4.3 Fuel Requirements, Transponder, ADS-B, and ELT

A legal VFR cross-country can still be a 91.151, 91.215, 91.225, or 91.207 bust. The knowledge test writes each rule as a separate item. Do not let “I have a Mode C transponder with ADS-B and a 406 ELT” collapse into one imaginary “required equipment” blob.

Airplane VFR fuel — 91.151

No person may begin a flight in an airplane under VFR unless, considering wind and forecast weather, there is enough fuel to fly to the first point of intended landing and, assuming normal cruising speed:

• during the day, to fly after that for at least 30 minutes; or
• at night, to fly after that for at least 45 minutes.

The reserve is after the first intended landing, not after a string of optional fuel stops you might make if the wind is worse than planned. The clock starts when you would arrive at that first airport at normal cruise. Day versus night is the civil-twilight definition used throughout the FARs, not “whenever I turn the landing light on.”

Wind is in the regulation. A still-air 90-minute tank that becomes a 100-minute flight into a forecast headwind is not a 91.151 flight, even if the still-air numbers showed 30 minutes extra. Forecast weather that forces a longer routing is the same problem.

91.151(b) gives rotorcraft a 20-minute VFR reserve. That is not the airplane answer. IFR reserve (91.167) is a different rule: destination, then most distant alternate if one is required, then 45 minutes at normal cruise. Do not import 91.167 into a VFR stem.

Beginning the flight is the test. Burning into the reserve after an unforecast headwind is a judgment and 91.13 problem; launching without the reserve already in the tanks is the 91.151 violation.

Transponder and Mode C — 91.215

Unless ATC authorizes otherwise, you may not operate in the airspace below unless the airplane has an operable transponder (Mode A 4096-code or Mode S) and automatic pressure-altitude reporting with Mode C (100-foot increments).

91.215(b) applies to:

1. All aircraft in Class A, Class B, and Class C.
2. All aircraft within 30 nautical miles of an airport listed in appendix D, section 1 (the primary Class B airports) from the surface up to 10,000 feet MSL — the Mode C veil.
3. A narrow exception inside that veil for aircraft never certificated with an engine-driven electrical system, balloons, and gliders, if they stay outside Class A/B/C and below the Class B or C ceiling or 10,000 MSL, whichever is lower.
4. All aircraft above the ceiling and within the lateral boundaries of a Class B or Class C area, up to 10,000 MSL.
5. All aircraft (except no-electrical-system aircraft, balloons, and gliders) in the 48 contiguous states and the District of Columbia at and above 10,000 MSL, excluding airspace at and below 2,500 feet AGL; plus a smaller 10-NM Mode C ring around certain appendix D, section 2 airports.

The PAR picture is the veil and the 10,000-foot / 2,500-AGL carvedown. Flying 10,500 MSL over the plains requires Mode C. Flying 9,500 MSL in Class E outside B/C/veil does not, unless some other paragraph catches you. Flying 10,500 MSL but only 2,000 AGL along a mountain ridge is inside the 2,500-AGL exclusion.

If the airplane has an operable transponder maintained under 91.413, 91.215(c) requires you to operate it, including Mode C if installed, in the (b) airspace and in all controlled airspace, unless ATC directs otherwise. Having the box and leaving it off in Class E is the trap.

ATC deviations: inoperative Mode C but working transponder — request anytime. Inoperative transponder to destination or a repair station — request anytime. No transponder installed — request at least one hour before the proposed operation.

ADS-B Out — 91.225 (current text)

After January 1, 2020, unless ATC authorizes otherwise, ADS-B Out is required in the airspace 91.225(d) lists. In practice that is the 91.215 Mode C map plus one extra shelf:

• Class A (and in Class A the equipment must be 1090ES, TSO-C166b or TSO-C166c — Universal Access Transceiver is not a Class A solution).
• Class B and Class C.
• Within 30 NM of an appendix D, section 1 airport from the surface to 10,000 MSL (the same veil).
• Above the ceiling and within the lateral boundaries of Class B or C up to 10,000 MSL.
• Class E in the 48 contiguous states and D.C. at and above 10,000 MSL, excluding at and below 2,500 AGL.
• Class E at and above 3,000 MSL over the Gulf of Mexico from the U.S. coastline out to 12 nautical miles — this Gulf shelf is in 91.225 and is not a 91.215 paragraph.

Below 18,000 MSL, either 1090ES or 978 MHz UAT (TSO-C154c or TSO-C154d) satisfies 91.225. The performance rule is 91.227 (the “ADS-B Out works and reports the right data” rule). Aircraft never certificated with an engine-driven electrical system, including balloons and gliders, may skip ADS-B in the at-or-above-10,000 Class E airspace, and may operate in the veil outside B/C and below the B/C ceiling or 10,000, whichever is lower.

If ADS-B Out is installed, transmit. 91.225(f) requires each person operating an aircraft equipped with ADS-B Out to operate it in the transmit mode at all times unless the FAA authorizes otherwise for a listed sensitive government mission or ATC directs otherwise because transmitting would jeopardize ATC. Installing the box and switching it off is not a private-pilot option.

Deviations track the transponder idea: inoperative ADS-B Out to destination or repair — request anytime. Not equipped — request at least 1 hour before the proposed operation.

Emergency locator transmitter — 91.207

Except as provided in 91.207(e) and (f), no person may operate a U.S.-registered civil airplane unless an approved ELT is attached and operable. For typical part 91 operations that ELT may be a personal type or an automatic type (TSO-C91 may not be used for new installations after June 21, 1995). Attach it so crash impact is unlikely to destroy it; fixed and deployable automatic units go as far aft as practicable.

Batteries must be replaced or, if rechargeable, recharged:

• when the transmitter has been in use for more than 1 cumulative hour; or
• when 50 percent of useful life (or, for rechargeable batteries, 50 percent of useful life of charge) has expired, as established by the manufacturer.

Mark the new expiration date on the transmitter and enter it in the aircraft maintenance record. Water-activated batteries that are essentially unaffected in storage are exempt from the 50-percent clock.

Inspection — 91.207(d). Each required ELT must be inspected within 12 calendar months after the last inspection for proper installation, battery corrosion, operation of the controls and crash sensor, and a sufficient signal from its antenna.

Ferry exceptions — 91.207(e). You may ferry a newly acquired airplane to the place the ELT will be installed, or ferry an airplane with an inoperative ELT from a place that cannot repair it to a place that can. Only required crewmembers may be carried.

91.207(f) exceptions — paragraph (a) does not apply to, among others:

• aircraft on scheduled air-carrier flights;
• aircraft on training operations conducted entirely within a 50-nautical-mile radius of the airport from which those local flight operations began;
• design-and-test, new-manufacture delivery, agricultural application, research-and-development, showing-compliance / crew-training / exhibition / air-racing / market-survey flights;
• aircraft equipped to carry not more than one person;
• temporary removal for inspection, repair, modification, or replacement, with a logbook entry (date, make, model, serial number, reason), a “ELT not installed” placard in view of the pilot, and no more than 90 days after the ELT was first removed.

The 50-NM training exception is the PAR classic. Dual in the practice area around the home airport fits. A 60-NM dual cross-country does not, even if you call it training. The exception is about the radius of that local flight, not about whether a CFI is on board.