Accidents: February 2015

Preliminary Report: Learjet Destroyed in Suspected Illegal Flight

Learjet 35A, near San Fernando de Apure, Venezuela, Nov. 30, 2014–The jet was impounded upon landing at a remote strip after illegally entering Venezuelan airspace. The aircraft bears an N registration but local sources who recognized the aircraft claimed it was more likely a Brazilian airplane. Military personnel seized and destroyed the aircraft near San Fernando de Apure. Reports gave no details on the fate of the crew.

Preliminary Report: AStar Collides with Fire Bucket

Airbus Helicopters AS350B3, Pertica Bassa, Italy, Jan. 6, 2015–On a firefighting mission, the helicopter was returning to base when the bucket it was carrying contacted the tail rotor. The pilot was able to maintain control of the helicopter and safely executed an emergency landing on the front lawn of a home. The pilot was unhurt but the helicopter’s tail was substantially damaged.

Preliminary Report: Twin Otter Destroyed in Mexico Crash

De Havilland Canada DHC-6 Twin Otter 300, Tequesquitengo Airport, Mexico, Dec. 22, 2014–The right wing of the Mexican-registered Twin Otter collided with a number of shipping containers alongside the small airstrip, and the tail separated from the fuselage. The number of injuries aboard the aircraft was not reported.

Final Report: Cockpit Discipline and Mechanical Cited in Runway Excursion

Gulfstream GV-SP, Appleton (ATW), Wis., Feb. 14, 2011–As the jet approached Appleton following a maintenance test flight, the left hydraulic system failed. The aircraft was unable to stop before the end of 6,501-foot Runway 30 and incurred substantial damage after the left main landing gear collapsed. Neither pilot nor the single passenger was injured. The airplane, registered to and operated as a Part 91 maintenance flight by Gulfstream Aerospace, was on an IFR flight plan and flying in VFR conditions.  

After recording a number of relatively minor anomalies with the aircraft, the flight crew set up for an Rnav/GPS approach for a full stop at ATW, where the aircraft was based. As the airplane approached the virtual glideslope, the pilot flying called for landing gear down and the landing checklist. The gear extended normally. The pilot not flying completed the before-landing checklist to “include arming ground spoilers, warning inhibit, pumping up brakes/hydraulics/brake accumulator to 3,000 psi” except for “selecting full flaps,” which would be upon the pilot flying’s call. After the pilot not flying selected landing mode on the cabin pressure controller, an amber left side hydraulic quantity low crew alerting system (CAS) message illuminated; the airplane was inside the FAF approximately 5.8 nm from the end of the runway. The pilot flying selected the hydraulic synoptic page and noticed the hydraulic quantity dropping. He then called for full flaps but no movement was detected so the pilot not flying reselected flaps 20. Shortly after that an amber left hydraulic system fail CAS message appeared.

The pilot not flying ran the appropriate checklist but suggested a go-around. At the beginning of the checklist, there is a note that indicated, in part, “Select a runway that is at least 7,000 feet (2,133 m) long and 150 feet (45 m) wide.” According to the operator’s report, the pilot flying chose to land, a decision driven by the significant hydraulic leak on an airplane already configured for landing and at less than 1,000 feet agl. The pilot not flying continued the left hydraulic fail checklist and turned on the auxiliary pump at approximately 500 feet agl to comply with the manufacturer recommendation to verify the availability of the auxiliary system fluid. According to the operator’s report, both the pilot flying and the pilot not flying thought before landing that they had a good auxiliary hydraulic system with normal spoilers, brakes and nosewheel steering. The pilot flying had pulled the throttles to idle as the airplane touched down but indicated he “felt it took a long time to get the nose down.”

The pilot flying selected right thrust reverser but felt no resistance when he began began applying the brakes. He then reached for the emergency brakes, saw the 3,000 feet remaining sign and decided there was insufficient distance in which to stop. He attempted to go around by advancing power to the maximum continuous thrust setting. The pilot not flying felt there was not enough runway remaining to get airborne and saw the airspeed stable at 100 knots with no acceleration. He pulled the throttles back with approximately 1,000 feet of runway remaining, reporting later that he made this decision to avoid the worst case of a runway overrun at an even higher speed just as the engines were spooling up. The pilot flying again deployed the right thrust reverser and began steering to the right to avoid obstacles. The aircraft exited the runway at approximately 95 kias, veered right and came to a stop after the left main landing gear collapsed.

Post-accident examination of the airplane revealed that the nose landing gear swivel assembly, which had passed an acceptance test procedure before being installed, had seized, and the hydraulic fluid had leaked from a fracture on its inboard connecting tube. The swivel assembly had galling scars on the outside diameter of the spool and the inside diameter of the housing. Both the spool and housing were made from similar aluminum alloys that have a propensity to gall and adhere to each other when rubbed together. Further examination showed the nose landing gear hydraulic system did not have a required volumetric hydraulic fuse designed to minimize the loss of hydraulic fluid in the event of a line break downstream of such a device.

The NTSB determined the probable cause to be the pilot flying’s decision to land on a shorter-than-recommended runway with a known left hydraulic system failure rather than go around as suggested by the pilot-not-flying. The Board also cited the flying pilot’s failure to apply emergency brakes immediately after the primary brakes were found to be inoperative, as well as the late go-around attempt with insufficient runway remaining.

Contributing to the accident was the nose landing gear swivel assembly failure; the lack of a hydraulic fuse before this critical failure point; and the design of the swivel, which two similar alloys inclined to bind when rubbed together. Finally, the NTSB cited the lack of a disciplined cockpit environment as a contributing factor.

Final Report: Pilot Failed to Maintain Rotor Clearance

MD500E, near Elverta, Calif., Feb. 4, 2011–The helicopter was being operated under Part 133 by Wilson Construction on a power line installation mission when the rotor became entangled with a sock line rope used to string new lines. The main rotor blades made contact with the sock line rope, which then wrapped around the mast as the blades pulled it in.

The pilot lost control of the helicopter as it began an uncontrolled descent to the ground, coming to rest upright about 10 feet south of the power line structure. The lineman who had been riding on the skid was lying on the ground but still attached to the helicopter by her fall restraint and positioning belt. The pilot extricated himself safely from the helicopter. Both reported only minor injuries.

The helicopter operator reported the aircraft was working on a project to construct 30 miles of high-power electrical lines oriented north to south. Because it is not possible to pull the conductor wire through bundled travelers unless the sock line is actually in contact with a roller, construction crews install a hold down, a temporary block they secure to a ground anchor. They adjust the anchor rope on the sock line to maintain the proper tension.

A lineman was positioned on the skid of the helicopter to install a hold down at the power line structure as the pilot positioned the helicopter about 30 to 50 feet south of the structure. The pilot believed he was properly positioned near the sock line so that they could perform the task safely. The lineman on the skid placed the larger of the two hold-down ropes over the sock line and allowed it to fall. The lineman allowed the hold-down block to hang by the large rope just below, but the large rope tangled as it fell to the ground. The lineman on the ground tried unsuccessfully to clear the tangle. The lineman on the skid, with one hand on the hold down, was preparing to release the second smaller rope downward on the other side of the sock line when the rotor blades first made contact.

The NTSB determined the probable cause to be the pilot’s failure to maintain rotor-blade clearance from an installation rope while maneuvering to install power lines.