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The AH-64 Apache is widely considered a successful
weapons system. It's pretty tough, very flexible, has a
wide range of weapons that can hang off it and it looks all
cool and black and scary.
It has downsides, but as far as I can see, these are all
because of the inherent problems with helicopters.
Range,
load capacity, speed, max altitude, annoying noise, turn
performance. These are all issues when you have to
actively generate lift. Everything feeds into this, if you
want to move forward, you have to steal some of your lift
The faster you go, the more asymmetric your lift
becomes... all these things feed into
payload/endurance/speed compromises.
Aeroplanes suffer less, so lets make an Apache-plane
conversion kit. First, take off the rotors, this is done
routinely for transport. Next, lets fit a lovely big hi-wing
with all the lovely slats and flaps. Something like a Twin
Otter wing, maybe a smaller version of the C130, whatever
you can get off the shelf. Now mount it to where the rotors
were, should be a bolt on job. Then, have a couple of
engines hanging off it. Turboprops seem natural
candidates. The bottom of the engine pods should
structurally mount to hard points on the end of the little
stub wings on the Apache.
The wing should have space for a: lots of fuel b: storage of
the rotor blades. Under the wing should be many many
hard points for fuel/weapons. Interfacing with the existing
controls, some form of tail plane system, and whether to
run one of the Apache's engines as an apu will be worked
out by people who are good at that.
There, we now have either a: a horrible compromise, b: a
long range ferry/ long range deployment option for those
without big transport facilities or c: a sort of hybrid
medium attack aircraft.
Mock Up
https://www.dropbox.../Apache%20Plane.png
[bs0u0155, Aug 14 2014]
[link]
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[edit: is an attack airplane that looks like, but isn't, an attack helicopter] |
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Any chance of using the existing turbines for primary or at least additional forward thrust? |
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Great aircraft. Doesn't get you an attack
helicopter when you get to the forward operating
base. |
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Also, a turboprop aircraft gets you out of AAA
range. An Apache is nearly always vulnerable to
these because of a low service ceiling with any
weight on board. So you could fly around in your
Apache Plane, dropping munitions on the AAA
positions, then take off the wings, and go in nice
and low to clear up the rest. |
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So, you're hanging wings and hardpoints and feeding control lines at the top in a 'bolt-on job?' |
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True story: The local AFROTC's used to pay yearly visit to my college, bringing with them an AH-64, a Huey, and a Blackhawk that we could climb around. While peaking at the AH-64 I happened to notice that the carbon-fibre blade on the rotor appeared cracked. Poor flyboy had to stay there that weekend babysitting it while they brought a new blade to install. |
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//So, you're hanging wings and hardpoints and
feeding control lines at the top in a 'bolt-on job?'// |
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No, controls would all be wireless. If we can
control a
whole Global Hawk via satellite, we can move a
few
flaps/spoilers via short range digital radio or
optical
system. It could be as short as a couple of feet,
perhaps have an optical transceiver set up on the
inner face of each engine pod, dual redundancy,
fast,
hard to jam. |
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What about a rudder, horizontal stabilizer, vertical
stabilizer? You say the control surfaces will be wireless but
how will they be powered? |
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I hate to say it but, if you want a plane for close air
support that has the range and speed of a plane, with the
ability to hover and land vertically, the F35 would be less
terrible than an Apache with bolt on wings. |
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Well, all the control surfaces will be powered in the
usual way: generators on the engines, electrical
control and usual hydraulic rams etc. Effectively this
will be a cheap high wing turboprop with no
mid/forward fuselage, remotely controlled from
inside the Apache to which it's bolted. I don't expect
the Apache-plane to do any taking off or landing
vertically. Although Twin otters can get off the
ground in 500ft/ 64KIAS, I'd expect a little military
money might get that down a bit. |
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If fly-by-wire sounded scary, fly-by-wireless sounds even scarier. |
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All that weight hanging on the wings is the problem. |
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"The recent spate of accidents involving the new "airwire" system were finally traced to the crew's microwave oven..." |
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All that weight hanging on the wings is the
problem? |
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Really? A whole Apache is 1000+ kg lighter than a
single Trent 900 engine they hang off commercial
jet liner wings. They do OK. |
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Every hi-wing plane is essentially hanging from
underneath it's wings. Heck, the Apache hangs
from underneath its wings WHILE they're spinning
'round. In addition, I'm attaching the wing
structure to the hard points on the end of the
stub-wings on the Apache (also, plumbed for fuel)
creating tough little box sections in a little semi-
biplane arrangement. |
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//If fly-by-wire sounded scary, fly-by-wireless sounds
even scarier// |
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Fly-by-wire airliners are demonstrably safer in terms
of control authority than the conventional systems
they replace. |
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I like a laser-optical method of relaying info, its hard
to jam, and between send and receive points,
there's nothing to shoot. |
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But the mounting points for those blades are relatively narrow tubes designed to rotate about the long axis of each blade. Fixed wings, especially those with control surfaces, are rather different in terms of the loads they apply to the aircraft. |
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I'm not saying that the wings couldn't handle the weight. I'm saying that in applying all of that weight to the wings, you've increased the plane's inertias substantially in roll and yaw. It'll be a dog since it isn't designed to be a plane anywhere else and effectively carries more useless weight around. I suspect that so much of the thing would need modified that you'd be ahead simply starting from scratch. |
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" I like a laser-optical method of relaying info, its hard to jam, and between send and receive points, there's nothing to shoot. " |
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That could make flying in inclement weather very interesting. |
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"Raindrops keep falling on my plane..." |
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well water vapor doesn't absorb between 800-900 nm
or 1100 up. So use those, although, if you were
clever you'd put the light path inside the structure. |
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//Fixed wings, especially those with control surfaces,
are rather different in terms of the loads they apply
to the aircraft// |
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Think of this as more of a plane using a 5 ton Apache
as a cockpit, rather than a chopper with a pair of
wings bolted on. The wing can a continuous with the
whole rotor head mounting to the main spar. |
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Leave the bearing in. It can be locked up by the
hydraulics on the Apache. Also it doesn't have to
take much roll/pitch/yaw loads if the tail and stub
wings are all connected up. |
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If you hang the engines off of them, that's load inertia that the rotor
doesn't typically see. |
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The wing, engines and pseudo fuselage/tailplane
construction are all connected together in a standard
aeronautical configuration. The Rotor head, tail rotor
section AND stub-wing hard points are all connected
up. I think the Rotor head will see much lower
forces. |
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I think you're ignoring forces. Wing torsionals, dynamic inertial
reactions, offset weights of engines hanging forward of the wing spar,
etc. Your Apache airframe hardpoints are all in the wrong locations. |
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Made a crude mock up. <link> Apart from the very tip
of the Apache vertical stabilizer, it fits entirely
inside this cheap old Dash-8. Also realised you could
leave the landing gear extended and use that as two
more hard points. |
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Cool. Now you can put the wing on a pivot and call it either the Apachsprey or the Osprhe. |
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I'll agree with some of what I've seen above. No need to add engines. The bird already has plenty of power on tap. Just engineer some gearing into the center and nacelle portions of the wings to get that power out to where it's needed. Yes, I'd design the wing to be its own structure, able to lift the aircraft at the mounting point. It's been done before, and it's plenty do-able now. If you can set it up within a day or so, the helicopter can be its own transport into and out of "hot" areas, carrying its rotors in a protected sheath on its belly while enjoying something of the range/speed of a fixed wing turboprop aircraft, and swapping back into helicopter configuration for the duration of its deployment.
By the way, don't forget the tail. You'll want to disconnect the tail rotor and attach the antitorque controls to a real rudder, as well as rigging up an elevator (horizontal stab does move 30deg, just make sure it's set up for forward flight). I suppose it might be easier to do these as stated before, with a local ultra-secure wireless network connected to the controls. |
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