Pilot Debrief

DEHAVILLAND DHC-3 near Yakutat, AK — 2022-05-24

Final reportANC22LA035
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Date
2022-05-24
Location
Yakutat, AK, USA
Airport
3AK
Aircraft
DEHAVILLAND DHC-3
Registration
N703TH
Category
Airplane
Highest injury
Serious
Fatalities
0
Phase of flight
Approach

Probable cause

The pilot’s failure to determine the actual weight and balance of the airplane before departure, which resulted in the airplane being operated outside of the aft center of gravity limits and the subsequent aerodynamic stall on final approach. Contributing to the accident was the Federal Aviation Administration's failure to require weight and balance documentation for 14 Code of Federal Regulations Part 135 single-engine operations.

Contributing factors

Contributing to the accident was the Federal Aviation Administration's failure to require weight and balance documentation for 14 Code of Federal Regulations Part 135 single-engine operations.

NTSB narrative

The purpose of the flight was to transport three passengers and cargo. The pilot reported that, during takeoff, the airplane’s tail came up slightly lowered to the runway when he attempted to raise the tail by applying forward elevator. He stated that he thought this was unusual and attributed it to an aft-loaded airplane. He applied additional nose-down trim and departed without incident. While en route, the tail of the airplane seemed to move up and down, which the pilot attributed to turbulence. Upon arrival at his destination, the pilot entered a left downwind, reduced the power and extended the flaps to 10° abeam the end of the runway. He turned onto the base leg about ½ mile from the approach end of the runway and slowed the airplane to 80 mph. Turning final, he noticed the airplane seemed to pitch up, so he applied full nose-down pitch trim and extended the flaps an additional 10°. On short final he applied full flaps, and the airplane abruptly pitched up to about a 45° angle. He stated that he applied full nose-down elevator, verified the pitch trim, and reduced the power to idle. When the airplane was about 300 ft above ground level, the airplane stalled, the left wing dropped slightly, and the airplane entered about a 45° nose-down dive. After allowing the airplane to gain airspeed, the pilot applied full back elevator. The airplane impacted forested terrain near the approach end of runway 23 at an elevation of about 18 ft. A postaccident examination of the airframe and engine revealed no evidence of preaccident mechanical malfunctions or failures that would have precluded normal operation. Elevator and rudder control continuity was confirmed from the cockpit to the respective control surfaces. The airplane's estimated gross weight at the time of the accident was about 7,796 lbs and the airplane's estimated center of gravity was about 3.2 to 5.6 inches beyond the approved aft limit. Maximum gross weight for the airplane is 8,000 lbs. The operator did not comply with their operations specifications and the federal regulations that required them to follow the weight and balance control procedures outlined in the aircraft weight and balance section of the pilot operating handbook and the requirement to maintain an aisle between the crew and passenger compartments. The low speed, left roll, and pitch down of the airplane is consistent with an aerodynamic stall. The additional nose down trim at takeoff, the instability of the airplane during cruise flight, the full nose down trim during the approach and rapid pitch up after the application of full flaps are all consistent with an aft center of gravity (CG) condition of sufficient magnitude that the elevator pitch down authority was insufficient to overcome the pitching moment generated by the loading and aircraft configuration. The full down (or landing) flaps exacerbated the nose-up pitching moment due to the increased downwash on the tail and aft shift of the center of pressure. For each flight in multiengine operations, Title 14 Code of Federal Regulations (CFR) 135.63(c) requires the preparation of a load manifest that includes, among other items the number of passengers, total weight of the loaded aircraft, the maximum allowable takeoff weight, and the center of gravity location of the loaded aircraft; one copy of the load manifest should be carried in the airplane, and the operator is required to keep the records for at least 30 days. Single-engine operations, such as the accident flight, are excluded from this requirement. Had the pilot been required to prepare a load manifest that included the number of passengers, total weight of the loaded aircraft, the maximum allowable takeoff weight, and the center of gravity location of the loaded aircraft, he may have been more aware of the airplane’s out-of-center-of-gravity condition. The National Transportation Safety Board (NTSB) previously addressed the exclusion of single-engine operations from the Part 135 weight and balance requirements with the issuance of Safety Recommendations A-89-135, A-99-61, and A-15-29, which asked the Federal Aviation Administration (FAA) to amend the record-keeping requirements of 14 CFR 135.63(c) to apply to single-engine as well as multiengine aircraft. The FAA did not take the recommended action, and the NTSB classified Safety Recommendations A-89-135, A-99-61, and A-15-29 "Closed—Unacceptable Action" in 1990, 2014, and 2021, respectively.

Analysis

Primary failure mode
Human factors
First missed decision gate
Pilot failed to ensure proper weight and balance before takeoff.

NTSB coding

Evidence available

  • FDR / data
  • Photos
  • 13 docket documents
View NTSB final reportView NTSB docket

Docket documents13

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