Module 11C.12, 11C.16, 11C.17 — B3 light aeroplanes: ice and rain protection, pneumatic/vacuum, water/waste

B3 levels

Sub-module	B3 level
11.12(a) Ice formation, classification, detection	1
11.12(b) De-icing systems; probe and drain heating	1
11.12(c) Anti-icing; 11.12(e) rain repellent	not required
11.12(d) Wipers	1
11.16 Pneumatic/vacuum systems and pumps	2
11.17 Water/waste systems and corrosion aspects	2

Part 1 — Ice and rain protection (level 1)

Ice formation and classification

• Requires visible moisture and a surface at or below 0 °C.
• Rime ice: small supercooled droplets freezing instantly — white, rough, brittle.
• Clear (glaze) ice: large droplets freezing slowly near 0 °C — transparent, hard, heavy, spreads back; most dangerous.
• Mixed ice and frost (hoar frost on parked aircraft — must be removed before flight; even thin frost on the wing increases stall speed).
• Effects: loss of lift, more drag and weight, lower stalling angle, blocked pitot, jammed controls, propeller vibration; carburettor icing (Module 16) can happen in clear, humid air at temperatures well above freezing.
• Most B3 aeroplanes are not approved for flight into known icing — the AFM limitation must be respected.

Detection

Visual (windscreen edges, wing leading edge, struts, an ice indicator rod), and for night flight on equipped aircraft an ice inspection light.

De-icing and heating systems found on B3 aircraft

System	Notes
Pitot heat	Electrically heated pitot head; check heater current/warmth (hot on the ground — avoid prolonged ground use)
Heated stall-warning vane	On aircraft with known-icing or IFR equipment
Windscreen defrost	Warm air from the cabin heater ducted to the windscreen
Pneumatic boots	Some higher-performance singles — inflated from the dry air pump pressure side, held down by vacuum
Electrical propeller de-ice	Heater boots on blade roots fed via slip rings and brushes (some types)
TKS fluid system	Porous leading-edge panels weeping glycol fluid ("weeping wing"), propeller slinger, windscreen spray — fitted to some modern light aircraft, sometimes as "non-hazard" (not certified for known icing)
Drain heating	Rare on B3 aircraft (no water/waste systems in most)

Wipers

Rare on B3 aircraft; where fitted, never operate on a dry screen (acrylic scratches easily).

Key fact: Most B3 aeroplanes are not certified for flight into known icing; pitot heat and windscreen defrost are the usual ice-protection items. Frost must be removed before take-off.

Part 2 — Pneumatic / vacuum systems (level 2)

Purpose

Supply suction (or pressure) air to drive gyroscopic instruments (attitude and heading indicators) and, on some aircraft, de-icing boots.

Sources

Source	Notes
Dry-vane engine-driven pump	Carbon vanes, self-lubricating; driven through a shear coupling; destroyed by oil/solvent contamination; fails suddenly
Wet-vane pump	Oil-lubricated steel vanes; needs an oil separator to return oil to the engine
Venturi tubes	On the fuselage side in the slipstream/airflow; work only with airflow; affected by ice
Electric standby pump / manifold suction	Backup sources on some installations

Typical vacuum system layout

1. Central air filter — cleans cabin air entering the instruments (replace at intervals; smoking in the cabin clogs filters quickly).
2. Gyro instruments — air jets spin the rotors.
3. Suction relief (regulating) valve with garter filter — limits suction to the set value.
4. Suction gauge — typically 4.5–5.5 inHg at the specified engine rpm; low-vacuum warning light on many aircraft.
5. Pump — exhausts overboard.

Pressure systems use the pump outlet to push air through the gyros instead, with an inline filter and pressure regulator.

Pressure control, indications and faults

Symptom	Likely cause
Low suction reading	Pump wear/failure, leaking lines or fittings, regulator set too low
High suction reading	Clogged central filter (gyros spin slowly although the gauge reads high), clogged regulator garter filter, relief valve stuck closed or mis-adjusted
Gyros slow to erect / tumble	Low suction, dirty instruments, worn bearings
Sudden total loss	Dry pump failure (vane breakage) or drive coupling shear

Note: where the gauge is between the instruments and the pump, a clogged central filter gives a higher-than-normal gauge reading but less air through the gyros.

Pumps — maintenance

• Replace a failed dry pump together with filters; flush/clear lines of carbon debris; never use thread sealant that can enter the pump; correct gasket; no oil contamination.
• Check the drive coupling, mounting and drive rotation; follow the pump manufacturer's service life recommendations.

Key fact: A dry air pump is destroyed by oil or solvent; when a pump fails, replace the filters and clean the lines to remove carbon debris before fitting a new one.