Air carrier X non adherence to ATC clearance excursion from assigned altitude. Pilot deviation.

Attributes
ACN	180669
Time
Date	199106
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : sea
State Reference	WA
Altitude	msl bound lower : 2800 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Controlling Facilities	tracon : sea tracon : sea
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other
Flight Phase	descent : approach
Route In Use	approach : visual
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 5000
ASRS Report	180669
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Resolutory Action	controller : issued new clearance
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Air carrier X on approach to runway 34R at sea. We were cleared to intercept sea runway 34R localizer and descend to 4000'. 1 min later a weaker voice cleared us for visibility approach to runway 34R. I, first officer and PNF, acknowledged that we were cleared for the visibility approach runway 34R. I noted at the time that the controller hadn't asked if we had the airport or other aircraft in sight, but discounted any worry because it was visibility flight conditions. At 2800' MSL a stronger-signalled voice asked if we had the airport in sight and cleared us for a visibility approach runway 34R. At this time I realized the first communication was false, and having descended to 2800', had busted altitude. The NOTAMS for sea didn't mention 'false broadcasts,' nor did ATIS nor ATC.

Original NASA ASRS Text

Title: ACR X NON ADHERENCE TO ATC CLRNC EXCURSION FROM ASSIGNED ALT. PLT DEVIATION.

Narrative: ACR X ON APCH TO RWY 34R AT SEA. WE WERE CLRED TO INTERCEPT SEA RWY 34R LOC AND DSND TO 4000'. 1 MIN LATER A WEAKER VOICE CLRED US FOR VIS APCH TO RWY 34R. I, F/O AND PNF, ACKNOWLEDGED THAT WE WERE CLRED FOR THE VIS APCH RWY 34R. I NOTED AT THE TIME THAT THE CTLR HADN'T ASKED IF WE HAD THE ARPT OR OTHER ACFT IN SIGHT, BUT DISCOUNTED ANY WORRY BECAUSE IT WAS VIS FLT CONDITIONS. AT 2800' MSL A STRONGER-SIGNALLED VOICE ASKED IF WE HAD THE ARPT IN SIGHT AND CLRED US FOR A VIS APCH RWY 34R. AT THIS TIME I REALIZED THE FIRST COM WAS FALSE, AND HAVING DSNDED TO 2800', HAD BUSTED ALT. THE NOTAMS FOR SEA DIDN'T MENTION 'FALSE BROADCASTS,' NOR DID ATIS NOR 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.