Subject: LTE
Date: Tue, 9 May 2000 08:44:34 -0500
From: "Dave Anderson"

Glad to see you do the transcribe of the article. I have been doing some tests with tail boom strakes on the 206 and also finished a structural demo on a UH-1H with strakes which is now STC'd. The purpose of the strakes is to reduce the side force on the tail boom while in right sideward flight (or winds from the right). This gives some increase in pedal margins. As a part of my test work I have had several conversations with the author and although he is not a fan of strakes, he has been a help in the test sequence.

I have the dubious experience of looking at all of the four conditions mentioned in the article which means most of my 206 time is sideways and backwards. In my opinion, all helicopters with tail rotors are susceptible to some form of LTE. I have seen it in Bell's as well as Hughes, and Russian A/C. I don't have much time in Sikorsky's, but I have no reason to believe that it can't be induced.

The article was Don Bloom's experience in flight test with the OH-58A which is not exactly a 206B. This aircraft as well as OH-6's and few others operated in an environment where slow speeds and right turns at low altitudes were the normal procedure. Accordingly, there were a lot of accidents as well as overtorques. I haven't done this, but I can imagine that herding cattle is probably a good set up for LTE.

Dave Anderson


Subject: Re: LTE
Date: Tue, 9 May 2000 09:58:35 -0500
From: "Meshnet"

I emphatically agree with the observation that all helicopters with tail rotors are susceptible to some form of LTE, which I prefer to call "LPE", for "Loss of Pilot Effectiveness". I have seen film footage from inside a Dauphine that got into LTE during an approach to a ship.

Herding cattle, police work, and news cam flights are three of the mission profiles exhibiting the highest frequency of "LPE". Pilots start flying ground speed and focusing on a target on the ground, so that when a yaw begins they are often unaware of it until a serious yaw rate has been established. The other situation in which uncontrolled yaw most often develops is in hot approaches, where the pilot tends to honk in a big flare and pitch pull while still out of ground effect.

As Don Bloom's experience has shown, LTE is very difficult to get into "on purpose", because it is an artifact of uncoordinated flight, and few of us get into that mode when we are paying attention to what we are doing -- except, of course, for cops, news cams, and such, where the job is on the ground.


Subject: Re: LTE
Date: Tue, 9 May 2000 20:51:25 -0500
From: "Seay"

>>The other situation in which uncontrolled yaw most often
>>develops is in hot approaches, where the pilot tends to honk in a big flare
>>and pitch pull while still out of ground effect.

>Uhh...okay, I'll bite. Could someone explain to me how this can be a set-up
>for LTE?

Juat had a taste of this about three weeks ago in a Bell 206-- I was letting my son try an approach and he flared while still OGE --- Next thing I hear is "Dad, there's no more left pedal"

It was a hot day (95F) and we were full of fuel. He had the collective way up and the torque was about to overcome the tail authority.

As we came down into ground effect less collective was required and we never really began to spin However, am pretty sure if we had been slow on getting on down that the situation could have worsened rapidly. Had a spin started it would have worsened as the tail was forced into its own vortex and really failed. As usual --- when in a tight drop collective and think later.


Subject: LTE does not affect all Helos!
Date: Thu, 11 May 2000 14:52:00 GMT
From: nlappos@bellsouth.nospam.net

For Meshnet, and the others who express the universality of LTE, and who want to blame pilots for airplane problems:

While your opinion is theoretically correct, the practical issue is that several helos are woefully inadequate in basic tail rotor authority, and are therefore more likely to experience LTE.

The term LTE is itself a misnomer, in that it infers that somewhere the perfectly normal and acceptable tail rotor gets blanked, or stalls or somehow becomes ineffective. This is simply not supported by the data, or by the military tests that have been conducted.

LTE is found on helos that have poor tail rotors, where the yaw thrust margins are low in normal maneuvers. With low margins, the type and severity of maneuver that absorbs all the anti-torque is much more likely to be encountered. On helos with powerful tail rotors, LTE is non-existant I defy you to find legitimate LTE in a Black Hawk, or an Apache or an S-76.

LTE is cured in two ways:

1) In shitty helicopters, baby them as you maneuver at low speed, especially with regard to collective pitch applications in descent with cross or down winds.

2) get a helicopter with a better tail rotor, and you will never see LTE unless you purposely induce it. The proof is the US Army yaw maneuver criteria improvement over the last 30 years, which has eliminated LTE in the new designs. In 1965 (H-1, H-58), all you needed was 17 knots of sideward flight capability. In 1978 (Ah-64, UH-60) you had to show 45 knots at altitude). In 2000 (Comanche), you have to show a snappy hover turn at 45 knots.

LTE is not a problem in any helicopter that meets the modern yaw maneuver criteria. PERIOD

Why do I rag on this way? Because if we all don't help keep the issue understood, we will always have to fly crappy helicopters where some well meaning but misinformed guy can simply blame the pilot (Meshnet said "which I prefer to call "LPE", for "Loss of Pilot Effectiveness").

Modern helos can eliminate the need to blame the pilot by eliminating the need to baby the machine. The Army forced the redesign of the OH-58D to eliminate LTE, which they found when doing simple bob-down maneuvers.

Why stop at LTE, Meshnet? let's blame all those pilots for the post crash fires, and eliminate crashworthy fuel systems. Those stroking seats are for wimps who can't really fly, lets just break the backs of the assholes, ("Loss of Crappy Pilot") and eliminate the problem through Darwinism!

Seroiusly, I believe we must learn to criticize the job we are given, and the machines we use, if we are to make progress in our industry. I joke that the only difference between a test pilot and a regular pilot is that the test pilot is allowed to blame the machine.

Learn to blame the machine, learn to fix the heliport, learn to say no to the night semi-IFR mission, and maybe our loss rate will improve, our customers will be safer, and our insurance rates will drop.

Every airliner lands on the same runway, same width, same markings. They make their living changing the environment to fit their needs. They force standard angles, clearances, dimensions and procedures, and so they get impeccable safety - 10 times the safety we do.

We in Helo-land (45 clicks south east of Pepperland) are very willing to land in an LZ with a telephone pole in the center, to fly VFR at night in 500 and 1, to lift the boss over a set of wires at his heliport without complaint. And when we hit that pole, run into the terrain, or snag that wire, we blame the pilot, a poor shmoe who only has 2500 hours and 7 years experience.

This attitude has to stop - we have to stop trusting the "Right Stuff" to keep us out of the woods. We have to start expecting to get aircraft that are relatively easy to fly, systems that help us do the job and operating environments that help us keep safe.

We don't have to look too far for examples. Lose 3 helicopters in ice fog, anyone? Do you think the average person thinks helo pilots are fools? Do you think we looked foolish? Do you think a guy in Alabama will think twice about a charter because of that Alaska incident?

Wow! Did I get carried away, or what?


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Last updated 11 May 2000