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The Hudson River "LTE" Accident


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#21 Fred0311

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Posted 03 June 2019 - 12:14

You're so melodramatic!

,...and with such a Charles Bronsonesque grudge against LTE! I don't remember Bob, do you have a mustache?

There's no way you forgot that stache....



#22 Nearly Retired

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Posted 03 June 2019 - 23:29

First of all, Butters STFU.

 

Secondly, I am not on a crusade against LTE.  I just think that too many times it is used as an excuse for poor piloting.  Because it's hard to disprove.  If the pilot says he got into an "uncontrollable" spin that he could not stop with full left pedal, then who can say otherwise?  And who would?  We try very hard to exonerate the pilot.  

 

In one of the recent Boeing 737 Max-8 crashes (Lyon Air or Ethiopia, I forget), the MCAS was erroneously commanding nose-down trim.  The pilots tried using the electric trim switch on the yoke, but as soon as they were done trimming the nose up, the MCAS trimmed it back down.  The airplane got faster and faster becuase the dummies in the pointy end NEVER PULLED THE POWER BACK.  Thus, the manual trim wheel became unusable because the aerodynamic forces on the stabilizer made it too difficult to move.  Eventually, the nose-down forces on the control wheel got so heavy that both pilots pulling together could not get the nose up.

 

The fact that these pilots never throttled back is astonishing to the investigators.  Why *NOT* pull the power back?  Well, because they were getting an erroneous stall-warning indication for one thing, but their THREE airspeed indicators should have persuaded them that the stall-warning system was malfunctioning and that it would be safe to slow down.  They did not.  They *did* shut the stabilizer trim switches off, which should have allowed them to regain pitch attitude control, but they were still too fast for the manual trim wheel to be used.  So instead of slowing down and reducing the aerodynamic forces on the elevator, they unbelievably turned the stabilizer trim switches back on!  It sealed their fate.  The MCAS continued to command more nose-down trim.  They crashed.  And now all of the 737 Max-8 planes are grounded. 

 

Sooooo, what part of this accident did pilot-error play?  Yes, the airplane was not reacting normally, but people smarter than me theorize that it could have been saved if the pilots were...you know...sharper. They did not have to be going that fast.

 

Okay, back to the matter at hand.  I would wager that 90% or more of all Bell 206 "LTE" accidents are simply pilot-error, where the pilot let the aircraft get out of control.  Claiming that an accident was "LTE!" tarnishes the reputation of the Bell 206, a safe, reliable aircraft in which I have considerable time and experience.  In fact, I probably have more time in a downwind OGE hover in a 206A than many of you experts have total time.  Yes, I'm talking to you, Butters.

 

The NYC L-4 accident was not LTE.  Let's stop calling it that.  He did not lose effectiveness of his tail rotor; he simply did not avail himself of all the power it had.


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#23 r22butters

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Posted 04 June 2019 - 12:12

First of all, Butters STFU.
 


Sure thing pallie, just let me know when Death Wish 206 comes out.

,...'cause LTE's gone too far this time!

#24 Spike

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Posted 04 June 2019 - 12:15

IMHO, this particular incident was poor ADM which resulted into LTE causing a crash. Fix the ADM, and the link in the accident chain is broken.

During 206L check-rides at a former ENG employer, we were required hover OGE at 1500 feet, downwind, then start hovering backwards until the machine snapped around. Pilots were required to apply full left peddle and lower the collective and fly out of it, which we did, with a loss of about 150 feet at minimum, 300 feet at max. I can say, it didnt take much to get the machine to snap around. The lesson, dont attempt to hover downwind.

Birds understand the importance of landing into the wind. If their tiny brains can grasp the significance of this concept, maybe we humans should do the same.
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#25 Jaybee

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Posted 04 June 2019 - 16:24

Could you elaborate? I am assuming you made a typo, because having a groundspeed lower than the tailwind component results in weathervane tendency and increased power demand. Hovering OGE (0 groundspeed) with a 10 knot tailwind, is not a good position to be in.

 

No typo.

 

But you are changing the rules of the game.

 

I said "dangerous'. You said "more power" and "not a good position".

 

I never claimed it was the best idea or even mentioned power. 

 

If you are cognizant of the situation you put yourself in and the inherent risks and limitations that imposes on you and thereby how to get yourself out of it there is nothing "dangerous" about the maneuver. Idiot pilots make it dangerous not the maneuver.

 

In a rush to be right though everyone wants to change the rules of the game, instead of taking a deep breath and allowing there brains to wrap around a new thought. 

 

For whatever its worth, my instructor won many awards including the Art Scholl for his Helibatic Airshow Act. I have been privileged with getting to explore the edges of the envelope with him.


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#26 Hand_Grenade_Pilot

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Posted 04 June 2019 - 19:27

No typo.
 
But you are changing the rules of the game.
 
I said "dangerous'. You said "more power" and "not a good position".
 
I never claimed it was the best idea or even mentioned power. 
 
If you are cognizant of the situation you put yourself in and the inherent risks and limitations that imposes on you and thereby how to get yourself out of it there is nothing "dangerous" about the maneuver. Idiot pilots make it dangerous not the maneuver.
 
In a rush to be right though everyone wants to change the rules of the game, instead of taking a deep breath and allowing there brains to wrap around a new thought. 
 
For whatever its worth, my instructor won many awards including the Art Scholl for his Helibatic Airshow Act. I have been privileged with getting to explore the edges of the envelope with him.

I understand the point you are making now. And I agree; as long as the pilot maintains situational awareness in regards to their environment, power margin, power pedal travel remaining, etc it is not dangerous operating downwind. But if a pilot is ignorant of any of the variables, or becomes fixated/distracted, it can quickly turn into an unfavorable situation.
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#27 iChris

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Posted 05 June 2019 - 13:10

Lack of Training and Experience (LTE)

 

He’s coming in to land, everything looks pretty good. Probably dancing on the pedals because he’s downwind; nevertheless, everything is still under control. Then he decides to go around. Instead of flying it around and coming back in, giving himself room for his landing approach, he gives up his airspeed and slows into an OGE hover and tries to pedal turn back toward his landing pad. Very surprising to me why he would do that since he stated he knew the wind conditions.

 

It all turns bad at 0:13 in the video. The helicopter is talking to the pilot, in its own way, giving him clues to what’s about to happen, if he continues with this madness. The helicopter is saying, I don’t want to make this right pedal turn, the weathervane effect is too strong, and once the turn starts, I won't be able to stop it, unless you're super-fast with full left pedal.  

 

You can see the pilot fighting with the helicopter trying to make that right hovering pedal turn work. I bet he had almost full right pedal trying to break through the weathervane effect. Two problems with this situation. One, right pedal decreases tail rotor pitch, thereby decreasing anti-torque thrust. Two, the left side of the helicopter is perpendicular to the wind. The wind in combination with a bit of main rotor vortex is now in opposition the tail rotor's induced velocity, thereby further reducing anti-torque thrust. The Pilot has unwittingly relinquished most of his anti-torque thrust, just seconds before it's going to be needed. It wasn’t a Lack of Tail-rotor Effectiveness, he relinquished most of that, it was due to his Lack of Training and Experience 

 

He’s ignored the helicopter’s clues and warnings. So, around they go. He’s become a passenger along for the ride, out of this control. The pilot had no clue what was about to happen, if he had, he wouldn't be in this situation. In fact, he’s probably so surprised from the abrupt uncommanded right yaw, being he was already applying right pedal, he subconsciously freezes, doing little or nothing with respect to pedal input. There's no deceleration evident in that spin, he never applied full left pedal in a timely fashion. If you’re late with the pedal, its too late. Fortunately, he survived.  

 

ADM maybe, but ADM assumes you have the prerequisite knowledge to make the right decision in the first place. The basic prerequisites would’ve prevented this accident. just one simple thing, everyone should've been taught, when hovering in windy conditions, always make your first hovering turn to the left in counterclockwise (US) rotor systems and to the right in clockwise (UK) rotor systems. 

 

Had that been done in this case, he most likely would have run out of left pedal or close to it before breaking through the weathervane effect. Taking heed to that clue, moving on to Plan B, avoiding low-speed maneuvering downwind. Being extremely careful when performing out of ground effect pedal turns with winds above 10 knots. You need to fly the helicopter in the direction it needs to go, not hover it, maintaining airspeed above translational whenever possible.

 

It’s not the helicopter, the tail-rotor never lost effectiveness

 

Bell 206L4-FM - Satisfactory stability and control have been demonstrated in each area of the Hover Ceiling charts with winds as depicted on the Maximum Safe Relative Winds chart (Figure 4-5).

 

AREA A (unshaded area) 3000 FEET AND BELOW

 

IGE — winds from any direction up to 35 knots.

 

OGE — for azimuths from 150° clockwise to 060°, winds up to 35 knots; 

 

for all other azimuths, winds up to 30 knots.

 

FAA AC90-95 - LTE is not related to a maintenance malfunction and may occur in varying degrees in all single main rotor helicopters at airspeeds less than 30 knots. LTE is not necessarily the result of a control margin deficiency. The anti-torque control margin established during Federal Aviation Administration (FAA) testing is accurate and has been determined to adequately provide for the approved sideward/ rearward flight velocities plus counteraction of gusts of reasonable magnitudes. This testing is predicated on the assumption that the pilot is knowledgeable of the critical wind azimuth for the helicopter operated and maintains control of the helicopter by not allowing excessive yaw rates to develop.

 

Accident Preliminary Report

 


Edited by iChris, 05 June 2019 - 23:49.

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Regards,

Chris

#28 iChris

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Posted 05 June 2019 - 16:03

In almost all of these so-called LTE/loss of control accidents, pilots always state they applied full left pedal. No, they didn’t. They had no clue what was about to happen. They were so surprised from the abrupt uncommanded right yaw, they subconsciously freeze, doing little or nothing with respect to pedal input.

 

Example: Cockpit video Bell 206, Van Nuys, CA. So-called LTE accident, pilot states full left pedal was applied. The video shows otherwise. It turns bad at 0:45 in the video. At 0:47-0.48 there you see it, feet frozen, nothing with respect to full left pedal input. 

 

NTSB Aviation Accident Data Summary

 

 

oCsI3zF.png


Edited by iChris, 05 June 2019 - 16:25.

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Chris

#29 Nearly Retired

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Posted 05 June 2019 - 19:11

Thank you, Chris!  Well said.  Maybe people will listen to you instead of me; I seem to have little credibility when it comes to such issues.



#30 Hobie

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Posted 05 June 2019 - 19:55

I truly appreciate all of the high timers and their sage advise. Thank you guys.  The main takeaway from you guys is *never* let your guard down. 



#31 r22butters

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Posted 06 June 2019 - 00:38

"Lack of Training and Experience"? Gee, I make that joke and the crowd is silent, Chris makes it his thesis and here come the likes,...no, I told myself I wouldn't get emotional :(

Still, why is it "So-called LTE"? If the pilot's feet just sat there lifelessly, isn't that how LTE happens?

Anyway, my opinion is irrelevant and this stupid topic is almost as exhausting as the ones on vrs is/is not swp and skid time vs. blade time!

Its The Bug, that's who I'm waiting for. This ridiculousness ain't over 'til Buggieboy makes the final decree!

#32 Nearly Retired

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Posted 06 June 2019 - 02:04

Butters, the tail rotor doesn't lose effectiveness if you don't use it.



#33 r22butters

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Posted 06 June 2019 - 12:03

Butters, the tail rotor doesn't lose effectiveness if you don't use it.




#34 Wally

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Posted 06 June 2019 - 13:10

Y'all keep talking about tail rotors, LTE, LTA, etc.,like there is some kinda magic involved in that specific control.  There's no magic or exclusive property of tail rotors, everything you do with the machine has limits, yours or the machines'. 

Knowledge is the key and planning is the lock that opens the door to survival when you encounter a limit.  Based on my experience in having pushed full pedals in either direction on occasion and seen inadequate response to perform the maneuver anticipated, the situation is survivable- if you prepared for it by having a survivable plan. You know- or should know that fin effectiveness depends on airspeed.  You should know that torque compensation is related to the fin and power demand.

 

I'm not going to pretend to know what happened in the video or teach avoidance.  I will tell you what worked for me: high steep slow and cautious, with an abort planned and executed at "X" condition.

If the safest approach is downwind, establish the path and speed high enough that you can safely fly out  Test your pedal and stick for limits as you fly the approach.  Know and plan for the limits to change as your tailwind component increases and I abort if I think I might be approaching a limit.  Power demand is also a yaw control...  I do not have to follow the nose on my approach, all I have to do is be able to follow a controlled descent path onto the point of landing- this ain't an airplane.  What's most difficult is maintaining vis and clearing the area from the pilot.  I prefer to land with the tail away from ground access, but that doesn't mean I must do so.  If I can  control access path and provide adequate clearance with the tail in any other direction, might do so

It is possible in some circumstances to yaw the aircraft in the 'wind shadow' on the pad when you couldn't point it where you wanted in flight. It us also possible that the entire approach turns to crap when you encounter the orographic turbulence as you try to enter the 'wind shadow'.

Sometimes I could adapt and sometimes I couldn't and I diverted to another site.


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Just a pilot (retired, so I have a LOT of time)...


#35 Franz123

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Posted 06 June 2019 - 20:13

I agree with you Cris



#36 Spike

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Posted 07 June 2019 - 13:59

Darn iPhone.... See below.

Edited by Spike, 07 June 2019 - 17:08.


#37 Spike

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Posted 07 June 2019 - 14:00

Thats what the investigators/lawyers will say; the pilot *knew* or *should have known* the dangers of a tail wind landing.

The most basic level of training and experience includes why pilots should avoid such conditions. He made the decision to do what he did and paid the consequences.

Edited by Spike, 07 June 2019 - 14:01.

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#38 r22butters

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Posted 18 June 2019 - 14:22

Looks like this guy had better luck with his "LTE" moment :D






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