF, where the world view is that Vortex ring is VooDoo, everything must be duplicated, probabilities come second to gut feel, science is just a clever way to bamboozle people who already have all the answers, urban autorotation is a 10^-9 Catastrophe !!?!!?

ShyTorque
You are clearly a genuine, distinguished and experienced pilot.
That makes it really difficult for me to understand your heli-world view:
"anything might happen" really, do you mean as in: "life is like a box of chocolates"?
Do they make helicopters where just anything might happen?
You said something about yawing through 90degrees
I was only asking if that was really what you thought happens, and now its even worse than that.
(some pilots have not even noticed that their TR Drive system failed 30mins previously in the cruise, its a long way from your 90 degrees etc strange world view)
"correct immediate actions are taken." you mean like using the controls for instance?

"crews did not receive detailed simulator training for tail rotor malfunctions" and that means the whole brewery couldn't organise for these guys to maintain SandL with sideslip. ("slowed till no longer yaw stable", "cut the throttles at 150ft") that DOES NOT NEED DETAILED SIMULATOR TRAINING - surely, really?? really??

"one of the staff who were tasked to develop a full motion sim. syllabus" (as was Crab I think??)

"no simulator that could be used for the Wessex and no interest"
So nothing achieved there then? why not just show it in flight?
5mins bar chat might obey the 80/20 rule?? If you actually knew what to say.

Difficult for me to understand how an experienced pilot can say all that, is this a special RAF thing or a 1967 thing?
Can you really believe what you just said, genuinely?
(You once said you were an engineer by training (i think?), but then said bending has nothing to do with shear, strangely)

Crab
"The pilot attempted to regain speed - they were doing 60 kts when the driveshaft failed"
No - you are completely wrong, again:
from the report:
"
  • Shortly after the aircraft appeared to achieve stabilised flight, the nose began to rise and the aircraft decelerated. The aircraft was now close to its critical yaw angle, beyond which airflow separation over the rear fuselage/tail pylon occurs, thereby removing its yaw stabilising, ‘weather-cock’ effect. This angle appears to have been reached after 13 seconds of stable flight, when the yaw began to increase significantly.
"

You live in a world where when a pilot simulates an emergency with cadet passengers on board(!), causing a TRDS failure, then screws up the response, everyone gets a medal and its a 'training problem'. You live in a fantasy world. Must be nice.

"the only way to reduce the rotation was to chop the throttles" also not true. Fatal consequences, incompetence (ie not competent to resolve a simple (self induced) tail rotor drive shaft failure, whilst in a simple flight regime, S&L. Just useless).





What was the budget of this helicopter unit?
$50m? $100m? and it takes how many people at a highly trained level to fail to carry a heart to transplant op.
Cudda got the nurse's brother's friend to carry it over for a share in the petrol. When is this going to get real?
Another helicopter not saved by having 2 engines.... post institutionalised folk damage civil aviation worldwide.
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Old 9th Feb 2020, 20:21
  #54 (permalink)  
 
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Got to hand it to you AnFI, you are always good to pep up a thread or two for a few pages until it all gets google-eyed bananas.

You are of course right in one respect in particular: If they hadn‘t been flying that over-designed, overpowered helicopter, they would have had less of a yaw emergency to deal with. But don‘t waste your time here, write directly to the Japanese Police and paint a different, lower risk future.

btw you need to check in more often or pay more attention: Crab flies this type and will know very well how ugly LOTRT issues are in it.

Yours in sport

TT
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Old 9th Feb 2020, 20:52
  #55 (permalink)  
 
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Originally Posted by ShyTorque View Post
Once the fuselage yaws 90 degrees to the direction of travel, the drag increases exponentially and you're an involuntary test pilot and might have little say in what the aircraft does, at least for a few seconds. With a rapidly rotating fuselage, pitch may become roll and roll may become pitch.
I agree! I just (3 days ago) had an opportunity to simulate a coupled cruise flight in A139 Sim (CAE) with a TR shaft failure. If the pilot DOESN’T REACT at all, the helicopter easily turns 90 degrees... 180 degrees... even 270 degrees... pitching and rolling quite violently. At least CAE SIM is modelled so... based on the data from Leonardo... I guess...🤔

Cheers! 😉
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Old 9th Feb 2020, 21:38
  #56 (permalink)  
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Gents,
The AW-139 has both a FDR and a CVR, let's see what reading those two shall reveal.
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Old 9th Feb 2020, 21:48
  #57 (permalink)  
 
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Originally Posted by tottigol View Post
Gents,
The AW-139 has both a FDR and a CVR, let's see what reading those two shall reveal.
It was a good ”time out” call Tottigoll! 😁 It will be interesting and a useful lesson to learn, when the report comes out... 😉
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Old 9th Feb 2020, 22:13
  #58 (permalink)  

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Originally Posted by Search&Rescue View Post
I agree! I just (3 days ago) had an opportunity to simulate a coupled cruise flight in A139 Sim (CAE) with a TR shaft failure. If the pilot DOESN’T REACT at all, the helicopter easily turns 90 degrees... 180 degrees... even 270 degrees... pitching and rolling quite violently. At least CAE SIM is modelled so... based on the data from Leonardo... I guess...🤔

Cheers! 😉
SAR,
Irrespective of what you, the manufacturer and I think, it appears that this AnFI thinks he knows better, as is his way.
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Old 10th Feb 2020, 01:38
  #59 (permalink)  
 
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The most common issue I see daily in the FFS when practising loss of TR thrust in cruise flight is pilots allowing the IAS to gradually bleed off while startled or distracted by looking for a landing site etc. If this happens there comes a point in the power/ airspeed combination when the nose suddenly and rapidly departs to the right. Unless you dump the lever rapido at this point, we are just counting down to the red screen. The yaw rate makes extremely difficult to gain airspeed whatever you try to do with the cyclic.
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Old 10th Feb 2020, 05:28
  #60 (permalink)  
 
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Originally Posted by Search&Rescue View Post
I agree! I just (3 days ago) had an opportunity to simulate a coupled cruise flight in A139 Sim (CAE) with a TR shaft failure. If the pilot DOESN’T REACT at all, the helicopter easily turns 90 degrees... 180 degrees... even 270 degrees... pitching and rolling quite violently. At least CAE SIM is modelled so... based on the data from Leonardo... I guess...🤔

Cheers! 😉
I am sure that you are right that the SIM does this.
If the aircraft does this, then how is it allowed to fly?
Who would fly in such an aircraft? Darwinian process at work maybe?

ShyTorque
Yes it is hard to believe, but if you say this aircraft is that bad/dangerous i have to believe you. You say: "...you're an involuntary test pilot and might have little say in what the aircraft does, at least for a few seconds. With a rapidly rotating fuselage, pitch may become roll and roll may become pitch." Either it is that bad or you don't understand this (making you an ideal person to write the book??).

There are accident reports, an H369 in Australia is one, non-event. and a gazelle in UK where the drive shaft failures were bearly noticeable (in the Gazelle for HALF AN HOUR !!)

TorqueTalk
I know you are right. Just sad to have people believe they are buying an extreme safety level with this complextity.


tottigol agree
Non PC Plod quite right, an easy mistake to make
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