@Peter the piece of the report you translated was that high humidity and near 0°C are propicious to “severe” carb icing.
This was in the analysis section produced by the FFA safety council.
The above is true and gives a link to further reports and safety bulletins based on research into carb icing.
The first 2 sections of the report are descriptions of what actually happened and the pilot’s thinking behind his actions and his decision making.
I don’t see why you think it’s a weird report.
I have never found any practical use for these carb icing diagrams – except to convey the message that carb icing can happen basically anytime. I mean, what does “serious icing” even mean when you essentially never get carb ice even in those conditions?
I have some 800 hours in carburetted aircraft and have encountered (noticeable) carb icing maybe half a dozen times (and I do fly IFR). Only in cruise and in all cases it was quickly fixed by applying carb heat. (But then my SOP is to apply carb heat whenever I fly with reduced power such as on approach – which I guess everyone does?) Of course, it might be different if you fly an aircraft which is unusually susceptible to carb icing.
IIUC severe (not serious) icing is term used in both meteorology and aviation technical circles to describe a) conditions which no aircraft is certified to fly in (anti or deicing conditions will likely be overcome, even airliners)
b) the ice build up in the entry to the carbs might not be overcome by addition of full carb heat. AIUI it is never recommended to use partial carb heat.
The report posted earlier in this thread was of a PA18 pilot who probably made the right decisions (except for commiting an infraction) at the time but found that it was after the intial application of carb heat and the engine parameters returned to normal and just when he thought the problem was over the engine suddenly stopped. It seems that instead of a slow build up of ice the carb entry suddenly became blocked.
Each aircraft is different in its susceptibility to carb icing or indeed any icing as are the conditions one normally flies in.
It is always difficult for a BEA to attribute an accident to carb icing as by the time they get on scene any ice will most probably have melted. So the normal wording in their reports say something along the lines that there is a strong.possibility that carb icing played a part.
gallois wrote:
IUC severe (not serious) icing is term used in both meteorology and aviation technical circles to describe a) conditions which no aircraft is certified to fly in (anti or deicing conditions will likely be overcome, even airliners)
b) the ice build up in the entry to the carbs might not be overcome by addition of full carb heat. AIUI it is never recommended to use partial carb heat.
This applies to airframe icing. There is no such thing as “severe carb icing conditions —> cannot be overcome by carb heat”.
There is no physical reason why such conditions should even exist. The maximum temperature drop in the carburettor is primarily a function of the maximum pressure drop, which happens at idle. As long as the carb heat (which does NOT heat the carburettor, but uses warm air from the engine compartment) raises the temperature of the air by that amount, it is impossible to ice to form, even at zero degrees.
Hence these diagrams are utter BS, and as others have pointed out exaggerate carb icing potential to such a degree to be obviously wrong. If this were true, we would all be using carb heat in the cruise very regularly or fall out of the sky.
The reality is that the propensity for carb ice is highly dependent on the engine type and actual aircraft installation. The only time I could ever get any indication of carb ice on a PA28 is on the ground on a cold wet morning with a cold engine, with RH near the ground almost 100%. Great teaching moment for students to recognise the symptoms and not get concerned when applying carb heat actually makes it worse for a bit before it improves. The reason for that is that in the PA28 installation, the carburetor is bolted to the engine sump, protected from direct air streams and behind the cabin heat exchanger, and that the ducting from the cold air intake via the filter also sits partly behind the cabin heat exchanger. Once the engine and hence carburetor are warm – no ice, at least not within 5 or minutes at or near idle.
On the other hand, Continental powered Cessnas are known to ice up more easily. Way back when I got my licence, I trained on C150 (Continental O-200) and carb ice was more prominent (happened regularly when taxiing on cold wet mornings, SOP was to apply carb heat before line-up to clear any ice). The C152 (Lycoming) was somewhere in between.
Airborne_Again wrote:
I have never found any practical use for these carb icing diagrams – except to convey the message that carb icing can happen basically anytime. I mean, what does “serious icing” even mean when you essentially never get carb ice even in those conditions?
“Serious” vs “moderate” is just a mix of probability, range of throttle settings where it can happen, and speed of icing. I flew a lot in fall / winter mornings with near-fog and I get carb icing pretty much every time at idle, and when the conditions are just right, also in cruise. Knowing these conditions seems quite important to identify the threat (and, for example, do regular checks during cruise, which is not part of your SOP; or just improve your reaction time in order to not get caught by a fully-iced throttle in cruise). At +25/+10, you really don’t need to worry about it. At +6/+5, better know it’s going to happen at some point (meaning all the time) and apply caution and extra checks. That’s what the diagram says, and I don’t see why it’s useless.
I posted.this study in another thread. I can’t seem to cut and paste individual pages so I am posting it again here.
See pages 31 to 34.
Icing_flight_manual_pdf
maxbc wrote:
do regular checks during cruise, which is not part of your SOP
No, that is not part of my SOP, but I always select a specific power setting for cruise and monitor it. If the rpm/MP goes down without any apparent reason, I do apply carb heat to check.
I’ve a few hundred total hours in Pa28, Pa38, and C152 in North Scotland, and don’t remember ever experiencing carb icing.
I’ve 2,000 hours in Jodel DR1050 and Bolkow Junior, both with O200 engines. Engine stoppage due to carb ice is common at start-up and taxi. The Bolkow installation is more susceptible than the Jodel, even though I run it on Avgas. I’ve had carb ice in the cruise frequently lately.
There is a Canadian CAA carb ice diagram with the statement that carb ice is possible at all temperatures using mogas.
Airborne_Again wrote:
No, that is not part of my SOP, but I always select a specific power setting for cruise and monitor it. If the rpm/MP goes down without any apparent reason, I do apply carb heat to check.
That’s sound. But I observed sometimes MP (and RPM) changing on their own when climbing, or if airspeed or OAT varies. I know at least some of these conditions made MP / RPM change slightly and it had nothing to do with carb icing.
maxbc wrote:
I know at least some of these conditions made MP / RPM change slightly and it had nothing to do with carb icing.
Yes. So I apply carb heat and see no improvement so I conclude that it wasn’t carb ice and turn it off again.
