Preliminary Report: Four Die in Kenyan Freighter Crash
Fokker 50, Nairobi, Kenya, July 2, 2014–A Fokker 50 freighter headed to Mogadishu, Somalia, crashed shortly after takeoff at 4 a.m. from Runway 06 at Nairobi-Jomo Kenyatta Airport. All four crewmembers on board were killed in the accident and the aircraft was destroyed when it came down in a residential area a mile northeast of the airport.
Preliminary Report: Learjet and Typhoon Collide in Mid Air
Learjet 35A, Elpe, Germany, June 23, 2014–The two occupants of a civilian Learjet died when their aircraft collided in midair with a German Air Force Typhoon fighter. The Learjet and two Typhoons were taking part in an interception exercise at the time of the collision. The Learjet crashed, but the Typhoon pilot was able to make an emergency landing at Nörvenich Air Base.
Preliminary Report: LongRanger on Rig Run Crashes In Gulf of Mexico
Bell 206L-4, South Tim Bailier 317 platform, Gulf of Mexico, June 11, 2014–The helicopter was flying a straight-in approach to the oil rig when it made between eight and 10 clockwise spins, before going silent and falling into the water, according to a witness. The helicopter sank in 380 feet of water but was recovered.
Examinations showed extensive damage to the cabin, and the tailboom had separated from the cabin section of the fuselage. One of the main rotor blades, which had separated about four feet from the mast, was not recovered. The landing skids, cabin door and floor were not recovered. The commercial pilot and passenger lost their lives. VMC prevailed and company flight following was in effect at the time of the accident.
The helicopter was registered to Coy Leasing and operated by Westwind Helicopters under Part 135.
Preliminary Report: Helicopter Substantially Damaged in Hard Landing
MD500E, Mesa, Ariz., June 8, 2014–The helicopter, registered to and operated by the Mesa Police Department, landed hard at about 12:56 a.m. following a loss of engine power in the cruise. Neither the pilot nor the tactical flight officer aboard was injured, but the helicopter was substantially damaged. The nighttime VFR flight was a routine patrol.
About 1.4 hours into the flight, the pilot performed a series of flight checks in the vicinity of Phoenix-Mesa Gateway Airport. A short time later, while traveling at 60 to 70 knots about 700 feet agl, the pilot heard an uncharacteristic change in the engine note accompanied by a decrease in engine speed. As the pilot tried to diagnose the problem, a series of caution warning lights illuminated, followed by the engine-out tone.
The pilot immediately entered an autorotation, aiming for a tree-lined field. The helicopter cleared the trees, and before initiating the flare (but late in the autorotation) the pilot turned on the landing light and touched down level on the skids. The main rotor blades subsequently struck and severed the tailboom just aft of the tail fairing.
Preliminary Report: Meridian Accident at Westchester Co.
Piper PA-46-500TP Meridian, White Plains, N.Y., June 13, 2014–The private instrument-rated pilot and sole occupant of the Meridian was killed when the aircraft collided with trees and terrain shortly after it took off at 8:08 a.m. from White Plains Airport (HPN), N.Y. The Part 91 turboprop single was on an instrument flight plan at the time of the accident, although ATC later said the pilot never contacted the New York departure controller.
Radar sweeps beginning at the midpoint of the 6,500-foot runway captured the aircraft at five positions, all of them over airport property. Each of the first three sweeps showed the aircraft at 500 feet msl, approximately 60 feet agl. The final two sweeps showed the aircraft in a shallow right turn and were at 600 and 700 feet msl before radar contact was lost. HPN weather was reported as overcast ceiling at 200 feet and quarter-mile visibility in fog. The wind was from the east at six knots, with temperature and dew point of 17 degrees C.
One witness said he heard the Meridian’s engine before he saw the airplane. He added that the aircraft’s wings were level when the outboard section of the left wing struck a tree, the inboard section of the left wing struck a second tree and the airplane broke apart in a large cloud of blue “smoke” that smelled like “diesel” fuel. The fuselage came to rest on its left side against a tree, 280 feet down the wreckage path. The instrument panel and cockpit were destroyed by impact. The cabin and empennage were largely intact.
Examination of the accident site revealed that all major components of the airplane were accounted for and there was no evidence of an in-flight or post-impact fire on any of the airframe components. The FBO at HPN reportedly filled the airplane’s tanks the day before the flight with 60 gallons of jet-A.
Flight control continuity was traced through multiple breaks in the control cables and bell cranks to the relevant flight controls, and each separation of the cables exhibited signatures consistent with tensile overload. Control continuity was confirmed from the cockpit to the rudder and elevator.
The engine and propeller were both about 290 feet down the wreckage path, and separated by approximately 20 feet. All four propeller blades exhibited similar twisting, bending, leading- and trailing-edge gouging and chord-wise scratching. One propeller blade was fractured near its root and on its outboard tip, but the associated pieces were located at the accident site. The engine was separated from the airplane and found upright. The accessory gearbox and inlet case were fractured at numerous locations. The accessory gearbox spur gears and fractured sections of the accessory gearbox were recovered at the site. An engine data acquisition unit and a tablet computer were recovered from the accident site and sent to the NTSB recorders laboratory for examination.
Final Report: Learjet Failed To Stop on Wet Runway
Learjet 25B Portland, Ore., Nov. 17, 2010–The crew of the Part 91-operated Learjet was unable to stop the aircraft on 6,600-foot-long Runway 30 at Portland because the pilot flying failed to touch down at the proper point, according to the NTSB. Contributing to the accident was a poorly performing anti-skid system that allowed the tires to encounter reverted rubber hydroplaning. Additionally, the company-developed quick-reference landing distance chart did not provide tailwind correction factors, a shortcoming highlighted by an eight-knot tailwind component.
The crew flew a VOR/DME-C approach that included an oblique course approximately 40 degrees to the Runway 30 centerline under wind conditions that produced the eight-knot tailwind component. The runway was still wet from moderate to heavy rain during the preceding hour. Despite the tailwind, the captain elected to land on Runway 30 rather than circle to land. The crew said that the airplane was at the prescribed airspeed (Vref) for its weight with full flaps extended and that it touched down just beyond the touchdown zone. The aircraft’s optional thrust reversers were not operational. The captain extended the wing spoilers immediately after touchdown, tested the brakes and noted normal brake pedal pressure. However, during rollout, he noted a lack of deceleration and applied more brake pressure, with no discernible deceleration. The captain said there was insufficient runway for a safe go-around. He did not activate the emergency brakes (which would have bypassed the anti-skid system) because he thought there was insufficient time and because he was preoccupied with maintaining control of the airplane. Both pilots applied brake pressure, but with the airplane about 2,000 feet from the runway’s end, it was still traveling at about 100 knots.
As the airplane rolled off the departure end of the wet runway, both pilots estimated it was traveling at between 85 and 90 knots. The aircraft continued 618 feet through a rain-soaked grassy runway safety area before encountering a drainage ditch that collapsed the nose gear. The main gear also partially sank into the wet ground. The crew said they saw no cockpit indications of an anti-skid system failure or malfunction. After the airplane came to a stop, however, they noticed the annunciator light associated with antiskid for the number-two wheel indicated a system failure. The other three annunciator lights (one for each wheel) were not illuminated.
During the approach, the first officer had completed the landing data card by using the company-developed quick-reference card that lacked tailwind correction factors. The Learjet’s aircraft flight manual, however, did contain tailwind correction factors. The first officer read the quick-reference data as indicating that 3,240 feet was required to stop on a dry runway in zero wind, with a wet correction factor raising the stopping distance to 4,538 feet. The Vref speed was listed as 127 knots for their landing weight of 11,000 pounds, and the first officer’s verbal and written statements noted that they crossed the runway threshold at 125 knots. During the investigation, however, Bombardier Learjet calculated the wet stopping distance with an eight-knot tailwind as 5,110 feet.
The touchdown zone for Runway 30 is 1,000 feet beyond the approach end. The crew estimated they touched down about 1,200 feet from the approach end, yielding a remaining runway length of 5,400 feet. Air traffic controllers who saw the landing said the airplane touched down at a taxiway intersection 1,881 feet from the approach end, which would leave about 4,520 feet of runway remaining in which to stop the airplane. The controllers saw water spraying off the main landing gear just after the airplane touched down.
Post-accident testing indicated the brake system, including brake wear, was within limits, with no anomalies, and investigators noted no evidence of tire failure. When the anti-skid was removed and functionally tested, the control box and the left and right control valves tested within specifications. The four wheel-speed sensors also met the electrical resistance specification. The output voltages on three sensors exceeded the minimum but the fourth was frozen and could not be rotated or tested.
The NTSB concluded that the airplane likely touched down on the water-contaminated runway beyond the touchdown zone, leaving about 600 feet less remaining runway than the performance charts indicated the airplane required under wet conditions. Since reverted rubber hydroplaning typically follows an encounter with dynamic hydroplaning, the reverted rubber signatures on the number-two tire indicate that the airplane encountered dynamic hydroplaning shortly after touchdown and the left main gear wheel-speed sensor anomalies allowed the left tires to progress to reverted rubber hydroplaning. This, along with post-accident testing, indicated to the NTSB that the anti-skid system was not performing optimally and, in concert with the hydroplaning conditions, contributed significantly to the lack of deceleration during the braking attempts.