Use this chapter to distinguish what a control selects from what the aircraft actually does. The current system catalogs list cockpit commands and readings.
Interpret the indication
Distinguish a control input, selected target, switch position, system state and displayed result. They are not interchangeable. Some supplied actions write a different internal binding from the corresponding observation.
N1 and N2 are engine fan and core speeds. A/T means autothrottle; FMA means flight-mode annunciation. APP is the approach-mode button, and LAND ALT is the pressurization landing-altitude target.
Units
Check the current reading catalog and response for the value you are using. APU means auxiliary power unit; EGT means exhaust gas temperature. IRS means inertial reference system.
Use the declared unit and the installed response schema. Pilot airspeed is in knots; altitude and radio altitude in feet; vertical speed in feet/minute; attitude in degrees; heading in magnetic degrees; barometer in inHg. Engine N1/N2 are percentages and engine EGT is in degrees C. Fuel quantity is in kilograms. Hydraulic pressure is in psi and quantity in percent.
Read each control’s declared units before choosing a target. Lever position and actual surface extension are separate observations. Use the radio frequency units returned by the tool rather than applying an extra conversion.
If a required unit or valid observation is unavailable, report the missing information rather than applying a numerical limit with an assumed unit.
Check whether the indication is valid
Use all available power, failure and display-validity information. An unpowered lamp is not a verified extinguished lamp. An unavailable indication is not a numerical zero.
RADIO_ALTITUDE is declared with a display upper bound of 2500 and a display condition matching either IRS mode to 2. Several FMA indications have similar IRS and electrical conditions. These declaration conditions do not supply a general IRS selector decoder.
APU_EGT and the generic TAXI_LIGHT_ON indication are explicitly marked verified=False. A separate taxi-light-brightness position indication is declared. Do not use an unverified binding as the sole completion evidence for a required state.
Engines and APU
Engine 1 corresponds to LEFT engine indications; engine 2 corresponds to RIGHT engine indications. The mapped N2 bindings explicitly identify engines 1 and 2. Use the associated engine throughout each start sequence.
The engine start switches select GRD, OFF, CONT or FLT through named actions. Use the engine controls to select the start levers independently of the thrust levers. Keep these controls separate. During the normal start, fuel admission occurs at 25% N2; at 56% N2 the procedure calls for verification of start-switch OFF, followed by START VALVE OPEN extinguished and a starter-cutout announcement.
Verify engine 2 stable before engine 1 start. A switch return, an extinguished start-valve indication and stable engine operation are separate conditions. Use the assigned stability criteria; the supplied checklist does not provide a numerical stable-idle band or dwell time.
APU selector position, APU availability, APU electrical supply and APU bleed supply are separate states. APU EGT alone does not establish any of these states.
Electrical power, fuel, hydraulics and air
AC/DC meters can be affected by their selected source. Verify source availability and on-bus status for the required power source; an AC voltage alone does not establish that both engine generators are connected.
The fuel system provides six pump-position indications and corresponding toggle actions. Use the selected fuel configuration and actual loading. Where center-pump automatic shutdown is fitted, switch selection and pump operation must be distinguished.
Hydraulic A/B pressure and quantity are separate from the four pump-switch positions. Pressure alone does not establish which pump is selected. The optional hydraulic compensator affects the depressurized flight-control condition.
The air system provides pack, isolation-selector, recirculation-fan and trim-air positions plus cabin conditions. Use the installed detent decoding for OFF, AUTO and OPEN. Cabin differential pressure is not starter duct pressure, and current cabin altitude is not the LAND ALT target.
Autoflight
Read active and armed modes separately using the current autoflight readings. Do not infer a mode from an undecoded number or a selected button light.
Selected airspeed, heading, altitude and vertical speed have separate observations. The current cockpit_mcp_and_autopilot tool also accepts action: "set-altitude" and a value in feet, from 0 to 41,000. Verify the selected target after adjustment using the autoflight readings; selected altitude remains distinct from actual altitude. Do not infer a target from an assumed click count.
VNAV behavior depends on BASIC/COMMON, VNAV ALT installation, intermediate restrictions and whether the MCP target is reset before or after top of descent. Use the actual configuration and observed mode. TO/GA roll behavior and GS-before-LOC capture are also configuration-dependent.
Crew sides, warnings and guards
Use the crew side specified by each procedure. A captain indication is not an independent F/O or standby comparison. Synchronization of settings does not establish independent instrument agreement.
Verify the exact warning, guard or lock named by the checklist. Master caution does not replace a specific annunciator; door closed does not prove door locked; a switch position does not prove its guard closed. Capture warning information before acknowledgement. A warning reset is not correction of the underlying condition. Last modified on October 30, 2026
