XM655

[Mayfly]

Well done all - fingers X'd

[Crew chief]

i know it's early days, but what's the engine looking like in respect of keeping RR happy?

sm

Hi sm.

The issue is not keeping RR happy its the local authority and the HSE we have to comply with.

cc.

[Saracenman]

ah - yes - thank you for correcting me! FunPolice.gov.uk

sm

[Crew chief]

ah - yes - thank you for correcting me! FunPolice.gov.uk

sm

Sorry sm but facts are facts.

cc.

[Bovril]

i did forget to say externally .. as for xray vision.. maybe have some specs in my toolbox

but so far she looking in excellent condition

Has the intake of copious amounts of thick, salty meat extract given you x-ray vision Mr Bovril??

[Sooty655]

After removing the hollow locating dowels and the last few bolts, we lifted the LP compressor top half casing this morning. The compressor was found to be very dirty, but in excellent condition. The rest of the day was spent cleaning and inspecting in detail, and we have found nothing which causes us any concern.

An inspection of the zero stage stators has shown that we need to change three cracked blades, and luckily they are all in the top half, which means that the access is fairly easy.

We have also removed some of the bolting on the HP compressor casing, but we will complete the LP work and refit its casing before we open the HP.

I will add some pictures tomorrow - not enough bandwidth at present.

[Mayfly]

Brilliant news - am I right in thinking the stators just slide in a grooved slot [so to speak]

[Sooty655]

Brilliant news - am I right in thinking the stators just slide in a grooved slot [so to speak]

The stators are indeed mounted in a grooved slot, much like a dovetail joint in woodwork. However, the words "just slide" don't do justice to how tight they are. I have made up a puller to get them out of the seized engine we got from Woodford (our source of spare blades), but I plan to improve it before we tackle the stators in No 4.

[Mayfly]

yeah I know - just a figure of speech!

[Sooty655]

As promised, here are a few pictures of our activities yesterday, all taken by Charles Brimson.

After we removed the remaining fixings, it didn't take long to position the engine under the gantry and start lifting the casing.


Needless to say, as it went up we were anxious to see what condition it was in.


This is the port side view after a good cleaning....


...and the starboard view.


Looks pretty good from the front too.


This is the top half casing. We need to change three of the zero stage stators (the top row).


More busy days ahead, but so far, everything is positive.

[Sploosher]

Its all looking good from mhere, you guys do a cracking job looking after you lady.............


I really must get down and see her some time

[Mayfly]

That engine really is looking very good isn't it!

I take it you have a stock spares for the stators? So what is their job then Sooty.

[Sooty655]

Yeah, we are very pleased with the condition, although to start with it was very dirty. Probably caused by the very dusty arrival of the army helos at W&W a few years ago, when DT already had 655's engines running.

We are using the seized engine we got from Woodford as a source of spares.

One set of rotor blades followed by one set of stator blades (sometimes called vanes) form each stage of the compressor. The rotor blades impart velocity to the incoming air, and also cause it to swirl. The stator blades reduce the velocity again, increasing the pressure, and remove (some) of the swirl ready for the next set of rotor blades to repeat the process. An Olympus 301 has six of these stages in the LP compressor and a further seven in the HP compressor.

Caveat - that is the simple description. For readers who want a more technical description, there are plenty of good books available.

[Bovril]

i was going to say dont they make 655 roar whereas 201's squeal?

[Sooty655]

i was going to say dont they make 655 roar whereas 201's squeal?

The term usually used is "Howl", I don't think 558's many supporters will be pleased to hear it described as a squeal.

Afaik, the howl comes from a resonance in the air intake in front of the 200 series engines. With 301s, the intake is shorter, and the resonance doesn't seem to happen, so all you can hear is the roar.

[Hungry Haggis]

i was going to say dont they make 655 roar whereas 201's squeal?

MAYFLYsend miss whiplash round to Bovril he need's a bit of corection


At last The inside of a jet engine .i did chalenge someone some time back You win.How far are you going to dig in there

[Pujgnie]

Great piccies

That engine looks in great condition (say he NOT knowing anything of Olympus engines ) Also looks a tad heavy.

Numpty Q comming up............. Are those fan blades individually replaceable, or is it the whole gubbins ?

[Sooty655]

Are those fan blades individually replaceable, or is it the whole gubbins ?

None of the blades can be replaced individually, i.e. without removing others.

The stator blades can be removed one at a time from the end of the row until you reach the one you want to change, then the remainder can be put back. This is not too difficult in the top half, difficult but possible for the bigger stages in the bottom half, and impossible for the smaller stages in the bottom half. In that case, you would have to turn the engine over and remove the bottom half casing from what has become the top, if you see what I mean.

Having said that, normal practice would be to replace a complete stage. We are only replacing individual blades because the fault is very specific (fatigue cracking which is a well known 301 problem) and we don't have enough spares to consider replacing the lot.

To replace rotor blades, the whole compressor rotor has to be removed and dismantled into its separate stages, and then rebalanced after re-assembly. That need a lot of specialist equipment - not something we would want to tackle.

[Bovril]

you know me only teasing

i was going to say dont they make 655 roar whereas 201's squeal?

The term usually used is "Howl", I don't think 558's many supporters will be pleased to hear it described as a squeal.

Afaik, the howl comes from a resonance in the air intake in front of the 200 series engines. With 301s, the intake is shorter, and the resonance doesn't seem to happen, so all you can hear is the roar.

[Pujgnie]

Ta Sooty

Do the 200 and 300 series engines have the same amount of blades ? and how many are there in total ?

[Sooty655]

At last The inside of a jet engine .i did chalenge someone some time back You win.How far are you going to dig in there

When we have put the LP compressor back together, we will take the HP top half casing off to inspect that section as well.

As regards the inside of a jet engine, we plan to open up all the possible sections of the seized engine we got from Woodford and turn it into a display item to use at Wellesbourne and at our W&W events. However, as it isn't directly related to keeping 655 serviceable, it isn't going to be finished any time soon.

[Dan4th]

Do you guys plan on doing any
(ahem...) Animal Testing??

D.

[Sooty655]

Do you guys plan on doing any
(ahem...) Animal Testing??

D.

I sometimes struggle to follow Murkin humo(u)r, but if you are suggesting chicken mincing, then the answer is NO WAY. We only have to confirm the engines are still fit to run, not validate the original design.

Do the 200 and 300 series engines have the same amount of blades ? and how many are there in total ?

300 series engines have an extra stage (the so-called zero stage) on the front of the LP compressor, so they have roughly 40 more rotor blades and 60 more stator blades than a 200 series. This produces the extra air flow and compression which results in the extra thrust.

I have no idea how many blades are used in total. I will try to find out, but don't hold your breath.

[Dougs]

hi sooty,
do you inspect the 'hot end' to check the TBC on the blades, vanes and the combuster wall?

[WaddoVet]

I have no idea how many blades are used in total. I will try to find out, but don't hold your breath.

You told me it was 7 1/2 buckets-full!