THE ROBINSON R22, R44 AND R66 ENGINE MONITORING UNITS (EMU)
As the clocks have gone back, and the nights are drawing in then obviously more tea will be consumed, so I thought I would provide you with some light reading whilst you dunk those biscuits!
The Robinson R22 and R44 types have the EMU fitted as standard in helicopters purchased after 15th January 2020.
The EMU is manufactured by Robinson Helicopter Co (RHC) and is assigned to a model and it’s serial number.
The R66 had it’s EMU fitted as standard from day one (1) and is supplied by Rolls Royce and is assigned to the engine (the EMU stays with the engine).
The EMU’s for the R22, R44 and R66 types are intended as maintenance aids only; an independent maintenance record has to be kept and these documents will serve as the official and approved historical records for the type.
The primary responsibility of following and complying with all operating limitations and to report any observed exceedance remains with the pilot.
The R22/R44 EMU
The R22 and R44 EMU’s also house the engine governor (the old governor was analog, the new one is digital).
They are located in the same housing but are totally separate and independent of each other i.e. there is no interaction between them.
The R22 EMU/governor is located behind the pilot’s seat back, with the connection port under the seat, outboard of the rear wall of the seat compartment.
The EMU status light is also located there.
The R44 EMU/govenor is located behind the left hand rear seat back, with the connection port under the left hand seat, under the rear seat compartment wall.
The R44 EMU status light segment is located at the bottom right position in the annunciator panel.
The EMU status light is intended to be used as a reference only for pre flight and maintenance activities and not to be a distraction to the pilot in flight; therefore the EMU segment in the annunciator panel will only illuminate while the annunciator panel test button is depressed.
The pilot is required to check the EMU status during their pre-flight check and must have the battery switched on to do this as the EMU only receives power when the battery is in the on position. After this selection the EMU requires 10 seconds to go through a self test before it will illuminate.
The pilot should occasionally check the annunciator panel caution and warning lights in flight by pressing the annunciator test button
The pilot will see a steady (non flashing light) status light if the EMU is in the normal operation mode.
If the status light is flashing slowly (once every two (2) seconds) it is telling the pilot that there is a fault detected with the EMU or one of its sensors.
If the status light is flashing quickly (four (4) times per second) it’s telling the pilot that an exceedance has been recorded.
A slow or fast flashing light indication would require technical investigation prior to flight.
Once the cause has been identified and corrective action taken, resetting exceedance indications prior to the next flight is highly recommended.
However, if the pilot determines the aircraft is in a condition for safe flight, exceedance reset may be deferred and dispatch allowed.
Reset should be completed as soon as practical.
The R22 and R44 EMU monitors the following systems:
- Engine speed – the signal comes from a probe in the engine accessory gearbox; for independence the engine side of the tachometer still receives its signal from a set of points in the engine right hand magneto.
- Rotor speed – the signal comes from an independent additional Hall effect sender mounted to the main rotor gearbox adjacent to the 2 original Hall effect senders (rotor and low rotor RPM).
- Engine oil temperature – the signal comes from a probe in the oil filter assembly with independent systems for the oil temperature gauge and the EMU.
- Cylinder head temperature – the signal comes from a probe in to a relevant cylinder with independent systems for the cylinder head temperature gauge and the EMU.
- Manifold pressure – is taken from the manifold pressure line.
- Ambient pressure – is taken from the static system.
- Outside air temperature – the signal comes from an independent temperature probe beneath the aircraft cabin.
The data from these systems is stored once per second; however if an exceedance is detected, the exceedance record will be created and the data is stored at a higher rate of 15 times a second.
The values that trigger an exceedance indication are set at levels where maintenance action is required.
This is slightly higher than the operating limit values and allows for some instrument tolerance, which is intended to avoid nuisance indications.
Therefore from a technical data view point it is possible to see a number in the ‘maximum occurrence’ column slightly higher than the ‘operating limit’ but not shown as an exceedance (not shown in red).
The EMU data can be accessed using PC or Apple devices. If you are using an Apple device there is an application that can be downloaded from the Apple application store.
The R66 EMU
The R66 EMU is located behind the right hand rear seat back, with the connection port under the seat, outboard of the rear wall of the seat compartment.
The EMU status light segment is located at the bottom right position in the R66 annunciator panel.
The EMU status is intended to be used as a reference only for pre flight and maintenance activities and not to be a distraction to the pilot in flight, therefore the EMU segment in the annunciator panel will only illuminate while the annunciator panel test button is depressed.
The pilot is required to check the EMU status during their pre-flight check and must have the battery switched on to do this as the EMU only receives power when the battery is in the on position and the EMU requires 10 seconds to go through a self test before the segment will illuminate.
The pilot will see a steady (non flashing light) status light if the EMU is in the normal operation mode.
If the status light is flashing slowly (once every two (2) seconds) it is telling the pilot that there is a fault detected with the EMU or one of its sensors.
If the status light is flashing quickly (four (4) times per second) it’s telling the pilot that an excellence has been recorded.
A slow or fast flashing light indication would require technical investigation prior to further flight.
The R66 EMU monitors the following systems:
- Measured Gas Temperature (MGT) – the signal comes from the MGT harness, with the thermal couples in the engine gas path between numbers 2 turbine wheel (gas producer turbine) and the number 3 turbine wheel (power turbine).
- Torque – taken from the engine torque meter oil system.
- N1 speed – taken from the N1 engine compressor speed sensor.
- N2 speed – taken from the N2 engine power turbine speed sensor.
The EMU will also record engine starts when the N1 exceeds 30% and the MGT is at least 343 deg C.
The R66 EMU is intended to be used as a maintenance aid.
It is the pilot’s responsibility to report any observed exceedances and the operator’s responsibility to maintain a record of engine starts and time in service.
The EMU records exceedance of the Rolls-Royce engine limits, not the RHC airframe operating limits.
The primary responsibility of following and complying with all operating limitations and to report any observed exceedancs remains with the pilot.
Knowledge is flight safety helping to keep your RPM in the green.
R
