Altitude deviation.

Attributes
ACN	145307
Time
Date	199005
Day	Fri
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : zjx
State Reference	FL
Altitude	msl bound lower : 23000 msl bound upper : 24000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zjx tracon : anc
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other
Route In Use	enroute : direct enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : instrument pilot : commercial pilot : flight engineer
Experience	flight time last 90 days : 170 flight time total : 7000 flight time type : 80
ASRS Report	145307
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 130 flight time total : 3675 flight time type : 130
ASRS Report	145014
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Ambiguous
Air Traffic Incident	Pilot Deviation Operational Deviation other

Narrative:

En route on frequency 135.65 we received the following clearance: 'flight X, descend to and maintain FL230 for traffic, and contact jax center on 128.05', or so I thought. I read back the clearance, specifically reading back the altitude, and we switched to 128.05. The controller on 128.05 asked us to identify, and then told us we should be on 128.07. We checked in on 128.07, and heard 'flight X, flight X, climb to and maintain FL240'. At that time we were descending through 23300'; we promptly disengaged the autoplt, started a climb back towards FL240, and verified the assigned altitude. The controller then said that we'd probably picked up someone else's clearance. Contributing factors: too many aircraft on frequency may have led controller to miss our readback. Pilot didn't verify after readback before going off frequency. Confusion on the part of the second controller (128.05) as to who we were led to delay in detecting the deviation.

Original NASA ASRS Text

Title: ALT DEVIATION.

Narrative: ENRTE ON FREQ 135.65 WE RECEIVED THE FOLLOWING CLRNC: 'FLT X, DSND TO AND MAINTAIN FL230 FOR TFC, AND CONTACT JAX CTR ON 128.05', OR SO I THOUGHT. I READ BACK THE CLRNC, SPECIFICALLY READING BACK THE ALT, AND WE SWITCHED TO 128.05. THE CTLR ON 128.05 ASKED US TO IDENT, AND THEN TOLD US WE SHOULD BE ON 128.07. WE CHKED IN ON 128.07, AND HEARD 'FLT X, FLT X, CLB TO AND MAINTAIN FL240'. AT THAT TIME WE WERE DSNDING THROUGH 23300'; WE PROMPTLY DISENGAGED THE AUTOPLT, STARTED A CLB BACK TOWARDS FL240, AND VERIFIED THE ASSIGNED ALT. THE CTLR THEN SAID THAT WE'D PROBABLY PICKED UP SOMEONE ELSE'S CLRNC. CONTRIBUTING FACTORS: TOO MANY ACFT ON FREQ MAY HAVE LED CTLR TO MISS OUR READBACK. PLT DIDN'T VERIFY AFTER READBACK BEFORE GOING OFF FREQ. CONFUSION ON THE PART OF THE SECOND CTLR (128.05) AS TO WHO WE WERE LED TO DELAY IN DETECTING THE DEVIATION.

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.