Narrative:

We arrived at the aircraft at pdx approximately 10 mins prior to show time; so we were not rushed. 3 MEL's were listed for the airplane (APU inoperative; automatic pressure controller inoperative; and #2 DME inoperative). I began my first officer preflight while the captain did his preflight and reviewed the paperwork (logbook; releases; etc). Prior to engine start; the captain and I did discuss the start procedures with an APU inoperative (we even referenced the QRH bleed air diagram since neither of us had done this type of start in quite a while); and quickly mentioned that the pressurization system should work ok in 'altn;' and that the #2 DME was inoperative; but didn't look into the opc MEL pages for those items. The flight plan had us filed as a '/J;' basically meaning no restrs for the route that was filed. Once we were airborne; the captain looked at the MEL for any amplifying data about our #2 DME MEL and found there was a note 'RNAV not permitted.' I was the PF with the #2 autoplt engaged in LNAV; flying the route between pdx and sjc. As far as we could tell; the aircraft was staying on course (rnp on the legs page of the FMC was staying at about 0.23); and we had no calls from sea or ZOA about any course deviations (there are no backup navaids for this routing). The captain referenced his fom to see what the guidance was about RNAV versus LNAV (were they the same? Should we really be flying in LNAV with the #2 DME inoperative?) and it really wasn't clear to either of us. We continued on our routing; with the autoplt engaged in LNAV until we received vectored for our approach. On the ground in sjc; the captain talked to dispatch and maintenance control and we continued to our next city without using LNAV (received headings to vors along the route) since we were now downgraded to a '/west.' maintenance personnel then returned the #2 DME to a normal operations. As the first officer; I need to be more proactive in checking all the amplifying data about all the MEL's we're carrying. The captain I flew with was very conscientious; and we did have good crew communication; but each person can become 'channelized' and I shouldn't have assumed he had received all the information from the dispatch release we needed. There should be some type of a caution note on the flight release for any restrs the aircraft has with a navigation equipment like we encountered (ie; 'LNAV/RNAV not authority/authorized for this flight until #2 DME MEL cleared.').

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Original NASA ASRS Text

Title: B737 CREW FLIES COMPANY FILED RNAV RTE PROHIBITED BY MEL.

Narrative: WE ARRIVED AT THE ACFT AT PDX APPROX 10 MINS PRIOR TO SHOW TIME; SO WE WERE NOT RUSHED. 3 MEL'S WERE LISTED FOR THE AIRPLANE (APU INOP; AUTO PRESSURE CONTROLLER INOP; AND #2 DME INOP). I BEGAN MY FO PREFLT WHILE THE CAPT DID HIS PREFLT AND REVIEWED THE PAPERWORK (LOGBOOK; RELEASES; ETC). PRIOR TO ENG START; THE CAPT AND I DID DISCUSS THE START PROCS WITH AN APU INOP (WE EVEN REFED THE QRH BLEED AIR DIAGRAM SINCE NEITHER OF US HAD DONE THIS TYPE OF START IN QUITE A WHILE); AND QUICKLY MENTIONED THAT THE PRESSURIZATION SYS SHOULD WORK OK IN 'ALTN;' AND THAT THE #2 DME WAS INOP; BUT DIDN'T LOOK INTO THE OPC MEL PAGES FOR THOSE ITEMS. THE FLT PLAN HAD US FILED AS A '/J;' BASICALLY MEANING NO RESTRS FOR THE RTE THAT WAS FILED. ONCE WE WERE AIRBORNE; THE CAPT LOOKED AT THE MEL FOR ANY AMPLIFYING DATA ABOUT OUR #2 DME MEL AND FOUND THERE WAS A NOTE 'RNAV NOT PERMITTED.' I WAS THE PF WITH THE #2 AUTOPLT ENGAGED IN LNAV; FLYING THE RTE BTWN PDX AND SJC. AS FAR AS WE COULD TELL; THE ACFT WAS STAYING ON COURSE (RNP ON THE LEGS PAGE OF THE FMC WAS STAYING AT ABOUT 0.23); AND WE HAD NO CALLS FROM SEA OR ZOA ABOUT ANY COURSE DEVS (THERE ARE NO BACKUP NAVAIDS FOR THIS ROUTING). THE CAPT REFED HIS FOM TO SEE WHAT THE GUIDANCE WAS ABOUT RNAV VERSUS LNAV (WERE THEY THE SAME? SHOULD WE REALLY BE FLYING IN LNAV WITH THE #2 DME INOP?) AND IT REALLY WASN'T CLR TO EITHER OF US. WE CONTINUED ON OUR ROUTING; WITH THE AUTOPLT ENGAGED IN LNAV UNTIL WE RECEIVED VECTORED FOR OUR APCH. ON THE GND IN SJC; THE CAPT TALKED TO DISPATCH AND MAINT CTL AND WE CONTINUED TO OUR NEXT CITY WITHOUT USING LNAV (RECEIVED HDGS TO VORS ALONG THE RTE) SINCE WE WERE NOW DOWNGRADED TO A '/W.' MAINT PERSONNEL THEN RETURNED THE #2 DME TO A NORMAL OPS. AS THE FO; I NEED TO BE MORE PROACTIVE IN CHKING ALL THE AMPLIFYING DATA ABOUT ALL THE MEL'S WE'RE CARRYING. THE CAPT I FLEW WITH WAS VERY CONSCIENTIOUS; AND WE DID HAVE GOOD CREW COM; BUT EACH PERSON CAN BECOME 'CHANNELIZED' AND I SHOULDN'T HAVE ASSUMED HE HAD RECEIVED ALL THE INFO FROM THE DISPATCH RELEASE WE NEEDED. THERE SHOULD BE SOME TYPE OF A CAUTION NOTE ON THE FLT RELEASE FOR ANY RESTRS THE ACFT HAS WITH A NAV EQUIP LIKE WE ENCOUNTERED (IE; 'LNAV/RNAV NOT AUTH FOR THIS FLT UNTIL #2 DME MEL CLRED.').

Data retrieved from NASA's ASRS site as of January 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.