Changes of power and speed produce slight changes in directional trim.
Stability
The aircraft is dynamically stable about all axes.
Ample trim control is available for all conditions of flight and the aircraft holds
the trimmed speed well.
10 Cruising
The maximum recommended engine speeds for cruising are 2500 rpm at sea
level, 2650 rpm at 5000 feet and 2750 rpm at 10,000 feet. These figures will
produce approximately 70% power at the given altitudes.
Up to 5000 feet this power will produce an IAS of approximately 100 knots,
giving a true airspeed of nearly 105 knots. For actual figures on range and
endurance, fuel consumption etc, refer to Chapter 6, Cruise Performance Table.
11 Mixture Control
When operating at altitudes of more than 5000 feet above mean sea level or at
any altitude where best power is required, adjustment of the mixture strength is
necessary.
This is done by pulling the knob out toward the “LEAN” position until maximum
RPM is obtained while holding the airspeed steady and with fixed throttle, then
returning the control toward “FULL RICH” until RPM drops just perceptibly.
This procedure produces best power with the mixture slightly on the rich side to
prevent
overheating.
Re-adjust the fuel-air mixture for each change in throttle setting, altitude or
carburettor
heat.
Pilot’s Operating Handbook VH-SJH Chapter 5
Handling
12 Carburettor Icing
Carburettor icing on the ground has been dealt with earlier in this Chapter.
Carburettor heat should be used in flight at the first indications (engine
roughness, or loss of rpm) that ice may be forming.
To remove carburettor ice first apply full heat, then by trial and error determine
the minimum heat required to prevent any further accretion, using full heat to
remove any build-up of ice during the process.
With full carburettor heat rough engine operation and loss of power will result.
In addition to this the engine will run rough due to an over-rich mixture.
In such cases the mixture should be leaned in accordance with Paragraph 11
except that it must be remembered that too lean a mixture will cause overheating
and detonation. The mixture must not be leaned unless an increase in engine rpm
results.
13 Vapour Lock
When operating in very hot weather there is a possibility of vapour forming in the
fuel suction lines.
Idling on the ground, in such circumstances should be reduced to the minimum
and rpm maintained at a higher than normal figure.
Descending to lower altitude may restore any power loss due to vapour formation
at high altitudes, normally above 10,000
feet.
14 Pre-Stalling and Pre-Aerobatic Check
Preliminaries – Check:-
Height………………………………Sufficient to recover by 3000 feet above
terrain
Airframe……………………………Flaps and trim
Security…………………………….Canopy, harnesses and loose articles
Engine………………………………Normal engine operation. Fuel contents,
fuel
pump
and
mixture
rich
Pilot’s Operating Handbook VH-SJH Chapter 5
Handling
Location…………………………….Not in controlled airspace. Not over a built
up are. Within gliding distance of a forced
landing field.
