Similar call signs and frequency blocking congestion result in an altitude excursion near lga, ny.

Attributes
ACN	496720
Time
Date	200012
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : lga.vor
State Reference	NY
Altitude	msl bound lower : 22000 msl bound upper : 23500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zny.artcc tower : jxn.tower
Operator	common carrier : air carrier
Make Model Name	DC-9 30
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	cruise : level
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zny.artcc
Operator	common carrier : air carrier
Make Model Name	DC-9 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 8000 flight time type : 3000
ASRS Report	496720
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 7500 flight time type : 450
ASRS Report	496173
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllerb
Resolutory Action	controller : issued advisory controller : issued new clearance
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Lga 322 degree radial, 52 DME, FL220, air carrier flight xyy given climb to FL350 and expedite through FL250 from ZNY. Transmission acknowledged and climb began. Heard unreadable transmission and then ZNY gave air carrier flight xxy clearance to climb to FL350. Shortly after, ZNY called air carrier xyy, and told us to descend back to FL220, that we were not given clearance to climb. Apparent miscom between like call signs and unreadable radio xmissions. Both captain and first officer acknowledged clearance to FL350 to ZNY.

Original NASA ASRS Text

Title: SIMILAR CALL SIGNS AND FREQ BLOCKING CONGESTION RESULT IN AN ALT EXCURSION NEAR LGA, NY.

Narrative: LGA 322 DEG RADIAL, 52 DME, FL220, ACR FLT XYY GIVEN CLB TO FL350 AND EXPEDITE THROUGH FL250 FROM ZNY. XMISSION ACKNOWLEDGED AND CLB BEGAN. HEARD UNREADABLE XMISSION AND THEN ZNY GAVE ACR FLT XXY CLRNC TO CLB TO FL350. SHORTLY AFTER, ZNY CALLED ACR XYY, AND TOLD US TO DSND BACK TO FL220, THAT WE WERE NOT GIVEN CLRNC TO CLB. APPARENT MISCOM BTWN LIKE CALL SIGNS AND UNREADABLE RADIO XMISSIONS. BOTH CAPT AND FO ACKNOWLEDGED CLRNC TO FL350 TO ZNY.

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.