For my Rotorheads- What happened here?

RyanB

RyanB

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SWP or LTE?

 
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Loss of tail rotor authority. Pitch change link or tail rotor gear box. Must've been no wind or it would've been more violent.
 
I don't know anything about that incident, but looks like LTE.

There's a difference between LTE (which is a factor of aerodynamics and power available) and loss of tail rotor thrust (which is mechanical). This looks like the former. IOW, nothing broke on the aircraft, the pilot just got into a situation the helicopter couldn't handle. Certain Bell products are far more susceptible to this than most helicopters.
 
Without being able to see the anti torque pedals (whether or not the pilot gave it all she got or not) and/or the torque gauge - my best guess is its a pilot induced dumbassery.

Came in shallow and slow at what looks to be a relatively high altitude at who knows how hot with little to no wind - that's just asking for something bad to happen.

For whatever its worth I spent 800 hours flying mountainous (above 5000 DA) at or near max gross for conditions and I flew the way my instructor taught me (old guy) and all the old guys I ever flew with that were still alive after 30 years of helicopter flying all liked how I flew my approaches.

At 200' AGL slow to ETL, power applied early, steep approach riding the bubble, fall out of ETL at the bottom as you come into IGE - you'll know with altitude to spare if you have the power or not.

Some guys would like to come in fast and shallow with a big flare into an IGE hover, the problem with that is you don't know if you have the power to pull through at the bottom until its too late.

In the video, they are basically trying to HOGE (hover out ground of effect) their way all the way to a landing, again bad idea. as soon as that nose started to yaw the pilot should have lowered the collective a smidge and pushed forward on the cyclic for airspeed - kind of like the blue line on OEI multi engine work, it isn't natural to push the nose over near the ground but its the right thing to do. all pulling power in is going to do is make the nose yaw more, as you see in the video.
 
LTE. Would’ve spun much more violently with loss of tail rotor thrust. Probably high altitude and heavy. If he would’ve just kept his speed above ETL before going into IGE, he would’ve been golden.

Winds don’t appear to be a factor here but they can be. Friend of mine got into LTE in a 407 with a strong right crosswind. When he pulled in power at the bottom for landing, the nose yawed right, he applied full left pedal but the nose kept going right. Did a go around and pulled 116 % TRQ :eek:and almost balled it up.
 
Velocity173 said:
Friend of mine got into LTE in a 407 with a strong right crosswind. When he pulled in power at the bottom for landing, the nose yawed right, he applied full left pedal but the nose kept going right. Did a go around and pulled 116 % TRQ :eek:and almost balled it up.
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Eek! So what would’ve been the best action to take in that situation?
 
Ryanb said:
Eek! So what would’ve been the best action to take in that situation?
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Exactly what Jaybee said. First thing is get some of that collective out. You can bet he’s got the collective up in his armpit creating a huge amount of trq, which tries to yaw the nose right. Reducing collective while keeping full left pedal will easily bring the nose back left. Similar to right stuck pedal; get off the trq. Second thing is, get some speed. Get back up to ETL (15-20kts ish) to reduce drag (vortices/ induced flow). That drag reduction will also contribute to a reduction in trq. Once he descends down into IGE which will further reduce that drag, he’s got it licked. Easier said than done though. It’s about not panicking and work through the problem. This pilot chose the worst possible recovery because avoiding the ground while spinning is a strong impulse.

The key in all of this is no different than a fixed wing landing or taking off a high altitude. You gotta do the planning before you arrive. First question is, do I have OGE power? If you’re borderline like in this vid, you run the risk of both SWP and LTE. If you don’t have it or borderline, then milk ETL (15-20) until getting into IGE (about 1 rotor disk). Even if I have plenty of OGE power I still keep my speed up to try and minimize my time in the avoid range (engine out).
 
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Velocity173 said:
Exactly what Jaybee said. First thing is get some of that collective out. You can bet he’s got the collective up in his armpit creating a huge amount of trq, which tries to yaw the nose right. Reducing collective while keeping full left pedal will easily bring the nose back left. Similar to right stuck pedal; get off the trq. Second thing is, get some speed. Get back up to ETL (15-20kts ish) to reduce drag (vortices/ induced flow). That drag reduction will also contribute to a reduction in trq. Once he descends down into IGE which will further reduce that drag, he’s got it licked. Easier said than done though. It’s about not panicking and work through the problem. This pilot chose the worst possible recovery because avoiding the ground while spinning is a strong impulse.

The key in all of this is no different than a fixed wing landing or taking off a high altitude. You gotta do the planning before you arrive. First question is, do I have OGE power? If you’re borderline like in this vid, you run the risk of both SWP and LTE. If you don’t have it or borderline, then milk ETL (15-20) until getting into IGE (about 1 rotor disk). Even if I have plenty of OGE power I still keep my speed up to try and minimize my time in the avoid range (engine out).
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Good explanation. So to be clear, you can still get into an LTE situation even if you don’t have any wind?
 
Ryanb said:
Good explanation. So to be clear, you can still get into an LTE situation even if you don’t have any wind?
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It can occur without wind but it will be a high altitude and heavy situation. Basically the air is so thin that the tail can’t overcome the trq from the main rotor.

Also depends on aircraft. Some are more susceptible to LTE than others. Some of your smaller helos can get into it in surprising conditions while some of your larger more powerful ones you’d have to be a special kind of stupid to get into it. In 206 training LTE was thoroughly covered. In Black Hawk training I remember an instructor said something like “LTE, yeah...it’s not an issue for us.”:)
 
Velocity173 said:
It can occur without wind but it will be a high altitude and heavy situation. Basically the air is so thin that the tail can’t overcome the trq from the main rotor.

Also depends on aircraft. Some are more susceptible to LTE than others. Some of your smaller helos can get into it in surprising conditions while some of your larger more powerful ones you’d have to be a special kind of stupid to get into it. In 206 training LTE was thoroughly covered. In Black Hawk training I remember an instructor said something like “LTE, yeah...it’s not an issue for us.”:)
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That makes sense. Thanks for the explanation.
 
Ryanb said:
Good explanation. So to be clear, you can still get into an LTE situation even if you don’t have any wind?
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If'n ye wantin' to split thee hairs...
NO.
Without a three page long diatribe that spawns arguments between helo pilots the world over - LTE is a wind produced effect, the running out of tail rotor at high altitude is a running out of power or LTA loss tailrotor authority, the tail rotor is making thrust its just doesn't have enough juice to make enough. That'n be a nitpickin' however and goes back to who trained you how kind of thing. End of the day, pilot messed up don't really matter exactly technically why.

LTE - is uncommanded yaw which if uncorrected for will result in loss of directional control
If you pull more power than you have tail rotor that is a commanded yaw of your own doing.

Nits picked. Peace.
 
Lots of rotor wing acronyms in this post. I can guess what some of 'em are, but it'd be helpful if you fling wing guys would define:

OGE (Out of ground effect?)
IGE (In ground effect?)
LTE ???
LTA ???
ETL (??? Transitional lift)
 
PaulS said:
How about an acronym glossary so we mere fixed wing pilots can follow???
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kyleb said:
OGE (Out of ground effect?)
IGE (In ground effect?)
LTE Loss of tail rotor effectiveness
LTA Loss of tail rotor authority
ETL (effective transitional lift)
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jaybee said:
If'n ye wantin' to split thee hairs...
NO.
Without a three page long diatribe that spawns arguments between helo pilots the world over - LTE is a wind produced effect, the running out of tail rotor at high altitude is a running out of power or LTA loss tailrotor authority, the tail rotor is making thrust its just doesn't have enough juice to make enough. That'n be a nitpickin' however and goes back to who trained you how kind of thing. End of the day, pilot messed up don't really matter exactly technically why.

LTE - is uncommanded yaw which if uncorrected for will result in loss of directional control
If you pull more power than you have tail rotor that is a commanded yaw of your own doing.

Nits picked. Peace.
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Good point. That’s what I was curious about, as it’s easy to view the two synonymously.
 
Page 11-20. LTE at altitude is a seperate condition from the 3 wind conditions. It’s due to a pilot operating outside of the tail rotors ability to produce thrust to counter trq. Could be due to the thin air, lack of rpm or combo. Perhaps LTE isn’t the best way to describe it but that’s what the FAA still uses.

https://www.faa.gov/regulations_pol...helicopter_flying_handbook/media/hfh_ch11.pdf

To be honest I’ve never heard LTA used in an official capacity before other than a loss of tail rotor thrust condition. I’ve heard of “lack of tail rotor authority” used in LTE but even then, never seen it as an FAA definition. This guy makes up his own acronym of NETR or “not enough tail rotor.”

http://www.rotorandwing.com/2011/11/29/loss-of-tail-rotor-effectiveness-bell-206/

Whether it’s LTA, LTE or NETR, the 206 does have specific weight and density limits for it due to keeping the tail rotor within “stall margins.”

https://vanhornaviation.com/documents/206L1-FMS-901.pdf
 
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@Velocity173 Meh, FAA woefully behind the times as usual - https://www.cnatra.navy.mil/local/docs/pat-pubs/P-401.pdf

Can't copy paste from the PDF file so just a snippet...

Naval Air Training Command said:
Section 610

1. LTA and LTE

The ability of the tail rotor to provide anti-torque and yaw control can be greatly reduced by two factors that are easily confused. LTA is related to power available to the the main and tail rotor. LTE is related to the direction from which the wind strikes the tail rotor in a hover and tends to be labeled as an aerodynamic phenomenon compared to LTA, which is most often described as a mechanical phenomenon."
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It then goes into greater detail about LTA and LTE. They also identify 5 critical wind azimuths vs the FAA's 3.
 
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Choppers? Nothing new here. "Flying" those things is like taildraggers, break-even propositions at best.:stirpot: ;)

HOGG, get away from that thing! :D
 
So unnecessary, not even a really confined area. After seeing so many vertical TOs and LDGs, one of the most disappointing things about helicopter performance is how often they must be significantly flown like airplanes when in high DA.
 
jaybee said:
@Velocity173 Meh, FAA woefully behind the times as usual - https://www.cnatra.navy.mil/local/docs/pat-pubs/P-401.pdf

Can't copy paste from the PDF file so just a snippet...



It then goes into greater detail about LTA and LTE. They also identify 5 critical wind azimuths vs the FAA's 3.
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Well, I guess the Navy leads the way. :cool:All depends on your reference I suppose. The Canucks and the Aussies go with LTA as a mechanical failure or “loss of tail rotor thrust.”

https://www.tc.gc.ca/eng/civilaviation/opssvs/civil-aviation-safety-alerts-2017-02.html

https://www.atsb.gov.au/media/5772474/ao-2016-159-final.pdf

This author describes LTA as the weather cock region???:confused:

http://www.aviation-training-books....odynamic-performance-aspects-of-a-helicopter/
 
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Ouch, that was hard to watch. Jaybee nailed it.
 
I slept at a Holiday inn once

Heh I don't know about lead the way but for my brain waves the Navy material synched up and made more sense to me then how the FAA tried to explain it. The problem with the FAA explanation - while i don't necessarily disagree that calling everything tail rotor LTE is that by their own definition LTE is uncommanded. While it be splittin' thee hairs i think it's more direct, succinct and just all around clearer to break it up into LTA and LTE. Again, depends on who trained you kind of thing. Weird because the guy who taught me was a Kiowa Warrior showing me Navy material
 
Keep in mind the density altitude can be very high in Guatemala. The highlands get, well, high. And it is in the tropics, so heat had humidity can get up there even i the highlands. Don't know if that contributed to what happened to the helicopter, since you rotor heads seem to really enjoy speaking in acronym.
 
steingar said:
Keep in mind the density altitude can be very high in Guatemala. The highlands get, well, high. And it is in the tropics, so heat had humidity can get up there even i the highlands. Don't know if that contributed to what happened to the helicopter, since you rotor heads seem to really enjoy speaking in acronym.
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Yeah, but at the first sign of a problem...and the sign was there long enough...fly out of it. I had a tough instructor. Really tough. And he drilled that time and again.

And of all the weird things rotorheads do, we refer to the things on the floor as pedals. Everyone knows what they really are.
 
jaybee said:
I slept at a Holiday inn once

Heh I don't know about lead the way but for my brain waves the Navy material synched up and made more sense to me then how the FAA tried to explain it. The problem with the FAA explanation - while i don't necessarily disagree that calling everything tail rotor LTE is that by their own definition LTE is uncommanded. While it be splittin' thee hairs i think it's more direct, succinct and just all around clearer to break it up into LTA and LTE. Again, depends on who trained you kind of thing. Weird because the guy who taught me was a Kiowa Warrior showing me Navy material
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I don’t mind breaking both up but standardizing it across the board would be nice. The Army doesn’t even give it a name. Just a one liner:

In some helicopters during high altitude operations, the maximum antitorque produced by the tail during a hover may not be sufficient to overcome torque even if gross weight is within limits.

LTA or LTE, as long as pilots realize the above statement can happen, that’s all that really matters.
 
Dave Krall CFII said:
So unnecessary, not even a really confined area. After seeing so many vertical TOs and LDGs, one of the most disappointing things about helicopter performance is how often they must be significantly flown like airplanes when in high DA.
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79FFF9EB-F150-4C85-9D5B-C43FC02F0EE6.jpeg
It’s also amazing how often they can be flown as helicopters. At a hover with a 14,000 ft DA with no worries about staying in IGE, above ETL or getting into LTA. ;)
 
Velocity173 said:
View attachment 62757
It’s also amazing how often they can be flown as helicopters. At a hover with a 14,000 ft DA with no worries about staying in IGE, above ETL or getting into LTA. ;)
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Cool. Yeah, in HP Beasts like that, probably carrying nothing except filled with helium balloons... ;) Curious what was the temp and wind doing?
 
Dave Krall CFII said:
Cool. Yeah, in HP Beasts like that, probably carrying nothing except filled with helium balloons... ;) Curious what was the temp and wind doing?
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Ah, I think temp was maybe 1C, 12,600 PA and winds calm. I believe we were within 5 % of max trq available so we weren’t exactly doing it without breaking a sweat. Wrong kind of winds (Air Force Mt Hood 2002) and things would get ugly real quick.

Gotta friend who flys Ospreys in the Marines and he said they wouldn’t even come close to pulling off an OGE hover in those conditions. Great aircraft but hovering OGE isn’t a strong suit for tilt rotors.
 
Velocity173 said:
Ah, I think temp was maybe 1C, 12,600 PA and winds calm. I believe we were within 5 % of max trq available so we weren’t exactly doing it without breaking a sweat. Wrong kind of winds (Air Force Mt Hood 2002) and things would get ugly real quick.

Gotta friend who flys Ospreys in the Marines and he said they wouldn’t even come close to pulling off an OGE hover in those conditions. Great aircraft but hovering OGE isn’t a strong suit for tilt rotors.
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Nice. What was your weight?
Got an old flight student that went on to fly Ospreys for a few tours and then flight training, then slow death by desk. Never even came by to give me a ride.
 
Dave Krall CFII said:
He don't need no stiiinking checkout to fly a chopper -for a while.
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The story I heard about this was the owner got tired of waiting for his instructor and decided to leave without him.

Also heard his wife told him his dream of flying a helicopter was over and that his insurance check will be for the new Motor home...
 
Dave Krall CFII said:
Nice. What was your weight?
Got an old flight student that went on to fly Ospreys for a few tours and then flight training, then slow death by desk. Never even came by to give me a ride.
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Maybe 15,500-16,000 lbs.
 
I have never seen LTA used..just LTE...then again I have been in a OH-58 in conditions where you could not peddle turn at a hover due to a 45-50 mile an hour wind and could not shut down as well without the chance of taking the tail boom off...the tail rotor had full authority but not the ability...
 
Dave Krall CFII said:
What kind of T.O. when you picked the guys up?
Also, congratulations on that American Flag plant. That must've took some doing, any story available?
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Take off? They were basically standing near the edge of a mountain ridge. Just dropped over the edge, pitched down and accelerated out. Similar to this vid only we didn’t have to do a one wheel landing.

They didn’t plant the flag there. It was just a re-enlistment for one of our crew chiefs. Not sure why their faces are blurred out. Can’t remember who sent me the pic but that’s the way it came.
 
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