Speed deviation by descending traffic.

Attributes
ACN	298900
Time
Date	199503
Day	Mon
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : dtw
State Reference	MI
Altitude	msl bound lower : 4000 msl bound upper : 6000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : dtw tower : iad
Operator	common carrier : air carrier
Make Model Name	B747-400
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 190 flight time total : 19000 flight time type : 2150
ASRS Report	298900
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe non adherence : far other anomaly
Independent Detector	other flight crewa
Resolutory Action	flight crew : overcame equipment problem
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

During descent (approximately 1500 FPM, 235-240 KTS) approach requested we increase our descent rate, vertical speed was selected to comply and to start the faster descent quicker. Speed was selected to 250 KTS and flight control heading was selected. Neither engaged and after a short attention to another matter (traffic watch, looking for airport, etc) it was noticed that the aircraft had accelerated to approximately 260-265 KTS. Autoplt was disengaged and reengaged, and flight control heading/speed re- selected. Worked satisfactorily after that. Cause - unknown. Remedy, not to be so aggressive in accommodating ATC.

Original NASA ASRS Text

Title: SPD DEV BY DSNDING TFC.

Narrative: DURING DSCNT (APPROX 1500 FPM, 235-240 KTS) APCH REQUESTED WE INCREASE OUR DSCNT RATE, VERT SPD WAS SELECTED TO COMPLY AND TO START THE FASTER DSCNT QUICKER. SPD WAS SELECTED TO 250 KTS AND FLT CTL HDG WAS SELECTED. NEITHER ENGAGED AND AFTER A SHORT ATTN TO ANOTHER MATTER (TFC WATCH, LOOKING FOR ARPT, ETC) IT WAS NOTICED THAT THE ACFT HAD ACCELERATED TO APPROX 260-265 KTS. AUTOPLT WAS DISENGAGED AND REENGAGED, AND FLT CTL HDG/SPD RE- SELECTED. WORKED SATISFACTORILY AFTER THAT. CAUSE - UNKNOWN. REMEDY, NOT TO BE SO AGGRESSIVE IN ACCOMMODATING ATC.

Data retrieved from NASA's ASRS site as of July 2007 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.