MD-80 Series (DC-9-80) Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Human-Machine Interface
Aircraft Equipment Problem Less Severe; Deviation - Altitude Crossing Restriction Not Met; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Flight Crew Returned To Clearance
Chart Or Publication; Aircraft; Procedure
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.
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.