Preliminary Reports

Super Puma Investigation Focuses on Tail Rotor Drive Assembly

Aerospatiale (Airbus Helicopters) AS332L1 Super Puma, Nov, 22, 2024, 41 km north-northwest of Hay Aerodrome, New South Wales, Australia

Australian Transport Safety Bureau investigators probing the emergency forced landing of the twin-engine helicopter found that “the splined sleeve supporting the pitch change control plate had fractured at the mounting flange.” The detachment of the control plate appeared to be “the likely reason for the uncommanded yaw” that precipitated the accident sequence.

The helicopter departed from Broken Hill Airport in New South Wales (YBHI) on the last leg of a ferry flight from Kuala Lumpur, Malaysia to Albury, N.S.W. where it was to be used in firefighting over the summer season. While in cruise at 3,500 feet, about an hour and a half after takeoff, the pilot and passenger noticed a high-frequency vibration “throughout the airframe.”

The pilot lowered the collective and began descending with the intention of landing at Hay Airport (YHAY), then about 22 nm from their position. Recorded flight track data indicates a descent rate of about 1,500 fpm at an airspeed of 115 knots.

During the descent, “a loud thud…was immediately followed by an uncommanded yaw to the left.” The pilot set up a straight-in autorotation to an open field and tried to reduce both throttles to idle, accidentally shutting down the number two engine in the process. The yaw stopped with the reduction in power but resumed when the pilot raised the collective in the landing flare. The helicopter initially touched down upright facing opposite the direction of flight, then rolled onto its right side. There was no post-impact fire. Both the pilot and passenger were seriously injured; the passenger subsequently died, and the helicopter was destroyed.

Citation Damaged in Rejected Takeoff

Cessna Citation 560, Dec. 27, 2024, Pagosa Springs, Colorado

The twin-engine corporate jet sustained “substantial damage to both wings” when it overran the end of Runway 01 following a rejected takeoff. The two pilots, eight passengers, and three dogs on board were not injured. The Part 91 personal flight was departing for Tulsa Riverside Airport (KRVS).

The pilot recalled that the airplane seemed to accelerate normally to its calculated 96-knot decision speed (V1) and 103-knot rotation speed (Vr) but would not rotate even with full aft yoke.

At an indicated airspeed of 120 knots, she rejected the takeoff, using full reverse thrust and maximum braking. The jet went off the end of the 8,001-foot runway and into the grass, where the passengers and crew deplaned. The pilot subsequently said that “the airplane did not feel like it had enough power and did not seem to accelerate at the correct rate based on the calculated performance data.” The apparent discrepancy between the statements was not initially explained.

Final Reports

Flight-Test Procedures Faulted in Caravan Break-Up

Textron Aviation C208B, Nov. 18, 2022, Snohomish, Washington

Onboard video recordings, ADS-B track data, and post-accident simulation confirmed that the flight-test crew exceeded the airplane’s airspeed limitations not only on the accident flight but also during a flight on the previous day. All four crew members died when the Caravan broke up about 7,000 feet above ground level; the final ADS-B data point showed a descent rate of 8,700 fpm.

The flights were conducted as part of the test protocol in support of a new supplemental type certificate. After flying several other maneuvers from their test card, they configured the airplane to perform an accelerated stall with full flaps in a 30-degree bank and the engine set to produce 930 foot-pounds of torque. ADS-B data adjusted for winds aloft indicated that after a gradual left roll to 30 degrees bank, calibrated airspeed quickly dropped from 105 to 48 knots. Data recorded by the Pratt & Whitney engine monitoring system showed the airspeed dropping to 35 knots as the Caravan climbed at 2,560 fpm, then quickly increasing to 223 knots as it descended at a rate that peaked at 14,000 fpm. Engine torque increased to 2,200 foot-pounds. The airplane’s published maximum operating speed was 175 knots; maximum flap extended speed was 150 knots.

Witnesses saw the airplane break apart in flight. The resulting debris field spanned 1,830 square feet. The onboard flight test data acquisition system was destroyed, and no data from the accident flight was recovered.

An NTSB simulation informed by ADS-B flight track data showed that after the stall the Caravan rapidly rolled 120 degrees left while pitching 60 degrees nose-down. Analysis of the aerodynamic loads imposed showed that they exceeded the wing’s designed stress load limits. Onboard footage recovered from one of the previous day’s test flights also showed that during a full-flaps stall at idle power in a 30-degree bank, the airplane rolled left to a maximum bank of 83 degrees before the pilot could level the wings. During the recovery he pitched down 25 degrees to “get some airspeed back.” Airspeed reached 183 knots before the pilot corrected the acceleration.

The NTSB report noted that although the 83-degree bank “exceeded the allowable roll limit during this maneuver,” the crew did not identify the exceedance or even query the onboard data acquisition system to determine the maximum bank angle reached. Under the test plan, the roll exceedance should have been considered a failed test, halting further testing until the reason for the exceedance could be determined and corrective measures implemented prior to attempting higher-risk maneuvers. The airspeed excursion above the maximum operating speed should also have triggered the overspeed inspection laid out in the Caravan’s maintenance manual, but there is no record of that inspection having been performed.

Cause Undetermined in 2022 Runway Overrun

HondaJet HA-420, March 7, 2022, Quebec, Canada

The Transportation Safety Board of Canada (TSB) could not determine a cause for a 2022 runway overrun in Canada, according to a final investigation report issued January 28. The event occurred at Montréal/St-Hubert Airport, Quebec (CYHU), and the aircraft was operated by Skyservice Business Aviation.

According to the report, the aircraft touched down on a wet runway and the pilot applied brakes. However, the deceleration was significantly lower than expected, causing the HondaJet to overrun the runway by approximately 700 feet. Two crew members and four passengers were on board, but no injuries were reported, and there was no damage to the aircraft in the incident.

The TSB found that the runway used was sufficiently long for the landing and not contaminated by ice at the time of the incident. There were no signs of hydroplaning, and the aircraft’s speed was appropriate. The flight crew adhered to the operator’s stabilized approach criteria, and the aircraft was found to be in compliance with maintenance regulations. A post-occurrence inspection detected no failures in the braking system.

Skyservice Business Aviation has implemented safety actions for the operation of its HondaJet HA-420 aircraft, including modifications to the aircraft’s flight manual supplement concerning landing performance on wet and contaminated runways.

The TSB has noted that runway overruns remain a key focus area on its Watchlist. The report underscores the importance of having adequate safety areas beyond runway ends to mitigate the potential consequences of overrun events.

Inoperative CHT Gauge One Factor in Ferry Flight Crash

Antonov AN-2, Nov. 14, 2022, Opa-Locka, Florida

The ferry flight crew experienced engine loss and attempted to land the radial engine-biplane on a levee. Evidence showed “the main landing gear being too wide for the airplane to land on the levee, and damage consistent with the airplane having traveled off the left side of the levee, nosing over, and coming to rest inverted.”

Post-accident investigations revealed that the airplane was equipped with an oil cooler under the fuselage with electrically--controlled shutters to regulate airflow. These shutters were found in the closed position at the time of the accident. The engine cowling’s flaps, which control airflow to the engine, were also closed during both engine runup and takeoff. Examination of the engine’s oil system revealed metal contamination inside the oil filter, pump filter, and strainers, suggesting internal damage had occurred before the power loss.

The cockpit instruments and switches were labeled in Cyrillic script, and the pilot had only partial excerpts of the aircraft’s flight manual, which were in Spanish. “The manual also listed reference airspeeds in miles per hour, though the airplane was marked in kilometers per hour,” the NTSB final report stated. The oil cooler and cowl flap switches, located next to each other, were found in the off position after the accident.

The pilot, who was also an airframe and powerplant mechanic with an inspection authorization, said he had performed preflight inspections on three separate visits before the accident. However, he did not use a checklist and could not recall whether the cowl flaps were open during the flight. He also did not remember any details about the oil cooler operation. “When asked if everything was working correctly, he advised that the cylinder head temperature [CHT] gauge did not work,” the report noted. “When asked when he noticed that it did not work, he advised that it was on the very first runup.”

The NTSB concluded that the pilot’s failure to properly configure the engine’s cooling systems and his decision to fly with an inoperative CHT gauge were the primary causes of the engine’s overheating and subsequent power loss. The pilot’s lack of familiarity with the aircraft’s systems, combined with his failure to monitor engine temperatures, directly led to the loss of power. ζ

— Amy Wilder contributed to this report.