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Instrumentation

The power plant related instruments are mounted on the instrument panel in front of the pilot in two vertical rows. Typically the instruments are laid out as shown in the following picture.

Torque guages

The torque guages are mounted at the top of the engine instrument cluster and provide an indication of positive engine torque that is being delivered to the propeller. Positive or negative torque can exist at any time however positive torque gives the pilot an indication that the engine is driving the propeller and not the other way round.

  • The torque guages used in the Conquest are mounted at the top of the instrument cluster
  • The torque guages are calibrated in ft/lbs and require electrical power for operation.

Torque indications are measured by a torque meter which is an oil metering device. The torque meter is fed a constant oil inlet pressure from the engine lubricating system and then returns the oil back to the gearbox after the metering process. The amount of metering require by the torque meter is a direct relationship to the torque being produced by the engine.

The torque meter then sends the metering pressure to a transducer which transfers the pressure into an electrical signal and sends it to the electronic fuel computer and the torque guage. The torque guage is calibrated in foot pounds (ft/lbs) and requires electrical power for operation. The guages will stow into the ‘OFF’ position when the batteries are off.

Exhaust Gas Temperature (EGT) Guages

The EGT guages are typically mounted directly beneath the torque guages in the engine instrument cluster. The temperature indication shows the temperature of the combusted gases in the exhaust duct which are measured by eight thermocouples which are wired together in parallel to give the best “average” reading.


The EGT guages used in the Conquest are mounted beneath the torque guages

The Conquest EGT system utilises three different forms of EGT which are:

  • Raw EGT,
  • Compensated EGT, and
  • Calculated EGT.

Raw EGT is the uncorrected temperature which is measured in the exhaust duct by the thermocouples.

Compensated EGT is the measured raw EGT which is compensated so that both engines will show the same rated torque at the same EGT. This compensated temperature is corrected by an engine mounted EGT compensator, which is adjusted for that particular engine, i.e. EGT compensators cannot be changed between engines.


The EGT compensator shown in the EGT indicating system

During Manual mode operations the indicated EGT for all operations is Compensated EGT and is relative to the maximum EGT of 770° Celcius for one second. The maximum EGT which can be set by the pilot during manual mode operations in flight is found either in section 2 of the flight manual, reading the inner scale of the OAT guage, or by matching the torque or EGT against a normal mode engine.

Table 2-5 from section 2 of the flight manual is the most accurate method of determining the maximum temperature that can be set by the pilot on the EGT guage. This table requires the pilot to extrapolate the temperature by entering the table using the current in flight conditions to find the maximum EGT, as previously stated, this Extrapolated EGT is the most accurate EGT for the current in flight conditions.

Should the pilot change height or power settings then a new maximum EGT will need to be extracted from this graph. It should be reiterated that in manual mode, the maximum EGT limit in flight is related to the 770° C temperature limit and may be higher than the normal mode single redline limit which is marked on the EGT guage.


The EGT guages have a 450° C single redline limit marked that is only used during normal mode ops

The second method of determining the maximum in flight EGT during manual mode operations is by using the OAT guage mounted on the far left hand side of the instrument panel. This is a much faster method than looking up the temperature from table 2-5 in the flight manual, however it is a much more conservative figure and is not as accurate as the table 2-5 method.

To use this method during flight, the pilot simply needs to observe the current in flight temperature from the OAT guage and use the figures from the inner portion of the guage as the maximum temperature to set for maximum EGT. Remember, use the figures from the inside of the guage as the maximum EGT, not the indicated OAT (this won’t even come close).

The third method of setting the maximum EGT on a manual mode engine in flight is by setting the fuel flow or torque against a normal mode engine. This method obviously requires that one engine is operating with the fuel computer off and the other engine with the fuel computer on.

This method requires that the normal mode engine be operated at 100% RPM to match the manual mode engine RPM followed by the pilot matching either the fuel flow or the torque (whichever is reached first) of the manual mode engine with that of the normal mode engine. This method is also a more conservative method than the table 2-5 method but is much quicker and easier.

It should be noted that this last method can be used in the event of a single EGT guage failure in both normal and manual mode operations.

During operations with either one or both engines operating in manual mode it should be noted that the propeller syncrophaser becomes inoperative as does the Torque, Temperature Limiting capability of the manual mode engine.

Calculated EGT is the last form of EGT used by the Conquest and is the usual EGT indication read by the pilot during normal mode operations. Calculated EGT is basically a compensated EGT that has been modified by the electronic fuel computers to conform to a Single Red Line (SRL) limit of 450° C between 96%-100% RPM.


The EGT guages are marked with 450° C Single Red Line limit as this is the typical max EGT

Because calculated EGT is modified by the electronic fuel computers it is much easier for the pilot to set the maximum EGT during all phases of flight and requires no complicated calculations on the pilots behalf what so ever. This also means though that Calculated EGT is only possible during normal mode operations as the fuel computers do all the work for the pilot.

Therefore during normal mode operations the pilot must never allow the maximum EGT to exceed this single redline limit of 450° C. This is not the case during manual mode operations as the pilot can use on of the three earlier methods which may allow the pilot to increase the EGT beyond 450° C to whatever the extrapolated limit maybe.

Calculated EGT is controlled by an 80% switch in the fuel computer and is inoperative below 80% engine RPM. Below 80% RPM the indicated EGT is compensated EGT and is related to the 770° Celcius limit. The EGT guages require electrical power for operation and will stow into the ‘OFF’ position (see EGT pic above) with the battery switches 'OFF'.

Engine RPM Guages

The RPM guages are typically mounted directly beneath the EGT guages in the engine instrument cluster. The RPM is indicated on a dual analogue/digital guage which is driven by a tachogenerator which is mounted on the reduction gearbox.


Engine RPM guages mounted below the EGT guages.

Both the sweep needle and the digital display are calibrated in percentage RPM with the digital reading showing percentage RPM to one decimal place. The RPM guages require electrical power for operation and will show a blank digital face and a zero percent sweep needle indication with the baterry switches 'OFF'.

Battery switches ON
Battery switches OFF

Fuel Flow Guages

The fuel flow guages are typically mounted directly beneath the RPM guages in the engine instrument cluster. The fuel flow from each engine is indicated on an analogue guage which is compensated for temperature and indicates the mass flow from each engine calibrated in lbs/hr flow.


Fuel flow guages mounted below the Engine RPM guages.

The fuel flow guages are operated by a transducer which is mounted down stream of the fuel control unit which senses the the fuel flow and converts this into an electrical signal for display to the pilot on the fuel flow guages. Electrical power is required for the fuel flow guages to operate and will stow into the 'OFF' position with the battery switches 'OFF'.

Fuel Quantity Guages

The fuel quantity guages are typically mounted at the bottom of the engine instrument cluster. The fuel quantity for each tank is indicated on an analogue guage which is calibrated in fuel pounds not fuel litres allowing easy calculation from the pilot the aircrafts remaining endurance.


Fuel quantity guages located at the bottom of the engine instrument cluster

Oil Temperature/Pressure Guages

The Oil Temp./Press. guages are typically mounted directly beneath the fuel flow guages in the engine instrument cluster. The oil temperature and pressure for each engine is indicated on an analogue dual purpose guage which requires electrical power for operation. An OIL PRESS warning light mounted on the annunciator panel will also illuminate when the oil pressure drops below 40 PSI. Note: This warning light operates independently of the oil pressure/temperature guage, therefore providing a means of checking a faulty oil pressure guage.

Oil pressure/temp. guages
Oil press. warn. light which illuminates < 40 PSI.

 
Instrumentation


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