ELT, Transponder, and Pitot-Static Inspection Cycles: What GA Pilots Need to Track

Every GA owner knows about the annual inspection. It’s the big one — the event your entire maintenance year revolves around. But lurking alongside it are three other recurring inspections that don’t follow the annual’s calendar and are easy to lose track of: your ELT inspection, your transponder check, and your pitot-static system test.

Each is governed by a different section of the Federal Aviation Regulations. Each has its own interval. And each can ground you if it lapses — sometimes without you even realizing it until you’re reviewing your records or getting a ramp check.

The three inspections at a glance

Before we dig into the details, here’s the summary. These are the regulatory requirements for Part 91 operations:

• ELT — 14 CFR 91.207(d). Interval: 12 calendar months. May be performed by an A&P mechanic or other person authorized under 14 CFR 43.3 — a certificated repair station is not required.
• Transponder — 14 CFR 91.413. Interval: 24 calendar months. Must be performed by a certificated repair station with appropriate ratings.
• Pitot-Static — 14 CFR 91.411. Interval: 24 calendar months (IFR only). Must be performed by a certificated repair station with appropriate ratings.

Notice the differences. The ELT is on a 12-month cycle; the transponder and pitot-static tests are on 24-month cycles. The pitot-static test is only required for IFR flight, while the transponder check applies regardless of flight rules (if you’re operating in airspace where a transponder is required). And none of these necessarily align with your annual inspection date.

ELT: the 12-month inspection

Under 14 CFR 91.207(d), your Emergency Locator Transmitter must be inspected within the preceding 12 calendar months. The inspection verifies that the ELT is properly installed, that its battery has adequate charge, and that the unit will activate on impact as designed. The battery must also be replaced (or recharged, for rechargeable types) when 50% of its useful life has expired, or after one cumulative hour of use.

Most owners have their ELT inspected at annual, which is a natural fit since they’re both on 12-month cycles. But here’s where it gets tricky: if your annual date shifts — say you bring it in two months early one year — your ELT inspection date shifts with it. If you’re not tracking them independently, you might assume the ELT is good through your next annual when it actually expires earlier.

Practical tip: Even though many A&Ps inspect the ELT during the annual, track it as a separate line item with its own due date. That way, if your annual date ever shifts, you won’t accidentally fly past the ELT inspection window.

Transponder: the 24-month check

Under 14 CFR 91.413, no person may use an ATC transponder unless it has been tested and inspected within the preceding 24 calendar months. This applies to all transponder-equipped aircraft operating in airspace where a transponder is required — which, for most GA pilots flying near any towered airport or in Class B, C, or above 10,000 feet MSL, means it applies to you.

The transponder check verifies output power, frequency accuracy, mode and code operation, suppression characteristics, and (for Mode C or ADS-B Out) altitude reporting accuracy. It must be performed by a certificated repair station holding the appropriate instrument rating, or by an appropriately rated manufacturer.

Because it’s a 24-month cycle, the transponder check doesn’t align with annual inspections. If your transponder was checked in January 2025, it’s due again by the end of January 2027. That has nothing to do with when your annual falls. Many owners bundle it with the pitot-static test since they’re on the same interval, which can save on shop time and avionics bench fees.

Pitot-static: the IFR requirement

Under 14 CFR 91.411, each altimeter, encoding altimeter, and static pressure system must be tested and inspected within the preceding 24 calendar months before the aircraft can be used for IFR flight. The key phrase there is “used under IFR.” If you fly VFR only, this test is not required by regulation.

However, even VFR-only pilots should consider the practical implications. Your altimeter and static system are what give you accurate altitude readings. A static system leak might not set off any warning — you’ll just get slightly wrong altitude and airspeed indications, which in marginal VFR conditions could be a real problem.

The test checks for leaks in the static system, verifies altimeter accuracy at multiple pressure settings, and confirms that altitude encoding (the altitude your transponder reports to ATC) matches your altimeter within allowable tolerances. The tolerance is generally ±125 feet, as specified in 14 CFR Part 43, Appendix E.

Common pitfall: You file IFR for the first time in months. Everything looks good in the cockpit. But your pitot-static test expired three months ago. Technically, you cannot legally fly that IFR trip — even though all the instruments seem to work fine. This is the kind of compliance gap that shows up at the worst time: during an insurance review, a pre-buy inspection, or a ramp check by the FSDO.

Why these inspections fall through the cracks

The annual inspection is easy to remember because everything revolves around it — it’s the most expensive, the most time-consuming, and your A&P or IA is the one driving the schedule. But these three avionics and instrument inspections have their own cycles, and they drift independently.

The most common reason these lapse is that owners track them informally — a note in the logbook, a reminder on a phone calendar, a mental note that “the transponder was done at the same time as the pitot-static, so they’re both good until next year.” That works until you change avionics shops, adjust your annual date, or simply forget which month the clock started.

ELT battery: the hidden expiration date

Beyond the 12-month ELT inspection, there’s another date you need to track: the battery replacement date. Under 14 CFR 91.207(c), the ELT battery (or its rechargeable equivalent) must be replaced when 50% of its useful life has expired — which is typically marked on the outside of the transmitter. Most ELT batteries have a useful life of five to six years, depending on the manufacturer.

Additionally, the battery must be replaced after one cumulative hour of use. If your ELT is inadvertently activated (it happens more often than you’d think, usually during maintenance), that activation time counts against the one-hour limit.

Regulatory note: Always verify specific inspection requirements, intervals, and tolerances in the current edition of the applicable FARs and your aircraft’s maintenance manual. Regulations can be amended, and specific aircraft or equipment may have additional requirements via Airworthiness Directives or manufacturer service bulletins. The FAA is the authoritative source for all regulatory information.

Putting it all together: a tracking strategy

The good news is that once you understand these three inspection cycles, tracking them is straightforward. The challenge is maintaining that tracking consistently over years of ownership, across shop visits, annual inspections, and avionics upgrades.

Here’s what effective tracking looks like:

Track each inspection independently with its own due date based on when it was last performed — not based on when your annual falls. If your A&P does the ELT inspection during the annual, record both the annual date and the ELT inspection date separately.

Record who performed the inspection and their certificate or repair station number. For transponder and pitot-static tests, this must be a properly rated repair station — your A&P alone generally cannot sign off these checks unless they also hold the appropriate repair station certificate or rating.

Set reminders with lead time. These inspections require scheduling with an avionics shop, which may have a backlog. A 60-day reminder for the 24-month items and a 30-day reminder for the ELT gives you time to book an appointment without flying past the deadline.

Keep the logbook entries clear. Each inspection should have its own logbook entry with the date performed, the applicable FAR section, the next due date, and the signature of the person or repair station that did the work.

This is exactly the kind of multi-interval, multi-regulation tracking that digital maintenance tools are built for. When you have items on 12-month, 24-month, and calendar-date cycles all running simultaneously, a system that automatically calculates “next due” and sends reminders before they lapse keeps you compliant without the mental overhead.

That’s what we’re building with TachMinder — a single dashboard where every recurring inspection, AD, and maintenance item is tracked by its correct interval, with reminders that fire early enough to act on. No more mental math, no more calendar conflicts, no more discovering at annual that something lapsed three months ago.