Tuesday, September 26, 2006

Engines? We Don't Need No Steeenking Engines!

WARNING: No philosophical issues here, just a bit of deep background with a strong likelihood of inducing excruciating, perhaps permanent, boredom.

To a pilot, this para led immediately to a "What The ..." moment:

A BRITISH AIRWAYS jumbo jet carrying 351 passengers was forced to make an emergency landing after an 11-hour transatlantic flight with a failed engine.


"Emergency landing" just doesn't play well with rest of the sentence, especially that 11-hour part. So for those of you at home in the pixel audience keeping score, here is some deep background on how you get to an emergency landing an entire continent and ocean away from its instigation.

Just to stir the stew, the story also includes this little info-nugget demonstrating the EU has found yet another way to be incredibly meddlesome, apparently without even the tiniest tingly nanny-sense that there might just be some unintended consequnces:

The incident happened three days after a European regulation came into force requiring airlines to compensate passengers for long delays or cancellations. Under the new rules, if the pilot had returned to Los Angeles, BA would have been facing a compensation bill of more than £100,000.


The EU, in forging towards the brave new world where government ensures citizens are never exposed to any risk, has provided powerful incentive to continue a flight that might otherwise turn back. After all, it is very easy to quantify a 100% chance of losing £130,000 (including fuel dumped to get under max landing weight), but very difficult to balance that against the much smaller likelihood of losing vastly more money in deciding to continue the flight despite losing an engine.

There are really three factors bearing on the question: Safety, cost, and regulatory requirements. In general, safety is covered by the Federal Aviation Regulations (FARs), under the assumption that if you are complying with the rules, you can't be screwing things up too badly, unless you engaged in a brand new way to auger in.

With regard to engine failure, the FARs require that the pilot in command land at the nearest suitable airport following an engine failure.

Except for four engine aircraft, where the Captain may continue to a more distant airport, provided that, in the Captain's judgment, proceeding to that airport is as safe as landing at the nearest suitable.

Somehow, I doubt the rule writers had subsequent transatlantic crossings in mind. The FAA attempted enforcement action based upon some ex post facto decision as to what the rule meant, as opposed to what it clearly said, but pretty quickly gave it up.

Despite appearances, accompanied by a certain amount of press hysteria, was the Captain's decision, albeit legal, sound? (NB -- the Captain's authority is absolute, and there is no possibility BA could have penalized him in any way should he have decided to return to LAX.)

By sound, I consider whether proceeding with three engines would have exposed the aircraft to any greater hazard than four.

Oddly enough, the answer is "No." A B-747 has sufficient performance to fly until fuel exhaustion on two engines, and probably even with one, although at a much lower altitude. With three available, the only additional risk is that of diverting to a field short of the destination due to higher fuel consumption resulting from flying roughly 7,000 feet lower en route. It is further worth noting that there has never been a case of multiple, coincident, engine failure on engines equipped with digital engine controls.

At an intellectual level, it is impossible to find fault; however, I'll bet there are few Captain's who would have decided to press on. (I was on a 747 bound for London out of LAX that suffered a compressor stall about 10 minutes after takeoff; thirty minutes later we were back in the departure lounge.)

But still ...

As for the EU, it is difficult to summon enough scorn without entirely depleting my considerable derision reserves.

5 Comments:

Blogger Duck said...

Skipper,
Does the FAA or their English equivalent make the determination of what an "emergency" landing is? Is this an official condition or is this just verbiage added by the press?

The problem with the EU regulation is that even if airlines don't take the lost revenue into consideration when making decisions like the one you cited, there will always be the opportunity for the press or the public to second guess their decisions.

September 27, 2006 7:57 AM  
Blogger Hey Skipper said...

David:

If a pilot declares an emergency, the landing is an emergency landing, no matter how normal it may be. The press's use of the term, while technically correct, often serves to add drama where none exists. (The Jet Blue nose gear failure landing being a classic example -- hours of hype leading up to what any true expert could have told you would be an otherwise normal landing with some interesting visuals.)

The point of declaring an emergency is to absolute priority, where required, to the declaring aircraft.

You are correct about the immediate problem with EU regulation, because the certain outcome is some degree of public opinion based solely upon the regulation's perceived impact upon the decsion.

But what is worse, IMHO, is the EU's drive to eliminate the foreseeable consequences of people's actions. Air travel is not a certain thing; presuming BA maintains its aircraft in accordance to BAA regulations, then mechanical failures are simply an impossible to prevent part of flying (ignoring for the moment that BA could have been in the position of paying for an act of nature -- a pelican down the throat of number four).

September 27, 2006 8:52 AM  
Blogger Oroborous said...

I didn't find that to be boring.
Quite the opposite.

September 27, 2006 1:24 PM  
Blogger Harry Eagar said...

I didn't know about digital controls. I can recall coincident failures of several (including all) engines in the predigital era.

In one, which I remember vaguely, a transpacific airliner dropped something like 20,000 feet before the engines restarted. So, flying lower is not, to my mind, a wholly negligible element in overall flight safety.

Even without EU regs, I also recall that Alaska Airlines kept flying past several airports after experiencing some control problems, eventually crashing in the ocean.

My brother told me that the worm screw that actuated the tailplane was so worn that its only connection with the lever was hardened grease.

September 27, 2006 1:29 PM  
Blogger Hey Skipper said...

Harry:

In one, which I remember vaguely, a transpacific airliner dropped something like 20,000 feet before the engines restarted. So, flying lower is not, to my mind, a wholly negligible element in overall flight safety.

That did happen (about ten years ago, I think) to a BA 747 that had a night time encounter with a volcanic ash cloud from an eruption that occurred after departure and had not yet been passed to the crew. Their is much more emphasis put on ash cloud tracking now.

There are two problems with flying lower: that is where most of the weather is, and the consequent decrease in True Airspeed leads to significant increases in fuel consumption.

Even without EU regs, I also recall that Alaska Airlines kept flying past several airports after experiencing some control problems, eventually crashing in the ocean.

Yes, they did. However, to my knowledge they were on the radio with their maintenance people in an attempt to analyze the problem. It may well have been that any significant trim change, or change in aerodynamic loading on the horizontal stabilizer, inevitable with the transition from high altitude cruise to landing configuration/speed would have ripped out the jack screw (your brother is not far from the mark); perhaps we should be thankful the inevitable happened over the water.

I didn't know about digital controls. I can recall coincident failures of several (including all) engines in the predigital era.

Turbines are already amazingly reliable; the addition of Full Authority Digital Engine Controls (FADECs) has eliminated engine exceedences, and removed the fuel control system as a source of failure.

FADECs have provided so much reliability, as well as contributing to power increases, that most airliners built since the early 90s have had two engines. Pre-FADEC reliability led to considerable route restrictions for two-engine aircraft: no further than (IIRC) 45 minutes from the nearest suitable airport on one engine -- over water routes were too convoluted to be economical, hence three engine aircraft like DC-10/L-1011.

Demonstrated FADEC equipped reliability has been so outstanding that two engine aircraft are no longer at such a disadvantage.

My wife says of me "Ask him the time, he'll build you a watch."

September 27, 2006 6:25 PM  

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