Systems: Ice and Rain Protection Flashcards
How can the pneumatic anti-icing system be enabled?
The pneumatic anti-ice system is fully automatic. Under icing conditions in flight, the entire system protection is activated. On the ground, there is a system protection built in which inhibits the wing and stabilizer anti-ice valves from opening whenever wheel speed is below 25 knots. This inhibition can only be overridden when performing a test of the pneumatic anti-ice system. If the system fails to automatically engage in icing conditions, per the QRH, the ice detection override knob may be set to ALL to engage the system.
What surfaces does the thermal (pneumatic) anti-icing system cover?
Engine nacelle (lips)
Wing leading edges
Horizontal stabilizer leading edges
What are the electrically heated areas?
Windshields
Pilot tubes, pitot-static tube, AOA sensors, TAT probes and pressurization static ports
Lav water drain and water service nipples
When do the electrically heated areas receive heat?
Anytime an engine is running, all the electrically heated elements receive heat, with the exception of the TAT probes, which only receive heat when the engine lips are receiving pneumatic heat.
How does the system automatically detect icing conditions? How will the crew know if the system is functioning properly?
There are 2 ice detectors installed at the left and right nose section of the aircraft. They are designed to pick up ice quickly, and once ice is being detected, a signal is transmitted to activate the pneumatic anti-ice system. During icing encounters, the icing signal remains valid for 60 seconds, and an advisory (ICE CONDITION) is displayed on the EICAS. Simultaneously, an internal ice detector is heated to de-ice the unit and probe. When the probe is de-iced, it’s natural frequency is recovered and heating of the probe ceases. With the natural frequency of the probe restored, the probe is cool enough to once more monitor ice build up. This sucked then repeats itself until icing conditions no longer exist.
Can thermal anti-icing be provided by the APU?
No.
The APU only has one stage of compression and cannot provide air that is dense/hot enough.
Where does anti-ice bleed air for the horizontal stabilizer come from?
Normally, engine bleed #1. However, limited anti-ice capacity can be provided by a single engine bleed up to 15,000 feet.
Refer to overhead panel.
Definition of icing in the air? On the ground?
In flight: TAT less than 10 degrees C and visible moisture is present in any form
On the ground: ATIS temp of less than 10 degrees C and visible moisture is present in any form.
Visible moisture: clouds, fog with visibility of one mile or less, rain, snow, sleet and ice crystals.
How is engine lip anti-icing provided? Can it be manually selected?
The engine anti-ice valves open automatically as a function of system logic. They will receive an electrical input to open when the ice detection override knob is set to AUTO and any ice detector is activated. The valves can be manually commanded to open by placing the ice detection override knob to ALL or ENG, or by testing the ice protection system per the AOM.
When are the horizontal stabilizer and wing anti-icing systems inhibited?
On the ground, with a wheel speed of less than 25 knots. This is to prevent structural damage caused by surface heating.
How is a minimum compressor speed (N2) maintained during los thrust settings in icing conditions?
The FADEC for each engine provides an automatic logic to ensure a minimum available thrust during icing conditions, even during low thrust settings to compensate for increased bleed air consumption. This is done automatically with no pilot intervention, anytime the aircraft is in flight and icing conditions are detected.
The logic is automatically inhibited when the landing gear is extended in order to improve the aircraft’s rate of descent and glide slope path adjusting capability.
What is the desired holding configuration of the aircraft when holding in icing conditions?
Gear up, flaps up, min airspeed 200 KIAS
