Subchapter 10.5 – Common Readback Errors and Exam Traps

The Trap: You may not abbreviate your callsign until ATC abbreviates it first. Some pilots abbreviate too early.

Your full callsign is "OE-DMS."

Wrong: On the first call, "Oscar Echo Delta Mike Sierra, request engine start." Then responding with: "DMS, roger."

Correct: On the first call, "OE-DMS, request engine start" (company/national prefix + number or letters). Then, ATC may say: "DMS, engine start approved." Then you respond: "DMS, WILCO." (Now you can abbreviate.)

Rule: Use your full callsign until ATC abbreviates it. Then you may abbreviate the same way ATC did.