What happened
On March 11, 1998, a Cessna 425 (registration D-ICHS) operating a charter flight from Hannover landed at Helsinki-Vantaa Airport. During taxiing following the landing on runway 22, the pilot identified a malfunction in the right brake of the nose gear. After informing air traffic control, the pilot determined that the aircraft could continue taxiing by utilizing propeller reverse thrust to assist with deceleration.
To guide the aircraft to the Business Flight Center (BFC) parking area, a 'Follow Me' vehicle was dispatched. The pilot followed the vehicle along taxiways Oskar and 2. As the vehicle approached the designated parking stand, the driver stopped the vehicle and exited to provide manual hand signals. However, the aircraft continued toward the vehicle at a high rate of speed. As the aircraft attempted to turn left to avoid the vehicle, the right wingtip struck the light bar mounted on the roof of the 'Follow Me' car.
The collision caused damage to the aircraft's wingtip, including the leading edge and the de-icing boot, though the fuel tank remained intact. The vehicle sustained damage to its roof, light bar, and mounting hardware.
The investigation
The investigation examined the communication between the pilot, air traffic control, and the vehicle driver, as well as the mechanical state of the aircraft. It was established that the pilot had reported the brake failure to air traffic control, and the controller had confirmed the aircraft's ability to taxi. However, the controller did not explicitly relay the brake malfunction to the 'Follow Me' driver, assuming the driver had overheard the radio exchange.
The investigation also reviewed the driver's radio monitoring. While the driver monitored several frequencies, including the apron and vehicle channels, the specific frequency used for the conversation between the pilot and the tower (118.60 MHz) was not being monitored by the driver at that time.
Findings
- The primary cause of the accident was the excessive taxi speed maintained by the pilot while operating an aircraft with impaired braking capability.
- The pilot failed to utilize the available space and maneuvering options, such as nose-wheel steering or early use of reverse thrust, to slow the aircraft before reaching the vehicle.
- The pilot operated under the unverified assumption that the 'Follow Me' driver was aware of the brake malfunction.
- Air traffic control did not explicitly inform the vehicle driver of the mechanical issue, and the controller did not verify if the driver had understood the situation.
- The brake failure was caused by a faulty tire valve, which led to a fluid leak in the right nose gear brake.