Amazon's Drone Helicopter Delivery Plan

Both machines have inter-linked drive trains so a single engine can drive both rotors. Unfortunately, losing a rotor (on either machine) is going to result in a catastrophic accident.

With the Osprey and its power and speed capabilities it is very possible to fly the aircraft through the power curve and into the ground even with no rotor malfunction. They crashed a couple of them this way while trying to simulate fast approaches into a "hot" landng zone like they used to do with CH-46's.

BTW, there are no clutches in the drive train of the Chinook, not sure of the Osprey but haven't heard of any. If an engine fails the power section just freewheels while the other engine takes on the load. Minor point but important.

Hooker

not being a helicopter guy, I'm not sure i understood you point about flying through the power curve, can you clarify?

Yep, no problem.

It is possible, during a high speed approach to an LZ (often done in combat). to not have enough power available in a rotorcraft to slow the aircraft before contact with the ground. This means that the momentum of the aircraft is higher than the amount of power available to arrest the approach. Thus, flying through the power curve.

Or, alternatively, the engines and power train cannot generate and transfer the power fast enough to stop the aircraft even if they have the actual power capability simply because the aircraft is flying too fast.

While there is danger in this for any rotorcraft, the Osprey has a much higher availability of momentum than classic helicopters because of its higher operational speed. Helicopter pilots transitioning to the Osprey have to relearn their trade from scratch for the Osprey and several paid with their lives.

Hooker

Is this also at least in part due to the reduced combined swept area of the Osprey's rotors, as compared to a typical helicoper?

If I understood Hooker's explanation properly, then yes, in part because the rotors are smaller, but mainly because it was designed as an airplane that can hover instead of a classical helicopter. It's advantage in combat is that it can fly as fast as most fixed wing aircraft, but that advantage is it's weakness when doing a combat approach because pilots transitioning to it from classical helicopters flare too late and are unable to slow down in time because it is moving much faster than a helicopter would be.

By golly, I do believe you've got it.

Yes, in part, so good point. Rotor momentum does play a significant role. The rest of the "equation" involves gross weight and density altitude of the area in question.

There's a ton of charts available for reference that indicate optimal speeds and power settings for a gazillion approach scenarios. Unfortunately the charts won't replace seat of the pants experience in combat.

Hooker

Do the smaller rotors make it more likely to create the recirculating vortex problems when hovering as well, or is the effect likely minimal?

Good question. I've never thought to look into that one.

I would presume that the greater separation between rotors with non-overlapping blade tracks would make the vortex less of an issue when hovering in ground effect..

But I've been known to be wrong before!

I stand corrected. Ring vortex is just as valid an issue for tilt rotors.

See first paragraph of this link.

Ah! gotcha! Makes perfect sense.

I understood they had Sprag type overrunning clutches fed by hydraulic torque converters, but I may have been misinformed.

I had an Osprey flyover yesterday, somewhere between 500 and <1000 feet headed towards Ft. Carson, I never realized just how large those 'fans' are, you could clearly see the outline. Having piloted a light twin through engine failure routines for my MEL rating, I can't imagine trying to fly that beast on 1 engine, or auto rotating to any kind of a survivable landing.

Both "fans" are interconnected with drive shafts, unlike multi-engine starch wings. One engine out is not a big deal as long as it's not heavily loaded.

Autorotation on a dual engine failure must be a trip. I wonder where they might get the hydraulic power to rotate the wing into autorotation (vertical) orientation if they have dual engine failure while in fixed wing mode.

Hooker

Maybe the pivot is sufficiently below the center of pressure for the wing/rotor combo....or the pitching moment is sufficient?

Good questions. I don't have a clue.

I did just realize though, that the wing doesn't change pitch, just the engines/nacelles.

In any case the hydraulics would still have to be managed to prevent an out of control change in engine/nacelle pitch. That would be quite a trip under dual engine out conditions.

I did a little googling but didn't find much about nacelle pitch control other that it has both manual and automatic modes.

By the way, I am presuming it is hydraulics that controls nacelle pitch but I'm not 100% sure.

Hooker

In my replies, I was clearly trying to call attention to the possibility that someone would find a need to create a drone with the capacity to carry at least two people...

The aforementioned MSN video clearly shows that possibility has already been accomplished (i.e.: happened)...

But, what actually ''happens'' is not necessarily ''what'' was expected, and/or ''when'' or ''how'' it was expected...

I did not expect an essentially validating video to be available so soon. I am still pleasantly surprised (by the video, that is)...

Also, strictly speaking, all the ''possibilities'' can not each all ''happen''...

Once one of the possibilities does happen, then another set of possibilities become possible, but only one of them will immediately actually happen, with the cycle repeating over and over and over...

Thus, only one ''possibility'' actually does ''happen'' to become actual history...

As per the aforementioned MSN video, what I thought was a short-term ''probability'' actually did, in effect, happen relatively quickly...

Wow, you really can't leave this one alone.

Seeing that you have replied to my comment three separate times, suggests that you are highly interested in my reply. Who am I to deny someone's dream that costs so little to fulfill?

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While I never communicated that all possibilities each all happen, I am willing to play devil's advocate here out of a rare impetus towards philoblogthrop duty.

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I'm not even going to bother with the low lying fruit; the hitherto unmet need for you to specify you are speaking about seemingly mutually exclusive outcomes of a single event potential.

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Instead I am going to question where your certainty comes from when you suggest that '...only one ''possibility'' actually does ''happen''...'?

How can you be certain that this is not an artifact of your/our particular perspective on time and continuity? How can you be certain that there is not a branching at every choice/possibility and you experience each of the various occurrences, but that each of you have no way of communicating with the multitude of other yous and no way to remember the various occurrences that weren't in the particular branch you are currently experiencing?

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How do you know that is all hasn't already happened?

via http://www.theospark.net/