Whip it

[Witch]

OK Robbie Rangers, we went flying up yo Mary's Peak this morning. The flight up there was uneventful. After making two orbits, we find a spot to land. Approach is a little high and fast-normal for me-and as luck would have it, I was able to set-er down on the slight slope. After a couple of pictures-and angry hikers approaching us-we lift off. While doing so, the tail kicks to the right and I have to give left pedal. Departure was ok.

 

We then go to an abandoned landing. I did two approaches that were way high and fast. Somehow things look different with a few thousand board-feet of Doug fir under you. Anyhow, I get to the landing and the tail kicks to the right again. I'm fighting it with left pedal. Nick freaks out, but we land OK. After flying through the woods, and to our suprise flying about 100 feet past a gravel pit on the top of the mountain at 70 kts, we head for other places to land.

 

Once again upon landing, that dang tail kicks to the right again. I again catch it, but wonder what it is that I'm doing to cause this phenominon. Any ideas? Obviously, I think the left pedal input may not be enough to prevent a kick to the right, but other than that, I have no idea.

 

Oh, I took my GPS and it recorded the flight path. Here's the path to Mary's peak.

Here it is.

 

Later.

[joker]

Witch,

 

Confirm this for me: The tail kicks to right hand side of heli and nose left....OR...the nose goes right with tail left?

 

If you were using the 'left' pedal to compensate then it would suggest the latter...nose right, tail left.

 

What was temperature and QNH. If it is Mary's Peak I'm thinking of, the altitude is about 4000' ASL? Two men inside weighing how much?...how much fuel did you have? Where was the wind in each case of yaw kick?

 

Was it a 'kick' and then back to normal, or did it stay like that until corrected with pedal?

 

 

It could have been an engine cough...but I have my suspicion of what was happening.

 

AC 91-95

 

Have a read of this, and see if this could be the problem!

 

If I am right (and probably not), tsk tsk to your instructor for not spotting a) the conditions, the onset.

 

Joker

[Witch]

Oh boy, complicate it for me!

 

OK, so the tail kicks to the left causing the nose to go right. That's what I mean by kicking to the right. Left pedal is applied and the nose goes back to the left.

 

We had about 12 or so gallons, and the wind was non-existant sans the up drafts on the other side. That took me by suprise.

 

The kick stayed until pedal was applied. In each case we probably yawed about 20-30 degrees.

 

Mostly I think I'm not applying enough pedal when coming to a stop, but most of the time it seems like the wind catches it. Rotorwash? It does this in both helos I fly, especially when landing in fields and rock.

 

I can't get AC 91-95 to come up right now.

 

I don't know. This and not being able to land exactly on a spot-I come up short-really has me bummed. Don't even ask about the hover auto. I'll just have to work on it.

 

Later

[500E]

Worth the read Joker, reminders are timely and can save your life.

[Gomer Pylot]

Higher altitude results in less tail rotor effectiveness. When you come in fast, you have to pull in lots of collective to stop the descent, which requires a lot more pitch in the tail rotor to stop the torque turn, and at altitude, it requires a LOT more. You need to make very slow approaches, with the power in before touchdown, at altitude. During approaches, slow is good, fast is very bad. Limit your rate of descent to ~300fpm, and keep your airspeed down. Get a sight picture for the approach, keep that approach angle, keep the descent to around 300fpm, and take whatever airspeed results.

 

At higher altitudes, you need to be aware that you can lose tail rotor effectiveness, and run out of power, very quickly. Mountain flying isn't the same as flying at lower altitudes, and you instructor should know that and be prepared for it. He probably doesn't have the experience, though, so you need to be very careful up there.

 

In short, the helicopter wants to turn because it takes more power to stop, and the tail rotor is less effective at stopping all that torque, on mountain tops, especially with a wind from the right. Try to keep the wind on the left if possible, because the helicopter will try to weathervane into the wind, and it takes less power if it's weathervaning to the left.

[Superman]

Hey Witch

 

AC91-95 deals with loss of tail rotor effectiveness (LTE) it is also covered in the Rotorcraft flying handbook, chapter 11. Might also read thru the steep approach. As Gomer said, slow and steady, constant angle descent, when done correctly you will have your power in and left pedal correction applied prior to reaching the hover. I try to fly (teach) a profile that would allow you to continue to the surface and land without making any large power or pitch changes. As far as the 22 goes, my personal opinion is that when you come in hot (fast) and steep, and level in the hover the governor will roll on the power rather quickly and will add to the other factors already in play causing the nose right "twitch" This also happens in the Schweizer, but it doesn't have the governor so it doesn't seem as bad as in the 22.

 

Fly Safe

Clark

[Witch]

Gomer, That's what I was doing, coming in steep. I went around a couple times until I was coming in shallower. I also have a tendancy to flare-used to fly airplanes. I know I need to come in slower but Nick says I'm coming in too slow and that I need to set down on the spot instead of hovering to it. That'll take a little more time on my part.

 

That does make sense though. Lately it seems that I don't apply a whole lot of pedal when landing until the tail kicks. Possibly because of the flare?

 

I just read about the main rotor disc interference paragraph. Now that sounds like what is happening. I've also had that while hovering and spearing cones. Dang, and I remember reading that just a month ago. Crap!

 

Thanks guys. I think that might be the problem.

 

Now then, how to prevent it? More left pedal very quickly. That in itself might be a problem for I think I have slow reaction time. It often takes a moment to realize the tail is kicking. I guess if the tail kicks, just stomp on the left pedal? Sorry, not ready for that.

 

I'll work on it. Much thanks to you Gomer.

 

Later

[joker]

Witch,

 

You must aim to avoid this situation...not simply say, "when it happens, I'll .....!"

 

Gomer is absolutely right in his description of the power demands when landing hot / high / heavy. Everything you explain fits bill for an insidious LTE as you pull torque to bleed this last speed off. That was obvious from your first post.

 

Your prevention should be to slow the approaches down of course. But also your coordination between torque (pulling collective) and anti-torque (applying left pedal) needs to be greater. Sit at home, and with imaginary controls, and do 'down / right / aft, up / left / forward'. Do this over and over again.

 

Quick question: How close to the left pedal limit do you get to recover the 'kick'?

 

The point is, your instructor is either not too concerned about this at this moment, or he can't see what is happening. Let's hope its the former rather than the latter.

 

Let's hope, he can see what is happening and is allowing you to get the feel of the aircraft, whilst he is confidently in control of the situation. Let's hope that what you feel as being a kick, is simply a subtle right yaw to him.

 

However, I am concerned. As you talk of 'stomping' on pedals, and 'fighting it', and you instructor 'freaking out', then it doesn't sound that in-controll at all. Have a good chat with your man, 'Nick' about all this. Find out what he thinks of it.

 

Quick question: When he briefed you on that flight, can you remember what his teaching objectives were?

 

 

Good luck,

 

 

Joker

[Brianmech72]

I've never experienced an LTE as I fly in Delaware which is less than 200' ASL in most places. Does LTE happen in a "kick" like he describes it? I would think it would be more gradual and maybe even a mushy feel to the tail. I'm only imagining what it would be like. The engine cough should cause a kick though. I am just getting the hang of the correlated throttle on the Enstrom and I have noticed that a throttle change kicks the nose around a lot sharper than a power change with the collective.

[joker]

Brianmechanic,

 

never experienced an LTE as I fly in Delaware which is less than 200' ASL

 

I am sure you don't do all your flying below 200ASL!

 

Sarcasm aside, let's get one thing straight....LTE can happen at any altitidue. Its just that altitude (rather high density altitude) can make it happen sooner.

 

LTE is insidious...it creeps up on you. Most of the time you deal with it naturally and without thinking. As you raise collective you automatically apply left pedal, without really thinking why.

 

The problem is, there is a threshold where it becomes very difficult to recover from using pedal alone (possibly unrecoverable), and then everything happens quickly.

 

So you are both right and wrong...it does happen gradually, but to a point. Then you may well get the sensation that the tail 'whips' round.

 

It is important to know that AC verbatim. The conditions which cause LTE are well known and accurate. The recovery technique works...I know!

 

Joker

[Eric Hunt]

Why are you all brainwashed with "LTE"?? It doesn't really exist. All you are describing here is running out of left pedal, because you are demanding too much anti-torque. If it was a true LTE, nothing you do with the pedals can stop it, pedal stops or not.

 

Make slower approaches, bring the power (and pedal) in early, and if you are approaching the pedal limits, bug out.

[Witch]

Eric, I can't read your posts with that dang picture bouncing away there.

 

When landing I have plenty of left pedal. I'm thinking that I'm losing tail rotor thrust because of vortices from the main rotor. Nick agrees. Gomer reminded me of the causes of LTE and sure enough, there it is in the helicopter handbook-chapter 11.

 

Just have to remember to add more pedal and try to anticipate the kick if it comes.

 

Maybe that's why I don't like to fly sideways to the left?

 

Later

[flyby_heli]

LTE doesn't exist??

 

If you are running out of pedal earlier than normal (due to wind from critical azimuths or high density altitude) it means the tail rotor is not as effective as under ideal conditions. So in my eyes loss of tail rotor effectiveness (LTE) certainly exists, but can also be described simply as running out of pedal.

 

I join the line of guys suggesting to slow down the approach and bringing in the power earlier and more gradual.

 

Flyby

[Helo-Pilot]

Slowing down the approach and getting the power in early is definatly the way to go. I had a hard time with the concept for a while until one day, just like hovering, it all clicked.

 

slow down

power in

ROD 200 fpm or less

maintain the angle needed

 

I had an instructor that would want me to land into some real confined areas. I was actually flying with two instructors, and each flight one or the other would tell me to do just the opposite of the other. It really drove me nuts. Finally, one shipped out to the GOM and the one I was left with would tell me to slow down, and relax. Get the power in, slow down, control my ROD with 200 fpm or less. It works every time.

[joker]

Why are you all brainwashed with "LTE"?? It doesn't really exist. All you are describing here is running out of left pedal, because you are demanding too much anti-torque. If it was a true LTE, nothing you do with the pedals can stop it, pedal stops or not

 

Good grief....Eric, next I suppose you're going to tell me that Centrifugal Force doesn't exist either!!!

 

OK, I will concede that Witch's problems are not complete Loss of Tail Rotor Effectiveness. It's true, he is not coordinating his application of left pedal, and managing his anti-torque demands on approach. This is what I tried to suggest in Para. 3 of my Post #8.

 

However, to say that LTE doesn't exist is just a question of semantics. You interpreting the 'L' to mean a total loss...me interpreting it to mean 'less than before'.

 

If Witch's situation was due solely down to an increase of torque (as you say), then wouldn't the right yaw be gradually proportional with that application of power? But he is talking about 'kicks' - sudden right yaw disproportional to his power application which he has to 'fight' with left pedal to control. This is LTE in its onset. Its just that he does have pedal remaining to deal with it.

 

The onset of LTE doesn't have to result in full blown loss of control with the aircraft spinning round and round. As I mentioned in Post #10, it is insidious. It is happening before the total loss of control, but we deal with it naturally, and most of the time we have 'pedal' to spare.

 

4. THE PHENOMENA OF LTE.

LTE is a critical; low-speed aerodynamic

flight characteristic which can result in an

uncommanded rapid yaw rate which does not subside

of its own accord and, if not corrected, can result

in the loss of aircraft control.

My emphasis

 

 

As mentioned in the AC, it happens and 'if not corrected can result in loss of control'.

 

As for whether it exists or not, well I for sure have tried / experiencecd:

 

1 - Sitting with a tailwind and having to work the pedals just to keep heading (Weathercock Stability)

2 - Flying sideways to left and had to increase left pedal. (TR VRS)

3 - Positioned my helicopter with a quartering headwind and had to work the pedals more than normal (MR intereference)

 

In all of those situations, the mechanisms of LTE were at work. However, I had enough pedal left to control it.

 

I have created and recreated total LTE (which resulted in 180 right yaw), by deliberately combining a number of the textbook conditions. The using the textbook recovery, I halted the right yaw and flew away. (Not as a training exercise with students, and with 2000 feet altitude - BTW!)

 

It exists!

 

So let's not confuse issues here on a question of words.

 

Joker

[Witch]

Now now boys, there's no need to fight. I think what we have here is a failure to communicate. Communication is a difficult concept to communicate to others. 80% of communication is non-verbal, and seeing we can't see each other, we're only getting 20% of the message.

 

Kiss and make up.

 

Later.

[joker]

Witch,

 

There is no fighting here...just healthy debate.

 

I didn't read Eric's post as 'fighting talk' and if I sounded aggresive, I didn't mean to be.

 

Often there are different interpretations of concepts, and to debate on these is not wrong.

 

There is no failure to communicate...Eric made a statement as clear as the writing on the wall. I disagreed with this statement, although I understand what he is saying.

 

Eric and I have debated many concepts before and I don't think we could ever be seen as 'fighting'. I respect his knowledge and posts. Often he will correct me, occasionally I will correct him! That doesn't mean I have any quarrel with him.

 

So let's keep up the healthy debate.

 

As for centrifugal force...bring it on!

 

Joker

[Vaqueroaero]

Good discussion going on here.

 

I have some great videos of what happens when you come in on an approach too fast and pull in too much power at the end. Question is how to post them for all to see.

 

The most assured way to avoid the problem is to be anticipating it. Situational awareness is vital. As others have said get the power in early, and keep the rate of descent low.

 

If it starts to go wrong then try and pick speed up again and do a go around! One of the hardest things to teach someone is that by lowering the collective slightly and therefore reducing the power/torque then you are actually reducing the power demand, thereby aiding the recovery. The problem is that close to the ground instinct tells us to pull power. Obvious results with that one.

 

Another thing: it is also possible to get into the situation on takeoff aswell.

 

Short response, but have to go and fly. Any advice on the videos?

[67november]

Good discussion going on here.

 

I have some great videos of what happens when you come in on an approach too fast and pull in too much power at the end. Question is how to post them for all to see.

 

Any advice on the videos?

 

up load your videos into the gallery there is a section for videos.

[Gomer Pylot]

YouTube. You can put anything you like there, and post a link here.

[Witch]

Went flyin' again today I caught a couple of kicks, but at landing time, Nick had me land the bird in a left crosswind. I told him the tail was going to kick over and he acknowledged it would. So I taxi into the headwind, get over the spot, and turn to the right. Nothing so far. As soon as I lowered the collective, it kicked again. I caught it again but then the wind took the tail back and I had to push the right pedal. Now by this time, we had drifted about 50 feet downwind. In an attempt to look like I knew what I was doing, I turned left into the wind and tried to taxi back to the spot. I gave it some forward cyclic, and we started going up. We got into ETL and I put the collective down, and down we went. So I get over the spot and turn right and set her down...rough. Nick then takes the controls and backs it up about five feet. Now shutdown is eminent.

 

For me it was a comedy of error.

 

I've been over controlling the hover autos lately too.

 

He also did a 180. I'm not so sure about the diving part.

 

Later.

 

Oh Joker, I was kidding. Remember what I said about me coming across as a smartass?

 

I like my other avatar better.