Narrative:

While in sequence for takeoff on runway 18L at dfw airport we listened to the tower issue the clearance 'at the marker, fly heading 185.' we did not think much of the clearance initially. We adjusted the brightness on our marker lights and turned up the volume. We received the same clearance and pressed on our way. While waiting for our brightness on our marker lights and turned up the volume. We received the same clearance and pressed on our way. While waiting for our turn for takeoff we looked at the SID to see if the marker was depicted and it was not. We thought there probably ought to be a DME cross reference/radial reference to backup the marker if they are going to issue such a clearance. This would be beneficial to aircraft that were not marker equipped or had inoperative equipment. As it was, we did not get a marker light indication in our aircraft but we did get the aural tone. Had we forgotten to turn up the volume it could have resulted in a late turn and possible confusion. The congested dfw frequencys would make it difficult to resolve any confusion that may have resulted. Of course, if an aircraft received this clearance and could not comply (no equipment/inoperative equipment) they would request an alternate clearance. But once again, with dfw's congested frequencys this is not a simple task. If this is to be a regularly used clearance, a good solution would be to depict the marker on the SID with a DME or radial cross reference to co-identify the fix position. A lot of sids already are cluttered with information but confusion at low altitude, on departure, and with parallel departures should be avoided if at all possible. Callback conversation with reporter revealed the following information: the dfw tower pps stated the marker turn is issued for noise abatement. The phraseology is supposed to be 'at the MM fly heading.' pps said he would put out a memo reminding controller's to use the word middle when using this procedure.

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Original NASA ASRS Text

Title: POOR ATC PHRASEOLOGY FOR DEP CLRNC.

Narrative: WHILE IN SEQUENCE FOR TKOF ON RWY 18L AT DFW ARPT WE LISTENED TO THE TWR ISSUE THE CLRNC 'AT THE MARKER, FLY HDG 185.' WE DID NOT THINK MUCH OF THE CLRNC INITIALLY. WE ADJUSTED THE BRIGHTNESS ON OUR MARKER LIGHTS AND TURNED UP THE VOLUME. WE RECEIVED THE SAME CLRNC AND PRESSED ON OUR WAY. WHILE WAITING FOR OUR BRIGHTNESS ON OUR MARKER LIGHTS AND TURNED UP THE VOLUME. WE RECEIVED THE SAME CLRNC AND PRESSED ON OUR WAY. WHILE WAITING FOR OUR TURN FOR TKOF WE LOOKED AT THE SID TO SEE IF THE MARKER WAS DEPICTED AND IT WAS NOT. WE THOUGHT THERE PROBABLY OUGHT TO BE A DME CROSS REF/RADIAL REF TO BACKUP THE MARKER IF THEY ARE GOING TO ISSUE SUCH A CLRNC. THIS WOULD BE BENEFICIAL TO ACFT THAT WERE NOT MARKER EQUIPPED OR HAD INOP EQUIP. AS IT WAS, WE DID NOT GET A MARKER LIGHT INDICATION IN OUR ACFT BUT WE DID GET THE AURAL TONE. HAD WE FORGOTTEN TO TURN UP THE VOLUME IT COULD HAVE RESULTED IN A LATE TURN AND POSSIBLE CONFUSION. THE CONGESTED DFW FREQS WOULD MAKE IT DIFFICULT TO RESOLVE ANY CONFUSION THAT MAY HAVE RESULTED. OF COURSE, IF AN ACFT RECEIVED THIS CLRNC AND COULD NOT COMPLY (NO EQUIP/INOP EQUIP) THEY WOULD REQUEST AN ALTERNATE CLRNC. BUT ONCE AGAIN, WITH DFW'S CONGESTED FREQS THIS IS NOT A SIMPLE TASK. IF THIS IS TO BE A REGULARLY USED CLRNC, A GOOD SOLUTION WOULD BE TO DEPICT THE MARKER ON THE SID WITH A DME OR RADIAL CROSS REF TO CO-IDENT THE FIX POS. A LOT OF SIDS ALREADY ARE CLUTTERED WITH INFO BUT CONFUSION AT LOW ALT, ON DEP, AND WITH PARALLEL DEPS SHOULD BE AVOIDED IF AT ALL POSSIBLE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE DFW TWR PPS STATED THE MARKER TURN IS ISSUED FOR NOISE ABATEMENT. THE PHRASEOLOGY IS SUPPOSED TO BE 'AT THE MM FLY HDG.' PPS SAID HE WOULD PUT OUT A MEMO REMINDING CTLR'S TO USE THE WORD MIDDLE WHEN USING THIS PROC.

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.