Narrative:

Filed flight plan was nuw -- IR348. In departure, initial climb clearance was to 9000 ft. Whidbey departure gave following clearance after takeoff, 'cleared to maintain IR348 altitudes.' (which, for first leg, are 500 ft AGL to 13000 ft MSL.) this is an ambiguous clearance in that it implies that aircraft is cleared now to those altitudes. In an attempt to attain VMC, aircraft was climbed to approximately 11500. After nuw 059/20 when ZSE said our clearance was only to 9000 ft. ZSE's UHF radio was barely readable (we reported as such) due partly to our radios which are known to provide loud static when in clouds (arc-182). Aircraft began descent to 9000 ft until 24 DME (IR348) then resumed climb to 13000 ft MSL where a clearance to 17000 ft MSL was requested and IR348 was cancelled.

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Original NASA ASRS Text

Title: PLT OF AN MIL MTR ACFT INADVERTENTLY OVERSHOT ASSIGNED ALT DUE TO HIS MISUNDERSTANDING OF THE DEPT CLRNC.

Narrative: FILED FLT PLAN WAS NUW -- IR348. IN DEP, INITIAL CLB CLRNC WAS TO 9000 FT. WHIDBEY DEP GAVE FOLLOWING CLRNC AFTER TKOF, 'CLRED TO MAINTAIN IR348 ALTS.' (WHICH, FOR FIRST LEG, ARE 500 FT AGL TO 13000 FT MSL.) THIS IS AN AMBIGUOUS CLRNC IN THAT IT IMPLIES THAT ACFT IS CLRED NOW TO THOSE ALTS. IN AN ATTEMPT TO ATTAIN VMC, ACFT WAS CLBED TO APPROX 11500. AFTER NUW 059/20 WHEN ZSE SAID OUR CLRNC WAS ONLY TO 9000 FT. ZSE'S UHF RADIO WAS BARELY READABLE (WE RPTED AS SUCH) DUE PARTLY TO OUR RADIOS WHICH ARE KNOWN TO PROVIDE LOUD STATIC WHEN IN CLOUDS (ARC-182). ACFT BEGAN DSCNT TO 9000 FT UNTIL 24 DME (IR348) THEN RESUMED CLB TO 13000 FT MSL WHERE A CLRNC TO 17000 FT MSL WAS REQUESTED AND IR348 WAS CANCELLED.

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.