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Hi everyone,
We have completed about 50% of our test flying regime, and can now provide additional information for the in-flight performance with profiled horisontal stabiliser ribs.
The horisontal stabilisers were set to -3 degrees incidence with the profiled ribs, instead of the usual -4 called for by the plans. This requires no modifications to the kit, just removing the spacers is sufficient. The elevators trail straight-behind in the cruise, which suggests this angle is efficient, at least at lighter weights.
Control with elevator feels crisper than with flat ribs, control inputs feel sharp and effective - but the response of the aircraft to elevator control has not become 'twitchy'. The rudder does feel massively powerful at speed, but this is apparently normal for a Bearhawk(?).
Longitudinal stability tests have been completed, and show very positive stability characteristics - the Bearhawk rapidly annuls any in-flight disturbance. There was no tendency to 'porpoise', just an immediate return to level flight.
Observation during landing shows about 30-40% control deflection is required during approach at 50KIAS at 3 notches flap, leaving ample control for the flare or slower approaches. Perhaps 80%-90% elevator is required to keep the speed back around 45KIAS with 4 notches (resulting is a massively steep descent profile) so a small blip of power is required in the flare, however this is still very controllable. Power-on approaches relieve this problem to some extent.
Speeds are too variable from aircraft to aircraft to give a meaningful comparison, but certainly some reduction in drag exists. Both the improved aerodynamic shape of all three stabiliser surfaces, as well as the reduced profile as seen by the oncoming airflow. I suppose that the induced drag remains approximately the same.
I hope someone finds that useful!
Jonathan
We have completed about 50% of our test flying regime, and can now provide additional information for the in-flight performance with profiled horisontal stabiliser ribs.
The horisontal stabilisers were set to -3 degrees incidence with the profiled ribs, instead of the usual -4 called for by the plans. This requires no modifications to the kit, just removing the spacers is sufficient. The elevators trail straight-behind in the cruise, which suggests this angle is efficient, at least at lighter weights.
Control with elevator feels crisper than with flat ribs, control inputs feel sharp and effective - but the response of the aircraft to elevator control has not become 'twitchy'. The rudder does feel massively powerful at speed, but this is apparently normal for a Bearhawk(?).
Longitudinal stability tests have been completed, and show very positive stability characteristics - the Bearhawk rapidly annuls any in-flight disturbance. There was no tendency to 'porpoise', just an immediate return to level flight.
Observation during landing shows about 30-40% control deflection is required during approach at 50KIAS at 3 notches flap, leaving ample control for the flare or slower approaches. Perhaps 80%-90% elevator is required to keep the speed back around 45KIAS with 4 notches (resulting is a massively steep descent profile) so a small blip of power is required in the flare, however this is still very controllable. Power-on approaches relieve this problem to some extent.
Speeds are too variable from aircraft to aircraft to give a meaningful comparison, but certainly some reduction in drag exists. Both the improved aerodynamic shape of all three stabiliser surfaces, as well as the reduced profile as seen by the oncoming airflow. I suppose that the induced drag remains approximately the same.
I hope someone finds that useful!
Jonathan
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