OEI landing DA42

aart wrote:

require a replacement of coolant hoses every 5 years, probably the same for Austro engines.

Actually doesn’t look like it – I checked the Austro AE300 Maintenance Manual & there’s a 100 hr visual inspection and cleaning of all fuel & coolant lines, but no scheduled replacement interval. The Conti & Austro maintenance regimes seems to differ quite a bit…

I don’t think you need to go for automotive stuff, when an NPT-terminated hose with an EASA-1 form is so relatively cheap. The issue is with metric-terminated hoses, which is why I asked if that’s what they were. I would expect Thielert to be metric, but who knows? Apparently Airbus use NPT hoses – presumably because they want to sell to the USA.

Mine were replaced in 2012 and that’s when and where sloppy work came from.

So that was up in Sweden? If so, that’s not what would expect in that country..

Do you have to buy the hoses from Conti?

At that point in time yes. Since then, my service station has been looking for commercial (automotive) replacements and I think he does that now.

Do you have to buy the hoses from Conti?

You get the same issue with Socata. The engine hoses are US-thread (NPT) and thus cheap. The one external oil hose (apart from the six little ones feeding the rocker covers, there is only one oil hose, for the oil pressure sensing, and it is fed via a restricted orifice in case of a leak) is ISO metric thread and very expensive – about 10x the normal price. One can get them made but the French outfit (Aeroquip) which has a monopoly on the fittings notices they are Socata hoses and quotes a very long lead time But the cost is still 50% of Socata’s. I got two made by Saywells in Worthing, UK, a while ago.

Thank you, Emir, for the information and congrats how you handled the emergency!

One thing is sloppy installation mentioned earlier. A disgrace. Another thing:

Thielert (the name sticks, although it is now a Conti CD-series engine, so much better ) engines require a replacement of coolant hoses every 5 years, probably the same for Austro engines. Costly, and a little frustrating too, because when mine were replaced 2 years ago the mechanics and I looked at the old ones and could not distinguish them from new.. Clamps and other hardware looked fine too.
So, I was left with the feeling that I had not only spent money for something that was probably not needed, I had also introduced a risk in that someone could have made a mistake in this pretty extensive re-hosing job. ‘Why change a winning team’ came to mind.

Nice little revenue stream for Conti. But (if they are not already doing so) it is high time for them to consider extending the replacement interval of these components or come up with an inspection procedure rather than calender-time replacement. They need to continue to bring down maintenance cost if they want Diesels to become the de-facto standard in GA. Although there are other advantages of flying Diesels, cost is still the name of the game. In most places of Europe the equation of extra maintenance vs fuel cost saving works out in favor of Diesels, in the US it probably doesn’t.

achimha wrote:

there is almost no access (TB20 comes to mind).

You ought to buy one and then you will see. One can inspect much of the hoses from underneath, by shining a lamp up the air exhaust holes at the bottom. I do that on every preflight. Do you remove all the covers on every preflight?

Few planes (no modern ones, AFAIK) have all the engine covers fully removable, and those I have flown that have, tend to have shagged fittings.

Regarding water cooling, the issue I see is that the mfgs don’t want to spend money on high quality fittings and hoses. On an aircraft, I would use nothing less than steel (stainless, for water coolant) fittings and PTFE hoses which are braided and fireproofed. At around €50-100 each, such hoses are a complete no-brainer, and I cannot understand who so many planes (especially non-certified ones) don’t use them everywhere. Then you need to have proper strain reliefs / hose mounts which stop them flopping about – this is another neglected area.

The reason why loss of coolant is a major item on cars (my Toyota Celica had only one stoppage in the 15 years I had it from new – exactly this) is because they use crap hoses for the water.

However, in Emir’s case, it was down to monkey maintenance, and this brings me back to what I keep saying about the owner having to get “stuck in”, but I get criticised for suggesting that there are bad maintenance companies out there. The reality is that anybody who has a “mechanical/technical brain” (and Emir certainly has) can inspect the work done. Yes… I know about airfield politics, and sometimes this is a problem if the only maint company you have doesn’t want you inspecting their work.

And doing, or being involved in, the 50hr checks is a priceless bonus because you get to know what your plane should look like under the covers – at a cost of a few hours of your time every few months.

Those without a technical aptitude, or those who want to treat their plane like a BMW/Merc/whatever will always be exposed to these issues and they have no choice. That’s GA for you

achimha wrote:

In my experience with engine failures (and I have too much experience there), an open liquid circuit is one of the main reasons for engine failures.

Exactly ! So with liquid cooled you now have effectively DOUBLED your chances of failure on each and every flight.

Of course Michael is right, what isn’t there can’t break and what is there will eventually break.

However, our air cooled Lycontosaurus engines already have a large number of oil hoses, fittings, etc. The more add on things like constant speed prop, turbo chargers, suction pumps, the more oil hoses going around. Those hoses are often of poor quality and their attachments even worse. There is only one oil pump by the way.

Therefore the water cooling plumbing doesn’t really change much. As part of my pre-flight on longer/more demanding trips, I remove all cowlings and check all hoses. I’m lucky that my airplane can be fully opened in 1 minute with a few camlocks, knowing that there are other models where there is almost no access (TB20 comes to mind).

In my experience with engine failures (and I have too much experience there), an open liquid circuit is one of the main reasons for engine failures.