From: nlappos@bellsouth.nospam.net
Subject: Re: V22 Opsrey Question
Date: 15 May 2000
Newsgroups: rec.aviation.rotorcraft

 guru2@null.net wrote:
stuff snipped
>
>The only other obvious question is purely rhetorical:  Since I see no
>reason why the V22 should be any more dangerous than any other
>helicopter with multiple main rotors, and there are obvious advantages
>in speed and presumably in radius of opperation, why wasn't it developed
>at least 15 years earlier?
>
>Thanks for any enlightenment.
>
>Pete


Pete,

The successful development of tilt rotor technology depended on two important
technologies that were of sufficient maturity to allow the XV-15 to be the
success that it was:
1) Engines light enough, yet powerful enough to lift the machine. Tilt rotors
must have small highly loaded disks, unlike multi rotor helicopters whose
disks stay above the aircraft, and don't have to swing past the fuselage.  For
this reason tilt rotors need about half again more power than helicopters to
lift the same payload, so the engines must be light, and efficient.  While
demo aircraft were possible in the past, only now can the modern turbines
allow a practical production tilt rotor.

2) Theoretical computation to control the dynamic interactions that exist
between the rotors and the wing.  Without the excellent computers available
today, the search for acceptable aero-elastic solutions would take very
expensive and time consuming trial and error.  The limiting factor in all
early tilt rotor vehicles was the interaction of the rotor frexquencies with
the wing, creating resonances in many flight modes.  The XV-15 and now the
V-22 are reported to be quite free of such worries.  An important other
technology is the composite structure which allows tuning the wing and rotor
structure to avoid these interactions with relative ease.

I must comment that any given tilt rotor has LESS range than a helicopter with
the same power, cost and empty weight.  This is because the tilt rotor starts
off with half the payload, and so even though it is quite efficient in cruise,
it carries so little payload relative to a helicopter that it never catches
up. The tilt rotor has a significant speed advantage, of course, probably at
least 75 knots and perhaps as much as 125 knots (150 to 160 for a helicopter,
225 to 300 for a tilt rotor).

You have already seen responses as to yaw control, which is done with
differential cyclic control.

Nick

From: Nick Lappos <nlapposNOnlSPAM@miami.gdi.net.invalid>
Subject: Re: V22 Opsrey Question
Date: 16 May 2000
Newsgroups: rec.aviation.rotorcraft

"auger" wrote:>
>With such a general statement about the limitations "any given" tiltrotor
>(as opposed to "any given shipborne" tiltrotor, I trust in your range
>calculations you are using a tiltrotor without the V-22's shipborne
>requirements of:
>
>wing & blade stow gearing and motors (adding weight),
>wing length limit (affecting efficiency in airplane mode) and consequent
>prop length limitations (affecting both lifting capacity, speed and range).
>

Auger,
Your question is a good one.  The V-22 and the H-53E have similar
 systems and penalties for Marine shipboard operations, and the
generalization that the helo will beat the Tilt Rotor in range is
accurate for that comparison.

The wing length and prop length issues for the tilt rotor are
really layed out by its basic geometry, not by any shipboard
requirements.  For the rotors to be at the ends of the wings, and
then convert to props, the rotors must not come too close to the
cabin.  This sets the size of the rotors for all basic tilt
rotors, and makes them small and highly loaded disks, and
therefore less efficient by about 40% than an equivilent
helicopter, which can have the rotors overlap the fuselage (like
some of the big Russian machines, like the V-12).
 The efficiency is directly tied to the size of the rotor disk(s)
for the weight of the machine.

Also, if the wing on a tilt rotor is too long and thin, it
becomes a real elastic nightmare for avoiding the various
resonance modes that I touch on in the post above.  These
modes are kind of like the pylon rock some helicopters
exhibit.  The rotors can begin to pump themselves, twist the
wings and feedback in resonance.  The shorter,
lower aspect tilt rotor wing is quite a bit stiffer, and is less
prone to resonances, that is why it is used on the V-22 and the
XV-15.

Tilt rotors have very high drag on the wing in a hover, where the
downwash on the wing is "felt" as extra weight and therefore lost
payload.  On a helicopter, we package the fuselage tightly to
keep the vertical drag down to about 5% of the total weight,
which means that a 50,000 lb helo has about 2,500 pounds of lost
payload due to downwash.  A tilt rotor wing is flat and big and
completely exposed to the high speed downwash, making the penalty
of vertical drag at least 10% of the gross weight.  Therefore,
for a 50,000 lg tilt rotor, the lost payload is twice that of an
equivilent helicopter, a difference of perhaps 2,500 pounds or
so.  Thjis fact is why some folks use a tilt wing instead of a
tilt rotor.

All this fits into the sweeping statement I made, which is true
for helos vs tilt rotors, that with the same power, cost and
empty weight a given helicopter will have more range that a tilt
rotor, but of course much less speed.

Nick

From: nlappos@bellsouth.nospam.net
Newsgroups: rec.aviation.rotorcraft
Subject: Re: V22 Opsrey Question
Date: Sun, 21 May 2000 14:52:38 GMT

 "zrassler"  wrote:
>

>
>What penalties does the  H-53 suffer from being ship-borne? Added weight for
>a motor to stow its blades? Don't think that would compare to a motor and
>gearing on the V-22 to stow its wing and the blades on two engines.

Nick sez:
 On the H-53 series, the whole tail section folds automatically, after the
tail rotor is disconnected and motored into correct position.  The main rotor
is indexed, the pitch of the blades are all locked with special mortorized
pins, and the head is rotated into position by a special motor.  All
automatically, and all in winds up to 45 knots.

I think you are trying to explain the tilt rotor's shortfall in payload as
something to do with shipboard issues, and it won't wash.  Specifically, given
 the same power, cost and empty weight, a helicopter will carry almost twice
as much useful load as a tilt rotor.

zrassler sez:
>It seems to me that helicopters are well-suited to ship-borne operations
>because they don't have to have wings to stow. There is a greater weight
>penalty when adapting a tilt-rotor to shipborne operations.
>
>I am not saying it is unfair to compare the two aircraft in shipborne
>configuration. I am just saying that the performance of an Osprey would
>improve much more if it was designed to be land-based than any performance
>gain a naval helicopter would get by being designed from the start to be
>land-based.
>
>Therefore, I still contend that your statement was too general. Admittedly,
>I can only speculate on the performance of the Osprey without all the naval
>bells and whistles.

Nick sez:
I'll be glad to prepare a comparison of the 609 and a Black Hawk, if you'd
like!  The comparison stays the same, equal weight, power and cost the
helicopter carries twice as much, and goes farther.

>The distance from right outer blade tip to left outer blade tip was limited
>by naval requirements. Once the designers had that limitation, I believe
>this distance was based on the diameter of a presently used helicopter
>model's blade diameter, they designed the wing and the length of the blades
>based on that limitation.
>
>The whole damn plane was designed from the start based on naval
>requirements.
>
>What "basic geometry" are you talking about?

Nick sez:
This is where I wasn't clear enough.  If you lay out a tilt rotor to fit any
given area of deck space, it will have two very small rotors as compared to an
equivilent helicopter.  That is beacuse the two disks must not touch the
cabin, so they must be small.  Generally, a tilt rotor must have only about
40% of the rotor disk area of an equivilent helicopter, which means that ot
will need about 50% more power for the same payload (or that it will have much
less payload for the same power).  This is not salesmanship, zrassler, it is
physics.

Zrassler sez:
... But longer wings can be stiffened, adding cost of course.
>
Nick sez:
And pigs can fly, too, if we put a big enough engine on them.  The cost trades
have been made, zrassler, and V-22 and 609 have small short wings that provide
good performance without worries about aero-elastic resonances.

Zrassler sez:
>
>Makes sense. Longer wings and longer props would cause an increased loss of
>efficency proportional to the increase in the area of the wings immediately
>below the props. However, there would be a greater increase in the area
>below the props outside of the shadow of the wings. So performance would
>impove in helicopter mode if you could lengthen the wings and props. So what
>do you think the performance would be like in airplane mode with longer
>props and wings? And this is primarily where the tiltrotor gets its range.

Nick sez:
There is no wing on a tilt rotor that is not under the rotor disk.  If the
rotors were so small that it were otherwise, then the hover efficiency would
be even more atrocious, and the payload and range would suffer more.

zrassler sez:
>Your points are good about the "inefficiency" of lifting a weight straight
>up and letting it down. So I agree that a tiltrotor, unless it found a way
>to bring its wings into the 5% lift retardation effect of the modern
>helicopter, will never be as good a lifter as a helicopter. Obviously, if
>you flew an Osprey all the way to its target in helo mode you would have
>less range. However, tiltrotor gets its range in airplane mode, it only uses
>helo mode to land and take off. How can you extrapolate this lifting
>advantage of a helicopter into "range" without calculating power saved by
>using the lift generated by the tiltrotor's wings to keep the plane aloft?

Nick sez:

You misunderstand the problem, zrassler!  If the tilt rotor has less useful
load in its hovering takeoff, it can't carry the fuel to get the range.  The
awesome panalty of having only half the payload of a helicopter means that the
tilt rotor starts with one foot in a hole.  It takes off with half the payload
for the same power and cost, so it can carry only half the fuel.  Even tough
it is more efficient in cruise (and surprisingly, only a bit more efficient)
it never gets to go as far as the helicopter, because the helo can take off
with more fuel!

I will post on my web site some slides that explain this better.  Please look
for a post with a pointer to that web site a little later today, OK?

best,
Nick

From: nlappos@bellsouth.nospam.net
Newsgroups: rec.aviation.rotorcraft
Subject: Re: V22 Opsrey Question
Date: Sun, 21 May 2000 16:09:13 GMT

 nlappos@bellsouth.nospam.net wrote:

>I will post on my web site some slides that explain this better.  Please look
>for a post with a pointer to that web site a little later today, OK?
>
>best,
>Nick


Here is that site:

http://personal.mia.bellsouth.net/mia/n/l/nlappos/tiltrotorcomp.htm

From: nlappos@bellsouth.nospam.net
Newsgroups: rec.aviation.rotorcraft
Subject: Re: V22 Opsrey Question
Date: Sun, 21 May 2000 19:12:21 GMT

In article <z9WV4.34994$au2.382438@news1.rdc1.bc.home.com>, "Matthew" <c_and_m@bc.symREMOVEpatico.ca> wrote:

>
>Nick, of course a small amount of knowledge is a dangerous thing, but I used
>your numbers to try put the airspeed advantage into the mix.  I think this
>is fair to do because while helicopters will continue to exist, there are
>missions that the tiltrotors will command.
>
>Lets say we want to move 60,000 lbs to a place that's 700nm away.  I choose
>700nm because this forces the Osprey to take 6,000 lb loads while the H53 is
>allowed to take 10,000 lb loads.  This gives an advantage to the H53.  Wind
>is calm and turnaround times are negligible ('cause the Marines are so
>keen).
>
>V22 completes the mission in 25.5 hours.  H53 completes it in 28 hours.
>
>This is considering only one machine of each type, if there are 6 of each
>machine then the H53 finishes the mission in 4.7 hours and the V22s finish
>it in 7.6 hours.  With 10 machines the V22 finishes it in 1.6 hours.
>
>
>Now I'm going to change the mission.  We only have to move the 60,000 lbs
>500 nm away.  I had to make an assumption that the 4,000lb difference in the
>two max range values was fuel required for 100nm for the V22 and 150nm for
>the H53, and then I extrapolated that value to make a max payload at 500nm
>range of 14,000lb for the V22 and 16,000lb for the H53
>
>V22 completes the mission in 9 hours.  H53 completes it in 13 hours.
>
>If there are 6 machines of each type then V22 completes mission in 1.8 hours
>and V22 completes it in 3.3 hours.  (Actually require 5 V22's and 4 H53's).
>
>
>Of course, you must consider getting the resources back to do another
>mission.  V22's will be back soonest, I assume the turnaround times will be
>similiar, so that consideration benefits the V22's.
>
>Like Simmsac said, you can't compare apples to oranges.  I picked this
>mission to demonstrate a usefullness of the V22.  I tried to give the
>benefit to the H53 in many places, but still couldn't get the H53 to win.  I
>have no doubt that there are many missions where the H53 will win over the
>V22, that's why the 53's are staying.
>
>I did this quickly, so my math may be wrong, but I think it's close enough
>to illustrate the point.
>
>Matthew.
>
>
Matthew,

Good work and good argument!

You are not wrong (although I think you mixed up the V-22 and 53E labels in
your paragraph 7 above)  What we are now doing, at least, is using the facts
to establish a premise!

What is next needed is to work out the economics of doing it, with the cost of
the machines, their support and manpower in the mix.

Whenever DOD did that, the V-22 lost, but it was bulled through by Congress,
anyway.

In terms of purely per machine, the argument is nearly a wash, as you show,
with some preference for the V-22.  When worked out per dollar, there is no
contest, a helicopter wins.  I am really pleased to see that at least now we
don't see that the V-22 "carries twice the load twice as fast as a
helicopter".

Thanks for making the next leap in a true operations analysis approach
to the problem.  Some details to now be sure what we are doing is valid.  The
Boeing site carries the V-22's hover weight as 47,500 pounds where the Bell
site sez 52,780.  The difference is that Bell is publishing the standard day
capability, while Boeing is more correctly using the "Marine Hot Day"
capability (3000 feet and 90 degrees).  Run your numbers again, using the
actual capacity of both machines at the Marine Hot day, and see how the V-22
does!

Also, the use of 275 knots in normal cruise may not be justified.  This is a
peak speed, and needs to have the aircraft at 25,000 feet!  What would it be
for a real tactical mission?  Boeing lists the 275 knots as Max speed, and I
have seen Vbest range listed at 225 knots.  I also know that the range data
published by Bell is not at 275 knots (some manufacturers are good at
publishing all the high points, without explaining that you can't get them all
at the same time).  What would the analysis give at 250 knots?

Also, the H-53E data is for a fielded aircraft, with a full operational set of
equipment, and a real flight manual to establish the actual capabilities.  I'd
really be interested to know what the V-22 flight manual sez!

Anyway, good answer, Matthew!  Unlike Simmsac, who just lumps things into
"their own mission" so that little actual analysis (thinking) is required, or
previous posters who asserted that the 53E is "heavy lift" and therefore
disqualified from consideration (as if a rotorcraft with 13,000 horsepower
like the V-22 is medium lift! LOL!)

Nick Lappos

From: nlapposNOSPAM@snet.net
Newsgroups: rec.aviation.rotorcraft
Subject: Re: Aviation Week Mag on Troubled V-22
Date: Fri, 05 Jan 2001 00:03:00 GMT

In article <932b5c$j4o$1@nnrp1.deja.com>, Darin Ninness <dninness@numega.com> wrote:
>  ronpilotpi@aol.com (RonPilotPI) wrote:
>>   From this week's Aviation Week magazine:
>>
>> V-22 Hydraulic Woes Strike Again
>> ROBERT WALL/WASHINGTON
><snip>
>
>Hmmm.. so what they're saying is, lose a single flight control
>actuator, lose the ship?
>
>I got two word for ya Ron: stabilator actuator.
>
>Darin
>The Boeing Bigot

Darin,

At least try to be an accurate bigot!  This ancient Black Hawk urban legend
needs correcting yet again.

The H-60 family has had two accidents where the stabilator was implicated.
One involved a maintenance error where airspeed info was disconnected from the
system, and the other involved flight into icing conditions with no pitot heat
on, where the airspeed indications fell to zero and the crew did not
understand what was occurring.

No stab failure per se has caused an accident, but the urban myth persists....

Regarding the propensity for hydraulics to cause full control failure, I
believe that the V-22 has all the protection that good helicopters have - dual
systems with a third back-up.

Where the typical tilt rotor might be more exposed is that it has a bunch more
control actuators than either a helicopter or an airplane.  I list here the
actuators (which are actually all dual) - six for the main rotors, two for the
tilt mechanism, and a full set of airplane control actuators, too, probably 2
aileron, 1 rudder, 1 elevator.  That's 12 dual (24 pistons and valves!) all
tolled.  A typical helicopter has 3 main rotor and one tail rotor as primary
controls, for a total of 4 actuators (8 pistons and valves).  That makes a
failure of a critical control three times more likely in a tilt rotor.

Buy Parker Bertea stock, I say.


Nick Lappos
Still a believer in high speed tilt rotorcraft

From: nlapposNOSPAM@snet.net
Newsgroups: rec.aviation.rotorcraft
Subject: Re: Aviation Week Mag on Troubled V-22
Date: Sun, 07 Jan 2001 04:22:01 GMT

In article <938i09$jab$1@nnrp1.deja.com>, Darin Ninness <dninness@numega.com> wrote:
> It just seems strange that just
>2 "stabilator-implicated", not stabilator-caused,  accidents would
>result in the restriction of the entire fleet of UH-60s to the
>old "80kts or less below 3000 ft" for several years until they could
>fix the system. (supposedly)
>
>  Now, fault me for falling victim to an "urban legend," but I got that
>stuff straight from the UH-60 guys in 201st Aviation Company, Camp
>Humphreys, Korea, so that was the stuff coming out of the Blackhawk
>community in the mid-late 80s
>
Nick Sez:

I agree there was lots of smoke and thunder once upon a time. The safety
guys within the Army were predisposed to ground the aircraft after each
accident, and the stabilator was always a hot suspect (it always seemed that
the rumors became real that way.  Agent Orange, anyone?), but the causes were
always found to be the rather less exotic (bolts left out of the flight
controls, etc.).  When the causes were found, the aircraft was ungrounded, but
nobody ever made the apology speach to the poor stabilator.

The flight restriction was, I believe, caused by one case of documented EMI
that never affected the stabilator (it did cause some hydraulic lights to
blink!), but caused some concern. The ECP that banished the EMI  (lots of
filtering for the electrics) also lifted the restriction.


Darin sez:
>Like that old saw about twin engine airplanes:  A piston twin is twice
>as likely to experience an engine failure than a piston single, because
>there is twice as much to go wrong. (Any statistician would probably
>tell you that's not entirely accurate, but its one of those rules of
>thumb that persists..)

Nick sez:
The only problem with that analogy is that when an engine quits (twice as
often in a twin as a single), you come down under control. When a flight
control servo (both sides) quits, its a different game, with a noisier
landing.

Darin sez:
>Thanks for the insight, Nick.  Keep it up.

Nick sez:
That's what I like about RAR, Darin!  Stay a "Boeing Bigot".  I worked with
their Comanche team for years, and they are good guys!  Too many rotors, of
course, but still  ;-)

Nick

From: nlapposNOSPAM@snet.net
Newsgroups: rec.aviation.rotorcraft
Subject: Re: Aviation Week Mag on Troubled V-22
Date: Sun, 07 Jan 2001 04:25:59 GMT

In article <20010106214134.20043.00000205@ng-fm1.aol.com>, shabercj@aol.com (Shaber CJ) wrote:
>>From: nlapposNOSPAM@snet.net
>>
>....
>>
>>The H-60 family has had two accidents where the stabilator was implicated...
>
>
>Dumb question, but is the H-60 fly-by-wire?
>
Nick sez:

No such thing as a dumb question, but I have seen some dumb looks once or
twice, Shaber CJ!

The aircraft controls are conventional.  The stabilator is a dual, compared
electric system.  It detects its failures, freezes in place and sounds a
caution to the crew.  The crew has a slew switch on both cyclics to bring it
up to the high speed position.

Nick

From: nlapposNOSPAM@snet.net
Newsgroups: rec.aviation.rotorcraft
Subject: Re: More Great Journalism For The V22 (NOT!)
Date: Tue, 16 Jan 2001 02:09:28 GMT

In article <94067t$fu9$1@nnrp1.deja.com>, jww45@my-deja.com wrote:

>Thanks for the post Chuck;
>
>I wonder who the Bush senior moron is?  Ronnie/Ronpilot?  Bush is
>following the tried an true method:  If your stupid, surround yourself
>with people that make you look smart.
>
>Back to helicopters:
>
>What helicopter in service can go 280 mph with a useful load and a
>range more than 30 miles?  Obviously this a minor thing.
>
>What helicopter (of any kind: experimental or otherwise) has gone 280
>mph without having to be rebuilt?
>
>If anyone says the Sikorsky ABC (I am not sure they ever got that fast)
>you should consider that they lost 50% of those in testing.
>Interesting side note:  When the XV-15 was demonstrated at the same
>time as the competeing ABC at Ft. Rucker the XV was flown in and the
>ABC was trucked in.  I heard from people there that the they still have
>damage to their ears from the ABC due to the jet noise.  By the way
>this ship could not hover with full fuel.  What a slick concept.
>
>JWW45
>

Dear JWW,

Boy are you off base!

You said, " When the XV-15 was demonstrated at the same
>time as the competeing ABC at Ft. Rucker the XV was flown in and the
>ABC was trucked in."  Not very true, and I know, because I flew the ABC into
Ft. Rucker!  What else have you got wrong?

" By the way this ship (ABC) could not hover with full fuel.  What a slick
concept."  In fact the ABC is about 50% MORE hover efficient than the Tilt
Rotor, due to its highly efficient counter rotating rotors.  The experimental
ABC used thrust engines to get it to 300 mph (without even needing a rebuild!)
and it had two small PT-6 engines that wouldn't let it hover with a full bag
of gas. A production ABC would have no such limits, as it would not be a
flying wind tunnel, as the XH-59A was.

You didn't mention that the  XV-15 design started life with PT-6 engines,
which guaranteed that it would not ever hover. The Bell guys wisely delayed
the program, re-engined it with T-53's (because of the awesome power hunger of
the tilt rotor design) and gave it 40% more power.

You missed the key point of the article that you criticized.  The requirement
to cruise at 300 mph was key to the selection of the tilt rotor, but was never
based on any demonstrated need.  At only $80 million a copy, it comes out to
$266,000 per mph.  Wow!  Glad that's not My money... Wait, it is!

Nick

Date: Sun, 28 Jan 2001 02:51:15 -0500
From: Nick Lappos <nlapposNOSPAM@snet.net>
Newsgroups: rec.aviation.rotorcraft
Subject: Re: Even MORE V-22 commentary

Bob Barbanes wrote some good stuff about V-22 doubts. (all snipped)


Bob,  here are some of my thoughts.

I have a pretty good understanding of the strengths and weaknesses of
helicopters, and of tilt rotors, and I do think the V-22 needs a chance
to continue its development, but part of the problem is the tremendous
build-up it was given.  I think it has become victim of all the hype its
supporters generated in the last two decades.

1) It does not carry more and go farther than a helicopter - Hypers of
tilt rotors do nobody a favor when they say "twice as far and twice as
fast as the helicopter it replaces."  While the statement is technically
true and also misleading, we should thank God they weren't replacing the
venerable H-46 with a Boeing 747, or they'd run out of multiples.  In
truth, a tilt rotor has only about half the payload of a helicopter with
the same power and empty weight, and it barely goes as far as that
helicopter.

2) Its speed does not let it survive at any higher rate than a helicopter
- Again, the hypers try to believe that 250 knots is some panacia for
survival, which would mean that C-130's are invulnerable.  The premise is
absurd, of course.  Survival is aided by either flashing by at near the
speed of light, or moving carefully while staying behind cover and
concealment - as in NOE tactics.

3) Its maneuverability is barely that of a loaded transport airplane.
The hypers used to show armed tilt rotors flashing by, guns blazing, and
argue that speed is life.  Yet the Yuma accident was pilot error because
the pilot went down faster than the 800 feet per minute restriction?  How
among us has not descended a loaded helicopter faster than that at 40
knots?  The absurd posts in this thread that try to compare the limits of
touchdown speed (which is determined by how strong the landing gear is)
with the propensity of a tilt rotor lose control is a real retreat from
all those armed V-22 pictures, huh?

I hope several things come true in the weeks ahead - that the V-22
continues, at a pace that allows it to be fully understood, that I don't
hear any more about how crappy helicopters are because tilt rotors will
replace them all, and that this newsgroup finds other stuff to talk
about!

Nick