PRELIMINARY REPORTS
Bulkhead Hole Discovered after L-382G Depressurization Incident
Lockheed L-382G, Iliamna, Alaska, Feb. 12, 2016–The L-382G, a stretched, commercial variant of the C-130E Hercules military transport, experienced rapid cabin depressurization while operating a scheduled cargo flight from Bethel Airport (PABE) to Elmendorf Air Force Base (PAED) in Anchorage. The incident occurred 100 nm east of Bethel, with the flight operating under an IFR flight plan in morning VMC. The crew declared an emergency and diverted to Iliamna Airport, where they made an uneventful landing. Subsequent examination of the aircraft revealed a large hole in the forward pressure bulkhead canted web.
Low Rotor RPM Preceded Hawaii Air-tour Helicopter Crash
Bell 206B, near Honolulu, Hawaii, Feb. 18, 2016–The local air-tour flight was maneuvering in daytime VMC near the USS Arizona Memorial near Pearl Harbor when the pilot felt a vibration and then heard a grinding noise followed by a loud bang. The instruments showed the engine was still operating, but rotor rpm was decreasing. The pilot entered an autorotation to a grassy area near Contemplation Circle at the memorial, and then attempted a left pedal turn to avoid several people in that the area. The helicopter then descended rapidly into the water 20 feet from the shoreline.
Witnesses at various locations at the memorial site reported seeing the helicopter traveling at a low altitude before it suddenly descended. The day after the accident, the wreckage was raised from 40 feet of water and rinsed with fresh water, with all major structural components recovered. Four people on board were injured, one seriously; a fifth, a teenage passenger, later perished from his injuries.
FACTUAL
Evidence of Icing in Twin Commander Crash
Twin Commander 690C, near Bellevue, Tenn., Feb. 3, 2014–The pilot of the twin-turboprop corporate aircraft had made two prior attempts to land at Nashville John C. Tune Airport (JWN) in daytime IMC before crashing on the third approach to the airport, with icing a potential factor, according to an updated NTSB factual report.
The flight was operated by a private pilot with three passengers on board. The pilot had picked up the aircraft earlier in the day from Clarence E. Page Municipal Airport (RCE), Oklahoma City, Okla., following a 150-hour inspection. The accident flight was operated under an IFR flight plan from Great Bend Municipal Airport (GBD), Great Bend, Kan., to JWN.
At 16:28 the pilot was cleared for a GPS (Rnav) approach to Runway 2 at JWN. At 1629:27 the pilot stated, “I’d like to climb and uh review the approach and uh do it again.” The pilot was then directed to maintain 3,000 feet and turn right to a heading of 020 degrees. The pilot acknowledged the clearance correctly, but turned to a heading of 200 degrees. The controller told investigators she did not correct the pilot’s action, as “the incorrect heading did not create a conflict with any other traffic.”
Nine minutes later, ATC asked if the pilot was re-established on the GPS Runway 2 approach to JBN, to which he responded in the affirmative. The controller then noted the aircraft was a half mile east of the final approach course, which the pilot confirmed. At 16:42 the pilot reported going missed a second time.
At 16:53 the pilot received clearance for a third GPS approach to Runway 2 at JWN. Two minutes later, ATC informed the pilot that radar services were terminated and instructed him to report cancelling IFR either on the ground or in the air. The controller also advised the pilot of traffic 10 miles in trail. The pilot did not acknowledge these transmissions, and no further communications were received from the aircraft.
The aircraft crashed in a field nine miles south of JWN, killing all four people on board. Radar data indicated the airplane had been on the final approach course when it veered left to 210 degrees and descended into terrain. Observed weather conditions at JWN at the time of the accident reported wind from 360 degrees at 5 knots, with visibility of five statute miles under an overcast ceiling at 800 feet. Observed temperature was 41 degrees F with a dew point of 25 degrees F.
An Airmet for IFR conditions was in effect for the area, indicating ceilings below 1,000 feet and visibility less than three miles. No advisories for icing were in effect, although three Pireps for icing conditions in the Nashville area were included as part of the last weather briefing obtained by the pilot at 15:38. The NTSB noted the procedures for flight in icing conditions and operation of anti-icing equipment as outlined in the aircraft’s operating handbook, adding that impact damage precluded any evidence to show if these systems had been engaged before the accident sequence.
A performance study of the aircraft’s flight path during the approach, conducted by the NTSB, found the aircraft had slowed to 111 knots when it began a shallow left turn away from the final approach course. Eighteen seconds later, the aircraft had slowed to 108 knots while still turning, before descending suddenly at more than 10,000 fpm. Investigators added that the aircraft’s published clean stall speed was 77 knots in level flight, increasing to 108 knots in a 60-degree level turn, assuming the wings were free from contamination.
FINAL
Improper Procedures, Incorrect Radio Frequency Factors in Alaska Commuter Fatal
Cessna 208B, Saint Mary’s, Alaska, Nov. 29, 2013–An improperly selected radio frequency was one of several factors that contributed to the 2013 downing of an Era Aviation Cessna 208 Caravan that killed four deaths and seriously injured six.
The scheduled commuter flight departed Bethel Airport (AKST) in Bethel, Alaska, at 5:41 p.m., 40 minutes behind schedule, with the intended destination of Mountain Village Airport (PAMO). The flight operated under nighttime VFR, despite reported IMC along the route of flight. Before reaching Mountain Village, the pilot diverted to St. Mary’s Airport (PASM) because of the deteriorating weather conditions, and subsequently requested and received a special VFR clearance to land at St. Mary’s.
Witnesses on the ground reported deteriorating visibility in fog and ice, and saw the aircraft enter a controlled, descending right turn into terrain one mile from the runway. After attempting to contact the pilot by radio, the witnesses determined the aircraft’s last reported position via the company’s flight tracking software, and they located the wreckage near that position one hour later.
Examination revealed that the aircraft’s radio remained tuned to the ARTCC frequency and that the pilot had attempted to activate the pilot-controlled lighting at PASM on that frequency, not the airport’s CTAF. The NTSB determined that deteriorating weather conditions, restricted visibility in fog, and lack of runway lighting all contributed to the pilot’s probable loss of situational awareness and resulting CFIT while attempting to perform a visual approach to land at PASM.
Investigators also determined that two company flight coordinators had failed to discuss the flight’s calculated risks and weather conditions with the pilot, as required by the company’s risk-assessment program, and that neither of the coordinators had received training in that program. At the time of the accident the company did not require signoffs on the risk-assessment form by either flight coordinators or pilots.
Furthermore, the NTSB discovered that the FAA had performed numerous control inspections at the operator’s location, with investigators “repeatedly” noting problems with the company’s training, risk management and operational control procedures. The NTSB determined that the agency had not held the operator “sufficiently accountable” for correcting these deficiencies.
‘Dynamic Rollover’ Led to Bell 206 Takeoff Accident
Bell 206B-III, Missoula, Mont., April 4, 2014–Following a flight conducted in daytime VMC by a pilot under evaluation by the operator, Minuteman Aviation (MAI), for possible employment, MAI’s chief pilot took the left seat for a second flight from Missoula International Airport (MSO) to the company practice area, a dry and level patch of ground adjacent to the airport property. The pilot under evaluation landed on the field, which she described to investigators as a “normal dry livestock field.” The approach and landing were made into the wind, on a heading described as roughly parallel to Runway 29 at MSO.
After a brief discussion, during which it was agreed that the chief pilot would take the controls to demonstrate the next flight maneuver to the evaluee, the chief pilot attempted a liftoff. He told investigators that the helicopter’s right skid felt “stuck” to the ground, and he was not able to successfully level the helicopter before it rolled onto its right side, incurring significant damage to the fuselage, tail boom and main rotor. The chief pilot shut the helicopter down and both occupants exited the aircraft. They were unable to note any obvious cause of the “stuck” skid before a post-impact fuel leak and small fire curtailed their efforts.
A wind speed and direction indicator in the airport’s control tower recorded sustained wind from 290 of between 10 and 18 knots around the time of the accident, gusting to 22; however, a separate wind indicator as part of an automated surface observation system (ASOS) 2,500 feet north-northeast of the accident site recorded wind direction varying between 267 and 298 degrees magnetic, with speeds of 10-17 knots, gusting to 20 knots.
No mechanical deficiencies or failures were noted before the accident, or through a post-accident examination, and no evidence could be found to substantiate or refute the chief pilot’s belief that the right skid had become stuck to the ground.
The NTSB determined the likely cause of the accident was dynamic rollover, a condition that the FAA Rotorcraft Flying Handbook (H-8083-21) defines as “a lateral rolling tendency” in single-rotor helicopters on liftoff, when “right side skid down” and “crosswinds from the left” act in conjunction with the rotational direction of the main rotor blades to upset the helicopter.
ADS-B Data Helps Determine Sequence of Events in C208 Downing
Cessna 208B, Kwethluk, Alaska, April 8, 2014–Investigators used automatic dependent surveillance-broadcast (ADS-B) flight tracking data to help determine the chain of events leading to the crash of a Cessna Caravan that killed both pilots during a training flight.
The accident occurred during the first training flight for a newly hired second-in-command (SIC) for Hageland Aviation Services, dba Ravn Connect. About 21 minutes into the flight in daytime VMC, the aircraft entered a steep descent from 3,400 feet msl and struck terrain. A review of the check airman’s past training flights, including interviews with other pilots and examination of archived ADS-B data, revealed that the initial aircraft upset during the accident flight coincided with the time he would typically simulate an in-flight emergency and descent.
Post-accident examination showed the aircraft was configured for cruise flight at the time of the accident, with all control cables intact. Investigators determined that the aircraft had been trimmed for an abnormal nose-down configuration immediately before the crash, consistent with a simulated pitch trim excursion during the training flight.
Simulated aircraft performance calculations prompted the NTSB to conclude that aircraft “control forces required to counter an anomaly increase to unmanageable levels unless the appropriate remedial procedures are quickly applied,” and that it was “likely that the check airman simulated a pitch trim excursion and that the SIC, who lacked experience in the airplane type, did not appropriately respond to the excursion.” The NTSB cited the check airman for failing to implement corrective action in time to prevent loss of control.