G2 flight crew with ZTL at FL410 mistakenly accepts descent clearance for similar sounding aircraft.

Attributes
ACN	637736
Time
Date	200411
Day	Sat
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : mgm.vortac
State Reference	AL
Altitude	msl bound lower : 38500 msl bound upper : 41000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : ztl.artcc
Operator	general aviation : corporate
Make Model Name	Gulfstream 200 [G200] (IAI 1126 Galaxy)
Operating Under FAR Part	Part 91
Navigation In Use	other
Flight Phase	cruise : enroute altitude change
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : ztl.artcc
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : cfi
Experience	flight time last 90 days : 50 flight time total : 10500 flight time type : 120
ASRS Report	637736
Person 2
Affiliation	company : corporate
Function	flight crew : first officer
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	Flight Crew Human Performance

Narrative:

While at cruise flight, FL410, we were handed off to another ZTL frequency. Shortly after tuning in, we believed we were given a descent clearance to FL310. I thought this was unusual as we were still 90 mins from our destination. I asked the reason for descent clearance and was told it was for traffic. The MOA's off the east coast were in effect so there were a lot of aircraft using over land instead of atlantic rtes. I started a descent and had the first officer call again to verify. The controller said that clearance was not for us (aircraft abc) but for 'air carrier abc.' we began to climb from FL385 back to FL410. We stated our position and altitude and were handed off to another ZTL frequency. Similar call signs can lead to problems. I should have been more direct in my questioning this clearance. The controller should have noticed that 2 readbacks were from an incorrect call sign. My hope is that as the voice frequencys become more congested, and more aircraft have call signs easily confused, we will develop electronic data delivery of airborne clrncs. We already have pre departure clearance's through afis and ACARS. This should not be that costly to develop and implement. Until then, I know I'll try to be more careful of confusing call signs.

Original NASA ASRS Text

Title: G2 FLT CREW WITH ZTL AT FL410 MISTAKENLY ACCEPTS DSCNT CLRNC FOR SIMILAR SOUNDING ACFT.

Narrative: WHILE AT CRUISE FLT, FL410, WE WERE HANDED OFF TO ANOTHER ZTL FREQ. SHORTLY AFTER TUNING IN, WE BELIEVED WE WERE GIVEN A DSCNT CLRNC TO FL310. I THOUGHT THIS WAS UNUSUAL AS WE WERE STILL 90 MINS FROM OUR DEST. I ASKED THE REASON FOR DSCNT CLRNC AND WAS TOLD IT WAS FOR TFC. THE MOA'S OFF THE EAST COAST WERE IN EFFECT SO THERE WERE A LOT OF ACFT USING OVER LAND INSTEAD OF ATLANTIC RTES. I STARTED A DSCNT AND HAD THE FO CALL AGAIN TO VERIFY. THE CTLR SAID THAT CLRNC WAS NOT FOR US (ACFT ABC) BUT FOR 'ACR ABC.' WE BEGAN TO CLB FROM FL385 BACK TO FL410. WE STATED OUR POS AND ALT AND WERE HANDED OFF TO ANOTHER ZTL FREQ. SIMILAR CALL SIGNS CAN LEAD TO PROBS. I SHOULD HAVE BEEN MORE DIRECT IN MY QUESTIONING THIS CLRNC. THE CTLR SHOULD HAVE NOTICED THAT 2 READBACKS WERE FROM AN INCORRECT CALL SIGN. MY HOPE IS THAT AS THE VOICE FREQS BECOME MORE CONGESTED, AND MORE ACFT HAVE CALL SIGNS EASILY CONFUSED, WE WILL DEVELOP ELECTRONIC DATA DELIVERY OF AIRBORNE CLRNCS. WE ALREADY HAVE PDC'S THROUGH AFIS AND ACARS. THIS SHOULD NOT BE THAT COSTLY TO DEVELOP AND IMPLEMENT. UNTIL THEN, I KNOW I'LL TRY TO BE MORE CAREFUL OF CONFUSING CALL SIGNS.

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.