Monday, August 7, 2017

Lockheed P2V-5F Neptune, N410NA, Neptune Aviation Services Inc: Accident occurred August 05, 2017 at Pocatello Regional Airport (KPIH), Bannock County, Idaho

The National Transportation Safety Board did not travel to the scene of this accident.

Additional Participating Entities:
Federal Aviation Administration / Flight Standards District Office; Helena, Montana
Robinson Helicopter Company; Torrance, California

Aviation Accident Preliminary Report - National Transportation Safety Board:

Neptune Aviation Services Inc:

NTSB Identification: WPR17LA180

14 CFR Part 137: Agricultural
Accident occurred Saturday, August 05, 2017 in Pocatello, ID
Aircraft: LOCKHEED P2V 5F, registration: N410NA
Injuries: 3 Uninjured.

This is preliminary information, subject to change, and may contain errors. Any errors in this report will be corrected when the final report has been completed. NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

On August 5, 2017, about 2000 mountain daylight time, a Lockheed P2V-5, N410NA, was substantially damaged shortly after a departure from Pocatello Regional Airport (PIH), Pocatello, Idaho. The airline transport pilot, commercial pilot and passenger were not injured. The airplane was registered to and operated by Neptune Aviation Services, Inc. under contract with the United States Forest Service to provide aerial application services. Visual meteorological conditions prevailed and a flight plan was not filed for the local flight, which was conducted under the provisions of 14 Code of Federal Regulations Part 137. 

According to the pilot-in-command (PIC), the flight departed on its third mission to disperse fire retardant over a nearby wildfire. During the airplane's climb, the PIC observed an uncommanded aft movement of the control yoke with a simultaneous increase in the airplane's pitch attitude. He instructed the first officer (FO) to retract the flaps while he re-trimmed the elevator, but they were not able to regain pitch control. The airplane's varicam indicator showed a few degrees of nose down trim and did not change for the remainder of the flight. The FO attempted to adjust his trim wheel and then re-trim the airplane using the emergency varicam, but the airplane continued to maintain a pitch up attitude. He then deployed 5° of flaps at the PIC's instruction, which reduced the elevator backpressure. The PIC subsequently jettisoned the load of fire retardant over vacant farm land and then asked the FO to declare an emergency with the tower controller while the PIC entered a shallow left turn to intercept the downwind leg for Runway 21. As he made his control inputs he determined that the elevator was bound as he received little response from the elevator control. 

The PIC had previously demonstrated approaches to land without making any adjustments to power or pitch, so he configured the airplane for an approach without trim or elevator control. They flew a wide traffic pattern and made small adjustments to compensate for altitude. During the final approach leg, the PIC used a combination of wing flaps and engine power for pitch up adjustments, crew coordinated application of elevator for trimmed pitch, and turns to make their pitch down adjustments. As the airplane reached about 500 feet above ground level, the crew deployed the airplane's remaining 5° of flaps to increase the pitch attitude. Both the PIC and FO pulled hard on the yoke while the FO gently retarded the throttles and the PIC trimmed the emergency varicam. 

Postaccident examination of the airplane revealed damage to the varicam. As this secondary control surface is directly connected to the elevators and provides a primary structural load path for all elevator loads, the damage was classified as substantial. Further examination of the varicam showed that the varicam actuator's outboard locating bolt had backed out of the drive coupling. The bolt head had not been safety wired.

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