DC9 crew undershot an altitude crossing restr.

Attributes
ACN	425990
Time
Date	199901
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : har
State Reference	PA
Altitude	msl bound lower : 25000 msl bound upper : 26000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	DC-9 30
Flight Phase	descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : flight engineer pilot : instrument pilot : cfi
Experience	flight time last 90 days : 150 flight time total : 14000 flight time type : 7500
ASRS Report	425990
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : commercial pilot : flight engineer pilot : instrument
Experience	flight time last 90 days : 210 flight time total : 12000 flight time type : 1600
ASRS Report	426103
Events
Anomaly	altitude deviation : crossing restriction not met altitude deviation : undershoot other anomaly other
Independent Detector	other controllera other flight crewa
Consequence	Other
Supplementary
Air Traffic Incident	Pilot Deviation

Narrative:

We were at FL310 on radar vectors toward har. About 90 NM west of har, ATC gave us a crossing restr west of har. At about 65 NM west of har, ATC told us to start our descent. A handoff was made to the next sector and the new controller asked whether we had an altitude clearance. This was approximately 45 NM west of har. We were passing FL260 for FL250. The captain had apparently accepted and read back a clearance to cross 45 NM west of har at FL250. I had heard the clearance restr as a crossing 25 NM west of har at FL250. In the controller's next transmission we were cleared to FL180. No other traffic was observed visually or on TCASII. The controller didn't call out any other traffic. This was a simple miscom on what distance the altitude was to be reached by. We both verbalized the altitude when setting the alerter. I thought the controller and captain both said 25 NM. The captain thought I said 45 NM.

Original NASA ASRS Text

Title: DC9 CREW UNDERSHOT AN ALT XING RESTR.

Narrative: WE WERE AT FL310 ON RADAR VECTORS TOWARD HAR. ABOUT 90 NM W OF HAR, ATC GAVE US A XING RESTR W OF HAR. AT ABOUT 65 NM W OF HAR, ATC TOLD US TO START OUR DSCNT. A HDOF WAS MADE TO THE NEXT SECTOR AND THE NEW CTLR ASKED WHETHER WE HAD AN ALT CLRNC. THIS WAS APPROX 45 NM W OF HAR. WE WERE PASSING FL260 FOR FL250. THE CAPT HAD APPARENTLY ACCEPTED AND READ BACK A CLRNC TO CROSS 45 NM W OF HAR AT FL250. I HAD HEARD THE CLRNC RESTR AS A XING 25 NM W OF HAR AT FL250. IN THE CTLR'S NEXT XMISSION WE WERE CLRED TO FL180. NO OTHER TFC WAS OBSERVED VISUALLY OR ON TCASII. THE CTLR DIDN'T CALL OUT ANY OTHER TFC. THIS WAS A SIMPLE MISCOM ON WHAT DISTANCE THE ALT WAS TO BE REACHED BY. WE BOTH VERBALIZED THE ALT WHEN SETTING THE ALERTER. I THOUGHT THE CTLR AND CAPT BOTH SAID 25 NM. THE CAPT THOUGHT I SAID 45 NM.

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.