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To file flight plans, an aircraft's transponder and ADS-B codes must be defined. This article describes the codes and provides examples of code designations for select avionics systems.

To define the Surveillance codes for an aircraft, do the following:

1. Open ForeFlight Mobile.
2. Go to More.
3. Select Aircraft.
4. Tap on the Aircraft Profile to edit.
5. Scroll down to the Filing section.
6. Select the desired field: ICAO Surveillance or Other Information.

Once the aircraft codes have been defined, when filing a flight plan, the designated codes will be included.

Transponder Codes

ATC requires a transponder code to be included in the ICAO Surveillance field to file a flight plan. The most common codes used are A, C, E, S, L, and N. The transponder codes available are listed in the following table:

CODE	DESCRIPTION
A	Mode A - no altitude (no Mode C)
C	Modes A and C
S	Mode S - Aircraft ID and Altitude
P	Mode S - Altitude, no Aircraft ID
I	Mode S - Aircraft ID, no Altitude
X	Mode S - no Aircraft ID, no Altitude
E	Mode S - Aircraft ID, Altitude, Extended Squitter (most ADS-B Out transponders are this code)
H	Mode S - Aircraft ID, Altitude, Enhanced Surveillance
L	Mode S - Aircraft ID, Altitude, Enhanced Surveillance, Extended Squitter
N	Nil (no transponder)

 

ADS-B Codes

All aircraft equipped with Automatic Dependent Surveillance-Broadcast (ADS-B) must include the appropriate code in addition to the transponder code.

If a flight plan is filed with only an ADS-B code and does not include a transponder code, the flight plan will be rejected. For example, E (transponder code) and B2 (AD-B code) together are acceptable, but B2 alone is not. Only one ADS-B code may be used. For example, using B2 is acceptable, but using B2 and U2 together is not. 

The most common ADS-B codes for general aviation are B1, B2, U1, and U2. The full list of codes is listed in the following table.

CODE	DESCRIPTION
B1	ADS-B Out capable transponder (dedicated 1090)
B2	1090 MHz “out” and “in”  ADS-B Out+In capable transponder (dedicated 1090)
U1	UAT “out” ADS-B Out capable system (dedicated 978 UAT)
U2	UAT “out” and “in” ADS-B Out+In capable system (dedicated 978 UAT)
V1	ADS-B Out only using VDL Mode 4
V2	ADS-B Out+In using VDL Mode 4
If the aircraft is equipped with ADS-C, also choose one of the following:
D1	ADS-C with FANS 1/A capability
G1	ADS-C with ATN capabilities

ADS-B Out transponders are all 1090ES, and UAT Systems are all 978 MHz out. There are no dual-band ADS-B Out systems on the market. The Out is what is specified and mandated, the In may only be specified if there is an Out of the same frequency. Aircraft equipped with 1090ES transponders are authorized to fly at all altitudes. 978 UAT systems are not permitted above 18,000 feet.

 

Other Information Field

Apart from the code used for ADS-B Out, two additional fields labeled "CODE" and "SUR" in the "Other Information" section should be defined. However, these fields are not mandatory.

CODE

The CODE field is where you input the assigned hexadecimal value obtained from the FAA registry. This value is unique to the registration (N number) and is consistently transmitted by ADS-B Out systems. Its inclusion optimizes the FAA's link between the filed flight plan and the ADS-B Out, minimizing the need for transponder code reassignment when flying in proximity to other aircraft sharing the same transponder code.

SUR

The SUR is used to indicate that the ADS-B Out is of the variety that is 2020 compliant. This allows routing into airspace or along routes that only ADS-B Out equipped aircraft are permitted. If there is a radar outage, a direct route through the outage area may still be given. Some routes will not be assigned unless the aircraft has this code set.

There are two values used for the SUR code:

• 260B for 1090ES
• 282B for UAT

Examples of Transponder and ADS-B Codes

The following section presents codes for non-ADS-B Out compliant transponders and ADS-B Out compliant transponders.

Non-ADS-B Out Compliant Transponders

Garmin

Hardware	Applicable Transponder Code
GTX327	C
GTX328	S
GTX330/33

 

Honeywell Bendix King Transponders

Hardware	Applicable Transponder Code
KT 73	S
KT 76A	C
KT 76C

 

ADS-B Out Transponders (1090ES)

Avidyne Transponder   

Hardware	Transponder Code, ADS-B Code, and Other Information Code
AXP340	E, B1, and SUR/260B
AXP322

 

Collins    

Hardware	Transponder Code, ADS-B Code, and Other Information Code
TDR-94-94D  (501 and 502 only)	E, B1, and SUR/260B

 

Garmin

Hardware	Transponder Code, ADS-B Code, and Other Information Code
GTX330ES/33ES	E, B1, and SUR/260B
GTX335
GTX345	E, B2, and SUR/260B
GTX345/R
G375 GPS/Transponder
GTX-3000	L, B1, and SUR/260B

 

Honeywell Bendix King

Hardware	Transponder Code, ADS-B Code, and Other Information Code
KT 74	E, B1, and SUR/260B

 

L3 Transponders

Hardware	Transponder Code, ADS-B Code, and Other Information Code
Lynx NGT-9000	E, B2, and SUR/260B

 

Stratus

Hardware	Transponder Code, ADS-B Code, and Other Information Code
Stratus ESG	E, B1, and SUR/260B

 

Trig

Hardware	Transponder Code, ADS-B Code, and Other Information Code
TT31	E, B1, and SUR/260B

 

ADS-B Out UAT Systems (978 MHz)

FreeFlight UAT Systems

Hardware	Transponder Code, ADS-B Code, and Other Information Code
Ranger 978 XVR with mode A/C	C, U2, and SUR/282B
Ranger Lite with mode A/C	C, U1, and SUR/282B

 

Garmin UAT Systems:

Hardware	Transponder Code, ADS-B Code, and Other Information Code
GDL82 with Mode A/C	C, U1, and SUR/282B
GDL88/84 with Mode A/C	C, U2, and SUR/282B
GDL88/84 wMode S	S, U2, and SUR/282B

 

L3 UAT Systems

Hardware	Transponder Code, ADS-B Code, and Other Information Code
Lynx NGT 1000	C, U1, and SUR/282B
Lynx NGT- 2000/2500	C, U2, and SUR/282B

 

uAvionix UAT Systems:

Hardware	Transponder Code, ADS-B Code, and Other Information Code
SkyBeacon	C, U1, and SUR/282B
Tail Beacon
Echo UAT -	C, U2, and SUR/282B

 

References

• Aeronautical Information Manual 4-5-7 thru 4-5-9
• FAA ICAO Equipment Code Definitions (PDF)
• Part 91.225