drseti wrote:Alex, are you approaching in a glide, or carrying power into the flare? If the latter, you might be seeing gyroscopic precession when you raise the nose, caused by the not inconsiderable torque the Rotax 912 develops. Try gliding at idle power on final to see if that corrects the yaw tendency in the flare.
Come to think of it, Paul, the pattern of yaw-pitch coupling I've experienced is indeed consistent with gyroscopic precession... Transition with some power into a level flight would produce a gyroscopic right yaw. Counteract with left rudder and you'll get gyroscopic pitch up on that transition with resulting balloon.
Release left rudder and pitch slightly down to bleed excessive pitch and gyroscopic effect start yawing to the left...
Lots of work... Better glide with minimum prop rotation in flare then. Thinking back I may be in a habit of cutting to low idle right *after* rotation into a flare is completed.
What strange is that I do not recall noticeable gyroscopic effects in the two other planes. Normally they are considered negligible in tricycles because control surfaces provide enough input in all phases of flight.
I've noticed that Sting S3 does not recommend slips with full flaps citing large area of negative air pressure generated behind them affecting tail surfaces. Hence in a ground effect with full flaps the efficiency of Sting's tail group may be diminished and there's nothing much left to counteract gyroscopic forces in yaw/pitch coupling which normally would be masked by effective empennage.
Tecnam Sierra has more aerodynamic (full surface) flaps, that do not produce as much of a wake and Evektor with similar flaps has *very* low wing with tail group well above the flaps wake.
If this is correct with this in mind one also has to be very careful when practicing stalls with full flaps. If spin would develop it most likely will be unrecoverable due to aerodynamic blanketing of the tail group by turbulence from flaps. Significant percentage of Sting accidents in NTSB reports are due to spins including couple training flights with CFIs during stall practice.
Every plane has its own set of quirks. I find that every new LSA I fly teaches me to be a better pilot in its very own way...
NTSB Identification: ERA11LA427
14 CFR Part 91: General Aviation
Accident occurred Friday, July 29, 2011 in Sarasota, FL
Aircraft: TL ULTRALIGHT SRO STING S3, registration: N2442
Injuries: 1 Fatal,1 Serious.
...
On July 29, 2011, about 1247 eastern daylight time, a special light sport airplane (SLSA) TL Ultralight Sro Sting S3, N2442, registered to N2442 Aviation, LLC, operated by Universal Flight Training, LLC, was lost from radar and crashed about 12 nautical miles southeast of the Sarasota/Bradenton International Airport (SRQ), Sarasota, Florida. Visual meteorological conditions prevailed at the time and flight plan information is unknown for the 14 Code of Federal Regulations (CFR) Part 91 instructional local flight from the SRQ airport. The airplane sustained substantial damage, and the certified flight instructor (CFI) sustained serious injuries while the pilot-rated student was fatally injured. The flight originated from SRQ about 1230.
According to the Federal Aviation Administration (FAA) inspector-in-charge, the purpose of the flight was checkout of the pilot-rated student. After departure, the flight proceeded to a practice area southeast of SRQ, and while performing a power off stall, the airplane entered a spin, which the CFI was unable to recover. The airplane impacted the canopy of a large oak tree before coming to rest at the base of the oak tree. The CFI was able to exit the airplane; however, due to his injuries, waited on the ground next to the airplane for rescue personnel. The pilot-rated student had to be extricated from the airplane. Both occupants were airlifted by helicopter to a hospital in St. Petersburg, Florida.
NTSB Identification: WPR12FA295
14 CFR Part 91: General Aviation
Accident occurred Thursday, July 05, 2012 in Piru, CA
Aircraft: TL ULTRALIGHT SRO STINGSPORT, registration: N177N
Injuries: 2 Fatal.
...
On July 5, 2012, about 1324 Pacific daylight time, a TL Ultralight SRO Stingsport, N177N, was substantially damaged when it impacted terrain near Piru, California. The airplane was registered to and operated by the pilot under the provisions of Title 14 Code of Federal Regulations Part 91. The certified flight instructor and commercial pilot receiving instruction were fatally injured. Visual meteorological conditions prevailed and no flight plan was filed for the instructional flight. The local flight originated from Whiteman Airpark, Van Nuys, California, at 1300.
Multiple witnesses driving on Highway 126 within the vicinity of the accident site reported observing the accident airplane descending in a nose low attitude while spinning in a counter-clockwise direction before it descended below a tree line....
Note that full flaps stall is required to demonstrate skill in instructional flight.
That's 2 out of 3 recorded by NTSB cases. Add the similar spin accident in Australia - this would get to 3 out of 4.... I guess I limit my practice to incipient stall in this plane ::)
One thing that bugs me somewat about LSA industry is that handling charachteristics of aircraft apprear to be not taken seriously. Evektors had long and well documented by NTSB history of loss of the control during rollout due to poor nose gear stability at higher speeds. Sting may apparently have some issues with stall/spin. These normally are inherent design flaws - fix them and probably this would end up to be a different model... I'm curious how are aerodynamic/mechanical designs wetted for overall soundness in LSA industry?
