History of Flight
On August 5, 2017, about 2000 mountain daylight time, a Lockheed P2V-5 airplane, registration N410NA, was substantially damaged shortly after departing from Pocatello Regional Airport (PIH), Pocatello, Idaho. The airline transport pilot, commercial pilot, and mechanic were not injured. The airplane was registered to and operated by Neptune Aviation Services, Inc., Missoula, Montana, as a public aircraft under contract with the United States Forest Service. Visual meteorological conditions prevailed, and no flight plan was filed for the local flight.
According to the pilot-in-command (PIC), the flight departed on its third mission to disperse fire retardant over a nearby wildfire. During climb, the flight crew increased nose-up pitch, and the PIC responded with nose-down pressure, which required additional force. He used trim inputs to reduce pressure. Moments later, he observed an uncommanded aft movement of the control yoke with a simultaneous increase in pitch attitude. He instructed the first officer (FO) to retract flaps while he re-trimmed the elevator, but they could not regain pitch control. The FO attempted to adjust his trim wheel and then re-trim using the emergency varicam, but the airplane continued to pitch up. The PIC then deployed 5° of flaps, which reduced elevator backpressure. He jettisoned the fire retardant over vacant farmland and asked the FO to declare an emergency with the tower controller while he entered a shallow left turn for Runway 21. During control inputs, he determined the elevator was bound, receiving little response.
The PIC elected to configure for an approach without trim or elevator control, as he had previously demonstrated such a landing in training. The crew flew a wide pattern, using wing flaps and engine power for pitch-up adjustments and coordinated elevator application for pitch-down. At about 500 feet above ground level, they deployed the remaining 5° of flaps to increase pitch attitude. Both pilots pulled hard on the yoke while the FO gently retarded throttles and the PIC trimmed the emergency varicam.
Aircraft Information
The airplane, manufactured in 1954, was registered to Neptune Aviation on December 16, 2010. It was powered by two outboard Westinghouse J34-WE-36A turbojet engines and two inboard Curtis Wright R-3350-32WA radial engines. The most recent 100-hour inspections were completed on July 10, 2017, at 8,420.2 total flight hours; the previous annual inspection was in October 2016. At the time of the incident, total flight time was 8,486.7 hours.
The airplane was equipped with a variable camber (varicam) horizontal stabilizer in place of an elevator trim tab, mounted on the trailing edge of the fixed stabilizer. Elevators are hinged to the trailing edge of the varicam and kept faired by a trim tab on the left elevator. The varicam trim is electrically controlled by switches on both yokes, with travel limits controlled by limit switches in the tail section. Hydraulic pressure from the main system rotates the varicam drive shaft to move the actuators and deflect the secondary control surface. The varicam actuators are secured to the drive shaft through universal joints at the outboard ends, comprising two bolts normally threaded and safety-wired to the drive coupling, plus two bolts with castellated nuts and cotter pins.
Postaccident Examination
Examination revealed damage to the varicam. Since this secondary control surface is directly connected to the elevators and provides a primary structural load path, the damage was classified as substantial. The varicam's left outboard drive stop and yoke showed only one bolt secured to the coupling; normally two bolts are threaded and safety-wired together. Photographs from Neptune's Director of Maintenance (DOM) showed the second bolt resting against the lower varicam skin with no safety wire in the bolt head. No safety wire was found in the cavity of the secondary control surface.
The DOM reported that absence of one drive coupling bolt would hinder torque capabilities, allowing one side of the varicam to move and the other to remain stationary or turn incrementally, twisting and deforming the varicam. Since the elevator is hinged to the varicam, the twist can force one elevator into an upward deflected position. The left side of the varicam was deformed, and the left elevator was deflected upward.
Maintenance and Inspection
Neptune Aviation uses task cards distributed to mechanics. A task summary card dated July 27, 2016, noted worn universal joints on the left varicam. A mechanic recorded removal and replacement of three sets of universal joints on the left varicam inboard and outboard sides, per NAVAIR 01-75EDA-2-3, with no defects noted. The entry was stamped "M77," assigned to a mechanic who left the company a few days later for unrelated reasons. Task card 10-3, line "j" of the annual inspection requires installation of drive shafts, u-joints, and drive shaft stop assembly secured with lockwire; this was verified with the stamp. Another task card indicated card 10-3 was completed on July 28, 2016, during the annual inspection.
The DOM stated the varicam work was performed at Neptune's Alamogordo, New Mexico facility, which reopened in 2014. The facility employs one daytime shift of mechanics working 0700-1730, four days per week. At the time of the 2016 annual inspection, the facility had 12 full-time employees: a shop manager, lead mechanic, quality assurance mechanic, six line mechanics (all A&P certified), and three parts purchasing staff.
Neptune's Standard Operating Procedure (SOP) includes criteria to designate certain task cards as Required Inspection Items (RII). The lead mechanic annotates "RII required" on task cards; then a quality assurance (QA) inspector must inspect the work. Under company RII guidance, ATA 27, item 10 states: "Varicam System Components – Install/Rig/Adjust (P2V)." The right column states to check proper installation, torque, security, and safety. An RII notation was not placed on sub-task card 163379-244, which required lockwire for the drive stop bolts. Although the varicam qualifies as an RII, the oversight did not register with the mechanic or lead mechanic. An audit of the annual inspection package later discovered seven task cards missing mandatory RII notations.
Personnel and Procedures
The lead mechanic was responsible for generating and assigning task cards. The QA inspector, who had been with Neptune since 2010 and primary QA since November 2015, stated the lead mechanic was preoccupied with paperwork and spent most of his time at his desk rather than performing inspections. When asked about the RII process, the QA mechanic said that even if RII is not documented, the paper goes to the lead and then QA stamps it as approved despite company requirements to verify.
The mechanic who performed the safety wiring departed the company on August 2, 2016, a few days after servicing the varicam, having given two weeks' notice due to family issues. The lead mechanic was later terminated for poor attitude and falsifying completed work, including inscribing another mechanic's name on a task card when that mechanic was absent. He had also created a stressful environment by reviling mechanics to expedite work. The shop manager reported that the lead mechanic worked well initially but later attempted to create a barrier between the New Mexico facility and the company's Missoula headquarters, and received complaints about his lack of involvement.
The company does not offer recurrent training on internal procedures for quality assurance, lead mechanics, or line mechanics, though it maintains a two-year recurrent requirement for RII training. Training for P2V mechanics consists of a one-time course with hands-on and classroom elements, plus recurrent training when necessary.