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ATR 42-500 > Ice and Rain Protection > Flashcards

Flashcards in Ice and Rain Protection Deck (17)
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Ice Protection Levels 1,2,3

Level 1s, probes and windows.

Level 2s, anti-ice equipment (props, horns and side windows) and ENG deice.

Level 3s, airframe deice.


Ice Protection System

Aircraft ice protection is provided by a pneumatic and an electrical system adapted for the critical areas. Ice detector monitors ice accretion. It is connected to the CCAS.


Deicing Indicator

Illuminates steady blue when airframe deicing system is on.

Flashes 5 mins after the last ice accretion detection.


Icing AOA pb

The icing AOA pb illuminates green as soon as the either of the horn anti-ice pb is selected on. It indicates that stall warning thresholds have been reduced. It can only be canceled manually be depressing the pb, provided the horns are tuned off.


Ice Detector

Located under the left wing, alerts the crew as soon as ice forms and continues until ice is no longer detected. When 0.5mm of ice accumulates on the the detector, it sends an alert to the crew and begins a 7s heating cycle to shed the ice. If no ice is detected 60s after the detector begins the heating cycle, the alert is canceled.

The ICING light illuminates steady amber when ice is detected and the horns and airframe deice are on. It illuminates flashing amber when ice is detected and either the horns or airframe deice or both are not on, or a fault in the system is detected.


Prop Deice

ACW supplied and inhibited below 63% Np.

Amber FAULT light indicates power loss to at least one blade and sends ANTI-ICING on the CAP.

NORM heats 3 blades per for 10s for 2 cycles then 10s off
HI heats 3 blades per for 20s


Probe Heats

Probes are heated both on the ground and in flight except the TAT probe (inhibited on the ground).


Windshield Heating

Front keeps outside heated to +2*C and inside to +21*C.
Sides keep inside to +21*C.


HORNS anti-icing pbs

2 pbs control the RUD and and L ELEV and the AIL and R ELEV ant-ice heat. A FAULT on these indicates a failure of one of the associated units.

As soon as at least one of the pbs is activated, the stall alert threshold is reduced.


Engine and Wing Protection

Pneumatic boots sequentially inflate to remove ice. Deice valves control the delivery pressure to 20.3psi and 6 distribution valves control air supply to the boots.

Two types of boots are used, chordwise for the leading edges and gas paths and annular for the engine intakes. When deflated, the boots are held to the structure by negative pressure from a venturi supplied with bleed air.



Controls the Deice valves and associated engine distribution valves. Selected ON, the deice valve opens and a signal is sent to the MFC to initiate a cycle.
A FAULT light illuminated indicates a distribution valve disagreement (downstream pressure with valve closed or no downstream pressure with valve open), or AIRFRAME AIRBLEED pb is closed and temperature upstream of the deice valves is >230*C, or the inflation sequencing is incorrect.



Controls the timing cycle of the prop anti-ice when MAN is selected on my the MODE SEL AUTO pb.
Low power is selected when the pb is released, and should be for temperatures between 0*C and -10*C.
High power should be selected for temperatures between -10*C and -30*C.



Controls the selection of timing cycle for MAN operation when selected on the MODE SEL AUTO pb. FAST cycle is 60s (pb released) for ops below -20*C and SLOW cycle is 180s (pb selected) for ops above -20*C.


DEICING OVRD pb (guarded)

Controls the emergency deicing operation which consists of a separate 60s timing cycle and a fault light illuminates when the MFC modules associated to air intake boots control fail resulting in an incorrect inflation sequencing.



With the pb released normal operations are in effect and the DEICING MODE SEL pb is inoperative and the timing cycle selection is controlled by the ADC and the MFC. The Amber FAULT light indicates a an ADC or MFC failure. In the MAN mode (pb engaged) allows the crew to select the appropriate timing cycle depending on the SAT.


Airframe pb

Level 3, controls the distribution valves to the wings and stabilizers. Sends signal to the MFC to initiate the deicing cycle according to the MODE SEL pb.
A FAULT light indicates a disagreement in inflation sequence. Associated distribution valve is open but no downstream pressure is detected or distribution valve is closed and downstream pressure is detected.



Controls both deice and isolation valves.

In the OFF position, both deice and isolation valves are closed. ENG DEICE can still be used.

A FAULT light indicates either, air pressure downstream of the deice valve remains 230*C.