Narrative:

I write this report to bring attention to an irregular procedures checklist used by my airline for the B757/767 fleet that I believe may be inadequate. The actual boeing checklist is nearly identical; verbatim. Still; I remain concerned that neither checklist addressed the problem adequately. A recommendation to fix the checklist will be provided at the end of this report. But; first; I must explain why I take issue with the procedure in question. The procedure is entitled; 'standby bus off.' it is short. (I apologize that this report will be much longer than the checklist itself; but I must detail my concerns adequately.) my assumptions and conclusions are derived from the information given in air carrier's flight manual. My concern rests in not knowing one major detail: will the battery charger automatically reconnect the battery and its associated busses (hot battery bus; battery bus; standby AC and standby dc) to the main busses when the battery dies? The answer to that question is not clear in our manuals; but the checklist itself seems to imply that the answer is no. If the answer is no; then my report is valid. I am concerned that a pilot will read this checklist; accomplish it; and not pursue the ramifications of following it without further analysis. I am equally concerned that a pilot will read the checklist; accomplish it; and then begin to research what effect his actions will ultimately have; and find out too late he has crippled his airplane and limited his options. When the pilot accomplishes the first step; and takes the standby power selector to battery; he has disconnected the battery charger. The caution in the procedure mentions that. What the checklist fails to mention is what will happen when that battery; now being discharged to power not only the standby busses; but now also the hot battery bus and the battery bus; dies. The battery may take anywhere up to 30 mins to fail; but it will fail. At the point of battery failure; the pilot will lose all items on the hot battery bus; the battery bus; and both standby busses (even if only one was defective before). Because the battery is required to power the battery and standby power control panel; I presume the dead battery will no longer allow reselection of the automatic position. Does this mean there is no longer any way to reconnect the battery charger to the battery? It really doesn't matter that the engines are turning; the generators are fine; and all is well in the main AC/dc system. The problem is the pilot disconnected his most vital system from main aircraft power to power them via the battery; and apparently has no way to reconnect them once the battery dies. A cursory look at the busses involved shows me that the airplane is now critically diminished; operationally.

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Original NASA ASRS Text

Title: B757 FO QUESTIONS THE QRH PROCEDURES AND CAUTIONS FOR STANDBY POWER OFF LIGHT.

Narrative: I WRITE THIS REPORT TO BRING ATTN TO AN IRREGULAR PROCS CHKLIST USED BY MY AIRLINE FOR THE B757/767 FLEET THAT I BELIEVE MAY BE INADEQUATE. THE ACTUAL BOEING CHKLIST IS NEARLY IDENTICAL; VERBATIM. STILL; I REMAIN CONCERNED THAT NEITHER CHKLIST ADDRESSED THE PROB ADEQUATELY. A RECOMMENDATION TO FIX THE CHKLIST WILL BE PROVIDED AT THE END OF THIS REPORT. BUT; FIRST; I MUST EXPLAIN WHY I TAKE ISSUE WITH THE PROC IN QUESTION. THE PROC IS ENTITLED; 'STANDBY BUS OFF.' IT IS SHORT. (I APOLOGIZE THAT THIS REPORT WILL BE MUCH LONGER THAN THE CHKLIST ITSELF; BUT I MUST DETAIL MY CONCERNS ADEQUATELY.) MY ASSUMPTIONS AND CONCLUSIONS ARE DERIVED FROM THE INFO GIVEN IN ACR'S FLT MANUAL. MY CONCERN RESTS IN NOT KNOWING ONE MAJOR DETAIL: WILL THE BATTERY CHARGER AUTOMATICALLY RECONNECT THE BATTERY AND ITS ASSOCIATED BUSSES (HOT BATTERY BUS; BATTERY BUS; STANDBY AC AND STANDBY DC) TO THE MAIN BUSSES WHEN THE BATTERY DIES? THE ANSWER TO THAT QUESTION IS NOT CLR IN OUR MANUALS; BUT THE CHKLIST ITSELF SEEMS TO IMPLY THAT THE ANSWER IS NO. IF THE ANSWER IS NO; THEN MY REPORT IS VALID. I AM CONCERNED THAT A PLT WILL READ THIS CHKLIST; ACCOMPLISH IT; AND NOT PURSUE THE RAMIFICATIONS OF FOLLOWING IT WITHOUT FURTHER ANALYSIS. I AM EQUALLY CONCERNED THAT A PLT WILL READ THE CHKLIST; ACCOMPLISH IT; AND THEN BEGIN TO RESEARCH WHAT EFFECT HIS ACTIONS WILL ULTIMATELY HAVE; AND FIND OUT TOO LATE HE HAS CRIPPLED HIS AIRPLANE AND LIMITED HIS OPTIONS. WHEN THE PLT ACCOMPLISHES THE FIRST STEP; AND TAKES THE STANDBY PWR SELECTOR TO BATTERY; HE HAS DISCONNECTED THE BATTERY CHARGER. THE CAUTION IN THE PROC MENTIONS THAT. WHAT THE CHKLIST FAILS TO MENTION IS WHAT WILL HAPPEN WHEN THAT BATTERY; NOW BEING DISCHARGED TO PWR NOT ONLY THE STANDBY BUSSES; BUT NOW ALSO THE HOT BATTERY BUS AND THE BATTERY BUS; DIES. THE BATTERY MAY TAKE ANYWHERE UP TO 30 MINS TO FAIL; BUT IT WILL FAIL. AT THE POINT OF BATTERY FAILURE; THE PLT WILL LOSE ALL ITEMS ON THE HOT BATTERY BUS; THE BATTERY BUS; AND BOTH STANDBY BUSSES (EVEN IF ONLY ONE WAS DEFECTIVE BEFORE). BECAUSE THE BATTERY IS REQUIRED TO PWR THE BATTERY AND STANDBY PWR CTL PANEL; I PRESUME THE DEAD BATTERY WILL NO LONGER ALLOW RESELECTION OF THE AUTO POS. DOES THIS MEAN THERE IS NO LONGER ANY WAY TO RECONNECT THE BATTERY CHARGER TO THE BATTERY? IT REALLY DOESN'T MATTER THAT THE ENGS ARE TURNING; THE GENERATORS ARE FINE; AND ALL IS WELL IN THE MAIN AC/DC SYS. THE PROB IS THE PLT DISCONNECTED HIS MOST VITAL SYS FROM MAIN ACFT PWR TO PWR THEM VIA THE BATTERY; AND APPARENTLY HAS NO WAY TO RECONNECT THEM ONCE THE BATTERY DIES. A CURSORY LOOK AT THE BUSSES INVOLVED SHOWS ME THAT THE AIRPLANE IS NOW CRITICALLY DIMINISHED; OPERATIONALLY.

Data retrieved from NASA's ASRS site as of May 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.