As some know yesterday at the aerotow I crashed my Duster. After release from tow the plane flew fine striaght but almost every turn resulted in a tip stall. I clicked in some clicks of down trim several times throughout the flight but it still fell off a tip on turns. Before setting up for final I made some flatter turns right over my head maybe 200/300 feet high without stalling. There was a turbine on the runway warming up so I flew south toward the mountain. When I heard the turbine taking off I made a 180 degree turn back for the field. The plane tip stalled spiraling in nose first.
I plugged everything in this morning and ran all the surfaces and everything worked. The elevator trim was right at neutral, even though I was clicking in down trim several times durring this flight. I ran the elevator trims and the trim did work. The last time i flew was on the slope in very light conditions. I suspect i had trimed the plane up significantly durring this flight. I built the duster without washout, a possible mistake. I did examin the wings and there does not appear to be any twist, or washin, which would tend to promote tip stalling.
I suspect nothing was wrong with the plane other than the pilot was flying way to slow. Flying these large gliders at Grantsville you can get quite far away, resulting in not being able to really tell how fast you are going and how sharp your turns are. The slope is completely different flying and way more forgiving. Flying this glider 2-3 times /month on the slope and only 3-4 aerotows per year also makes it difficult, at least for me to transition from Ridge lift to thermal flying.
What I will do different.
1) I have never trimed my planes for Aerotow. In the future my first aerotow flight will be a trim flight, for determining the elevator trim that results in sufficent speed where the plane can be banked at a 45 degree angle without tip stalling.
As far as the condition of the Duster...
- Body other than the canopy is fine. Canopy is cracked in several areas. Was not happy with the job I did on the canopy anyway.
- Horizontal and vertical tail surfaces, not damaged.
- Wings are damaged pretty good. The duster had a 78" center section that slides between two bulkheads and securred with bolts, and 50" plug in tip sections. The center section broke on both sides at the dihedral joints. which are about .500" outside the edge of the body. The center section that slides between the bulkheads will have to be completely rebuilt as well as about a foot into each wing. The tips are not in that bad of condition but both at the area where the airelons start have a crack through the sheeting, I will need to disect and see if the spar is damaged in these areas.
I have other funner projects going on right now but eventually might rebuild this.
Oh man, Lee, that really sucks. Glad I wasn't there to witness the crash.
I know exactly what you are talking about, there is a tendency to fly too slowly during aerotow or thermal events. I've had the ASH tip stall on me in turns when it's way up there and hard to determine speed. I think you are right about trimming for a more nose-down attitude to keep the speed up. The other thing that might help is a millimeter or two of reflex in your ailerons. I don't know how the Duster would respond to it, but it is certainly worth a try.
Well, you now have the winter to get her back together. Don't feel too bad though, you'll still need three more rebuilds to match the number of times I've rebuilt the ASH!
Lee, sorry to hear about your crash. I bet you'll have her rebuilt quickly!
Just thought I would mention that my radio (Futaba 9CAPSuper) has 3 flight modes all with different elevator trims. Not sure what radio you're flying but maybe worth looking into:
I use 1 for themal mode (trimmed for level flight at optimal thermaling speed). 2 for speed mode (Launching, Landing, big dives, transitioning from sink to lift.) I don't really use 3 but some guys will use a third flight mode for a speed mode w/reflex.
Good luck with the winter project!
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