Notar using turbine thrust...?
GReeder88
Seems a natural use of a lot of power.
AKAAB
maintain yaw control during an engine failure. If the engine exhaust was the
only source of air, then a failure would leave you with no yaw control. By
coupling the fan to the drivetrain, a freewheeling rotor will drive the fan
through the transmission...
Paul Agnew
John W. Hart
flight school in 1964, we were told that the Lycoming T53-1100 turbine
engine used in the UH-1D helicopter produced less than the equivalent of 10
horsepower from exhaust thrust.
John
"Steve or Kay JACOBS" <sk...@bigpond.com.au> wrote in message
news:S%w54.5405$E4.1...@newsfeeds.bigpond.com...
> Might also have to do with there not being enough exhaust thrust available
> to do the job....basically 'cos the engine is designed as a "turbo-shaft"
to
> supply torque for the Main Rotor,,,efficient design would mean not much
> waste heat left for thrust ....(but I'm sure someone will have a better
> reason!).....
>
>
> --
> Cheers 'n Beers .....Steve Jacobs :-)
> Melbourne, Australia.
>
>
GReeder88
building a turbine Rotorway and using the exhaust as a notar
but a engine out would send you spinning to your doom. Don't want that!
FYI: A Rotorway tail rotor produces about 20 lbs of thrust while a 150 hp
turbine is producing almost 80 lbs of thrust I was told.
Shaber CJ
you had an engine failure you would lose your anti-torque.
Steve or Kay JACOBS
Brad Boss
GReeder88 wrote in message <19991214085808...@ng-da1.aol.com>...
>Anyone know why Notar uses a fan instead of the thrust produced by the
turbine?
>Seems a natural use of a lot of power.
Basically, the thrust produced in a turboshaft engine, goes to turn the
power turbine wheels, which are placed at the end of the engine in the
exhaust gasses. These wheels are connected to the drivetrain to provide
torque. As you can see, there is not really any excess thrust that is not
being used by the power turbine itself. The only thing coming out of the
exhaust are the exhaust fumes, with the trust going to drive the power
turbine wheels.. Any Jet engine mechs, or engineers, out there, correct me
if I'm wrong....
Brad B.
SGT, US Army
CH-47D flight engineer
Brad Boss
RW Walker wrote in message <839iok$b06$1...@mur2.odyssey.on.ca>...
>Why, thank you for the nice request.
>
>You're on the right track, but there is still some energy left in the hot
>gases after their last pass through a turbine.
>Bill "Not really an engineer but I play one at work" Walker
>(sorry Mr.Barbanes)
Thanks, Bill.
I was going off the top of my head, and I hate giving out false info.
Turbines do fascinate me though. They look complex but are really pretty
simple, once you get past all the systems...The T-55's we use at work are
are 1950's technology. Who would have thought we'd still be using them 40
years later?
Brad (Not really a soldier, but I play one at work...;) " Boss
RW Walker
Brad Boss wrote in message ...
>
>Any Jet engine mechs, or engineers, out there, correct me
>if I'm wrong....
>
You're on the right track, but there is still some energy left in the hot
gases after their last pass through a turbine. The engine designer has to
leave some velocity in the gas after the last turbine, to keep the stuff
moving out of the engine. Otherwise it would produce back pressure, reducing
the mass flow through the whole engine.
The amount of thrust is pretty low, but not zero. Back when Westlands set a
world speed record with a Lynx (early 80s?) they tuned the engine exhausts
to magnify and direct the thrust, but they were looking for the last 0.1 of
a knot. The AStar B2 has the exhaust slightly tilted to offload the tail
rotor, but again its a small effect.
As several earlier posts pointed out, the main reason for not using engine
exhaust in the NOTAR tailboom is that the exhaust goes away when the engine
quits. The fan they do use in the NOTAR is connected to the main gearbox,
and is thus turning as long as the main is turning.
I guess when the main stops turning, lack of directional control is only one
of your problems :).
Dan & Jan Hollenbaugh
pressure returning to ambient at the exhaust face, meaning you've gotten
every bit of energy out of the air before returning it to the atmosphere.
In reality, that doesn't happen. You have to design for a margin at high
power requirements, so there's always a little left at the end under any
normal condition.
By the way, I concur with the rationale that the exhaust is not used so that
the helo has yaw control following engine failure. An additional reason
might be the engineering difficulty of keeping a pressurized tailboom at a
constant pressure with varying engine exhaust pressure under different power
requirements, and the possibility of excess backpressure stalling the engine
power turbine. It could probably be done, but the venting and controls
would be expensive and heavy. Wouldn't want to figure that one out.
Besides, the Hughes model 500 transmissions that the NOTAR aircraft use, and
that of the OH-6A the original development was done on, already had a power
take-off point for a tail rotor, easily adaptable to the internal fan. Why
add more design work when there's a simple solution staring you in the face?
Remind me some time to tell you how I did my best to get the NOTAR
development program cancelled (it was funded by the Army) in 1979.......
Dan H.
Comanche Test Engineer
Brad Boss wrote in message ...
>
>GReeder88 wrote in message
<19991214085808...@ng-da1.aol.com>...
>>Anyone know why Notar uses a fan instead of the thrust produced by the
>turbine?
>>Seems a natural use of a lot of power.
>
>Basically, the thrust produced in a turboshaft engine, goes to turn the
>power turbine wheels, which are placed at the end of the engine in the
>exhaust gasses. These wheels are connected to the drivetrain to provide
>torque. As you can see, there is not really any excess thrust that is not
>being used by the power turbine itself. The only thing coming out of the
>exhaust are the exhaust fumes, with the trust going to drive the power
>turbine wheels.. Any Jet engine mechs, or engineers, out there, correct me
>if I'm wrong....
>
Eric W Braeden
Dan & Jan Hollenbaugh <holle...@mindspring.com> wrote in message
news:83cd9f$v6m$1...@nntp9.atl.mindspring.net...
>
> Remind me some time to tell you how I did my best to get the NOTAR
> development program cancelled (it was funded by the Army) in 1979.......
>
> Dan H.
> Comanche Test Engineer
>
I'm ready for some great new insights.
Eric
Shaber CJ
>development program cancelled (it was funded by the Army) in 1979.......
Please share with us!
Dan & Jan Hollenbaugh
I was a US Army 1LT, assigned to the Aviation Systems Command (AVSCOM)
Applied Technology Laboratory at Ft. Eustis VA in 1979 as an aerospace
engineer, working in the Aeromechanics Technical Area doing wind tunnel and
performance testing. The Technical Director of AVSCOM HQ in St. Louis had
been talking informally with Hughes Helicopter folks about some independent
research they were carrying out on a Circulation Control Tail Boom, which
would use a Coanda effect to generate sideward force from the rotor downwash
in hover. This, combined with a direct jet thruster at the end of the
tailboom, would, they thought, provide enough force to replace a tail rotor.
The Tech Director asked Hughes to submit an "unsolicited proposal" for the
research, so the Army could decide if we wanted to fund it. That proposal
filtered down the ranks to my office, and I and a senior engineer were
tasked to
evaluate it for technical worthiness. We rejected the proposal, based on
our belief that the system would never be as efficient as Hughes claimed.
First of all, we thought their projections of thrust available from the
circulation control tail boom to be overstated. Second, the projections of
thrust available from the jet thruster did not take into account efficiency
lost through turning the flow 90 degrees through a set of vanes, from axial
to lateral. Third, a
smaller, higher velocity flow will always be less efficient in creating a
given amount of thrust than a larger, slower one. That's why direct jet
vertical lift, like the Harrier, is always so inefficient. Hughes also used
as part of their rationale the "success" of the thruster-type antitorque
device of the XV-9A (c. 1965). This ignores the fact that the main rotor
drive system on the XV-9A was tip jet thrust, using hot air from a set of
turbofan engines. Antitorque requirements for this were negligable, needed
only to overcome friction! And the final reports on the XV-9A rated the
system as marginal! Bottom line, a NOTAR will always be more inefficient
than a tail rotor providing the same amount of thrust. Efficiency
translates to control power, and ultimately, fuel. Finally, the contractor
was proposing that a NOTAR would enhance survivability by removing the tail
rotor, ignoring the fact that the entire pressurized tailboom was now
vulnerable area. When you shoot a big hole in a pressurized tailboom, you
now have TWO jets, and the new one may be pointing in a bad direction.
This last argument, by the way, lingered for years. I once asked the
Hughes chief aerodynamicist about it at a lecture, and his answer was that
there was enough excess flow available from the fan (IIRC, an Aerospatiale
Fenestron with the blades shortened on the prototype) to provide additional
air to the NOTAR, forgetting that would make the thrust from the ballistic
damage hole higher too. When Boeing Sikorsky and McDonnell-Bell were
competing for the LHX (now Comanche) development program, the McDonnell-Bell
design had to be modified at the last moment, because the Army survivability
analysis considered the whole tailboom to be vulnerable to threat weapons.
I was by then in my first year as LHX (Comanche) Test Engineer.
McDonnell-Bell countered by lengthening the NOTAR fan drive shaft to move
the fan down near the end of the boom - basically creating an inefficient,
internal tail rotor! I should add, in the interest of fairness, that this
was not considered a major drawback to the McDonnell-Bell design, and is not
the reason they lost the competition.
Anyway, as I started to say, bottom line - NOTAR will always be less
efficient and less responsive than a tail rotor for the same amount of
thrust. It saves you no weight, offers no performance advantage, and
doesn't lower vulnerability. There's only one reason to go with a NOTAR,
and that's if you have overriding concerns about backing the tail rotor
into the trees (or people!) in confined areas.
Anyway, we wrote up our negative evaluation and sent it up the chain. It
got out of the lab (through three levels of engineering review) with
complete approval, got up to AVSCOM HQ, and the Tech Director took one look
at it, said, "Wrong answer", and sent it back to be redone - with strong
hints as to what the right answer should be. It was taken away from my
division and given to another office in the lab. Those folks read the
writing on the wall and produced a glowing evaluation of the concept.
The rest is history. Hughes was awarded a $1M (IIRC) contract for
development, and an OH-6A as a protoype. They did the work, claimed victory,
and tried to sell NOTAR
aircraft to everyone. The Army didn't buy it, and I don't think anyone else
did either. At one time McDonnell leased a group of NOTAR equipped 500's
(MH-6) to the 160th Avn Bn, who kept them for a few months and turned them
back in as less capable than the same bird equipped with a tail rotor. I
recall some police versions somewhere, anybody know if they're still in use?
Boeing sold off that model line a year or so back when they bought
McDonnell, and I haven't heard anything about the buyer offering the NOTAR
option for sale.
So that's how I tried to get NOTAR aborted before its birth. After 20
years, I still think I was right, and that the lack of NOTAR on anything in
production proves it. This, by the way, is just my personal engineering
analysis, and does not necessarily reflect the opinions of anyone else who
works for
the Army (standard disclaimer).
Dan Hollenbaugh
Comanche Test Engineer
(I will now shut up - my license to blow my own horn is hereby suspended,
lest I tread on the toes of the many people in here who are smarter than I
am)
RonPilotPI
RW Walker
Brad Boss wrote in message ...
>are 1950's technology. Who would have thought we'd still be using them 40
>years later?
>
BW
no...@remove.mint.net
<holle...@mindspring.com> wrote:
. . .
>So that's how I tried to get NOTAR aborted before its birth. After 20
>years, I still think I was right, and that the lack of NOTAR on anything in
>production proves it. This, by the way, is just my personal engineering
>analysis, and does not necessarily reflect the opinions of anyone else who
>works for
>the Army (standard disclaimer).
>
>Dan Hollenbaugh
>Comanche Test Engineer
Hello.. I'm just an enthusiast with 20hrs flight time in a Bell 47...
Isn't NOTAR also supposed to be much quieter than a tail rotor? I
also remember all the talk about how NOTAR helos can do all sorts of
maneuvers that tail-rotor helos can't. But that's just my "Discovery
Channel" knowledge...
What is your take on ABC (the Advancing Blade Concept) that Sikorsky
pursued with their S-69 a while back? Basically it involves two
3-bladed, counter-rotating, coaxial rotors with rigid blades, mounted
close together (unlike the Kamov helos). I know we'll never have
anything like that in our military, but I'm just interested in the
design.
Dan & Jan Hollenbaugh
no...@REMOVE.mint.net wrote in message
>Hello.. I'm just an enthusiast with 20hrs flight time in a Bell 47...
>Isn't NOTAR also supposed to be much quieter than a tail rotor? I
>also remember all the talk about how NOTAR helos can do all sorts of
>maneuvers that tail-rotor helos can't. But that's just my "Discovery
>Channel" knowledge...
Yes, it's quieter, but the tail rotor is only a small portion of total
helicopter noise, so it's not that big a deal. (When was the last time you
picked up the sound of a tail rotor before you heard the engine or rotor
noise - other than the SA-365 fenestron whine, that is?) As for doing
things a tail rotor can't, the only thing is sticking the NOTAR into a bush,
which I've actually seen in PR films. Pure "Discovery Channel" BS.
>
>What is your take on ABC (the Advancing Blade Concept) that Sikorsky
>pursued with their S-69 a while back? Basically it involves two
>3-bladed, counter-rotating, coaxial rotors with rigid blades, mounted
>close together (unlike the Kamov helos). I know we'll never have
>anything like that in our military, but I'm just interested in the
>design.
>
Nothing wrong with ABC. It was one of the candidate concepts for LHX in the
'80s. What I remember is that the only problem was the high weight of blade
and mast structure needed to keep the two rotors from "shaking hands" under
maneuvering. As you note, the Kamov designs have a much higher spacing,
which allows them to use a lighter, articulated rotor system.
I should defer to Nick Lappos on this, though. He flew the program and is
much more knowledgable about it. I was just an interested observer, not
directly involved.
Eric W Braeden
Too bad your Tech Director was corrupted bureaucrat, unqualified
for his job. You did the right thing.
I've always be facinated by NOTAR and the Coanda Effect, but I
see now I missed some key ideas. Your clear post has given me
much to think about. Thanks again.
Eric
J. Mark Wolf
>
> Okay, here's the story:
>
> I was a US Army 1LT, assigned to the Aviation Systems Command (AVSCOM)
>
>
> years, I still think I was right, and that the lack of NOTAR on anything in
> production proves it. This, by the way, is just my personal engineering
> analysis, and does not necessarily reflect the opinions of anyone else who
> works for
> the Army (standard disclaimer).
>
> Dan Hollenbaugh
> Comanche Test Engineer
Very interesting account of the "design cycle" of the NOTAR. Thanks.
--
Regards
J. Mark Wolf
Pinckney, Michigan
Exec 162F N1955Z
linc
your death.
I've heard (on this NG) that the only effect that is really disconcerting is
the fact that it weathervanes into the wind because there is no tail rotor
control with the engine out.
--
Linc
-----------
Avoid the rush, get to know God early!
GReeder88 <gree...@aol.com> wrote in message
news:19991214163104...@ng-fy1.aol.com...
Ken Leander
worth reading. Do you happen to remember some of the figures for the energy
lost pushing the air through the NORTAR tail pipe? It's been a while since
I took fluid dynamics in college. But, I do seem to remember that the
energy required to push a fluid through a pipe increases geometrically with
velocity.
Ken Leander
Ken Leander
milliliters Pb/gallon)? There is an estimated 50,000 kids in Michigan alone
suffering lead poisoning. It's a permanent affliction. The lead in one
small piece of paint chip is hundreds of times more toxic than minimum safe
levels. Tooth decay, and retardation are but a couple of the symptoms.
All I'm saying is don't get complacent and progress will be made.
Ken Leander
"RW Walker" <bwalkerd...@odyssey.on.ca> wrote in message
news:83eusr$p1r$1...@mur2.odyssey.on.ca...
Dan & Jan Hollenbaugh
drive system, but that's no big deal. You do, however, want to have
directional control to point the aircraft, and for that you need air to the
notar (or control of a tail rotor)
Dan H
linc wrote in message ...
Dan & Jan Hollenbaugh
have the original analysis - if I run across it I'll post again.
Dan H.
Ken Leander wrote in message <83glli$1ak$1...@geraldo.cc.utexas.edu>...
Paul Agnew
yaw hard in the direction of blade rotation due to frictional forces.....
Paul
Shaber CJ
>years, I still think I was right, and that the lack of NOTAR on anything in
>production proves it. This, by the way, is just my personal engineering
>analysis, and does not necessarily reflect the opinions of anyone else who
>works for
>the Army (standard disclaimer).
Well, a very interesting article. However, you are wrong on many points: (I)
The market place has accepted the NOTAR; (2) MD Helicopter bought the 500, 600
and 900 series from Boeing (yes this includes the 520N, 600N, 900N and the
902N, all NOTARs). Last year MD Helicopter sold 65 aircraft, five were
traditional tail rotor and the rest NOTARs. MD has orders for over 100
helicopter to be delivered in 2000 all but six are NOTARs. (The above
information is as remembered from an article in Aviation Weekly or Airborne Law
Enforcement.)
There are many reasons the NOTAR is a great system beside the obvious of not
having a tail rotor spinning at high RPM:
Tail Rotor
Just think of all the accidents caused by a tail rotor failure or strike. The
NOTAR has eliminated these accidents.
LTE
Just last week there was a discussion of LTE while OGE hover down wind. The
NOTAR does not suffer from LTE. I have hovered the MD 520N downwind with a
17 knot wind, and it is stable as a rock. I believe the 600N is not as good
downwind but it sure beats tail rotor aircraft. The NOTAR can get a right yaw
when the airflow breaks away from the tail boom in a right descending turn with
almost no airspeed. Just add maybe 5 knots airspeed and the flow reattaches.
Safety
Check the NTSB web page and you will find two accidents with MD 520N. The 520N
just suffered its first fatal accident due to a high side governor failure
(there are over 100 flying). The other accident is really an incident where a
couple of blades hit the boom while shutting down downwind and letting the
rotors coast to a stop. There have been no failures of the NOTAR system. How
many tail rotor failures are there a year (i.e. a sweater blows out he door and
wraps around the tail rotor etc.)
Noise
The NOTAR is 50% quieter (actually measured) than a similar helicopter. When I
over fly people, horses, cows whatever, they will not look up until I have
almost on top of them. At a125 KIAS the 520N will project sound 500 feet in
front of the bird while a Jet Ranger will project sound 2,500 feet.
Yaw Authority
The 520N has the same yaw authority as a 500 D with a four bladed tail rotor.
The 500D with a two bladed tail rotor is probably better for sling loads.
Easy to Fly
I find the 520N is easier to fly than the 500's due to the YSAS. With the YSAS
turned off it flies like a 500D with a four bladed tail rotor. One can set the
pedals to neutral on a 520N lift off fly a pattern and land without any pedal
input.
Power compared to Tail Rotor 500's
The 520N could use a bit more power, but it sure beats the heck out of a Jet
Ranger (plus it does not have all the problems a jet ranger has with the
tittering rotor system, i.e., sensitive to cg changes, not very maneuverable
etc.) The 520N can certainly out climb, turn and fly a Jet Ranger.
Military Use
Just because the Army did not buy the 520N does not mean it is not a good
machine. The Coast Guard is operating 902N for drug interdiction.
Summary
Is the NOTAR a perfect helicopter? No. But it sure is a great machine and
better than some other light helicopters. If you are transporting people in
and out of confined areas or noise sensitive areas, it is the best machine. If
you a sling operator it may not be the best but it works pretty good, ask
Helimax in Montreal (they operate 7 MD 520N's) including sling loading with
the 520N.
The NOTAR needed some refinement when it first came out to the market, plus
they were over priced. After serial number 23 on the 520N the pitch angle was
changed on the fan and that was just what the 520N needed and Allison got
better at making the C20R. The 600N needs a YSAS and the factory is working on
one. Many people seem not to like the NOTAR, but they are not the ones flying
them. The 520N and the 900's are very good helicopters and I have not met a
pilot that has flown either that was not impressed. The 600N is a great
machine but I would wait until the YSAS is developed before I bought one.
P.S. I do not work for or with MD. The above is just from my experience with
the 520N and limited experience with the 600N. I was in the market for a light
turbine helicopter and I researched the Bell and MD products and decided the MD
520N was best for me. I did my training in the Jet Ranger thus I was not
biassed from early experiences. One thing I really noticed that I only heard
very positive comments on the 520N's from those that flew them and very
negative comments from those that did not fly them. I am glad I bought a 520N.
Craig
Shaber CJ
From: shab...@aol.com (Shaber CJ)
Date: Sat, 18 December 1999 04:44 PM EST
Message-id: <19991218164421...@ng-cq1.aol.com>
<Dan Hollenbaugh
Dan & Jan Hollenbaugh
limited experience and even more limited engineering education, who prefers
a single type he's gotten used to. That's not an argument I can ever
win.......
I am, however, very insulted by the "company line" tag. I wonder - I talk
about years of fighting the bureaucracy to stop a program, and I'm accused
to toeing the "company line"? Oh, well - one thing I learned early in
dealing with newsgroups - The ability to post to a newsgroup does not
automatically cannote intelligence. Now you all know why I don't post very
often.
Dan H.
Talon 26 wrote in message ...
>Thanks for the post from a current user Craig. Your info is what I am
>hearing as the norm from NOTAR users, I read a little "company party line"
>in Dan's posts, if not 10 year outdated info.
>Mark
>
>Shaber CJ <shab...@aol.com> wrote in message
>news:19991218171714...@ng-fq1.aol.com...
Talon 26
hearing as the norm from NOTAR users, I read a little "company party line"
in Dan's posts, if not 10 year outdated info.
Mark
Shaber CJ <shab...@aol.com> wrote in message
news:19991218171714...@ng-fq1.aol.com...
RonPilotPI
practical 101
> And what I read in Craig's post is the opinion of a single pilot, with
> limited experience and even more limited engineering education, who prefers
> a single type he's gotten used to. That's not an argument I can ever
> win.......
Years ago a friend of mine who was a starving graphic artist and sign
maker was so broke he lived in his shop and showered in a silk
screening clean up trough.
One day he got his biggest order to date. It was for a single pylon
free standing sign 30 feet high.
He designed it and took it to an engineer. The engineer said it was
just fine and signed it off.
My friend built the sign and up it went....... 6 six days later it bent
over and it cost my friend over 4,000 to replace at his expense.
A year later he got another large job for another free standing sign.
He designed it and took it to a building contractor with a grade 12
education and 20 years experience. Together they looked at the design
and decided where it needed to be beefed up
He skipped the engineer that time around and 16 years later the sign is
still standing.
Dan there is a lot to be said for book learning and degrees.... but
engineers don't fly helicopters.........pilots do.
Craig sounds practical - you sound arrogant and maybe that's why the
General had some other engineer look after the project.
Robert Wittmann
As I see, here are talking two different groups about the same helicopter
under different angels of view.
Dan (as an engineer) stated an analysis about the EFECTIVENESS of the
different types to provide yaw counterforce.
An other topic is to talk about the handling characteristics of a helicopter
with a NOTAR - System.
I read Craigs article (the userć„€ view) and I think it is important to know,
that there are other arguments besides tailrotor-effectiveness.
Noise reduction is one.
No danger of turning t/r blades (confined areas, ground personnel,...)
is an other.
But: All these arguments have nothing to do how easy to fly such a baby. The
crucial thing is the installed yaw stabilizing and actuating system (I hope
this is the correct translation of the abbreviation "YSAS").
When you have a h/c with such a system (as effective as Craig posted) then
it is primarily not the effectiveness of the tail rotor what the pilot
experiences ! The only thing you experience is the easyness of handling due
to the yaw stabilizing system.
Or let me explain it the other way around: Install this system into e.g. a
BO 105 and you will experience that pilot workload is greatly reduced, the
baby is easier to fly....
The next thing Dan (as an experienced engineer) told everyone is simply
statistics:
One must not try to derive a statistic from statements of less than thousand
persons. And of course not upon one single opinion.
Craig analized his personal situation and found out which helicopter
fullfills his demands - He found a MD500.
The Army analyzed their situation and found out that a NOTAR-System did not
fullfill their demands.
In the end this all sounds rather simple (even to a Non-engineer).
So Mr. practical 101s problem is, that he can not read:
1. an analysis shows that there is no difference between the engineer or
the pilot.
2. there was nowhere anything said if Dan is a pilot or not.
3. who told you that engineers do not fly helicopters? Short example:
Every test-pilot needs a diploma in mechanical/aeronautical engineering
and some 1500h on different types of a/c to get a licence.
4. Dans arguments are true (both, on the desk and in practise).
5. The Armys reasons are different from Craigs and these differ from
those of other users.
And in conclusion: The same thread can be drawn about the French FENESTRON -
tailrotor system.
With kind regards from Bavaria,
Robert
Robert W. Wittmann
University of The German Armed Forces - Munich
- Aerospace Engineering-
German Army Aviation
Eric W Braeden
Do you have any figure on the fuel burn rate of the NOTAR vs. conventional
TR?
Eric
Dan & Jan Hollenbaugh
Note to self: Remember that there are intelligent alternative viewpoints,
and keep sharp tongue in mouth.
Dan H.
Robert Wittmann wrote in message <385cd...@news.unibw-muenchen.de>...
Shaber CJ
you have as PIC in NOTAR aircraft?
I am not saying they are the best thing since sliced bread. It is just they
are very good helicopters and after a few teething problems they have proven
the design.
Shaber CJ
>Do you have any figure on the fuel burn rate of the NOTAR vs. conventional
>TR?
Mine burns 24-28 gallons per hour, depending on torque. At 28 gallons an hour
I am fly 120 kts (70 psi)
Shaber CJ
<shab...@aol.com>>Well, a very interesting article.
However, you are wrong on many points: (I)
>The market place has accepted the NOTAR; (2) MD Helicopter bought the 500,
600
>and 900 series from Boeing (yes this includes the 520N, 600N, 900N and the
>902N, all NOTARs). Last year MD Helicopter sold 65 aircraft, five were
>traditional tail rotor and the rest NOTARs. MD has orders for over 100
>helicopter to be delivered in 2000 all but six are NOTARs. (The above
>information is as remembered from an article in Aviation Weekly or Airborne
Law
>Enforcement.)
And how many of these were due to "rebates" from this new company, stuck
with that bad technology and still trying to sell it?
>
>There are many reasons the NOTAR is a great system beside the obvious of
not
>having a tail rotor spinning at high RPM:
>
>Tail Rotor
> Just think of all the accidents caused by a tail rotor failure or strike.
The
>NOTAR has eliminated these accidents.
You didn't read what I wrote - I said, if tail rotor strike is an overriding
concern, then NOTAR is a good idea. In the case of tail rotor failure, the
NOTAR, with its internal fan driven off the MD 500 tail rotor take-off, is
just as susceptible to failure of its shaft-driven fan as a tail rotor
equipped aircraft.
>
>LTE
>Just last week there was a discussion of LTE while OGE hover down wind.
The
>NOTAR does not suffer from LTE. I have hovered the MD 520N downwind
with a
>17 knot wind, and it is stable as a rock. I believe the 600N is not as
good
>downwind but it sure beats tail rotor aircraft. The NOTAR can get a right
yaw
>when the airflow breaks away from the tail boom in a right descending turn
with
>almost no airspeed. Just add maybe 5 knots airspeed and the flow
reattaches.
>
LTE is normally caused by a transitory aerodynamic effect. We fly the
Comanche sidewards at 80 knots, and it does not suffer LTE either. I don't
recall any problems with tail-rotor equipped 500s suffering LTE either. So
NOTAR solves a problem that never existed in the Hughes 369 / MD 500 series
to begin with.
>Safety
>Check the NTSB web page and you will find two accidents with MD 520N. The
520N
>just suffered its first fatal accident due to a high side governor failure
>(there are over 100 flying). The other accident is really an incident
where a
>couple of blades hit the boom while shutting down downwind and letting the
>rotors coast to a stop. There have been no failures of the NOTAR system.
How
>many tail rotor failures are there a year (i.e. a sweater blows out he door
and
>wraps around the tail rotor etc.)
And what was the comparable accident rate with the 500 series with standard
tail rotor? Partial statistics are meaningless.
>
>Noise
>The NOTAR is 50% quieter (actually measured) than a similar helicopter.
When I
>over fly people, horses, cows whatever, they will not look up until I have
>almost on top of them. At a125 KIAS the 520N will project sound 500 feet
in
>front of the bird while a Jet Ranger will project sound 2,500 feet.
>
Actually measured under what conditions, at what range, azimuth and
altitude? At what relative angle to the helicopter - nose on or tail on?
Again - partial statistics are meaningless. If you were an engineer, you'd
understand this. You sound like a salesman....
>Yaw Authority
>The 520N has the same yaw authority as a 500 D with a four bladed tail
rotor.
>The 500D with a two bladed tail rotor is probably better for sling loads.
>
Define yaw authority. Total force from trimmed forward flight? Total force
from hover? What's the damping ratio?
>Easy to Fly
>I find the 520N is easier to fly than the 500's due to the YSAS. With the
YSAS
>turned off it flies like a 500D with a four bladed tail rotor. One can set
the
>pedals to neutral on a 520N lift off fly a pattern and land without any
pedal
>input.
So why did the Army give back its NOTAR-equipped MH-6 aircraft?
>
>Power compared to Tail Rotor 500's
>The 520N could use a bit more power, but it sure beats the heck out of a
Jet
>Ranger (plus it does not have all the problems a jet ranger has with the
>tittering rotor system, i.e., sensitive to cg changes, not very
maneuverable
>etc.) The 520N can certainly out climb, turn and fly a Jet Ranger.
>
I'm not comparing the 520 to a jet ranger, I'm comparing it to a 500. This
does not help your case.
>Military Use
>Just because the Army did not buy the 520N does not mean it is not a good
>machine. The Coast Guard is operating 902N for drug interdiction.
>
The USCG flies many things no one else does, because they can't afford
better. What sort of cost incentive were they offered?
>Summary
>Is the NOTAR a perfect helicopter? No. But it sure is a great machine and
>better than some other light helicopters. If you are transporting people
in
>and out of confined areas or noise sensitive areas, it is the best machine.
If
>you a sling operator it may not be the best but it works pretty good, ask
>Helimax in Montreal (they operate 7 MD 520N's) including sling loading
with
>the 520N.
SUMMARY: You're just another pilot, with good information from your own
limited experience, rather than an engineering education, 20 years of
experience with different design concepts, and a deep appreciation of all
that goes into the development and purchase of a total helicopter system.
Study some more, fly some more types, and get back to me.
>
>The NOTAR needed some refinement when it first came out to the market, plus
>they were over priced. After serial number 23 on the 520N the pitch angle
was
>changed on the fan and that was just what the 520N needed and Allison got
>better at making the C20R. The 600N needs a YSAS and the factory is
working on
>one. Many people seem not to like the NOTAR, but they are not the ones
flying
>them. The 520N and the 900's are very good helicopters and I have not met
a
>pilot that has flown either that was not impressed. The 600N is a great
>machine but I would wait until the YSAS is developed before I bought one.
>
>P.S. I do not work for or with MD. The above is just from my experience
with
>the 520N and limited experience with the 600N. I was in the market for a
light
>turbine helicopter and I researched the Bell and MD products and decided
the MD
>520N was best for me. I did my training in the Jet Ranger thus I was not
>biassed from early experiences. One thing I really noticed that I only
heard
>very positive comments on the 520N's from those that flew them and very
>negative comments from those that did not fly them. I am glad I bought a
520N.
>
>
Okay, you're not working for the manufacturer. But you're working from a
limited experience and understanding of the options, and espousing the one
you're most comfortable with. Does that mean it's the best?
>Craig
>
>
Dan
I certainly did not mean to ruffle your feathers. I merely presented my point
of view from practical experience and the experience of my analysis as a buyer.
A couple of counter points: the MD 500 certainly is subject to LTE. MD
Helicopter will be selling approximately 100 NOTAR helicopters this year, and
that is after Boeing and MD miss managed the line by overpricing among other
miss-steps.
If we maintain our civility and conduct a discourse perhaps we can all learn a
bit more. We do not have to share the same opinion.
Mark
Nothing bad was meant by the "party line" comment, sorry if you took it
that way. If you read back through past posts and this thread though, I
think you will have to admit you sound like a Boeing and Comanche marketeer.
Again no offense meant by the "party line" comment.
Mark (was Talon 26)
Dan & Jan Hollenbaugh <holle...@mindspring.com> wrote in message
news:83hjfn$it7$1...@nntp9.atl.mindspring.net...
Ken Leander
I recognized right away that you were talking about NORTAR from a purely
military viewpoint. The power loss and increased target size are horrible
side effects (from a military perspective). The military benefits are
almost nonexistent. Further, the cost has to be paid for in armament,
weapons, or fuel payload given the same engine output. I think I'd do my
best to see that no military helicopter flew with NORTAR, and I'd be proud
to say so.
Furthermore, I can see why you were deeply offended by the 'company line'
crack. I would be too.
The problem is that most of the people reading this newsgroup are thinking
of GA usage of NORTAR. 60% noise reduction and safety issues more than
mitigate the loss of tail rotor efficiency. And the thought of increased
target size is of absolutely NO concern in GA. From a civilian viewpoint,
NOTAR benefits are quite desirable.
Maybe you should have begun your analysis of NORTAR with 'For Military Eyes
Only' :) Well, I hope you have learned your lesson! Few people fully
understand what they are reading or from who, and fewer take the time to
clarify or resolve misunderstandings. C'est la vie. But that doesn't mean
you shouldn't post or that you should just give up. Aviation is the
mistress you serve. And, she is worth some abuse.
If you do find the time to look up the efficiency cost of NORTAR in HP, I'd
enjoy hearing from you on that. And, I realize that MD/Boeing has probably
improved on those numbers since then. BTW the entire MD line of helicopters
what just sold to the Dutch effective this February. But, Boeing retains
NORTAR technology rights. What do you bet that the Dutch have either
cheaper labor costs, less union influence, or both?
Ken Leander
"Dan & Jan Hollenbaugh" <holle...@mindspring.com> wrote in message
news:83iuk0$d5p$1...@nntp8.atl.mindspring.net...
GReeder88
two Rotorways in your hanger ( R-22's if you prefer) and one had a NOTAR and
one did not. Which one would you fly more?
We learned turbine exhaust is not being used for safety reasons in case of
engine failure. We did not get any input on how much power is drained unless I
missed it. Also if we got shot at we might be better off with the rotor. I
wonder if I should spend the effort and build one...? Any opinions? ...haha
Jim Powell
I have not met a single pilot who considers the 520N a better helicopter than a
500E or D model. Not one. And lets not talk about the abortion 600N.
The 520Ns are quiet , maybe 5 percent quieter than 500E 4-blade tail rotor.
My local police fly a 520n and a 500E and the noise signature is insignificant
comparing the two. They are both very quiet once
they get to 500ft agl and MUCH Quieter than a 206B , many times quieter than a
AS350 and light years quieter than a 407 '"flying chainsaw".
Off subject but the 407 is the loudest and has the largest noise signature of any
light helicopter ive ever heard. Bell did not consider
the effects of noise when they designed the 407 because it can be heard twice as
far as a AS350 (not a quiet helo in any sense of the word.).
Chris Johnson
>> Wow, Craig, this HAS turned out to be one of the best threads this year.
>>Do you have any figure on the fuel burn rate of the NOTAR vs. conventional
>>TR?
>
>I am fly 120 kts (70 psi)
Craig, would you mind telling us what sorts of uses your ship is flown for?
linc
At least with a T/R and it's drive shaft it will be harder for the enemy
(not impossible) to create an emergency in war time. Bad enough when the
lead is flying, in a NOTAR one hit anywhere in the tailboom creates a
problem whereas in a T/R aircraft one hit in the boom does not necessarily
mean I'm in trouble.
Since it provided no benefit to the military, why should they have funded
it?
--
Linc
-----------
Avoid the rush, get to know God early!
practical 101 <practi...@Hotmail.com> wrote in message
news:191219990114361489%practi...@Hotmail.com...
| Dan & Jan Hollenbaugh <holle...@mindspring.com> wrote:
|
| > And what I read in Craig's post is the opinion of a single pilot, with
| > limited experience and even more limited engineering education, who
prefers
| > a single type he's gotten used to. That's not an argument I can ever
| > win.......
|
Dave Blevins
>>Noise
>>The NOTAR is 50% quieter (actually measured) than a similar helicopter.
>When I
>>over fly people, horses, cows whatever, they will not look up until I have
>>almost on top of them. At a125 KIAS the 520N will project sound 500 feet
>in
>>front of the bird while a Jet Ranger will project sound 2,500 feet.
>>
>
>Actually measured under what conditions, at what range, azimuth and
>altitude? At what relative angle to the helicopter - nose on or tail on?
>Again - partial statistics are meaningless. If you were an engineer, you'd
>understand this. You sound like a salesman.....
I don't know whether the numbers posted are absolutely correct, but I
can say that the 520N that the San Jose Police flew until its recent
demise was very noticeably quieter when flying overhead. I have heard
both types over my house and it's amazing how much less of a fuss the
NOTAR makes.
BTW re: the NTSB report on the SJPD accident - I couldn't find it -
could the poster that referenced this post the URL to it?
Dave Blevins
student (fixed wing) pilot
John
flamed out?
Dan & Jan Hollenbaugh
friction in the main rotor drive system. Besides, you'd still want yaw
control to help point the helicopter in the direction you intend to land it.
Dan H.
John wrote in message <83jvpp$807$1...@nntp4.atl.mindspring.net>...
Martin McKowen
Robert Wittmann wrote in message <385cd...@news.unibw-muenchen.de>...
> 3. who told you that engineers do not fly helicopters? Short example:
>Every test-pilot needs a diploma in mechanical/aeronautical engineering
>and some 1500h on different types of a/c to get a licence.
Good arbitration Robert. In Germany it is true that test pilots need an
engineering degree? Is this for civilian test pilots or for military as
well? It is different here in Oz!
Cheers
Marty
Matthew
>Very well-said, Herr Wittman. Thank you for an excellent summary.
>
>Note to self: Remember that there are intelligent alternative viewpoints,
>and keep sharp tongue in mouth.
>
>Dan H.
Dan, don't let the short tempered replies scare you off. I've enjoyed your
posts and I'm sure many others have as well.
Matthew.
Robert Wittmann
Eric W Braeden schrieb in Nachricht <385cf7a1$0$84...@news.voyager.net>...
> Wow, Craig, this HAS turned out to be one of the best threads this
year.
>Do you have any figure on the fuel burn rate of the NOTAR vs. conventional
>TR?
>
>Eric
>
Wow, Eric, this has turned out to be one of the longest Fullquotes this
year. !
Do you have any figure on the binary burn rate of the Normal mail-box user
vs. conventional students who do not have to pay for access ;-)) ?
With kind regards from Bavaria
Robert
When you find irony in this statement - keep it.;-)
Robert Wittmann
Hello Martin,
Thank you:-)
Martin McKowen schrieb in Nachricht
<6Hc74.5789$Dh3....@ozemail.com.au>...
>Good arbitration Robert. In Germany it is true that test pilots need an
>engineering degree? Is this for civilian test pilots or for military as
>well? It is different here in Oz!
I am only shure about our national regulations in Germany.
And here you need this awfull amount of hours, a degree in engeneering and
you have to pass the test.
There are no basic differences between the rules (military / civilian).
But what are the regulations in your country? - I' m just interested.
Cheers
Robert
linc
--
Linc
-----------
Avoid the rush, get to know God early!
Matthew <c_a...@bc.symREMOVEpatico.ca> wrote in message
news:zHi74.4929$ak....@news20.bellglobal.com...
Shaber CJ
>a
>500E or D model. Not one.
Now you have. I consider it better because it is easier to fly and easier to
maintain and safer.
Dan & Jan Hollenbaugh
in too late to participate in that, and Nick knows much, much more about the
subject than I do, anyway.
Dan H.
Eric W Braeden wrote in message <385cf7a1$0$84...@news.voyager.net>...
J. Mark Wolf
>
> The pioneers of any
> field did not have any text books to use and had to make it up for
> themselves. Therefore the pioneers had to be operators and engineers all in
> one. It is only in this latter day that we differentiate. It is a
> symbiotic, interdependent relationship and not worthy of a pissing
> competition.
>
> My two cents worth, cheers
>
> Marty
Point well made Marty. Being an engineer, I've always been dismayed at
the "them versus us" mentality between the engineering staff and the
"blue collar" staff. We're all trying to arrive at the same objective,
just from different vectors.
--
Regards
J. Mark Wolf
Pinckney, Michigan
Exec 162F N1955Z
J. Mark Wolf
>
> Well, there are exceptions. Igor Sikorsky designed and flew most of his early
> choppers. He crashed a few, but always learned something in the process. One of
> his favorite cartoons, according to son Igor Jr who sent it to me, was a person
> being dragged to a plane they designed, and he didn't want to fly it. Point
> being that a good engineer will always be confident in flying his creation,
> like Igor did.
>
I'd enjoy seeing that cartoon, could you post a jpg?
John W. Hart
design something to ride, (bicycles) if there were no riders????
John
"RW Walker" <bwalkerd...@odyssey.on.ca> wrote in message
news:83mh0k$iup$1...@mur2.odyssey.on.ca...
>
> practical 101 wrote in message
> <191219990114361489%practi...@Hotmail.com>...
> >
> >Dan there is a lot to be said for book learning and degrees.... but
> >engineers don't fly helicopters.........pilots do.
> >
> but you'll never see monkeys or bears designing and building bicycles.
>
> Bill "feels Like I work in a Zoo" Walker
>
>
RW Walker
Pardon Me
> You can go to any circus or zoo and see monkeys and bears riding bicycles,
> but you'll never see monkeys or bears designing and building bicycles.
Your quite right: ------> Monkeys and bears don't design bicycles.
Engineers do
And get as mad as you want but it wasn't a monkey that designed the
O-rings on the challenger and it wasn't a bear that couldn't convert
what was it - metric to yunno on the second last Mars probe.
And yes man would not have stood on the moon without engineers
And yes you might have to be an engineer to be a test pilot in this day
and age.
BUT------> when your strapped in with the canopy closed you'd better be
a better pilot than engineer when you ram the throttles home and lift
the wheel off the ground because when the shit hits the fan it won't be
a slide rule that gets the pilot home.
Engineers don't fly planes --------> PILOTS DO
Pilots don't design planes --------> ENGINEERS DO
There are old pilots and bold pilots but the engineers that designed
the O-rings still get to eat Xmas dinner with their family this year
DON'T THEY
RonPilotPI
Dan H.
=============================
You're right - that was a good thread also. OK - a two-way tie for Best
Rotorcraft Thread of 1999 - and the winners are 2 current Sikorsky employees -
of course!
Ron (Sikorsky fan)
RonPilotPI
Well, there are exceptions. Igor Sikorsky designed and flew most of his early
choppers. He crashed a few, but always learned something in the process. One of
his favorite cartoons, according to son Igor Jr who sent it to me, was a person
being dragged to a plane they designed, and he didn't want to fly it. Point
being that a good engineer will always be confident in flying his creation,
like Igor did.
Ron (Sikorsky fan)
Martin McKowen
RonPilotPI wrote in message
<19991220211337...@ng-fg1.aol.com>...
>>
>Well, there are exceptions. Igor Sikorsky designed and flew most of his
early
>choppers. He crashed a few, but always learned something in the process.
One of
>his favorite cartoons, according to son Igor Jr who sent it to me, was a
person
>being dragged to a plane they designed, and he didn't want to fly it. Point
>being that a good engineer will always be confident in flying his creation,
>like Igor did.
>
>Ron (Sikorsky fan)
>
>
snobbery. The people that believe that education is more important than
experience. What we try to point out is that those books that they were
educated from are written by people with experience. The pioneers of any
Dan & Jan Hollenbaugh
this thread is going to degenerate into "engineers vs. pilots", I'm sorry,
but I'm not going to play. First, I work closely with test pilots, for whom
I have tremendous respect. They go out every day and place their asses
squarely on the line we engineers draw. Second, live operational pilots are
my #1 product (my raison d'etre is their safety), regardless of their
estimate of what I know.
Let's just not go there.................
Dan H.
RW Walker wrote in message <83mh0k$iup$1...@mur2.odyssey.on.ca>...
>
>practical 101 wrote in message
><191219990114361489%practi...@Hotmail.com>...
>>
>>Dan there is a lot to be said for book learning and degrees.... but
>>engineers don't fly helicopters.........pilots do.
>>
>You can go to any circus or zoo and see monkeys and bears riding bicycles,
>but you'll never see monkeys or bears designing and building bicycles.
>
Mikko Pietilä
<robert....@unibw-muenchen.de> wrote:
>
>Hello Martin,
>
>Thank you:-)
>
> Martin McKowen schrieb in Nachricht
><6Hc74.5789$Dh3....@ozemail.com.au>...
>
>>Good arbitration Robert. In Germany it is true that test pilots need an
>>engineering degree? Is this for civilian test pilots or for military as
>>well? It is different here in Oz!
>
>
AFAIK, of the four "big" military test pilot schools three do not
require an engineering degree from the drivers. I do not know
personally any USAFTPS (sp?) graduates, but EPNER, ETPS and USNTPS do
not require that. It will help, but it is not a requirement.
Perhaps within the some services it is difficult to get assigned to a
TPS unless you do have an engineering college degree. However, we had
in the ETPS drivers with engineering BSc-degrees (aeronautical,
mechanical even chemical engineering), a guy with English history
degree and guys with no college degree as such (military academy).
IMHO there was no differences in the end product between guys with
different backgrounds. After 10+ years of flying most of the pilots
were not very current with what they had learnt in college anyway.
The pilots had to do basically all the same engineering related things
than us FTEs, although not always to the same depth. Amazing, how much
one can be made to learn in a year.
MPi
Martin McKowen
Squadrons, there is no particular requirement but an assessment that they
are capable of passing the course. From the squadrons (fast jet) I was in
we sent a guy with a science degree, one with no degree but something like
54 aircraft in his log book, and another pilot that had an arts degree (I
think). So it comes down to aviating ability. And they all said that it is
amazing how much you can learn in a year. Of these they all went to ETPS.
We do send to the other schools but I am not sure of the requirements.
Cheers
Marty
Mikko Pietilä wrote in message <385f5b9a...@uutiset.saunalahti.fi>...
Mark
first step to getting a new aircraft, the test pilot are another and the
user (pilots, mechs, ect..) is also a major contributor. The engineer
designs to the best of his knowledge applying a lot of theory sometimes. No
aircraft has been sent to a user without test pilots verifying if the
engineers were right and most often requiring design changes be incorporated
prior to the aircraft's final form as released from the factory. You don't
see many aircraft that are the same as a prototype and a production model.
Kind of like a A&P signing off someone's work on your aircraft I guess.
Mark
Dan & Jan Hollenbaugh <holle...@mindspring.com> wrote in message
news:83n50f$3jo$1...@nntp2.atl.mindspring.net...
Matthew
(snip)
>There are old pilots and bold pilots but the engineers that designed
>the O-rings still get to eat Xmas dinner with their family this year
>
>DON'T THEY
Like Ron and others have been saying, in the past, aircraft designers were
also the first to fly. Someone once pointed out that that was a Darwinian
way of perfecting aircraft design. Designers that made bad product crashed
and made no more bad product.
Matthew.
RW Walker
Martin McKowen wrote in message ...
> It is a
>symbiotic, interdependent relationship and not worthy of a pissing
>competition.
>
The best pilots are all a little bit of an engineer, whether they admit it
or not. And most of the best engineers have some piloting experience.
BW
RW Walker
John W. Hart wrote in message <83mmgs$sat$1...@holly.prod.itd.earthlink.net>...
>It is true that monkeys and bears don't design, but why would one want to
>design something to ride, (bicycles) if there were no riders????
I think everybody is taking this way too seriously. The (tongue in cheek)
point I was trying to make is that it's easier to find and train "riders",
than it is to find and train designers, builders, and maintainers.
Go to the HR department of any airplane company and ask them what they get
more of - resumes from experienced designers and maintenance techs, or
resumes from licensed pilots willing to wash floors while waiting for a
chance at a pilot job.
Bill "we're looking for a few good techs" Walker
Mark Chapman
>
> The AStar B2 has the exhaust slightly tilted to offload the tail
> rotor, but again its a small effect.
>
I guess I have to say that "I am from Missouri" on this score. I am led
to believe that this is done to separate the exhaust flow from the
tailboom to keep it cleaner. I seriously doubt that there is any
significant value added from residual thrust. As an example, the S-76A
engines produce 45 pounds of thrust each. Not diddly compared to the
10,500 lbs of helicopter.
RW Walker
Mark Chapman wrote in message <3861B302...@ns.sympatico.ca>...
>>
>I guess I have to say that "I am from Missouri" on this score. I am led
>to believe that this is done to separate the exhaust flow from the
>tailboom to keep it cleaner
You could be right Mark. After all, it was a salesman that told me about the
anti-torque effect.
BW
Lou Haas
Mark Chapman <roto...@ns.sympatico.ca> wrote in message
news:3861B302...@ns.sympatico.ca...
> RW Walker wrote:
> >
> > The AStar B2 has the exhaust slightly tilted to offload the tail
> > rotor, but again its a small effect.
> >
> to believe that this is done to separate the exhaust flow from the