Anti-icing/De-icing Flashcards
Ice can cause the following issues:
Reduced performance:
- increased drag
- decreased thrust
Increased stalling speed
- reduced lift
- additional weight
control surface hinges restricted
blocks pitot tubes and static vent giving earenous pressure indications
Ice protection are required in..
- Wing leading edges
- tailplane
- engine and intake inlets
- propellor
- windshield
- static and flight instruments
- sensors and probes
Countering effects of ice
De-icing:
Process of removing accumulated ice in flight or before
Anti-icing
process of preventing ice forming or building up in critical areas of aircraft
BOTH can be done onground using special fluids and hot air
This only lasts a short time..
measures for protection must take place in flight via the aircraft’s own systems
De-icing and anti-icing techniques
HOT BLEED AIR
for wing, fin, tailplane, engine nacelles
HOT ENGINE OIL & AIR
engine nacelles
ELECTRIC HEATED MATS
Propellers and heated edges
PNEUMATICALLY OPERATED INFLATING MATS (de-icing)
leading edge wings, find, tailplane that breaks off accumulations
DE-ICING FLUID
fluid weeping from pores along the leading edge of aerdynamic surfaces.
ICE DETECTION
Vibrating Rod System
ROSEMOUNT
Located on:
Outside of the fuselage
How it works:
** *In normal condition:** Electrically vibrates at 40 Khz
*With ice: the vibration is reduced, signaling ice warning and energises a heater element in the rode
*Returns to normal: Once ice melts, the heater element is switched off and rod vibrates at 40KHz, extinguishing ice detection warning.
ICE DETECTION
Pressure Operated Ice detector
Aneroid capsule connected tube
- protrudes into the airflow
if sensor holes become clogged, pressure in the aneroid drops, triggering ice warning.
Modern systems = electrical sensors
Fluid systems
DE-ICING
Use isopropyl alcohol
Used to de-ice aircraft
Used to de-ice windshield
How it works:
* fluid is pumped from a reservoir along a gallery pipe and into perforated strips on the leading edge
* Fluid flows back over the surfaces to melt the ice
TO KNOW:
1. sequence of deicing is time controlled
- a head compensation valve directs appropriate amounts of fluid to tail and wing
- There are indicators on ice protection panel showin how much fluid remains + warnings
Thermal ice protection
Heat source used to melt ice and prevent it from forming
1. Engine Bleed Air
* most common in jet transport
2. Electric powered matt
* turboprop
Bleed air system
ANTI-ICING/DE-ICING
Bleed air is exteracted from compressor
When de-icing system is on, the de-ice shut off valve opens to allow hot air to flow to perforated tubes (piccolo tube) along the leading edge
mainly sprayed onto inner face of the leading edge or inside the leading slats (inner most slats don’t have this system)
TO KNOW
-Bleed air affects performance - system MUST be OFF during take-off and performance critical phases
- A rise in temperature of air bleed will **warn if there is unacceptable temperature.
**
-Too hot to be used on ground. Only switched on in flight
Jet engine ANTI-ICING
2 Systems:
FOR THE ENGINE
- internal
- can’t be controlled by pilot
- may use either or both hot oil, or hot engine air
- to heats the nose cone and the fan
FOR ENGINE INTAKE
- Uses bleed air passing through ducts inside nacelle
Both reduce thrust and increase of temperature due to hot air entering the enging
Electric powered matt - turboprob
DE-ICING
Use in cases where there isn’t large amount of bleed air
used in leading wing (inner slats usually) and engine intake area
COmposed of:
Resistive metal stripes
how it works:
- switch off and on in sequence (to ease load on generator)
- but some are heated continuously
Intermittently heated areas allow ice to form but they melt again.
Dereflector/Bypass doors Turboprop
Dereflector door and bypass door both drop down to create airflow in the intake and allow ice particles to exit
Electric Protection system
series of electrial matts bonded to the wings leading edge
has **sophisticated control system **
- adjusts the sequence and heat applied to each matt depending on the sensed conditions
Propellors
Need electrical de-icing/anti-ciing system
ice forms near the roots
ice on tips falls off
Electrically heated boots cover 50% of the blade area
Power supplied through** slip rings and brushes**
**Power to heated mats is cycled between inner and outer **
heating sequence is symmetrical across multiple propellors and blades
for odd # of blades, the blades are heated simultaneosly.
Ice protection plate
fitted on fuselage abeam
to protect fuselage from ice flying off the blades
