Narrative:

On departure from runway 22L at midway, the vors were set to moline, the first outbound fix, and the #2 DME was on hold for the 31C localizer. This was to check that the initial turn was made within 4 NM, as required by the midway 4 SID. After our initial turn to 250 degrees, we contacted chicago departure and were assigned a heading of 290 degrees and cleared to climb from 2000 ft to 4000 ft. At some point during the climb, or perhaps after reaching 4000 ft, I reached down to de-select the DME hold. Things were pretty busy at this point, as there were a lot of aircraft on the frequency, and we were in solid IMC and icing conditions. Shortly afterward, I noticed that the controling agency on the frequency was midway tower. I looked at the radio control heads and discovered that the communication had been transferred back to the #2 radio, which still had the tower frequency set in it. I reselected departure and a moment later the controller called us with a climb clearance. His tone indicated that perhaps he had already tried to contact us, although he didn't sound upset. While puzzling over how we had gotten off frequency, I noticed that the DME hold annunciator on the instrument panel was still illuminated. Looking down at the VOR control head, I realized that when I went to push the DME hold button to de-select hold, I had actually pushed the next one to the left of it, which looks just like it, but is the button that transfers communication from the #3 to the #2. I was shocked to find that through a momentary lapse of attention, I had rendered myself incommunicado in the chicago class B airspace on a busy IFR day. The cockpit workload was high at the time, and there was no urgency to get the DME on moline. I could have waited till things settled down (the word 'prioritize' echoes from past instructors). Also, I realized later, this was my first flight in the right seat of this type of aircraft in 2 months. I'm sure momentary unfamiliarity with the controls due to a lack of recent experience with them was a major contributor to this incident. (Most of my recent flying has been in a similar aircraft, albeit with different radio controls.)

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Original NASA ASRS Text

Title: CAPT OF AN MLG CPR JET ACFT INADVERTENTLY SWITCHED OFF OF DEP FREQ RESULTING IN MOMENTARY LOSS OF COM.

Narrative: ON DEP FROM RWY 22L AT MIDWAY, THE VORS WERE SET TO MOLINE, THE FIRST OUTBOUND FIX, AND THE #2 DME WAS ON HOLD FOR THE 31C LOC. THIS WAS TO CHK THAT THE INITIAL TURN WAS MADE WITHIN 4 NM, AS REQUIRED BY THE MIDWAY 4 SID. AFTER OUR INITIAL TURN TO 250 DEGS, WE CONTACTED CHICAGO DEP AND WERE ASSIGNED A HDG OF 290 DEGS AND CLRED TO CLB FROM 2000 FT TO 4000 FT. AT SOME POINT DURING THE CLB, OR PERHAPS AFTER REACHING 4000 FT, I REACHED DOWN TO DE-SELECT THE DME HOLD. THINGS WERE PRETTY BUSY AT THIS POINT, AS THERE WERE A LOT OF ACFT ON THE FREQ, AND WE WERE IN SOLID IMC AND ICING CONDITIONS. SHORTLY AFTERWARD, I NOTICED THAT THE CTLING AGENCY ON THE FREQ WAS MIDWAY TWR. I LOOKED AT THE RADIO CTL HEADS AND DISCOVERED THAT THE COM HAD BEEN TRANSFERRED BACK TO THE #2 RADIO, WHICH STILL HAD THE TWR FREQ SET IN IT. I RESELECTED DEP AND A MOMENT LATER THE CTLR CALLED US WITH A CLB CLRNC. HIS TONE INDICATED THAT PERHAPS HE HAD ALREADY TRIED TO CONTACT US, ALTHOUGH HE DIDN'T SOUND UPSET. WHILE PUZZLING OVER HOW WE HAD GOTTEN OFF FREQ, I NOTICED THAT THE DME HOLD ANNUNCIATOR ON THE INST PANEL WAS STILL ILLUMINATED. LOOKING DOWN AT THE VOR CTL HEAD, I REALIZED THAT WHEN I WENT TO PUSH THE DME HOLD BUTTON TO DE-SELECT HOLD, I HAD ACTUALLY PUSHED THE NEXT ONE TO THE L OF IT, WHICH LOOKS JUST LIKE IT, BUT IS THE BUTTON THAT TRANSFERS COM FROM THE #3 TO THE #2. I WAS SHOCKED TO FIND THAT THROUGH A MOMENTARY LAPSE OF ATTN, I HAD RENDERED MYSELF INCOMMUNICADO IN THE CHICAGO CLASS B AIRSPACE ON A BUSY IFR DAY. THE COCKPIT WORKLOAD WAS HIGH AT THE TIME, AND THERE WAS NO URGENCY TO GET THE DME ON MOLINE. I COULD HAVE WAITED TILL THINGS SETTLED DOWN (THE WORD 'PRIORITIZE' ECHOES FROM PAST INSTRUCTORS). ALSO, I REALIZED LATER, THIS WAS MY FIRST FLT IN THE R SEAT OF THIS TYPE OF ACFT IN 2 MONTHS. I'M SURE MOMENTARY UNFAMILIARITY WITH THE CTLS DUE TO A LACK OF RECENT EXPERIENCE WITH THEM WAS A MAJOR CONTRIBUTOR TO THIS INCIDENT. (MOST OF MY RECENT FLYING HAS BEEN IN A SIMILAR ACFT, ALBEIT WITH DIFFERENT RADIO CTLS.)

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.