A320 Normal Procedures: Cockpit Preparation to Engine Start

The A320's cockpit preparation and engine start procedures are the part of the Airbus standard operating procedures (SOPs) that turns a parked, often unpowered aircraft into one with both engines running and ready to taxi. They establish that the aircraft is fit to fly, align the inertial reference system, load the flight management and guidance system (FMGS) and start the engines, normally automatically under FADEC control.

The Airbus flight crew operating manual (FCOM) and flight crew training manual (FCTM) set the order: safety exterior inspection, power-up and preliminary cockpit preparation, exterior walkaround, cockpit preparation, before pushback or start, and engine start. Engine figures are those of the CFM56-5B unless another engine is named, and the aircraft's own FCOM governs. Taxi and takeoff follow in A320 normal procedures: taxi, takeoff and climb.

SOP philosophy and task sharing

Airbus SOPs consist of inspections, preparations and normal procedures. The items of each procedure follow a standardized scan of the cockpit panels, unless that order would conflict with the priority of the actions, so that the work is efficient and nothing is skipped. The SOPs assume that all systems operate normally, that the automatic functions are used normally and that both pilots use an electronic flight bag; Airbus recommends two, to reduce the risk of erroneous inputs.

Preparation actions are allocated by seat, to CM1 in the left seat or CM2 in the right. Phase-of-flight duties are allocated by role: the pilot flying (PF) flies and navigates, and the pilot monitoring (PM) monitors the flight path, the navigation and the systems, and communicates (see pilot flying and pilot monitoring). On the ground the PF prepares the FMGS and the PM checks it.

The cockpit follows the dark cockpit philosophy: when every system is ready and fit to fly, the overhead pushbuttons are unlit, so any light during the panel scan means something.

Safety exterior inspection and power-up

The safety exterior inspection comes first, before the hydraulic systems are pressurized. CM2 checks the wheel chocks; if they are not in place, the parking brake must be set with sufficient accumulator pressure. CM2 also checks the landing gear doors: if any is open, the hydraulic systems are not pressurized until the ground staff give clearance. Items marked with an asterisk are the only ones repeated after a transit stop without a crew change; a new crew does them all.

At power-up CM2 confirms both ENG MASTER switches OFF and the ENG MODE selector at NORM. If the aircraft has not been electrically supplied for 6 hours or more, CM2 checks, with the BAT pushbuttons OFF, that each battery reads above 25.5 V, which ensures a charge above 50 %. At or below that value a charging cycle of about 20 minutes follows: batteries at AUTO, external power ON, and the ELEC page showing the battery contactors closed and the batteries charging, before a second check.

The APU is then started (see A320 APU). On the batteries alone it should be started within 30 minutes of selecting them to AUTO, because after 35 minutes their charge is below 25 % of capacity. The APU FIRE test pushbutton must not be held for more than 3 seconds, or the APU may shut down and its extinguisher discharge. After MASTER SW ON the crew wait at least 3 seconds before pressing START. The SOP sets APU BLEED ON once the APU is available; selecting it 3 minutes after the APU start further reduces cabin odors, since the warm-up lets the seals reach their best performance and clears oil traces from the duct.

Preliminary cockpit preparation

The preliminary cockpit preparation checks the aircraft's condition before the walkaround, starting with aircraft acceptance. CM1 presses the RCL pushbutton on the ECAM control panel for 3 seconds, which recalls every warning and caution the crew cleared or canceled during the last flight. The crew also review the operations engineering bulletins (OEBs) applicable to the aircraft, with particular attention to red OEBs and above all those that must be applied before the ECAM procedure (see A320 ECAM and warning system).

The crew check the fluid levels on the system display: the HYD page for hydraulic quantity, the ENG page for engine oil and the DOOR page for crew oxygen, where on the ground an amber half frame around a pressure below 1,500 psi calls for a check against the minimum. VHF 1 is kept for ATC, being the only VHF available in the emergency electrical configuration.

A preliminary takeoff performance computation gives both pilots a common plan and the same assumptions. A crosscheck of performance data covers the runway, the takeoff shift, V1, VR and V2, green dot, the takeoff thrust (TOGA, FLEX or derated), flaps, THS, packs, anti-ice and the engine-out acceleration altitude. Agreement on green dot indirectly confirms that consistent gross weights were used.

Exterior walkaround

The exterior walkaround gives a global assessment of the aircraft; missing parts or panels are checked against the configuration deviation list (CDL) for dispatch. At the landing gear the crew check the wheels and tires for cuts, wear and cracks, the removal of the safety pins, the brake wear pin length with the parking brake ON and the oleo extension; any difference between the two main gears is reported.

IRS alignment: complete and fast

An IRS is aligned only with the aircraft stopped on the ground, never during engine start or with the engines running; if the aircraft moves during the alignment, a new full alignment is needed. Ground alignment is possible between 82° N and 82° S (see A320 ADIRS and standby instruments).

A complete IRS alignment is required:

• before the first flight of the day;
• at a crew change;
• when the departure airport lies between 2° N and 2° S;
• with GPS unavailable, if navaid coverage on the route is poor or the flight will last more than 3 hours.

When none of these applies, a fast IRS alignment is done if the IRS and FMGC positions differ by 5 NM or more on the MCDU POSITION MONITOR page.

The crew initialize the position on the MCDU, gate coordinates being the most appropriate. Entering or changing the origin or the company route resets the INIT coordinates to the airport reference point, so they are checked again. During the alignment the E/WD memo IRS IN ALIGN counts down the minutes to NAV, from at most 10. It is green, and pulses if one IRS's alignment is faulty; once an engine has started it turns amber, and a faulty alignment then becomes the IR NOT ALIGNED caution. The principles are in inertial reference system alignment and modes.

Cockpit preparation and FMGS initialization

The cockpit preparation completes the panel scan and the setup for the flight. Pressing the recorder GND CTL pushbutton starts the cockpit voice and flight data recorders on the ground; after engine start its ON light goes out and the recorders run automatically. The flight number, which ADS-B transmits, is entered in the FMS during the cockpit preparation.

The PF then prepares the FMGS (see A320 FMGS and MCDU), filling every boxed field; blue fields accept an entry, while green data is computed and cannot be changed.

View full schematic

INIT A takes the city pair or company route, the cost index and the cruise level. INIT B takes the expected zero fuel weight and its center of gravity (ZFW, ZFWCG) and the block fuel, checked against the flight preparation; it is not filled straight after INIT A, because the FMGS would start computing predictions and slow the remaining entries. After engine start INIT B is no longer available, and weight or fuel changes go on the FUEL PRED page. The PERF TAKE OFF page takes V1, VR, V2, the FLEX temperature, the flap and THS setting and the thrust reduction and acceleration altitudes, which default to 1,500 ft or a value set by airline policy. The engine-out acceleration altitude must be at least 400 ft above the airport, keep the net flight path 35 ft above obstacles and respect the maximum time for takeoff thrust.

When the PF has finished, the PM checks the entries by going through the FMGS pages in the same order, so that both pilots share the same picture of the departure, the trajectory and the constraints, and asks if anything is unclear.

Before start and pushback

Each pilot adjusts the seat until the eyes are in line with the red ball and the white light; from there the cut-off angle and the view of the ground ahead are those the taxi technique assumes. As in airline procedures generally, the beacon goes on before pushback or engine start, telling the ground crew that engines are about to run (see aircraft exterior lighting). The thrust levers must be at IDLE, because the engines start whatever their position: a lever left forward would bring a rapid and hazardous thrust increase.

For pushback the ground staff disconnect the nose wheel steering with the towing lever on the nose gear, and the NW STRG DISC memo appears, in a color that depends on whether an engine is running. Towbarless pushback with an accepted tug is approved up to a steering angle of ±85° (see ground handling, pushback and engine start). The Before Start checklist then confirms the critical items after the flows, as every normal checklist does (see standard operating procedures and checklists).

Start air comes preferably from the APU bleed, with the APU at 100 %, then from an HP ground cart, never used together with APU bleed, and last from a running engine by crossbleed, with X BLEED OPEN and that engine's thrust increased once the area behind is clear.

Automatic engine start sequence and idle parameters

Engine 2 is usually started first: it powers the yellow hydraulic system, which pressurizes the parking brake. In the automatic engine start the FADEC controls the start valve, the ignition and the fuel (see A320 engines and FADEC):

If no ENG MASTER is set ON within 30 seconds of selecting IGN/START, the pack valves reopen. The power transfer unit is inhibited during the first engine start and tested automatically during the second, so a brief HYD PTU memo then is normal.

At ISA sea level a CFM56-5B stabilizes at idle, shown by AVAIL, at about 19.5 % N1, 58.5 % N2, 390 °C EGT and a fuel flow of 275 kg/h (600 lb/h). With both engines running the ENG MODE selector returns to NORM, and the ENG page clears 10 seconds after the end of the start sequence. The after start procedure then sets APU BLEED OFF, and each engine runs at or near idle for at least 2 minutes before high thrust.

Start faults and crew actions

On the ground the FADEC aborts an automatic start by itself for a hot start, an overtemperature, a stalled start or no light-off. It closes the HP fuel valve and the start valve, cuts the ignition, dry cranks the engine to clear fuel vapor and manages any further attempt. The amber FAULT light on the ENG MASTER panel and an ECAM caution alert the crew. The dry crank continues only while the ENG MASTER stays ON: setting it OFF stops it.

The ENG START FAULT alert covers, among other causes, no light-up, a stall or an overtemperature above 725 °C, an exceeded starter time and low start air pressure. The start EGT limit is 725 °C on the CFM56-5B and 635 °C on the V2500-A5.

The starter limits are:

• an automatic start, with up to three attempts, counts as one cycle;
• successive ground start cycles need a 20-second pause;
• after four failed cycles, the starter needs 15 minutes of cooling;
• the starter must not run with N2 above 20 %.

If the electrical supply is interrupted during the start, shown by the loss of the ECAM display units, the FCOM has the crew set the ENG 2 MASTER OFF and perform a 30-second dry crank. If the ground crew report fuel leaking from the engine drain mast, the engine runs at idle for 5 minutes; a leak still present then means shutdown and a maintenance investigation.

In a manual start, MAN START opens the start valve and the ENG MASTER goes ON at maximum cranking, at least 20 % N2; the FADEC then aborts only for a start EGT exceedance before 50 % N2 on the ground. In flight no start is aborted automatically (see gas turbine engine starting).

Library articles are written for study and exam preparation. They do not replace your aircraft's approved documentation, your operator's procedures or the regulations themselves.