How about a tilt rotor attack helicopter?

Originally posted by Lonestar24
Does anyone know how well the V-22 might handle autorotation?

According to Carlton Meyer over on G2mil, not very well. Exceedingly high blade loadings and high rotational speeds with poor inertial loadings on the small, inefficient, proprotors tend to chew up rotor reserves faster than you can put the aircraft down. Add to this the peculiarities of assymetric RBS on a bird trying for a fast touchdown and it becomes equally easy to flip it on it's back and play lawndart.

The BAT, being a much smaller design, may be different and closer to the XV-15 (which was actually quite agile with the nacelles up) and as I recall, later versions had the engines inboard to further simplify design of the crossshaft and remove some of the complexities of wiring, hydraulics and bobweighting on the wings.

Obviously the BAT also brings you the ability to sustain altitudes above the trashfire and early (SA-7) class MANPADS envelope while (if need be) executing dive and climb attacks without total loss of airspeed for climb rate and angle. It /probably/ has similar range advantages in fixed wing mode (half the gas, but also no wingfold or troop compartment bloat) to the V-22 and the VTOL capability makes it more likely to be compatible with Marine expeditionary requirements than either the Harrier or the A-10 as a function of shared spots, lower costs and larger air components (Replacing at least 4 skids and 6 bumblebees = 10 aircraft with uniform escort performance) during RW ops.

If tiltrotors have notional problems it is the they have very narrow CG margins and limited internal fuselage volumes to stuff everything including a _downlook_ sensor suite, SLAR and long stroke gear sufficient to clear the proprotors to at least a 60` deadstick (something the V-22 also cannot readily do).

You have to be an idiot to put a weapon platform directly over any target and things like the AMUST effort have essentially proven the viability of replacing attack/recce helicopter pairings with UAVs in the division/manuever class and above. This would offload SOME of the BATs payload problems, high or low, given only that it has automated TFR capabilities like those tested on the Comanche.

Rotors down, you would consider the BAT more of a mini-Tornado than an Apache. Proprotors to 60` and you SHOULD be able to clear some wingstores, especially dropfire ones.

If the TR has any significant disadvantages it is simply that:

A. It's day has come and gone as an attack helicopter platform because we have the ability to integrate systems like the SDLF into an airframe half the size of the F-35 and use an engine like the TF34 to get twice the aero performance (especially ceiling) at half the '747, side by side' signature penalty. This is particularly crucial when you understand that escorting airmobile ops requires a 1.5X speed advantage to be able to engage enroute threats and still catch up to the slicks before the LZ.

B. Endurance + Standoff counts more than anything. A threat which cannot approach a route or fixed point objective you intend to drive into or pass by is one which is deflected more readily than one which is engaged as they come with the ground forces essentially reduced to staked bait goats. Add to this the sized of the proposed V-22/CH-53K deckspoting and under roof requirements as well as the sheer stupidity of assumption that is an MEF /ever/ operating in a high risk forced entry condition (which 'harbor assault' mission is still the Marine's principle reason for being) without landbased or CVN air support, and it quickly becomes clear that, for the CAS mission, there are better, more numerous and more _responsively available_ assets to load a real carrier with.

C. We need a small drop-fire weapon which is available as a boosted Viper Strike (VSM) and once so equipped with this and perhaps a sniper finder system like Viper you don't have to drop the nose below the horizon to engage at all. Which means that a much smaller (Scaled Eagle Eye) system may well prove sufficient without a man onboard. Without VSM, you are stuck with APKWS, JCM and perhaps SDB, as your principle micro-CAS weaponization elements and they are frankly both too large and too expensive (as is) to be carriageable by something as small as the BAT shown. Given that I believe the traditional 'gunship' mission of nose-forward strafing off a short orbit slant (as you saw in Baghdad recently) is a fools errand, putting a man onboard just to declare presence in a relatively huge airframe is ridiculous.


KPl.


LINK-

Ambush At Najaf
www.afa.org...

CEH, those like me who think that RW Attack Aviation is an abortion of resource over expenditure and stupid self-imposed service turf 'rules as missions' specialization (See Key West Accords) have seen this coming for a long time. Probably since 1968.

The problem now is that, as fast as we move up, we may end up going diving right back down into the mud when and if hunting weapons and DEWS become commonplace.

Which means that, short of agrav and deflector shields you may well have to go unmanned just to get the lolo throwaway capabilitie$ and small $ignature in the same sock.

All of which tends to literally 'emphasize' platform weight-as-cost trades to the point where man in the loop is a waste of time and your eyes in the sky may be better off thrown out the back of a truck (super Cypher like) which _drives_ to the sound of gunfire as a direct denial of troop transport asset risk. i.e. Given the V-22 is nominally useless as troop transport (too few, too short, too slow) it may, with RRB, still prove an acceptable SWORDS or Gator tosser as to be more competitive in the war-after-next (2020) scenario than direct attack aviation.

Originally posted by waynos
Yes longbow, with the size of the V-22 you would be right, but the OP wasn't talking about the V-22 itself, just a tilt rotor atack craft and I was still thinking in terms of the drawing I posted.

I think a wing is very unlikely to 'break' and if it were then the impact would have been enough to kill any type of aircraft, not just a tilt rotor

Yes, but even smaller tilt rotor will always be bigger target than comparable helicopter. Also the wing doesn't need to break, all you need to do is to hit that hydraulic shaft that connects both rotors (and you need it on tilt rotor in case opf engine failure). It goes through the entire wing so I don't think it can be properly armored.

Anyway you'll maybe see something similar to your pic in future, because Marines would like to have some faster escort for Ospreys, Cobras are too slow. There was some talk about 1 engine tiltrotor, how can it look?

With one engine? I wonder?

Unless you have one engine in the fuselage driving tilting rotors on the wingtips through shafts, as with earlier experimental offerings. Other than that I don't know.

Originally posted by waynos
With one engine? I wonder?

Unless you have one engine in the fuselage driving tilting rotors on the wingtips through shafts, as with earlier experimental offerings. Other than that I don't know.

Its an interesting idea but I do agree that it may not be the most failure safe plane. less recoverable then flying a bag of brick even. Maybe a civilian single engine would work? In a combat zone I agree that its a risk I don't like and the fact about the V-22's protection for the contecting shaft is something that escapes me at this point. It would and for the weight factor for sure.

Originally posted by ch1466

Originally posted by Lonestar24
Does anyone know how well the V-22 might handle autorotation?

The BAT, being a much smaller design, may be different and closer to the XV-15 (which was actually quite agile with the nacelles up) and as I recall, later versions had the engines inboard to further simplify design of the crossshaft and remove some of the complexities of wiring, hydraulics and bobweighting on the wings.

I think that the Bell Helicopter BAT, always had the engine in the nacelle, see link:

www.aiaa.org...

By the way, if all you said on the V-22 is true, how long do you give them, before exposing the drawback, since they are about to go into production?

What do you mean "about to"? The Marines already have their third squadron of them.

Originally posted by PopeyeFAFL
By the way, if all you said on the V-22 is true, how long do you give them, before exposing the drawback, since they are about to go into production?

As Zaphod said they are in full production and the "drawback" may not even be true so its just a thought at this point till someone can prove it either way.

If your interested in more uptodate info about the V-22 check out the link:
www.navair.navy.mil...

There was some talk about 1 engine tiltrotor, how can it look?

Just a couple of days after I was speculating about a tilt rotor with a single engine mounted within the fuselage in response to this question, I have discovered this image of a proposed Australian UAV



some info;

AVT's remotely piloted demonstrator has a glassfibre airframe just over 2m (6.5ft) long, weighs 9kg (19.8lb) without batteries and has a payload that will total 4kg for a production-standard aircraft.
The Hammerhead's propulsion system comprises two twin brushless electric motors, each driving 0.5m rotors and mounted on a boom arm that rotates through 90e_SDgr to allow the UAV to transition from vertical to horizontal flight.
A third electric motor mounted within the fuselage drives a ducted fan whose efflux is directed through four vectored nozzles at the rear to provide attitude and yaw control.
Air vehicle pitch and roll control is achieved by modifying the speed of the main rotor engines, while a rudder in the tail and ailerons in the rear wing provide flight control during horizontal flight.
Take-off can be achieved using just 20% of available engine power, with each main engine capable of producing 2.4hp (1.8kW). The UAV currently uses lithium polymer batteries, providing 20min endurance in hover mode and a forecast forward flight endurance of up to 2h.

[edit on 2-4-2007 by waynos]