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Tilt Rotors


CJ Eliassen
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Like has been said much before, NASA got to the moon quicker than the Osprey got operational.

Despite the apparent up beat mood thats being promoted by the developers I think there are still many entrenched problems in the ship.

In a recent article in rotor and wing they stated that they were working on a ultra sonic VRS detector that would let the pilot know if one rotor was entering VRS so that AVRS could be avoided.

Even with that improvement theres still a lot of problems. The rotor wash is to high to work from unprepared strips, its already to heavy to add guns an armour, and it appears that aproach profiles will be severely restricted.

The problem seems to be that there is nothing else on the horison for heavy lift transport. I beleive at the last time they looked at cancelling it, they decided against it due to the lack of anything else.

One thing seems certain though if they loose more life getting this thing to work another replace ment will have to be found.

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I don't know if a VRS detector will help much if the pilot is trying to dodge bullets or AAA when on approach.   The heavily loaded prop-rotors help to increase the ROD at which VRS will be experienced, but it also increases the speed putting VRS right into the operational profile.  Doesn't seem like the best thing to have in a combat aircraft.  

 

With the blades and wings all folding, seems to me that they forgot the basic KISS principle.  So complex and so many things to fail.  

 

Do you think the BB-609 will make it to production if the V-22 fails?

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With 3 new choppers all coming out right now I would be surprised.

Theres the S-92, A-109, and the EH 101.

Thats a lot of competition. The thing that will kill the 609 is the costs.

The running costs will have to be massive.It would have to suck fuel like a pig in the hover, and its even more complex than a chopper. I think the DOCs will be very high.

They seem very committed to it now but from what Ive heard the companies operating the meds and heavies are more interested in the bottom line than a few extra knots. Add that to the fact that they will take up the whole heli pad on a rig, or roof top, the costs and hassles become very high.

AB is claiming 50 sold already, who knows for sure, but one thing to think about, for how much it will cost, you could probably have a lear and a 2nd hand S-76.

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I was fortunate enough to talk with a V-22 test pilot when visiting a flight school a while back.  His friend was the Chief Instructor Pilot there.  Anyway, he said there are too many political struggles for the program to survive - mostly because of the engineering problems.

 

He gave me an example of when a V-22 crashed because the control systems were accidently put in backwards!  Also, I recently came across the following articles, which puts a dark cloud of the project...

 

http://www.g2mil.com/V-22struggles.htm

 

As far as a civilian model, I can't see how it would be cost effective.

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  • 1 month later...

As often stated with enough power you can make a barn door fly.  The tilt rotor (V-22) does fly and when they get all of the reliability and safety of flight bugs worked out it will do very well.  That is until it enters a combat scenario.  When it enters into the helicopter mode and slows for landing and disembarkation of troops and equipment it is extremely vulnerable.

 

The airframe structure is mainly composite material that does not lend itself to field repair and the entire aft structure from the wing back is one piece.  If this section sustains severe damage it must be removed from the airframe and shipped back to the factory for remanufacture and/or major repair.  This will have a major effect on the squadron availability and impact the operational elements to carry the battle to the enemy.

 

One of the selling points made to congress to justify the high cost of manufacture was that the use of composites would provide more reliability than conventional metal structure, which is true.  However the level of maintainability of composite structure is much lower than that of metal structure.  Metal structure can in some cases be repaired at the first or second level.  Composite structure can’t effectively be repaired in the field without compromising structural strength.

 

In a heavy battle environment there will be a significant level of attrition of the V-22.

 

:unclesam:  :bowdown: Pierre just completed his flight training and the instructor showed him what happens during Zero G.

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Just remember that many of these same sentiments were brought to the fore, when a certain Mr. Sikorsky first started developing our beloved helicopters.   High costs to operate (what's a rental cost for an R22/Sweitzer 300 compared to a C150 ?? 3X as much !!) such low speeds (then heli's were generally cruising at 70 kts), poor lifting capabilities, overly complex, etc, etc.   The fuel burn is a non-issue, if you put the same engines in another helicopter, pull the same power out of them, then the fuel burn will be the same.  Yes DOC's will be higher, but in a cost per mile, may be quite competitive.  

 

Yes there are technological difficulties, and I hope these will be overcome, since the premise of the craft is extra-ordinary.  Where I believe the V-22 will shine is in SAR.  It's as fast (or close enough) as a C130 herc, but has the advantage of being able to land close to the rescue site, or hover, and allow someone to be winched aboard.

 

Cheers

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Randy, no disrespect intended, but what about the down wash?

They are already restricted to prepared airfields, and restricted from fast roping.

The big problem is you cant change the laws of physics. The massive disc loading, creates massive downwash.

Looking cool aside would you really want to fly one?

Before you answer, answer this senario:

Hey man fly my chopper, its quick. OK you say what about emerg procedures?

Well, you cant auto, you cant glide.

Oh, OK, anything else I need to know?

Well dont desend to quick, or youll be inverted in the ground, and its sloppy as heck in the hover.

For me personally I wouldnt fly a ship that couldnt glide or auto in a powerout situation.

I understand the desire to see new technology go forward, and while the tilt rotor is an exciting development, I think there are to many bugs.

The thing that seems to be driving it is that there is nothing elven close to being a rival with a hope of being produced.

I hope they do get it working, I just dont think that they will.

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Everytime you perfom a maximum performance takeoff, you have the same negative characteristics.  You are inside the HV curve, so you can't glide and you can't auto.  So, you run a few safety checks to make sure your ship is running okay before performing this maneuver.  I have no idea, but I imagine the V-22 has a similar safety check procedure before inverting the blades; otherwise, they would do a run-on landing to minimize damage (bang up blades instead of ship).  Having that said, I don't think the V-22 will live as either commercial or military aircraft.  I also agree that the technology just isn't there... yet.
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Gummy, none taken.  

 

Valid points, but how much higher is the downwash, than say a fully loaded UH-1 ??  Or S-92, EH101 ??  I don't know, as each of them has a pretty good downwash.  A/c are lost each year due to whiteout/brownout caused by the downwash obliterating all visual reference.  Perhaps the limitation on the Osprey is to prevent an accident which could end the program.  Allow Bell/Boeing some time to address some of the other technical difficulties.  Or there might be a problem, I don't know.  There has been so much propaganda, and misinformation, that it's hard to determine what is true, and what is merely conjecture.  

 

I had thought that there was a disconnect (freewheel/sprag/overrunning clutch type deal) in case of a dual engine failure.  Allowing the thing to perform a form of autorotation.  I would imagine she'd be a little sprightly in the descent (R-22 comes to mind :D).  Those stub wings would generate some useful lift, easing the load on the rotors.  There is also the fact that if they do want to sell the 609, it will have to perform, and be survivable with 1 engine out, and with both engines failed.  

 

Cheers

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The V-22 and the AB-609 are powered lift aircraft and therefore do not have to demonstrate autorotation.  When I worked on the V-22 program I had a conversation with an Aerodynamics engineer and he indicated that the rate of descent in autorotation for the V-22 was 4-6000 feet per minute.

 

:unclesam:  :yinyang: This is Pierres brain after the first few lessons at ground school and several flights under the hood.

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I believe the V22 has been tested in both autorotation and fixed-wing glide, and the glide seems to be quite doable (makes a mess of the rotors on landing, though). Here's an link to the:

Rotorhub article

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Hey again, below are some of my personal favourite exerts from the link posted by fling wing:

With reguard to the cross drive system

‘And we have had only one loss of the cross shaft that handles the power transfer during the entire test programme,’ says Tom MacDonald, chief test pilot on the integrated test team. (He does not include a shaft failure following an engine explosion that led to a fatal accident in 1993.)

 

In reference to autos,

'MacDonald says that for years it was assumed the best way to handle a power problem was to raise the nacelles ‘and then kind of do this fluttering thing’ to the ground similar to a helicopter autorotation.

But MacDonald says it’s clear the vehicle can’t really be landed safely like that – although test pilots have been able to simulate flaring the aircraft after the descent portion of the maneuver

But we don’t see fleet pilot being able to do it safely. The descent rate is unrealistically high for the average service pilot.

With reguard to a glide,

It’s a fastish approach, but nothing untoward. Say about 120 knots on final perhaps more depending on your weight. There’s plenty of maneuver margin and, sure, you’re going to bust the props off. But so what. They’re designed to do that.’

 

with reference to the testing so far,

A series of tests demonstrated stable approaches in a simulated glide to Pax River runways. For safety reasons the approaches were abandoned at 800 feet

 

Reading between the lines it doesnt really sound that optimistic to me.

Comparing it with the CH-53, a larger ship the figures dont seem very good to me.

The CH-53 has a descent rate of 2000-2500ft/min, comared with the 4-6000 for the v-22.

The landing speed for the Ch-53 is 30knts comapred with the 120 for the v-22.

 

Randy, yes aircraft have been lost to brown out, reguardless of make. From what I understand the restriction was imposed for the saftey of ground personel. The velocity of downwash is directly related to disc loading.

To give an Idea of the differences the robie22 has a disc loading of approximately 3lbs/ft^2, jet ranger is around 4, MD500 is about 7.

THe CH-53 has a disc loading of around 13lb/ft^2, While the V-22 has a disc loading of around 25lb/ft^2, almost double.

 

I just found the article with the limits currently imposed,

 

Significant flight limitations were placed on the FSD V-22 in OT&E to date, including:

 

not cleared to hover over unprepared landing zones until OT-IIC

no operational internal or external loads or passengers

moderate gross weights only

not cleared to hover over water.

 

I could go on but I wont. There are so many thing that I persoally see fault with, it seems a shame to me that so much money is being spent on an aircraft that wont have the capabilities of what they are trying to replace.

 

:crutches: This is Pierre, after completing his zero g training in the robbie, he went on to try auots in the V-22, the funeral is on wednsday.

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I have a feeling that the V-22 is not well suited to the role the military is trying to put it in. It has a niche, but as many have already pointed out, it's a small niche indeed - the money poured into the V-22 would most likely have been more effectively used to make more "conventional" aircraft more capable.

 

The 609 is a different story. It is also a niche machine, but the niche is much bigger in the civilian world. You have pretty much the performance of a King Air (yes, less range, but how many twin-turbo flights are more than three hours). You can land (almost) anywhere you'd land a S-76. The cost per hour has not yet been proven, but if it turns a six-hour trip into a three-hour trip, that's good. If you can fly those three hours above the weather, that's better.

 

There's a huge attraction to stepping into an aircraft in downtown New York and being able to step out of the same aircraft an hour later in downtown Boston.

 

I'm a lot more optimistic about the 609.

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  • 1 year later...

I'm surprised I have'nt seen more coaxial rotor or intermeshing machines as they try to push the envelope.   Some hatchet tip rotors fend off retreating blade stall to a higher speed on single rotor machines so add it to rotor designs for the duals.    

 

I'd go for a ride in a fullsize production "Unicopter" but hide behind a fire truck when a tilt rotor is hovering...

 

A turbine powered "unicopter" type upsized to a EC155 sized cabin would be a good ems rig.

 

Unicopter

 

If I was an engineer at kman I'd start with the engine/trans from the kmax, make a fuselage as slippery as EC's but with the pusher prop.   They will need 3 or 4 rotor elastomeric rotor heads.

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