S97 Raider

[SplineDrive]

Originally Posted by whoknows idont

Why? Without having given it much thought, using a fast compound for SAR doesn't seem like the worst idea.

High speed SAR has been discussed before... at one point it was hoped that a 609 tiltrotor variant with a wider door and retractable hoist would be a good fit for the US Coast Guard. So he range and speed of a twin Raider style aircraft isn't a bad fit for the mission, though making an aircraft that can handle landing on ships in severe sea states isn't something Sikorsky has tackled yet. If that's not part of the mission requirements, then sure, it's worth consideration as an idea.

[CTR]

Originally Posted by etudiant

The Cobra was indeed in service at the time, no question. The Cheyenne was to be the clean sheet follow on, faster, more powerful and more capable.
The Apache was launched as a Cheyenne successor after that effort ran into technical problems.

Just looking at first flight and introduction into service dates can confuse one into thinking that the Cobra came after the Cheyenne. The truth however is found in the program request for proposals and contract awarding dates. The request for proposals and contract award for an interim attack helicopter which Bell won came after the paper competition that Bell lost. After losing to Lockheed Bell built the prototype AH-1 using company funds. Bell recognized that the Cheyenne was not the near term solution the Army desperately needed. Once the Cobra was in service and the Cheyenne was in flight test, there was a de facto fly off competition between them. The Cheyenne with superior performance but fragile and maintenance intensive design, or the Cobra with it's just acceptable performance but rugged durability and commonality with the Huey. While not official, Vietnam changed the Army's perspective on what they needed, which doomed the Cheyenne. When the Apache was designed 10 years later it benefited from the Cobra Lessons Learned.

Performance at the cost of low availability and high maintenance is not always a good trade.

Moving forward to the S-97 thread, I believe there is a lesson to be relearned. Is the added performance provided by the highly complex composite structure, three rotor, fly by wire S-97 worth the lower availablity and higher maintenance when compared to a modern equivalent to a Kiowa?

[SASless]

Is the added performance provided by the highly complex composite structure, three rotor, fly by wire S-97 worth the lower availablity and higher maintenance when compared to a modern equivalent to a Kiowa?

Or a ...... Commanche?

[SplineDrive]

Originally Posted by SASless

Or a ...... Commanche?

That is a very fair question, no doubt!

[tartare]

So - it would seem that the proven tiltrotor format of the Valor (notwithstanding a static rather than rotating nacelle) appears to be a lot lower risk than the S-97?
With admittedly no expertise whatsoever in this area - the Valor intuitively `looks right'
And as (ironically) Kelly said - "If it looks right..."
Fascinating project - hadn't realised the split into FVL light, medium, heavy and ultra.
Now I see what you mean by the Commanche comment SAS.

[Photonic]

If I can throw a question out here, as a non-expert in this area:

To what extent is the competition between ABC and tilt-rotor designs determined by radar profile? Tilt-rotors obviously presenting a larger target in cruise mode. Or does that not matter anymore, with current AA radar tech being able to pick up anything of that size inbound and flying low?

[CTR]

Originally Posted by Photonic

If I can throw a question out here, as a non-expert in this area:

To what extent is the competition between ABC and tilt-rotor designs determined by radar profile? Tilt-rotors obviously presenting a larger target in cruise mode. Or does that not matter anymore, with current AA radar tech being able to pick up anything of that size inbound and flying low?

On what information do you base your conjecture that the tiltrotor had a higher RCS in cruise?

[Photonic]

Originally Posted by CTR

On what information do you base your conjecture that the tiltrotor had a higher RCS in cruise?

IIRC, it was an article I read somewhere mentioning the huge forward-facing area of the rotors in cruise mode. I'll see if I can dig it up.

[tottigol]

Obviously there are the wings and the nacelles with engines/gearboxes, but aren't the rotor/propeller blades of composite material?

[Photonic]

Originally Posted by tottigol

Obviously there are the wings and the nacelles with engines/gearboxes, but aren't the rotor/propeller blades of composite material?

Primarily composite, but with other materials that are radar reflective:

"The V-22 is equipped with two counterrotating three-bladed proprotors. The blades are constructed primarily of composite material with a metallic leading edge abrasion strip and integral de-ice blanket. "
V-22 Osprey

Each blade is also wired for green LED lights at the blade tips, for ground crew safety (you may have seen photos of the "green ring" on these things at night). So they're not 100% composite, and whatever metal is in there is spinning to form a disk in cruise mode. A metal leading edge strip would probably light up pretty good.

This was the only info I could find about the radar cross section, from "V-22 crew chief Staff Sgt. Brian Freeman’s letter to Gannett’s Marine Corps Times," quoted in defenseindustrydaily.com:

"Nevertheless, the countermeasures dispensing system was found to have insufficient capacity for longer missions, and radar reflection from the V-22’s total propeller disc area of more than 2,267 square feet rivals that of two Boeing 707s in formation.146 (Given that situation, one can only wonder at the logic behind the development of top-secret "stealth paint" for the fuselage at a cost of $7,500 per gallon; the one aircraft they painted required 10 gallons for a paint job costing $75,000 -- but those huge, whirling discs were still there, bouncing back radar signals with gusto.)"
V-22 Osprey: A Flying Shame?

Maybe there have been upgrades since then, and I remember seeing something recently about Bell developing new prop/rotor blades. But I think that was mainly for cost-savings? Anyway, it's just something I find interesting when comparing tiltrotor, tiltwing, and more conventional designs for military use.

[CTR]

After all these years it is suprizing to me how many people still don't understand "stealth".

Stealth technology is not limited to detection by radar. Stealth technology includes acoustic detection, thermal signature, and visual detection.

Designing an aircraft to incorporate stealthy radar characteristics is highly dependent on its intended mission. No aircraft is completely invisible to radar. Comprises are made to provide stealth where it makes the greatest mission benefit.

For a B-2 bomber it is penetration at high altitude that is of greatest importance. While on the dogfighting F-22 needs to be concerned all directional aspects need to be considered.

So before dismissing the benefits of Low Observable paint on a V-22, think about the V-22 mission.

[riff_raff]

I believe one advantage of tilt rotors versus helos is their ability to quickly climb and cruise at altitudes beyond MANPADS. There are many things Bell can do to reduce detection of this tilt rotor. They are using composite materials for most of the airframe structures and rotor. The straight single-piece wing makes it easier to manufacture and repair, and also simplifies the interconnect rotor drive system. One major reason for using the non-tilting engine was due to the fact that there were no suitable tilting turboshaft engines available.

[Mee3]

one piece of anything is harder to repair compared to segmented design.

Modern chopper can easily beat manpads in service today in terms of practical ceiling and climb no slower than TRs. The only benefit for current gen of TRs are the range and speed. Anything else is just sell pitch.

[The Sultan]

As to a tilt rotors rotor radar cross section. The rotor blades in airplane mode operate at high angles which provides the same faceting effect as on a F117 to deflect radar from returning to its source. NAVAIR tried a Lawerence Livermore airframe mounted radar blade tracker which worked ok when the target section of the blade was perpendicular to the tracker, but useless with even a few degrees of pitch as the return was deflected. The proposed solution was to add a 360 degree radar reflector to the blade to ensure a return. Obviously this was rejected as stupid. V-22's still use optical trackers for a rare maintenance action.

Note: Radar cross section is closely guarded, has little to do with presented disk area (disk presented solidity somewhat), and something a Staff Sargent would never have a clue of.

[SansAnhedral]

Originally Posted by Mee3

Modern chopper can easily beat manpads in service today in terms of practical ceiling and climb no slower than TRs. The only benefit for current gen of TRs are the range and speed. Anything else is just sell pitch.

Climb no slower? The climb rate in airplane mode is not matched by conventional helicopters, and that's precisely what riff was referring to.

Originally Posted by Vertical Mag - Flying the V-22

Climb capability is where the Osprey excels, with rates approaching 4,000 feet a minute depending on environmental conditions.

[SansAnhedral]

At AHS today, Mark Miller from SAC mentioned the S-97 has 18 total flight hours to date in 13 flights, which is over the course of 2 years.

Also disclosed they have attained 150kt in level flight and 130kt in a 45 degree bank, which aligns with the footage released recently.

[Mee3]

Originally Posted by SansAnhedral

Climb no slower? The climb rate in airplane mode is not matched by conventional helicopters, and that's precisely what riff was referring to.

Take 609 and 175 for example. They have engines somewhat in the same class. And they both climb about the same.

[SansAnhedral]

Originally Posted by Mee3

Take 609 and 175 for example. They have engines somewhat in the same class. And they both climb about the same.

Curious where you get the idea that the 609 is limited to 1500 fpm climb rate.

[Mee3]

Originally Posted by SansAnhedral

Curious where you get the idea that the 609 is limited to 1500 fpm climb rate.

I never said it is. But if you are implying that 609 RoC is in another class, surely you have done the math and the chance is very slim.

[SansAnhedral]

Originally Posted by Mee3

I never said it is. But if you are implying that 609 RoC is in another class, surely you have done the math and the chance is very slim.

AW themselves (and Bell prior) estimated 2500-3000 fpm climb rate publicly, and with quite a bit of flight testing completed to date I have heard this is not far from accurate.

A 75-100% increase would indeed be in another class.