Closest Real-Life Airwolf Equivalent?

[Spino]

One problem was that the Army decided to give up high speed flight in favor of the tactic of hovering behind hills and using the terrain to conceal their helos. That's why the Apache is not the worlds fastest chopper. So both Sikorsky and Lockheed were working on something the Army eventually decided it didn't need.
Those Sikorsky proposals look like great whiff material.

Well to be fair high speed doesn't exclude that kind of hover capability, and it has the added benefit of getting you to the battlefield faster.  On the AH-56 this was especially true because the reversible pusher prop allowed for rapid acceleration and deceleration, so your could get to a hover spot faster and stop on a dime.  Could still be useful in certain situations, but obviously the Army decided it wasn't worthwhile.

The AH-56 also apparently had quite an advanced equipment fit, in addition to TOW missiles it had a computing sight for its other weapons, and I believe that was linked to a laser rangefinder and a doppler radar to get accurate range information.  And all that in the late '60s!  If I recall correctly even the Apache doesn't have range computing for its unguided weapons.  Its fire control computer could also store coordinates for multiple targets, allowing the helo to spot targets, dip behind terrain, and pop up and attack those targets quickly from a different direction later.

Both the Cheyenne and the S-67 were highly agile, particularly for their size and speed, so they could work in and out of rolling terrain easily.

[kerick]

It also depends on which congressmen had stock in which company. Rumor was that Bell got so much work because the First Lady Johnson had a large share of Bell stock. It was in her name anyway.

[Weaver]

That 'rotoprop' idea has always puzzled me.

When they swivelled the rotor round to the rear, did the pilot have to lean VERY heavily on the rudder pedals to trim the over-sized rudder to counter-act the still present main rotor torque affecting the rest of the airframe, or was there something else going on? If there was it's not at all obvious.

AFAIK no-one else ever tried the idea, or did they?

If you look at the dorsal and ventral fins on the rotoprop demonstrator, they had rudders. That means that at high speed, they could get counter-torque and directional control from the fins, freeing up the tail rotor to become a pusher prop in the same way that fixed wings take the load off the main rotor at high speed.

[Weaver]

Here's another way to get close to Airwolf, the S-69/XH-59, with contra-rotating rigid blades and auxiliary jets. Hit 274 mph in tests, and it was a bit of a lash-up not an optimised design, so they was probably quite a bit more to be had with full development effort.

https://en.wikipedia.org/wiki/Sikorsky_S-69

[kerick]

These experimental aircraft by Sikorsky always look like they just cut up the front end of a civilian biz jet and then built the back part on later.

[PR19_Kit]

If you look at the dorsal and ventral fins on the rotoprop demonstrator, they had rudders. That means that at high speed, they could get counter-torque and directional control from the fins, freeing up the tail rotor to become a pusher prop in the same way that fixed wings take the load off the main rotor at high speed.

I did, which is why I asked the question about 'boot full of rudder'. Makes you wonder why more choppers don't have rudders too.

[Weaver]

If you look at the dorsal and ventral fins on the rotoprop demonstrator, they had rudders. That means that at high speed, they could get counter-torque and directional control from the fins, freeing up the tail rotor to become a pusher prop in the same way that fixed wings take the load off the main rotor at high speed.

I did, which is why I asked the question about 'boot full of rudder'. Makes you wonder why more choppers don't have rudders too.

Well in most cases the tail rotor's available throughout the flight envelope, so why bother. I suspect the rotorprop aircraft would have had some kind of automatic system that deflected the rudders as the speed increased and the tail rotor pivoted so that the pilot didn't have to figure it out himself.

Some helos do have rudders: the Kamov co-axial rotor types are the ones that spring to mind. On twin main rotor types, yaw control is usually by differential pitch between the two rotors, but you don't really want to do that at high speed, so the rudders are probably a useful substitute.

[Spino]

Here's another way to get close to Airwolf, the S-69/XH-59, with contra-rotating rigid blades and auxiliary jets. Hit 274 mph in tests, and it was a bit of a lash-up not an optimised design, so they was probably quite a bit more to be had with full development effort.

https://en.wikipedia.org/wiki/Sikorsky_S-69

Imagine an S-67 with aux jets.  There's the real Airwolf IMO.

[kerick]

I've noticed the Apache models I've seen have a curve built in to one side of the vertical stabilizer. If you imagine a rudder that doesn't move, that's what it looks like.

[Weaver]

Imagine an S-67 with aux jets.  There's the real Airwolf IMO.

The thing is, the auxilliary jets on the S-69 were so much dead weight in the hover that they ate the entire payload capacity, and in fact, with them fitted, it couldn't hover out of ground effect and needed to use a runway to take-off.

That's the problem with most bolt-on high-speed mods for helos: even something as simple as fixed wings. Fixed wings, that unload the rotors in forward flight and thereby raise the upper speed limit on the rotors (the stall speed of the retreating blade) have been tested to death by over a dozen different programmes starting way back in the 1950s. In almost every case, the reduction in payload caused by the dead weight of the wings in the hover, plus the loss of lift efficiency due to the rotor downwash impacting the wings, made them non-viable for a practical, production aircraft. You have to have a compelling case for needing that extra 100 mph to make it worth eating the penalties, and nobody with the money to pay for it has one, so far.

Now what occurs to me in order to make booster jets viably light, is to integrate them with the rotor power plant. Imagine this: you have two turbojet cores, one either side of the helo, with elongated jet pipes. At the end of each jet pipe is a free turbine driving a fan, which gives you the thrust you need for fast forward flight. In between the turbojet and the aft-fan is a clang-box diverter, which can divert some or all of the exhaust into a second turbine, which is linked by a shaft to the rotor gearbox. By varying the position of the diverters, you can vary how much thrust goes to the rotor or the fans. In theory this MIGHT ber able to get you the functionality of Airwolf (but still not the full claimed speed) for the about 60-75% the weight of separate rotor turbines and booster jets. HOWEVER, this still involves a lot of heavy steel hot-end plumbing, and my spitball estimates might prove optimistic in practice.

[zenrat]

What is Airwolf's top speed supposed to be?

[Dizzyfugu]

What is Airwolf's top speed supposed to be?

Supersonic... 

[jcf]

I think the fan in fin was an attempt to lower the drag at higher speeds. Not sure how well it works. Seems that if it made a big difference more would use it.

The fenestron is more about accuracy of
lateral control, especially in hover. NOTAR
like control without the problematic bits of
that system in regards to complexity. The reduction in drag is a side benefit.

[jcf]

The AH-56 wasn't proceded with because it
was realized that it was the wrong machine for the changing realities of what would be
needed if the Soviets attacked Western Europe.
It was designed to be an all-singing all-dancing multi-role helicopter to an early '60s conception of what would be needed, and it was influenced by what was happening in Vietnam. Unlike the AH-64 it was not designed with anti-armour as its primary role, that was to be just one of its planned roles. It would have worked OK in that occasional role in a Vietnam like scenario, not so much against the Warsaw Pact. The clue to what it actually was is the last three letters in the program name, FSS (Fire Support System). Flying artillery with a role like that of a fixed wing attack aircraft and localized fire support, after making its bombing run. The high speed requirement wasn't for accompanying the troop helicopters, it was so it could also
be an escort for fixed wing aircraft. What it would supposedly be protecting them from is still an open question. The ability to hover at 6,000 ft. was also an odd requirement.
As it turned out the experience in Vietnam showed that a smaller machine like the Cobra was the better choice for the assault role and hard to hit. The AH-56 would have been a nice fat target in those conditions.
The Cobra was also easily adapted to use
the TOW missile for the anti-armour role,
the lack of a mast-mounted site was not an
issue because of the weapon being line of
sight, the AH-56 would have had to expose
itself just the Cobra did, but again it would
have been a bigger target and more limited
in where it could hide.
Contrary to what some folks seem to believe
the Cobra was not some sort of lash up that
was rushed into production to fill the gap.
Bell was working on concepts for dedicated attack helicopters years before AAFSS came
along, they presented the D-255 concept to
the Army in 1962, it not only presaged the
Cobra and AAFSS in shape and proportions,
one of the mockups also had the stepped
cockpits that later became the standard for
attack helicopters.
The fact is that the AH-56 was designed and
built to questionable requirements that had
already been superseded by the reality of changing tactical and strategic requirements before its first flight.