Robin DR401 with CD155 reliability (and diesel v. Lyco/Conti engine reliability)

L_C wrote:

My question is for luckymaaa : is the problem with the flaps fixed now ?

I’m not luckymaa but my club have had the same problems with either (or both) the DR401 and DR400 CDI.

For the flaps (happened essentially on the DR400 CDI), I think they changed practically the whole flaps actuator system to resolve the problem. In the end, they are not even capable of saying what was wrong.

For the engine, we replaced both engines with the new generation of the engine.
So far (4 months of operations for the 401, and one month for the other), so good.

boscomantico wrote:

True. On trainers and rental planes, Vfe is busted almost daily

However, on many trainers (e.g. C150/2, C172) there is an approach flap (10 degree) Vfe which is about cruise speed (or higher!), and usually the speed will have bled down below Vfe for full flaps by the time the electric flaps slowly grind their way past 10 degrees.

I agree, uncommanded flap movement is not funny in the least!

I had this with a faulty flap switch in my old C150 twice, both were not funny, not in the least.

One was in initial climb when the flaps extended to 40 degrees (from 10) accompanied with a vicious pitch up. I managed to retract them by holding the flap switch in the up position manually the whole time until base leg, then let them extend again for landing. They changed the flap switch.

On another flight 2 years later, the opposite happened and the flaps retracted on short final. Again the flap switch was changed and the circuit breaker as well for a model which can be pulled.

Do I need to say I prefer manual flaps? Seneca II, Piper 28 or vintage Mooney any time please.

It doesn’t stop there. Quite a few airliners have flap problems regularly. I recall an A330 which came back with zero flaps 4 times in a row before they flew it to Toulouse for them to figure it out. It took 3 weeks to fix…

I’ve just been through the latest stats for the CD engines.

IFSD rate 1.74 / 100k hours, note the required IFSD rate for ETOPS 180 is 2 / 100k…

Unscheduled maintenance events 1.1 / 1’000 hours.

Shorrick_Mk2 wrote:

I’ve just been through the latest stats for the CD engines.

I am curious about the source of this. Could you share?

Do you have source for the numbers concerning Lyco/Conti?

http://www.continentaldiesel.com/typo3/index.php?id=106&Year=2017&NewsID=178&L=1

No source for Lyco / Conti but then again as there’s no way to easily centralise the data and follow up on repairs / incidents there will never be such a statistic either. And it’s not like they have an actual incentive to run one ^^

IIRV the BEA report on the Thielerts published a couple of years ago claims that the IFSD rate given by the FAA for Lyco/Conti is 10/100Khrs.

No source for Lyco / Conti but then again as there’s no way to easily centralise the data and follow up on repairs / incidents there will never be such a statistic either.

You don’t know what you don’t know so you can’t know the extent of under-reporting.

• Nobody with a brain would approach this by phoning engine shops – there must be hundreds if not thousands (shops and A&Ps doing engine work) just in the USA. The only way is to approach aircraft owners, from the FAA aircraft database. And that way you will get massive OVER-reporting because most people respond only if they have something negative to say (look at any pilot forum ). Look at that infamous PA46 survey which reported a massive INFS rate of (from vague memory) 10%. If that was true, most of the fleet would be dead. They did have lots of problems but obviously nowhere near that figure, and most were cracked cylinders. I have just ordered a Dell XPS13 laptop and 100% of the user feedback on their website is negative… So the easier data collection on diesels (because the mfg has owners over a barrel so has better data) doesn’t really help you.

• Differing mission profiles. The majority of diesels are operated by schools, which means very easy mission profiles.

• Most schools have tame (or even in-house or owned) maintenance arrangements. Remedial action isn’t necessarily going to get reported.

• Different ability to abuse the engine. The vast majority of flight training is done with the old engines. These are abused all the time. Whereas, for self fly hire, IME, diesel planes are rented out only to pilots which the school is happier with.

• The old engines are more vulnerable to abuse, due to the manual controls and often poor pilot training. The diesels with their ECUs will last longer in the hands of technically inept pilots (I am sure somebody will turn this around against me, as some always do, but it is like the Airbus v. Boeing argument). So the resulting stats are like the old argument about flying = motorcycling in safety terms, when actually the vast majority of bike accidents are either caused by a car or involve another vehicle (the rider would not have crashed on an empty road) and most of the rest are e.g. idiots doing 150mph on a country lane.

Some of these could work one way and some could work the other way, but nobody really knows which. Your “data” could be off by 10×. I could give you examples from electronic manufacturing where the most unexpected factors conspire to deliver either great or crap reliability.

And it’s not like they have an actual incentive to run one

No mfg has such an incentive… I would argue the “new engine” mfgs have a bigger incentive to hide data – because the old stuff is a known quantity and their defects are generally accepted and “lived with” by their owners so to them nothing would be earth shattering data.

BEA report on the Thielerts published a couple of years ago claims that the IFSD rate given by the FAA for Lyco/Conti is 10/100Khrs.

Given that the BEA will write in an accident report “the flight was in VMC” because it was on a VFR flight plan, when actually it was in solid IMC (departing into OVC006) for about 500nm, I would not expect the BEA to do anything excessively diligent when it comes to GA

A school has an easier mission profile?! I was thinking repeated landings and takeoffs with the assorted power changes are harder on an engine.

In-house maintenance won’t save you from remedial action reporting, as CD will know when you hook up to the ECU.

Interestingly enough, in the US, 41% of bike rider deaths were caused by crashes were no other vehicle was involved. Doesn’t sound like a vast minority.

Here’s what @aviathor referred to as the ‘source’ for the BEA report

http://www.technify.de/typo3/index.php?id=530&backPID=530&tt_news=2027&L=1

See last paragraph. No direct source data of course, but it is published by Continental themselves, so they must somehow believe it is more or less accurate. BTW, in all later press releases this piece of data is no longer used. I guess they realize that if the difference between the reliabilities becomes as large as an order of magnitude less, it becomes embarrasing and they still like to sell some Avgas engines for the time being.