OH-58A

0 views
Skip to first unread message

Instlsrv

unread,
Mar 5, 2000, 3:00:00 AM3/5/00
to
I am looking at purchasing an OH-58A Bell helicopter. It would have the
T63A700 turbine. Any comments good and bad would be appreciated.
Thanks.

Dangerpig

unread,
Mar 5, 2000, 3:00:00 AM3/5/00
to
Get familiar with the EP for LTE
"Instlsrv" <inst...@aol.com> wrote in message
news:20000305113035...@ng-ce1.aol.com...

Rick Troxell

unread,
Mar 5, 2000, 3:00:00 AM3/5/00
to
Also, you can barely hover IGE on a summer day without redlining TOT. Seems
they had a problem a few years back with a gear in the Power and Accessories
Gearbox disintegrating and sending shrapnel into the cabin area. (As if you
wouldn't have enough to worry about with the engine failure.) If, on the
other hand, it's a "Super A", that would be a pretty good aircraft. It
would have the T63-A-720 engine, "C" model drivetrain, and, hopefully, the
PIP tailrotor. (Less likely to encounter LTE.) Though still called an "A"
model, it would essentially be a
"C" model. How much are you paying for that thing?

ax57

Meshnet

unread,
Mar 6, 2000, 3:00:00 AM3/6/00
to
> "Instlsrv" <inst...@aol.com> wrote in message...

> > I am looking at purchasing an OH-58A Bell helicopter. It would have the
> > T63A700 turbine. Any comments good and bad would be appreciated.
> > Thanks.
Dangerpig <dng...@vvm.com> wrote in message ...

> Get familiar with the EP for LTE

Actually, get ready for a succession of maintenance nightmares in which you
seek help from your TC holder (not Bell), try to operate with surplus parts
that have questionable or no histories, and operate an aircraft with
marginal performance anywhere close to max gross. I flew this model for
years, and it's OK with one observer and no baggage, except on hot/high
days.

"LTE", on the other hand, is a misnomer. It should be called "LPE", for
"Loss of Pilot Effectiveness". It afflicts all single main rotor
helicopters, and results from a failure on the part of the pilot to maintain
smooth, coordinated flight with due regard for the limitations of the
aircraft. LTE is very difficult to demonstrate, because it is caused by
flying in ways that no conscious, thinking pilot would ever fly.

Seay

unread,
Mar 6, 2000, 3:00:00 AM3/6/00
to

"Meshnet" <jim...@ticnet.com> wrote in message
news:sc7ld1...@corp.supernews.com...

> > "Instlsrv" <inst...@aol.com> wrote in message...
> > > I am looking at purchasing an OH-58A Bell helicopter. It would have
the
> > > T63A700 turbine. Any comments good and bad would be appreciated.
> > > Thanks.
> Dangerpig <dng...@vvm.com> wrote in message ...
> > Get familiar with the EP for LTE
>Meshnet wrote ----

> "LTE", on the other hand, is a misnomer. It should be called "LPE", for
> "Loss of Pilot Effectiveness". It afflicts all single main rotor
> helicopters, and results from a failure on the part of the pilot to
maintain
> smooth, coordinated flight with due regard for the limitations of the
> aircraft. LTE is very difficult to demonstrate, because it is caused by
> flying in ways that no conscious, thinking pilot would ever fly.

I have to disagree -- at least as far as a Bell 206 is concerned (esp. with
the small tail rotor)
All you have to do is have a brisk tailwind, hover slow, and turn right --
presto!
As the tail 'whups ' around when the tailwind catches it you will be in LTE
without loss of
consciousness.
Best be thinking at that point -- I know I was -- some of it unprintable.

Butch Grafton

unread,
Mar 6, 2000, 3:00:00 AM3/6/00
to

"Seay" <wrid...@hub.ofthe.net> wrote in message
news:zRYw4.77525$Cn1.1...@news5.giganews.com...

>
> I have to disagree -- at least as far as a Bell 206 is concerned (esp.
with
> the small tail rotor)
> All you have to do is have a brisk tailwind, hover slow, and turn
ight --
> presto!
> As the tail 'whups ' around when the tailwind catches it you will be in
LTE
> without loss of
> consciousness.
> Best be thinking at that point -- I know I was -- some of it unprintable.


I takeoff everyday at max gross weight in a Bell 206 and I have to tell you
it is the best little aircraft I have ever flown with a crosswind or
tailwind component while at a hover. I too believe the biggest problem with
LTE is poor control touch. Someone correct me if I am wrong but if I
remember correctly Bell does not even mention LTE in its operators manual.
It seems to be more of an Army issue.

Butch

Norm Melick

unread,
Mar 7, 2000, 3:00:00 AM3/7/00
to
Butch Grafton wrote:

> Someone correct me if I am wrong but if I
> remember correctly Bell does not even mention LTE in its operators > > manual.
> It seems to be more of an Army issue.
>
> Butch


I don't think you are wrong, but Bell Hurst has/had a video
on LTE that all students could view during their breaks in
training. It was put out by the Army, I think.

I can't grab my manual right away, but LTE was discussed
during my initial and re-current training.


Norm

Shaber CJ

unread,
Mar 7, 2000, 3:00:00 AM3/7/00
to
>
>> Someone correct me if I am wrong but if I
>> remember correctly Bell does not even mention LTE in its operators > >
>manual.

Bell does mention LTE in the manual and it is an important compoente when
checking out in a 206, at least where i learned.

Walter Hawn

unread,
Mar 7, 2000, 3:00:00 AM3/7/00
to
This must be a function of the little tail rotor. I've 10's of
thousands of takeoffs, in 206's at all weights, winds and loads. Never
once had one even start to depart from control. All with the big fan in
back.
On the other hand, the scenario described seems to be a perfect setup
for the event. 206's are not perfect, just very good honest little
birds. The large tail rotor is installed for a reason.
180 Walt

Butch Grafton

unread,
Mar 7, 2000, 3:00:00 AM3/7/00
to

"John Eacott" <eac...@helicopterservice.com.au> wrote in message
news:wTex4.1$uf7...@vic.nntp.telstra.net...
> Butch,
>
> LTE references from Bell:
>
> Rotor Breeze Jul/August 1984
> Operational Safety Notice OSN 206-83-10 Oct 1983
> Information letter 206-84-41/206L-84-27 July 1984
>
>
> --
> John Eacott
> The Helicopter Service Australia
> www.helicopterservice.com.au
>

But did they ever place it in an operators manual? I know our Bell manuals
do not mention it but the Army's rewritten version does.

Butch

Seay

unread,
Mar 7, 2000, 3:00:00 AM3/7/00
to

"Walter Hawn" <weave...@worldnet.att.net> wrote in message
news:38C50A4C...@worldnet.att.net...

http://weather.noaa.gov/weather/current/KLBB.html
current windWSW at 39mph gusting to 50mph
bring your big'ol tailrotor on down and give it a
downwind hover try at LTE.
(results may vary)
Hehe

John Eacott

unread,
Mar 8, 2000, 3:00:00 AM3/8/00
to

Butch Grafton <1but...@snowhill.com> wrote in message
news:38c46895$1...@news.snowhill.com...

>
> I takeoff everyday at max gross weight in a Bell 206 and I have to tell
you
> it is the best little aircraft I have ever flown with a crosswind or
> tailwind component while at a hover. I too believe the biggest problem
with
> LTE is poor control touch. Someone correct me if I am wrong but if I

> remember correctly Bell does not even mention LTE in its operators manual.
> It seems to be more of an Army issue.

Arne Stühmer

unread,
Mar 8, 2000, 3:00:00 AM3/8/00
to
Hi
Sorry, but what does LTE actually mean?
Thanx in advance
Arne
_________________________________
Total Flight-Time: 1.0 h - R22 :)

Meshnet

unread,
Mar 8, 2000, 3:00:00 AM3/8/00
to
"LTE" is an abbreviation for "Loss of Tailrotor Effectiveness". When the US
Army first encountered a problem with uncontrolled yaw rates in OH-58As, it
called it "tailrotor stall". Testing showed that tailrotor stall is
effectively impossible in a properly rigged OH-58A tailrotor. Further
testing and statistical analysis of occurrences showed that there is an
apparent -- I use the word "apparent" for a reason -- loss of tailrotor
effectiveness in two circumstances:
1. In what is called a "vortex ring state", when the wind is coming
from a direction which causes the downwash of the main rotor to interfere
with the air hitting the tailrotor. This condition is essentially found
only at airspeeds below translational lift.
2. In any circumstance, but usually HOGE, in which a pilot allows a
yaw rate to become established before acting to counteract it. High slow
flight by police and newscam helicopters is a typical example. The pilot
focuses on something happening on the ground, probably while orbiting the
ground scene slowly, and a yaw rate becomes established before the pilot is
aware of it. Trading altitude for airspeed while putting in full left pedal
typically permits a recovery. Failure to do so generally results in a
damaging, but rarely fatal, impact with the ground. Another situation in
which such yaw rates can become established is in "hot dog" approaches, in
which vertical and horizontal approach rates necessitate a large late
application of collective, when the pilot fails to adequately compensate
with left pedal. How often have you seen a helicopter yaw a bit to the
right when approaching to a hover? If not caught promptly, that yaw can
become uncontrollable.
The key thing to remember is that these problems apply to all single main
rotor helicopters, including NOTARs. If the statistics are adjusted to take
into account the vastly greater numbers of 206 series helicopters compared
to any other model, and the relative lack of experience of many 206 pilots
compared to those in more expensive models, the apparently higher experience
of LTE in 206/OH-58A helicopters tends to greatly moderate. I don't think
the difference actually disappears, though.
Arne Stühmer <arnest...@geocities.com> wrote in message
news:38C65D95...@geocities.com...

Walter Hawn

unread,
Mar 8, 2000, 3:00:00 AM3/8/00
to
Seay wrote:
>
> http://weather.noaa.gov/weather/current/KLBB.html
> current windWSW at 39mph gusting to 50mph
> bring your big'ol tailrotor on down and give it a
> downwind hover try at LTE.
> (results may vary)
> Hehe

34 knots gusting 43? Been there, done that.
If you're buyin', I'm flyin... Wait- That doesn't sound right.
Have to use your bird, I'm not crazy enough to own a helo.
180 Walt

Bob Barbanes

unread,
Mar 8, 2000, 3:00:00 AM3/8/00
to
Jim Burtt wrote:
(a bunch of good stuff about LTE snipped)

>The key thing to remember is that these problems apply to all single main
>rotor helicopters, including NOTARs.

But... The Bell 206 is especially vulnerable in one regard. LTE can also occur
in the following scenario: high power demand with the wind from the right rear.
The vertical fin on the 206 blanks off a LOT of tail rotor area both above and
below the tailboom, and acts as a pretty decent weathervane to catch the wind.
I got into LTE at a high (2,000 feet) hover one day in a 206L (I forget whether
it was a "straight"-L or an L-1). When the thing snapped to the right I
thought I'd lost the tail rotor. I kept the left pedal in, but don't recall
going to FULL travel on it, which is recommended. I sat there, frozen, for
maybe half a turn. Then I woke up, followed it around with cyclic, lowered the
pitch and flew out of it with maybe a hundred foot loss or so. Very scary.
Potentially ugly if I'd have been at only 100 feet over the trees. After that
I was MUCH more aware of hover work (high power) with the wind off the right
rear.

Live and learn. Learn and live.

Bob

"The dignity of the craft is that it creates a fellowship."
Antoine de St. Exupery

Nick Lappos

unread,
Mar 8, 2000, 3:00:00 AM3/8/00
to
Let me wade in on this one, with some careful words about LTE.

The size and thrust of the tail rotor are the key determinate of
the aircraft's propensity for LTE. LTE is not a pervasive single
rotor helicopter problem, in fact, virtually all LTE occurrences
involve only two types of helicopter, both Bell.

The term LTE describes the right yaw, but it is not a condition
where the tail rotor gives up the ghost. Most occurrences
involve pulling some power at the bottom of an approach, where
the extra power absorbs the small amount of anti-torque
available, and the main rotor torque takes the aircraft for a
ride.

Cross winds can cause main rotor wash to enter the tail rotor and
cause a loss of thrust of maybe 5% or so, enough that a marginal
aircraft is kicked out of control. The key is to have enough
extra tail rotor thrust to absorb this small loss, and also
enough to allow some vertical maneuvering.

In smooth hands, LTE can be avoided, as long as the flight does
not involve OGE maneuvering where the torque is high and the tail
rotor is really pushed to its limits.

There was an FAA push to include LTE words in all single rotor
helicopter flight manuals, but it was beaten down by all of those
manufacturers who make helicopters with good tail rotor thrust
margins. I assume the one manufacturer who experiences virtually
all the LTE occurrences chose not to go it alone and create a
competative disadvantage.

I know of no H-60 or S-76 LTE events, not surprising when you
consider their ability to sustain flight in 35 to 50 knot cross
winds. This is also true of Apache and OH-58D. OH-58A/C, Bell
206 and Cobras are notorious for LTE, and the original OH-58D was
rejected by the Army until the tail rotor was redesigned to
eliminate LTE that occurred during bob-down maneuvers.

Nick Lappos


* Sent from RemarQ http://www.remarq.com The Internet's Discussion Network *
The fastest and easiest way to search and participate in Usenet - Free!


Instlsrv

unread,
Mar 9, 2000, 3:00:00 AM3/9/00
to
Im looking in my OH58 operators manual and there are limitations. Chapter 5
p.10 Manuvering section 5-24 states a hovering limitation. "Ten percent of
total petal travel, full right to full left, is considered adequate for safe
control. The rearward airspeed limit is 30 knots and sideward limit is 35 knots
except that control is marginal for certain combinations of relative wind
velocity and azimuth angles (measured clockwise form the nose of the
helicopter). See chapter 8 for a description of the marginal wind velocity and
azimuth angles.
Well this is definately interesting. I thought this was the Armys primary
trainer for years. Must have instilled good training.
What is an OH58A with a T63-A700 worth. All life limited components are to
have 700-1000 hrs left on them. The ship will come with everything except
radios and transponder, but be wired for a civilian set. It will be test flown
and dynamically balanced down to .2ips or less. Comes OD Green. Not sure
about the size of the tailrotor, but he said it would be new. What should it
be.
Any and all help and information are appreciated. I live in Wisconsin at
about 680msl. (enough power for 4 fat WI people to be lifted off with full
fuel?)
Thanks, Phil
PM

nla...@miami.nospam.gdi.net

unread,
Mar 9, 2000, 3:00:00 AM3/9/00
to
(Instlsrv) wrote:
>Im looking in my OH58 operators manual and there are limitations. Chapter 5
>p.10 Manuvering section 5-24 states a hovering limitation. "Ten percent of
>total petal travel, full right to full left, is considered adequate for safe
>control. The rearward airspeed limit is 30 knots and sideward limit is 35 knots
>except that control is marginal for certain combinations of relative wind
>velocity and azimuth angles (measured clockwise form the nose of the
>helicopter). See chapter 8 for a description of the marginal wind velocity and
>azimuth angles.

Nick sez:
You are looking at the Army manual. The civil B-206 manual keeps oddly quiet
about all this.

(Instlsrv) wrote:
Not sure about the size of the tailrotor, but he said it would be new. What
should it be.

Nick sez:
The comment on size and thrust of the tail rotor is more for the designer and
the budding aerospace engineers among us. As far as I know, there is no
optional bigger tail rotor on the members of the 206 family.

All this about LTE being said, lots of 206 pilots fly lots of missions without
tripping over LTE. While other helos have better histories in this matter, if
flown prudently, any certified helicopter should serve you well. (Bell is
mailing me an attaboy right now, I'm sure!)

Good luck!

Nick Lappos

scott gardner

unread,
Mar 9, 2000, 3:00:00 AM3/9/00
to

<nla...@miami.nospam.gdi.net> wrote in message
news:scechn...@news.supernews.com...

> (Instlsrv) wrote:
> >Im looking in my OH58 operators manual and there are limitations.
Chapter 5
> >p.10 Manuvering section 5-24 states a hovering limitation. "Ten percent
of
> >total petal travel, full right to full left, is considered adequate for
safe
> >control. The rearward airspeed limit is 30 knots and sideward limit is 35
knots
> >except that control is marginal for certain combinations of relative wind
> >velocity and azimuth angles (measured clockwise form the nose of the
> >helicopter). See chapter 8 for a description of the marginal wind
velocity and
> >azimuth angles.
>

During flight testing last summer, with winds of 2-3 knots, we absolutely
could not get 17 knot rearward flight. Not after numerous tries, with a
d*&^ good test pilot, using a pace vehicle.

We checked the rigging on the swashplate and it was rigged IAW the Bell
manual. It was biased 2 degrees forward when the rigging pin was installed
to locate the center of travel of the cylic.

The data from some of the original FAA testing said the swashplate was to be
0 degrees at center cyclic. We checked with Bell and they can't say for
sure whether or not it is supposed to have 2 degree forward tilt, only "rig
according to the manual". We checked a few other 206s and they all had the
forward tilt.

I cannot understand why we couldn't get to 17 knot rearward flight which is
the minimum according to the FAA.
Does anyone have any data to confirm our results? If your're curious, stick
a 5/16 bolt in the centering hole for the cyclic and put a protractor
(digital preferred) on the swashplate and measure the tilt relative to the
mast.
Maybe someone like Bob Barbanes can try running down the runway backward on
a no wind day and let me know how it goes. Be sure you have enough
elevation to fly out when it whips around.

I agree with Nick. LTE is more correctly called "wimpy tail rotor" The
ratio of tail rotor horsepower to main rotor horsepower has changed as
designers became aware of the need for more tail rotor authority. The 206
was designed in the 60s. BTW, the 427 seems to have plenty of tail rotor
power. Good rearward flight speed while the tail rotor is loudly growling.

Scott Gardner


Meshnet

unread,
Mar 9, 2000, 3:00:00 AM3/9/00
to

Nick Lappos <nlappos...@miami.gdi.net.invalid> wrote in message
news:1f4586c6...@usw-ex0102-083.remarq.com...

> Let me wade in on this one, with some careful words about LTE.
>
> The size and thrust of the tail rotor are the key determinate of
> the aircraft's propensity for LTE. (Snip.)

Nick: I appreciate the care you have taken with your words about LTE. I
disagree with your statement that the size and thrust of the tail rotor are
the key determinant. Your own description of the circumstances most likely
to generate "LTE" shows that the skill and attentiveness of the pilot is the
key determinant.

The key factors in creating the circumstances that lead to "Loss of Pilot
Effectiveness" in the form of LTE are mission-related. Adjust the numbers
actuarily for the predominant presence of certain Bell models in the
high-risk missions, and for the experience level of the pilots, and most of
the disparity goes away. I have seen video footage of "LTE" in a Dauphin,
for instance, which is not generally associated with this phenomenon.

Seay

unread,
Mar 9, 2000, 3:00:00 AM3/9/00
to

<nla...@miami.nospam.gdi.net> wrote in message
news:scechn...@news.supernews.com...
> The comment on size and thrust of the tail rotor is more for the designer
and
> the budding aerospace engineers among us. As far as I know, there is no
> optional bigger tail rotor on the members of the 206 family.
>
> All this about LTE being said, lots of 206 pilots fly lots of missions
without
> tripping over LTE. While other helos have better histories in this
matter, if
> flown prudently, any certified helicopter should serve you well. (Bell is
> mailing me an attaboy right now, I'm sure!)
>
> Good luck!
>
> Nick Lappos

I don't know exactly when Bell changed the tailrotor on the 206 but the
earlier models have a smaller rotor. Mine is S/N 327 and has the smaller
rotor.
IF you are careful about flight regimen then the smaller rotor is nice
because it uses less power.
Also the 206A model frame is lighter than the subsequent B model by 200 Lbs.
Therefore the helo's like mine which are a A/B or else simply a B conversion
have more lifting capability.
The early models also have hydraulic boosted foot pedals which I like but I
have heard some criticise. The boosted pedals are not a A or B model feature
but for some reason were eliminated somewhere in the series at S/N 600's or
so.
I THINK the heavier frame was military related to allow more 'attachments'
(weapons, etc) but I am not sure.
Anyway, I like my light frame , small tail rotor 206 just fine.
I can promise you need to respect LTE in the West Texas winds (been there --
done that)
I have found it to be predictable and recoverable as long as one is not
daydreaming and you remember (always ) which direction the wind is coming
from so you can use the breeze to bring the tail under control (pull cyclic
into the wind).
Can also state R22's will behave very close to the same but are a little
less likely to LTE and quicker to recover. (Quicker to do almost anything!).
I can't remember which magazine I read it in but Bell equipped Harrison
Ford's Longranger (that he rolled in the riverbed) with a beefier tailrotor
because he planned to use it on a ranch at a fairly high altitude.
Don't know if the blades were longer, bigger or what.
There may have been other mods for altitude performance.


Meshnet

unread,
Mar 9, 2000, 3:00:00 AM3/9/00
to

Instlsrv <inst...@aol.com> wrote in message
news:20000308220419...@ng-cj1.aol.com...
> (SNIP>)

> What is an OH58A with a T63-A700 worth. All life limited components are
to
> have 700-1000 hrs left on them. The ship will come with everything except
> radios and transponder, but be wired for a civilian set. It will be test
flown
> and dynamically balanced down to .2ips or less. Comes OD Green. Not sure

> about the size of the tailrotor, but he said it would be new. What should
it
> be.
> Any and all help and information are appreciated. I live in Wisconsin
at
> about 680msl. (enough power for 4 fat WI people to be lifted off with full
> fuel?)
> Thanks, Phil

Don't count on being able to pick up four cheeseheads with a full bag. Even
if you can pick up, controllability at HIGE will be dodgy, and HOGE will
probably be impossible, even on a cool day. Price? I'm not an expert, but
$50,000 would be the upper limit, unless you're a collector of rare and
valuable sports cars, baseball cards, etc.


C Morrice

unread,
Mar 9, 2000, 3:00:00 AM3/9/00
to
When you do S.I 206-112 -installation of C20B engine you get to mod T/R
gearbox and put on long tail rotor blades a la 206L. However full left
pedal angle is derigged so operationally the benefit is only to allow
interchangeability of long blades if you happen to run a mixed 206 B and
206L fleet.

However at S/N 4005 and sub on the 206BIII Bell has added a larger diameter
T/R driveshaft which accomodates the long blades and allows them to be
rigged to a higher left pedal angle. This should give better left pedal
control. I will have to look at HIGE and HOGE charts to see if this is
reflected in the charts.

CDM
Seay wrote in message ...

Rick Troxell

unread,
Mar 9, 2000, 3:00:00 AM3/9/00
to
The OH-58 originally had a tailrotor diameter of 5' 2". Back in the
mid-1980's, the number of mishaps in the OH-58 that were attributed to LTE
were high enough that the Army decided to implement a "Product Improvement
Program". They began to replace the tailrotors on the OH-58 with the 5' 5"
diameter tail rotor from the civilian Bell 206's that were in production at
the time. LTE-related accidents virtually ceased after the fleet was
modified. "Instlsrv"'s OH-58 should have the 5' 5" tail rotor unless it's
been in storage for 15 years or so.
There are other differences as well. The OH-58 has a main rotor diameter of
35' 4", as compared to the 206's diameter of 33' 4". A difference of 2' in
rotor diameter is significant. The tailboom is also 1' longer on the OH-58.
The OH-58 is heavier due to armor, (which can be removed), and to military
requirements for certain items to be "beefier". (I.E. the canopies on the
OH-58 are made from a thicker plexiglass.)
In my opinion, the OH-58 is more prone to hot start than the 206. (Perhaps
due to it's higher rotor inertia and the increased time required to get
everything turning.) Be very careful when the OAT/DA is high, the battery
is marginal, and the winds are up the exhaust. The latter may sound
trivial, but your TOT will be anywhere from 50-100 degrees higher when
starting with a tailwind as opposed to a headwind. If it comes with a tired
old Ni-Cad installed, you'd be better off investing in a Sealed Lead/Acid
Battery (SLAB). Could save your engine.

ax57

Tim B

unread,
Mar 10, 2000, 3:00:00 AM3/10/00
to
If nobody else from Bell thanks you, I will. Flew many years in the 206
series and never had a serious problem. Appreciate you not ragging on Bell
all the time like some. (That should raise some comments). Keep up the good
work.
Tim B

<nla...@miami.nospam.gdi.net> wrote in message
news:scechn...@news.supernews.com...
> (Instlsrv) wrote:
> >Im looking in my OH58 operators manual and there are limitations.
Chapter 5
> >p.10 Manuvering section 5-24 states a hovering limitation. "Ten percent
of
> >total petal travel, full right to full left, is considered adequate for
safe
> >control. The rearward airspeed limit is 30 knots and sideward limit is 35
knots
> >except that control is marginal for certain combinations of relative wind
> >velocity and azimuth angles (measured clockwise form the nose of the
> >helicopter). See chapter 8 for a description of the marginal wind
velocity and
> >azimuth angles.
>
> Nick sez:
> You are looking at the Army manual. The civil B-206 manual keeps oddly
quiet
> about all this.
>
> (Instlsrv) wrote:
> Not sure about the size of the tailrotor, but he said it would be new.
What
> should it be.
>

nla...@miami.nospam.gdi.net

unread,
Mar 10, 2000, 3:00:00 AM3/10/00
to


Meshnet,
What you say about the pilot's ability to screw up is correct, but only as far
as how marginal the helicopter he is flying is. My point is that if the tail
rotor is too weak, LTE is more probable. This is a fact, and if we simply
blame the pilot for LTE, we ignore the fact that LTE only occurs in a few
helos.

In short, everybody else who makes helicopters must be doing something right.
If we let them just blame the pilot, we don't improve the situation. LTE is
caused by marginal helicopters. This poor margin of safety burdens the pilot
with being extra careful, and the small percentage of times that someone is
not perfectly careful, he gets burned (literally).

The mission is to blame, too. NOE tactics brought out LTE for the poor helos
because of the OGE maneuvering needs of the new mission. The Army increased
the tail rotor requirements (mostly by demanding more sideward flight
capability) for newer helos (UH-60, AH-64, OH-58D, Comanche) and as a
result, they can't get LTE.

The mission makes the poor helo drop out of the game. It starts with a poor
helo, though.

Nick


Shaber CJ

unread,
Mar 11, 2000, 3:00:00 AM3/11/00
to
>you seen a helicopter yaw a bit to the
>right when approaching to a hover? If not caught promptly, that yaw can
>become uncontrollable.
>The key thing to remember is that these problems apply to all single main
>rotor helicopters, including NOTARs. If the statistics are adjusted to take
>into account the vastly greater numbers of 206 series helicopters compared
>to any other model, and the relative lack of experience of many 206 pilots
>compared to those in more expensive models, the apparently higher experience
>of LTE in 206/OH-58A helicopters tends to greatly moderate. .


I do not believe you can get into an LTE situation in the 520N or the 902N
NOTARs. Both these helicopters can be lifted off and fly a pattern with the
pedals fixed in neutral position. as collective is increased so is the fan
speed.

The NOTAR can have the air flow around the boom separate in a right turn with a
LARGE slip. When the air flow separates ease off the right pedal and the air
flow reattaches. You will only get this flow separation at slow speeds and a
very LARGE slip.

Craig

nla...@bellsouth.nospam.net

unread,
Mar 11, 2000, 3:00:00 AM3/11/00
to
C Morrice wrote:
>When you do S.I 206-112 -installation of C20B engine you get to mod T/R
>gearbox and put on long tail rotor blades a la 206L. However full left
>pedal angle is derigged so operationally the benefit is only to allow
>interchangeability of long blades if you happen to run a mixed 206 B and
>206L fleet.
>
>However at S/N 4005 and sub on the 206BIII Bell has added a larger diameter
>T/R driveshaft which accomodates the long blades and allows them to be
>rigged to a higher left pedal angle. This should give better left pedal
>control. I will have to look at HIGE and HOGE charts to see if this is
>reflected in the charts.
>

Thanks for the info! Your observation proves my point about the "weakness" of
the tail rotor. Let me explain.

If the OGE and IGE performance charts change when you change the tail rotor,
it illustrates that the tail rotor was the reason for the altitude limit.

For virtually all helicopters, the max gross weight to hover is set by the
engine power or the transmission torque limit. The tail rotor is not the weak
link. We test the sideward flight capability at altitude to confirm that the
tail rotor is still adequate at the higher power (higher power is higher
torque which requires more anti-torque).

For the 206 family, (and also for the "cat B 9 passengers or less"
certification that the 212 412 and 430 have), the tail rotor cannot provide
enough anti torque to allow the higher weights at altitude, so the IGE and OGE
weight allowable curves reflect the place where the tail rotor gives up the
ghost. More weight at altitude can only be carried if the tail rotor is
improved.

Nick

scott gardner

unread,
Mar 13, 2000, 3:00:00 AM3/13/00
to
> >> I do not believe you can get into an LTE situation in the 520N or the
902N
> NOTARs. Both these helicopters can be lifted off and fly a pattern with
the
> pedals fixed in neutral position. as collective is increased so is the
fan
> speed.
>
I thought the fan was a direct drive from the main rotor, how can it speed
up?
Are the fan blades variable pitch? That would make more sense.

Scott


scott gardner

unread,
Mar 13, 2000, 3:00:00 AM3/13/00
to

Unka Nick sez:
> If the OGE and IGE performance charts change when you change the tail
rotor,
> it illustrates that the tail rotor was the reason for the altitude limit.
>
> For virtually all helicopters, the max gross weight to hover is set by the
> engine power or the transmission torque limit. The tail rotor is not the
weak
> link. We test the sideward flight capability at altitude to confirm that
the
> tail rotor is still adequate at the higher power (higher power is higher
> torque which requires more anti-torque).
>
> For the 206 family, (and also for the "cat B 9 passengers or less"
> certification that the 212 412 and 430 have), the tail rotor cannot
provide
> enough anti torque to allow the higher weights at altitude, so the IGE and
OGE
> weight allowable curves reflect the place where the tail rotor gives up
the
> ghost. More weight at altitude can only be carried if the tail rotor is
> improved.
>
> Nick

Bell has an option for the 206L4 that does just that: increases max
available tail rotor blade pitch angle as the density altitiude increases.

Global Helicopter Technology has a similar product for the UH-1H called the
Density Altitude Compensator. E-mail gh...@airmail.net for more info.

Scott Gardner


Shaber CJ

unread,
Mar 13, 2000, 3:00:00 AM3/13/00
to
> I thought the fan was a direct drive from the main rotor, how can it speed
>up?
>Are the fan blades variable pitch? That would make more sense.
>

I am sorry, did I say the fan speed increases? The fan blasdes are variable
pitch.

Shaber CJ

unread,
Mar 13, 2000, 3:00:00 AM3/13/00
to
>There are other differences as well. The OH-58 has a main rotor diameter of
>35' 4", as compared to the 206's diameter of 33' 4". A difference of 2' in
>rotor diameter is significant. The tailboom is also 1' longer on the OH-58.

Any idea why (engineering or otherwise) the military required longer blades are
a lower RPM for the OH-58 as compared to the 206BIII?

Paul Baechler

unread,
Mar 13, 2000, 3:00:00 AM3/13/00
to
In article <20000313093901...@ng-fd1.aol.com>,
shab...@aol.com (Shaber CJ) wrote:

Actually, since the OH-58 came first, the question should be why the
206BIII has shorter blades.

--
Paul Baechler
pbae...@bellsouth.net

RW Walker

unread,
Mar 13, 2000, 3:00:00 AM3/13/00
to

Paul Baechler wrote in message ...
As I recall things, Bell started out with an ugly little thing (OH-4A) that
lost to the H-6 in the LOH contest. They then used this dynamics package on
an Italian styled body to produce the 206A. The OH-58 came AFTER all this.

So, I think the correct question is "why does the OH-58A have longer blades
than the H-4/206".

Bill "so I'm a nitpicker" Walker

Beavis

unread,
Mar 14, 2000, 3:00:00 AM3/14/00
to
In article <E8E5932009CD6989.DBE64100...@lp.airnew
s.net>, scott gardner <spe...@arlington.net> writes

>> >> I do not believe you can get into an LTE situation in the 520N or the
>902N
>> NOTARs. Both these helicopters can be lifted off and fly a pattern with
>the
>> pedals fixed in neutral position. as collective is increased so is the
>fan
>> speed.
>>
> I thought the fan was a direct drive from the main rotor, how can it speed
>up?
>Are the fan blades variable pitch? That would make more sense.

The fans ARE variable pitch Scott, but I'm not sure if they're fixed
speed or not.

Beav

John Bicker

unread,
Mar 16, 2000, 3:00:00 AM3/16/00
to
in article sujGefAw...@nachos.demon.co.uk, Beavis at
Bea...@nachos.demon.co.uk wrote on 13/3/00 20:42:

Sorry, wrong on both counts, the collective pitch on a 520N or 600N (not
familiar with Explorer - Rare species) for that matter is not connected to
the anti-torque controls. The fan speed also does not vary in relation to
the Nr. As for flow separation in a large RH slipping turn I would like to
see the facts and or how it was proven, there are other factors involved and
this sounds like a believable explanation. i.e. BS.

The anti torque thrust is proportional to the flow generated by the main
rotor which is induced by the coanda effect generated from the tailboom
slots which are fed by the fan. Hence the "pedals on the floor" trick.

One undesirable trait which should be demonstrated to all Notar pilots is
the onset of "anti torque" as pitch is pulled prior to touchdown in auto
rotation. Something that you don't really need. Ponder the possible
consequences.

IMHO the hook was already taken with the "Fenestron" and this was all that
was left to establish any individual indentity for these aircraft. The
supposed merits hardly justify the time and effort spent.

P.S. What is really "wrong" with a tail rotor?

Reply all
Reply to author
Forward
0 new messages