Date & Time: Nov 1, 2011 at 1439 LT
Type of aircraft:
Boeing 767-300
Operator:
Registration:
SP-LPC
Survivors:
Yes
Schedule:
Newark - Warsaw
MSN:
28656/659
YOM:
1997
Flight number:
LOT016
Country:
Poland
Region:
Europe
Crew on board:
10
Crew fatalities:
0
Pax on board:
221
Pax fatalities:
0
Other fatalities:
0
Total fatalities:
0
Captain / Total flying hours:
15980
Captain / Total hours on type:
13307
Copilot / Total flying hours:
9431
Copilot / Total hours on type:
1981
Aircraft flight hours:
85429
Aircraft flight cycles:
8002
Circumstances:
Thirty minutes after departure from Newark, crew informed their base in Warsaw that the central hydraulic system failed (hydraulic system C). On approach to Warsaw, crew completed the landing checklist but was unable to lower the gear. At 3,000 feet on approach, captain decided to abandon the descent and made a go around . During an 80 minutes holding circuit over Warsaw, a fighter pilot confirmed that all gear were not deployed and despite several troubleshooting, crew was unable to lower the gear. Eventually, it was decided to make a belly landing on runway 33. Following an uneventful approach, aircraft landed smoothly and skidded on runway, creating several sparks before coming to rest at 1439LT. All 231 occupants were evacuated safely and the company decided later that the aircraft was not repairable.
Probable cause:
The cause of the hydraulic leak and resulting failure was caused by the fracture of a flexible hydraulic hose connecting the brakes system of the right main gear with hydraulic system C. The fracture occurred in the area of a metal band around the tip of the hose. The nature of the crack suggests there was a stress relaxation resulting in material creep. The inner Kevlar lining of the pressure sleeve had signs of abrasions which according to the manufacturer suggests the hose had been repeatedly flexing as result of pressure changes, so that the manufacturer suspects the hose was not installed completely straight.
The hydraulic fluid was found to meet required specifications.
Following comparison of the alternate landing gear system with another aircraft with the circuit breaker C829 in both off and on positions, it was found that the alternate landing gear sequence would extend the gear with the circuit breaker in the on position, however, would not operate if the circuit breaker was in the off position.
The actuator was found operative.
The C829 circuit breaker was confirmed to not be indicated on the engine indications and crew alerting system (EICAS) and was not recorded by the black boxes.
Documentation (checklists) would turn attention towards that circuit breaker only if systems protected by the circuit breaker needed to be activated.
The checklist for loss of pressure in the central hydraulic system did not refer to the circuit breaker C829 leaving the crew without guidance if the first item to activate the alternate gear extension switch did not illuminate the "gear down" lights. The checklist did not include the possibility of the alternate gear extension failing at all.
The checklist for gear disagree also did not include the possibility of a failed alternate gear extension.
There was no checklist available at all in case of both primary and alternate gear extension had failed, e.g. a all gear up landing checklist.
Based on current technical evidence the investigation thus may conclude that the cause of the belly landing was the circuit breaker C829 in the off position. A separate issue will be to find out why the circuit breaker was off.

Source: AvHerald
Final Report:
SP-LPC.pdf13.83 MB