NTSB Factual Report

On October 25, 2016, about 1415 central daylight time, a Boeing A75N1 (PT17) single-engine vintage biplane, N48182, impacted terrain during a takeoff from McCampbell-Porter Airport (TFP), Ingleside, Texas. The airline transport pilot was not injured, and the airplane was substantially damaged. The airplane was registered to American Airpower Heritage Flying Museum and operated by Commemorative Air Force under the provisions of Title 14 Code of Federal Regulations Part 91. Day visual meteorological conditions prevailed for the personal flight that departed Mustang Beach Airport (RAS), Port Aransas, Texas, about 1300, and was operating in the traffic pattern at TFP when the accident occurred.

The pilot reported that he was practicing takeoffs and landings on runway 13 (5,000 ft by 75 ft, asphalt) with a surface wind slightly left of the runway heading between 5-7 knots. He made two uneventful stop-and-go landings before the accident takeoff. The third takeoff was uneventful until the tail became airborne, around 45 miles per hour (mph), and the airplane began to veer to the right. He responded by reducing right rudder input and applying back stick pressure to become airborne at 65 mph. The pilot reported that upon liftoff, the airplane yawed right as if it had weathervaned into the wind (despite the wind being left of centerline). In response, he reduced airplane pitch to increase airspeed, but the airplane continued to yaw right and it subsequently entered an uncommanded right roll with a slight nose-up pitch attitude. The pilot reported that he was unable to regain control with full left aileron and left rudder inputs. The airplane impacted terrain, off the right side of the runway, in a right wing low attitude. The pilot estimated that the airplane had reached a right bank angle of about 90° when the right wing impacted the ground. The airplane subsequently nosed-over and came to rest inverted. The airplane sustained substantial damage to the upper wing and empennage during the impact sequence. The pilot reported having flown 10 hours in the accident airplane make/model.

The pilot postulated that an inflight failure of the right horizontal stabilizer resulted in the uncontrollable right roll during takeoff. A postaccident examination confirmed flight control continuity to all primary flight controls; however, the right horizontal stabilizer and vertical stabilizer were significantly damaged during the accident. The airplane had a braced tail structure, with the bracing wire connecting the horizontal stabilizer forward spar tubes to the vertical stabilizer leading edge. The fractured right horizontal stabilizer's forward and aft spar tubes, right horizontal stabilizer bracing wire with fractured shackle fitting and bolt, and the fractured vertical stabilizer spar tube were sent to the National Transportation Safety Board (NTSB) Materials Laboratory for additional examination. The NTSB laboratory examination determined that all observed separations were consistent with an overstress failure due to impact-related damage; no materials anomalies were identified with any of the submitted components. Additional laboratory documentation for the submitted components is included in the docket materials associated with the investigation.

The operator provided a copy of their training manual used for the Boeing A75N1 (PT17) airplane. The training manual lists the airplane's power-off and power-on aerodynamic stall speeds at maximum gross weight as 55 mph and 51 mph, respectively. The training manual states that after liftoff a pilot is to initially keep the airplane pitch low to increase airspeed to a recommended climb speed of 75-80 mph to allow for adequate engine cooling and forward visibility. The training manual notes that the airplane is known to develop a left swerve during takeoff due to gyroscopic precession. The gyroscopic precession is proportional to the rate of pitch change during the airplane's transition from a three-point to a tail-up pitch attitude. The training manual notes that if a pilot allows the tail to rise too rapidly during takeoff it can result in a rapid left swerve; however, if the tail is raised slow enough, a normal right rudder input may result in a right yaw. The right yaw can be corrected for by raising the tail more rapidly, which allows gyroscopic precession to compensate for the unintended right yaw. The training manual also cautions that the use of aileron, when a rudder input is recommended, during a swerve will result in pilot-induced adverse yaw. Adverse yaw is undesirable tendency for an airplane to yaw in the opposite direction of a roll input. The training manual notes that if the use of aileron control is applied during a swerve, it should be made in the same direction of the swerve. The training manual notes that pilot should quickly detect any small deviations during a takeoff, then immediately respond with small, precise, and aggressive flight control inputs. A copy of the training manual is included in the docket materials associated with the investigation.

At 1415, the TFP automated surface observing system reported: wind 070° at 11 knots, a surface visibility of 10 miles, a clear sky, temperature 31° C, dew point 18° C, and an altimeter setting of 30.10 inches of mercury.

NTSB Probable Cause

The pilot's failure to maintain proper yaw and roll control during takeoff, which resulted in excessive adverse yaw upon liftoff.