No safety recommendations in report into Shannon incident

NO safety recommendations have been made following the publication of a report into an incident on Shannon Airport’s runway in December 2, 2019 when the nose gear of light aircraft collapsed after landing.

The Air Accident Investigation Unit (AAIU) of the Department of Transport has issued its final report into an incident the nose landing gear of the Piper PA23 aircraft collapsed, causing the aircraft’s two propellers to strike the runway.

The aircraft came to rest on the left side of the runway. The pilot, who was the sole occupant, was uninjured and exited the aircraft safely. The 36 year-old had 284 hours flying experience, of which 82 were on type. There was no fire after the landing.

The Airport Fire and Rescue Service attended the scene, and as a precaution, covered the aircraft and the adjacent runway surface in a blanket of fire-retardant foam.

On January 12 2022, the perator informed the Investigation that following a take-off from Shannon Airport that morning, the nose landing gear would not retract.

Subsequent troubleshooting found evidence of two hydraulic leaks, a low hydraulic quantity, and contamination in the hydraulic filters.

The engine-driven hydraulic pumps were removed and sent for overhaul, which identified the left-hand pump to be unserviceable.

The operator was of the opinion that the low hydraulic quantity resulted in cavitation and damage to the left-hand hydraulic pump, which resulted in contamination of the hydraulic system, causing the nose landing gear not to retract on January 12, 2022.

Following the occurrence, the operator inspected and tested several landing gear/hydraulic system components as well as replacing the engine-driven hydraulic pumps and flushing the hydraulic system.

Furthermore, the operator reported that several flights had been subsequently flown and that the landing gear and its indication system had operated normally.

In addition, a repeat inspection of the hydraulic filters was performed, as required, on 21 December 2021 with no adverse findings noted. New filter elements were installed at this time.

The investigation reviewed several possible reasons for the nose landing gear down-lock latch assembly not being fully engaged after the landing gear had been selected to the down position on
the flight from Kerry Airport to Shannon Airport to Kerry Airport.

The investigation considers that free play in the nose landing gear down-lock latch assembly combined with anomalies within the powerpak and/or air in the hydraulic system were the most likely technical factors in the occurrence.

Regarding human factors, the report found flickering of the nose landing gear down indication light on the previous flight, prior to a successful landing, may have adversely affected the pilot’s trust in the landing gear indication system.

This report does not sustain any safety recommendations.

The report concluded the Airworthiness Certification for the aircraft and the pilot’s licence and medical certificate were valid for the flight being undertaken.

This was the aircraft’s first flight following the completion of extensive maintenance activity on the aircraft.

Maintenance personnel removed and refitted the bulb in the nose landing gear down indication light assembly during troubleshooting for an alternator fault carried out before the first flight to Kerry Airport.

The pilot reported that when the aircraft was on the approach to Kerry Airport, during the flight conducted immediately prior to the occurrence flight, the nose landing gear indication light was flickering, prior to coming on steady. This was followed by a normal landing at Kerry Airport.

Before operating the aircraft on the return flight to Shannon Airport, the operator was not informed that the nose landing gear indication light was flickering during the approach to Kerry Airport.

The pilot reported that when the aircraft was on the approach to Shannon on the occurrence flight, the nose landing gear indication light was flickering. The pilot did not recall if the light came on steady prior to the landing.

The AAIU report stated the nose landing gear collapsed when the nose of the aircraft was lowered during the landing on RWY 24 at Shannon.

As a result of contact with the runway surface, the tips of both propellers were bent rearwards and the lower surface of the aircraft’s nose section sustained abrasion damage.

The soldered joints between the electrical wiring and the bulb fitting were found to be in poor condition when the nose landing gear down indication light assembly was removed from the aircraft following the occurrence.

Significant free play was found in the nose landing gear down-lock latch hook pivot.

System testing identified that when the landing gear selector lever was selected to the down extend position, the pressure in the down line was not maintained in accordance with Service Manual limits.

During workshop examination, the release detent screws on the powerpak for both the landing gear selector lever and the flap selector lever were found to have been unscrewed by approximately half an inch.

The landing gear selector lever did not return to the neutral position during system testing when the landing gear was selected to the UP (retract) position and the gear had fully retracted.

On January 12, 2022, the nose landing gear would not retract following a take-off from Shannon. While it cannot be conclusive, the investigation considers that this event was not related to the December 2, 2019 occurrence.

The report found a probable cause was the nose landing gear was not locked in the down position at the time of landing.

“Free play in the nose landing gear down-lock latch hook pivot, combined with anomalies within the powerpak and/or air in the hydraulic system, were the most likely technical factors in the occurrence.

“The flickering of the nose landing gear down indication light on the previous flight, prior to a successful landing, may have adversely affected the Pilot’s trust in the landing gear indication system.

“The flickering of the nose landing gear down indication light on the previous flight was not reported to the operator prior to the occurrence flight,” the report outlined.