ACR B-757 FLC EXPERIENCED ERRONEOUS VERT SPD MODE SELECTION WHILE COMPLYING WITH NOSE ABATEMENT PROCS. EXTREME PITCH-UP ATTITUDE RECOVERY ACCOMPLISHED. FLT DIVERTED; UNCERTAIN FLAP CONDITION.

Date: 1995-05 · Aircraft: B757-200

Anomalies: aircraft-equipment-problem-critical|other-unspecified

Synopsis

ACR B-757 FLC EXPERIENCED ERRONEOUS VERT SPD MODE SELECTION WHILE COMPLYING WITH NOSE ABATEMENT PROCS. EXTREME PITCH-UP ATTITUDE RECOVERY ACCOMPLISHED. FLT DIVERTED; UNCERTAIN FLAP CONDITION.

Narrative

SNA DEP; FO FLYING; LNAV SELECTED AT 400 FT; FLCH; V2 PLUS 15; R AUTOPLT ON AT 1000 FT. WHEN AUTOPLT WAS ENGAGED; ACFT PITCHED RAPIDLY UP; AND AIRSPD RAPIDLY DECREASED. NOSE ABATEMENT PROC CALLS FOR PITCH TO 21-25 DEGS. ACFT PITCHED WHEN AUTOPLT ENGAGED TO APPROX 30 DEGS. AS AIRSPD BLED BELOW V1; CAPT CALLED 'PUSH IT OVER.' BOTH CAPT AND FO PUSHED AGAINST AUTOPLT AND; DURING PUSHOVER; FO DISCONNECTED AUTOPLT . MOMENTARILY 'STICK SHAKER' AS ACFT NOSED OVER AND REGAINED SAFE FLYING SPD. FULL PWR WAS SIMULTANEOUSLY ADVANCED; AND GAR ENGAGED. AT 160 KTS; CAPT CALLED FOR CLEANUP. FLAPS WOULD NOT RETRACT AND LEADING EDGE SLATS ANNUNCIATED 'LE SL DISAGREE' ON EICAS. SLATS HAD EXTENDED FROM TKOF TO LAND POS AS RESULT OF STICK SHAKER (IMPENDING STALL) AND NOW DISAGREED WITH TRAILING EDGE FLAP POS. COMPLETED PROC FOR LEADING EDGE SLAT DISAGREE; MADE UNEVENTFUL LNDG AT LAX. REFLECTIONS AND RECOMMENDATION: FAA/NTSB SHOULD REVIEW SNA NOISE ABATEMENT REQUIREMENTS AND PROC. RESTRS REQUIRED ABNORMAL TKOF; CLB; AND DEP PROCS. REQUIREMENT PUTS ACFT CREW IN EXTREME CORNER OF ENVELOPE; AND SHOULD AN ABNORMAL SIT ARISE; YOU ARE ALREADY IN AN EXTREME POS AND ATTITUDE; AND IT BECOMES INTENSE QUICKLY. SECOND; ACR SHOULD REVIEW SNA DEP PROCS. THEY MAY VERY WELL BE CUMBERSOME AND DISTRACTING. CALLOUTS FOR MODE CTL PANEL; AUTOPLT; PASSING ALTS; DME; ETC; DISTRACT PNF FROM HIGHER PRIORITY TASKS SUCH AS FLYING AIRPLANE. IF AN ABNORMAL SIT ARISES DURING THIS PHASE; IT IS VERY DIFFICULT FOR BOTH PLTS TO STAY IN THE LOOP. IN SHORT; RETHINK AND TAILOR THE DEP PROC FOR THIS NOISE SENSITIVE ARPT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: RPTR'S CONCERNS TWOFOLD -- FIRST; THE NOISE ABATEMENT REQUIREMENT; AND COMPANY'S ASSOCIATED PROCS WERE A HAZARD TO SAFETY. SECOND; TAPES REVEALED VERT SPD SELECTION; RPTR SAYS; 'NO.' COMPANY PROCS ARE IN PROCESS OF REWRITE -- RPTR INVOLVED. NUMEROUS CALLOUTS (ALT AND DME) REQUIRED DIVERSION FROM MONITORING CTLING ACFT. THE DEP IS STILL AN ISSUE BECAUSE OP IS OFTEN ON THE EDGE; IN THE EVENT OF ANY COMPLICATION. SNA NOISE ABATEMENT COMPROMISES SAFETY FROM 'THE VERY BEGINNING; WHEN ONE FIRST STEPS INTO THE COCKPIT.' IT IS A PROCEDURAL; AND BRIEFING (10 ITEMS) BURDEN. FLC IS IN A HURRY-UP STATE; TRYING TO COMPLETE ALL TASKS; THEN CURFEW CAUSES GREATER PRESSURE. 'THE FLC IS SET-UP -- EVERYTHING IS IRREGULAR; MODE SELECTIONS; PITCH ATTITUDES; SPDS; AND PWR SELECTIONS ARE ENTIRELY UNUSUAL.' 'ON TKOF; THE ACFT LUNGES DOWN THE RWY; AND AN IMPROPERLY PERFORMED PITCH-UP COULD CAUSE A TAIL STRIKE.' IN THIS INCIDENT; 6 SECONDS AFTER 1000 FT PROCS WERE PERFORMED; THE VERT SPD MODE WAS TRACED AS SELECTED. SLOW SPD OBSERVED; AND WHILE RECOVERING ATTITUDE; CAPT HEARD STICK SHAKER. 'WE DID NOT HAVE THE SIT UNDER CTL UNTIL WE WERE JUST ABOUT TO TRM. WE DISAGREED ABOUT THE STICK SHAKER; SO THIS MEANT UNCERTAINTY OVER THE CAUSE OF THE LEADING EDGE SLAT EXTENSION. COMPANY PROC 'LEAVE FLAPS IN LAST KNOWN POS.' FLC RETURN LAND TO LAX; FOR MAINT; RWY LENGTH; AND SNA CURFEW PROBS. FLAP TRACKS WERE CHKED; AND MAINT PLACARDED R AUTOPLT 'INOP' (CAUSE WAS STILL; UNCERTAIN -- CHKS NORMAL); ACFT REFUELED; AND FLT DEPARTED TO SCHEDULED DEST. RPTR INSISTS THAT VERT SPD WAS NOT SELECTED BY EITHER FLT CREWMEMBER. HE IS POSITIVE THAT STICK SHAKER ACTIVATED; AND THIS EXPLAINS LEADING EDGE SLATS EXTENSION TO LNDG POS. COMPANY BULLETIN ISSUED 'ESTABLISH A NOSE- DOWN TREND' PRIOR TO SELECTION. SCENARIO WAS REBUILT IN SIMULATOR; AND INDICATED THAT ACFT WILL GO SLOW 5 OUT OF 12 TIMES.

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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.