Preliminary Reports
Missed Turn Preceded Nature Air Disaster
Cessna 208, Dec. 31, 2017, Punta Islita, Costa Rica—A witness reported that the second of two Nature Air Caravans departing the Islita Airport failed to make the right turn toward the only pass through the surrounding hills. Instead, the Caravan, which took off about 15 minutes after company traffic, maintained runway heading into a rising valley that ends in a blind canyon. All 10 passengers and both pilots were killed. Details of the pilots’ experience and familiarity with the terrain have yet to be disclosed.
Costa Rica’s Civil Aviation Administration suspended the operating certificate of Nature Air, which advertises itself as the country’s “largest domestic airline,” on January 11, but restored its authorization to fly on February 5. All of the passengers were U.S. citizens; both pilots were Costa Rican nationals.
First Legal Actions Filed in Mumbai King Air Accident
King Air C90B, June 28, 2018, Mumbai, India—The husband of copilot Marya Zuberi, one of five killed when the King Air crashed into a construction site on its first test flight following extensive renovations, has filed police complaints requesting investigations not only of the airplane’s operator and its maintenance provider, but also airport operator Brihanmumbai Municipal Corporation (BMC), the Airports Authority of India (AAI), and India’s Directorate General of Civil Aviation (DGCA). Prabhat Kathuria’s filings allege that the operator pressured his wife, the pilot, and the two engineers killed in the accident to attempt the test flight despite unsuitable weather, and also fault the BMC for allowing incompatible high-rise development under the approach paths to Mumbai’s Juhu Airport.
His claim that the King Air was “not better than a junk aircraft” extensively used for technician training was disputed by owner UY Aviation, which claims to have spent five times the aircraft’s purchase price rebuilding it for service as an air ambulance. Maintenance provider Indamer MRO’s inventory of parts replaced during that effort includes both engines and propellers, landing gear, brakes, and flight instrumentation. The aircraft accumulated more than a month of ground testing between initial authorization from the DGCA and the actual test flight.
Terrain Alerts Suppressed in Alaska Floatplane Crash
de Havilland DHC-3T, July 10, 2018, Hydaburg, Alaska—The pilot of a Turbine Otter that crashed into a mountainside between Steamboat Bay and Ketchikan told NTSB investigators that the floatplane’s terrain awareness and warning system (TAWS) was in “inhibited” mode to suppress ground proximity warnings. Six of the ten passengers on board the Taquan Air charter flight suffered serious injuries when their airplane hit Jumbo Mountain on Prince of Wales Island while maneuvering around low clouds. The other four passengers escaped with minor injuries, while the pilot was unhurt.
The NTSB’s preliminary report, released on July 17, includes two passengers’ accounts of the airplane flying in and out of clouds just before the crash; one reported texting the passenger in the copilot’s seat to request that he ask the pilot to turn around. The pilot reported that visibility decreased “from about three to five miles to nil” as the floatplane entered the Sulzer Portage. After initiating a climbing 180-degree turn, he was “momentarily disoriented” by what appeared to be a body of water ahead. By the time he recognized the mountainside in front of the airplane and attempted a steep emergency climb at full power, the aircraft was no longer in a position to clear terrain.
Coast Guard rescuers located the wreckage more than four hours after the accident and evacuated the victims to Ketchikan with the assistance of Temco Helicopters. In its preliminary report, the NTSB drew attention to its Safety Recommendation A-17-35, issued in the wake of a fatal June 2015 accident involving a Turbine Otter in the same vicinity, which calls for the FAA to “implement ways to provide effective terrain awareness and warning system (TAWS) protections while mitigating nuisance alerts for single-engine airplanes operated under 14 Code of Federal Regulations Part 135 that frequently operate at altitudes below their respective TAWS class design alerting threshold.” The FAA has yet to respond.
Final Reports
Failure To Use Supplemental Oxygen Led to Uncontrolled Descent
Cessna 501, May 23, 2016, Texarkana, Arkansas—Contrary to federal aviation regulations, the sole pilot of a Cessna Citation was not wearing an oxygen mask when the jet experienced an explosive decompression at FL430. The 15,000-hour airline transport pilot and all three passengers lost consciousness and the jet entered an uncontrolled descent, plunging 36,000 feet before the pilot regained consciousness and recovered control of the aircraft. Both wings were damaged by the aerodynamic loads imposed during the recovery, but the emergency landing in Texarkana was uneventful.
In its final report, the NTSB traced the sudden loss of cabin pressure to the combination of a loose clamp that allowed the air conditioning system’s primary pressurization duct to become disconnected from the water separator and a fractured flapper in the aft bulkhead check valve. The separation of the duct diverted pressurized air into the unpressurized section of the airframe, while the broken flapper allowed existing cabin pressure to escape. A Phase 5 inspection of the 1980-model airplane had been completed 38 days before the accident at a total time in service of 7,424.8 hours.
Errors by Ground Crew and Pilot Combined to Cause Fuel Exhaustion
McDonnell Douglas 369D, July 17, 2016, 36 km northwest of Hawker, Southern Australia—An interruption during his preflight inspection led the pilot to omit a visual check of the helicopter’s fuel levels, thereby failing to detect that the support crew had not refueled it the previous evening as claimed. The helicopter was one hour, forty-five minutes into a planned three-hour powerline inspection when its engine “just stopped” at an altitude of 100 feet. The pilot was able to steer the craft away from the wires toward a clear area, but he and the two utility workers on board suffered significant head, back, and spinal injuries in the hard landing that resulted. There was no post-crash fire. The fuel system remained intact, and investigators found no usable fuel in the wreckage.
The helicopter had been equipped with an auxiliary tank with a usable capacity of 115 liters (30 gallons) fabricated of stainless steel and located in the right rear side of the cabin. It was not equipped with a fuel gauge, sight glass, or any other quantity indicator. A solenoid valve operated by a switch on the instrument panel allowed fuel to flow by gravity into the main tank; a green light illuminated when the solenoid was energized, but the system provided no direct indication of fuel flow.
Before the flight, the pilot requested full fuel and was erroneously told that it had been refueled the previous evening, perhaps due to confusion with fueling between two flights that day. A discussion with another crew interrupted his preflight inspection and he forgot to look inside the auxiliary fuel tank’s filler neck, the only way to confirm it had been filled. The main tank’s gauge was a non-linear design intended to read more accurately at low levels than high, with very little difference in needle position between readings of “full” and three-quarters, and the position of the sun at the time of the accident made the instrument panel’s low fuel indicator light difficult to see.
Investigators also identified miscommunication in the approval process that led CASA to approve the auxiliary tank for normal-category operations when in fact approval had been intended only for temporary use during ferry flights. In response, the operator removed the auxiliary tanks from its entire fleet, requiring all aerial work to be conducted on the main tanks with adequate reserves.
Fatigue, Recent Transition Implicated in Lake Erie Crash
Cessna 525C, Dec. 29, 2016, Cleveland, Ohio—The pilot of a Cessna CJ4 that crashed into Lake Erie killing all six on board apparently believed that the airplane was flying on autopilot even though he never actually engaged it. The accident occurred just before 11 p.m. on a moonless night, making it unlikely that he was able to see the lake’s surface before impact. The NTSB noted that by that time the pilot had been awake for 17 hours, may have been susceptible to fatigue, and that he had less than nine hours as pilot-in-command of that model. Its instrumentation and panel layout differed significantly from those of the Cessna 510 (Mustang) he had previously owned and flown more than 370 hours.
The pilot, his wife, two sons, and two family friends had flown in from Columbus three hours earlier to attend a professional basketball game. The return flight was expected to take 30 minutes at an altitude of 12,000 feet. At 10:56 p.m., the jet was cleared to take off from Runway 24R of Cleveland’s Burke Lakefront Airport with instructions to turn right to a heading of 330 degrees and maintain an altitude of 2,000 feet. ADS-B track data showed that the Citation initially climbed at a rate of 6,000 fpm, reaching a maximum altitude of 2,925 feet 30 seconds after takeoff, then began to descend as its right turn reached a bank angle of 62 degrees and its pitch attitude decreased to 15 degrees nose-down. Impact occurred just over one minute after it began its takeoff roll.
Comparison of the instrument panels of the Mustang and CJ4 showed that the autopilot engagement buttons are in different locations, and there is not an adjacent indicator light in the CJ4. The only annunciation of autopilot engagement in the 525C is in the flight system status display in the upper section of the primary flight display (PFD). The PFD’s attitude indicator displays also differ, and the NTSB cited “negative learning transfer” as a factor in his failure to recognize that the autopilot had not engaged and the airplane was entering an unusual attitude.