Free safety module 6 of 7Aircraft Systems & Threat Management10 min readLast reviewed: 2026-09-13
Recognise the temperature and humidity conditions where carburettor icing forms even on a warm day, apply carburettor heat correctly, and fly a pre-briefed response to a power loss after take-off.
Scenario
Rough Running on Descent, +19 °C and Humid. Descending into Wollongong (YWOL) on a humid afternoon at +19 °C with the throttle near idle, the engine runs rough and RPM falls by about 150 with no control input. The conditions sit inside the serious-icing band of the CASA carburettor icing probability chart.
Decisions and actions
Apply full carburettor heat early and leave it on. Expect a brief further RPM drop and rougher running as the ice melts, then recovery. Partial heat can make icing worse.
Plan for icing before it appears: select carburettor heat before prolonged descents and extended low-power operation, and check it periodically in cruise when conditions are conducive.
Brief the engine-failure-after-take-off plan before every departure: lower the nose, hold glide speed, and land broadly ahead — no turn back below your pre-briefed height.
For a partial power loss, fly the aircraft first, then run the checks — carburettor heat, fuel selector and quantity, mixture, primer, magnetos, throttle — and commit to a landing area if power does not return.
Safety traps
Believing icing is a cold-weather problem — warm, humid days at low power carry a high risk.
Delaying carburettor heat until the engine is nearly stopped, when little exhaust heat is left to melt the ice.
The impulsive turn back after an engine failure on climb-out, risking a stall and spin.
Startle and fixation stopping the pilot from flying the aircraft while troubleshooting.
Check your understanding
1. On a +18 °C afternoon with high humidity, an aircraft at low power on descent develops an unexplained RPM drop and rough running. What is the most likely cause, and the correct first action?
Detonation — enrich the mixture
Carburettor icing — apply full carburettor heat and expect a brief further RPM drop as the ice clears
Spark plug fouling — increase power and lean aggressively
Fuel contamination — select the other tank
Show answer
B. These conditions are in the serious-icing band. Full carburettor heat sends warm air through the carburettor; rough running as the ice melts is expected, and then the engine recovers.
2. The engine fails shortly after take-off at 400 ft AGL with no runway left ahead. What is the correct immediate action?
Turn back to the departure runway
Lower the nose to hold glide speed and land broadly ahead, within a small angle either side of the nose
Raise the nose to stretch the glide to a better paddock
Complete the restart checklist before establishing the glide
Show answer
B. Below a safe, pre-briefed turn-back height, returning to the runway risks a stall and spin. Fly the aeroplane, hold glide speed and accept a landing ahead.
Educational use only. This module does not replace current legislation, the AIP, ERSA, authorised weather briefings, the aircraft flight manual or instructor guidance. Verify operational information through official sources before flight.
Aero Academic