NTSB Factual Report

HISTORY OF FLIGHT

On April 21, 1998, at 1550 central daylight time, a Cessna 150F airplane, N8720G, was destroyed upon impact with terrain following a loss of control during initial climb after takeoff from the Hatbox Airport near Muskogee, Oklahoma. The flight instructor and the private pilot receiving instruction were fatally injured. The airplane was owned and operated by Grassroots Aviation Inc., of Cookson , Oklahoma, under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the local instructional flight for which a flight plan was not filed. The flight departed from the Davis Airport, also in Muskogee, Oklahoma, at approximately 1535.

According to personnel at the Davis Airport, the flight instructor arrived at Davis Airport from Goodson at approximately 1500 to pick up the private pilot for his second period of flight instruction. The 74 year old pilot receiving instruction had been inactive since 1973 and needed proficiency training prior to joining the local unit of the Civil Air Patrol.

The airplane was observed by a witness to be performing touch and go landings on runway 35 at the Hatbox Airport. While on the initial takeoff climb portion of the third takeoff, the witness observed the airplane bank to the left as the nose dropped towards the ground. The airplane impacted on the airfield, in the infield grass area between the approach ends of runways 11 and 17.

PERSONNEL INFORMATION

The flight instructor has been flying since October 1977, when she first obtained a student pilot certificate. She was issued a commercial pilot certificate on June 14, 1981. She became a certificated flight instructor on October 30, 1981. She was rated in single and multiengine land airplanes and held an instrument rating.

Her last second class FAA medical certificate was issued on June 16, 1997. As of April 2, 1998, the day of the last entry in her logbook, the flight instructor had accumulated a total of 5,273 hours of flight experience, with approximately 195 hours in the preceding 6 months. Her last biennial flight review (BFR) was completed on August 15, 1997.

The flight instructor was recently awarded a Master Flight Instructor Award from a national flight instructor's association. She had been active in the American Association of Airport Executives, the International Women Pilots Association, and the Oklahoma Airport Operators Association, over which she once presided. In 1991, she completed an around the world flight in a general aviation airplane.

The private pilot receiving flight instruction, who was occupying the left seat of the airplane, was issued his private pilot certificate on April 16, 1969. He held a current third class medical certificate issued July 22, 1997. At the time of his last medical examination, the pilot reported having accumulated a total of 2,000 flight hours, of which 10 hours were accumulated in the preceding 6 months. A friend of the pilot stated that the pilot was a retired postal worker who had been inactive from flying since 1973. According to the friend, most of the pilot's previous flight experience was gained in Piper tailwheel equipped airplanes.

AIRCRAFT INFORMATION

The 1966 model airplane, serial number 150-62820, was purchased by the present owner on February 12, 1992. The airframe had accumulated a total of 5,260 hours since new. The last annual inspection was performed on August 1, 1997. The last 100 hour inspection was completed on February 6, 1998, just 36 hours prior to the accident.

The Continental O-200-A engine, serial number 62598-5-A, was reported to have been overhauled on April 15, 1998, at 590 tachometer hours. At the time of the accident, the engine had accumulated a total of 30 hours since its last major overhaul.

The maintenance records for the airplane were provided to the FAA inspector by the co-owner of the airplane for review. The inspector's review of the airframe and engine records did not reveal evidence of any anomalies or uncorrected maintenance defects. The inspector found the airframe to be in compliance with applicable airworthiness directives.

The airplane's fuel tanks were reported to have been topped off with 100LL aviation fuel prior to its departure from the Tenkiller Airpark, near Cookson, Oklahoma. Weight and balance calculations were made using figures provided by the operator and the FAA medical information. According to the maintenance records, the useful load for the airplane was established at 490.7 pounds on July 31, 1996. The airplane was calculated to be within weight and balance limits at the time of the accident.

A review of the 1966 owner's manual for the airplane revealed the following statement: "flap deflections of 30 and 40 degrees are not recommended at any time for take-off." In the paragraph describing procedures for a "go-around climb," the manual states: "In a balked landing (go-around) climb, the wing flaps setting should be reduced to 20 degrees immediately after full power is applied. Upon reaching a safe airspeed, the flaps should be slowly retracted to the full up position." Pertinent portions of the manual are enclosed.

METEOROLOGICAL INFORMATION

The nearest weather reporting station was located at the Davis Airport (MKO), located 5 miles south southeast (153 degrees) from the accident site. The recorded weather at 1553 reported clear skies with a visibility of 10 statute miles. The winds were reported from 350 degrees at 11 knots, gusting to 17 knots. The temperature was 21 degrees centigrade (69.8 F), with a dew point of 20 degrees centigrade (68 F). The altimeter setting was reported as 30.20 inches Hg.

AERODROME INFORMATION

The Hatbox Airport (HAX) is a WWII vintage uncontrolled airfield which is now surrounded by residences and a large sport complex. The airport, which is owned by the City of Muskogee, has been abandoned for over a year, but has remained open. A city official stated that because of its low density of traffic, the airport is occasionally used by local pilots for closed traffic pattern work. He added that runway 35 is normally used by local operators to practice short field takeoffs and landings.

WRECKAGE AND IMPACT INFORMATION

Examination of the wreckage site revealed that the airplane impacted the ground on a measured magnetic heading of 185 degrees. Physical evidence and ground signatures at the initial point of impact indicate that the airplane impacted the ground in a left turn, in a nose low attitude.

Particles of red lens, identified as the wing tip navigation light for the left wing, were found in the ground scar at the initial point of impact.

The leading edge of the right wing was found to be crushed aft along the full span of the wing. The outer portion of the left wing tip was damaged outboard of the landing light. All aircraft components were found within 50 feet of the resting place of the airplane.

The actuator for the electrically operated flap system was found in the fully extended position. The elevator trim was found in the 5 degrees "up" tab position. Flight control continuity was established to all the flight controls.

The engine mounts were destroyed by impact. The engine intake and exhaust systems sustained heavy impact damage. The carburetor and vacuum pump remained attached to the engine. The magnetos could not be examined at the accident site. The starter and generator remained attached to the accessory gear case.

The McCaulley 2-blade propeller remained attached to the propeller flange. None of the bolts attaching the propeller hub to the crankshaft were found to be stretched or distorted. Neither of the propeller blades exhibited any rotational marks or torsional twisting. The tips of both propeller blades were undamaged.

The propeller spinner, which was found partially attached to the propeller hub, sustained compression damage and did not exhibit signs of rotational scoring.

The fuel selector was found in the "on" position. Continuity was established to all engine controls. The throttle was found near the closed position. The mixture control was found in the full rich position and the carburetor heat control was found in the "cold" position. The throttle, mixture, and carburetor heat cables remained attached to the engine.

MEDICAL AND PATHOLOGICAL INFORMATION

Autopsies and toxicological tests were requested and performed on both occupants. The autopsies were performed by the Office of the Medical Examiner in Tulsa, Oklahoma, on April 21, 1998. Toxicological tests were negative on both pilots.

FIRE

A post-impact fire consumed the right wing, the cabin, and the empennage of the airplane. Both 13 gallon metal tanks were compromised during the accident sequence. No evidence or signs of pre-impact fire was found during the field portion of the investigation.

TEST AND RESEARCH

The engine was transported to the engine manufacturer's facility in Mobile, Alabama, for further examination and testing. A teardown examination of the engine was completed on July 23, 1998, under the supervision of a representative from the NTSB. The examination concluded that the "engine exhibited normal operational signatures throughout. All internal components appeared well lubricated. This engine did not exhibit any condition that would have caused an operational problem." See the enclosed report for details of the investigation.

ADDITIONAL DATA

The wreckage was released to the owner's representative upon completion of the investigation.

NTSB Probable Cause

The inadvertent stall as result of the pilot's failure to retract the flaps from the fully extended position prior to takeoff. Factors were the gusting winds and the pilot's failure to follow the before takeoff checklist.