Cessna 172H

(Tony Roberts) writes:

In fact, although everyone appears to agree that the 0300D carb is
more prone to icing than the Lycoming installed after 1967, if you
read the stats on accidents due to carb ice you will find that the
Lycoming has more than the Continental. Continental pilots are more
conscious of carb icing, and use carb heat to check for icing more
often.

Can you give a reference for the stats for carb-icing accidents? Are
they simply counting accidents, are they comparing the number of
accidents to the number of aircraft registered, or are they comparing
the number of accidents to the number of flight hours?

According to a rough count at the FAA database, about two thirds of
the 172's currently registered in the U.S. are models that shipped
with Lycomings. Furthermore, in my (still limited) experience, the
Continental 172's tend to be people's babies, flying somewhere between
25-100 hours/year, while a good number of the 172M/N/P/R/S planes are
flying hundreds of hours/year in flight school lines and FBO rental
fleets (unfortunately, I don't know any source for actual flight hours
per model type).

Taking all of this into account, I'd guess that Lycoming 172's fly
many times as many hours/year as Continental 172's do, so they would
need many times as many carb icing accidents/year just to be even with
the Continentals, not to mention more dangerous.

[snipped out section on ground leaning]

Also (stand by for controversy I add Avblend to the oil. They claim
that it helps prevent sticking valves. I cannot say that it does or it
doesn't. What I can say is that 2 months after buying the plane we had a
stuck valve - since then we have used Avblend and had no problems.

Were you ground leaning as aggressively before the stuck valve as you
are now? If so, the more obvious explanation would be the leaning,
not the oil additive.


All the best,


David

Hi David

Can you give a reference for the stats for carb-icing accidents?

Here is a quote fron Gene Whitt -

On average there have been 35 unexplained 'engine failures'
per year. Most of these have been Lycoming and attributed
to carburetor icing. Where POHs do not recomment heat unless
required, pilots lose the Continental sensitivity to pick up
on an unexplained rpm drop. Solution: Fly Lycomings as
though they were Continentals. The forementioned 35 are due
to complacency in the use of C.H.


Were you ground leaning as aggressively before the stuck valve as you
are now? If so, the more obvious explanation would be the leaning,
not the oil additive.

I was, but at that time I had a partner, so I cannot say for sure what he
was doing.
But the oil additive is cheap - and FAA approved. The valve job was
$650.00, so I see it as buying insurance.
I really don't want to try flying without it and then end up with another
stuck valve. That is probably why these guys sell so much additive -
people don't want to risk it

--
Tony Roberts )
PP-ASEL
VFR-OTT - Night
Cessna 172H