Aircraft general

Lights out

The cockpit seats two crew, plus a third occupant and a fourth. The fourth occupant's folding seat is an option, and the FCOM's list of installed equipment records it as fitted on all 49 of this course's airframes. System controls are concentrated on the overhead panel as pushbuttons set into the system synoptic, and wherever possible a pushbutton used for a corrective action carries its own status and failure lights.

Those lights follow the lights-out principle. In a normal configuration the overhead is essentially dark, and the colours mean the same on every system:

• Red - a warning: a failure that needs immediate action.
• Amber - a caution: a failure to be aware of, not needing immediate action.
• Green - normal operation.
• Blue - normal operation of a system used temporarily.
• White - an abnormal pushbutton position, or a test result or maintenance information.

In or out

The pushbutton’s position has a meaning of its own, again the same across systems. Pressed in means ON, AUTO, OVRD or OPEN. Released out means OFF, MAN, ALTN or SHUT. Some pushbuttons do not stay in - those are momentary action.

The picture is AC BUS 1 lost with AC ESS FEED released out to ALTN, from the electrical module. By the colour code, an ALTN legend showing on a pushbutton that is out is white: an abnormal position, selected on purpose.

Red means now

One light in the electrical system shows the principle at work. The emergency generator’s FAULT light comes on red if it is not supplying power when AC BUS 1 and AC BUS 2 are both unpowered.

Red, because in that state the aeroplane is down to its batteries: the essential network is on battery 1 through the static inverter and battery 2 on the DC ESS BUS, and the SHED busses are gone. A failure that needs immediate action is exactly what red is for.

Every opening on the fuselage

The A320’s fuselage has four passenger doors, four emergency exits in the cabin, two cockpit sliding windows that are the flight crew’s emergency exits, three cargo compartment doors and four avionics compartment access doors.

The counts are this aeroplane’s. The FCOM gives the A319 two cabin exits and two cargo doors, and a small batch of A320s in the same fleet has only two cabin exits as well - which is why "the A320 has four overwing exits" needs the word this.

Passenger doors and their slides

The four passenger doors are plug-type doors that open outward and forward - one forward and one aft on each side. Normal operation is manual, with hydraulic damping.

Each has a slide in a container on the inboard lower side, a slide arming lever, and a damper actuator: normally it limits the door’s travel, and in emergency mode it drives the door open. With the lever at ARMED the slide is attached to floor brackets either side of the door, so opening the door inflates and deploys it. If the inflation bottle does not discharge by itself, a crew member can open its valve.

Each door also has a mechanical locking indicator, an ARMED/DISARMED slide light, and a CABIN PRESSURE light that warns of residual pressure in the cabin.

The overwing exits

The four cabin emergency exits are overwing exits, two each side. They open inward, and their slides are always armed - there is no arming lever to forget. Each passenger door has a single-lane or dual-lane slide or slide raft; each emergency exit has a dual-lane slide.

To open one: remove the handle cover, which lights the HANDLE LIGHT and SLIDE ARMED indicator; pull the control handle, and the exit moves inward; lift it out of its frame by the handle recess; throw it out.

The secured cockpit door

A forward-opening hinged door separates the cockpit from the cabin. It is bulletproof, meets the rapid-decompression requirements, and is held by three electric locking strikes that stay locked whenever the door is closed. Where fitted, a deadbolt bolts the door from the cockpit side if more than one strike fails, or the whole locking system does.

The Cockpit Door Locking System’s control unit locks and unlocks the latches on the crew’s command - and unlocks the door by itself on a cockpit decompression, so that differential pressure can swing it open towards the cockpit. If the door jams, an escape panel can be removed from the cockpit side by pulling its quick-release pins and kicking it out.

On the 14 airframes from MSN 06139, the FCOM also describes a Cockpit Door Surveillance System (CDSS). Three video cameras let the crew identify a person before letting them into the cockpit. The camera views appear on the lower ECAM display, and a control panel on the centre pedestal selects them and switches between cameras. The FCOM does not describe a CDSS for the other 35.

NORM, UNLOCK, LOCK

The crew work the door with a toggle switch on the pedestal. UNLOCK, held until the door is fully open. NORM: closed and locked, with emergency access from the cabin possible. LOCK: locked, with emergency access, the buzzer and the keypad inhibited for a preselected 5 to 20 minutes.

From the cabin, a routine request is a code on the keypad and "#"; the cockpit buzzer sounds for 1 to 9 seconds. An emergency request is a separate code, and the buzzer sounds continuously while the OPEN light flashes. If the crew do nothing at all, then after a preselected 15 to 120 seconds the door unlocks by itself for 5 seconds.

And if the door loses electrical power it unlocks - but stays closed.

Three cargo doors, two kinds

The FWD and AFT cargo doors are on the right side, below the cabin floor. They open outward and upward, hydraulically, on the yellow system; their locking - locked open, locked closed - is mechanical, and they open only from outside.

The bulk cargo door is different in every respect: a plug-type door that opens inward and upward, mechanically locked and operated by hand, from outside or from inside.

Opening one on yellow

Release the door handle and pull it up to UNLOCKED. Then, behind the service panel’s access door, hold the selector valve lever at OPEN until the green light comes on - the door is fully open and locked. Holding the lever is what energises the yellow electric pump; releasing it lets the lever return to neutral and shuts the pump down.

While the pump runs for a cargo door, the flight controls and the PTU are inhibited. The only other yellow users still operating are the brakes and the engine 2 thrust reverser. Closing is the reverse, with the lever at CLOSE until the light goes off; on the way, the lever locks at an intermediate position that keeps enough pressure on to stop the door dropping open.

No electrical power

If there is an electrical failure or the yellow electric pump has failed, the cargo doors can still be worked - with the hand pump, reached through the ground service panel. It is a two-person job.

Water in, waste out

Potable water is held in a 200 l tank in front of the wing box, behind the forward cargo compartment, and piped to the galleys and lavatories. Its quantity shows on the Forward Attendant Panel, where the water and waste controls are.

The water is pushed, not pumped. In flight it is pressurised by bleed air; on the ground, by air from the service panel’s pressure port. Waste water from the galleys and basins drains overboard through two heated drain masts, forward and aft. Toilet waste goes to a 170 l waste tank, forced there by differential pressure.

On the ground, and below 16 000 ft

Toilet waste always moves by differential pressure. What changes is where the differential comes from: on the ground, and in flight below 16 000 ft, the vacuum generator makes it.

The drain masts change too - waste water leaves by gravity on the ground, and by differential pressure in flight.