Latest XH558 Newsletter

[Jigsaw]

Whilst I am gutted she won't be at Waddington, I am pleased the damage was contained and the airframe is intact.
I wish all at VTTS, particularly the engineering staff the very best in getting her airborne again.
Obviously, there will have to be air tests once the new engines are fitted. I shall console myself with regular visits to Robin Hood

[RLN]

I was waiting for Sooty to post on this. Thanks, Eric. We have blow-off valves to prevent surge. Do jet engines have these - obviously modern engines, not '50s designs?

[Sooty655]

I was waiting for Sooty to post on this. Thanks, Eric. We have blow-off valves to prevent surge. Do jet engines have these - obviously modern engines, not '50s designs?

It varies from engine to engine. Generally, the more shafts, the less is needed in the way of blow-off valves or variable stages. With two shafts (or three on a modern turbo-fan) the ratio of each individual compressor is less, and they can self-match the airflow by speed differences. A big single shaft obviously has all compressor stages turning at the same speed, and needs blow-off valves and/or variable stages to eliminate the tendency to surge/stall at other than design speed.

The Olympus and RB211 have no need for blow-off valves, whereas the biggest of the Avon family (single shaft) has separately activated blow-off valves at two compressor stages ( from memory, stage 4 and stage 7) plus a set of variable inlet guide vanes.

I think the GE CF6 (which has the fan and IP compressor on the same shaft) uses multiple stages of variable stators for airflow matching.

The exception to all this was the Armstrong Siddeley Sapphire, which had a large single shaft compressor with no blow-off valves or variable stages, but which was generally considered impossible to stall. The reason was that each individual compressor stage was horribly inefficient.

[RLN]

Thanks for that, Sooty. It seems that (in civilian turbofans) the Americans tend to have higher HP compressors and so need variable stator blading, whereas Rolls Royce with the Trent family have quite low pressure HP compressors and so don't have variable stators except for 1 row on the IP compressor.

[Sooty655]

Some of the difference comes from the basic structure of a two-shaft turbofan, which means that the design speed of the IP(LP) compressor is limited by the fan speed. This generally means the designer chooses to have more of the work done by the HP compressor. With a three-shaft arrangement, more work can be done by the IP compressor because it can be designed for a higher speed, so the compression ratio over the HP compressor can be reduced for the same overall compression ratio.

Recent work on a geared fan system (by P&W, I think) are aimed at reducing this limitation of the two-shaft layout.

[RLN]

Great stuff, thanks.

[Sploosher]

Sad to see the 558 wont be going to Waddington................

I have not yet decided if I am going to the show, but will be attending one of the arrivals days

[MOD]

I shall console myself with regular visits to Robin Hood

Smug ...











































Git (mk2)


Ian

[Jigsaw]

[Mayfly]

Not a lot of consolation but had 558 been serviceable she wouldn't have flown yesterday any way.

The total for the appeal is showing as £280,359 so less than £20K short of the overall aim - not a bad effort by all concerned.

[Minty4371]

Today's update.

DEADLINE 31st MAY
APPEAL TOTAL:
£310,136

MAY TARGET
£90,000
TO DATE: £100,136

[Jigsaw]

Bravo

Edit: Replacement engines on site. Applause to Turners of Soham and good luck in completing the work to the engineers

http://www.vulcantothesky.org/news/361/ ... tures.html

[Jigsaw]

Latest Newsbytes

“A week of hectic activity in the hangar has paid off as we are comfortably on schedule. Yesterday we passed a major milestone as the replacement no.1 engine went ‘on wing’ and today, no.2 is scheduled to be lifted into the airframe. Next week, the new engines will be connected to the aircraft systems: the fuel supply, jet pipes, alternators, hydraulic pumps, engine instrumentation and other ancillaries will be refitted.. In parallel with this, we are working closely with Rolls-Royce to complete the approvals necessary to have XH558 released for test flights at the beginning of July.

One of the engines has just 64 hours logged since it was originally fitted to XH558 in 2007, making it virtually new. The other one is a pristine zero-hour engine: it’s basically a brand new Olympus that hasn’t run since the Rolls-Royce quality inspector signed the green ”Serviceable” label on the anti-icing pipe more than 30 years ago.

These are very high precision pieces of engineering, so caring for them over this time is a tightly-managed operation. The bags you have seen in previous weeks’ photographs provide a hermetically sealed environment that helps protect them. Every month, we’ve opened the bags and replaced the chemicals that absorb moisture. We have also rotated the shafts and replaced the special inhibiting oil that helps to protect the fuel system and its seals. In just over a week, we’re aiming to bring them both back to life!”

See the latest pictures and a video here:
www.vulcantothesky.org/news/363/82/Late ... tures.html

[Crew chief]

Lets hope they don't make the same mistake again.

cc

[Jigsaw]

"With the two replacement engines now installed in their engine bays on the aircraft, attention is focused on the complex, time-consuming but vital job of carefully reconnecting them back in to the various aircraft systems: fuel, electrics, hydraulics, cooling air, engine bleed air, and of course engine instrumentation: rpm, oil pressures and so on.

To try to make as swift progress as possible, whilst ensuring everything is done properly, we have engaged some extra temporary technical assistance, including a propulsion trade technician from Marshall Aerospace.

Assuming everything goes to plan, we hope to be thinking about engine ground runs in a few days' time. More news on Friday!"

[Sploosher]

Assuming everything goes to plan, we hope to be thinking about engine ground runs in a few days' time. More news on Friday!"

does that mean there may be a slim chance of 558 being at Waddington then.............

if so, I may have to change my plans for that weekend........

[Mayfly]

I think it would be a slim chance, I've seen air tests mentioned somewhere and I dare say a couple of practice displays will be needed - and take into account the weather and............

take into account Waddington may way have replaced her you can't expect them to leave the slot open just in case.

[Sploosher]

A slim chance is better than no chance...............

[Dee]

Its allsounding very positive though now eh?! Great team we have banging the engines in etc!

[Kermit]

All very positive, and an engineering team working its socks off to get her back in the air, methinks both we and 558 are very lucky indeed to have such dedicated engineers......
fingers crossed, cant wait to hear those Olympus engines roaring over Finningley again, with a few howls thrown in for good measure !

[Mayfly]

All very positive, and an engineering team working its socks off to get her back in the air, methinks both we and 558 are very lucky indeed to have such dedicated engineers......
fingers crossed, cant wait to hear those Olympus engines roaring over Finningley again, with a few howls thrown in for good measure !

Goes with the territory - there is a lot of trust between air crew and engineers.

[Dee]

Cant wait to get up on the lane soon and hear those engines!

[Jigsaw]

Cant wait to get up on the lane soon and hear those engines!

I keep checking for updates as well. Will be straight to finningly when news of a flight is announced.

[MOD]

I keep checking for updates as well. Will be straight to finningly when news of a flight is announced.

You and 10,000 others Kev which is why, imho, it won't be made public until after it has happened. Of course DSA/Robin Hood Airport will be in the know and it may well be announced on Facebook again - much to Mr Homer's annoyance.

I'll just breath a sigh of relief when it happens... AAIB/CAA/HSE willing of course..

[Jigsaw]

I know what you mean Ian although last time it was absolutely packed but caused no problems I could see. Even the Police came, stopped, got out, and watched

Whatever happens whether announced or not like you I will be pleased to see XH558 serviceable