cchandler 0 #1 October 4, 2005 King Airs must fly jump run with the flaps set in "Approach". This flap setting lowers the nose/raises the tail, and greatly reduces the chances of a tail strike. Nearly every King Air tail strike has been because the flaps were not extended. The King Air flaps are powered by an electric motor which occasioally fails. Beware the operator who tries to get thru the weekend with inoperative flaps. Expect a tail strike. Also, dont forget about the "low pass" guys. The "Approach" flap setting, which is an inconvienient re-configuration during the climb, is way more important than a power reduction or the jump run speed. Lastly, regarding Center of Gravity. I continue to be amazed at the lack of knowledge regarding the relationship between CG and performance. Airplanes with aft CG's (within limits) have shorter takeoff rolls, climb faster and have lower stall speeds!! It's true; consult any accurate reference on aerodynamics. Airplanes stalling on jump run is generally not a CG issue. It is a pilot training and proficiency isssue. Granted, there are exceptions but if the plane "gets too slow" that is a result of pilot action - or inaction!! Be safe. Quote Share this post Link to post Share on other sites
AndyMan 7 #2 October 4, 2005 QuoteLastly, regarding Center of Gravity. I continue to be amazed at the lack of knowledge regarding the relationship between CG and performance. Airplanes with aft CG's (within limits) have shorter takeoff rolls, climb faster and have lower stall speeds!! It's true; consult any accurate reference on aerodynamics. Isnt' a lower stall speed a bad thing? I was under the impression that aft-CG played a big role in takeoff stalls, especially with Caravans? _Am__ You put the fun in "funnel" - craichead. Quote Share this post Link to post Share on other sites
cchandler 0 #3 October 4, 2005 "Isnt' a lower stall speed a bad thing?" No way dude. Would you rather have a canopy that stalled at 3 mph or 23 mph? Regarding CG during takeoff, I believe that any skydiving airplane that is loaded to capacity is within it's CG envelope. It may be overweight but by virtue of fully loading the plane, there will be weight both in the front and in the back - a balanced aircraft. Quote Share this post Link to post Share on other sites
billvon 2,395 #4 October 4, 2005 >Airplanes with aft CG's (within limits) have shorter takeoff rolls, climb > faster and have lower stall speeds!! It's true; consult any accurate > reference on aerodynamics. True in some aircraft, not true in others. It depends on the angle of incidence of the wings and tail, thrust line of the engine etc. For example, our grand caravan climbed faster and got off the ground faster with a forward CG; our pilot took data over several weekends. (For everyone else - what the poster is referring to is the effect that a rearward CG has on stabilizer lift. Stabilizers normally lift "down" - that is, they generate downward lift instead of upward lift like the wings. The farther back the CG, the less downward lift needed; thus at any given speed, induced drag goes down and available lift goes up as CG goes backward on a non-canard aircraft. As I mentioned above, sometimes that's not the whole story though.) Quote Share this post Link to post Share on other sites
cchandler 0 #5 October 4, 2005 The increase in performance is only partly due to a decrease in induced drag (and lets try to avoid an induced drag discussion). The increased performance is, accurately, from less total aerodynamic weight. I respect your pilots observations; however, I don't believe they would qualify as scientific data. The skydiving community is the only one that believes in this theory. Let's stop this misinformation about CG once and for all. Quote Share this post Link to post Share on other sites
billvon 2,395 #6 October 4, 2005 >I respect your pilots observations; however, I don't believe they >would qualify as scientific data. I agree. But in our case, our caravan climbs better with a forward CG. >Let's stop this misinformation about CG once and for all. Some planes climb better with a forward CG, some climb better with a rearward one. In all cases having a CG within limits is critical to safe operation of any aircraft. Quote Share this post Link to post Share on other sites
cchandler 0 #7 October 4, 2005 OK then, let's agree to perpetuate the myth. Quote Share this post Link to post Share on other sites
kallend 1,623 #8 October 5, 2005 Quote>I respect your pilots observations; however, I don't believe they >would qualify as scientific data. I agree. But in our case, our caravan climbs better with a forward CG. >Let's stop this misinformation about CG once and for all. Some planes climb better with a forward CG, some climb better with a rearward one. In all cases having a CG within limits is critical to safe operation of any aircraft. Two factors at work here - stability (which determines the allowable CG range) and trim. Trim is affected by a multitude of factors, such as high or low wing, tail located in the wake of the wing, engine thrustline position and alignment, fuselage length, tail volume coefficient... It is perfectly possible to have a situation in which a plane is stable and has a lifting tail in order to be in trim. In that case, trim drag would be minimized with a forward CG given that, in general, the wing is a more efficient lifting surface than the tail. JK - amateur airplane designer.... The only sure way to survive a canopy collision is not to have one. Quote Share this post Link to post Share on other sites
billvon 2,395 #9 October 5, 2005 > It is perfectly possible to have a situation in which a plane is stable >and has a lifting tail in order to be in trim It is also possible to have a situation where the plane is stable, the tail is lifting downwards - but a more-forward CG results in a trim conditions that generate less drag (i.e. better aligned elevator, a cleaner trim tab position) even though the amount of negative lift increases slightly. Quote Share this post Link to post Share on other sites
