| Engine
handling.
For most people the engine in
the nose of the aircraft is the only one they have. Even
if they're flying a light twin - the loss of an engine is a
real problem. With this in mind, it is surprising how
many people know so little about engines and engine handling.
Of concern also, is that people who hire aircraft seem to know
less about engines than people who own aircraft. Remember
- the person who flew that aircraft before you might know very
little about engines!
In this column I'll run through some simple points that will
help you maintain your engine (whether in a hired aircraft or
not - it's still your engine!) for long life, and to prevent
a possible failure on your flight.
Running an engine in:
If you are flying an aircraft with a new or nearly new engine
installed then it is essential that you help with the running
in process. As a general rule, aircraft engines are run-in
at HIGH power. We are looking to try and break the engine
oil down slightly while running the engine in to allow the piston
rings and cylinder walls to lightly "rub" together to form a
clean, matching surface. By using high power the oil
will start to break down (thin out) and allow this to happen.
Also of most importance is the use of the correct oil during
the running in process. Generally aircraft will use RED
BAND (straight mineral) oil during this time. This is
not a synthetic oil, and contains none of the friction modifying
components of "normal" oil. This allows the running in
described above to occur. If you use the incorrect oil
during a run-in then you can prevent the piston rings from bedding
in properly.
Engine warm up:
A crucial part of a flight is the engine startup and then warm-up
prior to takeoff. Many people are keen to get into the
air as quickly as possible, without giving the engine time to
warm up. Naturally, this is more of a problem during winter
than summer. If an engine has not warmed up sufficiently
there are many problems that can occur. The most obvious
is the lack of lubrication due to cold oil. Oil has an
ideal operating temperature that it is designed to work at.
When at this temperature the oil will flow freely throughout
the engine and lubricate correctly. If the oil is too
cold, it won't be able to flow properly, leading to engine damage.
An additional factor with engine warm-up is that the engine
is made up of many different metallic parts, and of many different
metals. It is vital that all these parts are allowed to
reach their optimum operating temperature so that all parts
have expanded correctly with the heat. If some parts are
cooler than others you can induce engine damage due to friction
between incorrectly sized parts.
Shock cooling:
When flying in cruise your engine is operating at a fairly constant
temperature - probably it's optimum operating temperature.
If you arrive in the circuit area, or start a descent and pull
the throttle back to a low setting, the heat source that was
keeping that engine warm is suddenly removed and the engine
starts to rapidly cool. This is most pronounced towards
the front of the engine where the cylinders and engine block
are directly exposed to the cold outside air, when compared
with the rear of the engine where conditions are more sheltered
and therefore much warmer. This differential cooling can
cause the engine block to crack, and the rapid cooling can cause
cylinders to crack. Both of these conditions can cause
and engine failure at worst, and at best you'll have an expensive
bill to pay when you land!
These are just a couple of points about engine handling.
There are dozens more, most of which can be found in some of
the excellent books produced by the engine or aircraft manufacturers.
Have a look at our links on the right hand column to some places
for research about engine handling.
Next time in this column - "Looking after passengers".
Do you scare the life out of your passengers when you take them
flying, or do they come back begging for more? Next time
I'll talk about some ways of making your passenger's flight
just that little more comfortable!
|
