Narrative:

I was working wabash sh sector. Weather was starting to affect my airspace FL360 and above on my northernmost boundary with ZAU. The rides were mainly 'occasional light chop' at the time with very few deviations. An aircraft that I was receiving from ZAU was climbing to FL360; requesting FL370; with crossing eastbound traffic at FL370. When the pilot checked on my frequency; I acknowledged him and told him to maintain FL360 and to expect higher clearing traffic at FL370. About two minutes later; he called and said he was 'negative rvsm due to turbulence.' I rogered him and tried to figure out what he meant by that as I had never heard of a pilot losing rvsm due to the rides before. I had other matters that needed immediate attention and also looked around for the supervisor to inquire what I should do about that particular situation; but didn't see the supervisor anywhere. Soon after; another aircraft that was 30-40 miles east reported severe turbulence at FL370 and began having problems maintaining altitude and descended into traffic at FL360. I was busy trying to deal with that situation when I glanced over at the negative rvsm aircraft and noticed that he was climbing into my traffic at FL370! I do not know if separation was ever lost in both instances. I would like to know if the pilot was correct in stating negative rvsm due to turbulence or if he should have told me he couldn't maintain his altitude. My supervisors couldn't explain what was to be done either. Recommendation; I do not know of any way to be able to prevent this type of situation as the severe turbulence came on so suddenly.

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Original NASA ASRS Text

Title: ZID Controller described a non-RVSM compliance event that led to a probable loss of separation. An RVSM aircraft was unable to maintain altitude due to turbulence; the reporter claims governing rules are unclear.

Narrative: I was working Wabash SH sector. Weather was starting to affect my airspace FL360 and above on my Northernmost boundary with ZAU. The rides were mainly 'occasional light chop' at the time with very few deviations. An aircraft that I was receiving from ZAU was climbing to FL360; requesting FL370; with crossing Eastbound traffic at FL370. When the Pilot checked on my frequency; I acknowledged him and told him to maintain FL360 and to expect higher clearing traffic at FL370. About two minutes later; he called and said he was 'negative RVSM due to turbulence.' I rogered him and tried to figure out what he meant by that as I had never heard of a pilot losing RVSM due to the rides before. I had other matters that needed immediate attention and also looked around for the Supervisor to inquire what I should do about that particular situation; but didn't see the Supervisor anywhere. Soon after; another aircraft that was 30-40 miles East reported severe turbulence at FL370 and began having problems maintaining altitude and descended into traffic at FL360. I was busy trying to deal with that situation when I glanced over at the Negative RVSM aircraft and noticed that he was climbing into my traffic at FL370! I do not know if separation was ever lost in both instances. I would like to know if the Pilot was correct in stating negative RVSM due to turbulence or if he should have told me he couldn't maintain his altitude. My supervisors couldn't explain what was to be done either. Recommendation; I do not know of any way to be able to prevent this type of situation as the severe turbulence came on so suddenly.

Data retrieved from NASA's ASRS site as of April 2012 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.