IFR equipment and required inspections

Start with the aircraft and the intended operation

IFR dispatch is an aircraft-specific decision. Check the airworthiness certification, approved flight manual, markings and placards, installed equipment and supplements, and the intended route, altitude and procedures. An airplane can be airworthy for a restricted operation yet unsuitable for a proposed IFR flight. A rental description saying “IFR equipped” is not the approval or maintenance evidence.

Under §91.7, the PIC determines whether the aircraft is in condition for safe flight and discontinues flight when unairworthy mechanical, electrical or structural conditions occur. Section 91.9 requires compliance with approved operating limitations. The annual inspection establishes a dated maintenance result; it does not promise that the aircraft remains serviceable after a later failure.

Read the kinds of operations equipment list (KOEL), required-equipment provisions and applicable approved supplements. These can require an item that is absent from a familiar mnemonic. Trace shared power and sensor dependencies when assessing redundancy. A tablet, portable receiver or attractive backup display is not automatically approved to replace a required instrument or navigator.

§91.7: airworthiness and PIC safe-flight determination · §91.9: approved operating limitations · §91.205(a): instruments/equipment or approved equivalents

Build the legal equipment list in layers

For the powered civil aircraft with standard U.S. airworthiness certificates covered by §91.205, IFR adds to the applicable day-VFR equipment and, at night, the night-VFR equipment. Section 91.205(d) requires two-way radio communications and navigation equipment suitable for the route; a gyroscopic rate-of-turn indicator subject to the rule's specific third-attitude-system exception; a slip-skid indicator; a sensitive altimeter adjustable for barometric pressure; a clock showing hours, minutes and seconds with a sweep-second pointer or digital display; an adequate generator or alternator; gyroscopic pitch/bank and direction indications, or approved equivalents.

The day-VFR baseline includes such items as airspeed, altitude and magnetic direction information, engine/fuel indications and the applicable safety equipment. Review the actual text for the aircraft and operation rather than relying on a shortened list. A VSI is not listed in §91.205(d), but the aircraft's approval, KOEL or procedure may still require it. Similarly, IFR does not universally require GPS or VOR equipment: the navigation equipment must suit the route and procedures being flown.

Add requirements imposed elsewhere: applicable ELT provisions, transponder/altitude-reporting rules, ADS-B Out airspace rules, required lighting, and aircraft-specific approvals for the chosen navigation operations. Whether a transponder or ADS-B exception/deviation applies is a separate legal determination. Carrying portable ADS-B In does not meet an ADS-B Out requirement.

Cockpit example: if an approved installed navigator supports the cleared RNAV route but its required navigation source is inoperative, a working communication radio and paper chart do not restore that capability. Repair, change the lawful mission or obtain a clearance the surviving approved equipment can support.

§91.205(b), (c), (d): applicable VFR and IFR equipment · §91.207: ELT requirements and exceptions · §91.215: transponder/altitude-reporting equipment · §91.225: ADS-B Out equipment/airspace requirements

Read the record, interval and applicability

For a typical small standard-category piston airplane under the ordinary inspection path, an annual inspection and approval for return to service must be within the preceding 12 calendar months. A 100-hour inspection is additionally required when carrying a person other than a crewmember for hire, or giving flight instruction for hire in an aircraft the instructor provides. “Used for training” alone is not the rule's entire test. Progressive and other approved programs, and the exceptions in §91.409(c), must be checked when applicable.

An annual can meet the 100-hour requirement, but an ordinary 100-hour inspection is not an annual unless an authorized annual inspector performs and records it as such. The 100-hour limit may be exceeded by no more than 10 hours while traveling to the place of inspection; those excess hours count toward the next interval. This is not a general allowance for continued lessons or rental flights.

Check the aircraft, engine and propeller records for completed inspections, applicable airworthiness directives (including recurring due dates), life/airworthiness limits and required return-to-service entries. Maintenance that has opened or altered an IFR system may trigger a test before its normal periodic due date. Match the aircraft and installed equipment serial/identification data to the record.

ELT inspections are required within 12 calendar months after the last inspection when §91.207 applies. Its battery replacement/recharge conditions are separate: more than one cumulative hour of use or 50 percent of the manufacturer-established useful life/charge life, with the specified exceptions. A current annual does not automatically prove every separately applicable inspection or battery condition was addressed.

§91.409(a)–(d): annual, 100-hour, exceptions and progressive inspection · §91.403: maintenance responsibility and mandatory limitations · §91.417: maintenance and inspection records · §91.207(c)–(d): ELT batteries and inspections

Separate the IFR tests from the annual

Calendar months and days are different. A system test completed in October 2024 ordinarily remains within the 24-calendar-month interval through October 2026, provided no earlier retest trigger applies. A VOR check is a 30-day interval; it does not last to the end of the thirtieth calendar month or automatically through a month end.

Section 91.411 requires retesting after opening and closing the static-pressure system, except use of system drains or alternate-static valves, and addresses maintenance that can introduce altitude-reporting data errors. It also prohibits using an altimeter for the covered IFR operation above its highest tested altitude. The pilot's normal ground check is useful but does not replace the authorized maintenance test.

The transponder test is distinct from the altimeter/static test even when a shop performs them together. Read what was actually tested, by whom, to what altitude and on what date. A transponder responding to ATC today does not establish that the prescribed test is current.

§91.411(a)–(d): altimeter/static/reporting tests, maintenance triggers and tested-altitude limit · §91.413: transponder tests and data-correspondence triggers · §91.171: VOR applicability and 30-day check

Use a permitted VOR method and record the result

When using VOR equipment for IFR, §91.171 permits the approved maintenance procedure or a qualifying operational check within the preceding 30 days. The authorized ground test signal or designated ground checkpoint tolerance is ±4°; an authorized airborne checkpoint tolerance is ±6°. When the rule permits the alternate airborne check method, use its specified location/procedure and ±6° tolerance rather than an arbitrary point over the countryside.

Two independent VOR systems, independent except for the antenna, can be checked against each other while tuned to the same VOR; the maximum difference is 4°. Agreement proves only the allowed comparison, not that both identify every possible fault. Two displays repeating one receiver do not create two independent systems for this method.

Record the date, place, bearing error and signature in the aircraft log or another record. The permitted tolerances are check limits, not desired tracking accuracy in flight. Learn the installed receiver's setup, test-signal identification and published checkpoint information before attempting a check. A navigator's GPS position does not casually replace the prescribed VOR check.

§91.171(b)–(d): authorized check methods, tolerances and record · AIM 1-1-4: VOR receiver check and VOT procedure

A placard is one part of an inoperative-equipment decision

First determine whether the aircraft operates with an approved minimum equipment list (MEL) and the required FAA authorization. An MEL applies to the particular aircraft and its stated conditions, procedures, records and limitations. A master MEL, another airplane's list or a maintenance shop's general suggestion is not an approved dispatch authorization for this airplane.

For an eligible aircraft without an MEL, §91.213(d) offers a specific path. A typical small non-turbine-powered airplane may qualify, but verify the aircraft is within the rule. The item must not be required by the VFR-day type-certification requirements, the aircraft equipment list/KOEL for the intended kind of operation, §91.205 or another applicable Part 91 rule, or an airworthiness directive requiring it to be operational.

If the item passes those checks, it must be removed with the cockpit control placarded and the specified maintenance record, or deactivated and placarded inoperative. If deactivation involves maintenance, it must be done and recorded under Part 43. An appropriately rated/certificated pilot or maintenance person must determine that the inoperative item creates no hazard. A pilot cannot use the placard to authorize unqualified maintenance.

Risk example: a cabin light may be legally deferrable for daytime operation, but a night IFR mission can make its loss a checklist or panel-reading hazard. Even a lawful deferral can undermine workload management or redundancy. Assess interactions, remaining power/sensors and the actual conditions. Required equipment cannot be made optional by writing “inoperative” beside it.

§91.213(a), (d): approved MEL and eligible non-MEL paths · §91.205: operationally required equipment · ACS II.C.K3/R1: inoperative procedures, documentation, limitations and risk

Make a defensible dispatch decision

Build a one-page dispatch record for a fictional airplane: approved operating limitations, applicable required-equipment list, inspection/test dates, VOR-use plan, discrepancies and the lawful resolution. Explain each item's applicability rather than merely listing mnemonic letters.

If the static system was repaired yesterday, check the maintenance-triggered test rather than trusting last year's sticker. If a required gyro-equivalent indication fails today, a current annual does not cure it. If an item is apparently optional, complete the full §91.213 path and hazard assessment. Obtain the maintenance expertise needed before departure; an IFR clearance is not an airworthiness approval.

§91.7: PIC condition-for-safe-flight determination · §91.213: inoperative-equipment paths · §91.411: tests after static-system maintenance

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