Narrative:

Opinion on RNAV. Flying the RNAV arrival skebr 1 for runway 25L into las, we had a couple of modifications to the constraints depicted on the arrival and a couple of controllers' directives that left us in doubt as to what the controllers wanted from us. Individually, the modifications were small and easily complied with. Collectively, they led to ambiguous intentions, deviation from standard cockpit management and increased radio xmissions for clarification. Prior to being handed over to las approach, center cleared us to descend via skebr 1 runway 25L, except 9000 ft at povoc. Checking in with las approach I stated 'descending via skebr 1 runway 25L, povoc at 9000 ft.' approach corrected me by saying that we were cleared 'skebr 1 for runway 25L.' I asked approach if that meant they wanted me to comply with the speeds and altitudes, except povoc at 9000 ft, depicted on the chart. Answer: yes. Prior to ipuny, we were told to slow to 220 KTS. No directions given reference the speed at povoc. Approaching povoc, I asked if they wanted the depicted 210 KTS or the previously issued 220 KTS. Answer: 210 KTS. Prior to povoc, we were switched to another approach controller. Checking in at 9000 ft, we were directed to 'slow to 170 KTS at 8000 ft, lower in 2 mins.' as no reference was given to leaving 9000 ft (either at povoc or in 2 mins), I had to ask if we were cleared out of 9000 ft. Answer (sounding irritated): yes, at povoc cleared to 8000 ft, slow to 170 KTS reaching.' with 3 more heading/altitude/speed controller requests, we were on an 8 mi final and switching over to tower. The previous day, the landing runway was changed 3 times after commencing descent 'via lynsy 1 landing runway 25L, runway 19L, runway 25L.' this required modifications to the route in the CDU each time. These modifications were made by the captain, not flying, across the throttle quadrant which is awkward at best, but breaches a basic constraint of being head down, manipulated the CDU at lower altitudes. This is fundamentally bad flying. The RNAV format is doable. However, there are enough variations, alterations, exceptions and ambiguities involved in the current execution of the RNAV procedures that a review or suspension of our participation in RNAV arrs/departures is warranted. Present utility of RNAV decreases safety (heads down), situational awareness (where we are in the flow to/from the airport), and position awareness. These procedures have not enhanced any aspect of company's operation from a plting perspective.

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Original NASA ASRS Text

Title: B737-300 CREW CLARIFIED ALT AND SPD CLRNC WITH THE CTLR. THE CREW NOTES THAT KEEPING THE FMS UPDATED PRESENTS AN INCREASED WORKLOAD PROB.

Narrative: OPINION ON RNAV. FLYING THE RNAV ARR SKEBR 1 FOR RWY 25L INTO LAS, WE HAD A COUPLE OF MODIFICATIONS TO THE CONSTRAINTS DEPICTED ON THE ARR AND A COUPLE OF CTLRS' DIRECTIVES THAT LEFT US IN DOUBT AS TO WHAT THE CTLRS WANTED FROM US. INDIVIDUALLY, THE MODIFICATIONS WERE SMALL AND EASILY COMPLIED WITH. COLLECTIVELY, THEY LED TO AMBIGUOUS INTENTIONS, DEV FROM STANDARD COCKPIT MGMNT AND INCREASED RADIO XMISSIONS FOR CLARIFICATION. PRIOR TO BEING HANDED OVER TO LAS APCH, CTR CLRED US TO DSND VIA SKEBR 1 RWY 25L, EXCEPT 9000 FT AT POVOC. CHKING IN WITH LAS APCH I STATED 'DSNDING VIA SKEBR 1 RWY 25L, POVOC AT 9000 FT.' APCH CORRECTED ME BY SAYING THAT WE WERE CLRED 'SKEBR 1 FOR RWY 25L.' I ASKED APCH IF THAT MEANT THEY WANTED ME TO COMPLY WITH THE SPDS AND ALTS, EXCEPT POVOC AT 9000 FT, DEPICTED ON THE CHART. ANSWER: YES. PRIOR TO IPUNY, WE WERE TOLD TO SLOW TO 220 KTS. NO DIRECTIONS GIVEN REF THE SPD AT POVOC. APCHING POVOC, I ASKED IF THEY WANTED THE DEPICTED 210 KTS OR THE PREVIOUSLY ISSUED 220 KTS. ANSWER: 210 KTS. PRIOR TO POVOC, WE WERE SWITCHED TO ANOTHER APCH CTLR. CHKING IN AT 9000 FT, WE WERE DIRECTED TO 'SLOW TO 170 KTS AT 8000 FT, LOWER IN 2 MINS.' AS NO REF WAS GIVEN TO LEAVING 9000 FT (EITHER AT POVOC OR IN 2 MINS), I HAD TO ASK IF WE WERE CLRED OUT OF 9000 FT. ANSWER (SOUNDING IRRITATED): YES, AT POVOC CLRED TO 8000 FT, SLOW TO 170 KTS REACHING.' WITH 3 MORE HDG/ALT/SPD CTLR REQUESTS, WE WERE ON AN 8 MI FINAL AND SWITCHING OVER TO TWR. THE PREVIOUS DAY, THE LNDG RWY WAS CHANGED 3 TIMES AFTER COMMENCING DSCNT 'VIA LYNSY 1 LNDG RWY 25L, RWY 19L, RWY 25L.' THIS REQUIRED MODIFICATIONS TO THE RTE IN THE CDU EACH TIME. THESE MODIFICATIONS WERE MADE BY THE CAPT, NOT FLYING, ACROSS THE THROTTLE QUADRANT WHICH IS AWKWARD AT BEST, BUT BREACHES A BASIC CONSTRAINT OF BEING HEAD DOWN, MANIPULATED THE CDU AT LOWER ALTS. THIS IS FUNDAMENTALLY BAD FLYING. THE RNAV FORMAT IS DOABLE. HOWEVER, THERE ARE ENOUGH VARIATIONS, ALTERATIONS, EXCEPTIONS AND AMBIGUITIES INVOLVED IN THE CURRENT EXECUTION OF THE RNAV PROCS THAT A REVIEW OR SUSPENSION OF OUR PARTICIPATION IN RNAV ARRS/DEPS IS WARRANTED. PRESENT UTILITY OF RNAV DECREASES SAFETY (HEADS DOWN), SITUATIONAL AWARENESS (WHERE WE ARE IN THE FLOW TO/FROM THE ARPT), AND POS AWARENESS. THESE PROCS HAVE NOT ENHANCED ANY ASPECT OF COMPANY'S OP FROM A PLTING PERSPECTIVE.

Data retrieved from NASA's ASRS site as of July 2007 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.