DA40NG

[Rich]

The discrepancies in stall speeds could perhaps be explained by CG. The manuals don't say, but the stall speeds could measured at most rearward CG for each scenario. The NG is considerably more limited in rearward CG than, especially, the standard tank 180's. I also note that the example empty moment arm for the NG, if realistic, is 10 CM (~4 in.) further forward than my somewhat nose-heavy 180.

My empty moment: 163,366.28 in-lb., weight: 1711 lb, empty CG: 95.48 in.
Example NG empty moment: 183,366.28 in-lb: weight 1984 lb, empty CG: 95.38

So even if the two were not tested at the most rearward CG, if they use the same loadings, the CG would be more forward than the 180, producing higher stall speeds.

[nrenno]

Nothing like having numbers for a quantitative comparison. What is still missing are the measurement errors. How accurate are the measurements of stall speeds?

The significantly higher stall speeds of the DA40-NG might lead to unsafe situations when a pilot used to the DA40-180 flies it.

[Guest]

This is an interesting debate. I’m considering buying a new DA40 NG so keep the comparisons coming. Especially, if you’ve flown both. My real concern isn’t as much the cruise performance as the differences in slow flight maneuvering, take-off/climb performance towards gross weight, and stall speed increase impact on safety.

This is the point I am trying to make right here. Literally every question you are asking is available (with the exception of actually flying the plane) on Diamond's web site under support / technical publications. You can pull up every POH for every plane that Diamond makes.

Yes. I have done this and see the documented numbers. I also have seen that the Lycoming DA40 usually outperforms it’s POH numbers. I’m trying to get out of this discussion if the lower performance numbers at lower altitudes is subjectively noticeable, limiting, or unstable? Does the NG outperform it’s published numbers?

I see the stall speeds are higher but who is really cruising around the pattern at 60-70 knots or doing steep turns at 85 knots at max weight. This seems dangerous with either engine.

[shorton]

I see the stall speeds are higher but who is really cruising around the pattern at 60-70 knots or doing steep turns at 85 knots at max weight. This seems dangerous with either engine.

All else equal, lower stall speed = safer aircraft. As was mentioned previously, the amount of energy that must be dissipated in a crash/forced landing increases exponentially with speed. So, small increases in speed create large forces on the aircraft and passengers. Greater stall speed means higher speed on takeoff and approach. If control is lost, impact forces will be much greater.

The Lycoming DA40 is the safest single engine piston trainer ever built. The engine technology may have been around a long time, but the engines don’t quit - I’m not sure if that will be the case with the Austro.

Ultimately, who knows what the safety record will prove to be for the 40NG, but I’d bet the farm it won’t beat the Lycoming DA40.

[pietromarx]

It is interesting that the stall speeds are most different (7-11 KIAS or about 11-15% of the speed) at the least bank angle. At higher bank angles, the stall speeds are quite similar (1-3 KIAS or 2-3% of the total speed). Landing straight ahead with a few extra knots isn't much of a big deal IMHO. Try driving on the freeway at 65-75 MPH and see if you find the experiences significantly different.

While CG is certainly a consideration, there are also differences in the wing design (the tips).

[nrenno]

A 7% increase in speed implies in 14% increase in kinetic energy (proportional to the speed square), while 11% implies in 32% increase. This is the extra energy that needs to be dissipated on landing or impact. Since, we don't fly at the stall speed (we typically fly around 10% above it on short final), the energy increase is likely significantly larger.

This is only one of the factors that need to be considered. Handling and the likelihood of stalls at low altitude might be even more important.

When doing a trade study to decide on a new airplane, I consider both quantitative information (e.g., performance, safety record, cost) and qualitative information (e.g., visibility, handling). Frequently sales people focus on intangibles because one of their goals is to maximize their profit, not the value to the buyer.

[Antoine]

Does anyone know of fatal accidents caused by stall/spin in a DA40-180?
I know of two such events in the NG. Discussed on this forum.

And as to this comment:
"who is really cruising around the pattern at 60-70 knots or doing steep turns at 85 knots at max weight. This seems dangerous with either engine."
Think again and imagine what could get you to end up in this situation against your will.
It only needs to happen once.
It happened to me, I admit, and the DA40-180 saved me.

[Rich]

Does anyone know of fatal accidents caused by stall/spin in a DA40-180?
I know of two such events in the NG. Discussed on this forum.

There was one likely stall-spin in a DA40F in 2016 (Utah), and the crash in Peru in 2013 is also a likely stall-spin. That's it in the NTSB database that I've seen, in over 15 years of production. Cirrus' on the other hand, with similar stall speeds to the NG, have had an impressive number (2-4 just last year), despite the chute and its highly-touted wing leading-edge trickery.

[Keith M]

I know I'm just whistling in the wind, but I'm really pleased with extra performance of my new CD-155 engine. It adds nothing to the weight of the old 135hp engine, so the stall speeds haven't changed (same as XLS), but the 3000ft cruise speed at 75% power has increased from 116 kias at 5.6 gph to 129 kias at 6.2 gph. At 95% power it was doing 142 kias, but I forgot to note the fuel consumption. I'm sure the DA40 is a safer aircraft and would be better seller with this engine than the Austro.

[CFIDave]

My understanding is that multiple Russian DA40 NG crashes were caused by students flying in the pattern who accidentally shut off the engine (via "Engine Master" switch) when they only meant to turn the "Fuel Pumps" switch on or off. Austro-engine DA40 NGs require the pilot to turn Fuel Pumps switch to ON before landing, and OFF right after takeoff; on the NG this switch turns on both electric fuel pumps running in parallel in case one pump were to fail.

Toggling the wrong switch would have been a very easy mistake to make, because the two switches are located next to each other on the left hand side of the panel, and both switches are silver toggles that require you to pull out and then up to engage: terrible human engineering IMHO. The result was that students accidentally shut off the engine and stalled the plane while flying in the pattern.

The good news is that newer DA40 NGs now have a big red switch guard covering the Engine Master switch -- identical to the red switch guard covering the backup gauge battery switch on the upper panel of all G1000 DA40s/DA42s. This guard makes it impossible for the pilot to confuse the Engine Master with the Fuel Pumps switch on the NG -- problem solved.