My grateful thanks to all who contributed on this subject.
It is reassuring to know that I am not alone in experiencing the symptoms of
carb.
air ice on start up in cold, damp conditions.
The general consensus of opinion from those who replied appears to be that it is
in fact carb. air ice, which disappears as soon as there is sufficient radiant
heat from the engine to warm the carburettors and inlet manifolds. Hence no
problem in flight when the engine is thoroughly warm.
Some members suggest fitting the Nigel Beale mod. to heat the carburettors,
which
uses coolant from the cylinder heads.However, it occurs to me that although
this will probably deal with the ice when the coolant has gained sufficient heat
---From the cylinder heads, the mod. then becomes redundant, as it appears that
radiation from the engine is sufficient to melt any ice as soon as it has warmed
up. The period throughout which the mod. may be effective is debatable.
Another point which came to light, which I had overlooked, is that the 'choke'
is not actually a choke but it is in fact a 'starting carburettor', and that in
the Operators Manual (para 6.8 Operation in wintertime) we are advised to 'start
with the throttle closed and the choke activated. (open throttle renders
starting carb ineffective)'.
It has been suggested that prolonging the period when the starting carburettor
is activated (and the throttle closed) may also solve the problem. This is
something
which I am certainly going to try as soon as the Great British weather
gives me a chance.
I hope that the above is helpful to anyone who comes across this problem.
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