Oxygen & ice

070 Operational ProceduresChapter 3

Supplemental oxygen — pressurised aircraft

Flight crew

Cabin altitude / duration	Requirement
10,000–13,000 ft (over 30 min)	Oxygen required
13,000 ft+	Entire time above
Certified above 25,000 ft	30 min supply up to 25,000 ft; 2 hours above 25,000 ft
41,000 ft+	At least 1 pilot must wear oxygen

Cabin crew

Cabin altitude / duration	Requirement
10,000–13,000 ft (over 30 min)	Oxygen required
13,000 ft+	Entire time above

Passengers

Cabin altitude / duration	Requirement
10,000–14,000 ft (after first 30 min)	10% of passengers
14,000–15,000 ft	30% of passengers
15,000 ft+	100% of passengers (never less than 10 min)

Key fact

Total dispensing outlets must exceed seating capacity by 10%. Warning system required indicating cabin altitude above 3,000 m (≈ 10,000 ft).

Supplemental oxygen — unpressurised aircraft

Role	Requirement
Flight crew	All time above 10,000 ft
Cabin crew	Over 30 min 10,000–13,000 ft; entire flight above 13,000 ft
Passengers	10% (10,000–13,000 ft, after 30 min); 100% above 13,000 ft

De-ice and anti-ice fluids

Type	Purpose
Type I	De-ice (remove existing ice) — hot fluid
Type II / IV	Anti-ice (preventative) — will wash off by rotation on take-off

Key fact

Holdover time — period fluid remains effective; starts at beginning of last step (anti-ice in 2-step procedure). Affected by temperature, humidity, precipitation, wind, and fluid type. Must repeat if holdover expires. Clean Aircraft Concept — all contamination removed before take-off (fuselage contamination acceptable). Commander ensures critical surfaces free of ice/snow/slush/frost.

Icing conditions

Key fact

Aircraft must be certified for flight into icing. Icing can reduce lift 30% and increase drag 40%. Most likely between 0°C and −10°C; rare below −18°C. Forms on leading edges first. Stable clouds: icing favours 0° to −10°C.

Contamination danger (least to most)

1. Frost
2. Freezing fog
3. Snow
4. Freezing drizzle
5. Freezing rain
6. Rain-soaked cold wing

Runway contamination (EASA)

Condition	Definition
Dry	Neither wet nor contaminated; may include effectively dry sections with moisture
Damp	Surface not dry but moisture does not give shiny appearance
Wet	Reflective but without significant standing water
Contaminated	over 25% of surface covered by over 3 mm water equivalent (slush, loose snow, compacted snow, ice)

Formula — Dynamic hydroplaning speed

Take-off (rotating):  9 × √Pressure (PSI)
Landing (non-rotating): 7.7 × √Pressure (PSI)
Alternative: 34 × √Pressure (bar)

Key fact

Dynamic hydroplaning — no braking action when water deeper than tyre grooves. Viscous hydroplaning — smooth dirty surface, usually at touchdown. Reverted rubber skids — tyre does not rotate; prevented by anti-skid. Wet runway approach: increase approach speed, positive landing, max reverse, brakes immediately. Do not set parking brake on wheel-well fire.

Braking action

Coefficient	Braking action	Code
≥ 0.4	Good	5
0.35–0.30	Medium	3
≤ 0.25	Poor	1
—	Unreliable (slush)	9

Exam trap

Shiny appearance does NOT mean contaminated — wet is reflective without significant standing water. Contaminated requires over 25% coverage AND over 3 mm depth. NADP not used on contaminated runway, ceiling under 500 ft, visibility under 1 NM, crosswind over 15 kts, tailwind over 5 kts, or windshear reported.