Turbo 310R User Guide
This automatic control of the waste gate by the turbo system will provide,
approximately, the placarded manifold pressure during single engine climb,
however all engine climbs at higher speeds or with closed cowl aps may re-
quire some adjustments to the throttle to maintain the proper manifold pres-
sure.
When the waste gate is fully closed, any change in turbocharger speed will
equal a change in engine operation. Anything that results in an increase or
decrease of turbine speed will cause an increase or decrease in manifold
pressure.
Manifold Pressure Variation vs. Altitude
As noted previously, at full throttle the turbocharger is capable of maintaining
the maximum allowable 32.0 inches Hg. manifold pressure up to 16,000 feet.
The RPM range for maintaining the maximum allowable manifold pressure is
2500 - 2700 RPM; if a lower RPM range is selected for a cruise climb such as
2300 - 2400 RPM, the manifold pressure may start to drop before 16,000 feet.
The turbo system controller does not include a pressure compensated waste
gate and therefore only operates automatically at full throttle. If a lower mani-
fold pressure is selected by the pilot, the throttle will require manual advances
to maintain the selected manifold pressure as the aircraft climbs.
Manifold Pressure Variation vs. Airspeed
When the aircraft is operated at full throttle at altitudes below 16,000 feet,
the waste gate is open, therefore changes in airspeed have little eect on the
manifold pressure.
At high altitudes, once the waste gate is closed, dierences in airspeed will
have a small, but noticeable, eect on manifold pressure.
Fuel Flow Variations vs. Manifold Pressure
This is one area where we are forced to deviate from real world behavior due
to a limitation within the X-Plane platform. Proper behavior is that fuel pump
output and fuel ow is regulated by engine speed and compressor discharge
pressure. The practical (real world) end result is that fuel ow adjustments by
the pilot are minimized greatly, reduced to small initial adjustments on takeo
or climb-out for the proper rich setting, lean-out in cruise, and return to full
rich for approach and landing.
However, X-Plane does not model this behavior correctly, instead choosing to
model ambient pressure only; this causes the turbocharged engine to behave
as a normally aspirated engine would in regards to fuel ow.
As such, as the aircraft climbs, the fuel levers will need to be managed by the
pilot in order to lean the fuel mixture so as to allow the engines to achieve
rated power and proper climb rates.
So - during the climb it is advised that the pilot should strive to maintain an
EGT of 1050° F by progressively leaning the fuel mixture, before leaning for
cruise power once at altitude.
Momentary Overboost Of Manifold Pressure
Under certain circumstances, such as rapid throttle movement, it is possi-
ble that the engine can be overboosted above the maximum allowable 32.0
inches Hg. manifold pressure. This could occur during the takeo roll or dur-
ing a change in full throttle operation while in ight. Slight, but momentary,
overboosting is not considered detrimental to the engine, but can usually be
controlled by slower throttle movements.
Altitude Operation
A turbocharged aircraft is capable of climbing faster and higher than a nor-
mally aspirated aircraft can, as such, the pilot should be aware of the possibil-
ity of fuel vaporization being encountered.
It is recommended that the auxiliary fuel boost pump switches be turned ON
when climbing to altitudes above 12,000 feet. In addition, the fuel pumps
should be left ON for several minutes after cruise in level ight has been es-
tablished.
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