Reply to post: Re: The investigation should center on...

Config file wipe blunder caused deadly Airbus A400M crash – claim

Anonymous Coward
Anonymous Coward

Re: The investigation should center on...

"As far back as WWII, aircraft were provided with the capability to go over 100% rated power if throttles were pushed past a retaining wire."

Just stop and think for a few moments here, sir. Maybe you've not noticed what's happened to aircraft engines since WW II.

Engines built in the WW II era relied largely on educated guesswork, both in design and in operation. No CAD, no simulations, barely a Materials Data Handbook, just slide rules, hard work, and a lot of engineering experience and intuition.

The engine controls back then, such as they were, were largely based on technology derived from clockwork and springs.

The result was that stuff was frequently massively overdesigned, or if it wasn't overdesigned, some unforeseen set of circumstances would take some critical parameter out of limits and Bad Things would happen. Sometimes Bad Things would happen quite often, after all there was a war on. Sometimes if the cause of a problem was obvious and easily fixed by a design change, there'd be a design change. Eventually.

The "war mode" facility allowed those tolerances to be exploited for a specific short term purpose.

And that was basically the way things carried on for a long time, albeit generally without a war mode button, with a few specific exceptions. Big tolerances, so things were safe. But big tolerances frequently implied extra costs.

The "full authority digital engine control" arriving in thr 1980s/1990s, combined with a whole load of other technology changes in the design and operational phases of aircraft engines (not to mention economic incentives for cost reduction and the usual stuff), allows those massive tolerances to be largely engineered out at design time.

When a modern engine manufacturer says "max rpm = 10k" (or whatever) they mean it. The historic mechanical and other tolerances in a modern aircraft engine have been largely engineered out to keep costs down and efficiency up, and the FADEC is relied upon to ensure the engine only operates in a "safe zone" where things like uncontained failures are almost infinitely improbable.

As part of the new improved approach the effects of going over 10k rpm will have been simulated, analysed, and maybe even costed. There won't be a safe way of going over 10k rpm. If there was, the manufacturers would have uprated the engine and said "max rpm = 11k" (or whatever).

If the manufacturer does want to permit "war mode" its use may well still equate to engine writeoff. But the tolerances that enabled things like "war mode" to be generally worthwhile and effective have largely been engineered out.

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