No APU Becomes A Big SNAFU

December 12, 2007

in Airplane Stories

On November 27, 2007, I was on Delta flight 1760 from Salt Lake to Orange County. The flight was boarding, and despite it being below freezing outside, the cabin temperature was in the high 80s. After sweating for several minutes following the scheduled departure, the captain came on and said the auxiliary power unit (or APU) was not functioning, but that it was “perfectly safe and perfectly legal” to take off without it. That explained why it was so hot. He said we were waiting for a starting cart to get the engines going in our MD-90.

After several abortive attempts to start the engines, they finally got them running and the AC started to work. We took off uneventfully, but about 10 minutes into the flight a generator on one of the engines went out, which meant that instead of a triple redundant power supply we were down to one and looking at complete failure of the electrical system. We went back to Salt Lake and were stuck waiting for 3 hours for a replacement plane which was not “perfectly safe and perfectly legal” to fly. It had a functioning APU.

{ 8 comments… read them below or add one }

Shakinthefat October 9, 2008 at 11:30 am

Sounds like everything worked out fine. Planes are mechanical and do break sometimes just like a car.


Adam October 30, 2008 at 5:01 am

An APU has nothing to do with an airplane's ability to fly safely. It's just provides electrical power when engines are shut off. Some airliner's don't even have APU's. They're not needed, they're just convenient so you don't have to connect to a ground power source to run things like the AC when you're on the ground. Plus, jets can start engines without an APU once airborne.


Mike R. December 17, 2008 at 10:13 am

"Sounds like everything worked out fine. Planes are mechanical and do break sometimes just like a car."

No shit!!

Shakinthefat, you are one lame individual.

You provide absolutely no insights into anything.

Mike R.


A Man January 11, 2009 at 8:45 am

Although aircraft dont need an APU to operate on most AC it is part of back-up systems in the event of IDG (generator) failures on any of the engines to power essential electrical systems. It is also used in the event that an engine bleed system fails and can supply the aircraft with bleed air, which is not only used for cabin/flight station AC but also for aircraft pressurization and much needed anti-ice prevention. Also just so everyone realized on the newer jets there are back-ups to the APU electrical systems by means of a RAT to provide electrical and hydraulics to the aircraft systems.


Rob April 3, 2009 at 10:08 am

Salt Lake to Orange…and you mention sweat?

What kind of world do you live in?

Oh, wait.

Climate controlled house, climate controlled car, workplace, gym, doctors office.

You don't live in the desert, you live in the coal mine. God forbid the outside world should intrude on your sweat glands.

It's not personal. It's just that the more of these supposed problems I read, the more I realize that most people are just cattle, and if they lost electricity, they would be scavengers within a week. Dead within 2 weeks.

*queues a nice disaster movie* – a plane crashes, everyone dies in scene 32.


Joe Mama April 9, 2009 at 5:24 am

Rob: Forget to drink coffee this morning?

I don't think an 80 degree cabin was the main issue, though uncomfortable. The main problem in the story was the loss of APU & having to return to SLC.

Maybe you should start drinking decaf.


rolf April 22, 2009 at 1:58 pm

If that last generator had failed, they would have been flying back the plane on RAT power.


Tony June 12, 2010 at 5:54 am



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