Nr,
Sorry to clash, there are indeed breather pipes on the R22 and it has no vent holes in the caps to my knowledge.
The fuel tank vent pipes are hidden behind the mast cowling and jointed in at least one place by soft tubing (plastic material).
In at least one case in the UK the soft tubing had 'kinked', causing a lack of venting to the tank. The result was an engine stoppage due to fuel starvation.
A directive was issued and some aircraft had these pipe assemblies changed for a type that
had the fault designed out.
The problem has not recurred in the last 3 or 4 yrs (to the best of my knowledge).
BEWARE if the dual fuel gauges do not decrease at a similar rate during flight (from equalised contents) because this can indicate that one tank's vent is blocked.
The second occurence (that I have not 'written up yet')happened in California, the inside of the air intake tubing delaminated and blocked off induction. The engine stopped in the hover.A friend of mine was the pilot. He landed it with a slight yaw but held it upright and no damage was sustained, no injury either, thankfully. He made a really good job of a 'REAL' EOL in the hover!
The air intake tubing has been changed under directive, favouring a type and construction that cannot allow delamination.
SPS