Iai 1124 flight crew reported failure to meet crossing restriction resulting from lack of proper aut...

Attributes
ACN	1533819
Time
Date	201804
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	IAI1124/1124A Westwind
Operating Under FAR Part	Part 91
Flight Phase	Descent
Flight Plan	IFR
Component
Aircraft Component	FMS/FMC
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 45 Flight Crew Total 15000 Flight Crew Type 3500
Person 2
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 20 Flight Crew Total 19500 Flight Crew Type 255
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Crossing Restriction Not Met Deviation - Altitude Undershoot Deviation - Procedural Clearance Deviation - Procedural Published Material / Policy

Narrative:

While descending out of 24;000 feet with a crossing restriction of 7;000 feet MSL 25 miles west of ZZZ VOR; [we were] descending on the autopilot with VNAV info (-1;500 feet rate of descent required to make our crossing) off the [FMS]. I set the vertical rate of descent on the autopilot to 1;700 feet down; so we would reach the target altitude early. The VNAV page remained on the FMS to make sure we stayed ahead of the descent required. While running our transition check we were queried by ATC if we were going to be able to make the crossing restriction. I checked the FMS and according to it we were still well ahead of the descent rate required for the crossing altitude. I checked the DME off of ZZZ VOR and saw we were only 28 miles west of ZZZ VOR and still at 21;000 feet and descending 1;700 feet per minute which was 200 feet more than the VNAV was saying we needed. We were descending through 15;000 25 miles west of ZZZ VOR.the autopilot had been serviced prior to this trip and had been working fine till this leg. If I would have done the mental rate of descent calculations for our crossing restriction I would have seen how far off the FMS was and could have done it manually.

Original NASA ASRS Text

Title: IAI 1124 flight crew reported failure to meet crossing restriction resulting from lack of proper automation monitoring.

Narrative: While descending out of 24;000 feet with a crossing restriction of 7;000 feet MSL 25 miles west of ZZZ VOR; [we were] descending on the autopilot with VNAV info (-1;500 feet rate of descent required to make our crossing) off the [FMS]. I set the vertical rate of descent on the autopilot to 1;700 feet down; so we would reach the target altitude early. The VNAV page remained on the FMS to make sure we stayed ahead of the descent required. While running our transition check we were queried by ATC if we were going to be able to make the crossing restriction. I checked the FMS and according to it we were still well ahead of the descent rate required for the crossing altitude. I checked the DME off of ZZZ VOR and saw we were only 28 miles west of ZZZ VOR and still at 21;000 feet and descending 1;700 feet per minute which was 200 feet more than the VNAV was saying we needed. We were descending through 15;000 25 miles west of ZZZ VOR.The autopilot had been serviced prior to this trip and had been working fine till this leg. If I would have done the mental rate of descent calculations for our crossing restriction I would have seen how far off the FMS was and could have done it manually.

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.

Iai 1124 flight crew reported failure to meet crossing restriction resulting from lack of proper automation monitoring.