A B737-700 AT FL390 EXPERIENCED MODERATE MOUNTAIN WAVE ACTION WITH MACH/AIRSPEED DEV EXCEEDING VMO/MMO LIMITS AND REQUIRING INSPECTIONS.

Narrative

WE WERE AWARE OF THE TURB FORECAST AREA NEAR THE MOUNTAINS BY DEN; AND THAT WE MAY BE TRANSITING THE LOWER CORNER OF IT ENRTE ZZZ1. WE WERE FLYING ECON CRUISE OF MACH .78 AT FL390 (BECAUSE OF WT; ALTHOUGH DISPATCHED AT FL410). AS WE APCHED; ATC QUERIES AND RPTS INDICATED ONLY LIGHT CHOP/TURB WITH ATC; STATING IT EXISTED UP TO FL380 AND LASTING ONLY A FEW MINS FOR E/W TRAVEL. SO; IT APPEARED ONLY 'LIGHT' AND BELOW US. AS WE APCHED SLIGHTLY NW OF SANTA FE; NM; THE LIGHT CHOP BEGAN AS THE SEATBELT SIGN WAS PUT BACK ON. IT STARTED TO WORSEN SO I SAT THE FLT ATTENDANTS DOWN. THE CHOP DID INDEED WORSEN EVEN MORE SHORTLY THEREAFTER. WITHIN A MIN OR SO; THE LIGHT CHOP SUDDENLY AND INSTANTANEOUSLY TURNED INTO MODERATE TURB WITH SOME MOUNTAIN WAVE ACTION. AS I STARTED TO PULL PWR TO SLOW TO MACH .76; THE AIRSPD LITERALLY JUMPED TO MACH .82 WITH CLACKER IN ABOUT 2 SECONDS. I WAS STUNNED AT HOW QUICKLY THIS HAPPENED WITH ONLY 'LIGHT CHOP' CONDITIONS REPORTED AT ALTS BELOW US ONLY. I HAD TO FURTHER PULL POWER ALL THE WAY TO IDLE WITH THE SPEED CONTINUING UPWARD TO MACH .84 WHERE IT STAYED FOR ABOUT 10 SECONDS (WHILE AT IDLE)! THE SPD THEN SLOWLY DISSIPATED OVER THE NEXT 15 SECONDS OR SO AS I GRADUALLY ADDED PWR TO INTERCEPT MACH .76. WITHIN THE NEXT MIN OR TWO; THE ROUGH RIDE WENT BACK TO LIGHT CHOP; THEN SMOOTH UNTIL; AMAZINGLY; ABOUT 20 MINS LATER; APCHING ABEAM AMA; SOME SLIGHT MOUNTAIN WAVE WAS AGAIN ENCOUNTERED FOR A COUPLE OF MINS! AFTER THE ENCOUNTER; WE LOOKED IN THE FOM TO SEE IF REACHING VMO +20 KTS OR MMO +.02 MACH (DESIGN LIMIT SPDS OF 340 KTS; MACH .84) REQUIRED A LOGBOOK WRITE-UP AND MAINT INSPECTION (I THOUGHT THAT THEY DID WITH RECENT EMPHASIS ON THE FACT FROM FLT OPS). I WAS ALSO UNSURE OF THE POTENTIAL MAINT INSPECTION TIMELINE REQUIREMENTS (IE; IMMEDIATE; OR WITHIN A CERTAIN NUMBER OF DAYS; OR... ETC). THIS MAINT INSPECTION REQUIREMENT KNOWLEDGE TURNS OUT TO BE A CRITICAL CUSTOMER SVC ISSUE INBOUND TO A STATION AFTER EVEN ONLY TOUCHING DESIGN LIMIT SPDS (ALSO FOR FLAP OVERSPDS). WE FOUND AN FOM APPENDIX PAGE THAT TALKS ABOUT 'UNSCHEDULED MAINT CHKS...EXCEEDING DESIGN SPD (VMO +20 KTS OR MMO +.02 MACH).' SINCE WE DID NOT 'EXCEED' THE DESIGN SPD; BUT ONLY 'REACHED' IT; THOSE WORDS CONVINCED US THAT NO MAINT ACTION OR INSPECTION DELAY WOULD BE EXPECTED REACHING DEST. WE KNEW A MECH WOULD BE THERE TO CONFIRM OUR ASSUMPTION ALSO. IT WAS NOT UNTIL AFTER TALKING TO MAINT CTL ON LNDG; AND THEIR GNDING OF THE ACFT FOR INSPECTION (APPROX 1-2 HRS) THAT I DISCOVERED THIS IN THE FOM ON THE PREVIOUS PAGES. THE FOM APPENDIX TALKS ABOUT 'ITEMS THAT REQUIRE GUIDANCE FROM MAINT CTL' BUT ONLY AN 'INFO' WRITE-UP: OPERATIONAL EXCEEDANCES THAT DO NOT REQUIRE MAINT INSPECTION: 1) VMO EXCEEDANCE OF LESS THAN 20 KTS. 2) MMO EXCEEDANCE OF LESS THAN .02 MACH. THIS IS; APPARENTLY; CORRECTLY WORDED REGARDING REAL WORLD OPS. HOWEVER; IT CONTRADICTS THE FOM PAGE GUIDANCE THAT ONE MUST 'EXCEED' DESIGN LIMIT SPD TO ACTUALLY TRIGGER THE INSPECTION REQUIREMENT (IE; 361 KTS; MACH .85 ). BECAUSE OF OUR CONFUSION IN THINKING NO INSPECTION WAS REQUIRED; PAX WERE ALREADY BOARDING AS WE GOT THE NEWS FROM MAINT CTL THAT THE ACFT REQUIRED AN INSPECTION WHICH COULD TAKE A COUPLE OF HRS. SINCE WE WERE A COUPLE OF HRS FROM DEST WHEN THE OVERSPD OCCURRED; WE COULD HAVE INFORMED DISPATCH VIA ACARS OF THE EVENT AND INSPECTION REQUIREMENTS WELL AHEAD OF TIME FOR OTHER ARRANGEMENTS AND ACFT SWAP PLANNING TO BE DONE TO INCONVENIENCE OUR PAX THE LEAST. THEREFORE; I BELIEVE THAT THE FOLLOWING CHANGES NEED TO BE MADE TO THE FOM: 1) THE PAGE SHOULD READ; 'REACHING AND/OR EXCEEDING DESIGN LIMITS SPDS OF 360 KTS; MACH .84 (VMO +20/MMO +.02). 2) THE FOM LIMITATIONS SHOULD INCLUDE; SOMEWHERE; THE DEFINITION OF 'DESIGN LIMIT SPD' AND THEN STATE THAT REACHING AND/OR EXCEEDING THOSE SPDS 'REQUIRE' GNDING OF THE ACFT AT DEST FOR A MAINT INSPECTION (POSSIBLY A COUPLE OF HRS); SO CONTACT DISPATCH AND/OR STATION OPS ASAP OF THE OVERSPD SO THAT PAX AND ACFT SWAP PLANNING CAN COMMENCE. (THE SAME IS TRUE FOR FLAP SPD EXCEEDANCES). ALSO; WHY NOT BLATANTLY STATE THAT MAX OPERATING SPDS; VMO/MMO (CLACKER) ARE 340 KIAS; MACH .82; THERE ALSO?