Narrative:

We were on the arrival which is a non-RNAV approach. During the descent we went through some areas of heavy rain and I could only hear static on the radios. While in the precipitation the static continued. I tried changing radios and was able to hear ATC. However; the static continued in the radios. On the descent we were asked if we could take a different arrival. We were RNAV capable and we accepted. This happened as we were starting our descent from cruise altitude to our crossing restriction of 16;000. Both pilots thought we heard that we were then cleared to descend on a new arrival. This approach allows us to descend below 16;000 after passing an initial. After we passed the constraining fix we started down/per the new arrival. At 14;800 ATC said we should have stayed at 16;000. We started back up and were told we could stay at 15;000. The next controller said not to worry about it. No action on our part was required from ATC. The static on the radios probably caused most of the confusion. At least twice we heard ATC calling us and asking if we could hear them; and that they had been calling us. This was before the incident happened; if ATC didn't clear us to descend; then the static on the radio aided in the confusion. Both pilots thought we heard the same thing. It is possible that human error on ATC's part aided in this problem. When they wanted us to change to the newer approach; they may have wanted to clear us for the navigation only part; but cleared us to descend also. Consider examining the radios that get high amounts of static in precipitation. As stated both pilots thought we had heard to descend by the arrival. Maybe reading back that we are clear to descend by the arrival would help with this.

Google
 

Original NASA ASRS Text

Title: An MD80's radios had so much static while in heavy precipitation near thundstorms that the crew could not hear the TRACON and had an altitude deviation because they thought they were cleared for a different arrival but were not.

Narrative: We were on the arrival which is a non-RNAV approach. During the descent we went through some areas of heavy rain and I could only hear static on the radios. While in the precipitation the static continued. I tried changing radios and was able to hear ATC. However; the static continued in the radios. On the descent we were asked if we could take a different arrival. We were RNAV capable and we accepted. This happened as we were starting our descent from cruise altitude to our crossing restriction of 16;000. Both pilots thought we heard that we were then cleared to descend on a new arrival. This approach allows us to descend below 16;000 after passing an initial. After we passed the constraining fix we started down/per the new arrival. At 14;800 ATC said we should have stayed at 16;000. We started back up and were told we could stay at 15;000. The next Controller said not to worry about it. No action on our part was required from ATC. The static on the radios probably caused most of the confusion. At least twice we heard ATC calling us and asking if we could hear them; and that they had been calling us. This was before the incident happened; if ATC didn't clear us to descend; then the static on the radio aided in the confusion. Both pilots thought we heard the same thing. It is possible that human error on ATC's part aided in this problem. When they wanted us to change to the newer approach; they may have wanted to clear us for the NAV only part; but cleared us to descend also. Consider examining the radios that get high amounts of static in precipitation. As stated both pilots thought we had heard to descend by the arrival. Maybe reading back that we are clear to descend by the arrival would help with this.

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.