A Tale of Mid-Air Dual Engine Failure

You can call me unlucky having been a passenger on an airliner that lost power in all of its engines in flight, and on yet another that lost two of its four engines, or you could call me lucky that I’m still around to tell you the tales.

The first event happened early in my career as a flight test engineer for a large aircraft manufacturer.

As part of certifying a new clean sheet, twin-engine airliner model before it would be allowed to carry the flying public, we were airborne exploring the engine restart envelope – that is, the various altitudes and airspeeds that a dead engine could be restarted using only the power of the wind to get it turning fast enough to successfully ignite.

I’m not going to lie – it was a little boring. It required the pilot to simply shut down one of the two engines in flight, let it cool for several minutes, and then demonstrate that it could be restarted at a range of different altitudes and airspeeds. It used what was called a “windmill start”, which literally relied on the speed of the wind to spin the engine blades fast enough to restart it when the pilot added fuel and spark.

We undertook hours of shutting down one engine, letting it cool sufficiently, restarting it, and then shutting down the other engine to repeat the process. Then, setting up for the next test point we again shut down one engine and after it cooled sufficiently I told the pilot it was time for him to relight it...

Call it fatigue, a distraction, or whatever you’d like, but the pilot did the unexpected and unthinkable. Instead of restarting the dead, windmilling engine, he reached over and shut down our only perfectly good remaining engine.

In an instant we became a 250,000lbs glider, drifting downwards precariously over the mountains.

The next minutes in the cockpit were tense but deliberate. The Auxiliary Power Unit (APU) was started to provide electricity and hydraulic power since there were no engines which would normally provide these. The plane was then pointed away from the mountains towards lower terrain.

The engine we inadvertently shut off wouldn’t be able to start in time since it would take upwards of 10 minutes to cool to a point where it would have a chance of lighting up which was much longer than our available glide time.

We had no idea if the other engine – which by now had presumably cooled sufficiently – would start since it had never been tested at this airspeed and altitude combination before.

Tense Wait in a 250,000 Pound Glider...

Once we were stabilized and had done everything to prepare for the worst, the moment of truth arrived. The pilot reached over to the fuel cut-off of the cooled engine and flipped it back on. There was a tense, awkward silence as all eyes looked to the engine gauges to see if the dead engine would roar back to life.

The worst-case scenario would have been to see the internal engine temperature soar to an exceedingly high level, known as a ‘hung start’, in which case it would again have to be shut off and allowed to cool for an extended period.

Mercifully, we observed the engine RPM slowly increasing as it started with temperatures remaining within safe levels. We had, once again, become a single-engine airliner. After the second engine was later successfully restarted, we made the executive decision to call it a day and finish another time...

A Tale for Another Time

Perhaps, if someday we meet in a poolside bar, I’ll tell you about the time I was aboard Concorde and we lost two of the four engines. Here, a computer failed allowing a shock wave to travel through and extinguish one engine, which unceremoniously “burped”, sending a disturbance through the inlet of its neighboring engine snuffing it out, too.

All of this caused a loud, audible bang followed by a rapid descent towards the ocean to get to an altitude where the engines were successfully restarted.

It’s been said that things happen in threes. As for two separate double-engine flameouts on an airliner, I truly hope there’s an exception to the rule...!

Read more articles by Brian Foley on AvBuyer

MI www.brifo.com