Airbus A220 Ice and Rain Protection

The Airbus A220 has wing and engine cowl anti-ice systems with AUTO modes, which can also be operated manually, and it heats its windshields, side windows and air data sensors. Two ice detector systems are installed, and two windshield wiper systems clear rain. Flight in icing conditions is one of the approved operations listed in the EASA type certificate for both models.

The public documents used here, the Transport Canada (TCCA) MMEL and evaluation report, the FAA Flight Standardization Board (FSB) report, the type certificates and the Airbus Aircraft Characteristics, show the controls, components and dispatch rules, but not the AUTO logic or the procedures of the flight crew operating manual. Dispatch conditions quoted are the MMEL's; an operator's MEL may be more restrictive. The principles are in ice protection and ice detection, thermal anti-icing and probe heat, window heat and rain protection. The A320's arrangement is described in A320 bleed air and ice protection, and the Boeing 787, which heats its wing electrically, in Boeing 787 ice and rain protection.

Ice detection

Two ice detector systems (IDS) are installed, and L ICE DET FAIL and R ICE DET FAIL are cautions. The MMEL makes the detectors part of the conditions for flight in icing. With one or both inoperative, the aircraft may be operated in icing conditions only if both the wing and the cowl anti-ice work, alternate procedures are used and the flight stays at or below FL350. Otherwise wing anti-ice is selected OFF and icing conditions are avoided. On the E190-E2 the ice detectors switch the bleed air anti-ice on and off by themselves in AUTO mode; the A220 sources used here do not say what triggers its AUTO modes.

The detectors are checked in other reliefs too: when a wing anti-ice valve is deferred, both ice detection systems are checked before each flight. The general principles of ice detectors, and of what makes a condition an icing condition, are in ice protection and ice detection and airframe icing.

Wing anti-ice

Two wing anti-ice valves (WAIV) are installed, one for each side, and the system has a WING A/ICE AUTO MODE as well as manual operation. The MMEL gives the wing anti-ice zones their own bleed air leak and overheat detection loops, and TCCA's steep approach limitations tie the use of wing anti-ice to the number of bleed sources available. The anti-ice control panel has L COWL, WING and R COWL selectors. On the E190-E2, for comparison, engine bleed air anti-ices the engine cowls and the outboard slats (see E-Jet ice and rain protection).

The MMEL relief for WING A/ICE FAULT concerns the AUTO mode: dispatch is allowed with the wing anti-ice operated manually. A failed valve is more restrictive. With one or both WAIVs secured closed, wing anti-ice is selected OFF and the aircraft is not operated in known or forecast icing conditions; the WAI sensors and both ice detection systems are checked before each flight. A failed detection loop has the same effect: if the leak detection loop of a wing anti-ice zone is inoperative, the WAIV on that side is considered inoperative, and maintenance verifies before each flight that no other loop has faulted.

The FAA FSB differences table from the A220-100 to the A220-300 lists, under limitations, a changed minimum speed with wing anti-ice inoperative above 30,000 ft; the report does not give the values.

Engine cowl anti-ice

Each engine's cowl anti-ice system has two valves, a lower and an upper cowl anti-ice valve (CAIV), and its own AUTO function. The second valve provides redundancy: with one valve secured open, the message COWL A/ICE REDUND LOSS may be displayed for dispatch. If the AUTO function of a cowl system fails, the aircraft may be dispatched with that cowl anti-ice operated manually, as required in flight.

The engine itself has a limit for icing. The PW1500G type certificate sets a minimum N1 of 1,991 rpm, the flight idle value, for flight in icing conditions, and the electronic engine control prevents lower rotor speeds in flight; the ground idle N1 is 1,574 rpm. The engines' own sensors and their heaters are covered in A220 engines.

View full schematic

Probe and sensor heating

The air data sensors are heated, and the MMEL treats their heater failures differently. L AOA VANE HEATER INOP may be displayed for dispatch only if the left angle of attack (AOA) vane itself is considered inoperative. The AOA case heater, air data system (ADS) sense line heater and ADS heater redundancy messages, such as L AOA CASE HEATER INOP, ADS SENSE LINE HEATER 1 INOP and ADS HEATER 2 REDUND LOSS, may simply be displayed.

Probe heating matters on the ground too. The Airbus Aircraft Characteristics warn that, because of probe heating, the OAT and TAT do not read accurately on the ground, so the crew take the temperature for de-icing decisions from the ATIS or other means. The A320, by contrast, heats its TAT probes in flight only, so that its ground reading stays accurate (see probe heat, window heat and rain protection).

Windshield and window heat

Four overhead pushbuttons with OFF lights, L SIDE, L WSHLD, R WSHLD and R SIDE, control the heating of the side windows and the windshields. The MMEL lists the windshield heating as two systems, each with a heat controller. In general, window heat stops ice forming outside the glass, prevents misting inside and keeps the panel at its strongest against a bird strike.

Except for extended operations, one windshield heat system may be inoperative for dispatch if the aircraft stays out of known or forecast icing conditions, the affected heat controller is deactivated and no APPR 2 (CAT II) or autoland operations are flown.

Rain removal

Two windshield wiper systems are installed. Each has an OFF (park) position and three modes: INT (intermittent), SLOW and FAST. The MMEL allows INT to be inoperative if SLOW or FAST works, and SLOW and FAST each back up the other. With one or both wiper systems inoperative, the aircraft may be dispatched if it does not fly in precipitation within five nautical miles of the airport of take-off or intended landing, and no APPR 2 (CAT II) or autoland operations are flown. The sources used here mention no rain repellent.

Operating in icing conditions

On the ground. Before de-icing fluid is applied, the Airbus procedure sets the L COWL, WING and R COWL selectors OFF and the wipers OFF; at least 3 minutes after de-icing, the anti-ice selectors are set as required. The bleed and APU steps of the same procedure are in A220 air conditioning, pressurisation and oxygen, and the fluids themselves in aircraft ground de-icing and anti-icing. Both models may take off at ambient temperatures down to -54 °C. The A220-300 may land down to -54 °C; the A220-100 down to -30 °C, or -54 °C after SB BD500-278001.

In flight. Avionics Build 8.0A2 added a step, "Ice dispersal procedure ... Accomplish, if required", to the procedures for failures that degrade the in-flight anti-icing capability. TCCA's list of such failures includes APU BLEED LEAK, L and R BLEED OVHT and L and R WING A/ICE FAIL, among others.

On a steep approach. For the steep approach option, with a glide path above 3.5° up to 4.1° under AFM Supplement 11, the ice and rain protection limitation reads that approaches are prohibited with a single bleed source unless wing anti-ice is selected OFF.

Dispatch at a glance

The bleed air system, its leak and overheat detection loops and the dispatch rules that come with a bleed failure are covered in A220 air conditioning, pressurisation and oxygen.

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.