Propeller Ice Protection
Fluid (slinger-ring) anti-icing and electrical (heater-boot) de-icing, and the anti-ice vs de-ice distinction.
Propeller ice protection, summary notes
- Ice on a propeller is doubly harmful: it disturbs the blade aerofoil (losing thrust) and, because it sheds unevenly, it UNBALANCES the propeller and causes heavy vibration, and shed ice can damage the fuselage.
- FLUID (anti-icing) systems pump a freezing-point-depressant fluid (e.g. isopropyl alcohol or TKS) to a slinger ring on the hub; centrifugal force flings the fluid outward along the blades through feed shoes, preventing ice forming.
- ELECTRICAL (de-icing) systems bond heater elements ('boots') to the blade shank/leading edge; current is fed to the rotating hub through slip rings and brushes and cycled by a timer so ice is loosened and thrown off in turn from each blade.
- ANTI-ICE prevents ice forming; DE-ICE lets a little ice build up and then removes it cyclically, propeller electrical systems are usually cyclic de-icers to limit electrical load.
- Slip rings/brushes and the timer are common maintenance items; boots are checked for security and correct heating, and the system is balanced across the blades.
- ⚠ Exam trap: electrical propeller de-icing feeds current to the rotating hub through SLIP RINGS and brushes and cycles heater boots by a TIMER to shed ice in sequence; fluid systems use a SLINGER RING and centrifugal force to distribute anti-ice fluid.
How is electrical power supplied to heater boots on the moving blades, and why is the heating cycled rather than continuous?
Power passes from the stationary engine to the rotating propeller hub through slip rings and carbon brushes, then out to the boots on each blade. The heating is cycled by a timer, energising one blade (or pair) at a time, so that ice is loosened and centrifugally thrown off in sequence, which keeps the total electrical demand manageable and sheds ice evenly to avoid imbalance.
Ice protection concept map
Propeller Ice Protection
Propeller ice protection quiz
Propeller Ice Protection, quiz
1. Ice on a propeller is especially harmful because it:
Unbalances the prop and causes vibrationImproves thrustCools the engine usefully2. A fluid anti-icing system distributes fluid using a:
Slinger ring and centrifugal forceHeater bootPneumatic pump only3. Electrical propeller de-icing feeds current to the rotating hub via:
Slip rings and brushesA slinger ringThe fuel system4. Electrical de-icing is usually:
Cyclic (timed) to shed ice in sequenceContinuous on all blades at oncePermanently on5. Anti-ice differs from de-ice in that anti-ice:
Prevents ice formingRemoves ice after it formsOnly warns of ice6. A typical propeller anti-ice fluid is:
Isopropyl alcohol / TKSEngine oilHydraulic fluid7. Heater boots for de-icing are bonded to the:
Blade shank/leading edgeSpinner tip onlyTrailing edge8. Cycling the de-ice heating from blade to blade helps:
Shed ice evenly and limit total currentIncrease imbalanceSave fuel