B737-200 captain accidentally turned the volume down on his communication radio.

Attributes
ACN	525101
Time
Date	200109
Day	Wed
Local Time Of Day	1201 To 1800
Place
State Reference	IN
Altitude	msl single value : 21000
Environment
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau.artcc
Operator	common carrier : air carrier
Make Model Name	B737-200
Operating Under FAR Part	Part 121
Flight Phase	descent : vacating altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 220 flight time total : 9000 flight time type : 220
ASRS Report	525101
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 180 flight time total : 3000 flight time type : 800
ASRS Report	525281
Events
Anomaly	other anomaly other
Independent Detector	other flight crewa
Resolutory Action	controller : issued new clearance controller : issued alert none taken : detected after the fact other
Consequence	other
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Flight Crew Human Performance

Narrative:

ZAU frequency 135.9 over gsh VOR on the gsh.GHS3 arrival. I was PF, first officer was off frequency on VHF #2 getting mdw ATC. I asked ATC for a descent clearance. I asked if they wanted us to cross awsum at 10000 ft. There was no reply, so I checked the radio volume and turned it up. ATC was calling us and we were given our clearance to descend and we expedited our descent. The B737-200 is different from the other models we fly in that the radio volume control is top on a stack of knobs that also change the frequency. It is easy to inadvertently reduce the volume as it doesn't have detent 'steps' like the frequency changing knobs. I have not flown a -200 in a long time and fell victim to this 'classic' gotcha. No harm was done but I felt an as soon as possible report was due as this is a bad design for the radio. Supplemental information from acn 525281: leg into mdw with the captain flying. I checked in with ZAU with a good response and set up VHF #1 for the next frequency change. I told the captain I would be off to get the WX (ATIS), which I did. I knew we had a crossing restr coming up and was monitoring the DME (-200) for descent. When I came back, the captain was apparently having difficulty contacting ATC as he also was watching the descent point (which had come and gone). He realized the volume knob was turned down and corrected it. ATC gave us a vector to help us make the awsum at 10000 ft restr. The rest was uneventful.

Original NASA ASRS Text

Title: B737-200 CAPT ACCIDENTALLY TURNED THE VOLUME DOWN ON HIS COM RADIO.

Narrative: ZAU FREQ 135.9 OVER GSH VOR ON THE GSH.GHS3 ARR. I WAS PF, FO WAS OFF FREQ ON VHF #2 GETTING MDW ATC. I ASKED ATC FOR A DSCNT CLRNC. I ASKED IF THEY WANTED US TO CROSS AWSUM AT 10000 FT. THERE WAS NO REPLY, SO I CHKED THE RADIO VOLUME AND TURNED IT UP. ATC WAS CALLING US AND WE WERE GIVEN OUR CLRNC TO DSND AND WE EXPEDITED OUR DSCNT. THE B737-200 IS DIFFERENT FROM THE OTHER MODELS WE FLY IN THAT THE RADIO VOLUME CTL IS TOP ON A STACK OF KNOBS THAT ALSO CHANGE THE FREQ. IT IS EASY TO INADVERTENTLY REDUCE THE VOLUME AS IT DOESN'T HAVE DETENT 'STEPS' LIKE THE FREQ CHANGING KNOBS. I HAVE NOT FLOWN A -200 IN A LONG TIME AND FELL VICTIM TO THIS 'CLASSIC' GOTCHA. NO HARM WAS DONE BUT I FELT AN ASAP RPT WAS DUE AS THIS IS A BAD DESIGN FOR THE RADIO. SUPPLEMENTAL INFO FROM ACN 525281: LEG INTO MDW WITH THE CAPT FLYING. I CHKED IN WITH ZAU WITH A GOOD RESPONSE AND SET UP VHF #1 FOR THE NEXT FREQ CHANGE. I TOLD THE CAPT I WOULD BE OFF TO GET THE WX (ATIS), WHICH I DID. I KNEW WE HAD A XING RESTR COMING UP AND WAS MONITORING THE DME (-200) FOR DSCNT. WHEN I CAME BACK, THE CAPT WAS APPARENTLY HAVING DIFFICULTY CONTACTING ATC AS HE ALSO WAS WATCHING THE DSCNT POINT (WHICH HAD COME AND GONE). HE REALIZED THE VOLUME KNOB WAS TURNED DOWN AND CORRECTED IT. ATC GAVE US A VECTOR TO HELP US MAKE THE AWSUM AT 10000 FT RESTR. THE REST WAS UNEVENTFUL.

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.