DA40NG

[Colin]

No, I don't believe the data included the 1.7 version. It was from Centurion (I guess Continental?) but it was a few months back and I didn't save it (other than remembering those two numbers).

[nrenno]

Colin,
We should not trust any information that cannot be verified. In my opnion, we should not even repeat information that cannot be verified without adding a big caveat. Some might take it as being the truth. If it gets repeated many times, it might get accepted as the “truth.” I have serious doubts about the number quoted (1 failure each 10^5 hours) for the reasons explained in my previous message.

[Karl]

Well I can only speak to the TAE/Centurion/CD engine.

We have logged well over 200,000 engine hours on a mix of 1.7 and 2.0 engines and we have had 3 failures which seems pretty close to the figure quoted by Colin and far exceeds the FAA quoted failure rate of 1 per 10,000 hrs for Avgas engines.
One was a cracked fuel pipe on a new 2.0 it resulted in an off airport landing and an EASA emergency AD.
The other 2 were also 2.0 and were caused by clutch failure (TAE unknowingly purchased a part that had not been heat treated to the stated standard). One ditched in the sea with no injuries and the other was landed on the beach with no damage by a solo student.
Although we had issues with the 1.7 it never resulted in an in flight shut down.

We had a few engine shut downs in twins while flying asymmetric but once we had given some guidance to the pilots it never happened again.

We lost another 2 aircraft, one was due to the student inadvertently shutting the engine down and the other was loss of control during an unauthorized low level tail chase.

Although the 1.7 was difficult to keep serviceable part of that was due to it being new technology and partly due to engineering inexperience with Diesel aircraft engines. All our aircraft were converted to 2.0 some time ago and when maintained correctly we get few if any defects between maintenance visits.

As stated above, we have flown a lot of hours and therefore have a well experienced maintenance team. When I visited the factory in 2011 TAE told me we were logging over 25% of the total engine hours for the 1.7/2.0 fleet.

[nrenno]

Karl,

What do you mean when you say "We have logged well over 200,000 engine hours." Who are we? How many airplanes do you have in the fleet that logged 200,000? One single engine running for 200,000 hours is statistically different than 100 engines running for 2,000 hours.

In addition, in order to have statistically significant numbers, we need to analyse dozens of cases, not 2-3 cases (failures). Good data (large sample sizes) and careful analysis are required for deriving statistically significant results.

What is necessary for the proper comparison of the various engines, is the estimation of probability of failure of each of them. This is a much more complex calculation.

I am involved in this discussion because this an important issue that I care about. It would be great to have the data necessary for making informed decisions.

[Karl]

Nrenno,

The who, is the company I work for.

16 DA 40 and 6 DA 42.

Aircraft engines have an overhaul life, so engines have flown between 1200 hrs and 2000 hrs depending on the model.

We as forum members will probably never have all the information required to derive statistically significant results.

The quoted estimation of the probability of failure was done by others. FAA/Diamond.

I was providing the information because due to the hours we have flown I probably have more information available to me than many other forum members.

My experience of TAE Diesel engines failures fits closely with the figures quoted.
As an aside I think the figures come from Diamond not TAE/CD. Where Diamond got them from, who knows?

[BKR]

Does anyone feel the worries about stalls in the DA40 NG can be mitigated to some degree by the G1000 NXi with GFC700 envelope protection system?

[shorton]

Well I can only speak to the TAE/Centurion/CD engine.
We have logged well over 200,000 engine hours on a mix of 1.7 and 2.0 engines and we have had 3 failures which seems pretty close to the figure quoted by Colin and far exceeds the FAA quoted failure rate of 1 per 10,000 hrs for Avgas engines

I don’t know where the “FAA quoted failure rate of 1 per 10,000” comes from. I’ve seen that quote a few times, but never citing specific FAA authority. Even if it’s true for GA engines historically, the failure rate of the Lycoming IO-360-M1A can’t be anywhere near that.

There are, and have been for more than a decade, around 700 U.S. registered DA40’s. I don’t know the average annual fleet hours, but 100 hours per year per plane seems conservative given the relative low age of the fleet and the number of DA40’s utilized by flight schools. If so, that’s 70,000 hours per year on the fleet of Lycoming DA-40’s. 700,000 hours over 10 years. Going through real data from the NTSB, I don’t see accidents or incidents involving a Lycoming engine failure. If the “1 in 10,000” number were accurate, we would expect 70 failures and many reported accidents over the last 10 years. No way.

[Antoine]

Karl's contribution is an impressive piece of data and I think it should be treated as such. His modesty earns my respect. 200'000 hours certainly is a very impressive background to analyze.
Without getting into statistics, Karl's contribution tells us that the CDI-135/155 has reached a level of maturity that makes it a credible powerplant. Add to this the moderate weight, improved life span and lower replacement frequency of expensive parts and I think we finally have a GOOD aircraft diesel engine.
A DA40 with the CDI-155 and some minor tweaks would get real close to what I call the perfect entry level 4-seater.
And btw, if Diamond bothered to build a DA42-VII around this engine I believe it would be a really nice aircraft.

[nrenno]

Karl,

It would be great if we could use the large data set that your company has to estimate the probability of engine failure as a function of time. It is likely the the probability distribution is not normal because of higher engine failures a low hours related to manufacturing problems and at high hours due to aging. When doing the anaylis, some of the problems mentioned earlier and dismissed need to be include in sample. When doing statistics, the samples cannot be filtered a priory.

The numerous inspections that the Diesel engine, gearbox, and a few other components require worries me because they indicate that at least the regulators do no believed that they are reliable. In my opinion, the limited life time of the Austro engine is another reason for concern. If the engine is so reliable, why it needs to be replaced at such short life time (around 2,000 hours). This is an indication that at least the regulators do not believe that they are reliable when this hour limit approaches.

Where are you located?

[Karl]

Nrenno,

All three of the issues we had were manufacturing issues on small parts. Non were engine failures in the sense of the engine needing scrapping or major repair.
The first one was a metal pipe that cracked due to vibration. The fix was to fit an extra pipe clamp
The clutch failures were caused by springs that had not been correctly heat treated. The repair was replacement of the clutch. OK the one that ditched in the sea was junk, but the one that landed on the beach flew a few days later with the original engine.
2 of the three engines went on to full overhaul time after replacement of parts. The one that landed in the sea could have done the same but didn't for obvious reasons.

We refer to them as engine failures as that is what the pilot sees but probably better described as uncommanded in flight shut down. Non of the engines "lunched" themselves or needed major repairs.

The low lifetime on some components was due to the life extension programme, gain real time data then extend the life.
Most have increased considerably with experience in the field.

The 2000 hr life is in line with most Lycoming and Continental engines.

A quick overview for those that don't know me.
I am from UK. Joined the Air Force in 1980 as an engineer. After I left the Air Force I spent many years restoring warbirds then moved into a management role for a few aircraft maintenance companies. I now live and work in Langkawi, Malaysia. For the first 8 years I was Engineering Manager and the last few years as Lead Quality auditor and Airworthiness Review Staff. I also do contract work on Diamond aircraft across Asia on behalf of the Asia dealer. In the last 2 years I have assisted Diamond owners in Indonesia, Thailand, Pakistan, Singapore and Malaysia.