DA40NG article in Aviation Consummer

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Rich
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DA40NG article in Aviation Consummer

Post by Rich »

A nice, complimentary article in the Feb issue, but I responded with some misstatements regarding the Lycoming versions and DA 40's in general:

As a DA40 owner since 2002 and active participant in DiamonAviators.net I need to correct some misstatements in the article. The Diamond POH has not been updated to reflect performance changes in the Lycoming models since the early models. With the introduction of the PowerFlow as standard and some aerodynamic cleanup, these later models have best cruise speeds in the high 140-knot range. My '02 has had the PowerFlow added and routinely cruises in the low 140s and delivers 141 KTAS at 10,000 ft. Climb is much enhanced with this change and at lower altitudes beats book climb rates by 300+ FPM at lower altitudes.

On the flip side, one thing often misquoted is the fatal accident count for DA40s. There have been 7 fatal DA40 accidents over time in the US, not 3. 7 is still a very lower number. Your writer made the mistake of including the model number in the NTSB inquiry. Due to a lack of discipline in the data entry in this database, using too much filtering results in incorrect results. Entering "DA40" for the model number yields only 3 accidents. "DA-40" yields 2 more. And there are yet 2 more hiding as "DA40-180" and "DA40 F". I've found, not just for DA40's, but for any make, it's best to leave out the model and manually scan the results.

I did not include one last observation in the email, which I'll make here. To date there have been no fatal DA40 NG accidents in the US but there have been 5 non-fatal accidents due to power loss. As far as I can tell, there have been no accidents among the Lycoming-powered DA40s involving power loss.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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chili4way
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Re: DA40NG article in Aviation Consummer

Post by chili4way »

Rich, I think you make a good point about the relative maturity of the engines involved (1955 vs. 2009) as the differences in airframes are relatively minor and unlikely to contribute to in-flight engine issues. Disallowing power loss by fuel exhaustion (more or less an equal opportunity mishap), this comes down to differences in the engines and their reliability.

From what I've seen, issues with the turbocharging system in the AE300 have been the predominant cause of reduction/loss-of-power issues. Austro continues improve the engines with ADs and MSBs to incorporate new learning (although it would suck to be the one of the five who have paid their tuition).

Comparing the reliability of a normally aspirated engine to a turbocharged one is a bit of apples & oranges. So is specifically limiting the scope of IO 360 inflight issues to Diamond Aircraft when the Austro Engines are uniquely in Diamond Aircraft.

There is a tradeoff in adopting any new technology, and each of us has to decide if the advantages are worth the risks. My DA40NG cruises at 155KTAS at 12,000 ft on 7.9 gph.
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Re: DA40NG article in Aviation Consummer

Post by Rich »

chili4way wrote: Sat Jan 25, 2020 4:54 pm Comparing the reliability of a normally aspirated engine to a turbocharged one is a bit of apples & oranges. So is specifically limiting the scope of IO 360 inflight issues to Diamond Aircraft when the Austro Engines are uniquely in Diamond Aircraft.

My DA40NG cruises at 155KTAS at 12,000 ft on 7.9 gph.
I believe it to be statistically valid and relevant, as the numbers of LYC-powered DA40's are sufficiently large and it puts the 2 engine types in the most similar environments possible. The two are also in the same HP range, though the Austro needs the turbocharger to achieve that. FWIW, I haven't been able to find any such failures among the (admittedly few) Thielert/Continental diesels.

Here is an interesting thing: There have been no fatal accidents in the US to date involving any of the Diamond diesel-powered aircraft, single or twin. Overseas is a totally different matter. Relative fleet sizes may play a role here, but zero is zero.

He did understate the cruise speeds. The Lycoming due to the annoyingly out-of-date POH performance figures. But for whatever reason, it appears he used book speed for the NG at 75% power. Whereas I figure most of you cruise at 92%. I made no comment about the NG in my response, as I have no first-hand knowledge.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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Re: DA40NG article in Aviation Consummer

Post by Boatguy »

The performance numbers are entirely understated, even in the AFM. I cruise at 85% power, 7.6gph, and typically see what the AFM quotes for 92%. Two panel photographs from last year:

14,600' -7C (ISA +6) 120KIAS / 153KTAS (AFM 153 @ 92%)
8,000' 10C (ISA + 11) 128 KIAS / 146KTAS (AFM 146 @ 92%)

Also understated is the fuel burn and useful load benefits. Climbing at 92% I burn 8.3gph, but descending at 45% I burn 4.0gph. Since I climb faster than I descend, this pulls the average down to more like 7gph for a trip. O69/KVGT last year was 18.25gal in 2.8hrs on the Hobbs. So a 3hr trip, plus 1hr reserve is 28 * 6.8 = 191lbs. The same trip and reserve burning an average of 11gph of avgas = 44 * 6 = 264lbs of fuel. 73lbs of additional useful load from fuel efficiency.

And the icing on the cake is that Jet-A is usually less expensive than avgas.

I'll send an email to Aviation Consumer!
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Re: DA40NG article in Aviation Consummer

Post by Rich »

Another area I didn't get into was the take on useful loads in the article. The POH example values and marketing brochures are useless in this regard. In addition, there is substantial variation among individual airplanes. On our wiki page (which for some reason include no entries for anything but Lyc-powered A/C and nothing later than 2010 models) shows UL from 941 lb (this happens to be my plane :D ) down to 811. That's a whopping 130 lb. range. In my case I run out of physical space, even with the extended baggage, before hitting the MTOW of 2646 (which also was ignored in the article, though it is the norm) or having CG issues.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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Re: DA40NG article in Aviation Consummer

Post by shorton »

Boatguy wrote: Sat Jan 25, 2020 11:56 pm The same trip and reserve burning an average of 11gph of avgas = 44 * 6 = 264lbs of fuel. 73lbs of additional useful load from fuel efficiency.
A realistic average fuel burn on that trip with the IO-360 is 9 gph. 11 is way too high. So its only a 25 pound difference. Now add the 50 pounds of ballast to the rear that I'd need in the NG due to its too heavy engine and poor CG envelope and the Lycoming has more useful load.

Some errors in the article have been noted. A big issue for me in the training environment is stall speed, which is, in part, a result of the forward CG. The article quoted clean stall speeds of 59 for the NG vs. 53 for the Lyc. Not so. It's 66 vs 53. An enormous 13 kts!
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Re: DA40NG article in Aviation Consummer

Post by Boatguy »

shorton wrote: Sun Jan 26, 2020 8:00 am
Boatguy wrote: Sat Jan 25, 2020 11:56 pm The same trip and reserve burning an average of 11gph of avgas = 44 * 6 = 264lbs of fuel. 73lbs of additional useful load from fuel efficiency.
A realistic average fuel burn on that trip with the IO-360 is 9 gph. 11 is way too high. So its only a 25 pound difference. Now add the 50 pounds of ballast to the rear that I'd need in the NG due to its too heavy engine and poor CG envelope and the Lycoming has more useful load.

Some errors in the article have been noted. A big issue for me in the training environment is stall speed, which is, in part, a result of the forward CG. The article quoted clean stall speeds of 59 for the NG vs. 53 for the Lyc. Not so. It's 66 vs 53. An enormous 13 kts!
Since these threads are often referenced much later by prospective buyers I'll add some real world data.

The only time I've used rear ballast is when I had a 250lb (113kg) CFII in the right seat on a training flight. For training flights useful load is usually irrelevant since there is no luggage and the flights are rarely more than 2hrs.

For the trip to Las Vegas with my wife that I referenced in an earlier post, this was the W&B:

Pilot: 190
Co-pilot: 130
Fuel: 28gal = 190
Oxygen tank + ditch bag = 12
Luggage: 40

TO weight 2,601 (1,180kg), 287lbs of unused useful load and well within the envelope.
LDG weight 2,459 (1,115kg) and 9gal in the tanks on landing.

Climbing at 660fpm through 13,000' to cross the Sierras at 13,500'. That's a real world trip in a DA40NG without air conditioning.

The planes with AC have 88lbs less useful load but also have their CG further aft. They essentially always have 50lbs of luggage in the baggage tube, cooler owners in the summer and don't need ballast with a 250lb CFII :) !

I'm admittedly a low time pilot so maybe I'm missing something more experienced pilots know because I don't understand the fixation on clean stall speed that crops up from time to time. Vref is nominally 1.3x Vso, so as stall speed decreases, the margin of error between Vref and Vso also decreases. Particularly in Diamonds, if you're on the high side of Vref you're going to float and float which in training sets the stage for porpoising or a botched go-around. So if we're both flying the correct Vref, the heavier plane actually has slightly more margin of error on speed.

There is certainly a difference in landing distance. At KVGT the AFM says I need 1,300', but reducing that to 1,100' would just mean the tower controller is more annoyed as they watch me high speed taxi to the first turnoff. At a shorter strip like KPAO (2,400') we're both going to take the same turnoff.

In the case of an off field emergency landing, slower is definitely better with less energy to dissipate. If that's a major purchase criteria then I should buy a Cirrus and pull the chute.

The point is not to disparage the DA40-180, but to clarify the misinformation in the article in comparing the two airplanes and to illustrate a real world trip in a DA40NG. As I write, waynemcc999 is making a very long trip in a DA40-180 over water in the Caribbean; we are fortunate to have choices.
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Re: DA40NG article in Aviation Consummer

Post by Rich »

Somehow this has turned into mutual model-bashing. The Lycoming vs. NG is a bit of apples-oranges, anyway. The NG is clearly superior at cross-country, higher-altitude flights. The Lycoming-powered planes have better low-altitude power-loading and the engines have less regularly scheduled maintenance and you can get parts and service almost anywhere.

And mine is the bestest of all :D
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Re: DA40NG article in Aviation Consumer

Post by Rich »

There's one more advantage I'll point out for the NG. Even though I have no first-hand knowledge, but based on experience riding in a DA42: The NG is presumably much smoother and quieter than my rattletrap Lycoming :thumbsup:
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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Re: DA40NG article in Aviation Consummer

Post by AndrewM »

When I flew one, I think one of the key advantages (amongst a number) was the ease of start up, FADEC control and most of all the smooth and quiet operation. The noise reduction is huge in my view, which would make long flights more comfortable and less taxing. Also, I think with the shorter wings due to the winglets the NG can fit in a standard hanger.

Would be great to get some PIREPS from those who have owned the Lycoming DA40 and then switched to the NG. I know there are not a lot of those folks, but there a for sure a few now.
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