4/6/2011, you wrote: >Very true statement Larry. I have slammed my tail on the runway more than >once and the tie down ring on my tail bears the wear to attest to the fact. >------------------- >Strange. >I have 335 hours on my KR2 tricycle, and NEVER hit the tail. >I can stall onto the runway, or drop the mains on the runway at 35 to 40 >kts. >Phil Matheson +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
I suspect the wing is not really "stalled" at that point and that your ASI is probably off by 10 to 15 knots at that AOA. You're simple descending to the runway from the flair at minimum airspeed. Same goes with a tail dragger touching tail first. An interesting test would be to measure the angle of the firewall in the three point position (tri-gear ). Then lower the tail to the ground and measure the firewall angle again. If the change is less then approx 14 degrees (plus your wing set AOA, the wing is not stalled with the tail touching. My tail dragger KR, with a 24 inch stretch over a standard KR, 30 inch Diehl gear, wing set at 3.5 degrees, has the wing at 12 degees in the 3 point attitude. Again, just one man's opinion. Larry Flesner ------------------------------------------------------------------------------------------ Larry, I have a tri-gear plans-built KR-2 with standard Diehl gear. Stub wing is set at 3.5 degrees AOA in level attitude. With the tail skid pushed down 5 inches off the level concrete, my inclinometer shows an AOA of 14 degrees. With the tail skid on the concrete the AOA goes to 17.5 degrees. My conclusion: I would stall the wing before the tail skid touches the runway. Not accounted for is the low wing ground effect, static load on the gear and use of flaps on the above data versus actual flight performance. I suppose it would be possible to momentarily touch the skid to the runway by over controlling with PIO. Another possibility is planting the tail on the runway with max aft cg and full elevator deflection. I recall Boeing doing an over-rotation test on a 747 to prove to the FAA that the 747 was still flyable from the runway in that high AOA and aft cg situation. Boeing used a huge oak block bolted to the tail of the 747 as a skid. Hmm...maybe a little oak block would work on my KR-2. Another data point for my flight tests. Sid Wood Tri-gear KR-2 N6242, pimping for the DAR Mechanicsville, MD, USA [email protected]
