Incident Overview
On 17 February 2025, the crew of a Tecnam P2006T aircraft, registration SP-SUT, was performing a training flight for a professional licence. At approximately 9:52 a.m. local time, while flying over Gliwice, the right engine began to malfunction. The crew observed unstable readings on the right engine tachometer, which showed alternating dips and rises.
Decision to Return
The instructor decided to turn back towards EPGL airport and prepare for landing. During the approach, after the flight was stabilised, the instrument readings returned to normal. The instructor then changed the decision and aborted the approach, intending to continue with the originally planned task of familiarisation flight in the vicinity of the airport. However, during the climb at around 9:57 a.m., unstable right engine RPM readings occurred again. Additionally, the crew noticed that the fuel gauge of the right tank was showing zero. The instructor again decided to abort the task and return to EPGL.
Emergency Landing
At 10:03 a.m., the crew informed the AFIS officer of EPGL airport that they needed to land immediately. The AFIS advised that runway 08R was available. The flight crew reported the emergency without requesting assistance from emergency services. During the landing approach, the right engine was idling, in accordance with the emergency procedures in the Airplane Flight Manual (AFM) for the Tecnam P2006T. The left engine functioned normally. The landing took place at 10:06 a.m. with no repercussions.
Aircraft and Engine Details
The Tecnam P2006T is powered by two Rotax 912 S3-01 engines with carburettor fuel supply. At the time of the occurrence, the total operating time since new (TSN) was 1,197 hours for the left engine and 1,209 hours for the right engine. The airframe had a total of 1,141 flight hours. The engines were factory-installed and had not been replaced. The last maintenance at the 100 flight hour level was carried out on 14 November 2024 at 1,101 flight hours, with 59 flight hours remaining for the next inspection. The aircraft was fuelled with automotive 98-octane petrol, which was used regularly by the user.
Findings
Post-occurrence visual inspection revealed a burned-out exhaust valve of the right-engine cylinder no. 2. Additionally, the fuel level sensor of the right tank was found to be malfunctioning, causing erroneous readings of the fuel gauge. This fault was not linked to the engine malfunction; the tank was filled with fuel during the flight.
Causes and Contributing Factors
The investigation determined that the unstable operation of the engine was caused by pressure fluctuations in cylinder no. 2, which occurred after the exhaust valve had burned out. Presumably, this fault was due to exhaust gas temperature (EGT) being too high during engine operation. The operation of the valves under such conditions led to excessive oxidation of the valve material and ultimately to valve burnout. As there was no EGT monitoring sensor, the crews operating the aircraft were unable to control the performance of the power unit in an optimal manner.
Preventive Actions
The investigator implemented the following actions: replacement of the exhaust and intake valves in the head of the right-engine cylinder no. 2; replacement of the fuel level sensor for the fuel gauge on the right tank; instruction to the maintenance organization to carefully monitor the level of carbon deposits in the cylinders, including inspection of valve condition during scheduled maintenance; and verification of the condition of the valves on the left engine (which were not damaged).
Commission's Comments
The occurrence is one of a number of engine valve burnouts on Tecnam P2006T aircraft. Rotax recorded 13 reports of such incidents on this type over the past five years, with various identified reasons. The Commission noted the trend of faults during operation of Rotax engines on Tecnam P2006T aircraft used in training, particularly for multi-engine training. Intensive operation of heavily loaded power units, combined with engine installation conditions, generates variable and high thermal stresses in the valve systems. The aircraft manufacturer has made some modifications, and the engine manufacturer introduced sodium-filled valves. The Commission drew attention to the need for constant monitoring of the operation and technical condition of Rotax 912 engines on Tecnam P2006T aircraft. It also criticized the instructor's decision to abort the approach and continue flying without identifying the cause of the engine malfunction, stating it was premature and not supported by good practice.
Safety Recommendations
No safety recommendations were formulated.