Air carrier large transport altitude deviation overshot.

Attributes
ACN	192017
Time
Date	199110
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : ott
State Reference	MD
Altitude	msl bound lower : 31600 msl bound upper : 31000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc tracon : den
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 3 Turbojet Eng
Flight Phase	cruise other descent other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 120 flight time total : 2500 flight time type : 100
ASRS Report	192017
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : overshoot conflict : airborne less severe non adherence : clearance
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera
Resolutory Action	flight crew : returned to intended course or assigned course other
Consequence	Other
Miss Distance	horizontal : 30000 vertical : 1500
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We were given a descent clearance to cross 20 mi north of ott at FL290. (We were at 330 and 40 mi south.) I switched radios (we have 2) to receive ATIS into phl when the controller amended our clearance to 'pilot discretion to 310 and expect same crossing restrictions.' traffic was called at 1 O'clock and 7-8 mi FL290. Traffic was located visually and on TCASII. As our aircraft past 30600 ft ATC issued a climb back to 31000 and TCASII issued a TA. Traffic passed in front of us 5-6 mi and 1500 ft below. A misunderstanding of the amended clearance was the cause for this deviation. Vigilance on the part of ATC, the air crew and TCASII avoided further altdevs.

Original NASA ASRS Text

Title: ACR LGT ALTDEV OVERSHOT.

Narrative: WE WERE GIVEN A DSCNT CLRNC TO CROSS 20 MI N OF OTT AT FL290. (WE WERE AT 330 AND 40 MI S.) I SWITCHED RADIOS (WE HAVE 2) TO RECEIVE ATIS INTO PHL WHEN THE CTLR AMENDED OUR CLRNC TO 'PLT DISCRETION TO 310 AND EXPECT SAME XING RESTRICTIONS.' TFC WAS CALLED AT 1 O'CLOCK AND 7-8 MI FL290. TFC WAS LOCATED VISUALLY AND ON TCASII. AS OUR ACFT PAST 30600 FT ATC ISSUED A CLB BACK TO 31000 AND TCASII ISSUED A TA. TFC PASSED IN FRONT OF US 5-6 MI AND 1500 FT BELOW. A MISUNDERSTANDING OF THE AMENDED CLRNC WAS THE CAUSE FOR THIS DEV. VIGILANCE ON THE PART OF ATC, THE AIR CREW AND TCASII AVOIDED FURTHER ALTDEVS.

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.