Incident Overview
On 15 August 2023, a Piper PA-34-220T (registration G-ZZOT) conducting a training flight as part of a multi-engine instrument rating course was involved in a serious incident at Liverpool Airport. The aircraft’s propellers struck the runway during a go-around from a simulated one engine inoperative (OEI) approach that was inadvertently flown with the landing gear up.
Flight History
The flight had successfully completed a simulated OEI ILS approach and go-around to Runway 27. The aircraft was turned downwind to join the visual circuit for a simulated OEI landing. During the go-around, the unsafe landing gear warning alarm sounded at a manifold pressure level the instructor considered higher than normal, interfering with crew communication. The instructor pulled the circuit breaker for the warning system to silence the alarm, initially keeping a finger on the breaker as a reminder to reset it when downwind for landing.
On the downwind leg, air traffic control instructed the crew to orbit due to traffic on the ILS. Because of the orbit, the aircraft was farther from the runway than expected, so the crew delayed lowering the landing gear until assured of reaching the runway. The student’s workload was high, increasing the instructor’s monitoring workload. Neither pilot completed the prescribed pre-landing checks; the landing gear remained up and the warning system remained inhibited.
During the pre-touchdown flare, the instructor became aware of abnormal propeller contact with the runway and instinctively selected full power, initiating a successful go-around. During a subsequent visual circuit, the landing gear was selected down and indicated three green lights; a normal landing followed.
Aircraft Information
The PA34-220T is equipped with a landing gear warning system linked to microswitches in the throttle quadrant. The microswitches activate the warning horn when throttles are retarded to approximately 14 inches of mercury (MAP) or below, with a tolerance of ±2 in Hg, if the landing gear is not down and locked. The operator reported that G-ZZOT had maintenance on the MAP trigger level about eight months prior, but the system had been operating normally since. On the incident flight, the warning horn sounded at about 16 in Hg MAP.
Organizational Factors
The operator’s operations manual did not explicitly state a policy on pulling circuit breakers outside of approved abnormal procedure checklists. The operator normally expected pilots to pull circuit breakers only when required by a checklist. Following the incident, the operator intended to issue formal guidance that circuit breakers should only be pulled if specifically required when following an approved abnormal procedure checklist.
Analysis
The landing gear warning system appeared to be operating normally, albeit at the upper tolerance limit. The instructor considered the communication difficulty from the alarm to outweigh the risk of silencing it. He initially used a tactile reminder but later unconsciously removed his finger. The orbit and change in sequencing for lowering the gear were cited as distractions. Neither pilot completed the pre-landing checks, and the instructor did not detect that the action was missed.
Conclusion
The propellers struck the runway after an inadvertent gear-up approach. The warning system had been disabled by the instructor due to communication difficulties. Distraction was cited as a contributory factor for the instructor omitting to reset the circuit breaker and not positively confirming the landing gear was down. Had the warning system been active, it would have been more likely that the gear-up condition would have been detected.