DA40NG

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Re: DA40NG

Postby jb642DA » Thu Feb 15, 2018 1:41 pm

Nice report Andrew!
Question about the DA40 with Garmin NXi - does it have "yaw dampening" and if so, what did you think of it?
Thanks -
John
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Re: DA40NG

Postby TimS » Thu Feb 15, 2018 5:20 pm

nrenno wrote:Tim,

I agree that the article that I cited is not based on quantitative data, and that simplicity does not always implies reliability. However, your comparison of the Lycoming IO-540, PT6-121A and RR Trent is not fair. You are comparing very different technologies, not piston engines with each other.

--Nilton


Curious, what besides that Lycoming and AE-300 have pistons; what else do they have in common?
Likely nothing.
I went up in technology and tolerance; same concept in switching from Lycoming to AE-300.

Tim
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Re: DA40NG

Postby shorton » Thu Feb 15, 2018 5:38 pm

CFIDave wrote:
shorton wrote:As far as operating cost, there is no doubt that the fuel cost of the NG will be less, but I'm not sure the lifecycle cost of the Austro engine would put the 40NG in the pro column for operating costs. There are a number of expensive inspections and component replacements, I believe at 300 or 600 hour intervals. I've heard grumblings that the hourly engine cost over the 1800 hour life of an Austro engine is nearly $50 per hour. If so, that would far exceed the lifecycle cost of the Lycoming IO-360 M1A. Perhaps someone with more detailed knowledge can comment on that.

There's an article "Diesel Reset: Improved Economics" in the August 2016 issue of Aviation Consumer by well-respected journalist Paul Bertorelli that directly compares total hourly cost (including engine reserve for TBO/TBR, required maintenance, and fuel cost) of Thielert/Continental diesels, Austro diesels, and the Lycoming IO-360.

http://www.aviationconsumer.com/issues/ ... 962-1.html


Thanks for the article Dave. I'm surprised that the midstream mx costs of an Austro are stated to be only 70% what they are for a Lycoming. I was under the impression that the Austro 100 hour maintenance (including the cost of the kit) was quite a bit more expensive than a typical Lycoming oil change and that every 300 hour (including gearbox oil) and every 600-hour maintenance (including new high pressure fuel pump) add quite a bit to the midstream cost. Based on your experience, is $7,000 a realistic cost of engine maintenance over the 1800 hour life of an Austro Engine?
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Re: DA40NG

Postby AndrewM » Thu Feb 15, 2018 7:16 pm

jb642DA wrote:Nice report Andrew!
Question about the DA40 with Garmin NXi - does it have "yaw dampening" and if so, what did you think of it?
Thanks -
John


I did not ask about the yaw dampening, and I had to hold rudder at the usual phases of flight, so I would guess not.

The other question I forgot to ask, that perhaps Dave can help with is whether the DA40 NG w/ G1000 nxi has the envelope protection. I would have thought with some of my maneuvers it would have corrected me if it was active.
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Re: DA40NG

Postby Boatguy54 » Fri Feb 16, 2018 1:33 am

Rich wrote:Just as a theoretical exercise I ran the W&B numbers on a flight I took last year from Spokane to Prineville for both my plane and a sample NG. Basically, myself, my stepdaughter, her two girls (10-13 yrs. old), full fuel and pretty much all the baggage I could stuff in the plane in the baggage compartment and rear seats.

I used the actual weight of my plane and the W&B for the DA40-180, against the sample airplane (which might not reflect any specific actual airplane) in the NG manual and its W&B calculations and limitations:

My plane calcs came out to 2,571.40 lb., CG 100.39 in.: 74.6 lb. under gross, 1.61 in. forward of rear CG limit.

The sample NG came out to be 2884.4 lb., CG 99.90 in: 10.61 lb. under gross, .30 in. aft of rear CG limit. Now this was using 7.01 lb./gal as fuel density, as it has in the manual. So I tried it at 6.7 lb./gal fuel density, an oft-quoted density for Jet-A. This came out to be a bit better at 2,865.3 lb. and 99.88 in. CG. But CG is still out of aft limit by .28 in.

My plane is a bit unusual, being one of the lighter, earlier ones with standard tanks, extended baggage and MTOW mod done. For this flight the front seats totaled 340 lb., rear seats (including various stuff the kids had there) totaled 200 lbs. and 100 lbs. in Forward baggage.

Obviously there is uncertainty around a couple of the numbers used for the NG. One of which is Jet-A fuel density. Poking around one can find various values for this fuel. But this exercise does show that it's pretty easy to bump up close to, if not beyond the rearward CG limit in the NG if you utilize extended baggage. It's the most restrictive in rearward loading of the DA40 variants. I can tell you I've stuffed this area full quite a few times over the years.

My club has a 2007 DA40/XL and a 2016 DA40/NG and provides a W&B calculator for each individual aircraft in the club. I put your numbers, as best I understand them, into the calculator and got these results:

DA-40/XL N732DS
Empty: 1798 (arm 98.6)
Front: 340
Back: 200
Baggage: 100
Fuel: 208 (34.7gal)
Total: 2,646 (MTOW)
CG aft of CG limit by 1.48"

DA-40/NG N125NG
Empty: 2030 (arm 96.4)
Front: 340
Back: 200
Baggage: 100
Fuel: 218 (32.5gal)
Total: 2,888 (MTOW)
CG aft of CG limit by 0.42"

I'm a student pilot and clearly no expert in this, but my take is that neither plane could accommodate this load. I was able to just balance the plane with these loads:

DA-40/XL N732DS
Empty: 1798
Front: 340
Back: 200
Baggage: 5
Fuel: 264 (44.2gal)
Total: 2,608

DA-40/NG N125NG
Empty: 2030
Front: 340
Back: 200
Baggage: 74
Fuel: 250 (37.3gal)
Total: 2,885

The NG is carrying more baggage and my guess is that they both have about the same range. This may be an issue with the specific 2007 XL and perhaps it is not representative of newer DA-40/XLTs.

The heavier engine in the NG pulls the CG forward about 2.2" which enables it to carry more baggage. Of course as many have observed, this is at the cost of poorer low altitude climb performance.
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Re: DA40NG

Postby CFIDave » Fri Feb 16, 2018 2:18 am

New DA40 NGs come with the new G1000 NXi flight deck, but no yaw damper and no ESP (envelope protection). Both of those are standard in new Diamond twins (DA42-VI and DA62).
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Re: DA40NG

Postby jb642DA » Fri Feb 16, 2018 2:39 am

Thanks Dave!
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Re: DA40NG

Postby Rich » Fri Feb 16, 2018 5:21 am

This is interesting:

DA-40/NG N125NG
Empty: 2030 (arm 96.4)

There must be some optional equipment in this plane because although the moment arm is considerably less that the XLT you have available, it's 0.9 inches further back than mine (95.46), with the lighter engine and the MT prop (as the NG would have, though maybe a different model). It's well known these older DA40's tend toward nose-heaviness, but I didn't think an NG would be less so.
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Re: DA40NG

Postby Antoine » Fri Feb 16, 2018 5:30 am

The DA40 XL is not a good representative of the DA40-180 breed. It has a known "aft CG" issue with compliments of the clever guy who decided to place some avionics in the tail while at the same time the aircraft got a lighter prop.
I had mine modified by moving said avionics to under the passenger bench, to somewhat alleviate the problem and Diamond offer a ballast kit for the nose. If an XL doesn't have it and has the 50 USG tanks (which is standard unless explicitly ordered without) it will have a very restrictive aft CG limit.
It is interesting that the NG has an even more restrictive aft CG limit than the 50 gallon DA40-180.
This implies that either the winglets issue remains despite smaller tanks, or some weird side effect of the 200+ lbs additional weight in the nose. Maybe more polar moment?

As a reminder: when the XL was announced, it had beautiful winglets and a significantly higher top speed claim (156 or 158 IIRC), but it failed spin recovery tests and the winglets were removed. They are back in the NG.
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Re: DA40NG

Postby CFIDave » Fri Feb 16, 2018 2:35 pm

The reason the DA40 XL failed spin testing with winglets was because of the high polar moment of inertia of the extended range (50 gal) fuel tanks located out near the wingtips. Because the DA 40 NG is much more fuel-efficient than a Lycoming DA40, it doesn't need the outboard wing tanks of the XL/XLS/XLT, with the NG's fuel capacity of only 39 instead of 50 gallons in the wings. That's why the NG can pass spin certification tests with winglets.

Here's a video showing Diamond's flight tests of the DA40 NG doing stall and spin testing:
https://www.youtube.com/watch?v=GQXLUaA3yo4
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