NTSB Factual Report

On June 26, 2010, about 1300 mountain daylight time, a Lockheed P2V-5 airplane, N1386C, was substantially damaged during a landing roll overrun at the Rocky Mountain Metropolitan Airport (BJC), in Broomfield, Colorado. The pilot and co-pilot were not injured. The airplane was registered to Neptune Aviation Services Inc., of Missoula, Montana, and operated by the United States Department of Agrigulture (USDA), Forestry Service, under an exclusive public-use firefighting contract. Visual meteorological conditions prevailed and a company flight plan was filed for the fire suppression flight. The local flight originated from BJC at 1150.

According to the pilot, following a “normal” retardant drop, the main hydraulic system failed. The airplane was configured for landing via emergency hydraulic pressure and an emergency declared. The pilot continued, that the landing was routine; however, when he attempted to stop the airplane using the emergency system brakes there was no response. The airplane went through a fence, down an embankment, and came to rest nose down on a city street. The pilot and co-pilot were able to exit unassisted through the airplane’s upper hatches.

The airplane had landed on runway 29R. The pilot exited the runway via taxiway A13. The airplane proceeded across taxiway A, through a grassy area between taxiway A and the tanker base ramp, and across the northwest portion of the tanker base ramp. The airplane then went off the prepared surface through the airport perimeter fence where it went down the embankment and came to rest on the north side of Network Parkway. Pieces of the perimeter fence were found in the parking lot of an adjacent office complex. One piece of the fence went through an office window.

A postaccident examination of the airplane showed the nose gear broken aft and upward crushing and bending of bulkheads and walls in the nosewheel well and underside of the nose structure. The Plexiglas nose dome window was broken out. One of the four propeller blades on the right engine was bent aft. All four of the propeller blades on the left engine were broken off near mid-span. There was also fire damage observed to the outer side of the left engine nacelle just behind the ring cowling.

Further examination of the airplane’s hydraulic system showed a rupture in the line from the main hydraulic and tank system. No other systems anomalies were found.

The USDA Forest Service reported that while returning to the airport, the pilot briefed the co-pilot about the proper procedures to lower the gear. The co-pilot referred to the emergency procedures checklist and went to the spar area to operate the emergency gear extension systems. The nose gear down select was activated and the gear dropped. The co-pilot then pinned the gear in the down position and moved the emergency nose gear extension system selector to the “bypass” position, which cut off emergency system hydraulic system pressure to the elevator flight control and emergency brakes. The airplane flight manual specifies the selector be placed back to the “normal” position. The co-pilot then made an unsuccessful try to lower the main gear by releasing the up-lock lever, but on the second try the gear came down. The pilot noticed all three landing gear indicators showed the gear was safely down and locked and reported this to the tower.

The pilot briefed the tower that they would not have nose wheel steering but would try to take the high speed taxiway (A-13) off the runway near the tanker base. They received clearance to land and to make a right turn when able to exit the runway.

After touchdown, the airplane was slowed using reverse thrust on the propellers and steered using differential braking. A hydraulic accumulator supplies enough pressure to the brakes to allow for a few applications in the event of a loss of system pressure. The pilot felt he had adequate directional control and could make the right turn at A13 using the remaining emergency braking system to stop the airplane in the dirt prior to the tanker base ramp. The pilot made the turn off the runway and taxied toward the ramp. As they approached the end of the taxiway, the pilot applied the emergency brake with no result. He checked to see that he had the right lever and reapplied, again with no result. He then told the co-pilot they had no brakes and were going to wreck.

According to the airplane flight manual the procedure for hydraulic failure is to land and stop on the runway using the emergency brake and accumulator pressure. After stopping, the stiff-knee pins are to be installed and the airplane is to be towed to parking.

NTSB Probable Cause

The pilot’s failure to follow published emergency procedures by taxiing to the parking ramp with a known hydraulic system failure. Contributing to the accident was the co-pilot’s improper selection of the bypass position on the emergency nose gear extension system, which shut off emergency hydraulic system pressure to the brakes, and a ruptured hydraulic line, which resulted in a total loss of the main hydraulic system pressure.