Narrative:

I departed in an aviat A1B husky on RF8001 hydraulic wheel skis. The mission was a local flight to make several ski landings off airport on snow at an area where I land quite frequently in winter. After departing I continued the climb northeast and lowered the skis. After leveling at 2;500 ft MSL; I continued northeast bound. Approaching the ski landing area; I descended; overflew the landing area and noted good air and light winds favoring a northeast landing as well as a light coating of new snow over the landing area. I continued and set up for a downwind with 2 notches of flap at 70 mph and set up for a low approach at 100 ft AGL to verify the wind and landing zone -- all looked good so I climbed back up to a pattern altitude and set full flap on base; verified the skis were down and completed remainder of landing checks. I landed normally and smoothly; came to a full stop and then set up for a takeoff straight ahead; planning a few more landings. As I broke snow on takeoff; I noted movement to my left. I glanced that way and saw that the left ski had rotated 90 degrees to a tip-up vertical position. I focused on flying the aircraft to a safe altitude straight ahead; leaving configuration alone. The aircraft seemed very docile in controllability. The right ski remained down and normal. Once at a safe altitude; I gently reduced flaps one notch ... All seemed ok; so I made a gentle turn back to the southwest toward my original departure airport. I continued the climb to 2;500 ft MSL and called on the company frequency that I had a ski malfunction. Company notified ATC radio and had them contact our company; who made contact with me on company frequency. Once level; I gradually reduced flap and set power to maintain 70 mph; which had been a docile airspeed so far. I completed cruise checks. I noticed that the rear cable on the left ski was loose -- by opening the left window and sticking my head out I could see that part of the cable was still attached to the left side of the fuselage and that the cables from the aft of the ski (a loop connected to both the left and right side 'wings' that compromise the tail of the ski) was still attached. The clevis pin and 'key ring' that holds these two together; in a 'Y' connection; had both departed; with no tension on the aft 'tail' of the ski; the tip was free to rotate up. The tail of the ski was now hanging vertical and well below the normal plane of the right ski. This would make a safe landing tricky. The husky; while slow from the large drag from the 'barn door' now hanging left and requiring more power and right rudder than usual; was otherwise easily controllable. There was some buffeting on the left horizontal but was felt as a rumbling vibration. There was no roll or unusual stick forces required. After discussion with company; I advised ATC that I would be landing at on the lake which is adjacent to the airport. I felt this would be more forgiving surface in the event of a ground loop tendency or landing; and I did not want to risk changing configuration from skis down to wheels down (to land on the paved airport runway). Our company would easily be able to access the plane once down on the lake; and in the event of trouble; EMS/rescue would have easy access; too. (The lake was currently notamed closed as it is the float operations lake in the summer.) while I was approaching the landing environment; the state DOT (department of transportation) headed to the lake to confirm the area I intended to land on was suitable. I believe they also had a fire rescue vehicle waiting at the lake edge. Our company was there as well. After circle or two overhead and a good to go from DOT; I set up a minimum descent shallow approach to land in the decided upon area. As the left ski aft tail touched gently first; with a power on minimum descent; it gradually began to rotate into position as I worked the aircraft lower. Both skis eventually slid on normally with no trouble or damage to the aircraft. Other than the separated cables; due to the departure of the clevis pin and ring; there was no damage to the aircraft. The company brought a threaded bolt and constellation nut with a cotter pin; installed same and checked aircraft over to be airworthy. I flew it off the lake and cycled wheels down for a normal uneventful landing back at the runway at the airport. Soon thereafter we informed the ski manufacturer of the problem. He advised that this was the second known incident of this problem. In march; RF-ski issued 'service letter 1' for replacement of attached hardware. Installation of this more robust and secure hardware would have prevented the incident I experienced. However; the design of the skis is such that (since tension from the rear cable is required to keep the tips of the skis down in flight) it is still subject to a single point of failure. There is no safety cable backup. Therefore; a frayed cable; a pulled out attach point or a broken aft ski 'tailoring' for example; all could lead to same scenario.

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Original NASA ASRS Text

Title: An Aviat A1B Husky's left aft cable attach bolt failed after takeoff causing the ski to rotate 90 degrees nose up so the pilot diverted; landing safely on a frozen lake where repairs were make to the ski attach points.

Narrative: I departed in an Aviat A1B Husky on RF8001 hydraulic wheel skis. The mission was a local flight to make several ski landings off airport on snow at an area where I land quite frequently in winter. After departing I continued the climb northeast and lowered the skis. After leveling at 2;500 FT MSL; I continued northeast bound. Approaching the ski landing area; I descended; overflew the landing area and noted good air and light winds favoring a northeast landing as well as a light coating of new snow over the landing area. I continued and set up for a downwind with 2 notches of flap at 70 MPH and set up for a low approach at 100 FT AGL to verify the wind and landing zone -- all looked good so I climbed back up to a pattern altitude and set full flap on base; verified the skis were down and completed remainder of landing checks. I landed normally and smoothly; came to a full stop and then set up for a takeoff straight ahead; planning a few more landings. As I broke snow on takeoff; I noted movement to my left. I glanced that way and saw that the left ski had rotated 90 degrees to a tip-up vertical position. I focused on flying the aircraft to a safe altitude straight ahead; leaving configuration alone. The aircraft seemed very docile in controllability. The right ski remained down and normal. Once at a safe altitude; I gently reduced flaps one notch ... all seemed OK; so I made a gentle turn back to the southwest toward my original departure airport. I continued the climb to 2;500 FT MSL and called on the company frequency that I had a ski malfunction. Company notified ATC radio and had them contact our company; who made contact with me on company frequency. Once level; I gradually reduced flap and set power to maintain 70 MPH; which had been a docile airspeed so far. I completed cruise checks. I noticed that the rear cable on the left ski was loose -- by opening the left window and sticking my head out I could see that part of the cable was still attached to the left side of the fuselage and that the cables from the aft of the ski (a loop connected to both the left and right side 'wings' that compromise the tail of the ski) was still attached. The clevis pin and 'key ring' that holds these two together; in a 'Y' connection; had both departed; with no tension on the aft 'tail' of the ski; the tip was free to rotate up. The tail of the ski was now hanging vertical and well below the normal plane of the right ski. This would make a safe landing tricky. The Husky; while slow from the large drag from the 'barn door' now hanging left and requiring more power and right rudder than usual; was otherwise easily controllable. There was some buffeting on the left horizontal but was felt as a rumbling vibration. There was no roll or unusual stick forces required. After discussion with company; I advised ATC that I would be landing at on the lake which is adjacent to the airport. I felt this would be more forgiving surface in the event of a ground loop tendency or landing; and I did not want to risk changing configuration from skis down to wheels down (to land on the paved airport runway). Our company would easily be able to access the plane once down on the lake; and in the event of trouble; EMS/rescue would have easy access; too. (The lake was currently NOTAMed closed as it is the float operations lake in the summer.) While I was approaching the landing environment; the State DOT (Department of Transportation) headed to the lake to confirm the area I intended to land on was suitable. I believe they also had a fire rescue vehicle waiting at the lake edge. Our company was there as well. After circle or two overhead and a good to go from DOT; I set up a minimum descent shallow approach to land in the decided upon area. As the left ski aft tail touched gently first; with a power on minimum descent; it gradually began to rotate into position as I worked the aircraft lower. Both skis eventually slid on normally with no trouble or damage to the aircraft. Other than the separated cables; due to the departure of the clevis pin and ring; there was no damage to the aircraft. The company brought a threaded bolt and constellation nut with a cotter pin; installed same and checked aircraft over to be airworthy. I flew it off the Lake and cycled wheels down for a normal uneventful landing back at the runway at the airport. Soon thereafter we informed the ski manufacturer of the problem. He advised that this was the second known incident of this problem. In March; RF-SKI issued 'Service Letter 1' for replacement of attached hardware. Installation of this more robust and secure hardware would have prevented the incident I experienced. However; the design of the skis is such that (since tension from the rear cable is required to keep the tips of the skis down in flight) it is still subject to a single point of failure. There is no safety cable backup. Therefore; a frayed cable; a pulled out attach point or a broken aft ski 'tailoring' for example; all could lead to same scenario.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.