.

Thank you

Frank also incorporates some Delta-3 angle in the main rotor.
Now I wonder if that offset pitch location is how he accomplishes it

Of course 2 blade tail rotors have Delta-3 to retain the plane of rotation and prevent flapping into the boom
but as far as I know he is the only one who does it on the main rotor as well.

Through the years my suspicious mind has pondered whether his unique Delta-3 combined with his unique coning hinges can create an unknown gremlin in certain conditions

I have often wished some researcher would mount the R system on a test stand and put it through every conceivable
motion to see if the blades would divert from their proper plane of rotation (not including Zero-G of course)

It would not require a lot of funding and if they used measuring instruments on all 3 hinge points could determine
if the coning hinges sometimes pivot beyond the design intentions.

the discussion is about R44s.

Robbiee, that will have been a poor attempt to simulate a TR failure not unintentional yaw - this is only safely and realistically done in a simulator.

That's not correct. The video is quite hard to follow given the English-as-second-language challenges. The paper suffers less from that. You are encouraged to read the paper at the link posted earlier in the thread.

The intent of his research was to show that LTE as many pilots currently understand it is, if not a myth, substantially misunderstood, and that under all conditions associated with certified designs sufficient tail rotor thrust can be developed to stop the rotation. While reducing torque is one way to assist the resolution of unanticipated yaw, it is not always an option available depending upon phase of flight, nor necessarily the best option. Also, one should not confuse responses to a stuck pedal or tail rotor failure with that suitable for unanticipated yaw.

Modeling and simulation of the design have been performed. The original GTRI modelling effort is documented here:

https://smartech.gatech.edu/handle/1853/52548

It's quite a large document. Chapter 5 is where the meat is, starting on PDF page 118 (not document page number).

There is also this, however I have not paid the $30 to download it and see if it is any good. It is quite recent:

https://vtol.org/store/product/mast-...tems-12593.cfm

Thank you very much ..... this is exactly what I was looking for (wishing for) .... lots of reading so off I go to do it .... I may even pay the $30 and download the second one ...... will report back if I do.

Ok then, what is LTE?

It’s a phenomenon where an aircraft tries to punish the pilot for demonstrating his superior skills and inferior footwork.

Hmm, already knew that.

,...but thanks for saving me from that excruciatingly long paper!

But what would you have done for full left pedal?

Ha ha, that's awesome, love it! :ok:

To answer your quesiton, Robbiee, per the paper, what everyone likes to call LTE is instead "unanticipated yaw", because at no point does the tail rotor demonstrate any ineffectiveness. It could be called "loss of pilot foot control" ;) Per the paper, if the pilot lets significant yaw rates develop it can take quite a bit of time to get it stopped, but assuming full pedal deflection it will stop. If the pilot does everything else necessary, such as maintaining altitude and position, it should stop without the helicopter doing anything else untoward. You really should read the paper.

Edited to add: unanticipated yaw (incorrectly termed "LTE") is not the same as stuck pedal is not the same as tail rotor failure.

There is also LTA - loss of tail rotor authority where you reach the pedal stop and still the unintended yaw continues. It is why some aircraft have a reducing crosswind limit with increasing density altitude.

As an example, the Wessex MAUM was 13,600Lbs but in Cyprus at the top of Troodos, the PA was 6,500 and the OAT often in excess of 20 deg C which could leave the DA in excess of 9000'.

The yaw envelope of the venerable old girl narrowed markedly up there and we were limited to 12,500 lbs for landing at the top and coming to a hover wasn't an option.

I took a visiting (Ex-84 Sqn) pilot up there and let him fly the approach as he had done it before when he had been in theatre but I reminded him about the yaw problem we might encounter.

We lost too much speed on short finals and reached the left pedal stop and started to yaw right - the only solution was to turn right, lower the collective slightly and try to get airspeed on. I succeeded but it taught me a lot about yaw control!

Hmm, this sounds like the whole SWP thing all over again. You guys just don't like how the FAA names things.


By the way, if you understand what causes LTE, then you should be anticipating it. Therefore, the only "unanticipated" yaw should be from stuck pedal, loss of tailrotor thrust, or engine failure.

Had that happen in training once too. It was at the end of the flight and we had just gotten back to our home airport. Assuming the training was over I was nice and relaxed (guard down) as I brought it to the pad. Just as I got the nose straight and was about to set it down, BAMN! the nose snapped left! I jammed in the right pedal, the yaw stopped (about 90° later) I raised the collective, we hit the ground, and had a good laugh.

Ah, how I miss surprise throttle chops..

,...'course if you're referring to stuck pedal, than well, I've only had about five minutes of stuck pedal training (none of it in a hover) so I'd probably crash before figuring out the correct course of action. :(

Operating at 3,000 metres over mountainous terrain immediately puts you into a corner of the operating envelope where you had better have some options up your sleeve. Power margins, turbulence, down draught velocity, escape routes, visibility and control issues are all great things to cover on the pre-flight briefing. It's a very unforgiving environment when things don't go to plan, and a great place to have experience on your side.

No joke. The highest I've flown my trusty 44 is not quite 2000M, and I treated her like a delicate flower up there. Not at all like the tough old bird she is nearer to sea level. 3000M op's has got to be something else entirely.

I think you should learn a little bit more about helicopters before you make sweeping statements like that.

You could start by reading that 'excruciatingly long paper' !

If its anything like that video, its just going to put me to sleep.

well it sort of depends if you want to learn about something that might save your life or not!

Well (as with SWP) what the FAA taught me about LTE has kept me alive for almost twenty years.

,...but if you think you've discovered something new in that article, please, feel free to share with the group.

A summary would be - LTE doesn't really exist and most encounters were caused by pilots being reluctant to put in sufficient pedal to stop the rotation. There are yaw disturbances caused by the interaction of the MR downwash and other turbulent flows.

There, saved you hours of excruciating reading.....

perhaps because the type of flying you are doing isn't very demanding.......

As a check of understanding Robbiee - imagine you are operating at MAUM at high density altitude into a landing site where you can't approach into wind, only crosswind - which way do you take the crosswind, from the left or the right?

Well, I don't know who MAUM is, but having done crosswind approaches from both sides, I guess I'd just pick the side that has the best view of the chicks on the beach.

Hmm, so again, no new information, just a desire to no longer call it LTE. Yep, that sounds like its worth fifteen pages.

Hate to say it, Robbiee, you and I are usually on the side of goodness and light, but in this case I'm in total agreement with crab!

Open your mind, read the damn article, and get with the program. You have already passed your oral exam, no need to parrot the FAA textbooks. And do a damn Google search for "MAUM" as it relates to flying. Certainly those on the wrong side of the pond ;) have some differences in jargon, but you are an intelligent guy (seriously, you are, you can't fool us), you really don't need to be spoon-fed this stuff, come on!

Robbiee - Maximum All Up Mass FFS...perhaps you prefer MTOW?

The flippancy of your answer leads me to believe you really don't understand the importance of the question in regard to TR performance and yaw control.

aa777888 - :ok:

I suppose not. Guess I'm just doomed to spin endlessly. :(

and if you bothered to read the paper, you would know that doesn't happen either.

It would be quite nice once in a while if the seasoned professional pilots (of which there are a large number on here) were actually listened to by the less experienced when knowledge is being imparted. It's for your good not ours as we have 'mostly' learned from our mistakes and close calls.

Sorry, oh wise one, your great secret will just have to remain hidden amongst those fifteen sacred pages.

Hopefully you are less flippant with the owners of those 22's you have to haggle down to hire. At least there is only 1 other seat if ego runs out.

Well, those 22 owners never tried to convince me that the textbook was wrong while keeping their great truth buried in a book so dull that it makes my VCR owners manual seem like a Penthouse Forum.

,...but please, more melodramatic responses, I really need the distraction from the insanity that is playing out in my neck of the woods these days. :bored:

Perhaps that paper could be a timely distraction. You don't have to agree with or believe in the findings, but at least the exposure to the perspective that the paper takes on the 'phenomenon' of LTE will broaden your knowledge and approach to flying challenges in the future. It won't do you any harm, but there's a good chance some thought-provoking will entertain the aviator in you.

Robbie,

You have dug yourself a rather large hole and worse than that have fallen head first in it. Maybe it’s time to get off your high horse and actually take on board some of the proven advice that has been offered to you in recent posts... as a pilot show some form of responsibility!

"Proven advice"? What?,...you mean, "read our awesome fifteen page dissertation on the great LTE secret",...?

Nah, I think I'll just stay on my high horse,...I can check out a lot of cleavage from up here! :ok:

Nice attitude, perhaps you should consider another forum since there is nothing professional about your approach to flying it seems.

Such melodrama and smugness,...you must be a delight at the pub. :rolleyes:

but my smugness and melodrama has kept me alive and flying safely for 38 years where as your gash attitude is far more likely to lead you into problems:)

I'm sure they love you at the flying club.................

Hmm, preferring knowledge I gained from a textbook (knowledge which has kept me from crashing for almost twenty years) over some great secret hidden in some abstract paper I found on the internet, is considered "gash",...?

Know what?,...next beer is on me. :}

Great reference paper aa77788.

I think my LTE/unanticipated yaw experience can firmly be placed in the poor aircraft management category as opposed to lack of inherent tail rotor authority. In strong laminar wind I made a lazy clearing turn with right pedal turn and presented the tail rotor directly into wind, with entirely predictable results. Whether there would have been enough authority to reverse the problem is moot, as the first 90 degrees were through so fast, it was clear that a continued turn back into wind was the easiest solution.

The moral of the story was be aware of aircraft limitations and don’t fly daft. I say aircraft limitations because many larger aircraft would have tolerated the same winds without the sudden snap. TR authority is, necessarily related to the aircraft‘s mass and the R22 is a light helicopter.

There is a very good video of an R44 down under that gets into all sorts of trouble due to poor management which was attributed to LTE, but isn't really. From a dozy lack of awareness that the aircraft was running out of power, to pretty much losing control took less than 10 seconds. And under stress, the pilot fought the aircraft almost into the sea, before it flew itself out of what had become vortex ring state. The one thing the pilot didn't do was lower the collective, roll on and get airspeed. Lucky. Very, very lucky.

I can't upload my versions of it. But maybe someone has another format (I have non-accepted MPEG & FLV).