Technical Talk

[Engine 711]

Now if we had that type of pump we'd be OK. Ours predates the HM governor and generates servo by basically centrifuging fuel through drillings in the pump rotor. It's therefore dependent on rotor speed rather tapping into delivery pressure. Seeing as the servo strokes the pump it's easy to see why we had to go light on all the settings to get the engine to start. we have a couple of Orph' 101s with the later pump and the one we have run and instrumented uses double the servo pressure and generates it instantly.

OK,so..... why not.... Change the Pump.....? Better to start the Orph you have - safely....?

[Renegadenemo]

Because it's the original one that pumped fuel on the 4th January 1967

[Engine 711]

Because it's the original one that pumped fuel on the 4th January 1967

Ah.....

[Renegadenemo]

The whole fuel system with the exception of the AFRC is original. The AFRC came from a crashed Gnat and was lying in the cellar at Shaftmoor Lane. K7's fuel system didn't have one. It had a primitive anti-surge control, one of only two ever made, and described in its own test report as a 'lash up'.

[Engine 711]

The whole fuel system with the exception of the AFRC is original. The AFRC came from a crashed Gnat and was lying in the cellar at Shaftmoor Lane. K7's fuel system didn't have one. It had a primitive anti-surge control, one of only two ever made, and described in its own test report as a 'lash up'.

Ah.... again. My knowledge of the Orf is almost zero.....

The Orff in K7 was - both times - a 700 series engine. The 2nd engine was 711 - so - there must have been 11 of them, at least.....? And 711 definitely came out of a scrap Gnat that DMC bought, for parts & spares.

[Engine 711]

Gnat XM691 was the first of 14 pre-production prototypes of what became the Gnat T.1, so it was far from a standard example of the type.

We could conclude that Engines 709 & 711 were effectively Flight Test engines - no more. Airworthy, but only just - lols.

[Renegadenemo]

We could conclude that Engines 709 & 711 were effectively Flight Test engines - no more. Airworthy, but only just - lols.

As I understand it, 711 flew but if the other one did it's either not recorded or i've not heard of it doing so. The fuel system dates back to 1959 and was a very early version. It was a real challenge to get it back to running order then mate it to a later 101 core engine such that it would all work - one of our most complex and proud restoration/conservation efforts backed by Rolls-Royce Plc even though they sought to distance themselves from it all post-Shoreham.

Sorry, R-R, we're still grateful for all your help and will continue to tell people that you made this possible.

[mtskull]

We had a failure with the hyd when the accumulator let go but we can run without that.

Are you sure? The purpose of a hydraulic accumulator, in addition to storing pressure, is to smooth out the pulses from the pump and protect the system from any "hammer blow" effect.

[Engine 711]

As I understand it, 711 flew but if the other one did it's either not recorded or i've not heard of it doing so. The fuel system dates back to 1959 and was a very early version. It was a real challenge to get it back to running order then mate it to a later 101 core engine such that it would all work - one of our most complex and proud restoration/conservation efforts backed by Rolls-Royce Plc even though they sought to distance themselves from it all post-Shoreham.

Sorry, R-R, we're still grateful for all your help and will continue to tell people that you made this possible.

The Shoreham Hunter crash....? https://en.wikipedia.org/wiki/2015_Shor ... show_crash

Not surprised - corporate liability & image and all that. RR (IMO) has always been at best a reluctant supporter of any speed record. The support for K7's Fuel System was from AEC - when they were part of RR, but still more... free wheeling. Less Treacle....

[conistoncollie]

Gnat XM691 was the first of 14 pre-production prototypes of what became the Gnat T.1, so it was far from a standard example of the type.

We could conclude that Engines 709 & 711 were effectively Flight Test engines - no more. Airworthy, but only just - lols.

A late friend of mine worked at BS in the sixties. He had this to say about XM691
It would be silly to say that I knew XM691 well, but it feels like it. It was used by Bristol Siddeley not only for flight test, but also a chase plane, for observation and for photography. The in-flight photograph of the Valiant, used briefly as Pegasus test bed, was probably taken from it.
In 1964 or thereabouts, in the course of my apprenticeship, I spent two weeks in the Flight Shed, and XM691 was there. It was much used and much liked.
Pegasus of course had its origins in the Orpheus, later powered the Harrier.