A MD80 flight crew mistakenly tuned an incorrect approach frequency and thought they heard a descent clearance. Following a period of silence; the correct frequency was selected and the crew was told of their incorrect descent and possible deviation.
Synopsis
A MD80 flight crew mistakenly tuned an incorrect approach frequency and thought they heard a descent clearance. Following a period of silence; the correct frequency was selected and the crew was told of their incorrect descent and possible deviation.
Narrative
After landing; Tower gave us Center phone number for a possible pilot deviation. Center stated we had descended from 12;000 FT to 10;000 FT without proper clearance. Here are the facts of the event. Flying the Arrival; Center subsequently cleared us directly to Airport; maintain 12;000 FT. I acknowledged and we complied. During the frequency change to Approach Control; I called on 124.95 with our descent clearance to 12;000 FT. Although the radio was scratchy; both the First Officer and I thought we heard a descent clearance to 10;000 FT. I responded with our descent to 'one zero thousand.' I then responded to Approach Control to expect vector for a visual approach to Runway 20. After that; Approach Control frequency became extremely scratchy and weak. I called Approach Control stated he was unreadable. After a call in-the-blind. I switched to chart frequency 132.02. Checking in with Approach Control on 132.02 (descending through approximately 11;700 FT); The Controller asked us our assigned altitude. I told him 10;000 FT. There was no further discussion concerning our descent to 10;000 FT with Approach Control. The approach and landing was uneventful. I now realize the correct; initial frequency for Approach Control was 124.97. My thinking is that there must have been some bleed-through from 124.97 to 124.95. I very much regret the events of this situation. Again; I must emphasize both the First Officer and I thought we heard a clearance to 10;000 FT; and that we believed we very properly complying with instructions and procedures. During my phone call with Center; he told me there was no loss of separation.
Second reporter narrative
I was pilot flying the Arrival. Center had given us direct to our destination; maintain 12;000 FT; and then gave us a frequency change to Approach Control. Captain checked in on frequency 124.95. We heard a weak transmission to maintain 10;000 FT. Did not hear Approach respond; although we could hear some talk on the frequency; but it was unreadable. The Captain started looking at the arrival chart for an alternate frequency; and subsequently descent clearance; and told us we had tuned the initial frequency incorrectly and it should have been 124.97. The Controller said nothing more about our altitude. For me; the lesson learned is that if there is any concern over the audio reception; go back to the previous frequency to seek a correction. I believe the frequency was just close enough for some reception and we acted accordingly for what we both thought we had heard.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.