200lb Useful Load Increase?

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Rich
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Re: 200lb Useful Load Increase?

Post by Rich »

In the US there has been one DA40 fatal spin accident. I can think of 3 others world-wide. And it has been intentionally spun in certification testing. So it's not impossible. Cirrus did get some kind of special certification consideration in this area due to "stall-resistance" and we know how that's turned out.
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Zepp
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Re: 200lb Useful Load Increase?

Post by Zepp »

Attached is the recent and final ATSB report on a spin accident in Australia in a 2006 DA40 in Sept 2017.
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Re: 200lb Useful Load Increase?

Post by blsewardjr »

Tragic. The ATSB put out a video that shows the crash scene. https://www.youtube.com/watch?v=nXAAbdNRypg In the report the aircraft looks relatively intact, however, the video shows more detail. Even though the cabin is relatively intact, apparently, it went down at 6000fpm, which is not survivable. No fire even though the tanks were breached.
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Re: 200lb Useful Load Increase?

Post by Antoine »

Sobering report Trevor.
Going back to my point, I said it is virtually impossible to spin a DA40-180 unintentionally. And I think this is a fair statement, having about 1'000 hours and a number of interesting "oops" moments in two DA40s .
But it still makes me worry to find out that there are spins even a DA40-180 cannot get out of, even with a seemingly experienced instructor on board - and even with no CG issues.
Poor chap sure looked like he knew what he was doing BUT it seems from the report that local aviation authorities will have to correct a thing or two in their publications that may have contributed.
First time I read that one should apply power BEFORE recovering! I was taught that engine torque is an aggravating factor and you want that out of the way until the aircraft is flying again.

More generally I wonder if this spin recovery practice really belongs in the syllabus.
During my EASA PPL, FAA CPL and IR I was never actually trained for SPIN recovery.
We did plenty of STALLS but no spins. Playing with actual spins sounds similar to the dreaded single engine go-around in a twin.
My friend and instructor killed himself while practicing this and I feel that this is a similar case of risk/return mismatch.
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Re: 200lb Useful Load Increase?

Post by CFIDave »

Almost any aircraft can be induced to spin if you try hard enough: I learned how to spin a Cessna 172 when working towards my initial CFI certification, but it was very reluctant to do so. In contrast, when flying a Decathlon (designed for aerobatics), all it took was a good kick of the rudder while the stall warning horn was blaring and over it went right into a spin...

But these were spin entries from flying straight ahead with predictable stalls. What's more insidious is "accelerated stalls" that come on unexpectedly when turning, since the additional G load increases the stall speed. This (when combined with flying uncoordinated with too much rudder in the direction of the turn) is typically what causes the deadly "base-to-final" spin that's unrecoverable when flying the pattern/circuits. In this situation it MIGHT be possible to stop the spin from fully developing -- by QUICKLY picking up the lowered wing with rudder (not ailerons) and dropping the nose, but I wouldn't count on it.

Once a spin is fully developed, I use the following PARE reminder for recovery:
POWER to idle
AILERONS neutral
opposite RUDDER, and
full-down ELEVATOR to break the stall.

This should work with any aircraft including a DA40, but only if you have sufficient altitude for recovery -- NOT when flying a traffic pattern.
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Re: 200lb Useful Load Increase?

Post by Colin »

I have no doubt that some of the regulations are blunt instruments. I think there is quite a bit of evidence that the MU-2 should not have been certified in whatever manner it was. And I am certain there are times when it is simply a paperwork issue. I wish that DAI had the marketing smarts, engineering prowess and desire to experiment that Antoine has exhibited. We would all be flying better performing planes.

Apparently things are so upside down that the FAA can't certify things themselves and rely on teams *within* the aircraft manufacturers to do their work. Little henhouse guarding by the foxes, I think.

I don't know what would be involved in adding the fork and the carbon-fiber elevator. I wish DAI would do it, because even if it didn't give them a single sale THAT year, it would mark them as a company that was forward-looking and forward-thinking. They would be alone on the frontier.
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Colin
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Re: 200lb Useful Load Increase?

Post by Colin »

I tried but I couldn't get the Icon A5 to enter a spin. It's a strange craft.
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Re: 200lb Useful Load Increase?

Post by Ian Sage »

Colin wrote: Tue Jun 04, 2019 6:15 pm I have no doubt that some of the regulations are blunt instruments. I think there is quite a bit of evidence that the MU-2 should not have been certified in whatever manner it was. And I am certain there are times when it is simply a paperwork issue. I wish that DAI had the marketing smarts, engineering prowess and desire to experiment that Antoine has exhibited. We would all be flying better performing planes.

Apparently things are so upside down that the FAA can't certify things themselves and rely on teams *within* the aircraft manufacturers to do their work. Little henhouse guarding by the foxes, I think.

I don't know what would be involved in adding the fork and the carbon-fiber elevator. I wish DAI would do it, because even if it didn't give them a single sale THAT year, it would mark them as a company that was forward-looking and forward-thinking. They would be alone on the frontier.
Having been through the certification process several times now (admittedly as a smaller entity than DAI) I can assure you that nothing would ever come to market if every test suggested in the initial test plan had to be done. There are some tests like spin and climb cooling that can never and should never be excluded. While they can be time consuming and expensive this is the critical role that is the FAA's essential function in the process.

Many of the tests can be avoided if you have a good relationship with other industry vendors. For instance as part of our supercharger STC we replace the factory starter with a different model Skytech. The FAA is entirely within their rights to require us to do any number of tests to ensure that the starter will function safely costing us both time and money to duplicate tests that Skytech already did themselves . . . or we could call Skytech and ask them if they would be willing to release their test data for whatever specific test the FAA is requesting at that moment.

As you suggested, some tests can be avoided by collecting the correct paperwork. One example would be the FAA requiring load testing of a bracket to ensure it is strong enough. If you want to avoid the test it could be possible to provide material certification that proves the part is far stronger than the load it will carry. Another example would be a test that can already be considered passed by virtue of a more strenuous test being performed without failure.

Last, in my experience there are always tests in the original plan that do not apply to the product being certified. Most likely they are a result of somebody copy/pasting portions of a previous test plan but I would not be surprised if they put a few things in there just to see if you are reading the plan thoroughly. One example from our history is a requirement to measure the back pressure in the exhaust between the cylinder head and the turbo's exhaust turbine. Since we use belt driven superchargers the part they required us to test does not exist. It does however require documented proof of why the test should be removed from the plan so even in these cases there is a cost of time.

I'm sure everybody who has gone through the process has both funny and horror stories. In the end it is a matter of figuring out which fights are worth fighting, which way to fight them and which to just bite the bullet and do in order to get your product to market. Picking these battles carefully has a huge impact on your time to market. Particularly when introducing new concepts.
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