Column: Concorde's design, engineering made for safe aircraft

"Aviation is proof that given the will, we have the capacity to achieve the impossible." - Eddie Richenbacker.

My column today is dedicated to those visionary aerospace engineers who created one of the most phenomenal aircraft in the history of aviation, the Concorde.

She is really a pioneer when you consider the extensive use of advanced materials, like welded titanium honeycomb stiffeners, titanium structural components, and titanium skin which were all proven on this aircraft.

Aerodynamically the Concorde isn't special, being a hybrid of a number of sub and supersonic aircraft designs, and the basic delta configuration has long been a favorite of the British Royal Air Force with their Vulcan bombers. But the combination of the design, coupled with state-of-the-art components and materials, culminated in a master piece of reliability.

Just think, 30 years of zero accident performances. And only a smattering of minor failures which not only never injured anybody, but hardly had an effect on operational schedules, until that fateful day July 25 when on takeoff the No. 2 engine exploded on the port side causing the No. 1 engine to fail as well. With two engines out on the same side, the sleek lady didn't have a chance.

What all this is leading up to is that Concorde is a perfectly safe airplane. Its design and materials have been as thoroughly proven as any aircraft flying today. Concorde's Rolls-Royce engines also have a perfect 30-year record. There can be no question of the integrity of those engines. So that leaves only two possible areas to consider and those are (1) maintenance, or (2) something external to the aircraft which fatally damaged it. Although maintenance can always be improved, I personally suspect something which happened against very high odds.

The most critical moment for any aircraft in takeoff mode is the instant of rotation. That is the moment of truth. And if you lose only one engine out of four at full gross weight, you can still safely climb, circle and land. However, two engines failing out of four at full gross weight, and on the same side, the ball game is over.

I think when all is said and done, we'll find that the No. 2 engine, which exploded, ingested runway debris or rubber from an exploded tire. Investigators so far have said they believe a piece of metal on the runway caused one of the tires to shred, crippling the engine or causing a fire in a fuel tank.

If there is any design fault in Concorde, and this is a matter of conjecture, it's possible that the British propensity for nesting their engines side-by-side within the wings of their aircraft expose the engine adjacent to the exploding one to shrapnel, which can cripple it as well.

For passenger aircraft, American airframe companies use external engine pods, keeping the pods well separated and staggered so as to eliminate the possibility of an exploding engine harming the one next to it. But this is less efficient and structurally dangerous in the case of severe yaw due to an outboard engine failure at supersonic speeds. Remember the Convair B-58? Instant disintegration!

Now, concerning skin cracks which have been observed on some Concordes, these are not structurally critical and can be readily repaired. However, what we've learned from this is that 30 years is about the limit for this type of skin.

Repairing cracks cannot go on indefinitely. And the cost of replacing wing spars and/or skin may be prohibitive, not to mention the vertical fin which takes a real beating. Today's Concordes may possibly be headed for the bone yard.

Should you think this skin cracking business is a phenomenon limited to Concordes, nothing is further from the truth. All metal aircraft structures - steel, aluminum, titanium, or whatever, which are subject to loads (people), vibrations (engines), flexure (loads and turbulence), and corrosion - will ultimately fail. It's up to our aerospace structural engineers and metallurgists to predetermine a possible time of failure and make certain that critical "fatigued" structures are replaced beforehand.

I wish I had a hundred dollar bill for every airliner in the world that's flying around with at least one cracked wing spar out of the three. Those repairs are routine.

I'm not trying to frighten you folks who fly, but you must remember that engineering is always pushing the state-of-the-art envelope to its limits. Therefore, we engineers will never know for certain how long any type of aircraft can fly before it will absolutely fail structurally. Computer programs aren't that good because no two flights are ever the same in terms of stress. All in all, I think the industry has done a superb job of predicting possible failures and keeping them contained with a minimum of life loss.

Again, I salute Concorde. Her British and French team represent the very best of aircraft engineering, any time, any place.

Bob Thomas is a Carson City businessman, local curmudgeon and former member of the Carson City School Board and Nevada State Assembly.

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