FAR 121, Appendix M FDR parameters
FAR 121, App. M, Item #43. Additional engine parameters:
There are several parameters such as vibration level, N2, EGT, Fuel flow, N3 and:
Fuel cut-off lever position. Is this the only parameter that is recorded to determine spar valve position? FAR 121, App. M does not mention any (required) parameters for recording spar valve position other than fuel cut-off lever position.
If the premise is that spar valve control has been tested and could not be demonstrated to fail under any condition, would the tests (investigating BA38) have been a duplication of tests performed during certifiation of the control system? If so, would there have been a reason to add any FDR parameters other than the required fuel cut-off lever position to determine spar valve position if the system was tested as fool-proof during certification?
The AAIB state: "Any uncommanded movement would have been recorded on the FDR and warnings would have been enunciated on the flight deck."
FAR 121, App. M only mentions the fuel cut-off lever position as a required recorded parameter, does this mean that any additional parameter must have been added by the manufacturer or as a JAR-OPS requirement? After checking JAR-OPS 1.715 table A1, table B and table C, applicable to the 777, I could not find any such requirement.
Referring to warning enunciation on the flight deck regarding spar valve position. The warning I am aware of is presented only when there is a disagree between the spar valve control relay position and spar valve actuator position as a result of a jammed actuator. According to the AMM/SDS, OPAS monitors control relay position and valve (actuator) position. As long as the spar valve actuator follows control relay position, there is no warning (no status message on EICAS). Even if for whatever (very remote) condition the control relay would move from open to closed position uncommanded with fuel cut-off lever in the run position. As long as the valve actuator follows control relay command there will be no warning presented on the flight deck because OPAS does not sense a disagree between these two components, hence, sends no fault message to AIMS. OPAS does not monitor a disagree between fuel cut-off lever position and spar valve actuator position.
Spar valve position can be displayed to the crew, but only if the crew selects the fuel synoptic or maintenance pages. Neither are likely to be selected during an approach phase unless there is a specific reason to do so.
It would have been interesting if the FDR parameters (and which parameters) for the spar valve positions were included in figure 2 of the interim report. Perhaps they will be included in the final report.
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