What are the transponder, pitot-static, and ELT inspection requirements?
Updated · Wingman AeroCare, KFNL
Short answer: Three separate recurring checks apply to most piston airplanes. The transponder must be tested every 24 calendar months under 14 CFR 91.413; the static system, altimeter, and altitude reporting system must be tested every 24 calendar months to fly IFR in controlled airspace under 14 CFR 91.411; and the ELT must be inspected every 12 calendar months under 14 CFR 91.207(d). Each has its own due date, separate from your annual.
At a glance
| Check | Rule | Interval | Applies when |
|---|---|---|---|
| Transponder | 14 CFR 91.413, tested to Part 43 Appendix F | 24 calendar months | Any use of an installed transponder, VFR or IFR |
| Altimeter, static system, altitude reporting | 14 CFR 91.411, tested to Part 43 Appendix E | 24 calendar months | IFR flight in controlled airspace |
| ELT inspection | 14 CFR 91.207(d) | 12 calendar months | Most U.S.-registered civil airplanes |
| ELT battery | 14 CFR 91.207(c) | Per manufacturer's date, or after 1 cumulative hour of use | Same |
"Calendar months" means the check stays valid through the last day of the month it comes due. A test done March 3, 2025 for a 24-month item is good through March 31, 2027.
Transponder check (14 CFR 91.413)
You may not use an ATC transponder that meets the equipment standards in 14 CFR 91.215(a) (in practice, any transponder installed in a U.S.-registered civil aircraft) unless, within the preceding 24 calendar months, it has been tested and inspected and found to comply with Part 43, Appendix F (14 CFR 91.413(a)). Under 14 CFR 91.215(b), a transponder is required in most airspace around busy airports and in Class E at and above 10,000 feet MSL (excluding the airspace at and below 2,500 feet AGL), so nearly every owner needs this check whether or not they fly IFR.
After any installation or maintenance on a transponder where a data correspondence error could be introduced, the integrated system must also be tested to Appendix E, paragraph (c) (14 CFR 91.413(b)).
Under 14 CFR 91.413(c), the test must be done by an appropriately rated repair station, certain air carriers under their maintenance programs, or the aircraft manufacturer for transponders it installed. A typical A&P cannot perform it alone.
Altimeter and static system check (14 CFR 91.411)
You may not operate an airplane in controlled airspace under IFR unless, within the preceding 24 calendar months, each static pressure system, each altimeter instrument, and each automatic pressure altitude reporting system has been tested and inspected and found to comply with Part 43, Appendix E.
The static system must also be retested after it is opened and closed, except when only the system drain or alternate static pressure valve is used (14 CFR 91.411(a)(2)). This matters after avionics work: installing a new instrument or ADS-B unit often means the static system was opened.
Who may do it (14 CFR 91.411(b)): the manufacturer, an appropriately rated repair station, or, for the static pressure system tests and inspections only, a certificated mechanic with an airframe rating.
VFR-only aircraft: the 91.411 certification is not legally required if you never fly IFR in controlled airspace. Many owners do it anyway alongside the transponder check, because the altitude encoder correspondence is checked in the process and the aircraft stays IFR-ready.
ELT inspection and battery (14 CFR 91.207)
Under 14 CFR 91.207(d), each ELT must be inspected within 12 calendar months after its last inspection for:
- Proper installation
- Battery corrosion
- Operation of the controls and crash sensor
- Presence of a sufficient signal radiated from its antenna
Under 14 CFR 91.207(c), ELT batteries must be replaced (or recharged, if rechargeable) when the transmitter has been in use for more than 1 cumulative hour, or when 50 percent of the battery's useful life (as established by the ELT manufacturer) has expired. The new expiration date must be legibly marked on the outside of the transmitter and entered in the maintenance records.
There are limited exceptions in 14 CFR 91.207(f), for example training operations conducted entirely within 50 nautical miles of the airport where they began, aircraft equipped to carry only one person, and up to 90 days while the ELT is removed for repair. Separately, 14 CFR 91.207(e) allows a ferry flight to a place where an ELT can be installed or repaired, with only required crewmembers aboard. Most owners should assume the requirement applies.
A note on 121.5 vs. 406 MHz: satellite monitoring of 121.5 MHz ended in 2009. The FAA does not currently require a 406 MHz ELT for Part 91 operations, but a 406 MHz unit is far more likely to get search and rescue to you quickly.
How do I keep these straight?
Write all three due dates on the same page as your annual and AD list. Many owners line up the transponder and altimeter checks with the annual so the aircraft goes down once. Just remember each item keeps its own clock.
How Wingman handles it
Wingman AeroCare coordinates pitot-static, transponder, and ELT compliance for piston aircraft at Northern Colorado Regional Airport (KFNL), and we check all three due dates at every annual. If something is coming due, it shows up on your online estimate so you can approve it with everything else. Members of our Managed Maintenance Program get these dates tracked to the tail number. See avionics services or call (970) 292-0719.