Instrument cockpit and postflight checks

A check needs an expected result

An instrument flight-deck check asks three questions: what should this item show now, what independent evidence supports it, and what would make this flight unacceptable? A powered screen is not proof that its sensors, backup supply, navigation inputs, or mode selection are ready for IFR.

Use the checklist for the actual aircraft, its installed equipment, and its approved supplements. Work through it with an instructor before using the aircraft in IMC. The sequence below explains the reasoning; it is not a substitute checklist and supplies no invented voltages, vacuum ranges, warm-up times, or battery endurance.

1. ExpectedKnow the normal indication and limitation.
2. ComparedUse an independent reference or approved test.
3. ResolvedInvestigate a discrepancy before departure.

Example: two altitude tapes agree because they share one air data computer. That agreement does not independently validate the pressure source. Compare the appropriate altimeter setting, known elevation, separate standby instrument and system status as the installation permits.

IFH 5-36–5-38: instrument checks · ACS II.C: instrument flight-deck check

Check records as well as switches

For this initial-rating course, consider a typical U.S. small single-engine airplane operated under Part 91. Its inspection program and actual operation determine the requirements. Verify the applicable annual or other authorized inspection, any applicable 100-hour inspection, airworthiness directives and maintenance release. An annual is generally required within the preceding 12 calendar months under 91.409(a), subject to its exceptions. A 100-hour inspection applies to carrying persons for hire and to flight instruction for hire when the person giving instruction provides the aircraft; it is not triggered by every IFR lesson or every rental.

For IFR operation in controlled airspace, 91.411 generally requires the static pressure system, each altimeter and automatic pressure-altitude reporting system to have the specified inspections/tests within the preceding 24 calendar months. Certain maintenance also triggers tests, including opening and closing the static system with the listed exceptions. The installed ATC transponder must meet the applicable 91.413 testing requirements within the preceding 24 calendar months and applicable post-maintenance tests. Verify the records and exceptions rather than treating a cockpit self-test as the required inspection.

If using VOR equipment under IFR, verify the 91.171 operational check within the preceding 30 days and its record, or the regulation's applicable approved-procedure provision. Check the required equipment for this flight under 91.205 and any additional airspace/procedure requirements. The IFR equipment lesson develops the complete inspection and equipment decision.

A maintenance sticker, a recent previous flight, or the absence of a red X does not answer all these questions. Retrieve the actual records and resolve missing or ambiguous evidence.

14 CFR 91.409: annual and applicable 100-hour inspections · 14 CFR 91.411: pressure/altitude system tests · 14 CFR 91.413: transponder tests · 14 CFR 91.171: VOR checks

Inspect the sources and prepare the backups

During exterior inspection, follow the aircraft checklist for pitot/static openings, covers, ice or contamination, antennas and other sensors. Remove required covers; do not probe ports or improvise pressure tests. Check actual fuel, contamination, oil and other aircraft condition items. A clean wing and adequate performance remain necessary even if every instrument is serviceable.

In the flight deck, identify which displays share sensors or electrical buses. Verify standby attitude, heading, pressure and navigation references as fitted, their approved self-tests, and the backup power readiness. Learn the actual switching/reversion procedure and limitations. Do not test a battery by draining it or disconnecting a bus unless the approved procedure calls for that test.

Check usable charts and their effective dates, required navigation database currency, and relevant NOTAM changes for the route, approaches and missed approaches. A moving-map airport symbol is not evidence that its runway or approach is available. Approved navigation status comes from the installation and operating documentation, not from an app's appearance. A tablet backup needs usable downloaded material and power, but does not become an approved IFR navigator.

IFH 5-36–5-38: instrument checks · AIM 1-1-17/1-1-18: GPS and WAAS operation · ACS II.C.R2: outdated publications/databases

Compare indications after power and engine start

Follow the installed equipment's initialization and alignment procedures. Check power-source indications, attitude validity, heading and any alerts. Allow the specified stabilization before judging a gyro or AHRS; do not assume that an old mechanical-gyro warm-up time applies to every electronic installation. A plausible attitude picture with an invalid flag is not usable guidance.

Set the current appropriate altimeter setting and compare with known elevation. The IFH guidance considers an altimeter indication differing by more than 75 feet from field elevation questionable; account for the elevation of the actual check location and refer a discrepancy for evaluation. This is check guidance, not permission to ignore the aircraft's tighter limitations. A conventional VSI should be near its normal ground indication; electronic equipment has its own checks. Compare an anomalous result before adjusting flight controls or dismissing it as lag.

Identify the selected navigation source and confirm tuning, identification, course, display, database and integrity/mode status as applicable. Test communication and navigation using approved methods. Check pitot heat and other ice-protection equipment according to the aircraft procedures; a warm probe can burn, and an ammeter change is not a universal test for every installation. Check engine instruments and the checklist's readiness items.

IFH 5-37: after-engine-start checks

Use taxi motion to check directional instruments

Taxi slowly with attention outside, following the airport diagram, clearances and runway-incursion precautions. During turns, a serviceable turn instrument should indicate the direction of turn, and heading should change consistently with the aircraft's actual motion. The magnetic compass may show its known turning/acceleration errors; compare a steady known heading when appropriate. Check the attitude display according to its installation, rather than applying a mechanical-gyro tolerance to an AHRS.

At the specified run-up point, complete the aircraft's engine, power, navigation and autopilot checks. Know what a failed test looks like and how to disconnect automation. Check the departure clearance against the loaded route, runway and initial altitude. Verify any ODP/SID and its climb requirement against current charts and aircraft performance. A correct flight-plan line does not establish that the autopilot is in the intended mode.

Before takeoff, reconcile heading sources with the actual runway direction and chart. This is another check, not a reason to stare inside while entering or crossing a runway. Pause or ask ATC for time when the setup is not ready.

IFH 5-37–5-38: taxi/takeoff checks · AIM 5-2: departure procedures

A failed check needs an airworthiness decision

Under 91.7, the PIC determines whether the aircraft is in condition for safe flight. A pilot cannot authorize departure with required inoperative equipment simply by promising to avoid using it. An approved MEL and its authorization have their own procedures and limitations. Without an MEL, 91.213(d) applies only to the listed eligible aircraft and requires several determinations; it is not a general permission to cover any failed instrument.

Determine whether the item is required by the relevant certification equipment requirements, equipment list/KOEL for this operation, 91.205 or another rule, or an airworthiness directive. For an eligible item, removal or deactivation, placarding and any required maintenance record must be handled under the applicable rules. An appropriately rated pilot or authorized maintenance person must also determine that the item poses no hazard. A placard alone cannot make a required attitude or navigation instrument optional. Review the complete process in IFR equipment.

Practical example: a standby battery fails its prescribed test before an IMC departure. Stop and identify the installation's required equipment and operating limitations. Do not assume that a normal primary display or an ATC clearance supplies the missing redundancy or legal authorization. Delay, repair or use a different suitable aircraft when the requirements cannot be met.

14 CFR 91.7: PIC airworthiness determination · 14 CFR 91.213: inoperative equipment

Make the next pilot's information specific

After landing and safe shutdown, conduct the aircraft's postflight inspection and servicing checks. Look for leaks, contamination, damage, abnormal wear, remaining fuel and other checklist items. Secure covers and equipment using the correct procedure. Record a discrepancy even when the indication recovered: an intermittent fault can reappear under load or in IMC.

Describe observations rather than inventing a diagnosis. Record when the problem occurred, flight phase, affected indications, alerts, relevant settings, actions taken and the result. For example: “During climb at approximately 5,000 feet, primary attitude showed INVALID for about 20 seconds; standby attitude remained plausible; no bus-switching action taken; message cleared before level-off.” Give the actual aircraft identifier, flight/date and other details required by the operator.

Tell the responsible operator or maintenance contact, using its discrepancy process, and make the aircraft's status clear before someone else dispatches it. A pilot's discrepancy note is not a maintenance approval for return to service. Authorized maintenance personnel make the appropriate maintenance entries and release. Review unresolved items and servicing needs before the next flight.

ACS VIII.A: postflight inspection and discrepancy records · 14 CFR 91.405: maintenance and discrepancies · 14 CFR 91.407: return to service

FLIGHT SCENARIO

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