Investigation Summary
The flight was an on-demand air taxi operation with a commercial pilot and three passengers. During the takeoff from runway 8, the pilot waived a wake turbulence delay for an Embraer 190 that had departed 2 minutes 30 seconds prior and rotated the aircraft. According to the pilot, the airplane reached approximately 100 feet above ground level but failed to accelerate or climb further, subsequently yawing to the left. The pilot reported that the left engine RPM was lower than the right, leading him to believe an engine had failed. However, the front-seat passenger, an aerospace engineer, noted that the engine sound remained constant and the pilot failed to correct the yaw, instead allowing the aircraft to turn perpendicular to the wind. Investigators found that the airspeed indicator displayed miles per hour (mph) in large outer numbers and knots in smaller inner numbers. The pilot's reported rotation speed of 85 knots (98 mph) was likely actually 85 mph (74 knots), which was well below the best rate-of-climb speed of 120 mph (102 knots). The aircraft, which lacked counter-rotating engines to offset yaw at low speeds, stalled as the pilot attempted a left turn to return to the airport while at a critically low airspeed and high angle of attack.
Final Conclusions
The National Transportation Safety Board determined the probable cause to be the pilot's failure to maintain adequate airspeed, properly correct for left yaw, and his exceedance of the airplane's critical angle of attack during initial climb, which resulted in an aerodynamic stall and subsequent uncontrolled descent into water. (Final Report, January 23, 2018).
Video Analysis
No video analysis linked for this case file yet.
Airframe & Maintenance
Crew Experience
Captain
Held Commercial Pilot and Flight Instructor certificates. Multi-engine experience was 200 hours. The pilot had flown approximately 220 hours in a Britten-Norman BN-2A-21 Islander in the six months prior to the accident and had completed training in the accident aircraft type only 9 days before the crash.
Systems & Failure Modes
Airspeed Indicator
The instrument featured dual scales where mph were prominent on the outer ring and knots were smaller on the inner ring; the pilot likely misread the scale, leading to a low-speed climb.
Engines
Two Lycoming IO-540-C4B5 250-horsepower engines; post-crash testing showed no evidence of pre-impact failure despite the pilot's report of power loss.
Propellers
Hartzell controllable pitch full-feathering propellers; both were found in the normal operating range and not feathered after the crash.
Interesting Facts
- 01The pilot had only 20 hours of experience in the Piper PA-23 make and model.
- 02The aircraft was approximately 350 lbs below its maximum gross takeoff weight at the time of the accident.
- 03Post-accident examination of both engines confirmed crankshaft, camshaft, and valve train continuity.
- 04The airspeed indicator displayed mph in large outer numbers and knots in smaller inner numbers.
- 05The aircraft was not equipped with counter-rotating engines, increasing yaw tendencies at low airspeeds.
- 06The pilot waived a wake turbulence delay for an Embraer 190 that had departed 2 minutes 30 seconds prior.
Location
NO VERIFIED COORDINATES · This position predates coordinate provenance tracking. Treat it as an approximate marker for the area, not the accident site. No map is shown, because a marker here would imply a precision the record does not have.
Reported location: San Juan, Puerto Rico