Glider electric launch conversion

[Mark Hewett]

3 hours ago, PatMc said:

You can also leave the motor running at it's lowest practical speed during the approach. This causes the prop to be windmilling & adding drag rather than thrust, the result being a steeper descent. 

If using "spoilerons" as mentioned by Frank, I usually combine this with 50% (aprox) rudder to aileron mix as the ailerons will be less effective than normal.   

Also I find for the throttle - elevator mix that it's a good idea to have a few seconds delay (If your Tx has the facility) in the elevator's return to normal when the power is cut. This allows the model to slow down as it settle to it's glide angle & speed. It helps prevent loss of altitude due to inadverant stall at this change over point.The actual time delay has to be reached by trial & error over a few flights.

You know, it has never occurred to me that running the motor at lowest speed would increase drag.

 

This despite having flown full size turboprops that with the power levers closed, and the prop levers at max, the variable pitch props will be very fine and 'discing' - causing enormous amounts of drag. You can fly extremely steep approaches, but it's not recommended with passengers on as it makes them nervous. We did accept a runway change once which necessitated a very steep approach, but the hostie said some of the passengers were very upset and thought we were crashing. That was an Italian internal flight though - the British are obviously made of sterner stuff :-)    We made very steep 'tactical' approaches into Basrah because the buggers on the ground would be shooting at us. My first time there I completely cocked it up and crossed the threshold at about 1000ft. I continued and landed anyway, the runway is long, but I used most of it. I took some stick for it, but the passengers were military, so they should be used to being scared :-)      On a piston single engine light aeroplane, after engine failure the prop will windmill slowly. If you need to stretch a glide, maybe to reach land if you are over water, you can stop the prop by slowing to stall speed for a few seconds before returning to best glide speed. The reduced drag with the prop stopped instead of windmilling makes a significant difference.

 

Anyway, I will try using minimum motor speed tomorrow (oops - later today) and report back. Thanks Pat.

[Frank Skilbeck]

Re aileron reflex, only a few degrees should help, having them raised will also reduce any adverse yaw. And program the radio to reduce differential when you raise the ailerons. I also typically put my landing aids on the "throttle" stick on my electric gliders so I can modulate them on landing, the either use flight modes to switch between throttle stick control of have the motor on a switch/slider.

[Jonathan M]

14 hours ago, Mark Hewett said:

I cut the access hole and found both holes in the bellcrank were oversize for the clevis pin, and wire rod Z bend. The clevis I was able to move to a different bellcrank hole. For the Z bend slop I used a drop of medium cyano, this certainly works but I'm not sure how long it will last, so I've left the access hole hatch just tacked in place with hot glue.

 

Well done for identifying the mechanical side of the elevator issue.  Don't worry too much about the cyano, once set it is usually rock-solid and likely to last.

[Mark Hewett]

I flew it again today, wind about 10-15 mph. It handles much better with the slop taken out of the elevator linkage and the turbulator tape seems to have mellowed the tip stalling. I found that under full power you can get in a nose high low speed situation, that full down elevator cannot correct. When the stall does then occur it is a spectacular departure from controlled flight. You can avoid the situation by lowering the nose with elevator while you still have flying speed, and/or reducing power and re-applying when the nose attitude has been lowered. I suppose this is because the T tail doesn't have prop wash over it increasing elevator effectiveness, and/or may be blanked in turbulent air of off the stalling wing. I hope spin recovery will be possible - I haven't tried yet.

 

Running the motor at minimum power does seem to add a little drag and so make the landing approach more manageable - thanks Pat for that useful tip!