Split Main Rotor Found in R66 Wreckage
Robinson R66, Wikieup, Ariz., June 23, 2016—Both occupants, a commercial pilot and commercial pilot-rated passenger, died when the turbine-powered light helicopter crashed in unknown conditions during a cross-country positioning flight from Prescott, Ariz., to Riverside, Calif. The helicopter left Prescott at 1:40 p.m. local time in daytime visual meteorological conditions (VMC) to transport the pilot to take a Part 135 chief pilot checkride; the operator’s Part 141 chief pilot was the passenger.
The wreckage was located the following morning in hilly, desert terrain, with a debris field 750 yards long and 150 yards wide, with the left side of the fuselage more fragmented than the right. Left- side cabin and instrument pieces were located near the initial impact area, with the tail boom located midway into the debris field. The cabin was found inverted 600 yards into the debris field, and had been destroyed in a post-impact fire. The outboard five feet of a main rotor blade afterbody had detached from the leading edge spar, and the transmission, mast and second main rotor blade had separated as a unit. The engine remained attached to the airframe, and the main rotor driveshaft was bent approximately 15 degrees at the swashplate.
TBM 700 Pilot Diverted After Gear-Up Landing
Daher TBM 700, Evart, Mich., Apr. 14, 2015—During a Part 91 instructional flight in day VMC, the aircraft landed on Runway 24 (3,800 feet by 75 feet) at Evart Municipal Airport (9C8) with the gear up and subsequently diverted to Roben-Hood Airport (RQB) in Big Rapids, Mich., where it landed uneventfully with the landing gear extended. The accident was not reported to the FAA before discovery of the aircraft, by an FAA inspector from the Grand Rapids Flight Standards District Office, while it was undergoing repair in Florida.
The flight instructor on board said he and the aircraft’s owner departed 9C8 to perform VFR airwork, including steep turns and slow flight, followed by two uneventful landings at 9C8 using different flap settings. During the approach to the third landing with no flaps, the pilot failed to extend the landing gear at midfield downwind as had been done on the prior two landings. As the airplane descended into ground effect, the pilot and the flight instructor realized that the landing gear was not extended and “took immediate steps to go around,” but the rear ventral strikes, a portion of the aft belly and the propeller contacted the runway before descent could be reversed. After assessing aircraft damage and controllability on climb-out, the pilots opted to divert to RQB.
According to the pilot, the flight was part of a checkout on the TBM 700 required by his insurance company. The accident flight was the pilot’s first with the instructor, who had been recommended by the insurance company, after he went through “a lot of ground stuff” as part of his training in the accident airplane. The pilot told investigators he was not aware there was no gear warning alarm or light without the flaps extended, and said he was “distracted” from watching the airspeed and attitude of the airplane. During touchdown he heard the noise from the airplane’s contact with the runway and chose to abort the landing because “there was not much runway left.”
The pilot’s logbook showed that he had received 19.7 hours of dual instruction in the TBM 700, with no pilot-in-command flight time recorded.
JetProp Pilot Had Ambien, Marijuana in System
Piper PA-46-310TP, in Lehman, Texas, June 18, 2014—While a recently issued Probable Cause report officially cites a pilot’s decision to continue flying into a region of known adverse weather—as well as failure by ATC to provide critical weather information—as the primary factors in a 2014 fatal crash in Texas, the report also points to other factors indicating that the pilot’s decision-making abilities might have been impaired.
The cross-country personal flight originated from Aspen-Pitkin County Airport/Sardy Field (KASE), Aspen, Colo., at 1:26 p.m. local time, en route to Brenham Municipal Airport (11R) in Brenham, Texas on an IFR flight plan. Day IMC prevailed at the time of the accident, with “multiple weather resources” indicating rapidly developing convective activity with potential for moderate to severe turbulence, hail, lightning, heavy rain and high wind, and cloud tops near 48,000 feet.
The pilot checked in with the Albuquerque Air Route Traffic Control Center (ZAB) controller at FL270 at 3:17 p.m. local time, and four times over the next 10 minutes indicated altitudes 300 to 400 feet higher than the assigned altitude. At 3:30 p.m., the ZAB controller issued a Fort Worth Center Weather Advisory (CWA) and handed off control of the accident aircraft to the next controller five minutes later.
After a second altitude deviation, the controller queried the pilot and was told the aircraft was having autopilot issues. The pilot also asked to deviate east of course for weather. The controller granted the request; however, the aircraft then deviated west. During this time, a flight of two F/A-18s passed below the Piper’s track at FL250 and, according to the flight lead, encountered moderate clear icing. They requested and were approved to descend to FL190.
Between 4:08 and 4:17 p.m., the Malibu’s altitude continued to vary between 400 feet and 1,000 feet below FL270. At 4:17, the pilot checked in with a Fort Worth ARTCC controller (ZFW) at FL260, climbing to FL270, and advised the controller he was turning to avoid weather. At 4:30 p.m., the aircraft began a climbing left turn, with the pilot telling the ATC he “was trying to go through a window.” The pilot did not respond when asked by ATC if he needed a higher altitude.
The controller then advised the pilot that radar showed that he was in the middle of moderate to extreme precipitation, and asked if he needed a different altitude. The pilot did not respond. Thirty seconds later, the controller again tried to establish communications, without success, but this was followed immediately by a single “Mayday” transmission on the frequency. Two other aircraft in the area relayed to ATC that they had also heard the Mayday call. At 4:32 p.m. the controller asked the accident pilot to say altitude, and the pilot responded with “nineteen.”
At 4:35 p.m., the Malibu pilot reported that he was in a spin, and did not respond when asked if he could see the ground by the ZFW and one of the nearby aircraft pilots. A third aircraft in the area volunteered they had heard the accident pilot say he was spinning, and that he had lost sight of the ground or horizon. No further communications were received from the Malibu, and wreckage was subsequently located in an open field. The pilot was killed.
Airframe damage and ground marks were consistent with impact in a level attitude while in a flat spin. No apparent mechanical anomalies were noted that would have precluded normal operation before the loss of control and impact with the ground, and investigators could not substantiate the pilot’s report of an autopilot problem.
Autopsy results showed the pilot had coronary artery disease, which investigators noted could lead to an acute coronary syndrome with symptoms such as chest pain, shortness of breath, palpitations or fainting; however, they determined that would have been unlikely to have impaired the pilot’s judgment following a preflight weather briefing or while en route.
Additionally, toxicology results identified signs of two potentially impairing substances in the pilot’s blood: zolpidem, a prescription sleep aid marketed as Ambien, as well as 2.2 ng/ml of tetrahydrocannabinol (THC), the active ingredient in marijuana. The NTSB determined it was “unlikely” that zolpidem levels would be enough to impair the pilot’s performance, but could not determine if the pilot’s use of marijuana might have been a factor in the accident.
NTSB: Uncommanded Prop Feather on Takeoff Led to B1900 Crash
Beechcraft 1900, Miami, Fla., Feb. 11, 2015—The NTSB determined that the crash of a Venezuelan-registered B1900 turboprop twin stemmed from the uncommanded feathering of its left propeller, but investigators could not positively determine why the prop feathered. The two pilots and two passengers on board were killed.
The aircraft departed Runway 27L at Miami Executive Airport (KTMB) at 2:37 p.m. local time in day VMC, on an IFR flight plan to Providenciales International Airport (MBPV), Providenciales, Turks and Caicos. Two seconds after the flight crew called “rotate,” the cockpit voice recorder (CVR) caught a sound consistent with decreasing propeller RPM followed shortly by “engine is lost” and the sound of landing-gear retraction.
The flight crew reported engine failure to ATC, and replied affirmative when asked if they wanted to return to TMB. The controller then offered a 180-degree turn to Runway 9R, but the crew requested a traffic pattern to Runway 27L, which the controller approved with left turns in the pattern. Shortly afterwards, the flight crew reported that they needed to turn left downwind, and the controller cleared them to land on Runway 9R. The aircraft then slowed, and descended from 300 feet agl in a cross-controlled attitude until it stalled and struck terrain.
NTSB review of flight data recorder (FDR) data revealed that the left propeller rpm dropped to 60 percent immediately after rotation, and the left engine torque climbed off the scale, beyond 5,000 foot-pounds. Both indications are consistent with the left propeller twisting to the feathered position and the engine torque increasing in an attempt to maintain propeller rpm.
Post-accident examination of the wreckage revealed that the rudder trim actuator was at its full-right limit, consistent with the pilots’ efforts to counteract the left engine drag before its shutdown. This evidence suggested to the NTSB that the flight crew likely did not readjust the trim once the drag was alleviated, which resulted in the airplane being operated in a cross-controlled attitude for about 50 seconds with a left bank and full-right rudder trim. A proper response from the crew to the power failure would have allowed the aircraft to continue climbing at 500 fpm, according to investigators.
Teardown of the left engine and propeller did not reveal any pre-impact mechanical anomalies. Review of the airplane maintenance manual revealed instructions to check the propeller reversing linkage on the front end of the engine, which controlled the beta valve, for proper rigging during propeller installation. The manual also contained a warning that misadjustment of the beta valve could cause unplanned feathering of the propeller.
According to the aircraft manual, the ground/flight idle solenoid energizes when weight lifts off the wheels, as during takeoff. This further opens the beta valve, which the NTSB noted could exacerbate an existing misrigged condition as soon as the airplane becomes airborne; however, impact damage prevented investigators from verifying the beta valve rigging.
Two days before the accident, the left propeller was removed for overhaul and replaced with another overhauled propeller. During an interview, the aviation maintenance technician (AMT) who removed and replaced the left propeller said the pilots had reported on February 7 that the propeller was not achieving the correct power setting or pitch angle. The AMT said he completed the propeller removal and replacement in about six hours, and that he followed the airplane maintenance manual and only needed to disconnect the beta arm to perform the work. The AMT subsequently checked his own work and concluded with an operational check of power and performance.
The NTSB further noted that FDR data was consistent with the flight crew not performing the Before Takeoff checklist, which includes a low-pitch solenoid test that would have energized the solenoid and possibly driven the left propeller uncommanded to feather during ground operations.
Errant Towel Downed Logging Huey
Garlick UH-1B, near Kettle Falls, Wash., May 7, 2015—The NTSB determined that an improper post-maintenance inspection, which led to the engine ingesting a towel on a subsequent flight, caused the 2015 crash of a logging helicopter. The helicopter lost all engine power while performing a Part 133 external-load logging flight in day VMC, and sustained substantial damage after colliding with trees on a wooded slope. The sole-occupant pilot suffered minor injuries.
The commercial-rated pilot told an NTSB investigator that she had been performing logging operations for the past four days, and that the helicopter’s Lycoming T53-L-13B turboshaft had been replaced the day of the accident. The operator’s chief pilot conducted a short test flight following maintenance, after which the long-line was attached to the helicopter and the pilot conducted a 50-minute logging cycle. She then returned to the landing zone and refueled, planning on another 80-minute logging cycle.
Approximately 50 minutes into the second cycle of the day (22 picks) the pilot heard a loud screeching/grinding noise while maneuvering 200 to 300 feet above the tree line, followed by a muffled “bang” and then the low rotor RPM horn. She entered an autorotation, maneuvering to touch down upslope. The helicopter rolled down the slope several times before coming to a stop, at which time the pilot exited the helicopter through the side bubble window. She noticed the engine was smoking.
Investigators verified drivetrain continuity from the tail-rotor drive shaft to the transmission during post-accident examination, with rotation of the tail rotor driveshaft producing the expected corresponding movement of the main rotor. There was no sign of airframe malfunctions or failures, and the outside of the engine appeared intact with visible damage. The interior of the engine exhaust tail pipe showed signs consistent with internal overheating.
Examination of the engine’s inlet guide vanes (IGV) revealed material consistent with a towel within the various vanes. The IGV trailing edges appeared to be displaced forward and distorted, with signs consistent with foreign object debris damage. Material consistent with a towel was also seen in the compressor section.