All incidents were carburetted engines, not a single fuel injected.
I understand that. My question was about total number of engines in use i.e. the ratio between carburetted engines and the injected ones. I know carburetted prevail but I don’t know how much.
On FFA REX this week a Savannah had a loss of power and vibrations on take off.
Carb icing was the expected cause.
Many ULMs do not have carb heat due to the position of the carb not needing extra heat.
However, some authorities eg LBA UK insist that a carb heat system is installed even on such aircraft models. There have been reports that this has actually led to carb icing rather than to its avoidance.
I do not know the veracity of such reports but this one certainly suggests there is something going on in which the carb/fuel system is playing a part.
We recently had an engine failure on a Evektor Sportstar RTC with the 912S2 engine. It happened on the runway (fortunately) as the throttle was advanced during touch and go. The engine started again immediately using the starter. The carburettors were disassembled and inspected without anything amiss being found. In the end, the most likely cause was determined to be carb icing, but this is a diagnosis by exclusion so not entirely reassuring. The engine (and aircraft) had about 25 hr TT.
Emir wrote:
I understand that. My question was about total number of engines in use i.e. the ratio between carburetted engines and the injected ones. I know carburetted prevail but I don’t know how much.
Very likely a vast majority is carburetted, for now. Here’s some people guessing, 30 to 1 or even 100 to 1:
https://www.rotax-owner.com/en/912is-technical-questions/8640-number-of-912is-or-ratio-to-uls
Very likely a vast majority is carburetted, for now. Here’s some people guessing, 30 to 1 or even 100 to 1
So based on this ratio and total 22 occurrences, even if the problem existed for both types of engines, it would be reasonable to expect no occurrence on injected engines.
My Rotax 912 80hp installation draws (warm) air from within the engine cowling so susceptibility to carb icing is said to be low. In spite of this I had this electric carb heat system installed. Cheap insurance/peace of mind.
A friendly irish chap sells it via aircraftgraphix at gmail dot com.
Silvaire wrote:
In many places around the world, oxygenated gasoline is mandated by law and the only approved additive is alcohol
Not in Europe. What is mandated is a certain amount of fuel sold must be “carbon neutral”. How this amount is blended into the fuel is up to the resellers. Hence the definition for E10 for instance is up to 10% “carbon neutral” fuel.
aart wrote:
So they suspect vapour lock for the remaining cases
Vapor lock is indeed the only real issue using 98 (ethanol free) for instance. As the text clearly says, this issue is well known and sometimes permanently fixed in the non certified world, but not so much for certified aircraft. Clearly the aircraft manufacturers haven’t done a good enough job. Also, certification is a lot of paper and little engineering or testing. This is rather mind blowing actually. If they have tested the aircraft just one single time with winter blend mogas on a warm summer day, this issue would for sure rise it’s head. Clearly this has not been done, but the manufacturer still approves mogas for their aircraft, with no strings attached.
In the UK there’s a restriction of max 6000 feet with mogas, regardless of aircraft (or something like that, don’t remember exactly).
What seems to have been going on IMO, is this: For UL’s this issue (vapor lock) with mogas is well known, and has been so for decades. But, UL owners are more doers rather than talkers, so the issue is handled like any other “issue” like for instance low tire pressure (you simply fill more air in that thing). This could be anything from more cooling of the fuel system, being sure to use correct fuel for the season and preventive operative measures, to full re-design of the fuel system. Even installing highly modified engine with FI, Edgeperformance, that fixes this and a whole bunch of other nonsense issues. The aircraft manufacturer, as well as Rotax in many cases, being oblivious to this.
The aircraft manufacturers think there have been no issues with the UL fleet. There have been some rumors from time to time, but a “serious” business don’t take rumors into account. Rotax themselves are more concerned with people doing modifications on their products for “legal reasons” than recognizing than the main reason for these modifications are indeed suboptimal solutions.
What the manufacturers have done is to use the UL fleet as experience for their certified fleet. This has been done without assuring that they get correct feedback. No feedback usually means everything is OK. In this case however, no feedback does not mean a damned thing, but rumors do. It’s the same with UL91 and it’s actual octane level “on the street”. Rumors!! 
Yes, they are rumors, and they will remain rumors for all eternity. People will adapt nonetheless. People will only use UL91 when absolutely needed, and precautionary measures will be taken (throttle back immediately after take off, climb with a higher speed than usual for better cooling, stress the engine a little less than usual). The problem will pop up from time to time nonetheless and the effect will be:
1. Maintain the believe that UL91 is not what it seems. The rumors will not go away.
2. Maintain the believe that this is only rumors. It happens so seldom and the real snag could be a number of other things.
gallois wrote:
However, some authorities eg LBA UK insist that a carb heat system is installed even on such aircraft models. There have been reports that this has actually led to carb icing rather than to its avoidance.
How can adding carb heat lead to carb icing? Unless that means that unheated air will be used where normally preheated air from the engine compartment would have been used.
