Re: Mr. Boeing, don't put quarters in the fuse box...

The damage described, particularly the large melted hole in the mounting panel, sounds very much like typical high impedance arc fault damage. (In this context, "high impedance" means not low enough to activate the overload protection devices.) The system probably lacks arc fault protection, and it will probably take more than one such incident before adding arc fault detection is seriously considered.

They will tell you to buy it from Boeing, as required by their contract. Boeing of course triples the price and only sells to authorized service centers.

Yes. And it appears that the root cause of this condition is that Boeing (or Sundstrand) chose to delete differential protection from the EPS. They did this back on the 777, which suffered a similar fault:

The AAIB (UK's NTSB) reccommended implementation of differential protection schemes on future aircraft. Which Boeing evidently chose not to do. Or more likely Sundstrand, since Boeing doesn't have much left to say about EPS architecture. And this is odd, because every previous Boeing aircraft I'm familiar with has just such a system.

Perhaps you. But not Airbus. Or the future Chinese manufacturer.

We spend millions of dollars and years with Sundstrand developing the

757/767 automated EGPS. Only to see Airbus buy essentially the same system for their new aircraft off the self. Unless there's something in there covered by a patent, there's no way for Boeing to stop Sundstrand from selling anything they want.

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Paul Hovnanian  paul@hovnanian.com
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Have gnu, will travel.

When I worked for an aircraft engine component manufacturer there was no way in hell we would sell components designed for one customer to another, and I doubt very much that the situation is any different with Sundstrand and the EGPS. The Boeing specifications are proprietary even if not patented, and if Airbus wants the same thing they need their own specification for it, and will be assigned their own part numbers, no matter how similar the specifications are. Designing a system which performs the same functions using the same components based on experience obtained with another customer is not the same as selling that customer's parts (or specifications) to their competitors; the former is legal and a standard practice throughout the industry, while the latter is not.

Boeing probably only owns the top level specifications, typically not including specifications for subcomponents like contactors - Sundstrand probably owns the detail, component spec and manufacturing process designs for the system, and switching vendors would mean a new design and qualification testing to the same top level specifications.

Industrial espionage also seems to be a common industry practice, but not one universally participated in by all suppliers. I know of three specific incidents where General Electric attempted to steal proprietary information from my former employer - without success. We protected all proprietary information diligently, and I believe most suppliers do the same, for their own protection.

[snip]

I've been in a few negotiations with Sundstrand (and other vendors). They are very good at 'managing' Boeing's expectations. And the end result is that we spec what they are prepared to build. Or they won't bid on it. And that was when Boeing had a shadow of an engineering staff left. Once Sundstrand has got sign-off on the spec, they just turn around and repeat the same process with Airbus. So its got an Airbus part number. Name plates are cheap.

As far as selling parts, Sundstrand has always maintained very tight control of their spares market. When we were building a mock-up of the

747-400 EGPS, ordering one set of generators above the contracted allocation of one ship set per airplane was like pulling teeth. They (Sundstrand) didn't want us ordering parts that could be diverted into the spares market.

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Paul Hovnanian  paul@hovnanian.com
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Have gnu, will travel.

Sounds like I should sell my Boeing stock and buy Sundstrand. I am surprised that Boeing let them have the lucrative spares business. GE would never let a supplier sell spares directly to the end user. Presumably Boeing negotiated a lower first cost in return for giving up the spares income. Sundstrand may have bid the original parts at little or no profit if they anticipated good spares sales, accounting for the reluctance to sell extra parts at the OEM rather than spares price. A former employer lost several bids to supply engine parts to Pratt and Whitney because they refused to bid anything at other than the standard profit margin while the competition bid on the ink-jet printer model, and lowest life cycle cost was irrelevant with P&W, only lowest first cost counted. GE at the time was more reasonable in that regard, so it was good to see them leave P&W in the dust with engine sales.

Re the thread title: I suppose one could compare the deletion of differential protection to putting quarters in the fuse holders.

Glen

Yes. IIRC, the 747-400 IDGs (integrated drive-generators) cost Boeing about $10K each for use on delivery aircraft. When we wanted a set (of 4) for our test rig, our purchasing people told us it would be at the spares price of something like $50K ea.

The IDGs were a very high maintenance item (incorporating a hydraulic constant speed drive). Many of our customers complained about their price. Boeing management could never catch a cude, since they were looking at the Boeing price, not the spares price.

That one is bizzare. We had two differential zones per channel. One from the generator through the GCB (generator control breaker, which ties gen to its load bus) and another from the GCB, through the main bus and through the BTB (bus tie breaker). The breakers were in an overlap zone, so an internal fault in the GCB (for example) would trigger both gen and bus protection.

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Paul Hovnanian  paul@hovnanian.com
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Have gnu, will travel.