We were both staring at the yellow caution message on our EICAS screen, “IDG1” as I exited the runway at the first turnoff. It extinguished and was shortly replaced with a “GEN 1 OFF” caution message. The caution message surprised us both, but we performed and reacted well. I was more annoyed by it than startled; it being a yellow ‘caution’ message had a lot to do with it. If a red ‘warning’ message is received on takeoff, it most likely involves one of the engines, and that would get my blood pressure up. As we left the runway my good First Officer (funny and entertaining one too) told the pax (passengers) to stay seated on the PA and then transmitted to the control tower that we had aborted our takeoff.I had been there and done this before as a First Officer. I knew that this message was no fluke; it was a real problem that would occur again on a subsequent takeoff. We taxied back to the ramp, called maintenance are wrote the problem up in the logbook, and started the ‘circus music’ with passengers wanting to leave the flight and go back home.
FO ‘Rob’ had also called our operations people, a gate agent (CSA) met our flight with news that a good number of passengers would now miss their connections in Charlotte. We ended up losing half a dozen of them, but I had a little difficulty sympathizing with them as to why. When an airline strands a passenger in their travels due to a mechanical problem, they are obligated to put that passenger up in a hotel for the night, by law. The guess the passengers who got off the plane figured another night in their own beds was better than in a hotel, even though they were losing a significant amount of time at their destinations in the process.
It was our good fortune that we were at one of our maintenance bases. The mechanic came over quickly, and after a short conversation about what exactly happened it looked like they were going to “MEL” the left engine electrical generator. MEL means minimum equipment list, and is a long list that stipulates what components we can fly with while they are broken and maintenance is deferred, or in other words, the repair of said component is put off till a later time.
The message we got, “IDG1”, referred to our integrated drive generator, a combination of an engine driven generator and a constant speed drive unit (CSD). The CSD is similar to a car’s automatic transmission. Filled with oil, it turns an engine’s variable rotation speeds into a constant RPM, which rotates the electric generator. If the oil level inside the CSD is too low, the CSD can disconnect from the generator, and possibly get too hot if it doesn’t, which will also trigger a disconnect. If our case the IDG sensed that the oil level was too low on takeoff, as we started to accelerate. The acceleration caused the oil in the IDG to slosh just enough to trigger the IDG caution message, and resulted in the generator coming ‘off-line’.
There are many balls to juggle when you have a gate return. Passengers who are going home have to have their bags returned from the cargo hold. The maintenance has to be completed and the aircraft has to be released back into service. The Dispatcher is preparing another flight release, which can be put back in the system till the aircraft is returned to service. I try to coordinate all that and keep the passengers informed, every ten to fifteen minutes if possible. Sometimes there are unexpected delays in getting all this done. This time, everything worked like clockwork in getting us going again, though. An hour after we started engines the first time we did it again with one less electrical generator, and took off for Charlotte.
There were differences, as you might imagine. Our MEL (Minimum Equipment List) dictated that we can fly passengers with an inoperative engine generator, but to compensate for that we have to operate the APU (Auxiliary Power Unit), a small engine in the tail of our jet, for the entire flight. The APU produces electrical power and air for engine starts and air conditioning, and it has a lower maximum altitude for operation than the altitude our flight plan had been filed for. Consequently our dispatcher refiled our flight a few thousand feet lower. Normally we have two electrical generators active in flight; with the APU on we would regain that second generator.
Airline flying is the safest form of travel for a reason: the many safeguards and procedures that are built into our operations help to produce a safety factor that is very high. Although it might be frustrating when your flight gets delayed, have security that your pilots, flight attendants, and mechanics have the integrity to do the right thing when something on your jetliner breaks.And I do believe this advice, I’m not just saying it, in spite of all the media attention which has lately been questioning the effect that maintenance and scheduling pressures have on airline safety.
May God bless you, and thanks for reading my blog.