Hilltown, PA, USA
N47SS
Schempp-Hirth Standard Cirrus
The glider was being towed by an airplane for takeoff, when it was observed to bounce hard on the runway twice, then it assumed a steep nose up attitude. The tow rope broke, and the glider impacted the ground in a near vertical descent. The C-hook on the stabilator push rod, was found in front of, and not connected to the roller bearing on the stabilator. The pilot's flight experience was over 3,000 hours with about 84 hours in gliders. He had accumulated 28 hours in the accident glider, including 17 flights. This was the first glider the pilot had operated, that he was required to disassemble for storage and reassemble for flight. Witnesses reported the pilot experienced difficulty with the assembly process. A view window was located on top of the stabilator to check for proper engagement of the C-hook, and the AFTER ASSEMBLY checklist called for it to be used to check for proper assembly. A witness reported the pilot moved the control stick in the cockpit and observed movement of the flight controls, but he was not observed to actually check the view window for proper assembly. A check of another glider of the same make and model found it was possible to lock the stabilator in place on top of the vertical stabilizer, with the C-hook in the same place as found on the accident glider. In this configuration, the control rod that held the C-hook was pressed against the roller bearing and held in place by friction. However, the incorrect assembly was visible through the view window on top of the stabilator, and when the stabilator was held in place, it was still possible to move the cockpit control stick abut 1 inch forward or aft, with no corresponding movement on the stabilator.
History Of Flight On August 10, 2002, about 1350 eastern daylight time, a Schempp-Hirth Standard Cirrus, N47SS, was destroyed, when it collided with terrain during takeoff at the Philadelphia Gliderport (0PA0), Hilltown, Pennsylvania. The certificated private pilot was fatally injured. Visual meteorological conditions prevailed for the local flight. No flight plan had been filed for the personal flight that was conducted under 14 CFR Part 91. According to a witness, the pilot was in good spirits when he assembled the glider and prepared it for flight. The pilot was observed to perform a control check, which consisted of him moving the control stick in the cockpit and observing movement of the stabilator and ailerons. The witness reported that he observed movement of the control surfaces, but was not in a position to observe the control stick movements. No further flight control checks were observed. In preparation for takeoff from runway 25, the glider was attached to a 200-foot tow line and positioned behind the tow plane, a Cessna 305. A wing walker reported that he held the wings in a level position as the takeoff was initiated. As the glider gained speed, and the wing walker could no longer keep up with it, he released the wing, and turned his back to the takeoff, walking back to the starting point. A third witness reported seeing the glider still on the ground after the tow plane had become airborne. A fourth witness reported: "...The glider became airborne and began to rise above the tow plane. It appeared that after the glider continued to rise, the glider pilot took corrective action to get down to the correct position, but over-shot the mark....the glider appeared to be starting to PIO [pilot induced oscillation]...In the 2nd PIO, the glider did not appear to be excessively high - maybe 5 to 10 feet above the ground. In this second PIO, the glider did make contact with the ground. The glider then started a 3rd PIO, this time it got some what high - maybe 20 to 30 feet. The glider then headed down to the ground at a steeper angle than the previous two PIOs. Upon impact, I witnessed material parting company with the glider...The wings flexed downward severely, and I thought that at that time a wing might break...The glider bounced up, and then appeared to fly straight with wings level and the fuselage facing directly down the runway, at a slight angle of descent...Suddenly the glider appeared to accelerate and pitch up into a steep climb. It looked similar to the beginning of a winch launch. The climb angle continued to increase at a steady rate, and the glider slowed to a stall in a nose high attitude, which appeared to be well above 60 degrees above [the] horizon. The glider then quickly pitched downward and impacted in a nose down attitude." Another witness reported the ground roll of the glider appeared longer than normal, and also seeing the tow plane airborne while the glider was still on the ground. Several other witnesses reported similar observations, and also seeing the wing spoilers extended as the glider was climbing. The tow plane pilot reported that initially, the tow was normal. However, after becoming airborne, he felt his airplane being pulled nose left and nose low by the glider. Within about 3 seconds, the glider had disconnected from the tow plane. The tow plane pilot reported that he had not disconnected the glider and was not aware of how the separation occurred. PERSONNEL INFORMATION According to records from the Federal Aviation Administration (FAA), the pilot held a private pilot certificate with airplane single engine land, and instrument airplane ratings. In addition, he held a glider rating. The pilot was also a member of the Philadelphia Glider Council. According to records from the FAA, and the pilot's glider logbook, his total flight experience was about 3,084 hours, which included 84 hours in gliders. According to the pilot's glider logbook and records from the Philadelphia Glider Council, the pilot's glider experience included about 28 hours in the accident glider, consisting of at least 17 flights. A review of the types of gliders flown, revealed the accident glider was the first glider that was normally disassembled and stored in a trailer when not used, and which required assembly prior to flight. Witnesses reported that the pilot experienced difficulty with the assembly of the glider. However, one witness also reported that the pilot was able to recognize when the glider was not properly assembled. AIRCRAFT INFORMATION The stabilator was actuated through a series of pushrods and bell cranks, starting with the control stick in the cockpit. The stabilator pushrod connected to the stabilator with a C-hook. Once in place, the C-hook was prevented from backing off the roller bearing by an additional roller bearing that was located behind the C-hook. The glider was equipped with a locking tow hook, located on the underside of the fuselage, forward of the wheel. The hook was designed so that if the tow rope was pulled rearward, it would automatically disconnect. When the tow rope was pulling the glider, the latch was secured. A release mechanism for the tow rope was located on the left side of the instrument panel in the cockpit. The wingspan of the glider was 49.2 feet. AIRPORT INFORMATION The Philadelphia Gliderport was a private airport that was operated by the Philadelphia Glider Council. The runways were turf, with the length of the grass at less than 3 inches. The ground was hard. In the direction of takeoff, beyond the area of mowed grass, the terrain consisted of brush and grass about 2 to 3 feet high. The terrain in this area sloped down about 5 degrees, and trees were located on the sides. WRECKAGE AND IMPACT INFORMATION The glider came to rest in an area of mowed grass, on the airport, to the right side of runway 25. Examination of the turf runway revealed two ground scars where the grass had been scraped away and bare earth exposed. These ground scars were on a heading of 240 degrees magnetic, and were separated by 145 feet. The first ground scar was about 2,000 feet from the initiation of the takeoff roll. The scar was 13 feet long and 4 inches wide. The second ground scar was 28 feet long, and 4 inches wide, and in line with the first ground scar. On the second ground scar, the grass was more clearly scraped clear, and the ground was more visible. A third ground scar was found parallel to the second ground scar, and displaced 24 feet, 6 inches to the right. This ground scar was 8 feet, 6 inches long and about 1 1/2 inches wide. At the end of the second ground scar, pieces of curved plexiglas, and items that had been located inside the cockpit were found. A debris trail extended for 110 feet from the start of the second impact mark. The tow rope, which had failed near the tow plane attach point, was found beyond the second ground scar. The tow rope stretched toward the glider, but was not connected to the glider. The separated portion of the tow rope, which measured about 5 feet, had remained with the tow plane. The glider came to rest, about 740 feet from the start of the second ground impact mark, on a magnetic heading of 258 degrees. The glider was inverted, and pointed in a heading of 170 degrees magnetic. Small pieces of grass were found imbedded in the leading edge of the right wing. Both wings had multiple compressive fractures along their length. The wing spoilers were extended on both wings. The fuselage was crushed rearward and the fiberglass shell that retained the cockpit was shattered. The canopy ring was still attached to the cockpit structure. A functional check of the tow rope attach point revealed that it unlocked and released when the cockpit release was pulled, or the tow rope was pulled in a rearward direction. The aft fuselage was intact to the vertical stabilizer, where there was a circumferential fracture in the fiberglass. The vertical stabilizer was intact, with the separated rudder laying nearby. The stabilator was mounted on top of the vertical stabilizer, jammed in a leading edge up, trailing edge down position. The view window on the top of the stabilator, used to check engagement of the C-hook, was in place and not obscured. Flight control continuity was verified to the rudder and ailerons. Breaks were found in the elevator control system within the crushed cockpit area. All breaks occurred at other than connections between control rods, and all breaks were bright and granular in appearance. Stabilator control through the fuselage pushrods, and into the vertical stabilizer, was verified. The C-hook, which was mounted on the end of the stabilator control push rod and was used to engage the roller bearing on the stabilator, was found positioned in front of, and not connected to the roller bearing. MEDICAL AND PATHOLOGICAL INFORMATION Toxicological testing was conducted by the FAA Toxicology Accident Research Laboratory, Oklahoma City, Oklahoma. An autopsy was conducted on August 11, 2002, by Dr. Ian C. Hood, for Bucks County, Pennsylvania. ADDITIONAL INFORMATION On August 11, 2002, the flight control system of another Standard Cirrus was examined. When first observed, the glider was in a trailer with the wings and stabilator detached. The glider was removed from the trailer, and prepared for installation of the stabilator. The wings were not attached. To attach the stabilator to the vertical stabilizer, the trim was first locked in the forward position. Then the stabilator was positioned with the leading edge down about 45 degrees. It was then lowered, positioning the roller bearing in front of the C-hook. The stabilator was then rotated leading edge up to the horizontal position, while two alignment pins and a locking pin were engaged. Once the three pins were engaged, the stabilator was locked in place. After the stabilator had been installed correctly, it was removed. Examination of the stabilator found there was sufficient space forward of the roller bearing for the C-hook to reside. The stabilator was re-installed with the C-hook in front of, and not engaged with the roller bearing. In this configuration, it was still possible to lower the stabilator into position where it engaged the locking pins, and was locked in position. Looking through the view window on the top of the stabilator, it was possible to see that the C-hook was not engaged. No witnesses were located who observed the pilot look through the view window to determine if the C-hook was properly engaged prior to flight. With the C-hook forward of the roller bearing on the stabilator, the stabilator pushrod was held against the roller bearing by pressure and friction. In this configuration, it was possible to move the control stick and observe movement of the stabilator. However, the movement of the control stick was not smooth. In addition, when the stabilator was gripped, it was possible to move the control stick about 1 inch in either direction with no corresponding movement on the stabilator. Measurements were taken between the trailing edge of the stabilator, and the fixed portion of the stabilator, that was locked to the vertical stabilizer. With the stick in the full aft position, the trailing edge of the elevator was about 7/8 of an inch up, and with the stick full forward, the measurement was about 3 1/4 inches, trailing edge down. However, since this was a friction fit, and not secured by the C-hook, it was not possible to determine if this was the exact same configuration experienced by the pilot. According to the flight manual, movement of the stabilator was listed as + 2.65 inches, trailing edge up with the stick full back, and -1.77 inches trailing edge down, with the stick full forward. The flight manual for the glider contained an After Assembly checklist. Item # 7 states: "Is the hook of the elevator control rod properly inserted onto the bearing of the corresponding control fitting (Check through the inspection hole on the top of the elevator)." Item # 1 of the Before Take-off checklist states: "Check the function of the control surfaces. Do the controls reach the limit of their travel with sufficient ease and smoothness." A check of Safety Board records from 1964 through the date of this accident, revealed seven other Standard Cirrus accidents. None of the accidents involved an improperly attached stabilator. The aircraft wreckage was released to the Philadelphia Glider Council on August 11, 2002.
The pilot's improper pre-flight, and failure to follow procedures in the flight manual to determine that the stabilator was properly connected prior to flight, and which resulted in a loss of control while under tow, and uncontrolled impact with the ground.
Source: NTSB Aviation Accident Database
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