December 1, 2011
The Polish State Commission for Investigation of Air Accidents released an initial investigation report detailing the gear-up landing of a LOT Polish Airlines Boeing 767 on November 1.
The airplane operated on a regular passenger flight from Newark (EWR), USA to Warsaw (WAW), Poland. After take off, while retracting the landing gear and flaps hydraulic fluid began to leak from the central hydraulic system (installation “C”), what consequently led to pressure drop in this installation. After completing the QRH procedure and consultation with the operator’s operations centre, the flight crew decided to continue the flight to Warsaw.
During approach for landing at Warsaw the flight crew performed the QRH procedure which was connected with using the alternate landing gear extension system. The landing gear did not come down. A holding pattern was entered while the crew tried to lower the gear in the gravitational way, which was also unsuccessful. A Polish Air Force F-16 fighter flew by and confirmed the gear was up. Because the airplane was getting low on fuel, a safe emergency gear-up landing was carried out.
Initial investigation results indicate that on the P6 panel on the flight deck, the circuit breaker C829 BAT BUS DISTR (on A1 position) was in the position „Off”, while the circuit breaker C4248 LANDING GEAR – ALTN EXT MOTOR (on F6 position) was in the position „On”.
The circuit breaker C829 (BAT BUS DISTR) indicated on Photo 5 protects several airplane systems including the alternate landing gear extension system. The „Off” position of the circuit breaker was not recorded or indicated by the airplane systems (FDR – Flight Data Recorder and EICAS – Engine Indications and Crew Alerting System).
After connecting the ground power unit, setting C829 (A1) BAT BUS DISTR circuit breaker in the position „On” and activation of the alternate landing gear extension system, the landing gear was extended and the airplane was recovered.
April 15, 2011
TSB Canada published the final report of their investigation into an occurrence involving a LOT Polish Airlines Boeing 767-300, June 2009. Erroneous instrument indications resulted in airspeed and altitude deviations.
The LOT Polish Airlines Boeing 767-300 (registration SP-LPA) operating as LOT 2 departed from Chicago-O’Hare International Airport (ORD) and was destined for Warsaw (WAW), Poland. At 22:03 Eastern Daylight Time, while the aircraft was in level cruise flight in the vicinity of North Bay, Ontario, Canada the captain’s airspeed indicator suddenly increased above the maximum operating speed, and an overspeed warning was triggered. The flight crew reduced thrust to flight idle and initiated a climb. As the aircraft slowed, the overspeed warning stopped. The flight crew maintained the nose-up attitude with the reduced thrust setting but the captain’s indicated airspeed suddenly increased again, causing a second overspeed warning. As the flight crew reacted to the second overspeed warning, a simultaneous activation of the stick shaker occurred. During the incident the aircraft climbed from 33 000 to 35 400 feet above sea level (asl) and then descended to approximately 27 900 feet asl. The crew diverted to the Toronto/Lester B. Pearson International Airport where the aircraft landed safely. There was no damage to the aircraft and none of the 10 crew members and 206 passengers were injured.
Findings as to causes and contributing factors:
- There was a fault within the phase locked loop (PLL) circuitry of the ADC which resulted in sudden and erroneous airspeed and altitude indications on the captain’s instruments.
- The readings on the captain’s instruments were not compared to those on the first officer’s or the standby instruments. Consequently, the crew believed the captain’s instruments to be correct and made control inputs that resulted in significant altitude and airspeed deviations.
Findings as to risk:
- LOT Polish Airlines initial and recurrent flight training syllabus does not include practical training for an overspeed warning event. Consequently, flight crews may respond improperly and exacerbate the situation.
- Although revision 5 of the Boeing SB 767-34A0332 requires changes to chapters of the FCOM, it does not specify what the changes should be. Therefore some manuals may not be properly amended, thereby increasing the risk of crews being ill-informed of the status of the aircraft they operate.
- The LOT Polish Airlines FCOM incorrectly states that the IAS DISAGREE and ALT DISAGREE EICAS messages will not be displayed on the occurrence aircraft during an unreliable airspeed incident. This increases the risk of a crew misidentifying a problem.
- The installation of CVRs with less than 2 hours of recording capacity creates the risk that relevant information will not be available to accident investigators and that significant safety issues may not be identified.
- During the initial examination and disassembly of the ADC, it was noted that there was a large build-up of dust and dirt inside the unit, which could cause an increase in the internal temperature.
In the hold, with thrust at idle, the flight crew did not monitor the airspeed. In an attempt to maintain altitude, the autopilot increased the angle of attack until the stick shaker activated. During the recovery, the crew allowed the aircraft to climb through the flight’s cleared altitude, resulting in a loss of separation.