Mike Bull wrote:But do we know which of those engines the fuel system first came off of..?
Renegadenemo wrote:I'd have thought the gnat would have its fuel system on it and the spare engine would be just a core. Any other assumption has to have the gnat delivered with important parts missing that were somehow left on a scrap engine.
A complete engine would normally come with its fuel system, although the main parts of the fuel system, e.g. pump, CCU, are all considered to be Line Replaceable Units. This means that they should be fully interchangeable on a deployed aircraft, albeit there may be some limited in-field adjustment required, such as ground idle settings.
When an engine is removed, cannibalising the fuel system to get spare parts is not normally the done thing, as this would render it impossible to inhibit the remaining fuel system parts. However, it is well within the bounds of possibility for a flight test engine that the complete system would be removed to be used elsewhere, or returned for evaluation. If it is all flight test stuff, then there are doubtless reports in our archives which reference most of the fuel system hardware, but it could take a VERY long time to find them.
We know that the fuel system which came off the lake bed contained at least one part which was for development flight test only (the ASC), and therefore would not have come from a production engine / aircraft - but I'm not sure if that helps you any. Most flight test aircraft in those days ended up having multiple changes of parts on the fuel system as the envelope was explored and the fuel system calibration was developed. Subsequently almost anything from the flight test inventory or production standard hardware could be fitted if an item was removed as unserviceable, so the concept of the "original" fuel system for an engine from this source is pretty meaningless.
All of this is very interesting, but I think we alreday have the most important piece of information here, which is that the fuel system parts which were on the engine at the time of Donald's last record attemt are the ones which were found at the bottom of the lake.
By the way, I'm sure that a few H&S types could spend hours discussing the workshop photo with the two engines and the man on the ladder as a case study...