Ask a Kenyan student why carburettor icing is not something they worry about and you will hear a version of the same answer. It is a cold-country problem, something for pilots in Minnesota or the English Midlands, not for a country that sits on the equator.
That answer feels reasonable and it is wrong, and the numbers for Nairobi make the point better than any lecture could.
The Short Version
- Carburettor icing is driven by humidity and the cooling effect of fuel vaporisation inside the carburettor, not by how cold the outside air feels.
- The FAA's own carburettor icing probability chart shows icing is possible from about -12°C to 38°C, with serious icing possible up to roughly 32°C when humidity is high enough.
- Nairobi's average relative humidity runs 62 to 78 percent across the year, comfortably inside the icing band on an ordinary Wilson Airport morning.
- Kenya's core training fleet is exactly the aircraft this affects most: older carburetted C152s, C172Ns and Ps, and most PA-28 Warriors and Archers.
- Carburettor icing forms fastest at the low power settings used on descent and approach, the phase of every single training flight nobody skips.
The myth every Kenyan pilot inherits
The misconception is not stupid. It is a reasonable extension of a true fact, structural icing on the airframe, which really does need visible moisture and cold temperatures.
Carburettor icing is a different mechanism entirely, and the FAA's own safety education material addresses the confusion directly. Carburettor ice can form in perfectly clear air with no cloud in sight, because the ice grows inside the engine's induction system rather than on the outside of the aircraft (FAA Safety Briefing, "Breaking the Ice").
AOPA's Air Safety Institute makes the same point about temperature. Carburettor ice can form with the outside air temperature as high as 38°C, provided the relative humidity is around 50 percent or higher (AOPA Air Safety Institute, "Icing in the summer").
Thirty-eight degrees is a warm Nairobi afternoon on the hot end, not a special condition. Kenyan ground school does not need a new fact here, only a correction to where the existing fact applies.
What is actually happening inside the carburettor
The mechanism is straightforward physics, not a mysterious weather event. Air accelerating through the carburettor's venturi drops in pressure, and fuel vaporising into that airstream absorbs heat as it changes from liquid to gas.
That combined effect is why carburettor ice can form even when the outside air itself feels comfortably warm. AOPA's own guidance confirms the practical result: carburettor ice can develop with the outside air temperature as high as 38°C, which only makes sense once you accept that the temperature inside the carburettor throat is running well below whatever the thermometer on the ramp reads (AOPA Air Safety Institute, "Icing in the summer").
A 25°C morning at Wilson can therefore still be cold enough inside the carburettor for ice to build. If there is enough moisture in that air, ice starts forming on the throttle plate and venturi walls, narrowing the airflow the engine depends on.
This is why the FAA's own advisory circular on the subject treats it as an induction system hazard rather than a weather hazard. AC 20-113 recommends that pilots operating where relative humidity is above 50 percent apply carburettor heat briefly before takeoff, during taxi or run-up, specifically to clear any ice that has already started to accumulate on the ground (FAA AC 20-113).
The chart that matters: temperature and humidity, not season
The FAA maintains a published carburettor icing probability chart plotting outside air temperature against relative humidity, and it is worth understanding its shape rather than memorising a single number. Icing is shown as possible across roughly -12°C to 38°C, and serious icing, severe enough to affect the engine at glide power, is shown as possible from around -7°C up to roughly 32°C, depending on humidity (FAA AC 20-113).
The NTSB's own review of the accident record puts a number on how often that chart matters in practice. Carburettor icing was cited as a cause or contributing factor in around 250 accidents investigated between 2000 and 2011, averaging roughly two fatal accidents a year, and the Board found serious carburettor ice possible at temperatures as high as 32°C with relative humidity as low as 35 percent (NTSB Safety Alert SA-029, "Engine Power Loss Due to Carburetor Icing").
Nairobi's climate is the icing sweet spot
This is where the Kenyan context stops being incidental and becomes the entire point. Nairobi's average relative humidity runs from around 62 percent in February, the driest month, up to about 78 percent in May, the most humid (Weather and Climate, Nairobi humidity by month).
Every one of those figures sits above the roughly 35 to 50 percent threshold the FAA and NTSB describe for serious carburettor icing risk. Nairobi's daytime temperatures, averaging around 22°C in the coldest month and 25°C in the warmest, land squarely inside the serious icing band on the chart above (Nairobi climate averages).
Kenya's two rain seasons make the picture worse before they make it better. The long rains run roughly April to June and the short rains October to December, and both periods bring higher humidity on top of an already humid baseline (Tsavo Trust, on Kenya's rain seasons).
Kenya Meteorological Department's own outlook for August 2026, the month this article was written, forecasts occasional cool and cloudy conditions with light rainfall over Nairobi even while much of the country runs dry (Kenya Met, via The Kenya Times). Cool, cloudy, and damp is precisely the combination the icing chart flags, not the exception to it.
Which aircraft in Kenya's training fleet are actually exposed
Not every engine can ice this way, which is a detail worth being precise about instead of treating the whole fleet as equally exposed. Carburettor icing only affects carburetted engines, where fuel mixes with air in a carburettor upstream of the cylinders.
A large share of Kenya's core training fleet is exactly that. The Cessna 172N and 172P, still common in Kenyan schools, run carburetted Lycoming O-320 or O-360 engines, and most PA-28 Warriors and Archers of the same era run carburetted O-320 or O-360 variants as well (Lycoming O-320, Wikipedia; Lycoming O-360, Wikipedia).
Newer Cessna 172R and 172S models switched to the fuel-injected Lycoming IO-360, identifiable by the "I" prefix that marks fuel injection across the Lycoming range, and fuel-injected engines are not exposed to carburettor icing in the same way (Lycoming O-360, Wikipedia). The Piper Archer III was built with both carburetted and fuel-injected variants of the O-360, which means two aircraft that look identical on the ramp can have opposite exposure to this exact hazard.
The wider fleet now flying at Wilson and JKIA sits outside this specific risk. The fuel-injected singles like the C182 and C206, the DA40 and DA42, and the turboprops either inject fuel directly or burn kerosene through a turbine with no carburettor to ice.
That does not make them risk-free on the induction side, only differently exposed, a distinction covered in more depth in the companion piece on negative transfer between aircraft types. A student who trains on a carburetted C172N and later checks out on a fuel-injected 172S needs to know their carburettor heat knob has become decorative, not that the hazard itself has vanished from their flying.
Catching it before it becomes an emergency
Carburettor icing rarely arrives as a dramatic engine failure. It arrives as a slow, easy-to-miss power loss, and knowing the correct symptom for your aircraft is what turns a routine catch into a non-event.
In a fixed-pitch propeller aircraft, which covers virtually every C152, C172 and PA-28 Warrior or Archer flying in Kenya, the first sign of carburettor icing is an unexplained drop in RPM with no throttle movement to explain it. In a constant-speed propeller aircraft it shows up first as a drop in manifold pressure instead, because the propeller governor holds RPM steady while the engine loses power underneath it (FAA, Airplane Flying Handbook, FAA-H-8083-3C).
The correct response either way is full carburettor heat applied immediately and left on, not tapped briefly. Partial heat or an early return to cold can aggravate a partially melted ice buildup rather than clear it, and the engine may run rougher for several seconds as the melted ice passes through before power recovers (FAA, Airplane Flying Handbook, FAA-H-8083-3C).
The riskiest phase of flight is the one every single lesson includes without exception. Reduced power at the venturi increases the cooling effect, which is why the FAA's own chart marks the descent and approach phase, flown at glide power, as the point where serious icing is most likely to build (NTSB SA-029).
A student pulling power abeam the numbers at Wilson on a humid morning is doing exactly the thing the chart is warning about.
The opinion part
Here is the plain version. Kenyan flying schools brief carburettor icing because the syllabus requires it, then quietly file it under "not really our problem" because the country is warm.
That is backwards. Humidity does the damage, not the thermometer, and Nairobi has humidity to spare across almost the entire year while running daytime temperatures that sit inside the FAA's own serious icing band.
A CFI (Certified Flight Instructor) who treats carburettor heat as a fixed-item checklist gesture, applied out of habit rather than because the conditions call for it, is teaching the mechanics of the switch without teaching the judgement behind it.
What to actually do before and during every flight
None of this requires new equipment. Every carburetted C152, C172 and PA-28 in Kenya already has the tool fitted.
- Know whether your aircraft is carburetted or fuel-injected before you fly it, not after an unexplained power loss. The POH will say, and the engine designation will confirm it: an "I" in the Lycoming model number means fuel injection.
- Check temperature and dew point together, not temperature alone. A small gap between the two on a METAR reading means high relative humidity and a live icing risk, regardless of how warm the number itself looks.
- Apply carburettor heat during taxi or run-up on humid mornings, per the FAA's own recommendation, to clear any ice that has already started to form before you ever add power for takeoff.
- Watch RPM (fixed-pitch) or manifold pressure (constant-speed) continuously during descent, the highest-risk phase of every flight, and do not wait for roughness to act.
- Apply full carburettor heat immediately at the first sign, leave it on until you are certain the engine has cleared, and expect a few rough seconds as the melted ice passes through.
- Do not let a warm, sunny day talk you out of the check. The FAA's own data puts serious icing risk as high as 32°C, which is an unremarkable Nairobi afternoon.
Frequently asked questions
Can carburettor icing really happen on a warm, sunny Kenyan day?
Yes. The FAA's own probability chart shows serious carburettor icing risk up to around 32°C when humidity is high enough, and Nairobi's average relative humidity sits well above the threshold most days of the year.
Does every aircraft in a Kenyan flying school's fleet face this risk?
No. Only carburetted engines are exposed. Older C172N/P models and most PA-28 Warriors and Archers run carburetted engines, while newer C172R/S models and most of the wider fleet at Wilson and JKIA use fuel injection or turbine power, which is not exposed to carburettor icing.
What is the first sign of carburettor icing in a C152 or C172?
An unexplained drop in RPM with no corresponding throttle movement, since these are fixed-pitch propeller aircraft. Constant-speed aircraft show a drop in manifold pressure instead, with RPM held steady by the governor.
Why is the descent and approach the highest-risk phase?
Reduced power at the venturi increases the cooling effect that produces ice, which is why the icing chart marks glide power as the condition most likely to produce serious icing, and every training flight includes a descent to land.
Key Takeaways
- Carburettor icing is driven by humidity and the cooling effect inside the carburettor, not by outside temperature alone, and it can form in clear air with no cloud in sight.
- The FAA's carburettor icing probability chart shows serious icing possible up to around 32°C at sufficient humidity, a band that covers an ordinary Nairobi day.
- Nairobi's average relative humidity runs 62 to 78 percent across the year, and both rain seasons push it higher still.
- Older carburetted C152s, C172N/Ps and most PA-28 Warriors and Archers are exposed. Newer fuel-injected 172R/S models and the turboprop and turbine fleet are not, for this specific hazard.
- Watch RPM (fixed-pitch) or manifold pressure (constant-speed) through every descent, apply full carburettor heat at the first sign, and never let a sunny day talk you out of the check.
AngaBrief's Aircraft section of the pre-flight assessment records the aircraft type flown, which is exactly the detail that determines whether this hazard applies at all. It is not a dispatch authority, and the go or no-go decision on any given morning stays with the Pilot in Command and their instructor.