User manual

Aerosoft PBY Catalina 1.00 Manual
Page 8 of 100
Failure model and special features
FSX has an extensive failure model but there are a few things missing that we felt should be added.
These failures are typical for the type of aircraft and are not (or not well enough) provided by FSX.
They are certainly important when you fly the more modern versions. They are all museum items
and although mostly lovingly restored and in fine condition, they are many decades old and more
prone to problems when abused. Of course when you fly the war time versions it can be expected
that they are pushed to the red lines on the gauges more often.
Cylinder Head Temperature overheat
When the top of the cylinder is overheating a lot of parts are likely to fail. Sparkplugs, valves and
even the cylinder itself can deform or fail. More likely however is premature ignition of the fuel/air
mixture. This will abruptly reduce power and can cause serious damage. Overheating starts to get
serious at 260°C, but the exact value depends on how fast the CHT is increasing. The faster it
warms up, the sooner the engine will fail.
Cylinder head temperature can be kept within limits by use of the cowl flaps that augment the
normal cooling mechanisms. The onset of overheat is recognized by a quick drop in engine
performance. If CHT can be forced down before the engine fails, then engine power will be restored.
But there is little time.
Oil Temperature overheat
When the oil is too hot it will chemically break down and will get too thin to coat all the surfaces that
need lubrication. This increased friction causes even more heat and as the oil itself is an important
part of the cooling system problems can start slowly but will quickly grow in severity. Opening the
cowl flaps and a richer mixture (more fuel, less air) will reduce the temperature but high RPM will
always lead to higher temperature and in the end you will have to reduce your power settings to
avoid oil temperatures over 100°C. Engine overheat is more likely to happen due to high CHT than
because of high oil temperatures.
Carburetor icing
When ambient temperature is low and there is moisture in the air, ice can form on any surface. In
the carburetor this is even more likely because the air is decompressed and cools down. To prevent
the engines from being strangled the carburetors are electrically heated or as in the case of the
Catalina warmed with heat from the exhaust stacks.
Although FSX does feature carburetor icing, it is a very simple model. In the Catalina there are more
variables used and you will have to be more careful when you are running with low revs or in air
with high moisture content (in clouds or in any reduced visibility condition). It is best to maintain the
carburetor air temperature above 32°C in any possible icing condition to prevent a build-up of ice.
This will keep the air in the venturi above 10°C (as the temperature can drop 20°C because of the
decompression). When icing starts to build up engine power will drop and the engine could even