The instrument flight deck check

The check begins outside. On the walk-around, inspect the condition of all antennas, check the pitot tube for obstructions and remove its cover, and check the static ports for dirt and obstructions - including anything on the structure near the ports that would disturb the air flowing over them. A blocked static system is the failure that produces three wrong instruments at once.

Then the paperwork, which is part of the instrument check whether or not it feels like it. Confirm from the aircraft records that the altimeter and static system have been checked and found within approved limits within the past 24 calendar months. Check the ELT battery replacement date in the maintenance record and confirm it falls within its interval.

Then the flight paperwork: the airport directory and all NOTAMs for the condition and frequencies of every navigation aid on the route, and handbooks, en route charts, approach charts, computer and flight log appropriate for the departure, en route, destination and alternate airports.

Finally, in the cockpit: radio equipment switches off, the suction gauge properly marked as applicable, the airspeed indicator reading correctly, the vertical speed indicator reading zero - and if it does not, tap the panel gently. The engine instruments reading properly, the radios checked and set, and the deicing and anti-icing equipment checked for operation. The pitot heater is verified by watching the ammeter when it is switched on, or by the method the POH specifies.

When the master switch goes on, listen to the gyros spin up. Any hesitation or unusual noise should be investigated before flight - a bearing that is failing announces itself here and nowhere else.

Check the source of power for the gyro instruments on the suction gauge or the electrical indicators. The suction developed should be appropriate for the instruments in that particular airplane; where the gyros are electrically driven, check the generators and inverters instead.

Check the magnetic compass card for freedom of movement and confirm the bowl is full of fluid. Determine its accuracy by comparing the indicated heading against a known heading - runway heading - while stopped or taxiing straight, and note the card correction for the takeoff runway. Remote indicating compasses get the same treatment against known headings.

Allow five minutes after engine start for the heading indicator gyro to spin up. Before taxiing, or while taxiing straight, set it to the magnetic compass heading; a slaved gyrocompass is checked for slaving action and compared with the compass.

The handbook links this phase to runway safety directly: ensuring the functionality of the turn coordinator, heading indicator, magnetic compass and attitude indicator before taxiing and takeoff is essential, because knowing the airplane's position relative to the runway and other traffic depends on those instruments being right.

During taxi turns, check the turn coordinator's miniature aircraft for proper turn indications. The ball or slip/skid indicator should move freely and opposite to the direction of the turn, and the turn instrument should indicate the direction of the turn. Taxiing straight, the miniature aircraft should be level.

Before takeoff, recheck the heading indicator: if the magnetic compass and its deviation card are accurate, the heading indicator should show the known taxiway or runway direction when the airplane is aligned with it, within 5 degrees.

And the attitude indicator has a ground test most pilots skip. If the horizon bar fails to remain horizontal during straight taxiing, or tips more than 5 degrees during taxi turns, the instrument is unreliable. Adjust the miniature airplane against the horizon bar for that airplane on the ground - in some tricycle-gear airplanes a slightly nose-low ground attitude gives a level indication at normal cruise.

Finding a defect is only half the task; the other half is knowing what the rules allow. For IFR the equipment floor is 14 CFR 91.205(d), and an item on that list is not deferrable for an IFR flight regardless of how convenient it would be.

For everything else, part 91 offers two acceptable methods of deferring maintenance. The widely used one is the deferral provision of 14 CFR 91.213(d): the pilot determines whether the inoperative equipment is required by the type design, by the regulations, or by an airworthiness directive. If it is not required and the aircraft can be safely operated without it, the item is deactivated or removed and placarded INOPERATIVE. Where deactivation or removal involves maintenance - and removal always does - it must be performed by certificated maintenance personnel and recorded under 14 CFR part 43. The second method is an FAA-approved minimum equipment list, which is a document an operator holds.

One boundary is easy to get wrong and worth stating: maintenance deferrals are not used for in-flight discrepancies. Something that fails in the air is handled by the AFM or POH procedure for that failure, not by placarding it afterwards and continuing.

The instrument pilot's version of the question is sharper than the VFR one. Redundancy is why IFR equipment lists exist, and deferring an item that looked spare on a clear day can leave the airplane with a single path to a critical piece of information.

The check does not end at engine start. The handbook closes the sequence with one line: when shutting down the engine, note any abnormal instrument indications. That is the postflight half of the same job, and it is where the ACS puts documenting in-flight and postflight discrepancies.

A discrepancy noted after an IFR flight is worth more than most because the failures that matter are intermittent. A heading indicator that precessed unusually fast in the third hour, an ammeter that dipped once, a radio that got quiet on one frequency: none of it will reproduce for a mechanic on the ramp, and none of it will exist at all unless the pilot who saw it wrote it down.

What changes for an instrument pilot is what counts as one. An instrument that was merely annoying in VMC is a candidate failure in cloud, and the next pilot to take that airplane into IMC inherits whatever you decided not to mention.

The ACS asks for the procedures, so it is worth walking the whole path rather than stopping at good intentions. Four things happen, and only the first two belong to the pilot.

First, the pilot records it. Squawks or discrepancies are noted and reported to maintenance - written where the operator or the flight school directs, which in practice is a squawk sheet, a discrepancy page in the aircraft binder, or the aircraft log. Write what happened, when in the flight, under what conditions, and what you did about it. An entry reading « HSI acting up » costs a mechanic a day of ground running; « heading indicator precessed about 20 degrees in 15 minutes, twice, both times in the descent, vacuum indicating normal » points at a component.

Second, the pilot decides what it means for the next flight. If the item is inoperative and you intend to fly, that decision runs through 14 CFR 91.213(d) - is the item required by the type design, by the regulations or by an airworthiness directive - and if it may be deferred, it is deactivated or removed and placarded INOPERATIVE. The placard is itself a piece of documentation, and it is the one the next pilot will see first.

Third, maintenance acts. Where deactivation or removal involves maintenance, and removal always does, it must be accomplished by certificated maintenance personnel and recorded in accordance with 14 CFR part 43. A pilot does not make that entry, and a pilot does not return the aircraft to service.

Fourth, the record persists. The corrective action is recorded in the aircraft's maintenance records, which is what makes the next pilot's preflight review possible - the same review that checks that the required maintenance and inspections have been performed, and that any discrepancies have been addressed. Airworthiness directive status and compliance are kept in the same records under 14 CFR 91.417.

The ACS asks for IFR airworthiness as a single knowledge item: the aircraft inspection requirements and the required equipment for IFR flight. The two halves come from different regulations and are checked in different places, which is why they are gathered here. The equipment is 14 CFR 91.205. Paragraph (b) lists what every powered civil aircraft needs for day VFR, paragraph (c) adds the night items, and paragraph (d) adds the IFR items: two-way radio communication and navigation equipment suitable for the route to be flown; a gyroscopic rate-of-turn indicator; a slip-skid indicator; a sensitive altimeter adjustable for barometric pressure; a clock displaying hours, minutes and seconds with a sweep-second pointer or digital presentation; a generator or alternator of adequate capacity; a gyroscopic pitch and bank indicator, the attitude indicator; and a gyroscopic direction indicator, the heading indicator or equivalent. The instrument flight deck check earlier in this lesson is the functional test of that list.

The inspections are the other half, and they are read from the maintenance records rather than the panel. The annual inspection of 91.409 within 12 calendar months, and the 100-hour if the aircraft is used for hire. The altimeter and static system test of 91.411 and the transponder test of 91.413, each within 24 calendar months, both required for IFR. The VOR accuracy check of 91.171 within 30 days if VOR is to be used for IFR navigation, logged with date, place, bearing error and signature. The ELT inspection of 91.207 within 12 calendar months. And airworthiness directive compliance under 91.417, with the method and the next due date recorded. An airplane can pass its instrument flight deck check perfectly and be illegal for IFR because one of those dates has passed.

The ACS lists operating with outdated navigation publications or databases as a risk, and the Pilot's Handbook of Aeronautical Knowledge explains the mechanism in its GPS material: in many receivers an updatable database is used for navigation fixes, airports and instrument procedures, and these databases must be maintained to the current update for IFR operation. The handbook adds the consequence for those who do not: numerous pilots have ventured into airspace they were trying to avoid by using an outdated database, and if there is not a current database in the receiver, the moving map display is to be disregarded when making critical navigation decisions.

The failure mode is quiet. An expired database does not show an error on the approach; it draws a fix where the fix used to be, a minimum altitude that was raised last cycle, or a missed approach procedure that was changed. Paper is no better: an approach chart from an old cycle carries the same wrong number with the same confidence. The Chart Supplement and the NOTAMs are published on a 28-day cycle, and the handbook's planning material puts the check of currency, of charts, of the Chart Supplement, of NOTAMs since its issue, at the start of flight planning rather than at the end.

The use of navigation databases, listed by the ACS as a risk under flight planning, has a second half beyond currency. The database can be current and still be misused: a procedure loaded for the wrong runway, a transition selected that ATC did not clear, a waypoint typed by hand that resembles the one intended. The instrument pilot's defence is to brief the loaded procedure against the chart, fix by fix and altitude by altitude, before the approach; the chart is the authority, and the database is the tool that flies it. Where the two disagree, the chart wins and the disagreement is a discrepancy to be written up.