Yak 18T Flight Operations Manual
Page 35 of 82
Disclaimer: This manual is to be used as a reference only, it is based on translated Yak 18T Flight Operations
Manuals and has not been approved by the Yakovlev Design Bureau or any other authority.
• using the thrust lever SET a speed of 70% with the propeller's position SET to FINE
PITCH
• SHIFT the propeller pitch lever to the COARSE PITCH position (fully backwards), in this
case the crankshaft speed will be reduced to approximately 53%
• SHIFT the propeller pitch lever to the FINE PITCH position (fully forwards), the
crankshaft speed will increase up to the initial value of 70%. Notice a short-term oil
pressure drop at the engine inlet. Up to 2 kgf/cm² is allowed with a subsequent recovery
during 8-11 seconds
CHECK for the correct operation of the propeller and rpm governor at the equilibrium
speeds, for this purpose proceed as follows –
• using the thrust lever SET a speed of 70% with the propeller SET to a FINE PITCH
position
• using the propeller pitch lever SET a speed of 64%
• by MOVING the thrust lever smoothly back and forth but not against the stop, make
sure that the engine crankshaft speed remains UNCHANGED
• the engine speed can be increased or decreased by 2-4% respectively via an abrupt
forwards and backwards motion of the thrust lever. It’s equilibrium rpm will then be
restored in 2-3 seconds.
CHECK the engine during 20-30 seconds. To do this, perform the following procedures –
• SET the propeller control lever to the position FINE PITCH forwards to the fine-pitch
stop (decrease the propeller pitch completely)
• SHIFT the thrust lever smoothly forwards against the stop
The readings of the engine control instruments must be as follows –
Crankshaft rational speed 95%-99%
Supercharger pressure Po+125±15mm of Hg
Petrol pressure 0.2-0.5 kgf/cm²
Engine inlet oil temperature 40°C-75°C
Oil pressure 4-6 kgf/cm²
Cylinder head temperature ≤ 220°C
Carburettor inlet air temperature ≥ +10°C
CHECK the engine running at minimum speed (rpm) with the propeller SET at fine pitch and
the thrust lever SET fully backwards. The engine should run steadily, the instruments
readings must be as follows -
Engine speed (rpm) ≥ 26%
Oil pressure ≥ 1.0 kgf/cm²
Petrol pressure ≥ 0.15 kgf/cm²
To prevent the spark plugs from getting FOULED, the duration of the engine running at
minimum rpm should NOT EXCEED 5 minutes. Also note that the low voltage generator
light is expected to illuminate.
CHECK engine acceleration response. For 2-3 seconds put the thrust lever smoothly from
the idling stop fully forwards against the stop, in this case the propeller pitch lever must be in
the position FINE PITCH. Transition from the minimum speed (rpm) to the take-off regime
should be performed smoothly during 3 seconds. To provide the normal acceleration
response, the temperature of the cylinder heads should be at least 120°C and the oil
temperature at the engine inlet must be not less than 40°C
NOTE: the pilot can TEST of the engine acceleration response in flight. This should be
performed at an IAS of 160km/h
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