Engine gremlins

"You see that?"

We were flogging ye old jet on day 2 of a planned 3 day, east bound at 38,000 feet. My partner in crime was looking at the #2 engine running temperature (called ITT), and oil temperature and pressure. Though still well within limits and not changing, all 3 were noticeably different than they had been the flight before, with the ITT and oil temp. up, oil pressure down. The temperature on the departure runway had been near 100 and the air temperature during climb had been 15 degrees above standard all the way through 25,000 feet - slightly elevated engine temperatures would not be a surprise.

But at 38,000 feet the outside air temperature had fallen back to standard, checklists had been run, we were "on the step", and there was no good explanation for what we were seeing on the gages . 

"Yeah, I do."

In the back three VIPs were heading to a high power meeting over acquisitions; or something - they don't usually tell me much of what they are up to and the truth is - I don't really care. Getting them on the ground safely is the main concern, a distant second is getting them on the ground where they want to be. But even if the offending engine required a shut-down (and there was no indication such was impending) by the time the jet drifted down out of 38,000 feet the destination would be just off the nose anyway.

I know the movies suggest that an airplane with an engine out makes a sreaming, scary plumet to the ground with the crew scrambling to save the day and passengers crying and praying in the back.  In reality the first thing we do if we decide an engine needs shut down is get out a check list and calmly read it through.  Then we tell Air Traffic Control what we need and start down.  A 1000 foot / minute descent out of 38,000 feet will take the obvious 38 minutes and cover about 300 nm.  And, if we do it right, the passengers will not know anything is amiss until we turn around (its a small jet) and tell them so.

The elevated ITT suggested a minor leak of hot, compressed air from a fitting or something, maybe out of the bleed air valve itself. I have seen this failure mode a couple of dozen times during my years of turbine flying. It was something we would have to look at and fix before leaving on day 3, but it is normally a pretty minor repair. The oil temperature and pressure were a puzzle, directly related to each other but not normally a factor in a bleed leak. Yes, a bleed leak may dump hot air into the cowling, but the cowling around a running jet engine is ususally a pretty warm place anyway. Oil coolers have a stream of air flowing through them sourced directly from the outside where, at that moment, the temperature was some 40 degrees below zero.

I don't like being puzzled at 38,000 feet doing nearly 500 mph over the ground. It looked like Kintala's engine gremlins, having been banished from the boat, had followed me to the airport. Dropping the #2 engine cowling, after the passengers were on their way and out of sight, exposed the gremlin's handy work. Plastic spiral wrap hung from wires like long strings of hardened pizza cheese and there was a scorch mark on the inboard lip of the cowl. A quick engine run uncovered a failed bleed line that, in addition to the other damage,was flooding the oil cooler with a blast of air directly out of the burner section of the engine. We were putting A LOT of hot air in the cowling.

I hadn't seen that happen before.

Day 3 didn't happen. The VIP passengers were left to their own devices but eventually got back to home base, beating us by many hours. The first attempt at getting the correct part failed. (Sound familiar?) The second box air shipped across the country held the right one. A night flight west across one time zone and a 2 hour drive to the lake had me boarding Kintala just after midnight.

We are going to cove out tonight, the second time Kintala has been off the dock since her engine went back in service.

I hope I lost the gremlins back in Pittsburgh. They can follow someone else around for a while.