You Want It When???

While I was at work the other day a call came from Maintenance Control. There was a plane headed our way with a #1 engine bleed air issue. We get calls like this all the time and so it was not all that uncommon to have them request that we check it out. The problem came about when they said we HAD to have it fixed in two hours to make a flight to Midway.

A quick check of the history on the #1 engine bleed air system revealed that it had a 45 day history of problems! In other words this bleed air system has been acting up for over a month now and they wanted it fixed in two hours. I thought it was pretty ballsy of them to say we had to get it done, and I let the lead know how I felt about it. Luckily that day we had a guy on shift who is really good with engines and engine systems. He was able to figure out what was wrong and kick the plane out in about an hour and a half. Anyone who has worked on engine bleed air faults knows that often times multiple high power runs are required to narrow down and fix a problem.

Part of the issue is that the 737-700 is using the same bleed air valves and regulators as the 737-300 series. These valves seem to work well on the -300 engines (CFM-56-3) and are pretty reliable. These same components are not very reliable on the -700 engines (CFM-56-7). Boeing has not figured out why this is so, or at least they are not saying publicly why this is so. Through the grapevine we have heard that the -700 engines put out a different harmonic vibration than the older engines and this small vib is playing havoc with the components. Whatever it is they are still working on a fix!

More troubling is the "you have to get it fixed" statement. There is no way that I have to fix anything in an allotted time period. Make sure that you as a mechanic do not fall into this trap. Pressure is part of the job as I have mentioned before, however, when a component has a bunch of history, going back a lot of days, with a lot of different mechanics and parts thrown at it, proceed with caution. Do not let Maint. Ctrl or any one tell you how quickly you should work. In my example it all worked out fine but it could have easily gone the other way with the plane grounded and not leaving until the next morning. Thank God we had Dark Cloud there to work it (yes that is what we call him).