I don't trust tiltrotors anyhow.  They are like skydiving -- even if the
pilot does everything right, they can still kill you Just Because.

If ANY flaw appears in the transmission or power control systems, the
aircraft will most likely crash.

In helio mode, the same differential thrust problem that you have in a
310 now becomes a differential LIFT issue, with a very long moment arm.

In airplane mode, the rotors are too large to allow it to land like a
plane, and even if you shut down the engines and dead-stick, you will
catch the blades long before your landing gear is anywhere near the
ground, and it will flip you over on your back before you have the time
to swear.

Autorotation is relatively ineffective, because there just isn't enough
rotor area.

Just because a technology is attainable doesn't mean that it's practical.

Keith W

The props may or may not flip you over. Depends on how they stop. Also carbon props tend
to shatter rather than bend. For our small PAV single tilt rotor we advocate large airbags for
the pilot and pax instead of chutes as they inflate faster.

http://www.rotaryeng.net/VTOL.html

For high altitude tilt rotor PAV problems a ballistic chute will work fine.

I think the new variable twist blades
Boeing is working on will enhance auto rotation. It will certainly mitigate the vortex ring
state. Variable twist blades will make the disc area more effective in helicopter mode.

Tilt rotors are the future as they solve a lot of current car traffic and airport access problems.

Paul Lamar
------------------------------------------------------------------------

Got an airbag big enough to englobe the whole aircraft?

A carbon-fiber blade which is strong enough to be 1/2 of the support of
a fully loaded aircraft is NOT going to politely break up into
bite-sized pieces in a dead-stick landing -- they are going to be a big,
nasty lever, especially if fully feathered (thus hitting the ground in
the direction of their greatest cross-section).  It doesn't matter what
position they stop in, even with one blade straight up, there are
several feet of blade below the landing gear. So check the video of that
Navyator who snagged a cable with the hook while 3 feet off the deck.
The plane hit the deck so hard that the fuel tanks ruptured and the
plane exploded into flame like a Ford Pinto that's been rear-ended by a
dump truck.  From 3 feet up.  Landing with the right side up.  Now
imagine that's your tiltrotor, digging the blade on each side into the
ground from 5 feet up.  Or worse, digging ONE blade in from 5 feet,
while the other side is still clear of the ground.

I just don't see any other likelihood -- those rotors are just too big.
It would be much more chance of survival if they used 4 instead of 2.
The Vought / Hiller XC142 Tiltwing was capable of operating like a
plane, because the blades were shorter than the clearance to ground.

"The _______ of the Future" is usually an evolutionary dead end, or the
Zeppelin would still be queen of the skies, we'd all fly personal
rotorcraft to work, and UPS would be delivering packages to Luna City.

For that matter, weren't the Vega and Pinto touted as the "Future of
American cars" . . ?  That predicted future faded pretty fast after
people started dying in them.  Just imagine how eager people will be to
climb aboard the tiltrotor and commute to work when they've just watched
the news video of another just like it falling out of the sky, ballistic
chute wrapped around as it tumbles . . .

Nope, sorry, just don't see it, and if it is the future, I'll stick to
the good ol' days.

Keith W

There is a big difference between a tail hook and a thin blade in bending
it is not designed for. Not a good analogy. Blades are primarily designed for axial
loads and not bending loads. In fact they are usually hinged much like helicopter blades.
If a helicopter blades is not rotating it will collapse upward and not support the
weight of the helicopter. What keeps a helicopter up is the centrifugal force
on the blade while it is rotating. Helicopter blades are not rotating wings
despite the appearance.

It is also possible to blow the blades with explosive bolts if the crash mode
you describe is typical.

The Vega and Pinto are also irrelevant analogies as they both had minor flaws
easily corrected.

My philosophy is solve the problems rather than give up on high potential
technology. I am glad Mazda had the same philosophy when it came to the rotary.