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Last updated: 5 December 2020
Statuts:Enquête Officielle
Date:samedi 5 août 2017
Heure:20:00
Type/Sous-type:Silhouette image of generic P2 model; specific model in this crash may look slightly different
Lockheed P2V-5F Neptune
Operator:Neptune Aviation Services
On behalf of:U.S. Forest Service
Immatriculation: N410NA
Numéro de série: 526-5363
Année de Fabrication: 1954
Heures de vol:8486
Moteurs: 2 Wright R-3350
Equipage:victimes: 0 / à bord: 3
Passagers:victimes: 0 / à bord: 0
Total:victimes: 0 / à bord: 3
Dégats de l'appareil: Substantiels
Lieu de l'accident:près de Pocatello Airport, ID (PIH) (   Etats-Unis d'Amérique)
Phase de vol: En montée initiale (ICL)
Nature:Incendie
Aéroport de départ:Pocatello Airport, ID (PIH/KPIH), Etats-Unis d'Amérique
Aéroport de destination:Pocatello Airport, ID (PIH/KPIH), Etats-Unis d'Amérique
Détails:
A Lockheed P2V-5 airplane, N410NA, was substantially damaged shortly after departure from Pocatello Regional Airport (PIH), Idaho, USA. The two pilots and mechanic were not injured. The airplane flew under contract with the United States Forest Service. Visual meteorological conditions prevailed, and a flight plan was not 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 the airplane's climb, the flight crew increased the airplane's nose up pitch by a few more degrees and the PIC subsequently responded with increasing nose down pressure. However, the down pressure control input required additional force, so the PIC used trim inputs to reduce the pressure. Moments later he 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 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.

As the PIC had previously demonstrated the ability to land without making any adjustments to power or pitch in flight training, he elected to configure the airplane for an approach without trim or elevator control. The flight crew 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, and the 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 flight 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 one of the varicam actuator's outboard drive stop bolts had backed out of the drive coupling, and that the two bolts had not been safety wired. The airplane did not sustain any damage during the airplane's landing.

Probable Cause:

PROBABLE CAUSE: "Maintenance personnel's failure to secure hardware, which resulted in an uncommanded upward deflection of the left elevator and aft movement of the control yoke and inhibited the flight crew from adjusting the airplane's pitch attitude in flight. Contributing to the accident was the lack of maintenance oversight, which should have identified the unsecured hardware before flight."

Accident investigation:
cover
Investigating agency: NTSB
Status: Investigation completed
Duration: 1 year and 10 months
Accident number: WPR17LA180
Download report: Final report

Sources:
» NTSB


Photos

photo of Lockheed-P2V-5F-Neptune-N410NA
accident date: 05-08-2017
type: Lockheed P2V-5F Neptune
registration: N410NA
photo of Lockheed-P2V-5F-Neptune-N410NA
accident date: 05-08-2017
type: Lockheed P2V-5F Neptune
registration: N410NA
 

Plan

Les informations ci-dessus ne représentent pas l'opinion de la 'Flight Safety Foundation' ou de 'Aviation Safety Network' sur les causes de l'accident. Ces informations prélimimaires sont basées sur les faits tel qu'ils sont connus à ce jour.
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