CAA F50 at Beni on Aug 1st 2016, brakes problem

Last Update: April 20, 2020 / 21:52:17 GMT/Zulu time

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Incident Facts

Date of incident
Aug 1, 2016

Classification
Incident

Airline
CAA Compagnie Africaine Aviation

Flight number
BU-2511

Departure
Bunia, Democratic Republic of Congo

Destination
Beni, Democratic Republic of Congo

Aircraft Registration
9Q-CBL

Aircraft Type
Fokker 50

ICAO Type Designator
F50

A CAA Compagnie Africaine Aviation Fokker 50, registration 9Q-CBL performing flight BU-2511 from Bunia to Beni (DR Congo) with 23 passengers and 6 crew, landed on Beni's runway 29 when during the rollout the left main gear rotated causing the aircraft to veer left. The crew managed to stop the aircraft within the runway edges.

DR Congo's Bureau Permanent d’Enquêtes d’Accidents/Incidents d’Aviation (BPEA) reported the crew perceived a brakes problem causing the aircraft to veer left. The BPEA rated the occurrence a serious incident and opened an investiation. The DSB representing the state of manufacture joined the investigation to assist.

On Aug 15th 2017 the DSB released information in their quarterly bulletin stating the DR Congo's BPEA concluded the investigation on Jan 9th 2017.

The investigation reported that about 5nm before touchdown, when the landing gear was extended, an ANTI SKID FAULT message occurred. The crew continued the approach, set the flaps to 35 degrees in accordance with the checklist for not working anti skid systems. After touch down the first officer, pilot flying, had difficulties placing the power levers into ground idle. Due to the low deceleration the first officer therefore stepped into the pedal brakes, a few seconds both tyres at the left hand side burst. The aircraft came to a stop on the runway about 250 meters short of the runway end, the left main wheels were found tilted by 90 degrees. The occupants could disembark normally, there were no injuries.

DR Congo's BPEA released their final report in French dated Jan 9th 2017 (Editorial note: to serve the purpose of global prevention of the repeat of causes leading to an occurrence an additional timely release of all occurrence reports in the only world spanning aviation language English would be necessary, a French only release does not achieve this purpose as set by ICAO annex 13 and just forces many aviators to waste much more time and effort each in trying to understand the circumstances leading to the occurrence. Aviators operating internationally are required to read/speak English besides their local language, investigators need to be able to read/write/speak English to communicate with their counterparts all around the globe).

The final report concludes the probable causes of the incident were:

- poor application of aircraft maintenance procedures for the aircraft's electrical wires for the anti-skid sensors and sheath

- inability to select the propellers into ground idle preventing selection of reverse

- abrupt attempt to select mode "propeller ground idle stop" before or at touch down. Poor application of the procedure in the event of "propeller ground idle stop" being inop by the crew.

The BPEA analysed the flight was uneventful until final approach about 5nm before touchdown when the crew selected the gear down and received a gear down and locked indication followed by the "ANTI SKID INOP" indication. The crew reviewed the emergency procedure and decided to continue with the landing with the flaps at 35 degrees according to the ANTI SKID INOP procedure. Runway 29 had a length of 2000 meters, the first 300 meters however were unusable. At 17,000 kg landing mass Vref had been computed at 92 KIAS, the landing distance required with ANTI SKID INOP was 1680 meters. Upon touchdown or just before the first officer, pilot flying, attempted to select the propellers into ground idle stop, but failed, then advanced the lever again and tried another time, however, again without success. Seeing the remaining available runway ahead diminish with only about 250 meters remaining the first officer stepped into the brakes pedals which resulted in the left main tyres to burst and the main wheels to rotate by 90 degrees.

According to the AOM of the Fokker 50 the propeller ground idle stop will only operate when the gear struts signal weight on the wheels. The ground idle stop was probably selected prematurely.

The electrical cables for the anti skid sensor were cut because not being protected by the protective sheath (shield), following wear they came loose.

The report does not explain why the left main wheels rotated by 90 degrees.