B747 at FL350 changes to bos altitude for descent, climbs 700 ft, and conflicted with en route F900.

Attributes
ACN	602242
Time
Date	200312
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	navaid : bos.vortac
State Reference	MA
Altitude	msl bound lower : 34000 msl bound upper : 34700
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Controlling Facilities	artcc : zbw.artcc
Operator	common carrier : air carrier
Make Model Name	B747-400
Operating Under FAR Part	Part 121
Navigation In Use	other other
Flight Phase	cruise : enroute altitude change
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zbw.artcc
Operator	general aviation : personal
Make Model Name	Falcon 900
Operating Under FAR Part	Part 91
Flight Phase	cruise : level
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller radar : 17
ASRS Report	602242
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe non adherence : published procedure
Independent Detector	aircraft equipment : tcas other controllera
Resolutory Action	controller : issued advisory controller : issued new clearance
Consequence	faa : investigated
Miss Distance	horizontal : 18000 vertical : 300
Supplementary
Problem Areas	Flight Crew Human Performance
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I issued a crossing restr to aircraft X, who was inbound to boston, ma, to cross scupp at 11000 ft at time XA09Z, with the altimeter setting of 29.19. Aircraft X was level at FL340 when I issued this restr. He had opposite direction traffic at FL350 who was also equipped with rvsm equipment. This aircraft, aircraft Y, a F900/Q reported an aircraft in close proximity of 300 ft so I turned him 30 degrees right, away from traffic. His traffic was aircraft X, whose altitude now indicated he was at FL347. I asked aircraft X to verify leaving FL340. He reported at FL340 and said he had a pilot's discretion descent. I believe what happened is the pilot of aircraft X set his altimeter to 29.19 when I first issued the altimeter. This would account for the 700 ft he climbed from FL340 to FL347. Aircraft X type aircraft was a B747-400/west.

Original NASA ASRS Text

Title: B747 AT FL350 CHANGES TO BOS ALT FOR DSCNT, CLBS 700 FT, AND CONFLICTED WITH ENRTE F900.

Narrative: I ISSUED A XING RESTR TO ACFT X, WHO WAS INBOUND TO BOSTON, MA, TO CROSS SCUPP AT 11000 FT AT TIME XA09Z, WITH THE ALTIMETER SETTING OF 29.19. ACFT X WAS LEVEL AT FL340 WHEN I ISSUED THIS RESTR. HE HAD OPPOSITE DIRECTION TFC AT FL350 WHO WAS ALSO EQUIPPED WITH RVSM EQUIP. THIS ACFT, ACFT Y, A F900/Q RPTED AN ACFT IN CLOSE PROX OF 300 FT SO I TURNED HIM 30 DEGS R, AWAY FROM TFC. HIS TFC WAS ACFT X, WHOSE ALT NOW INDICATED HE WAS AT FL347. I ASKED ACFT X TO VERIFY LEAVING FL340. HE RPTED AT FL340 AND SAID HE HAD A PLT'S DISCRETION DSCNT. I BELIEVE WHAT HAPPENED IS THE PLT OF ACFT X SET HIS ALTIMETER TO 29.19 WHEN I FIRST ISSUED THE ALTIMETER. THIS WOULD ACCOUNT FOR THE 700 FT HE CLBED FROM FL340 TO FL347. ACFT X TYPE ACFT WAS A B747-400/W.

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.