17.5–17.7 Propeller ice protection, maintenance, storage and preservation

Scope

• 17.5 Ice protection — A level 1, B1 level 2: fluid and electrical de-icing equipment.
• 17.6 Maintenance — A level 1, B1 level 3: static and dynamic balancing; blade tracking; assessment of blade damage, erosion, corrosion, impact damage, delamination; treatment/repair schemes; propeller engine running.
• 17.7 Storage and preservation — preservation and depreservation.

Why propeller ice protection?

Ice on blades destroys the aerofoil shape (thrust falls, power required rises) and sheds asymmetrically, causing severe vibration and damage to the fuselage from flying ice. Ice collects mainly on the inner (root) area of the blades and the spinner, where centrifugal force is lowest.

Fluid (anti-icing) systems

• A tank of isopropyl alcohol (or a glycol-based fluid) and an electric pump (rate controlled by a rheostat) deliver fluid to a slinger ring — a U-section channel at the rear of the hub/spinner.
• Centrifugal force throws fluid from the slinger ring along feed shoes (grooved rubber strips bonded to the blade leading edges), spreading it over the blades.
• It is mainly an anti-icing (preventive) system; finite fluid supply limits endurance; alcohol is flammable.