Advances in electronics have revolutionised the ability to monitor, display, log and provide alarm functions for engine operating parameters.

A number of manufacturers now provide a range of systems that can be fitted to nearly any aircraft.

The original engine instruments supplied when most aircraft were constructed in the 1960s and 1970s are, by today’s standards, very basic. Simple aircraft were equipped with a tachometer, oil pressure gauge and oil temperature gauge, while more sophisticated aircraft may have also had a manifold pressure gauge, single channel cylinder head temperature gauge, an exhaust gas or turbine inlet temperature gauge and a pressure based fuel flow gauge.

In many aircraft, some of these instruments were located in positions well away from the central area of the pilot’s vision. Of even more concern, very few of these instruments had any alarm functions. Only a limited number of aircraft were ever fitted with a low oil pressure-warning light.

In some instances these original instruments can produce incorrect readings or misleading information. For example, the pressure based fuel flow indicators indicate a high fuel flow if a fuel injector nozzle becomes blocked. A single channel cylinder head temperature gauge, or EGT, may indicate that the cylinder to which the CHT or EGT is fitted to may be operating within specified limits, but this reading from one cylinder does not mean that all cylinders are within the specified operating limits.

Fortunately, the new engine monitoring systems overcome many of these limitations.

Typically, engine monitors have the ability to accurately monitor, display, log and alarm all engine operating parameters which include: –

  • Individual cylinder head and exhaust gas temperatures

  • Turbine inlet temperatures on turbocharged engines

  • RPM

  • Manifold pressure

  • Fuel Flow (Normally derived from a turbine type flow meter)

  • Oil Temperature

  • Oil Pressure

  • Voltage

  • Outside Air Temperature

The data logging functions of the engine monitors allow all of these parameters to be recorded. Depending on the amount of memory and the configuration of a particular system, engine operating parameters can typically be logged at 6 second intervals for 100 hours of operation This data can be down loaded to other computers, and the complete operating history of the engine graphically displayed and analysed. This feature makes it easy to identify trends, or faults that might have occurred.

In addition to the pilot periodically scanning the engine instruments to detect potential problems, engine monitors also continuously scan the engine operating parameters. Should the engine monitor find any parameter be outside of prescribed limits, it will raise an alarm to draw the pilot’s attention. Typically, alarm conditions are identified by the relevant display changing to red and flashing. This mode of displaying an alarm condition is far easier for the pilot to identify than looking for a needle that is no longer in the green arc. Some engine monitors also include audible alarms that can be linked through the audio panel. For example, if the oil pressure was low, a synthetic voice repeats “oil pressure, oil pressure” in the pilot’s headset.

Other benefits of engine monitoring systems include:

  • Improved management of fuel mixture settings and consequent fuel savings. In some aircraft the fuel savings alone will offset the cost of installing an engine monitor in 300 – 500 hours of operation.

  • Alarm functions for low oil pressure or high oil temperature.

  • Alarm function for high Cylinder Head temperatures.

  • Reduced maintenance cost by promoting better engine operation.

  • Providing accurate data to identify the cause of a fault, and to confirm that a fault has been fixed, again reducing maintenance costs.

  • The ability to identifying particularly damaging engine conditions such as pre-ignition in an individual cylinder. With an engine monitor a pilot will be alerted to a pre-ignition event by a very high and rapidly increasing cylinder head temperature and the pilot can then take suitable corrective action to save the engine.

However, the biggest benefit from fitting an engine monitoring system is the added safety that such a system offers. The safety benefit of engine monitoring systems is that accurate information for the whole engine is displayed to the pilot. In addition the engine operating parameters can be collected and trend analysed.

A review of the operating parameters over time will help to identify if any problems are starting to develop within the engine. Appropriate maintenance can then be planned to rectify these potential problems before they become a safety issue.

Should an engine fault develop in flight, the engine monitoring system provides an early warning to the pilot that the fault is developing or has occurred. If you are ever in the unfortunate situation of having a partially blocked fuel injector nozzle causing a detonation or pre-ignition event, only a multi channel engine monitor will provide timely and accurate information to the pilot so that corrective action can be taken before the engine is damaged. A few extra minutes warning of an engine fault may make all the difference between a successful landing at the nearest airfield and having the engine seize over hostile terrain while trying to reach the airfield.

Engine monitors provide the data so that operators and maintenance personnel can have a high level of confidence that the engine is operating as it should, and warnings when it is not.