777-200LR Flight Test Journal: Archives

12 October 2005

The brains of the engine

Shahrokh Ghayem, Propulsion Controls Lead Engineer

Mathew Metcalfe, Propulsion Controls Engineer

Peter Douglass, Propulsion Controls Engineer

Grazyna Ostrom, Propulsion Controls ATF

Kevin Brown, Propulsion Controls Engineer

Kyle Peterson, Propulsion Controls Engineer

As the Flight Test program for the 777-200LR Worldliner heads into its final few weeks, final certification work is underway on the Electronic Engine Control (EEC). That is our piece of this glorious machine.

The EEC is basically the brains of the engine. In reality, it is also an avionics box that resides on the engine. Its purpose is to control the engine functions, interface with the aircraft and allow the pilots on the flight deck to modulate thrust and control the function of the engines. It also provides indication to the pilots of the health of the engines.

For the 777-300ER and -200LR, General Electric developed a new generation of EEC, known as Full Authority Digital Electronic Control-3 (or FADEC3). It contains all new hardware with more memory, a new processor, and more thorough capacity in a smaller space.

In terms of flight testing, a lot of what we do is ride-along testing. Our box is just on there controlling the engines, and we monitor it. We get data off of everyone else's flight test, especially if anything unusual or interesting happens. There have been no problems related to propulsion or our function. We get daily reports from the people who are flying along and every day the reports come back and say, "No problems or issues." Don't get us wrong ... we enjoy the fact that everything is going so well. It's not bad, just a little monotonous.

In addition to supporting everyone else's testing, we have our own dedicated testing, which we are doing to look specifically at EEC functions - like thrust settings for various takeoffs and different runway altitudes and temperatures. We have our own dedicated certification tests to evaluate those, and we also look at some in-flight conditions. For instance, we'll shut down an engine in flight and restart it just to demonstrate that it can be done. We also do some refused takeoffs - heading down the runway and then putting on the brakes, pulling the throttle back and stopping.

The EEC is actually part of the engine system. As such, it gets certified by the engine manufacturer. We are not really certifying how the EEC controls the engine. We are certifying that it meets our airplane requirements in terms of performance and in terms of integration with the airplane.

Our work on this program started way back before the first 777-200LR was built. Nearly three years ago we went through and verified a lot of the functionality in the Propulsion Integration Laboratory (PIL). The PIL has the full avionics system for the airplane. It has all the displays, the avionics bench and a simulated flight deck. The engine, the airplane and the atmosphere are all simulated. We have a large rack of electronic equipment that translates data from simulated into real signals, which we then feed into the EEC. So, the whole purpose of the PIL is to trick the EEC into thinking it is really running an engine in flight. After you do that, you can introduce faults and test just about anything you want.

We spent several months in the PIL verifying a lot of the functionality, especially the Engine Indicating and Crew Alerting System (EICAS), which generates the messages that the pilots see if there was some condition they needed to be alerted to - things like cautions, warnings and advisories. In addition, we perform fault insertion testing to check the engine related maintenance messages to which helps engine maintainability and reliability.

By doing all this work in the PIL, we save a lot of money because flight testing is very expensive. It also allows us the opportunity to solve problems ahead of time and ensure that the flight test program is able to run as efficiently as possible and stay on schedule.