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Nick Lappos on Osprey
https://warthogterritory.net/forum/viewtopic.php?f=9&t=10529		 Page 1 of 1
Author:  M21 Sniper [ 04 Apr 2006, 12:38 ]
Post subject: 
"Theories are nice."

Yes Booms, and physics are indisputable.

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<b>"One post, One Kill".</b>
Author:  M21 Sniper [ 04 Apr 2006, 13:05 ]
Post subject: 
THe money hasnt all been spent. They still want to invest 20 billion + on this aircraft(the actual production vehicles).

I say no damned way. We 'need' it like we 'need' a hole in the head.

It's speed only confers a significant tactical edge on longer missions, but air assaults longer than 50nm will preclude the use of any slung loads.

And again, the notion of Osprey facing direct fire in an LZ......


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<b>"One post, One Kill".</b>
Author:  M21 Sniper [ 04 Apr 2006, 20:45 ]
Post subject: 
Nick Lappos was a sikorsky senior engineer for decades. Is now the boss of the US EH-101 program. These comments PREDATE his work in that capacity.(15 may)

His comments are pro and con, and obviously impartial.

http://yarchive.net/air/tiltrotor.html

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.

<b>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.</b> 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.

Part 2:


Auger,
Your question is a good one. <b>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.</b>

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. <b>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</b>, which can have the rotors overlap the fuselage (like
some of the big Russian machines, like the V-12).
<b>The efficiency is directly tied to the size of the rotor disk(s)
for the weight of the machine.</b>

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.

<b>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.</b>

<b>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.</b> This fact is why some folks use a tilt wing instead of a
tilt rotor.

<b>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.</b>

Nick

Part 3:

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. <b>Specifically, given
the same power, cost and empty weight, a helicopter will carry almost twice
as much useful load as a tilt rotor.</b>

Part 5:

Nick sez:
This is where I wasn't clear enough. <b>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.</b>

Part 6:

Nick sez:

You misunderstand the problem, zrassler! <b>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!</b>

best,
Nick

Google this guy, his SCIENCE is very hard to argue with.

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<b>"One post, One Kill".</b>
Author:  boomer [ 04 Apr 2006, 21:56 ]
Post subject: 
Theories are nice.

A 45 has a muzzle.
A 9mm has a bullet vent.
Author:  a10stress [ 05 Apr 2006, 12:17 ]
Post subject: 
:?:
Author:  a10stress [ 05 Apr 2006, 15:42 ]
Post subject: 
:?:
Author:  M21 Sniper [ 05 Apr 2006, 18:28 ]
Post subject: 
Dod DID kill Osprey(2x if im not mistaken!), but Arlen overrode them.

Since there is still a MASSIVE amount of money at stake i feel it's far too soon to just give up the fight on Osprey.

Even if the buy is halved(hell, at 107 million per even a 10% reduction means billions!) it is a WIN for the USN, USMC, and USAF.


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<b>"One post, One Kill".</b>
Author:  boomer [ 05 Apr 2006, 22:45 ]
Post subject: 
This thread is just Snipes attemt to show that Osprey CANT have more range than a helo, even though all the data shows that it does.

A 45 has a muzzle.
A 9mm has a bullet vent.
Author:  M21 Sniper [ 06 Apr 2006, 01:26 ]
Post subject: 
Sorry dude, this is just a top engineers(probably one of the top rotorcraft engineers alive as a matter of fact) opinion on tilt rotor technology.

He also has an entire pdf on the subject that someone emailed me earlier tonight. I'll host N' post it tommorow.

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<b>"One post, One Kill".</b>
Author:  M21 Sniper [ 06 Apr 2006, 01:56 ]
Post subject: 
Here is Nick's extremely detailed EH-101 vs MV-22 Osprey PDF when he was heading up the US-101 team, which came in the email with this note/correction from Mr Lappos:

"I have to redo the 609 data, the range chart is off, the aircraft has about 1200 NM of range if all its payload was made into fuel. Other than that chart, this presentation is quite accurate.
Nick"

Damn....im having a problem hosting this. Anyone know a good free site to host a .pdf file? Barring that, i can email it to anyone who'd like to see it. I've yet to even read it myself.

<img src="http://i22.photobucket.com/albums/b343/m21sniper/OnTheJobEnhanced.jpg" border=0>
<b>"One post, One Kill".</b>
Author:  boomer [ 06 Apr 2006, 03:45 ]
Post subject: 
I'm not arguing with his theory, but theories often dont prove out in real life. And more to the point Osprey isnt thoereticle it's real world and comparing it to anything other than real world alternatives is pointless.

Naturally I'd like to see the report.

putfile is the only hoster I know of and for me it was very slow to upload ( I gave up ) but I have ADSL so.....

http://www.putfile.com/


A 45 has a muzzle.
A 9mm has a bullet vent.
Author:  M21 Sniper [ 06 Apr 2006, 11:57 ]
Post subject: 
Of course we can't compare Osprey to existing helos.

If we do, it appears to be inferior in all aspects but speed.
This makes perfect sense to me, as ALL vehicles designed specifically for higher speeds suffer greatly in other mission critical areas.

Cars are the same way. My 928S HAULS ASS on flat asphault(wet or dry), but you wouldn't want to take it offroading, shopping, or during a snowstorm.

All machines are compromises. Osprey is no different. To me, the compromises are too severe for what's gained. If the thing did 500kts, ok......then you'd convince me, even AT 107million per, but alas....

Post me up your current email and ill shoot the ,pdf file out to you. I havnt read it yet, but it's get lots of great pix and charts, lol.

<img src="http://i22.photobucket.com/albums/b343/m21sniper/OnTheJobEnhanced.jpg" border=0>
<b>"One post, One Kill".</b>
Author:  a10stress [ 06 Apr 2006, 14:51 ]
Post subject: 
:?:
Author:  M21 Sniper [ 06 Apr 2006, 15:23 ]
Post subject: 
B47s were truly twice as fast in their actual employment vs a B17 though, and they flew much higher in a time and doing a mission where ever higher altitude was of huge importance to the success of the mission.

The thing that really irks me about Osprey is that it is so obviously not a replacement for any existing asset, but rather an all new mouth to feed at the budget table.

A mouth that will end up eating the equivelant to almost 3 full years of the entire USMC budget(combat supplemental funding NOT included).

It's obvious that the UH-1Z and CH-46E are going to carry on in the air assault role while the CH-53D/E and eventually K continue on in the heavy lift role.

Osprey has a few niche roles it could fill really well, but all those roles combined sure as fuck aint worth 107 million per aircraft IMO.

I suspect Osprey will spend the vast majority of it's life as a medium lift cargo plane hauling trash and troops into secured LZs.

If this thing was anywhere- ANYWHERE- near as good as Boomer tries to make it sound we'd be replacing practically all our medium(and perhaps smaller) sized helos with it to get the best volume price possible.

Yet the US Army doesnt want a single airframe, and the USN only wants 48(which, btw, are completely unfunded by the USN). The USCG has placed no orders for any either. Odd if it's so great for SAR(It aint by any means IMO) The USAF says it wants 50, but they've also been slashing into all kinds of other programs to buy more raptors.

The cancellation of 50 Ospreys pays for a reinforced Sqn of raptors all by itself.........

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<b>"One post, One Kill".</b>
Author:  boomer [ 06 Apr 2006, 18:40 ]
Post subject: 
Email same as always kaptor2@yahoo.com
How big is the file?

A 45 has a muzzle.
A 9mm has a bullet vent.
Author:  M21 Sniper [ 06 Apr 2006, 19:52 ]
Post subject: 
It's small, about 870kb.

Sending it out now. Anyone else wants it, let me know.



<img src="http://i22.photobucket.com/albums/b343/m21sniper/OnTheJobEnhanced.jpg" border=0>
<b>"One post, One Kill".</b>
Author:  Krieger [ 06 Apr 2006, 20:10 ]
Post subject: 
I've yet to see the Marines be able to justify the 300-400% price premium over readily available and capable alternatives (MH-60S for example at about $28m per) for just the extra speed. Perhaps as a supplement to an HMM fleet of SH-60s' sure, but not as the entire replacement of the HMM fleet - not only is that fiscally iressponsible (all the more so considering that you still need to find funds to modernize your rapidly aging HMH fleet of '53E's) it's potentially detrimental to the Marines ability to "fight" (aft mounted mini-gun on a ramp about 1/2 to 2/3's the width of a 53 or 47) their way inland.
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