Narrative:

We were cleared to hold as published at rbv on korry 2 into rga, and reported established as published 68 degrees/248 degrees. Aircraft Y was accumulating ice, and requested lower. ATC assigned 11000 ft MSL -- 1000 ft above our assigned altitude. Very low press altimeter confirmed with ATC twice approximately 29.02. Obviously, aircraft Y's altimeter remained at 29.92 inches as our standby altimeter was set to reference their possible deviation. ATC queried their altitude 2 or 3 times. They responded '11000,' unaware of the altimeter setting. ATC inquired no further. Also, their aircraft was not holding as published 68 degrees/248 degrees. Instead, they were holding on inbound course 238 degrees. We visually acquired aircraft Y too close, as they descended to, and entered, hold within 200 ft of our altitude just behind us. Obviously, we were obscured below their nose. We accelerated our aircraft briefly to achieve some spacing in pattern. ATC then told us to 'be sure and hold as published.' aircraft Y became aware of the altimeter error, and climbed to 1000 ft above our altitude. Controller advised 'this is a very low altitude setting and proper setting is important.' no TCASII alert!

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Original NASA ASRS Text

Title: CL65 FLT CREW OBSERVES MD88 IN CLOSE PROX IN HOLDING PATTERN, POSSIBLY DUE TO ALTIMETER SETTING ERROR.

Narrative: WE WERE CLRED TO HOLD AS PUBLISHED AT RBV ON KORRY 2 INTO RGA, AND RPTED ESTABLISHED AS PUBLISHED 68 DEGS/248 DEGS. ACFT Y WAS ACCUMULATING ICE, AND REQUESTED LOWER. ATC ASSIGNED 11000 FT MSL -- 1000 FT ABOVE OUR ASSIGNED ALT. VERY LOW PRESS ALTIMETER CONFIRMED WITH ATC TWICE APPROX 29.02. OBVIOUSLY, ACFT Y'S ALTIMETER REMAINED AT 29.92 INCHES AS OUR STANDBY ALTIMETER WAS SET TO REF THEIR POSSIBLE DEV. ATC QUERIED THEIR ALT 2 OR 3 TIMES. THEY RESPONDED '11000,' UNAWARE OF THE ALTIMETER SETTING. ATC INQUIRED NO FURTHER. ALSO, THEIR ACFT WAS NOT HOLDING AS PUBLISHED 68 DEGS/248 DEGS. INSTEAD, THEY WERE HOLDING ON INBOUND COURSE 238 DEGS. WE VISUALLY ACQUIRED ACFT Y TOO CLOSE, AS THEY DSNDED TO, AND ENTERED, HOLD WITHIN 200 FT OF OUR ALT JUST BEHIND US. OBVIOUSLY, WE WERE OBSCURED BELOW THEIR NOSE. WE ACCELERATED OUR ACFT BRIEFLY TO ACHIEVE SOME SPACING IN PATTERN. ATC THEN TOLD US TO 'BE SURE AND HOLD AS PUBLISHED.' ACFT Y BECAME AWARE OF THE ALTIMETER ERROR, AND CLBED TO 1000 FT ABOVE OUR ALT. CTLR ADVISED 'THIS IS A VERY LOW ALT SETTING AND PROPER SETTING IS IMPORTANT.' NO TCASII ALERT!

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.