Shameless update from Dale Kramer

Craig,

Thanks, right now I plan to have sort of a log on its Kickstarter page, at least for the 1/4 scale vLazair.

Dale

On Wednesday, March 16, 2016 at 12:22:12 PM UTC-7, DaleKramer wrote:
Craig,

Thanks, right now I plan to have sort of a log on its Kickstarter page, at least for the 1/4 scale vLazair.

Dale

Cool concept. There are a couple things I can see to worry about. It would seem like transitioning from horizontal to vertical landing would involve a risk that the pilot not make it all the way down to the parked position before his 3-4 minute battery life expires.

The other thing that looks worrisome is vulnerability to ground wind in the vertical standing position.

Dale will be pleased to know that the upcoming Nephi nationals does require PowerFlarm. Hopefully that trend will continue.

Hi Steve,
The transitions should be very quick. Thrust to weight will be about 1.3/1 so acceleration into cruise should be very quick. Landing transitions will basically be just a normal final approach to a touchdown spot but with the idea of being 50 ft high (or so) when you get there. This transition will be very easy to verify and demonstrate with the 1/4 scale. Can always add a few more pounds of battery if needed.
I am hoping to design the gear such that a single person can tip it from tail to nosegear if it gets windy for a tiedown.
What will be strange is that the 'ideal' landing direction will be a 90 degree crosswind landing wrt wind efects.
Great comments!
I saw that for Nephi, hope it continues for a while. Can't afford a glider yet.
Thanks,
Dale

On Wednesday, March 16, 2016 at 1:12:18 PM UTC-7, DaleKramer wrote:
Hi Steve,
The transitions should be very quick. Thrust to weight will be about 1.3/1 so acceleration into cruise should be very quick. Landing transitions will basically be just a normal final approach to a touchdown spot but with the idea of being 50 ft high (or so) when you get there. This transition will be very easy to verify and demonstrate with the 1/4 scale. Can always add a few more pounds of battery if needed.
I am hoping to design the gear such that a single person can tip it from tail to nosegear if it gets windy for a tiedown.
What will be strange is that the 'ideal' landing direction will be a 90 degree crosswind landing wrt wind efects.
Great comments!
I saw that for Nephi, hope it continues for a while. Can't afford a glider yet.
Thanks,
Dale

It will be interesting to see how that vertical landing works out with the model. I can't visualize how a normal approach speed can get you to a vertical position. Without thrust vector control it seems like it would require a high approach speed in order to then pull up to a vertical position and begin backing.

Have you modeled the vertical landing? How high does the aircraft get if things are done correctly? What speed does it back down at? Will the landing be autonomous or pilot controlled?

I can swallow the idea of vertical take-off much more readily than the landing. Maybe I'm just not visualizing the dynamics of the landing problem correctly.

Thinking about that some more, you don't necessarily have to approach at a higher speed and pull up. With enough thrust you can power your way through deep stall. Yet I still think it questionable that you can have enough battery life to assuredly get landed before it all comes to an end. I hope it works.

Steve,
Sorry, been busy, but yes you got it. With top electrics OFF and bottom electrics ON FULL, and wingtip electrics on 1/2 and Rotax on FULL there is still 1:1 thrust and about 900 ft-lbs of thrust pitch UP moment available (plus aerodynamic pitch up from elevators). It should pitch up to hover relatively easily. There are two throttles for manual flight, one for electric and one for Rotax. Yes there will be a auto transition mode. Electrics don't even come on until slow speed (fixed pitch props). 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).
Glad you are thinking about it

Dale

"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?