206L Crash on YouTube

[Old Skool]

Blenderpilot is right, if i am operating within the usual limits i should be able to control the heading of the aircraft with the pedals, if not then the T/R isn't up to the job.

[BlenderPilot]

If LTE was Vortex Ring, or interference from the main rotor or whatever . . . .

Then why don't you ever hear of people in Bell 407 (for example) ever getting LTE?

The answer is simple, that is because the 407 has a powerful, adecuate tail rotor, and the 206L3,L4 doesn't.

If I am correct the tail rotor in the 407 will provide adecuate control margin up to 35 knots of sideward flight, and the 206's will barely do at 17 knots, something to do with certification standards.

The 206 JetRanger dosen't get into so called LTE because it isn't very powerful, and thus you will run out of power before you run out of tail rotor most times.

[ReverseFlight]

I sympathise with all of you. I have come across so many LTE theories - it is probably the most controversial of all helicopter flight theory topics.

Many textbooks give the usual three LTE scenarios : (1) wind from the rear, (2) wind from the main rotor and (3) tail rotor vortex. Some say the tail rotor stalls in LTE ; others say it does not stall but rather merely loses its effectiveness.

My flight school says that weathercocking in a tailwind is not LTE : it's only a pedal control problem. This is akin to the B206 POH warning against running out of left pedal in a right crosswind : it's just a control problem, not LTE.

Frank says that the tail rotors of his R44s are large enough to be LTE proof. However in practice, R44s are crashing due to LTE even with left pedal full forward.

I am also well aware of Nick Lappos's theory that LTE does not really exist : it is entirely due to undersized tail rotors. I personally believe that is a plausible explanation, although I have found that insurance companies do not buy that argument when the proverbial hits the ceiling rotor. Insurance companies revert to the traditional Bell definition so that the blame falls squarely on the pilot, not the manufacturer. That is the reality of LTE.

Whatever label you call it, or however it develops, the proper corrective action of reducing torque will avoid increased premiums, litigation and a lot of butt pain besides.

[Runway101]

Maybe he is referring to the loss of tail rotor THRUST as outlined in section 3 (emergency procedure) in the R44 POH. It says "failure is usually indicated by nose right yaw which cannot be corrected with by applying left pedal".

There was an R44 accident in Hong Kong where they spoke a lot about LTE (helo spinning on take off). Was also discussed here if I remember right.

http://www.cad.gov.hk/reports/Aircra...ort_1-2007.pdf

[ReverseFlight]

Runway101, the Hong Kong one appears to be a combination of lifting off downwind and then making a yaw turn to the right. If that doesn't induce LTE, I'd be surprised, even with left pedal in full forward position (page 33 of pdf image, section 1.12.4 of the report).

Note also the report talks about the tail rotor being stalled (page 70 of pdf image, section 3.1.7) ? I suspect the majority of Ppruners would say that is wrong.

[407TX]

206

Gentleman's,

It is interesting to read about this, I have taking off from the exact place that L is taking off in Ecuador, the place is about 9800 feet PA, you can have temperatures from -10 to +15 depending the time of the year(on that day the winds were light and variable), now let’s go back in time, the pilot that was flying that helicopter was an Iranian fellow(nothing wrong with that) but with less than 500 hs of total time in helicopters, if you see the clip carefully, if he picked up the helicopter and pointed toward the guy that was filming and made a normal take-off, we will not be talking about this, but in his own words he mentioned "that somebody told him to do a climb with slight right pedal because he will be using less power", well, you guys know the result of this one.
It is not an LTE problem like Blender Pilot is pointing out, and I know how much "working experience" you have in Mexico, (you didn't make the cut at the PGR, decent pilot, excellent pictures), I can tell you that I can show LTE in any aircraft, even in the 407 (over 2,000 hs in that one), don't blame Bell for that one, this one is because the pilot didn't have the minimum experience and common sense to be "working at that altitude".

[helmet fire]

I have trawled the previous threads on the LTE issue and have posted the following summary for future reference. It is made up from the previous work of three authors, Nick Lappos, Arm out the Window and myself. Thanks/apologies to Nick and AOTW!

If you see the sections on recovery techniques and the contrasting symptoms, you might understand why the distinction is very important and why mis-labelling the issue is dangerous.

Here goes:

Loss of tail rotor control: You are not able to control the tail rotor pitch mechanism - it is a true emergency. This could be a stuck control (left pedal, right pedal, or centre) or it can be a total loss of thrust (broken drive shaft or gear box). It can occur on any helo, but is relatively rare. Part of the training on every helo.

Loss of tail rotor effectiveness (LTE): "Newly" discovered and named in the 80's after many accidents - in particular OH-58/B206 model, and is the cause of a significant percentage of those model's accidents. Although somewhat awkwardly named (as the tail rotor is still effectively working and must be providing thrust) LTE refers to what is thought to be an ingestion of main or tail rotor vorticey through the tail rotor which causes a rapid onset of yaw in the direction induced by torque that cannot be overcome by the application of full "power pedal". The yaw rotation is typically high and can build up quickly enough to fool most pilots into believing they have experienced a loss of tail rotor thrust.! It forces a loss of directional control while inside the normal envelope.

It is prevented by using very conservative flying techniques, and preparing recovery escape manoeuvres, or by re-designing the tail rotor to assure adequate thrust. The typical LTE involves an approach to a spot with moderate cross wind, and a loss of yaw control when the approach is terminated near the hover. Once entered, recovery is very difficult without descending, often ground contact is unavoidable.

Loss of Tail Rotor Authority (LTA): In this situation, the tail rotor does not produce enough thrust to counteract the torque/crosswind combination you require, your power pedal hits the stop, and around you go - though very gently when compared to LTE or total loss of thrust. LTA can occur on almost any helicopter when operated outside its normal envelope, typically when the rotor rpm is abused, or when very high torque is demanded. It is a symptom of mishandling the RRPM or Torque, not a separate cause.

It is prevented by pre planning weight/DA/power demands and carefully managing RRPM. Typical LTA events involve a takeoff or landing when the helicopter hits its engine topping, and the rotor rpm droops below the green arc, and subsequent Torque reaction overcoming the reduced tail rotor thrust even at max (maximum power pedal applied) causing a loss of yaw control. Recovery often can be made by lowering collective to recover rpm without significant descent, so that ground contact is often avoidable.

Apply that to this accident: it is not LTE!

[BlenderPilot]

I doubt LTE is really the cause of 1 out of 10 accidents that claim to be due to LTE.

Alleged LTE is more like LTA like the gentleman (HELMET FIRE) above just explained very well, Thank you.

In most cases that claim LTE, the tail rotor will just not have enough power to overcome MR torque, and that is not LTE, it's just a puny tail rotor.

I have done 360 degree pedal turns at a hover, in a Bell 407 with almost 35 knot winds, and the thing will just do what you want it to, but try that in a 206L, and that downwind turn will be so much fun.

Thank you HELMET FIRE for explaining LTE vs LTA

[rotorboater]

The typical LTE involves an approach to a spot with moderate cross wind, and a loss of yaw control when the approach is terminated near the hover. Once entered, recovery is very difficult without descending, often ground contact is unavoidable.

Explains a lot of what I have recently experienced, apart from just dropping the lever (which would have been V bad in my case) what is the best chance of getting out of it (obviously not getting into the situation n the 1st place is ideal!)

[Buitenzorg]

This is something I posted in a discussion on an R44 accident that was labelled LTE.

There is one phenomenon I’ve never seen addressed in these “LTE / LTA” accident investigations that most of us, certainly those who have spent time giving primary instruction are familiar with. It has no “official” name but my vote would be FOC, for

Freezing on the Controls.

From my own primary flight training efforts I recall (with cheeks burning) those occasions where despite my pushing that left pedal for all my 200 lbs. was worth the nose merrily kept trundling to the right – until the instructor took over, I lifted my trembling right leg off the pedal, and miraculously another 2 or 3 inches of pedal travel materialized.

I experienced an even more extreme example of this while giving instruction a few years later. My student was a slightly-built PPL rated gentleman in his 60s; I was in my 30s and outweighed him by over 50 lbs. Nevertheless, on several occasions after I called “I have the controls” I could not budge any of them – not the pedals, not the collective, not the cyclic – because of how tensed up he was. I terminated the lesson early because I was afraid we’d crash while wrestling for the controls; next morning he flew with another instructor who outweighed me by about 40 lbs. thanks to his weight-lifting hobby, and despite my warnings about this student he thought the pedals had jammed the first time he tried to take over.

These experiences have led me to believe that in a lot of cases where the accident report read “despite application of full left pedal” it should have read “despite the application of what the pilot believed to be full left pedal but was somewhat less than that”. Typical scenario: low-time and/or out-of-practice pilot, already somewhat tense, tail- or cross-wind hover, a little gust and the nose whips right, pilot really tenses up then pushes the left pedal, but against his tensed-up, immovable right leg, pilot now believes he has full pedal in and why doesn’t this spin stop? The remedy here would be enough clarity of mind to consciously lift the right foot off the pedal, but in a high-pressure and rapidly-changing situation, that’s an awful lot to expect from a relative neophyte. If the investigators asked “did you have your right foot on the floor?” and the pilot answered in the affirmative I’d have to believe he really had full left pedal in, but so far I’ve never seen this confirmed either way in accident reports.

As for my personal experience in type: in 250 hours in the R44 including hovering in and out of ground effect in any relative wind angle, I’ve never encountered the pedal stops. The tail rotor authority was always excellent. Please note that “twitchy in yaw” is not the same as “poor tail rotor authority”.

If the subjects of discussion are “Gazelle” and “fenestron stall” replace left with right and vice versa in the above.

Then recently I saw an in-cockpit video of a B206 accident, which rolled over after spinning out of control during taxi. A fraction of a second before ground contact the camera happened on the pilot's feet and the pedals were neutral.

All this led me to conclude that the first step in an LTE/LTA scenario should be: take your right foot off the pedal.

My roughly 1300 hours of flying B206L models at high-ish DA (up to 10,000 ft) showed that wahet we were told during training was correct: "Lead power application with up to full left pedal".

[ReverseFlight]

Thanks to helmet fire for the neat summaries.Just to clear up another term in my mind, what is a formal definition of "loss of tail rotor thrust" ? How is it related to LTE/LTA ?I know you said in one post "Loss of tail rotor thrust: Little spinning thing at the back stops spinning or falls off." Is that more like "loss of tail rotor" ?

[helmet fire]

Thanks Reverse,
I popped "loss of thrust" into the "loss of control" definition following Nick's lead to simplify the way these things are broken down into so many different names. If you lose thrust (ie tail rotor separation or drive shaft break), then you have lost control of the yaw system, and so that is why it was grouped in with stuck pedals, etc.

So the formal definition of Loss of Tail rotor Thrust: The tail rotor system ceases to produce thrust and therefore there is no longer any counter to torque reaction. This is a true emergency that, if in a hover, results in a rapid yaw against the power pedal, quickly achieving extreme rotation. As the vertical stabiliser achieves some measure of counter to torque reaction increasing with forward speed, the rate of yaw therefore dissipates with forward speed, and some types are able to maintain a semblance of a straight line and level flight at cruise speed even after a loss of tail rotor thrust! The loss of thrust may also be coupled with a significant shift in the CofG if associated with tail rotor system structural separation.

The recovery for loss of tail rotor thrust is entirely dependant upon the speed, hieght, and type of aircraft and is covered in the flight manual. Generally that would be to maintain forward flight at speed until near a suitable landing area, then conduct an engine off autorotative style approach. If you have not been able to maintain forward flight, you must remove torque by retarding the engine/s and conduct an autorotative style approach.

Loss of tail rotor thrust is not related to LTE/LTA in any way, as in both LTE and LTA, the tail rotor continues to produce thrust. Unfortunately, due to the high yaw rates experienced with LTE events, pilots can easily assume a loss of tail rotor thrust event instead.

In fact Bell recommended that pilots suffering an LTE event attempt to lower power to stop the yaw, then if not successful, roll the throttle off similarly to the reaction required following a loss of thrust incident. Following an Australian Army B206 LTE event in which the pilot experienced and LTE event at approx 50ft whilst terminating to a hover and carried out the Bell recommended checklist actions perfectly, a deeper analysis of the checklist requirements were undertaken and subsequently revised - at least in the Australian Army. Over adverse terrain, they now recommend accepting the yaw rate, using collective to ensure adequate ground separation (even if that means pulling power!) until sufficient height exists to lower the collective and fly away.

The trick then is to recognise an LTE event from LTA from a Loss of thrust event. Pulling more power in an LTA or loss of thrust event will be very unpleasant!

That is why so many people bang on about not calling these sorts of accidents LTE when they most clearly are not. Hope that helps.

[Aser]

Buitenzorg

You must be talking about this one:
YouTube - Helicopter crash accident on board camera no death

I really don't like just the feet tips on the pedals, hard to judge but seems that he's late in application.

[ReverseFlight]

Thanks again to Helmet Fire. I didn't know that the Aussie Army has this revised practice - trying to keep height at 50 ft AGL while spinning is extremely disorienting, let alone trying to distinguish LTT/LTE/LTA at the same time. I agree with Aser on the Van Nuys crash. The pilot had relatively little left pedal forward and was caught out badly. Reminds me of this one in Port Melbourne a couple of years ago. The event was caught on its gyro camera (which explains the stable picture) but the ship spun and descended some 1800 ft before recovering. I think it was caught downwind:YouTube - Helicopter looses control

[BlenderPilot]

Aser said . . . .

I really don't like just the feet tips on the pedals, hard to judge but seems that he's late in application.

Aser, I thing not only he might have been late, but he had a tail wind and made a pedal turn to the right, thus leaving the crosswind from the right, he had to stop the yaw rate with power applied to the tail rotor, if he had made it to the left he had the MR torque to help him stop the yaw, the story would have been different, if he had applied pedal promptly, he would have gotten in a tight spot, his mistake was making the pedal turn to the right and putting the wind on the critical side on a 206.

All ENG helicopters are heavy because of the equipment, (Usually the ENG equipment weighs about 400 pounds, but the 407 I flew with the Cineflex and HD transmision equipment, monitors had almost 700 pounds)

[FH1100 Pilot]

Blender Pilot said:

Aser, I thing not only he might have been late, but he had a tail wind and made a pedal turn to the right, thus leaving the crosswind from the right.

Nah, according to the "factual" NTSB report of the Van Nuys accident the wind was off the left, which means the crash should actually be titled: "1500-hour pilot loses control of perfectly good helicopter." But wait- how many of those 1500 hours were actually in 206's? I would guess not many.

The report states that they'd been up for 1.5 hours, which means that if he took off at 1545 local @ MGW and landed again at 1615 local he was 265 pounds or so *under* MGW. It was 30 degrees C, which is only 86F - not terribly hot and not terribly humid.

Turning a 206 from an into-the-wind hover to a left-crosswind hover should not be catastrophic, despite that some of you worrywarts erroneously believe the myth that it'll immediately going into an uncontrollable LTE spin with the wind off the left.

In a left-front crosswind (at sea level or so), a 206 becomes "twitchy" as the MR and TR vortices interact, but it remains eminently controllable and *still* requires less power to hover than with a right-crosswind. If a direct left-crosswind is strong enough to put the TR into VRS, then it is certainly strong enough to keep the fuselage from spinning due to weathercock stability. The only way you can get a 206 to snap to the right is to be below ETL with the wind off the right-rear, where the fin blanks off enough of the tail rotor to overwhelm it. Once that happens and the spin starts, look out! But as we all know, the TR is *not* stalled, and remains effective as long as you push and *hold* full left pedal.

The deal with a 206 is that you do actually have to depress the pedals to get the nose to do what you want. In the YouTube Van Nuys crash video, the pilot clearly is just sitting there, apparently as much of a passenger as the cameraman. Me, I would think that at his weight, just hovering into the wind is still going to require a considerable amount of left pedal. Mine does. Even executing a right pedal turn is going to involve having the left pedal displaced forward. Yet when we see the pilot's feet, the pedals are quite obviously close to neutral.

The pilot (who to his credit posted the accident footage on YouTube) admits that he screwed up. But at the same time he tries to deflect some of the blame by claiming that he got into "LTE." He did not. But it shows how quickly we are to invoke the boogieman of LTE in place of our own mistakes. If you don't have your left foot to the FLOOR in a 206, it's not LTE. And, at high altitudes it just might be plain ol' LTA (TR not big enough for MR torque).

Buitzenzorg got it exactly right in his post: Most "LTE" accidents probably result from the pilot not having put in full left pedal, and then freezing on the controls when things start to get out of hand and stuff starts happening faster than your brain can process. We all like to *THINK* we're Yeager and that we'll always handle ourselves and the helicopter with cool, calm professionalism. Sadly, the truth is that we are not and do not. Not always. In the case of Van Nuys, it was just a matter of a relatively inexperienced 206 pilot who was performing at a less-than-optimal level that day. Hey, sh*t happens.

[BlenderPilot]

FH1100 . . . .

Yes when he is doing his hover taxi to the ramp, the wind is from the left, but when he turned to the right, the wind came from the right, and that's is why it spun so fast and was difficult to control . . . . . . Difficult, though not impossible is a fact.

[FH1100 Pilot]

Blender, by the way it spins in the video, my first thought was that he absolutely had a tailwind too. However, not to be argumentative, but according to the NTSB the wind at VNY was 140/10. The pilot made his approach parallel to runway 16 to the parking area at the south end of the field, which would give him basically a headwind. The dollies were oriented facing perpendicular to runway 16/34 on a rough heading of 250. Thus, 250 minus 140 is 110, so as he made his right pedal turn he transitioned from a headwind to a left-crosswind, or maybe slightly left-rear. Still, should have been no problem for a 206BIII at that density altitude.

Unless I'm missing something...?

[GeorgeMandes]

Assuming we are talking about LTE on approach, one is highly unlikely to experience loss of control due to lack of sufficient anti-torque available by following the mountain procedures taught by the Canadian Helicopters mountain school in Penticton. Before your touch down attempt, you have made a proper recce, including making a loaded disk approach with an over shoot above ETL, where you assessed torque/temp/NG and pedal reserve, and as much as possible crabbed the ship into the wind. If you didn't have sufficient power or pedal margin before falling below ETL, you would abandon that approach, under those conditions, and never have slowed below ETL. Conversely, if your approach is with an unloaded disk, to a spot with an unknown wind direction and velocity, and unknown up or down flowing air, you are about to determine at that moment whether you have sufficient power and pedal to make a safe landing. If you think that a previous review of the performance charts will tell you whether you have the necessary performance, you are not taking into consideration the effect of up and down flowing air on your ship.

[CarryOnCopter]

As that well known helicopter pilot Clint Eastwood said,

"a man's got to know his limitations"