Trimming question on OV-10 Bronco
05-06-2005, 06:33 PM
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Trimming question on OV-10 Bronco
Just test flew Rich Uravitch 52" OV-10 Bronco and the flight went well except that in order for the plane to fly level under full power, I had to down trim the elevator slightly less than 1/4" from center. The CG is right on according to the plans. Once trimmed with this down elevator the plane flys great. I did notice on landing that the plane seemed to lose some of its control effectiveness but was not critical. The plane weighs 6 1/2 lbs with a 56" span and flown with O.S. 25FP engines. Seems to have ample power. Anyone have any experience with this plane or have any idea about my trimming problem. Maybe downthrust on the engines?? Thanks
05-06-2005, 09:12 PM
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RE: Trimming question on OV-10 Bronco
Hi,
check your wing and stab incidence,sounds like the wing is positive or the stab is negative in rwlation to each other.as far as downthrust what happens when the engines are idled after flying at full throtle.does the nose go up down or stay level?
check your wing and stab incidence,sounds like the wing is positive or the stab is negative in rwlation to each other.as far as downthrust what happens when the engines are idled after flying at full throtle.does the nose go up down or stay level?
05-07-2005, 06:29 AM
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RE: Trimming question on OV-10 Bronco
Scalebldr - Thanks for the reply - I did not get to the point of reducing the throttle to idle after full power which I need to do next I guess. I am going to check the incidence to make sure there are no problems there. The one other thing I should mention is that on the first take-off, the plane pitched-up quite steeply and after attempting to level out, required the down trim in the elevator to fly level. Reducing the throttle to land did not present any particular problems. Thanks again for the help.
05-07-2005, 06:55 AM
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RE: Trimming question on OV-10 Bronco
John:
What Scalebldr was leading into is that if the trim does not change with a different power setting the engines are angled correctly.
If the trim changes with power setting then the thrust line changes can decrease or eliminate this.
As you describe it I tend to agree with John - either the wing is too positive or the stab is too negative.
Cure? Best (and hardest) is to chop the plane apart and reset the stab. Second best is to remount the wing with less positive incidence. The easiest is to fly it with the down trim on the elevator.
You can ease this without any trouble by making the plane more nose heavy, if you still have the c/g range to do it. You have checked the c/g?
Bill.
What Scalebldr was leading into is that if the trim does not change with a different power setting the engines are angled correctly.
If the trim changes with power setting then the thrust line changes can decrease or eliminate this.
As you describe it I tend to agree with John - either the wing is too positive or the stab is too negative.
Cure? Best (and hardest) is to chop the plane apart and reset the stab. Second best is to remount the wing with less positive incidence. The easiest is to fly it with the down trim on the elevator.
You can ease this without any trouble by making the plane more nose heavy, if you still have the c/g range to do it. You have checked the c/g?
Bill.
05-07-2005, 06:59 AM
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RE: Trimming question on OV-10 Bronco
John:
A quick check on power trim: adjust the plane to level flight at full throttle, then chop the power. If the plane immediately pitches down you need down thrust. If it stays level the problem is indeed one of incidences on the wing and stab.
Bill.
A quick check on power trim: adjust the plane to level flight at full throttle, then chop the power. If the plane immediately pitches down you need down thrust. If it stays level the problem is indeed one of incidences on the wing and stab.
Bill.
05-09-2005, 12:29 PM
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RE: Trimming question on OV-10 Bronco
Guys - thanks for the suggestions and help. I will start my trimming process with eliminating the thrust issue and go from there. Thanks again
06-05-2005, 01:25 PM
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RE: Trimming question on OV-10 Bronco
John you didnt say if you had retracts installed. If so, did you balance it with the gear down or up? A friend of mine has one and he said it balanced with the wheels down, and when retracted it moves the CG rearward quite a bit, so he rebalanced with the gear in the retracted position. With the gear down it is nose heavy and required a lot of up elevator to become airborne.
If you balanced with the gear down, and then retract, it becomes tail heavy and will induce the nose up pitch you describe. He has since taken some of the nose weight out and had retrimmed. I've seen his OV10 fly and it looks great in the air, also it really moves out.
Pete
If you balanced with the gear down, and then retract, it becomes tail heavy and will induce the nose up pitch you describe. He has since taken some of the nose weight out and had retrimmed. I've seen his OV10 fly and it looks great in the air, also it really moves out.
Pete
