Upgrading DA42 with CD-155 engines

[ememic99]

Introduction

I made my decision about this upgrade long time ago. Basically, it was my intention since purchasing DA42 because at that time (July 2014) it looked that CD-155 (at that time Centurion 2.0s) STC for DA42 would be approved soon, since Mr. John Crosby had been in the final stage of the process. I still had some 500 hours available on current CD-135 engines and reasonably hoped STC would be available before I had to replace the engines. Diamond didn’t have any plans on developing such STC at that time (or they didn’t want to share any information about that), since they were pushing their own upgrade with Austro engines.

There were three main reasons why I chose CD-155 over AE300:
- much lower price of the upgrade (this gap has widened even more as time lapses)
- very close if not better performance in terms of climb and speed
- maintaining same weight and consequently same stall and other low speeds

Obviously, the only reason why to replace CD-135 with CD-155 instead of going only for new CD-135 was getting better performance.

Operating costs are maybe in AE300 favor (due to TBO rather than TBR) but having in mind initial price difference and 1800 (AE300) vs 2100 (CD-155) flight hours and possible extension, I don’t see much advantage of AE300 for private use. Also, knowing Diamond’s attitude towards customers once airplane sales is done, I’m not sure that anybody can guarantee reasonable overhaul cost for AE300 in future. What ensures me in such thinking is dramatic rise of AE300 upgrade over the years – it started with €125.000 six years ago to reach something between €320.000 and €400.000 without VAT, depending if you go for just NG (engine replacement only) or –VI (full upgrade, including GFC700).
Finally, in January 2015 EASA approved this STC and issued official document on it. Interestingly, very soon after that (March 2015) Diamond and Continental Motors issued press release with information that Diamond’s own STC for CD-155 was approved by EASA. That opened more options (at least theoretically) and I was under impression that competition would result in comparable pricing.

I was closely watching the situation and while Diamond did only one conversion (the one for STC) Mr. Crosby did several ones. According to information from different sources the majority of DA42 users with CD-135 engines just replaced them with new ones, benefiting from the lowest cost – approximately €90.000. The price of my upgrade was agreed long time ago when I first met Mr. Crosby and when we shook our hands and it’s some 40% higher than simple CD-135 engine replacement. The reasons for higher price are obvious – CD-155 engines themselves are more expensive than CD-135 and there are some cowling, radiators and exhaust system changes that are needed.

In November 2017, I made final plan for last few hours left on engines and asked final quotes from Diamond (for CD-155, NG, and –VI upgrades) and from Mr. Crosby. While Mr. Crosby’s offer was as same as we agreed long time ago, I was quite surprised with Diamond’s offers. CD-155 upgrade was 50% more expensive, while NG and –VI upgrades were in range specified above (€320.000 and €400.000 without VAT). So I didn’t have reason to think much and question my initial decision – it was just the last check of current pricing for peace of mind.

I accepted Mr. Crosby’s offer and we closed the deal beginning of December 2017 with idea of actual performing upgrade in spring 2018. I paid the down payment in exact amount of price of CD-155 engines which was of course used for purchasing new engines because Continental Motors required full payment when ordering. The engines were purchased in December 2017 to avoid usual price increase in new year with planned delivery in March 2018.

[ememic99]

Part one

The choice of the shop was very easy – Aeroservice located at Bled LJBL airport in Slovenia, one of the few shops which has qualified for performing CD-155 upgrade. Besides being geographically close, it’s the shop which has been maintaining my DA42 since I purchased it. On top of that, they have successfully upgraded several DA40, DA42 and C172 aircrafts with CD-155 engines.

My upgrade was scheduled for mid-March, aligning my schedule with shop’s availability which was just about to finalize the same upgrade for Swiss customer. Also, that was aligned with engine delivery time and I only could hope that all parties would keep up with schedule.

Luckily beginning of March Mr. Crosby informed me that engines had already been delivered to Aeroservice and that upgrade could start whenever approved by the shop. So, I flew there few days before agreed date and the works started immediately. First of all, propellers were removed and sent to MT Propeller for rebuild – changing blades while spinner and TKS parts were reusable. I opted for new Scimitar propellers because I had unique opportunity to exchange them relatively cheap.

[ememic99]

Part two

Instead of planned 5-6 weeks, the upgrade took 8 weeks. As usual, the delay was not caused by one thing but it was a combination of several stuff. As the parts (cowlings, exhaust and props) were supplied from different countries I was unfortunate to hit some public holidays in each country and this caused almost a month of delay. However, Aeroservice worked hard to pick up and complete job once everything was delivered to their shop.

My first flight (after the shop owner made few ground runs and test flights) was short one from Lesce LJBL to Ljubljana LJLJ to do the immigration check, followed by a bit longer flight from Ljubljana to Zagreb LDZA. I didn’t have the opportunity to check many different settings but the numbers I recorded on this flight were exactly as expected.

Altitude 8000 ft, measured TAS:
- load 90% CD-135 160 kts (FF 7.2 g/h per engine), CD-155 171 kts (FF 7.8 g/h per engine)
- load 85% CD-135 156 kts (FF 6.7 g/h per engine), CD-155 168 kts (FF 7.4 g/h per engine)
- load 80% CD-135 153 kts (FF 6.2 g/h per engine), CD-155 165 kts (FF 7.0 g/h per engine)
- load 75% CD-135 150 kts (FF 5.7 g/h per engine), CD-155 161 kts (FF 6.6 g/h per engine)

So the gain in speed from burning more fuel is obvious and it’s some 11 kts TAS at mid-altitudes. However, what surprised me was that I got some speed increase at the same FF – to be checked in the future.

[ememic99]

Performance

On Sunday I departed from Zagreb to Berlin Strausberg EDAY with plan to test as much a possible combinations of engine load and altitude. However, due to convective weather both on outbound and return flights I was able to check the performance only on higher altitudes.

FL 180, measured TAS:
- load 80% CD-135 167 kts (FF 6.2 g/h per engine), CD-155 175 kts (FF 6.8 g/h per engine)
- load 75% CD-135 163 kts (FF 5.7 g/h per engine), CD-155 173 kts (FF 6.6 g/h per engine)
- load 70% CD-135 160 kts (FF 5.2 g/h per engine), CD-155 170 kts (FF 6.2 g/h per engine)

FL 170, measured TAS:
- load 80% CD-135 165 kts (FF 6.2 g/h per engine), CD-155 175 kts (FF 6.8 g/h per engine)
- load 75% CD-135 161 kts (FF 5.7 g/h per engine), CD-155 171 kts (FF 6.5 g/h per engine)
- load 70% CD-135 158 kts (FF 5.2 g/h per engine), CD-155 168 kts (FF 6.2 g/h per engine)

So it seems consistent to gain in speed at mid-altitudes comparing to CD-135 – it’s around 10 kts TAS at the same load percentage. And again as in previous flight I noticed the gain in speed at same FF.

Regarding climb performance, that something that I have to measure across several flights but initial results seem to be ok. I measured it at MTOW and got following reults:
- up to 6000 ft, 100 KIAS, 1200 fpm, 100% load
- to 8000 ft, 102 KIAS, 1100 fpm, 100% load
- to 9000 ft, 102 KIAS, 1100 fpm, 98% load
- to 10000 ft, 100 KIAS, 1000 fpm, 97% load
- to 11000 ft, 98 KIAS, 1000 fpm, 95% load
- to 12000 ft, 92 KIAS, 900 fpm, 92% load
- to 13000 ft, 91 KIAS, 900 fpm, 91% load
- to 14000 ft, 90 KIAS, 900 fpm, 90% load
- to 15000 ft, 89 KIAS, 900 fpm, 88% load
- to 16000 ft, 89 KIAS, 800 fpm, 87% load
- to 17000 ft, 87 KIAS, 800 fpm, 83% load
- to 18000 ft, 87 KIAS, 800 fpm, 82% load

I picked up initially 100 KIAS as cruise climb speed just to see how fast I can climb at “high speed”. However, climbing at 86 KIAS (POH value for cruise climb) gives 1350 fpm or better at lower altitudes. 8000 ft is critical altitude for CD-155 and after that max available power decreases. Next time I’ll climb at constant IAS (e.g. 90 kts) all the way to cruise altitude to check how rate of climb decreases at higher altitudes.

OEI performance was tested only during test flights, so I have to see it myself. However, it’s not easy to test it at MTOW because usually I’m alone on such flights.

Of course the results are much better than with CD-135 engines – e.g. with CD-155 I had 1400 fpm at 1000 ft climbing at 86 KIAS while with CD-135 I had 1100 fpm under same conditions.

[TimS]

Keep the report coming.
Did you record fuel flows from before for comparison?
I would be interested more in the performance and fuel flows around 8-12K altitude; I generally avoid going higher since I do not like to wear O2.

Tim

[ememic99]

I have FF data for CD-135 at these altitudes but still miss it for CD-155. As you can see above, I made comparison of FF between these two engines for the altitudes I flew.

[TimS]

I have FF data for CD-135 at these altitudes but still miss it for CD-155. As you can see above, I made comparison of FF between these two engines for the altitudes I flew.

Nice. I did not know the fuel flows from the 135 were from your plane or book values.
Eyeball looks like you gain around three knots actually for the same fuel flow.
If you have the KIAS I would think it would be more useful when looking to compare identical fuel flow. I find KIAS is less susceptible to variation caused by temp and pressure differentials.

Anyway, nice looking upgrade!

Tim

[Keith M]

Emir, before I upgraded my DA40 from CD135 to CD155, its fuel totaliser was dead accurate and the fuel flow at 75% was close to yours at 5.6 gph. However, now it only reads 6.2 gph compared with your 6.5 gph. This may explain why when I fill up, I can get a gallon more in the tanks than the totaliser indicates. Do you know if it needed to be recalibrated after installing the CD155?

[ememic99]

Emir, before I upgraded my DA40 from CD135 to CD155, its fuel totaliser was dead accurate and the fuel flow at 75% was close to yours at 5.6 gph. However, now it only reads 6.2 gph compared with your 6.5 gph. This may explain why when I fill up, I can get a gallon more in the tanks than the totaliser indicates. Do you know if it needed to be recalibrated after installing the CD155?

Actually there's no "fuel totalizer" device in CD engines or DA40/42 airframe. It's FADEC that gives the number which is presented on panel, so I'm not sure you can calibrate it. I had the same situation with CD-135 (under-reading 5%) and I confirmed it across 500 flight hours and many refuelings. The numbers I published above for CD-135 are corrected (and accurate) ones while for CD-155 I have confirmed numbers only during 7 flight hours and two refuelings (seems accurate for now).

[ememic99]

I have FF data for CD-135 at these altitudes but still miss it for CD-155. As you can see above, I made comparison of FF between these two engines for the altitudes I flew.

Nice. I did not know the fuel flows from the 135 were from your plane or book values.
Eyeball looks like you gain around three knots actually for the same fuel flow.
If you have the KIAS I would think it would be more useful when looking to compare identical fuel flow. I find KIAS is less susceptible to variation caused by temp and pressure differentials.

Anyway, nice looking upgrade!

Tim

Here are IAS numbers:

FL 180
- load 80% CD-135 124 kts (FF 6.2 g/h per engine), CD-155 131 kts (FF 6.8 g/h per engine)
- load 75% CD-135 122 kts (FF 5.7 g/h per engine), CD-155 129 kts (FF 6.6 g/h per engine)
- load 70% CD-135 120 kts (FF 5.2 g/h per engine), CD-155 127 kts (FF 6.2 g/h per engine)

FL 170
- load 80% CD-135 125 kts (FF 6.2 g/h per engine), CD-155 133 kts (FF 6.8 g/h per engine)
- load 75% CD-135 123 kts (FF 5.7 g/h per engine), CD-155 131 kts (FF 6.5 g/h per engine)
- load 70% CD-135 121 kts (FF 5.2 g/h per engine), CD-155 129 kts (FF 6.2 g/h per engine)

Altitude 8000 ft
- load 90% CD-135 140 kts (FF 7.2 g/h per engine), CD-155 151 kts (FF 7.8 g/h per engine)
- load 85% CD-135 136 kts (FF 6.7 g/h per engine), CD-155 148 kts (FF 7.4 g/h per engine)
- load 80% CD-135 133 kts (FF 6.2 g/h per engine), CD-155 145 kts (FF 7.0 g/h per engine)
- load 75% CD-135 130 kts (FF 5.7 g/h per engine), CD-155 138 kts (FF 6.6 g/h per engine)

Have in mind that critical altitude for CD-135 is (was) 6000 ft, while for CD-155 is 8000 ft.