Narrative:

An E170 was on my frequency transitioning through my airspace at FL350. There were reports of constant light to occasional moderate chop being reported and most aircraft were descending to lower altitudes to get better rides. Another aircraft checked on my frequency and after telling the aircraft of the rides to expect they requested lower. The aircraft was not in my airspace so I called on the land line to coordinate lower. While I was off line coordinating I heard over the speaker somebody request something. I got off the line; transmitted in the blind that I was off the line coordinating and I would be right back with them. I then finished my coordination; and descended the aircraft that had requested lower. Then I observed the E170 descending out of FL343. I called the E170 to verify level at FL350. He told me that he had encountered constant moderate chop bordering on severe and the way I understood it the aircraft had to descend to keep his speed. He told me something about being near the safety envelope and needing to descend immediately. He told me he didn't require assistance now that he had descended. I worked the sector for another hour and never had a report of worse then occasional moderate chop. It's the first time in my experience that I've heard of a plane needing to descend so urgently; without an emergency. I felt I was taking care of the aircraft on first come; first serve basis. I'm pretty sure if I could have heard the E170's first request transmission instead of going over the speaker since I was on the line; I could have gotten him his clearance in time for him to not have to take matters into his own hands.

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Original NASA ASRS Text

Title: ZID Controller described an unexpected descent by an Air Carrier at FL350 during a turbulence encounter. The Controller did not hear the initial descent request because of land line coordination.

Narrative: An E170 was on my frequency transitioning through my airspace at FL350. There were reports of constant light to occasional moderate chop being reported and most aircraft were descending to lower altitudes to get better rides. Another aircraft checked on my frequency and after telling the aircraft of the rides to expect they requested lower. The aircraft was not in my airspace so I called on the land line to coordinate lower. While I was off line coordinating I heard over the speaker somebody request something. I got off the line; transmitted in the blind that I was off the line coordinating and I would be right back with them. I then finished my coordination; and descended the aircraft that had requested lower. Then I observed the E170 descending out of FL343. I called the E170 to verify level at FL350. He told me that he had encountered constant moderate chop bordering on severe and the way I understood it the aircraft had to descend to keep his speed. He told me something about being near the safety envelope and needing to descend immediately. He told me he didn't require assistance now that he had descended. I worked the sector for another hour and never had a report of worse then occasional moderate chop. It's the first time in my experience that I've heard of a plane needing to descend so urgently; without an emergency. I felt I was taking care of the aircraft on first come; first serve basis. I'm pretty sure if I could have heard the E170's first request transmission instead of going over the speaker since I was on the line; I could have gotten him his clearance in time for him to not have to take matters into his own hands.

Data retrieved from NASA's ASRS site as of July 2013 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.