En route
SSR (transponder) instructions
Understand and read back transponder instructions.
Original SkyRT lesson (pending instructor review)squawktransponder
When you use it
Whenever ATC assigns a code or asks you to operate the transponder.
Example exchange
ATCNarmada Control
VKA, squawk 4521
You
Squawk 4521, VKA
ATCNarmada Control
VKA, squawk ident
You
Squawk ident, VKA
This is an illustrative example. The required elements matter more than the exact words — ICAO phraseology allows variation, and local procedures can differ.
Required information
- Code (read back)
- Call sign
Expected sequence
- SQUAWK + code
- Call sign
Read back
- SSR code
Why it works this way
SSR codes are mandatory read-back items (Doc 9432 §2.8.3.5); other SSR instructions are acknowledged or read back (§6.5.2). SQUAWK IDENT means operate the IDENT feature; SQUAWK STANDBY means select standby. Special codes: 7700 emergency, 7600 radio communication failure (§9.5.5), 7500 unlawful interference (PANS-OPS, Doc 8168).
Common errors
- Passing through 7500/7600/7700 when changing codes
- Reading back a code with an 8 or 9 (SSR codes use digits 0–7)
References
- ICAO Doc 9432, Manual of Radiotelephony (4th ed., 2007), §6.5 — Secondary surveillance radar
- icao-doc-8168, Vol III, Sect. 4, Ch. 1 — Mode A codes 7500/7600/7700
Practise it: Transfer, position report and descent
Run the related simulator scenario and get item-by-item feedback on your transmissions.
Open the scenario