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Thread: Rear starboard exhaust tube broken........ Again

  1. #1

    Rear starboard exhaust tube broken........ Again

    I have heard and know that the exhaust tubes "break" every 200hours ish.... Don't tell me that it is not a problem as 200 hrs is about 4 years for a standard pilot. Or a 1 per hour......

    Surely something can be done about this design.......flaw??

  2. #2

    Rear starboard exhaust tube broken........ Again

    Exhausts are consumables on all aeroplanes, so don't expect them to last forever. mild steel ones rot after five years or so, and stainless ones are more prone to cracking that needs constant small repairs. There isn't a golden solution out there and especially on weight critical aeroplanes like ours where the exhaust is a big lump of weight and can't be as thick and bullet proof as might be optimum for long life. Quite different to a car where exhausts are normally double the thickness - and of course they don't last forever either..

    The Eurostar system uses flexi hose in the downpipes to relive stress on the downpipes and box, however over time the movement wears out and eventually fatigues the flexi portion.

    this can be delayed by adjusting the fit so the flexi section does have any parts that are coil bound because of too tight a radius. Some fiddling with angles and depth of insertion into the can helps to get the best fit.

    Also Evecktor have altered some of the lengths and angles the last couple of years to improve it in this regard. our School Eurostars used to eat a downpipes everY few hundred hours, but seem to be lasting a bit better now - or maybe it's just the poor summer reducing our hours and extending the time between replacements...!

    Carb and prop balance makes a huge influence on exhaust fatigue and life, so well worth keeping on top of those items regularly. any excessive shaking also reduces their life considerably - so another goo d reason to really be concerned and develop that mechanical sympathy and find the best routine for smooth starts and shut downs on your particular machine.

    Paul

  3. #3

    Rear starboard exhaust tube broken........ Again

    Paul

    Many thanks.

    Over the last 4 years there were a spate of exhaust failures on the eurostars at my field and I helped change a lot of them. Yes I agree there were some design changes, but i feel gutted that my exhaust has gone again.

    The rear starboard (same part as the rear port I think) is the one that split. That looks like a pretty straight run with very little curvature.

    Just wondering, I know the eurostars are near its weight limit, looking at the, say the Nynja or gt450 exhaust where they have sprung connectors, do they crack as often?

    I have seen exhaust tape, which not used a bandage because it has a hole in the pipe but for transmitting heat performance. Could this be used to aid the longevity of the flexi portion of the exhaust and cope with the vibrational elements.

    I agree with balancing the carb which may have caused additional stresses, i balanced the carbs at the 1000 hr service and was running smoothe , shame the exhaust flex broke 36hrs later....

  4. #4

    Rear starboard exhaust tube broken........ Again

    Originally we used the rotax supplied exhaust componets and welded up the Skyranger systems. 80hp 912and the mild steel rotax bits no problem. Except that after about 4 years or 400 hours or so they seemed to succumb to rot and the tailpipe would fall off after the inetrnal supporting baffle rotted through and allowed it to waggle and faituge crack. Bit of a nuisnace as there was no sensible repair and a new can was needed, could also scorch teh cowlings which was a bit of a worry.. We also had the odd mild steel downpipe seemingly go soft and screw itself up and flatten- very strange!

    They (Rotax) then changed to stainless as standrd component supply, which was better for the downpipes, and no rot but we had a statistically significant number of cracking problems around the cups on the can and around tailpipes again. We added supporting straps to tailpipe - sometimes that worked fine, other times little difference. 100hp 912S eats them rather quicker than the 80 horse.

    We then changed to using a CKT system that was originally deveoped for the Europa. Around 1.5kg heavier (and 50% more expensive), but looked better made and I didnt have to weld up the components. Fine on the 80 horse for a while, but then we had a spate of tailpipes falling off (again!!!), Steady bracket added, but then that would crack, Mk2 steady bracket finally chased that problem away. Occasional issues with cracking around the cups, and the odd downpipe head interface collar cracking round and falling off, but most reliable system yet. 912S gives it a bit of stick and it would move positon unbidded with danger of melting stuff that it came in conatct with, so SB issued for a steady bracket/ brace (been through three designs of that to stop it breaking!).

    Nynja exhaust a new design again - but from CKT - fingers crossed no major problems yet.

    Pand M exhaust have had their issues and lots of design changes. A 912S with sprag clutch problems has been known to dismantle the earlier systems on start!

    Two stroke exhausts rarely make 500 hours without gaining a few weld repairs or a complete replacement.

    went to do a GST the other day on a 582 blade (300hours ish) and we couldnt fly because exhaust manifold had cracked nearly all the way around - and it wasnt its first repair

    Exhaust are always tricky buggers - hence my comment as regarding them as consumables, and you must always view them with suspicion on your preflight!

    The annoying thing is, some aircraft can last three or four times longer before cracks or propbelms than another apparently identical machine - presumably due to subtle diferences in use of vibration patterns / carb and or prop balance etc etc. Headache for manufacturrers as problems often dont show up for 3-500 hours plus - and you will never get to market if you put that many hours on your new machine before selling them. and of course the production ones will alway do far worse than your test machine by sods law!

    things have got a lot better relaibilty wise over the years (time was when you needed to be a welder or have a good mate who was a welder, to be a microlighter!)- but mainly as individual manufacturers learn as the go along, and refine the systems they have in response to problems thrown up after hundreds of hours of use across the fleet.

    Paul

  5. #5

    Rear starboard exhaust tube broken........ Again

    Paul

    Many thanks for clarifying the state of play. I know a good welder :-) and now have a spare in case of emergency..

    New exhaust now fitted. It was interesting that on the Cosmik website they were out of stock........... But I was lucky to get one.

    Regards

    Wayne

  6. #6
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    Rear starboard exhaust tube broken........ Again

    I know that a lot of Eurostar owners have had this issue, but with 700 hours on the clock, not a single exhaust issue. I can't think why that would be, there's nothing special about the engine / exhaust installation on my Eurostar.

  7. #7
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    Rear starboard exhaust tube broken........ Again

    Do they all have soft start,ive seen pilots start from cold without keeping the engine at a sensible stable revs shaking itself silly,not saying rev the nutts off them but 2500steady till they warm up must cut down vibration that is the cause of cracks.

  8. #8

    Rear starboard exhaust tube broken........ Again

    They all have the 80- horse 912 Dave - which doesnt have (or need) the soft start module.

    Paul

  9. #9
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    Rear starboard exhaust tube broken........ Again

    Paul Dewhurst wrote: ...[after] 400 hours or so ...the tailpipe would fall off...

    Paul
    After the sorry wings saga, now this, is there anything on a Eurostar that DOESN'T fall off?

    :freaked:

  10. #10

    Rear starboard exhaust tube broken........ Again

    Phil, read the full message from Paul , he was referring to the exhausts on skyrangers.

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