The Ship Model Forum

by **Mark Petersen** » Wed Feb 13, 2008 4:55 pm

chuck wrote:
Mark Petersen wrote:I still can't believe we let a similiar capability slip through our collective fingers 40+ years ago

http://www.helis.com/50s/h_rotdyn.php
The capability that slipped through our fingers always looks good in retrospect because there was no time for any problems to manifest themselves. If Osprey had been canned in 1987, you will be crying a river of tears over the supposedly vast potential that we "let through our fingers".

Actually if the Osprey had been canceld in '87 I doubt I would be crying in my beer or acting as the font of a mighty stream. IMO the Osprey violates the basic priciple that all machines should be designed to. Keep it as simple as possible to do the given job. What happens on the Osprey when the tilt mechanism fails (and they will somewhere along the line). At the minimum you are going to lose the rotors, possibly the whole airframe and crew/passengers. Plus with the Osprey add in the cross shafts, gearboxes etc. Granted the Rotodyne was a compromise, but then any aircraft designed to function as a plane and helicopter will be. The Rotodynes tip jets functioned off of compressed air run by the turbines. There was no mechanical linkage to the engines period. Even if both engines failed it could still autorotate to the ground. And both engines clutch systems failed to spin up the compressors then it could still land on a runway like a conventional plane. If such an aircraft was being designed today I suspect that the rotor would be driven by bypass air from TurboFans with the TurboFans taking the place of the turboprops. The Rotodyne had its problems (noise being one of them) but the British decided not to continue development. I sometimes think the people who decided which aviation projects to cancel and continue in Britian in the late 50s early 60 were Soviet agents.

by **j leyland** » Sun Feb 10, 2008 8:38 pm

The current USNI Proceedings contains an article reporting the first deployment to Iraq. The tone seems to be a reasonable effort for a first deployment. How many tech reps do you think will deploy with the first unit of STOL F35's?

by **Tracy White** » Sun Feb 10, 2008 6:38 pm

It wouldn't lose lift, it's just not an airfoil designed to be efficient at that speed.

The main problem with helicopters is that different sides of the rotor "disc" produce different amounts of lift due to speed of the airfoil and the relative wind caused by flight speed and wide direction. This is alleviated somewhat by allowing the rotors to "flap" up and down as their lift values change.

A compound helicopter, with its fixed wings, can off-load the rotor disc so that this is not as much of an issue. It still will be an issue unless the rotor mast and blades can take the loads of shifting from XX speed one way to YY the other several times a second for thousands of hours.

But it's also a trade off; the helicopter works by blowing air down, and when you get close to the ground you get an added benefit of having a hard surface for that air to push against. With wings below the rotor disc, that area is lost in the total lift gained hovering in ground effect; you're pushing against the helicopter itself and not the ground.

by **Francisco P. de Nanclares** » Sun Feb 10, 2008 4:07 pm

And the forward going blade reaching the speed of sound and losing lift.

Cheers.
Pachi.

by **chuck** » Sun Feb 10, 2008 3:08 pm

Timmy C wrote:I'm just guessing, but would the reason for the departure from compound designs to a tilt-rotor design be due to a "speed cap" that a helicopter rotor produces? In other words, is there a "max speed" that a helicopter rotor restricts the aircraft to, and so they are making the tiltrotor design to eliminate that constraint?

Yes, there is. forward motion of normal helicopter with horizontal rotor is limited by the requirement that the forward speed of the helicopter does not cancel so much of the airspeed of the rotor blades on their backward half of the rotation that the blade lose lift during hald of each turn. This issue is bypassed with a tilt rotor that turns vertical during high forward speed.

by **chuck** » Sun Feb 10, 2008 3:01 pm

Mark Petersen wrote:I still can't believe we let a similiar capability slip through our collective fingers 40+ years ago

http://www.helis.com/50s/h_rotdyn.php

The capability that slipped through our fingers always looks good in retrospect because there was no time for any problems to manifest themselves. If Osprey had been canned in 1987, you will be crying a river of tears over the supposedly vast potential that we "let through our fingers".

by **Timmy C** » Sun Feb 10, 2008 2:29 pm

I'm just guessing, but would the reason for the departure from compound designs to a tilt-rotor design be due to a "speed cap" that a helicopter rotor produces? In other words, is there a "max speed" that a helicopter rotor restricts the aircraft to, and so they are making the tiltrotor design to eliminate that constraint?

by **Mark Petersen** » Sun Feb 10, 2008 9:22 am

I still can't believe we let a similiar capability slip through our collective fingers 40+ years ago

http://www.helis.com/50s/h_rotdyn.php

by **Sean Hert** » Fri Feb 08, 2008 2:00 am

Ok, that is pretty cool. The video of the Piasecki X-49A? Woah.

The return of the Cheyenne!

by **Tracy White** » Fri Feb 08, 2008 1:52 am

Werner wrote:I wonder if a fully modern, state of the art $110,000,000 helicopter wouldn't do better with less risk.

I'd really like to see something like the Compound Blackhawk given a "whirl."

Wait until the first Osprey is shot down.

by **bengtsson** » Mon Feb 04, 2008 3:52 pm

When the military tells you you like something, you like it! I been there and I take it all with a grain of salt. As to Iraq, it's not needed there at all. Missions were accomplished in fine style without it. What is the cost benefit ratio of having it there? It's been built and payed for, they have to use it or many officer's careers are going to go to heck. God help that machine if anyone sells the Iraqi fighters any semi-modern infantry handheld AA weapons. The enemy there is in no way to be used as a measure of our equipment's merits. It is in no way a modern battlefield. Ask the Israeli commando forces that went into Lebanon what even semi modern infantry weapons can do.
I'll admit, I don't like this aircraft. I don't think any Marine should be going up in it. Period. I doubt it can servive even modest enemy capabilities if they were up to date.

Bob B.

I

by **Werner** » Mon Feb 04, 2008 2:57 pm

Sean Hert wrote:Well, here's an article from military.com- it's not the same one IIRC, but covers some of the points

I'm sure the aircraft fills some important gaps for the ground-pounders. After all, it's been sitting in the pipeline blocking any alternatives for 30 years now... the question is, was that the right choice?

I wonder if a fully modern, state of the art $110,000,000 helicopter wouldn't do better with less risk.

by **Sean Hert** » Mon Feb 04, 2008 2:54 pm

Well, here's an article from military.com- it's not the same one IIRC, but covers some of the points

Higher, Farther, Faster: Osprey in War Military.com | By Christian Lowe | January 22, 2008 wrote: Al ASAD, Iraq - The Marine Corps moved heaven and earth to get them here. An amphibious assault ship was commandeered specifically to carry the New River, N.C.-based squadron halfway around the world to the most dangerous war zone on the planet.

And there was a lot riding on this deployment. Billions of dollars were spent over nearly three decades on a technology that many said would never work. And its track record -- at least in the early years -- wasn�t very good.

But the Corps� most high-profile program is finally deployed, and from the looks of it, the MV-22 Osprey tiltrotor transport is living up to its promise.

"There�s nothing in the inventory that can keep up with the Osprey," said Lt. Col. Paul Rock, commander of Marine Medium Tiltrotor Squadron 263, which deployed here in late September. "This aircraft can scream across the ground."

And that�s a big deal in a war zone still simmering with insurgents and terrorist-inspired upheaval. The more an aircraft can stay out of the danger zone the better.

by **Werner** » Mon Feb 04, 2008 2:46 pm

I think 1,752 flight hours over three months works out to 1.5 flight-hours a day per machine.

In my tally of service personnel, I missed another 12 Boeing support experts. That makes 28 attached specialist contractors supporting the squadron establishment's maintenance unit for 10 aircraft. It looks like 3-4 maintenance hours for every flight hour for this squadron.

by **Sean Hert** » Mon Feb 04, 2008 2:44 pm

Where'd you read this? I was just reading someplace else (I'll try to find it) about how they love the Osprey- gets wounded to and fro so much faster, it's saving lives, it can do 2+ cargo runs in the time it takes a helo to maybe do 1. Also that the dust in Iraq has been less of an issue than expected.

I'll go find that article....

by **Werner** » Mon Feb 04, 2008 2:40 pm

Apparently the machine has had quite a few electrical and electronic faults.

by **bengtsson** » Mon Feb 04, 2008 2:36 pm

Thank god my son in law is in the Army, when he goes back for his second tour soon he will not have to go up in one of those machines. I feel sorry for the Marines.

Bob B.

by **Werner** » Mon Feb 04, 2008 2:31 pm

In the first three months of VMM-263's deployment, these new planes have been available somewhat less than planned in spite of 2 shifts working 12 hours a day on their maintenance, together with 16 contractors provided by Boeing and Rolls-Royce. The average availability was been 76% in October and 65% in November. Not quite a "kick the tires and go" type of record.

The tempo of operations is demonstrated by the 1,752 flight hours, 7,144 passengers and 686,047 pounds of cargo carried in those months.

The conclusion of the article? "The jury's still out on the $110,000,000 MV-22".

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