Shameless update from Dale Kramer

"Multirotors come down very quickly and very stable with a good controller, not like the limitations of the 1950's tail sitters (all manual control)."

Vortex ring state can occur when settling under power with helicopters as the rotor settles into its own downwash. This has caused a number of crashes including the V-22 Osprey. So there is risk in "coming down very quickly". Once this occurs in helicopters (and I've only personally hovered models and real ones in forward flight :c) adding power simply feeds into the vortex problem. The save is to apply cyclic and move off into clean air. Is that an option with a tail sitter? Is there a "save"?

Another question is that once pitched up to land, would Rotax failure have a recovery mode?

Oops, that is 900 ftlbs in static conditions. It would be much less at any significant transition speed but still, I think the transition can be done without much of a zoom up. There have been all electric and 'similar aerodynamics' transition models built before and the videos I have seen of their transitions did not show much of a pull up but of course each design is different.
Bumper, yes vortex ring state conditions are possible. I believe that that risk can be reduced by adding some forward translation when you let down and by staying away from other vlift vehicles. Once near the ground of course you need to slow all movement down.
These conditions we are talking about the need for testing, just highlight why I am building a 1/4 scale model right now, not the full scale.
Didn't the Osprey put some sort of restriction on landing in close proximity to other Ospreys as an acceptable risk reduction for this issue?
Interesting to note that this condition only became apparent, years into the multi billion (I think billion) dollar program. Glad we all can take advantage of their experience.
Rotax failure results in the need for airbags if you are in transition or hover. Since all these failure we are talking about are for hover or neaar hover conditions, they would all happen close to the ground where the likelihood of a whole vehicle 'parachute' letdown or ejection seat failure would be very high. Having survived a very high rate of descent sailplane accident, where trouble began at a very altitude, I can say that, at least in my case, I believe that cockpit air bags would have greatly reduced my injuries.
For the past few years I have toyed, as many others have, with the idea of manned 'multirotor' designs. The keys to having a design with 'acceptable risk' failure modes is spending most of the flight time in aerodynamic flight, using more than 3 or 4 rotors for hover, redundant motor controllers and hover controllers (yet to be worked out) and airbags I also considered just doing transitions over water (it is softer with a landing pad of waters edge, which is funny at first but may be a good practice for risk reduction whenever possible.

Edit 'when trouble vegan at a very LOW altitude'

Edit 'when trouble began at a very LOW altitude' and 'landing pad AT waters edge'
and a few other typos, oh well!

On Thursday, March 17, 2016 at 6:17:09 AM UTC-5, DaleKramer wrote:
Oops, that is 900 ftlbs in static conditions. It would be much less at any significant transition speed but still, I think the transition can be done without much of a zoom up. There have been all electric and 'similar aerodynamics' transition models built before and the videos I have seen of their transitions did not show much of a pull up but of course each design is different.
Bumper, yes vortex ring state conditions are possible. I believe that that risk can be reduced by adding some forward translation when you let down and by staying away from other vlift vehicles. Once near the ground of course you need to slow all movement down.
These conditions we are talking about the need for testing, just highlight why I am building a 1/4 scale model right now, not the full scale.
Didn't the Osprey put some sort of restriction on landing in close proximity to other Ospreys as an acceptable risk reduction for this issue?
Interesting to note that this condition only became apparent, years into the multi billion (I think billion) dollar program. Glad we all can take advantage of their experience.
Rotax failure results in the need for airbags if you are in transition or hover. Since all these failure we are talking about are for hover or neaar hover conditions, they would all happen close to the ground where the likelihood of a whole vehicle 'parachute' letdown or ejection seat failure would be very high. Having survived a very high rate of descent sailplane accident, where trouble began at a very altitude, I can say that, at least in my case, I believe that cockpit air bags would have greatly reduced my injuries.
For the past few years I have toyed, as many others have, with the idea of manned 'multirotor' designs. The keys to having a design with 'acceptable risk' failure modes is spending most of the flight time in aerodynamic flight, using more than 3 or 4 rotors for hover, redundant motor controllers and hover controllers (yet to be worked out) and airbags I also considered just doing transitions over water (it is softer with a landing pad of waters edge, which is funny at first but may be a good practice for risk reduction whenever possible.

Borrow a foam pit from the extreme sports folks.

Vortex ring state has nothing to do with "staying away from other vlift vehicles." VRS is the interaction with your own vortex that decreases the relative angle of attack on your own airfoils/rotor blades. The recovery is to lower collective (altitude permitting) and use cyclic to pitch forward in order to fly out of the ring state - essentially to leave the vortex behind you. Simple adding power will exacerbate the "settling with power" and accelerate your descent.

I've encountered settling with power a couple of times back when I flew helicopters. The worst was when holding a stationary position at 1000' in a Bell 47 with a skysign (grid of lights). The bottom suddenly dropped out and the entire ship started shuddering as the blades went in an out of a stalled or zero lift state. Recovery was textbook and we lost about 200' feet.

How to recover in something like this proposed VTOL will be a large hurdle to surmount for certification and for overall safety of the design.

Paul A.
(Knocking the dust off my CFI-Rotorcraft...)
Jupiter, FL

Thanks Paul, I added that statement only because I understood that the Osprey had that recommendation added to its operation requirements.

Who knows, having propellers on 3 different horizontal planes during hover and that are so spread out versus their diameter, could reduce the chances of vortex ring state significantly.

In any case, we are talking about a condition that seems common to VTOL and helicopters which tells me that there is no reason to stop the development of my design due to some foreseeable consideration.

The proposed full scale vLazair would be an LSA with minimal certification issues.

Dale

On Wednesday, March 16, 2016 at 2:04:29 PM UTC-5, wrote:
Mandatory Flarms? Maybe if folks arent so busy playing with all their cockpit electronics they can keep their eyes outside where they belong. Flarms are not the answer, decent airmanship is. And heaven forbid any more dang things become mandatory. We cant legislate away idiocy.

Why not? We mandate parachutes, at about the same cost, and for the same reason: "See and Avoid" is really the "Big Sky Theory" and even the best lookout can't always detect a threat in time to prevent a collision.

Flarm is a valuable tool to help prevent a mid-air. When it fails (perhaps because the other guy doesn't believe in Flarm), your parachute is the next tool to use to save your life.

To me, idiocy is ignoring actual threats and practical solutions.

Kirk
66

On Thursday, March 17, 2016 at 9:02:45 AM UTC-7, kirk.stant wrote:
On Wednesday, March 16, 2016 at 2:04:29 PM UTC-5, wrote:
Mandatory Flarms? Maybe if folks arent so busy playing with all their cockpit electronics they can keep their eyes outside where they belong. Flarms are not the answer, decent airmanship is. And heaven forbid any more dang things become mandatory. We cant legislate away idiocy.

Why not? We mandate parachutes, at about the same cost, and for the same reason: "See and Avoid" is really the "Big Sky Theory" and even the best lookout can't always detect a threat in time to prevent a collision.

Flarm is a valuable tool to help prevent a mid-air. When it fails (perhaps because the other guy doesn't believe in Flarm), your parachute is the next tool to use to save your life.

To me, idiocy is ignoring actual threats and practical solutions.

Kirk
66

Hi Kirk,

I'm totally with you on Flarm, but I was marveling this morning about how we were having a great technical discussion about relatively high level stuff with Dale & how brave he was to start it here. I know Dale is the one that threw out the Flarm bait and I bit too, but we've got so many other threads to beat each other up about Flarm that it would be a shame to derail this nice discussion.

Cheers,
Craig

Sounds to me like this 'Radar' feature is what may be promoting more heads down use of Flarm. I don't think I am in favor of 'Radar' use.
Thanks Kirk!

Dale