Narrative:

Glider xx is an experimental category, open class glider designed for racing. Wingspan 55' length 27' seat 1, glide ratio 40/1 designed xa manufactured xb, one of 40 of this type manufactured from xa to xc. The tail confign of this glider is that of a V similar to the small aircraft. Unlike the small aircraft the glider tail is designed to fold to vertical for transportation in its trailer with the removal of one pin in the tail spar root. Prior to this flight when the tail had been unfolded the left tail had been allowed to fold past vertical to rest against the right tail. In this position the drive mechanism to the left tail became disconnected so that when assembled the elevator could be pushed down but could not be pulled nose up. Because of control balance and interaction it was not apparent on the ground that the surface was not properly connected. On takeoff the glider flew well for the first 200' above ground except that the nose was yawed to the left and did not follow the tow plane well. I was not alarmed by this behavior because open class gliders have poor yaw response at the best of times. Above it became more apparent that there was a problem because the glider required full aft stick to keep the nose up and would not respond to right rudder pedal. Having read a report of a similar failure which happened to the designer in 1968, I knew immediately what had gone wrong with the controls. Loss of control of the left V tail left me with a glider which would fly at 60-70 mph (2VSO) with full aft stick. Without right rudder response the roll rate to the right was limited to perhaps 1 degree per second, accompanied with substantial yaw to the left. Limited pitch control left me without the use of the flaps which deflect up to 90 for landing because they cause nose down pitch which would be uncontrollable. Without flaps the glider would have to be landed with a glide ratio of 35/1 which is about 150' per mi limiting the choices. With these limitations in mind, I chose to make a landing on runway 11 at worcester which is 7000' with unpopulated apches. The landing was successful with no damage to the glider and no injuries. The glider touched down 1500' past the threshold at 80 mph with wings level and the nose yawed 15 to the left. The uncorrectable yaw caused the glider to ground loop off the runway to the left. The problem would have been prevented with a positive control check after rigging the glider. The rigging procedure was interrupted and the positive check was omitted on this occasion. Unlike powered aircraft, the positive control check is a standard procedure with gliders because the problem of misrigged controls is relatively more common with gliders than with power aircraft which are seldom disturbed except by mechanics.

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Original NASA ASRS Text

Title: PLT OF SPN EXPERIENCES PARTIAL LOSS OF ACFT CTL.

Narrative: GLIDER XX IS AN EXPERIMENTAL CATEGORY, OPEN CLASS GLIDER DESIGNED FOR RACING. WINGSPAN 55' LENGTH 27' SEAT 1, GLIDE RATIO 40/1 DESIGNED XA MANUFACTURED XB, ONE OF 40 OF THIS TYPE MANUFACTURED FROM XA TO XC. THE TAIL CONFIGN OF THIS GLIDER IS THAT OF A V SIMILAR TO THE SMA. UNLIKE THE SMA THE GLIDER TAIL IS DESIGNED TO FOLD TO VERTICAL FOR TRANSPORTATION IN ITS TRAILER WITH THE REMOVAL OF ONE PIN IN THE TAIL SPAR ROOT. PRIOR TO THIS FLT WHEN THE TAIL HAD BEEN UNFOLDED THE LEFT TAIL HAD BEEN ALLOWED TO FOLD PAST VERTICAL TO REST AGAINST THE RIGHT TAIL. IN THIS POSITION THE DRIVE MECHANISM TO THE LEFT TAIL BECAME DISCONNECTED SO THAT WHEN ASSEMBLED THE ELEVATOR COULD BE PUSHED DOWN BUT COULD NOT BE PULLED NOSE UP. BECAUSE OF CONTROL BALANCE AND INTERACTION IT WAS NOT APPARENT ON THE GND THAT THE SURFACE WAS NOT PROPERLY CONNECTED. ON TKOF THE GLIDER FLEW WELL FOR THE FIRST 200' ABOVE GND EXCEPT THAT THE NOSE WAS YAWED TO THE LEFT AND DID NOT FOLLOW THE TOW PLANE WELL. I WAS NOT ALARMED BY THIS BEHAVIOR BECAUSE OPEN CLASS GLIDERS HAVE POOR YAW RESPONSE AT THE BEST OF TIMES. ABOVE IT BECAME MORE APPARENT THAT THERE WAS A PROBLEM BECAUSE THE GLIDER REQUIRED FULL AFT STICK TO KEEP THE NOSE UP AND WOULD NOT RESPOND TO RIGHT RUDDER PEDAL. HAVING READ A REPORT OF A SIMILAR FAILURE WHICH HAPPENED TO THE DESIGNER IN 1968, I KNEW IMMEDIATELY WHAT HAD GONE WRONG WITH THE CONTROLS. LOSS OF CONTROL OF THE LEFT V TAIL LEFT ME WITH A GLIDER WHICH WOULD FLY AT 60-70 MPH (2VSO) WITH FULL AFT STICK. WITHOUT RIGHT RUDDER RESPONSE THE ROLL RATE TO THE RIGHT WAS LIMITED TO PERHAPS 1 DEG PER SECOND, ACCOMPANIED WITH SUBSTANTIAL YAW TO THE LEFT. LIMITED PITCH CONTROL LEFT ME WITHOUT THE USE OF THE FLAPS WHICH DEFLECT UP TO 90 FOR LNDG BECAUSE THEY CAUSE NOSE DOWN PITCH WHICH WOULD BE UNCONTROLLABLE. WITHOUT FLAPS THE GLIDER WOULD HAVE TO BE LANDED WITH A GLIDE RATIO OF 35/1 WHICH IS ABOUT 150' PER MI LIMITING THE CHOICES. WITH THESE LIMITATIONS IN MIND, I CHOSE TO MAKE A LNDG ON RWY 11 AT WORCESTER WHICH IS 7000' WITH UNPOPULATED APCHES. THE LNDG WAS SUCCESSFUL WITH NO DAMAGE TO THE GLIDER AND NO INJURIES. THE GLIDER TOUCHED DOWN 1500' PAST THE THRESHOLD AT 80 MPH WITH WINGS LEVEL AND THE NOSE YAWED 15 TO THE LEFT. THE UNCORRECTABLE YAW CAUSED THE GLIDER TO GND LOOP OFF THE RWY TO THE LEFT. THE PROBLEM WOULD HAVE BEEN PREVENTED WITH A POSITIVE CONTROL CHECK AFTER RIGGING THE GLIDER. THE RIGGING PROC WAS INTERRUPTED AND THE POSITIVE CHECK WAS OMITTED ON THIS OCCASION. UNLIKE POWERED ACFT, THE POSITIVE CONTROL CHECK IS A STANDARD PROC WITH GLIDERS BECAUSE THE PROBLEM OF MISRIGGED CONTROLS IS RELATIVELY MORE COMMON WITH GLIDERS THAN WITH POWER ACFT WHICH ARE SELDOM DISTURBED EXCEPT BY MECHANICS.

Data retrieved from NASA's ASRS site as of August 2007 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.