Actually, last time I looked at Guiness, the Mi-24 was the fastest _service_ (unmodified) helicopter in use with a top speed around 200 knots. Of
course you don't dare maneuver it there because the margins on boom slap are so tight you don't dare.
More importantly, I recall a more or less vanilla S-76 did a 500km course at an average 187 knots in cruise which is the same as saying an F-22 can
sustain Mach 1.5 longer than a MiG-24 can sprint out to 2.65 or so.
Indeed, many civillian helos beat their military counterparts by virtue of much more capable rotor systems and MUCH MUCH cleaner (and lighter) system
design. In the early 1980's the USAr used both MD-500 and H-76 (militarized Spirit) to flat out embarass both the Apache and Snake during 'air to
air training' exercises.
That said, the X-2 looks like nothing more or less than the XH-59 ABC with a fantail as opposed to a pair of turbojets and so, IMO, if you don't
disqualify the X-2 as a compound, the 289 knot capability of it's grandpappy still makes Sikorsky the owner of the fastest chopper in the world.
Followed by Lunchmeat with their 260 knot XH-51 Little Chief.
Followed by Lunchmeat again with the 220 knot AH-56 (again, as a production ready _service_ helo).
The big problem with RBS or Retreating Blade Stall is that, even if you don't try to use collective pitch changes to retain lift on the retreating
side, the loss of lift causes the aft moving blade to droop and any subsequent loading change makes it start to buzz which eventually makes the blade
itself give up, separates the blade from the hub or cuts the boom. Rigid Rotor systems change this by virtue of effectively tying the _disk_ plane to
the advancing blade position with a stiff hubmount for all blades.
This means that the retreating rotor can neither droop on it's own nor rub at the mast and keeps everybody toes the same blade line regardless of
inertial/lift forces.
It is also why the Hokum is a joke rather than some kind of super-chopper because it's rotor system is not rigid and so if you try and load the
aircraft in a particularly turn direction at speed, you will either mesh the disks or again start separating blades.
THE BIG QUESTION then becomes "Does it matter?". Because if you have a competent ASE suite you can fly at 1G and 3-5,000ft, almost entirely outside
the trashfire envelope while defeating MANPADS and AHM with relative (MAWS time to see it coming) ease. Even as you can SEE to ranges heretofore
undreamt of by beanie prop jocks (40-60km, easy). With these kinds of capabilities, the armed military helicopter becomes less a direct combat (a
yankin' and a bankin') fires delivery platform than one which is designed to function as an econobus for sensor systems and standoff muntions. Most
of which can be dropfired.
This in turn potentially reopens up the idea of a 'cabin cruiser' system which can trade what is actually rather pathetic agility anyway (+3/-1.5G
for the Apache) for very long sensor coverage and very fast (for a choppper) refresh of wide scouting=organic ISR sanitization areas. If all your
sensors are side/downlooking, there is no reason to close with a target and so the frontal target area minimization and all round view justification
of a conventional gunship is also gone.
If you are carrying no weapons wings or fixed gear or cannon or optical systems (because a big cabin means internal stowage on a wider gear track with
shorter = more upright wheelbase), the other justification for the tandem seated gunship configuration: reduced frontal drag (Snake vs. Hog) is also
removed.
And so 'suddenly', with no requirement for agility or for external weapons loads or for visibility OVER a target the rotor system complexity of a
coax is also removed and you can go with a simple, single, hingeless/rigid main rotor system that offloads to wings or a lifting body shape in
principle cruise flight while maintaining an internal volume sufficient to be a useful liason/utility platform on the civil market.
This in turn being the principle problem I have with the X-2-
www.defenseindustrydaily.com...
As proposed. Particularly since, if I am operating a standoff sensor collection suite (including monitoring of previously emplaced UGS on a
detex-flyby basis) while acting as a drone controller for MOUT overhead apertures, I can sit the cabin like any ASW operator and 'feel no pain' of
up-front exposure.
Which means the frontend can be shorter and single-pilot optimized (SHADOW) to further assist in configuration, weight and streamlining issues.
We are now at the point where row-boat/shoot-ducks division of labor no longer makes for a viable workload reduction effort in a direct attack
platform of as limited a performance margin as the conventional Helo. Anaconda showed this when we had 4 AH-64 shot up within the first 30 minutes
and supporting air basically ceased to exist. Falujah repeated the lesson when we had something like 24 more Indians torn to pieces and one downed by
a bloody farmer and his stinkin' Carcano boltaction. We should not NEED a third.
The question then becomes whether we are willing to kick the Army in the nuts to show them that SPO _works_ (fully automated terrain avoidance and
approach to hover plus 360` night/synthetic vision systems) in a way that lets us retain a useful civil market advantage (low drag and high
performance in a 6-8 passenger cabin with 250nm range or 500nm with 4 passengers and aux tanks) once they finally get a Kiowa/Comanche/Longranger
RAH-rah replacement for their precious armed scout role.
KPl.
