DA40 vs. Cirrus SR20

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pietromarx
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Re: DA40 vs. Cirrus SR20

Post by pietromarx »

I wrote a lengthy reply yesterday on the whole Cirrus spin issue and then decided to delete it. I'll just put in an abbreviated one.

As an engineer, it simply makes no sense to say that the Cirrus was designed to avoid stalls and spins with a parachute. The chute was a regulatory fail on the part of the FAA. Cirrus decided to go for a shortcut in the original certification by saying that the chute would solve the issue of spins and both Cirrus and the FAA ignored the fact that pulling the chute comes *after* the spin. The chute shortcut resulted in a new airplane having a safety record equal to an airplane designed in the 1940s.

Saying that the parachute solves the issue of spins is like saying that seatbelts and airbags solve the issue of icy roads. Having spent a career in highly regulated industries mostly in private, but also in government, and also in aviation, the FAA simply made a mistake in not requiring Cirrus to demonstrate and provide spin recovery in lieu of the parachute.

Cirrus is now doing what they can by educating pilots as they can't / won't go back and fix the spin / chute issue. Diamond simply made a safer plane to begin with. The two planes, certified at the same time under the same regime, had vastly different safety records (and insurance rates).

The easiest way to know is to simply ask your insurance agent what the rates will be. When I've checked over the years, I have found that I could get $2M smooth on a DA40 for less than my automobile insurance. They wanted 4x for me on the Cirrus, but maybe it has come down.

They're both nice airplanes and the customer service (other than software) is basically the same. Diamond and Cirrus have always been responsive to sending airplane parts, being able to solve technical issues, etc. They differ in how they handle software, but are both dependent upon Garmin for almost everything.

The Diamond is a far more forgiving aerodynamic design than the Cirrus. I doubt that anyone would argue with this and the safety record is clear. It may not be as comfortable, but it is more fun ... and forgiving.
Last edited by pietromarx on Sun Feb 02, 2020 3:32 am, edited 2 times in total.
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Re: DA40 vs. Cirrus SR20

Post by Boatguy »

mbitran wrote: Sat Feb 01, 2020 11:05 pmHas Diamond been responsive to all of the customer concerns? It seems unbelievable to me that a company that is in the business of selling airplanes would allow such poor customer service to damage their reputation and product saleability.
Diamond has taken the first step to being responsive which is to agree to meet with owners and discuss the agenda posted in a separate thread. Scott McFadzean confirmed receipt of the agenda and did not push back on any of the items. But the proof is in the execution. We'll keep an open mind and see if Diamond follows up on the meetings with changes in policy and execution of the new policies.

I could not agree more that the current situation of some great planes and poor support is a tragic situation that is squandering the excellent engineering.
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Rich
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Re: DA40 vs. Cirrus SR20

Post by Rich »

TimS wrote: Sun Feb 02, 2020 3:11 am No idea where you get the idea that stall/spin is a major contributor to Cirrus accidents.
Seriously? By looking at the NTSB accident database. Start with the very first SR22 fatal accident and go from there.
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Re: DA40 vs. Cirrus SR20

Post by TimS »

pietromarx wrote: Sun Feb 02, 2020 3:24 am I wrote a lengthy reply yesterday on the whole Cirrus spin issue and then decided to delete it. I'll just put in an abbreviated one.

As an engineer, it simply makes no sense to say that the Cirrus was designed to avoid stalls and spins with a parachute.
Ugh, not sure why I am bothering. But here goes.
The FAA long ago determined that most spins occur in proximity to the ground; e.g. in the pattern. The result was a change in FAA mentality and offered an alternative path to certification. The alternative path is spin resistance; note not spin proof; instead of spin recovery. With less than 3% of spins proving to be recoverable, the FAA made the correct choice I believe to make it better to resist the spin than try and recover from it.

Cirrus and Columbia were the first two companies to take advantage of R&D by NASA on how to build a wing which offered significant resistance to a deep stall. Cirrus continues to follow this model today.

The most significant feature for the passive spin resistance is to have the wing root stall before the wing tips where the ailerons offer control. This is usually accomplished by wing twist or wing washout. This twist usually only gets a couple of degrees at most. In the case of Cirrus the change is much closer to 5 degrees (if memory serves); which is almost three to five times times the level you see in other most other planes. The advantage of this system is that it is significantly harder to get the plane into a spin; the disadvantage is when it enters a spin it is significantly harder to get out of it. For example in left spin, the left wing is stalled, the right inner section might be stalled and the right outer section flying. This places the leverage point of the rudder further away from the center of lift. By having the center of lift farther out on the wing, the amount of leverage required is much higher.

If you want more details, here is a piece by Cirrus: http://whycirrus.com/engineering/stall-spin.aspx

Tim
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Re: DA40 vs. Cirrus SR20

Post by TimS »

Rich wrote: Sun Feb 02, 2020 3:32 am
TimS wrote: Sun Feb 02, 2020 3:11 am No idea where you get the idea that stall/spin is a major contributor to Cirrus accidents.
Seriously? By looking at the NTSB accident database. Start with the very first SR22 fatal accident and go from there.
Actually I have many times. Beyond looking at one accident, if you want to make such an accusation get some stats and go through the list. It is not many, only about 4 pages in NTSB, and among the ten random ones I picked, spin, stall/spin or flat spin was three times total. The rest were "spinner". :)

Spin prevention is NOT part of the training in the Cirrus Approach; it is only a by product of the philosophy of having a stable approach. Having taken the course multiple times with different teachers, I can affirm this point. If spins were such an issue, then you would not have see the accident rate for Cirrus decrease so much over the past few years with the "Cirrus Approach".

Tim
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Re: DA40 vs. Cirrus SR20

Post by Rich »

TimS wrote: Sun Feb 02, 2020 1:54 pm
Rich wrote: Sun Feb 02, 2020 3:32 am
TimS wrote: Sun Feb 02, 2020 3:11 am No idea where you get the idea that stall/spin is a major contributor to Cirrus accidents.
Seriously? By looking at the NTSB accident database. Start with the very first SR22 fatal accident and go from there.
Actually I have many times. Beyond looking at one accident, if you want to make such an accusation get some stats and go through the list. It is not many, only about 4 pages in NTSB, and among the ten random ones I picked, spin, stall/spin or flat spin was three times total. The rest were "spinner". :)


Tim
Sounds like 30% to me. And I have been through a great number of them. This 30% sounds about right. So 30% isn't a major contributor in a plane that touts spin-resistance?, OK.
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Re: DA40 vs. Cirrus SR20

Post by Lou »

Listen to the audio of that poor woman who tried to land her SR-20 (I think in Houston) a couple of years ago. She was flustered because of strong convection and sadly dropped out of the sky. There could not be a clearer example for me of why I do not agree with the Cirrus training and flying approach.

Flying a GA airplane like a jet is fine when conditions are predictable, but this poor pilot did not have the skills to handle sudden strong convection in short final. So she kept trying to make a “Cirrus style” approach to different runways while ATC patiently worked with her. But the correct and safe response to those conditions is to handle the airplane differently. In our Diamonds with full flaps you can (and we probably all have) forward slip and drop like a stone safely until a few feet off the runway. We can do that because there is no one correct approach for our aircraft - we can change it up and fly differently for different conditions. The forgiving airframe does not mean it’s for dummies, it means a pilot has more options.

My aeronautical knowledge comes from building, flying and crashing models since the age of 10, so it’s not very sophisticated. But here is what I learned, for what it is worth. Low wind loading from long, high aspect ratio wings and balanced controls with plenty of authority from a generous tail moment yields an airplane that flies itself and recovers easily. High wing loading, short tail moment and aft C of G yields a fast but unstable airplane.

Cirrus is a nice airplane and I would be lying if I said I didn’t sometimes think about it, but for me safety is the clincher. I don’t want my hobby to be a potential catastrophe.
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Re: DA40 vs. Cirrus SR20

Post by Rich »

There is a stall mode that I used to regularly teach in all sorts of aircraft. It was called a "departure stall". This is a misnomer, as it really is a "missed approach" stall. Full flaps, gear down, full power, pull into a stall. It's the most wicked in any given plane. And we typically did it with CG not anywhere near the aft limit (two guys in the plane). In an M35 Bonanza, the behavior is truly extreme.

I've never actually done this stall in the DA40. I've started to, but the nose attitude became really extreme and I couldn't see ahead, so I abandoned it. That said, the potential is there to be kind of nasty in my plane. With the Powerflow I have more available HP (ergo p-factor) than the original design and still have the original (small) rudder. In any case, it's an extreme exercise to get my plane, at least into this condition.

But I've had to do three missed approaches in this configuration (full flap climb out) that I can recall - from within the flare - without any untoward incident. One was some weird wind condition I still don't fully understand, the other two are rightfully classified as using ones superior skill to make up for a lack of judgement. I operate out of an uncontrolled field these days and often sharing the pattern with low-time private trainees with limited English language skills. One must be flexible in dealing with the condition at hand. My plane is a good partner in these exercises.
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Re: DA40 vs. Cirrus SR20

Post by Rich »

BTW, there are 103 entries in 11 pages of Cirrus US fatal accidents in the NTSB query, not 4. A handful are not actually Cirrus Design, but most are, for a total of 98 fatal accidents. One can not use aircraft model as a query filter in this database, only "make". I've seen the same mistake with DA40 inquiries.
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Re: DA40 vs. Cirrus SR20

Post by pietromarx »

TimS wrote: Sun Feb 02, 2020 1:41 pm
pietromarx wrote: Sun Feb 02, 2020 3:24 am I wrote a lengthy reply yesterday on the whole Cirrus spin issue and then decided to delete it. I'll just put in an abbreviated one.

As an engineer, it simply makes no sense to say that the Cirrus was designed to avoid stalls and spins with a parachute.

Ugh, not sure why I am bothering. But here goes.
Your comments started this. Perhaps don't bother spreading manufacturer's revisionist marketing in the future... ?

TimS wrote: Sun Feb 02, 2020 1:41 pm The FAA long ago determined that most spins occur in proximity to the ground; e.g. in the pattern. The result was a change in FAA mentality and offered an alternative path to certification. The alternative path is spin resistance; note not spin proof; instead of spin recovery. With less than 3% of spins proving to be recoverable, the FAA made the correct choice I believe to make it better to resist the spin than try and recover from it.
The Cirrus is not particularly resistant to spins and, when it does go into a spin, it is abrupt and unrecoverable. Further, it is MORE of an argument against the parachute to solve the issue of spins. They require ALTITUDE to work, something manifestly not available "in proximity to the ground."

What planet produces the statistic that only 3% of spins are recoverable? I guess I and many others are incredibly lucky ... or your stat is another marketing spin? I guess so since you provided a link to ... Cirrus?!
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