An md-80 flight crew placed too much confidence in the ability of the vdi to assure compliance with ...

Attributes
ACN	1059920
Time
Date	201301
Local Time Of Day	1201-1800
Place
Locale Reference	DCA.Airport
State Reference	DC
Aircraft 1
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Component
Aircraft Component	Autoflight System
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Altitude Crossing Restriction Not Met Deviation - Procedural Published Material / Policy Deviation - Procedural Clearance

Narrative:

On the trups RNAV STAR into dca; we were following the step downs; and at one point trusted the vdi to keep us out of trouble. I am not sure if there was a momentary glitch with the vdi but I noticed; approaching weedu that we needed to lose about three thousand feet in about seven miles. I mentioned that to the first officer and he threw the 'boards' out and aggressively descended. I am not sure that we actually made the crossing restriction due to the fact that weedu dropped out from the CDU and the nd about a mile or more before we got there. My first thought is I needed to pay better attention to the distance between fixes. Secondly; trusting the vdi might not be the best course of action; even though the company recommends the use of the vdi. This time it misled us a bit.

Original NASA ASRS Text

Title: An MD-80 flight crew placed too much confidence in the ability of the VDI to assure compliance with the crossing restriction at WEEDU on the TRUPS RNAV STAR inbound to DCA. Aggressive action after recognizing the failure may have resulted in making the crossing.

Narrative: On the TRUPS RNAV STAR into DCA; we were following the step downs; and at one point trusted the VDI to keep us out of trouble. I am not sure if there was a momentary glitch with the VDI but I noticed; approaching WEEDU that we needed to lose about three thousand feet in about seven miles. I mentioned that to the First Officer and he threw the 'boards' out and aggressively descended. I am not sure that we actually made the crossing restriction due to the fact that WEEDU dropped out from the CDU and the ND about a mile or more before we got there. My first thought is I needed to pay better attention to the distance between fixes. Secondly; trusting the VDI might not be the best course of action; even though the company recommends the use of the VDI. This time it misled us a bit.

Data retrieved from NASA's ASRS site as of July 2013 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.

An md-80 flight crew placed too much confidence in the ability of the vdi to assure compliance with the crossing restriction at weedu on the trups RNAV STAR inbound to dca. Aggressive action after recognizing the failure may have resulted in making the crossing.