The flight crew of a B737 equipped with a rudimentary FMC failed to meet an ATC crossing restriction...

Narrative:

At fl 360 we were told to descend to fl 340 and then cross 85 NM east of pgs at fl 300. As the PF; after briefing the approach and going over the numbers with the pm; I lost track of the top of descent point resulting in a late start down on the profile. We crossed the crossing restriction approximately 1200 ft high. The descent and crossing restriction were issued very early; over 100 NM from the descent point; and after descending to fl 340. We first had to figure out what to put in the FMC since two waypoints (bavpe and cutro) were between pgs and the 85 NM fix. So the crossing restriction showed up prior to bavpe; cutro; then pgs; a little confusing. We then got ATIS; calculated the numbers on the performance computer; and proceeded to brief the approach and landing in las. After finishing those tasks and looking at the descent page; I saw about 9+ DME and assumed that distance was to the top of descent point; but it was actually to the crossing point. At abut 6 DME ATC mentioned the restriction; but we were unable to get down; crossing about 1200 ft high. Bavpe and cutro were still between us and pgs. Obviously I need to monitor things better than this event. I also think that crossing restrictions issued as early as this in a profile tend to create situations that with other events and tasks included; tend to become more susceptible to forgetting in the -300/-500 aircraft.

Original NASA ASRS Text

Title: The Flight Crew of a B737 equipped with a rudimentary FMC failed to meet an ATC crossing restriction due to difficulty interpreting the FMC display. Cite the complexity of defining the fix due to multiple intervening waypoints and the lack of clarity as to their location with respect to that fix.

Narrative: At FL 360 we were told to descend to FL 340 and then cross 85 NM east of PGS at FL 300. As the PF; after briefing the approach and going over the numbers with the PM; I lost track of the top of descent point resulting in a late start down on the profile. We crossed the crossing restriction approximately 1200 ft high. The descent and crossing restriction were issued very early; over 100 NM from the descent point; and after descending to FL 340. We first had to figure out what to put in the FMC since two waypoints (BAVPE and CUTRO) were between PGS and the 85 NM fix. So the crossing restriction showed up prior to BAVPE; CUTRO; then PGS; a little confusing. We then got ATIS; calculated the numbers on the performance computer; and proceeded to brief the approach and landing in LAS. After finishing those tasks and looking at the Descent page; I saw about 9+ DME and assumed that distance was to the top of descent point; but it was actually to the crossing point. At abut 6 DME ATC mentioned the restriction; but we were unable to get down; crossing about 1200 ft high. BAVPE and CUTRO were still between us and PGS. Obviously I need to monitor things better than this event. I also think that crossing restrictions issued as early as this in a profile tend to create situations that with other events and tasks included; tend to become more susceptible to forgetting in the -300/-500 aircraft.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	853848
Time
Date	200909
Local Time Of Day	0601-1200
Place
Locale Reference	ZAB.ARTCC
State Reference	NM
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Flight Phase	Descent
Flight Plan	IFR
Component
Aircraft Component	FMS/FMC
Person 1
Function	Captain
Experience	Flight Crew Last 90 Days 347 Flight Crew Type 12500
Person 2
Function	First Officer
Experience	Flight Crew Last 90 Days 262 Flight Crew Type 2400
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Crossing Restriction Not Met Deviation - Procedural Clearance

The flight crew of a B737 equipped with a rudimentary FMC failed to meet an ATC crossing restriction due to difficulty interpreting the FMC display. Cite the complexity of defining the fix due to multiple intervening waypoints and the lack of clarity as to their location with respect to that fix.