NTSB Factual Report

HISTORY OF FLIGHT

On May 26, 2001, at approximately 1350 central daylight time, a Cessna 150, N5617E, was destroyed when it impacted terrain during the takeoff initial climb while towing a Schleicher Ka-6E glider, N9915X, at the Mid-America Industrial Airport, Pryor, Oklahoma. The glider did not sustain any damage. The private pilot flying the airplane sustained fatal injuries, and the private pilot flying the glider received minor injuries. The airplane was registered to and operated by Tulsa Skyhawks, Inc., Bixby, Oklahoma. The glider was owned and operated by its pilot. Visual meteorological conditions prevailed, and a flight plan was not filed for the 14 Code of Federal Regulations Part 91 tow flight. The local flight was originating at the time of the accident.

The glider pilot stated in an interview with the NTSB investigator-in-charge (IIC), that at the time of the takeoff roll, the wind was out of the west, approximately 15 knots with gusts. He stated that he maintained a crab of 15 degrees into the wind in order to track down the runway 17 centerline. Shortly after lift-off, the glider encountered "severe turbulence" and was caught in an "extreme updraft." He recalled looking up at the sky, losing sight of the tow airplane, and being "jarred about the cockpit" while attempting to disengage the towrope. He further recalled that his altimeter was indicating 440 feet agl approximately midway down the runway at the time he released the towrope, and he estimated the tow airplane was 150 feet lower than his glider. He stated that "much of [the] runway was still ahead even though the glider had reached near pattern altitude already". While on downwind, he noticed some smoke at the end of the runway. He completed a normal traffic pattern and landed on the runway. Upon landing, he realized that the tow airplane had impacted the ground and was engulfed in flames on the east side of the runway.

The glider pilot mentioned that his glider had a tendency for the trim lever to release from its "full nose down" trim position, which is the recommended takeoff trim lever position, and "snatch" back to the "full nose up" position. He remembered having to push forward during the initial climb to counteract a nose up effect.

Witnesses were interviewed by the NTSB investigator-in-charge and by the FAA aviation safety inspector. One eye witness, who was located at the approach end of runway 17, stated that the glider was drifting to the left of the centerline and out of position. He observed the glider gain altitude "relatively abrupt" and was able to detect that the glider was "decidedly higher" than the tow airplane. He saw the glider break away to the east and thought the problem was over. He continued to observe the tow airplane and stated that from his position the airplane appeared to level off momentarily, and then "nose dived and impacted the ground."

PERSONNEL INFORMATION

The 44-year-old private pilot of the tow airplane held airplane single-engine land, airplane instrument, and glider ratings. The pilot was issued a third class medical certificate on May 19, 1999, with no limitations or restrictions. The pilot had accumulated approximately 583 total flight hours, of which 537 hours were in single-engine airplanes and 45 hours were in gliders. He had accumulated approximately 8.3 hours in the previous 30 days, of which 3.5 hours were in the same make and model as the accident airplane. The pilot completed his last biennial flight review on May 29, 1999, in a Grob 103 glider.

The 79-year-old private pilot/owner of the glider held airplane single-engine land and glider ratings. He held a valid third class medical certificate that was issued on December 9, 1999. The only limitation to the medical certificate was that the pilot was to wear corrective lenses while exercising the privileges of his airman certificate.

A review of the glider pilot's flight logbooks revealed that on April 9, 1999, he completed a biennial flight review in a Blanik L-23 glider. The logbooks also revealed that as of May 1, 2001, he had logged a total flight time of 971.8 hours, of which 299.5 hours were in airplanes and 672.3 hours were in gliders. The last three entries in the pilot's glider logbook were 3 hours 10 minutes on September 2, 2000, 20 minutes on February 3, 2001, and 25 minutes on May 19, 2001. The last two entries in the pilot's airplane logbook were 25 minutes on February 3, 2000, and 50 minutes on May 9, 2001.

AIRCRAFT INFORMATION

The 1959-model Cessna 150 was a high wing, single-engine, two-place airplane, which had been modified with a Horton STOL kit, a tow hook, and a Lycoming O-320 engine rated at 150 horsepower. The airplane underwent its last annual inspection on February 2, 2001, at an aircraft total time of approximately 3,996.0 hours. At the time of the accident, the airplane had accumulated approximately 4,016.0 total flight hours.

The 1967-model Schleicher Ka-6E had a wood structure with a wingspan of 49.2 feet. The wing area was 133.5 square feet with an aspect ratio of 18.1. The aircraft's empty weight was 419 pounds and its maximum gross weight was 661 pounds. Examination of the aircraft's maintenance records revealed that the glider underwent its last annual inspection on March 24, 2001, at an aircraft total time of 1,165 hours and 16 minutes. At the time of the accident, the glider had accumulated 1,165 hours and 41 minutes. No evidence of uncorrected maintenance discrepancies was noted in the records.

A functional check of the glider's trim lever operation was completed by the NTSB investigator-in-charge. The trim lever was placed in the full nose down position (takeoff position) and then secured by hand-tightening the wing nut, which is used to lock the lever in place. The control stick was then pulled aft, and the trim lever would release almost immediately. This procedure was repeated several times with the same result. An FAA inspector also performed a functional check of the trim lever operation with the same results.

According to the US sales representative for Schleicher gliders, the trim system in the glider was "not highly effective and should have been easy to override."

METEOROLOGICAL INFORMATION

At 1351, the weather observation facility at the Claremore Regional Airport, Claremore, Oklahoma (located 9 miles west of the accident site), reported the wind from 250 degrees at 11 knots gusting to 15 knots, visibility 10 statute miles, sky clear, temperature 73 degrees Fahrenheit, dew point 48 degrees Fahrenheit, and an altimeter setting of 29.94 inches of mercury.

A pilot, whose tow flight departed just prior to the accident, reported that the weather conditions were partly cloudy with a "reasonably" steady wind from about 240 degrees at approximately 9 knots, and the temperature was about 73 degrees Fahrenheit. The pilot further reported that he did not experience any turbulence or gusty wind conditions.

AERODROME INFORMATION

The Mid-America Industrial Airport is located 4 miles south of Pryor, at an elevation of 622 feet. The airport has one asphalt runway, 17/35, which is 5,000 feet long and 75 feet wide.

WRECKAGE IMPACT INFORMATION

The airplane impacted the 75-foot wide runway 16 feet 5 inches from the east edge. The initial impact point was located using a global positioning satellite (GPS) receiver at 36 degrees 13 minutes 13.4 seconds north latitude and 95 degrees 18 minutes 47.9 seconds west longitude. Examination of the accident site revealed that the airplane impacted the ground on a measured magnetic heading of 160 degrees and came to rest upright off the east side of the runway 174 feet from the initial ground scar on a measured magnetic heading of 155 degrees. The airplane's cockpit/cabin area was consumed by fire. Flight control continuity was confirmed from all flight control surfaces through the fuselage to their respective cockpit controls. All landing gear were found separated.

The tow hook was found partially separated from the tail, and the 187-foot tow rope was found 130 feet 8 inches northwest of the tail of the airplane. Examination of the tow rope revealed that the breakable link was broken. (The breakable link is part of a 6-foot adapter section of the tow rope that is attached to the glider end of the tow rope.) The pilot's emergency release rope was still attached to the tow hook and it was found laying on the ground next to the airplane.

The engine remained partially attached to the airframe. Engine crankshaft continuity and cylinder compression were obtained. Both magnetos and their wire harnesses were fire damaged, and all spark plug electrodes were light gray in color. The propeller remained attached to the crankshaft. One propeller blade had leading edge gouging and exhibited twisting and aft bending. The other blade had leading edge gouging and its tip was bent aft.

No damage was noted during an examination of the glider by the NTSB IIC. The 6-foot adapter section of the tow rope was not found during the on scene investigation; however, it was later found by a member of the soaring club.

MEDICAL AND PATHOLOGICAL INFORMATION

The Office of the Medical Examiner at Oklahoma City, Oklahoma, performed an autopsy of the tow airplane pilot. There was no evidence found of any preexisting disease that could have contributed to the accident.

The FAA Civil Aeromedical Institute toxicology report noted 47.6657(mg/dl, mg/hg) salicylate was detected in urine. Atenolol was detected in blood, liver, and urine. According to the FAA Southwest Regional Flight Surgeon, atenolol is an anti-hypertensive medication, and it was reported on the airman's last physical examination.

ADDITIONAL INFORMATION

The wreckage of the Cessna 150 was released to the owner on May 27, 2001.

NTSB Probable Cause

the failure of the glider pilot to maintain aircraft control and his delay in releasing the towrope. A contributing factor was the glider's worn elevator trim friction, which resulted in its disengagement.