Loss of Tail Rotor Effectiveness in Helicopters
Vložit
- čas přidán 27. 07. 2018
- Welcome back to Helicopter Lessons in 10 Minutes or Less!
Check out my ebook covering this and more! Get your copy on iBooks: itunes.apple.com/us/book/id144...
or on Kobo for Android, Windows and Desktop users: www.kobo.com/us/en/ebook/heli...
Want to buy me a beer or coffee as a thanks? www.paypal.com/cgi-bin/webscr...
Once again, I'm Jacob and in this video we're talking about Loss of Tail Rotor Effectiveness (LTE). Beginner pilots might have heard stories of other pilots "getting into LTE", having an uncontrolled spin, and almost losing control of the helicopter. Or they were forced to fly out of it / do a go-around. It can be quite a pucker factor and so it is important to understand what LTE is and where it comes from so you can prevent getting into these situations in the first place.
LTE is the uncommanded, rapid yaw rate that does not subside of its own accord and which, if not corrected for, can result in loss of helicopter control. This yaw rate is generally to the right in counterclockwise rotor systems and to the left or clockwise rotating systems. This is not related to a break in drive system and is not a stall in the tail rotor. Some commonly say it is because the tail rotor stalls but this is a misconception. The tail rotor trust is merely insufficient, but not stalling. LTE is a wind issue which occurs when operating at airspeeds less than effective translational lift.
Flight and wind tunnel testing has identified a few relative wind regions that can cause LTE. The first is generally from the 4 o'clock to 8 o'clock position and is known as weathercock stability. When winds impact the fuselage from this region the helicopter tends to pivot around the mast towards the wind or "weathervane" into the wind. Unless existing pedal and put is made, and on command it turned to the right or left will develop. Attempting to have her in this region can result in excess of pilot workload. The next region occurs when winds impact the tail rotor between the 8 o'clock and 11 o'clock positions. This creates a tail rotor vortex rings state. This is just like main rotor vortex ring state that I discussed in a previous video (Vortex Ring State / Settling with Power Part 1 • Vortex Ring State / Se... ) only hear it happens to the tail rotor. Your tail rotor is essentially settling with power. The tail rotor is meant to counter the torque effect of the main rotor by pushing the tail clockwise or to the right. But when enough of a left crosswind occurs, this creates the vortex ring state laterally in the tail rotor which reduces the effectiveness of the tail rotor's ability to counteract the torque affect.
Wind velocity is from the 9 o'clock to 11 o'clock regions can cause LTE due to the results of main rotor disk vortex/interference. This occurs when the winds literally push the wingtip vortices of the main rotor into the tail rotor which causes the tail rotor to operate in turbulent air. This causes angle of attack fluctuations and an eventual, sudden and rapid yaw. Helicopters are extremely susceptible to this type of LTE when operating at an Out of Ground Effect (OGE) hover with a left, quartering headwind. The last region generally doesn't get much coverage but is still very much a part of LTE. This occurs between the two and 4 o'clock positions when the right crosswind impacts the tail rotor and causes an Angle of Attack (AOA) reduction. The crosswind increases induced flow of the tail rotor which results in a decrease in thrust. Aside from just hovering in this region, this one typically sneaks up on pilots who are hover taxiing in a tailwind and start a right pedal turn to "hook it into parking." What happens is the aircraft begins turning to the right, it's this LTE region, and the nose does not stop turning to the right.
Attention must be paid to these regions because they can build on each other. Main rotor disk interference can start the right turn that puts you in tail rotor vortex ring state to then a weathercock stability state. If Loss of Tail Rotor Effectiveness is experienced, the best recovery technique is to apply forward cyclic while applying as much pedal inputs as possible to maintain heading control. If altitude permits, collective reduction can aid in reducing the yaw rate.
That wraps up LTE. It's the uncommanded yaw that does not subside on its own accord and is a result of operating at airspeeds less than ETL with certain wind conditions. It is not a mechanical break in drive system components or a stall condition in the tail rotor. It results in high pilot workload and potential loss of aircraft control.
Thanks for watching! Don't forget to hit like and subscribe. As always, safe flying!
If you want to further your professional helicopter education with advanced helicopter concepts, I'd recommend reading Cyclic and Collective, by Shawn Coyle - amzn.to/2ifQGLx
So, basically you're only "safe" with the wind coming in the narrow angle from 11 - 2 o'clock.
That's... comforting....
Your great educational videos are starting to make my rethink my decision to learn to fly these whirlybirds of death. (No, not really;)
Daniel Rehn. I'm not saying that's the only place you are safe. The regions of LTE are most dangerous when you're at high power settings without much power available left and you don't have a plan. There's nothing saying you can't operate in any of these regions. I've found myself in many instances where I had to operate in an LTE susceptible region and just had to modify my approach, heading, abort criteria, etc. Just have a plan if you know you may enter a dangerous situation. Thanks for the feedback.
@@helicopterlessonsin10minut10 Sorry late entry. Love the video. Im a layman so excuse me. What would be a good plan to have in these susceptible regions? I envision spinning wildly OOC until gravity finishes the job.
@@UploaderNine 😂
@@UploaderNine recovery is accomplished by getting the aircraft operating in clear air again. (or at least better than the air that it was operating in). So when we say "have a plan" usually this means a plan to fly out of an OGE hover and away from obstacles so that airspeed can be gained and thus, operate in clean air.
@@helicopterlessonsin10minut10hence they often happen in a hover with low power being used. Of all the types of LTE main rotor disk interference, weather cock and tail rotor vortex ring state I must say.....
.... Tail rotor vortex ring state is the most fun. 😃 I mean I am just saying. Nothing like a gust of wind from the flowing through the tail back into the main rotor then back into the tail in such a continuous cycle to give you all this unexpected yaw to deal with. 😂 just set that thing down with all the wind on the left side to prove after 100 hours or whatever you can just set the thing down straight and level no matter what the weather is like.
Great explanation of LTE, actually the most basic and understandable one I've seen!
Really struggled with this on my last lesson. Great explanation
Outstanding Job Jacob!! I retired in 1993. Enjoying renewing skills! My nephew retires this month. Remember going to his graduation with his Dad (My Twin brother) and getting to visit with one of my CFI’s. He advised Adam was a natural and a fantastic pilot. Adam became a CFI and loved his career in the Military - serving several overseas tours. Thank you so very much for your videos!
Just started flight school and your page has been so helpful ! I just want to soak up as much knowledge as I can to become a safe pilot . Thanks man !
Very very good! I knew about 3 of them, but I didn't know about the AOA reduction at the 2-4 o'clock position. I am still in the process of obtaining my Helicopter Private pilots license, and all of your videos are very helpful! Good job Jacob!
This may be my favorite intro video so far!
Jacob I'm an MD500 pilot and I'm learning a lot from your lectures Thank you
really enjoying the lessons mate! explains alot from my recent training flights! exam anyday now -Thanks Jacob
Great explanation. Thanks a lot. I always try to read or watch again and again about LTE before i commence my any tour where the longlining is involved. I really appreciate the explanation.
Great video lesson. Thank you sir.
Finishing up my commercial rating and very rusty. Been to many schools and watched probably most of the online inst videos. These are by far the best. So simply yet thoroughly described. Clearly communicated and not the dull, bore you to sleep tone. Your army students are very fortunate.
Could you do a follow up to this video about LTE Recovery? I read a lot about LTE, one of the more common causes of crash, but one of the least discussed about corrective action
I really appreciate all these videos, good work.
I think the one dislike is probably a fixed wing pilot. lol
Lolol
Exactly😂
I really like the thoroughness of your videos. I am always skeptical when I watch this type of video and tend to try to poke holes in the theory. But I must confess that I have learned things from your videos that I did not learn in Army flight training.
I am not sure of your background but I suspect you are of the AH-64-D/E persuasion. Most of my experience was on the AH-64A. I also spent time in the utility community before coming to the light. I was a crew chief on the UH-60s and later was a pilot/MTP on UH-1Hs, and then finally I was a pilot and MTP/MTFE on the AH-64A Apache.
I also worked for Bell Helicopter for 30 years prior to my retirement last year. I used to present a Helicopter 101 class to my colleagues. It was always well received.
You do an excellent job explaining the Fundamentals of Flight...keep up the good work!
Love your videos dude, been such a help for me!
Excellence in your vids may have saved a pilots life unbeknow to the pilot.
These vids are precision & true.
Thanks
Thank you great videos and explanation !
I’m a low hour pilot learning in an R22 and I had my first experience with this solo last week. Specifically the last one with the AOA Reduction, in almost the same scenario you mentioned about being finished and taxing back. Only I was going to make a left pedal turn in to a tail wind. Before I was able to start the turn a really big gust hit the right side of the helicopter and caused what you described. Luckily I was able to fly out of it but I bout pooped for sure.
A Robinson will never experience lte they have great tail rotor authority
I don't know much about helicopters but like them a lot. I understand LTE a lot more now. Thanks :). I watch that yellow pilot a lot. I got maybe an hour in a helicopter now and a ton of fixed-wing :). I just subscribed to your channel.
Way cool, in my opinion, one of the most profoundly inspirational and thrilling experiences to be had at this time and on this planet . . . is flying a helicopter. !
wow.
Great channel mate!
I want to build a helicopter and now you just told me that after building it I I still have a lot to learn to avoid death. WoW! Anyway, I'm still gonna build it. I will go with the rigid rotar system.
NOW I get it! Thanks!
Great stuff here, thanks.
Good vídeo 👍🏾🚁
Was landing in Honduras in a UH-1 and due to NOTAMS we were stuck with less than favorable conditions (direction of approach) with a high DA, critical forward CG, and a full load. As I finalized my approach to IGE hover I began my turn to get to the pad I ended up with an AOA-reducing quartering tailwind combined with weather vaning and the nose just kept rotating right. I quickly ran out of pedal, so down and forward onto the pad was the order of the day.
THANKS FOR A NICE EXPLANATION ... THE AOA REDUCTION CASE IS THOUGH HEARD FOR THE FIRST TIME ... WILL YOU PLS ELABORATE ON THAT A LITTLE ??? THANKS
Thanks very good explanation
Jacob n. 1 for clarity and depth of explanation. Very understandable and to the point. 👍🏻 as usual
That greatly shows the advantage of the Notar system.
Love your lessons! Keep em coming
Thank for these
I work as rural paramedic...90 mins by road to a very basic hospital ...our service uses an auto-launched Bell 412SP
(So based on the dispatcher's info they're usually on the way before we are)
30 mins flight time to the front door a full service hospital
But all our LZ's are uncontrolled
And occasionally...they just won't land where we want them to
So we end up loading the patient and chasing them around looking for a better LZ
Getting everyone a tad frustrated
Getting some insight into the physics of the aircraft...kinda helps
Great to hear! I’m working on a “Confined Area Landings” that should add some clarity to why certain approaches and LZ’s are decided upon. That sounds like the type of insight you’re looking for. Ultimately, your pilots should be able to provide insight as well. I always explain the decisions I make for maneuvers if people are interested to learn.
You rock. Thanks.
Hi Jacob, as usual great video! if you have time - could you please do a video on tail rotor aero D. Thanks a million.
Angelo Manuel Picoto. Thanks. Are you asking about tail rotor aerodynamics or tail rotor design?
Helicopter Lessons In 10 Minutes or Less , Apologies Jacob , an elaboration on the tail rotor aero D when the tail rotor experiences wind from all these different regions( induced flow, RAF , how the wind changes AOA etc) and maybe get into the differences between LTA and LTE? Thank you Jacob !
I'll see what I can do. Thanks for the feedback!
Another awesome vid Jacob...great job,waiting for video on helicopter performance and stability..! Is it down the line...?
Ab797. Thanks! I've got quite a large list of topics and that one is in there. Stay tuned.
Will be waiting for the same...awesome work !!
It's not "settling under power" it's "settling with insufficient power". The US has had one helicopter powerful enough to get out of VRS by applying torque/power to get out of it. That would be the CH-54 Tarhe, aka the "skycrane". Not even the mighty Chinook, which has a shit-ton of torque, can get our of VRS like the CH-54 can. The 47 is quite easy to recover from VRS however, you can usually just use pedals to get out of it. Also, the 47 doesn't have LTE since it has dual tandem rotors.. :) I am simply mentioning settling with insufficient power, not LTE.
Worthy of note is that the Apache has a special tail rotor, with dual blades scissoring on the tail.
Can you make a video about how does a helicopter take a turn?
Merci beaucoup !
thank you sir
Does this affect NOTAR helicopters like the MD902 Explorer? Excellent videos, you're students should be very proud of you. Top instructor
Great question. I’ll have to look that one up. At first thought, it doesn’t seem as though it would have as much, or any, effect in some cases.
It shouldn't because NOTAR uses a nozzle at the end of the tailboom for anti-torque control. Since there is no way to disturb the airflow over the tail rotor it shouldn't happen.
@@helicopterlessonsin10minut10 I’m thinking of electric tail rotors, like Bell’s EDAT (Electrically Distributed Ant-Torque). Could this significantly reduce the problems you have outlined?
Hi,could you make a video of the delta 3 hinge of the tail rotor?
Thank you! Very clear. Anyway, only wind coming from 11H to 2H is ok, then !
Romain Billion-Grand. Winds from other directions are certainly flyable. But you just need to be on the lookout for these areas when flying less than ETL and especially at high power settings.
Would you please explain the 'angle of attack', what is it, which part of the vehicle is affected?
Vortex Ring State is NOT Settling with Power.
He goes into that. czcams.com/video/P30SyNldEy4/video.html
@@GarranGossage And he is dead wrong. czcams.com/video/ehV9vLnBICE/video.html&ab_channel=PilotYellow
Sir, I believe you may be mistaken at time stamp 4:16. You state TR anti-torque as being "clockwise" then follow with "to the right". I believe it is "to the right" (in this example) but then that would make the required TR anti-torque to push counterclockwise. With that said your helo instruction series is excellent and as a new student I am in no position to criticize, however being that the subject matter is "life & death important" and can be incredibly confusing, I feel accuracy is of the utmost concern. I hope you accept my apologies. Thank you.
Thanks Jacob #HLI10OL #SkyBaum
Thank you again. Just to be sure are you saying that the proper corrective procedure is immediate application of forward cyclic and simultaneous application in increased pedal input to counteract the adverse yaw? And is that true for each of the four wind cases you’ve illustrated without regarded which one or the direction of the problematic wind? Also, since this tends to be a problem when hover-taxiing would a little upward pressure on the collective sometimes necessary to keep the main rotor sufficiently clear of the runway during or taxiway surface during its forward ark? Maybe my fixed wing mindset had me confused again. One more question: Are the intro shots from Fort Rucker??
William Eudy. Great questions! Yes, if the nose begins to yaw and it's suspected that aircraft control could be lost (this is the most important consideration) the corrective procedure is to apply as much pedal as possible to gain/maintain aircraft control while flying out of it. This is just another reason why it's so important to understand wind direction when maneuvering helicopters, even at a hover. Keep in mind that not all cases are the same. If the helicopter is light weight on a cold day you may have quite a large power margin and hovering in the weathercock stability may just be uncomfortable but not necessarily a condition where you could lose control. To address your other question, hover taxiing at a slightly higher altitude could potentially give you more altitude if you had to fly out of LTE but it also increases the required left pedal to maintain heading. So once again there is a trade off that the pilot must consider and tailor movements to the specific situation. Lastly, I have video intros from all over the world and yes some are from Fort Rucker. I hope this helps answer your questions.
@@helicopterlessonsin10minut10 There is no risk of the tail rotor stalling when you apply more pedal?
This is why i like kamov helicopters.
Awesome explanation of LTE! My question is, are there certain wind speeds at higher or lesser MPH that cause the LTE's or does that not matter of the speed of any given wind?
Generally speaking, the stronger the winds and the more power you have applied, the more severe/pronounced you can expect these effects to be. Great question!
@@helicopterlessonsin10minut10 Thankyou so much for the explanation of LTE. I look forward to more vides🚁🚁🚁🚁🚁🚁
It would be very cool if you started your own Helicopter Ground School
Not that frequent , in 35 years of duty works, like rescue, external load operations or long line, I may have done 2 or 3 LTE compared to hundreds of Vortex Ring State or Settling with Power.. BTW, Bell machines seem to be more affected by this. May be because of the clockwise choice and a different pull/push action of the tail rotor itself with different blades size.
I don't know anything about helicopters or flying at all but I'm going to make some guesses. If you lose your tail rotor you must assume it doesn't exist basically. I assume you can cut all power to it. If you can get the main rotor to gain rotational momentum enough through negative angles or whatever you call it to auto rotate you might be able to descend and then gain enough lift by changing to a positive angle closer to the ground. If you are high enough this should be easier and then again if you are low the impact forces will be less. I've never actually been in a helicopter I'm just theorising.
Hello Jacob. I showed the LTE video and printed pages for this LTE presentation during a stage check as I am doing my commercial add-on. At the place I train the main instructor had never heard of AOA reduction and in essence said probably not a good idea to raise this with the examiner as it is not in the helicopter flying handbook. Other than your presentation, where else can I find more details on this AOA reduction LTE concept to support your findings? I wondered if this is a more advanced training concept you receive with your military flight training but is not very common in General Aviation. Thanks.
It’s found in Ch. 6 of the Naval Introduction to Helicopter Aerodynamics manual outlining the differences between Loss of Tail Rotor Effectiveness and Loss of Tail Rotor Authority. Page 6-12 has a whole paragraph on it.
“AOA Reduction (060-120 degrees)
In a right crossword, the relative wind shifts toward a tail rotor blades’ chordline because of effectively increased induced velocity (Figure 6-11). The shifted relative wind impacts at a lower AOA, which develops lower lift and results in less thrust. The pilot will automatically compensate by adding more left pedal, but in some cases can reach pedal travel limits before adequate thrust can be generated.”
@@helicopterlessonsin10minut10
Thank you Jacob….excellent information and I will pass it along.
Can you make a video about stuff you need to from a pilot stand view, like know what beacon mean what, numbers on a runway for a example number 28 why is that there, Visual flight,instrumental flight. You get where I’m going lol
D'Narius Conner. Great question. Currently the channel is focused on aerodynamics but I would like to eventually expand into more topics later. Until then, here are some other videos that should answer your questions.
Runway numbers (czcams.com/video/lzx5j1C984M/video.html)
VFR/IFR flight (czcams.com/video/QTUvLCNPei8/video.html)
Thanks for the comment. I hope this helps.
Thanks I’m actually taking my sift in the next couple weeks hope for the best. Your videos been a huge help on understanding everything!
LTE is the lack of power on the tail to overcome the push from the weather, correct? I'm new on this that what I understand
LTE is caused by winds on the aircraft during high power settings. It’s not necessarily a lack of power to the tail rotor.
Wow seems like a lot of options for getting in to LTE. What kind of wind speed would be problematic? Seems almost impossible to avoid all of these angles relative to the wind when manoeuvring around an airport.
HappyCamper. LTE can occur with even just a few knots of wind depending on certain helicopters. These regions are not necessarily completely uncontrollable or unrecoverable wind azimuths as much as flight profiles to be aware of, especially when power limited. The only way to completely avoid these regions altogether would be to operate above ETL or with the nose into the wind while hovering. I hope this helps.
The reason why 'copters are a risky firm of flying. Give me two wings every time!
it bothers me he didnt put the wind angles to the center of the helicopter on the bottom two. Makes me think he did it on purpose? or am i just overthinking it? Let me know please its bothering me greatly and confusing me
I’m think of electric tail rotors, like Bell’s EDAT (Electrically Distributed Ant-Torque). Could this significantly reduce the problems you have outlined?
Even in these cases, the tail rotor could be affected by the wind gusts.
What kind of wind speeds are we talking that can have these effects?
It depends on aircraft but it’s generally most prevalent when you’re operating right at max torque available or OGE.
Are you an apache pilot or you take this intros on internet? Good videos btw you have absolutely no dislikes that's huge ! :)
Pyrodlt. Yes I'm an Apache Instructor pilot. Glad you're enjoying the videos!
Oh that's amazing! I'm willing to become a Tiger pilot in France your videos helps me a lot, thanks !
where can i find a reference for the AOA reduction area in any FAA books?
electric69irl. I've yet to see it published in anything FAA at this point. But it's mentioned in a few flight safety articles as well as explained in depth in the Navy's Introduction to Helicopter Aerodynamics (amzn.to/2K3TN1d).
There is a newer version of the mentioned manual.
Yessir
Is there any given situation of "main rotor disc interferance" at the 11 O clock----3 O clock positions at all???
Nothing outlined for counter clockwise rotating rotor systems. It’s generally a safe place to put the winds. But keep in mind all of this is reversed for clockwise rotating rotor systems.
@@helicopterlessonsin10minut10 Okie dokie. . . .gotchya. Trying to learn all i can fore im even able to go to helo flight school, if i can. Ive had reading & studying all about helicopters all thru Jr. High & High school back in the day & still trying to learn even more. Flying helos has always been my dream. . . . .dunno if it ever happen or not!!! Fly safe!
Can you do a video on blowback please?
flying helicopters should never be underestimated! having successfully done the licence, doesnt mean you can fly a helicopter. the real challenges will hit you in your coming years. thanks for this excellent video, which should keep you alert at any time, cause LTE might happen during your next flight.
Jacob thank you! Your videos will probably never have as many views as a random wanabe pop star, bud it can save life ;)
In essence: Wind is an issue.
Mostly at high power setting and strong winds
Unless you’re flying a French or Russian helo, then it’s swapped L/R
Apache is damn sexy, can't get enough of it!
video starts at 1:01
แนวคิดเขาทำได้คุณอย่าลืมว่าเรามีชุดควบคุมทดกำลังให้เท่ากันทั้ง 2 ข้างด้วยระบบคอมพิวเตอร์มันไม่ใช่แค่ส่งกำลังจากเครื่องยนต์อย่างเดียว
So takeaway is don’t fly helicopter in wind without your insurance paid up.
pucker factor ahaha
what's your analysis of this mishap ( czcams.com/video/mIW7JZbGf0Y/video.html ) due to LTE ???
or, just accept that if it happens at low airspeed and low altitude....you will probably break the bird.....at lest that what they taught me at mother rucker...granted, at some flight envelopes, you can save the bird without too much bending.
Settling with power and VRS are 2 different conditions and shouldn't be used interchangeably
A U T O
R O T A T E
A U T O
R O T A T E
I wish Ara zobayan has watched this video before he flew that Sunday
LTE had nothing to do with that incident. It was a controlled flight into terrain. It was reasonable to take of from John Wayne, but he should of called the flight at KVNY and had passengers take ground transport from there. He got confused in IMC and lacked experience though he had certification.
Stop saying SWP when you're talking about VRS. An inability to counteract momentum and ineffective aerofoils due to air movement are to entirely separate conditions. Stop conflating them.