Transponder, ADS-B & radar services

Primary radar sees a smudge. Your transponder turns it into a target with an identity and an altitude — the difference between a traffic call and silence.

codes worth knowing cold

Set 1200 for VFR unless ATC assigns something else. Three emergency codes matter:

They sit next to each other, so change codes deliberately — never scroll past 7500.

Mode C adds pressure altitude, which gives other pilots your altitude and makes traffic alerts work. Ident highlights you on the scope — press it when asked.

where the equipment is required

§91.215 lists the transponder-with-Mode-C airspace; §91.225 puts ADS-B Out in essentially the same places:

• All Class A, B, and C airspace
• Within 30 NM of a Class B primary airport, surface to 10,000 MSL — the Mode C veil
• Above the ceiling and within the lateral boundaries of Class B or C, up to 10,000 MSL
• Above 10,000 MSL in the 48 states, excluding airspace at and below 2,500 AGL

The one people miss: over high terrain, above 10,000 MSL you can still be within 2,500 feet AGL.

An airplane never certificated with an engine-driven electrical system — a Cub — may fly outside the veil and below the Class B/C shelves without either box. Transponder failed? Request a deviation from ATC, generally an hour ahead.

ADS-B In is the half nobody requires and everybody wants: FIS-B weather and TIS-B traffic in the cockpit, free, on 978 UAT. Both advisory — FIS-B radar imagery is minutes old, fine strategically, dangerous tactically near a thunderstorm.

flight following, honestly

VFR radar advisories cost one radio call and are worth taking on any cross-country: call approach or center with who and where you are, your altitude, and your destination. They're workload permitting — controllers drop advisories when busy, usually when the airspace is most complex. Plan so losing it changes nothing.

You get traffic calls and a controller who knows your position if things go wrong. You do not get separation — "radar contact" means identified, not protected. You stay responsible for see-and-avoid §91.113, terrain, and airspace: "remain outside Class Charlie" means exactly that, and Class B takes "cleared into the Bravo."

Worked example. Twenty miles from the Class C shelf: "Albuquerque Approach, Skyhawk one-two-three-four-five, two-zero miles northwest of Double Eagle, six thousand five hundred, request flight following to Santa Fe." Approach: "squawk four-five-six-two," then "radar contact." You're identified, not separated — so when they call "traffic, one o'clock, four miles, opposite direction, altitude indicates six thousand," you look, find it, answer "traffic in sight."