Mark L and I were having a short conversation off line about the "Aftermath KR-2", controls and spins. I started a write up about incipient spins vs fully developed spins. Then I realized that many pilots may not know the difference. When one talks about having done spin testing in an aircraft, knowing whether the pilot has done incipient spin entry and recovery vs fully developed spins and recover is important. So I thought I would share my thoughts with the group. You will have to decide for yourselves whether it is wisdom or just windy.
---------------- Here's why the 20? nose down piqued my interest so much in the accident video. NASA Spin Mode Classification Spin mode Angle-of-attack range, degrees Flat 65 to 90 Moderately flat 45 to 65 Moderately steep 30 to 45 Steep 20 to 30 Assuming little forward motion, 20? nose down from the horizon translates into roughly 70? angle of attack. According to the Spin Mode Classification, that makes it a flat spin. Even if the AOA was less than 65? due to some forward motion, it was surely greater than 45?, which still makes it moderately flat. Without an engine running to force a flat spin, that says Aft CG, but could also be saying lack of stabilizer and/or controls or a combination of aft CG and small stabilizers. There wasn't any indication in the accident report as to how long the pilot allowed the spin to develop before attempting recovery. 3 turns is typical to fully develop a spin. I have done as many as 15 turns when I had an aerobatic Biplane. My biplane typically held roughly 60 - 70? nose down in a spin, which would translate to 20 - 30? AOA. According to the Spin Mode Classification, that is a steep spin. It always recovered within 1/4 turn no matter how long I allowed the spin to develop. Most aerobatic aircraft have large stabilizers and controls, which makes recovery from an incipient spin and a fully developed spin the same. Most homebuilt, fast, slick aircraft lack the stabilizers and control authority to recover like an aerobatic aircraft. That is by design as large controls like an aerobatic plane has will get very heavy at speed unless you install helpers like spades on the ailerons and anti-servo tabs on the elevator. That starts adding unnecessary weight and complexity. Spins were one of the knocks on the Piper Tomahawk. They recovered quite easily from an incipient spin, but when a spin is allowed to fully develop, the pilot had to make the correct motions (full opposite rudder and full forward elevator), then be patient while the plane slowly recovered over the course of 2 - 3 additional rotations. That's enough to scare the socks off most pilots, including the test pilot that did the spin testing for Piper. Most pilots that allowed a spin to fully develop in that plane would never do so again, and that became the legend of many tales about the terrors of the Traumahawk. I've done a number of incipient spins in the Tomahawks, but never allowed a spin to continue to develop as I saw no reason to go share the same experience as the Piper test pilots. Most pilots have never done a fully developed spin. I would dare to say that most don't know the difference between an incipient spin and a fully developed spin. The recovery techniques are the same, but depending on the plane the recovery from a fully developed spin may be much slower and it may seem like the plane is not going to recover. And if the CG is a bit too far aft, it very well may not recover. (that's one of the reasons for CG range differences between standard, utility, and aerobatic categories on some planes) When the spin recovery is delayed, many pilots will start to panic and will attempt other strategies like deploying flaps, rolling the the ailerons back and forth, and powering up and down during the spin. Such techniques usually delay the spin recovery and may cause the spin to further develop or possibly go flat. I have not spun my KR more than 1 turn. To me, one turn spins and recovery proved it would recover from an incipient spin. I simply do not care about recovery from a fully developed spin as there is no reason why I would ever allow a spin to fully develop while flying this aircraft. I saw no reason to take the additional risk of spin testing for something I will never do. Jeff Scott Los Alamos, NM > >
