B737 captain reports being issued a hard altitude to cross mport then descend via the drllr 1 RNAV t...

Attributes
ACN	1188189
Time
Date	201407
Local Time Of Day	0601-1200
Place
Locale Reference	ZHU.ARTCC
State Reference	TX
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Descent
Flight Plan	IFR
Component
Aircraft Component	FMS/FMC
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 220 Flight Crew Total 10000 Flight Crew Type 7000
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Crossing Restriction Not Met Deviation - Procedural Clearance

Narrative:

Descending on the drllr 1 RNAV arrival to iah. Given a hard altitude to cross mport at; then 'descend via the drllr 1 arrival.' the FMC was correctly calculating the altitudes and speeds until the hard altitude crossing was given at the fix. Unknown as to the reason; but once the hard altitude is substituted for the between altitude; the FMC shows the aircraft significantly above the path. In my case yesterday; I was 2;000 ft above the FMC generated pdi path. Had to use full speedbrakes to make the hard altitude crossing restriction; then the rest of the RNAV descent was uneventful. You could probably easily re-create this in a simulator to the FAA controllers.

Original NASA ASRS Text

Title: B737 Captain reports being issued a hard altitude to cross MPORT then descend via the DRLLR 1 RNAV to IAH. When the hard altitude is entered in the FMC the aircraft is instantly 2;000 FT high on the descent path; requiring speedbrakes and high speed to make the crossing.

Narrative: Descending on the DRLLR 1 RNAV arrival to IAH. Given a hard altitude to cross MPORT at; then 'descend via the DRLLR 1 arrival.' The FMC was correctly calculating the altitudes and speeds until the hard altitude crossing was given at the fix. Unknown as to the reason; but once the hard altitude is substituted for the between altitude; the FMC shows the aircraft significantly above the path. In my case yesterday; I was 2;000 FT above the FMC generated PDI path. Had to use full speedbrakes to make the hard altitude crossing restriction; then the rest of the RNAV descent was uneventful. You could probably easily re-create this in a simulator to the FAA controllers.

Data retrieved from NASA's ASRS site 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.

B737 captain reports being issued a hard altitude to cross mport then descend via the drllr 1 RNAV to iah. When the hard altitude is entered in the FMC the aircraft is instantly 2;000 ft high on the descent path; requiring speedbrakes and high speed to make the crossing.