Cherokee Six w/ Black leading edges
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Join Date: Jul 2012
Location: Mozambique
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Cherokee Six w/ Black leading edges
Hi,
I am flying a Cherokee six in Mozambique, you know how hot it gets here. We bought a Cherokee six with black painted leading edges. For some reason, I am not sure if this is THE factor, but this Cherokee six has less performance than the other ones we have. I am not sure if the black painted leading edges might contribute to the performance degradation we have been noticing. When we are on the ground and the sun is hitting the wing, you simply cannot hold your hand more than 5 seconds on the black stripe, it’s burning hot. Do you think it might influence the wings aerodynamic flow?
Regards,
JM
I am flying a Cherokee six in Mozambique, you know how hot it gets here. We bought a Cherokee six with black painted leading edges. For some reason, I am not sure if this is THE factor, but this Cherokee six has less performance than the other ones we have. I am not sure if the black painted leading edges might contribute to the performance degradation we have been noticing. When we are on the ground and the sun is hitting the wing, you simply cannot hold your hand more than 5 seconds on the black stripe, it’s burning hot. Do you think it might influence the wings aerodynamic flow?
Regards,
JM
Join Date: Feb 2009
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I'd look at differences in engine hours, wear and tear, propeller, governors, rigging and the like before I went to work on black leading edges which probably do more to protect from stone strikes than degrade performance in the heat. My aeroplane is dark blue but it goes faster, climbs better and uses the same fuel than lighter colored versions I've seen. The only difference I can see is I have a TAS ASI and OAT. The others an IAS ASI. I'll leave it to the 'real experts' on PPRuNe to guide you on influence on aerodynamics.
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Diiferential Expansion
It may not affect performance but I will bet money that it stretches the skins at different rates in the wing. I had an ultralight that I did a repair on once that had dark blue leading edges and thin wing skins and you could hear the skins moving in the heat. White is the colour I like the most on cars and aeroplanes.
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Have a look at wing rigging. There can be quite a difference between flap & aileron settings between Pipers. The maintenance manual describes a rigging jig. But if you get 2 or 3 side by side and put a 1m piece of wood along the bottom of the wing touching the flap / aileron trailing edge then look at the gap between the wood and the rear part of the actual wing, you'll very quickly get an idea if one is different. There should be about 5mm gap. The better take-off cherokees might have more.
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Actually, the easier way is to look at the distance between the flap trailing edge and the bottom of the fuselage (some LAME's count exposed threads on the adjustment turnbuckle) then look at the aileron trailing edges compared with the flaps.
Another common differences are incorrect calibration of the tacho (ie you are doing more or less RPM than you think).
Cruise speed on the Cherokee 6 varies a bit depending on CofG position. Does one aircraft carry more junk? Or radio's down the back?
Another common differences are incorrect calibration of the tacho (ie you are doing more or less RPM than you think).
Cruise speed on the Cherokee 6 varies a bit depending on CofG position. Does one aircraft carry more junk? Or radio's down the back?
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The actual power output of any engine/prop combo is never identical to the next one & ASI's are also never identical even in the big birds. So end result is as has been mentioned here already if yr tach is saying one thing then that doesn't mean diddly poo in reality:-) CofG also has an effect on low power airframes as someone else eluded to already.
I recall flying an AC50 many years ago that was a dog compared t the others I flew, swore it was bent!:-)
Even the large Airliners have a perf degradation factor entered into the FMG's to help get the best optimum out of the airframe/engine combination, at GA level the same would apply but it's not accurately known.
As for the black LE's? Well hardly any effect would be appreciable I'd say
No two planes, no two pilots are the same.
Wmk2
I recall flying an AC50 many years ago that was a dog compared t the others I flew, swore it was bent!:-)
Even the large Airliners have a perf degradation factor entered into the FMG's to help get the best optimum out of the airframe/engine combination, at GA level the same would apply but it's not accurately known.
As for the black LE's? Well hardly any effect would be appreciable I'd say
No two planes, no two pilots are the same.
Wmk2
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As others have said it may end up being you have one aircraft that is a dog and one that is not.
However I would check the rigging and start at the cable tension on the ailerons.
Sometimes when this has dropped tension they look ok on the ground but in flight the airflow gives in upward deflection. Once tensioned correctly they are flush and match airfoil of the wing.
If you have the upward deflection you may be producing less lift on that section of the wing, correct tension also helps with the old lullaby wing roll on autopilots.
However I would check the rigging and start at the cable tension on the ailerons.
Sometimes when this has dropped tension they look ok on the ground but in flight the airflow gives in upward deflection. Once tensioned correctly they are flush and match airfoil of the wing.
If you have the upward deflection you may be producing less lift on that section of the wing, correct tension also helps with the old lullaby wing roll on autopilots.
