The Legacy 500, the world's first fly-by-wire super-midsize business aircraft, was expected to have completed its first flight by early this month, triggering an exuberant, but very brief celebration at 's headquarters in Brazil. The aircraft was slated for certification in 2012, but that original development schedule assumed first flight in third or fourth quarter 2011. That target day passed because Parker Aerospace, supplier of the three-axis fly-by-wire (FBW) control system, failed to earn a critical software approval, thereby grounding the flight test program for a year or more.
Parker's problems were traced to improper software documentation for the remote electronic units (REUs), the computers that command movement of the flight control actuators. Demonstrating strict FBW software verification and validation to airworthiness authorities is as critical to safety of flight as showing that you've used only aircraft grade hardware for the flight control computers and flight control surface actuators. Software glitches potentially can have fatal consequences, so ground testing of the aircraft at São José dos Campos has been limited to 80 kt., well below liftoff speed at the lightest weights.
Upon learning of the depth of Parker's problems, Embraer was compelled to send in its own team of software engineers and also an expert crew from veteran FBW firm. Ultimately, the aircraft manufacturer transferred responsibility for FBW software development from Parker to BAE Systems, with Parker's Irvine, Calif., division supplying hardware components.
Parker's woes doubtlessly blindsided the Brazilians because the California firm supplies key FBW components for the latter's ERJ 170/190 regional airliners. But the Legacy 500's three-axis FBW is considerably more capable and more complex than the two-axis digital electronic controls installed on Embraer's.
Fortunately for Embraer, BAE Systems is intimately familiar with the overall Legacy 500 FBW control system because it has supplied both hardware and software to Parker for the main flight control computers (FCC) from the onset of the program. The FCCs are the top-level digital brains of the FBW system that tell the REUs how to command the control surfaces. Embraer officials said that, in contrast to Parker, BAE Systems' FCC hardware and software development was “flawless” throughout the program.
“It's behind us now, thank goodness. We're moving on. All the tough questions are going to come [out]. How did we get here? What did we learn? And all of that stuff will be handled by Parker. I guess they're the people who have learned the most from this,” says Ernest Edwards, president of Embraer Executive Jets. So, how did Embraer get the FBW development program back on track?
“In a nutshell,” says Edwards, “it took a lot of hard work and dedication by all the teams involved. Once we identified the delay, it was a case of getting all the parties around the table and saying 'OK. Let's get involved and find out what we need to do to minimize this delay . . .' It was more a team effort than any individual party. It wasn't so much of the problem being a problem, the problem was the delay and how do we recover.”
Edwards' “team effort” reference soft sells the role played by Embraer's and BAE Systems' engineers in rectifying the FBW software problems. Without their involvement at the “25th hour,” the aircraft still might be a hangar queen.
“What's past is done and we have a great airplane,” Edwards concludes.