BeechTalk - BT - FAA Grounds Citation 525s With Tamarack Winglets

Username Protected · **Posted:** 29 May 2019, 18:06

Username Protected wrote:

They are finished. No insurer will touch them with a 10ft pole after the claims for the two crashes are paid out assuming they had any major liability insurance to begin with. I'm willing to bet the issue in the end will be a software flaw just as it was in case of the 737MAX. Maybe they can add some explosive bolts to it. That's the only way I'd get on a jet with this system.

Did I miss something? I am only aware of one 525 that went down, and I thought that the cause was not yet determined.

Username Protected · **Posted:** 30 May 2019, 01:51

Username Protected wrote:

Mike, so if I understand this graph (and I'm not sure I do), the winglets can add about 12% to total lift but the downforce can be up to ~25% of total lift?

If so, any idea about why? It seems like you would only need to cancel out the lifting force of the winglets and nothing more.

Adding the winglets and wing extensions makes some of the stock wing more effective. Indeed, winglets do not, for the most part, generate lift, they simply make the tip of the horizontal wing more effective. This is obvious when you think about the winglet airfoil being vertical. So you have to cancel not only the new lifting area, but also some of the old, to achieve the same spar moment.

Quote:

I can't imagine these devices can predict the wing load ahead of time so they have to react after they've seen the load. I get that the electronics react quickly but doesn't the wing still see the full stress of the load for the short period before the active winglets react?

The natural flexibility of the wing and its inertia gives the load alleviation system some time. You can't break the wing with an instant overload, it has to bend, that is move, to a point it breaks the spar. As long as you can move the load alleviation surface faster than the wing can reach limit bending, you can load alleviate.

But it still has to be fast and powerful to do that.

Quote:

I'm not a materials engineer (I'm a napkin engineer) but it seems the argument here is something like this "we are going to over-stress your wing spar but only for a few micro seconds so the spar won't really notice it".

Over stress is over stress even for a short period of time, but it takes movement of the wing, it has to change shape, for that to break something.

The worst case for Tamarack would be very light fuel load (low wing inertia), high indicated airspeed, and sharp gusts. That control surface has got to be wicked fast.

Which brings up another failure mode, oscillation. It isn't just a single shot overload from a gust, but the control system could go bezerk and drive the wing into flutter. Frankly, I am more worried about that than the overload case.

Mike C.

Username Protected · **Posted:** 30 May 2019, 06:17

Username Protected wrote:

The autopilot could do this same thing with the primary control surfaces but you can overpower the AP while hitting the red button to disconnect it. Atlas doesn't have an easy to reach red button and doesn't have a way to overpower it.

What about a trim runaway, what’s the red button to push? What about a flap runout that goes to landing flap?

It’s just the same as a winglet failure. Slow down and pull the breaker.

Andrew

Username Protected · **Posted:** 30 May 2019, 06:27

Username Protected wrote:

If they do give up, who will pay to develop the fix or the deinstall kit? How long will it take?

It is possible from what I’ve been told, two week process and you can never put them back on again.

Andrew

Username Protected · **Posted:** 30 May 2019, 06:32

Username Protected wrote:

This is from the Tamarack patent showing the negative load required:

Attachment:

winglet-lift-1.png

Do we have a graph of the load the wing can take as opposed to the applied load?

I must be jet lagged still as the wing isn’t taking the negative load, the wingtip extension is.

Andrew

Username Protected · **Posted:** 30 May 2019, 09:57

Username Protected wrote:

The autopilot could do this same thing with the primary control surfaces but you can overpower the AP while hitting the red button to disconnect it. Atlas doesn't have an easy to reach red button and doesn't have a way to overpower it.

What about a trim runaway, what’s the red button to push? What about a flap runout that goes to landing flap?

It’s just the same as a winglet failure. Slow down and pull the breaker.

Andrew

Username Protected · **Posted:** 30 May 2019, 16:59

Username Protected wrote:

Doesn't the red button interrupt the trim motor?

Hi John,

Yeah it does but the trim could be at full nose down if you do that. It’s the only emergency memory item that Flight Safety told me not to follow. Not sure if you’ve done it in the SIM but it’s almost impossible to over power when you disconnect the AP. I just did it again in the SIM a couple of weeks ago.

I’ve been taught:

1) pull the trim breaker.
2) manual trim to remove load
3) AP disconnect.

Super simple and no where near as violent as hitting the red Botton.

Andrew

Username Protected · **Posted:** 30 May 2019, 18:26

Will the A/P not disconnect on its own when you pull the trim breaker?

Username Protected · **Posted:** 31 May 2019, 02:32

Username Protected wrote:

Will the A/P not disconnect on its own when you pull the trim breaker?

Nope it holds still.

Andrew

Username Protected · **Posted:** 31 May 2019, 06:54

Here is a video of a dual asymmetric failure.

https://tamarackaero.com/insights/2019/ ... lure-video

Andrew

Username Protected · **Posted:** 31 May 2019, 07:50

Doesn’t seem like the best response.

https://www.aopa.org/news-and-media/all ... dium=email

Username Protected · **Posted:** 31 May 2019, 08:05

I've spent my aviation life watching people put the most extraordinary useless s**** on otherwise perfectly good airplanes.

If people weren't dying, it would be humorous.

But they are. Very sad.

Jg

Username Protected · **Posted:** 31 May 2019, 10:00

Username Protected wrote:

Here is a video of a dual asymmetric failure.

Lame.

They let if fail for 1/4 second and then depowered it.

"The video clearly shows that this failure condition with centering strips is not severe."

BS.

Now show us what it looks like if you get full asymmetry and you let it go for 3 seconds.

The roll rate was going to be significant if the 1/4 second failure was any indication.

Mike C.

Username Protected · **Posted:** 31 May 2019, 11:12

Username Protected wrote:

Doesn't the red button interrupt the trim motor?

Hi John,

Yeah it does but the trim could be at full nose down if you do that. It’s the only emergency memory item that Flight Safety told me not to follow. Not sure if you’ve done it in the SIM but it’s almost impossible to over power when you disconnect the AP. I just did it again in the SIM a couple of weeks ago.

I’ve been taught:

1) pull the trim breaker.
2) manual trim to remove load
3) AP disconnect.

Super simple and no where near as violent as hitting the red Botton.

Andrew

Username Protected · **Posted:** 31 May 2019, 16:19

Username Protected wrote:

Hey Andrew - thanks! Hope to see you at CJP this fall.

In the runaway trim procedure, do you just look at the trim indicator and trim back to neutral? (I must confess that I don't know where the trim indicator sits in normal cruise).

I’ve already registered so will see you there.

On the trim issue, you can almost feel it on the wheel as you trim it out. You also get the red E on the PFD with an arrow telling you which way to trim, so you can just trim in the direction till that extinguishes.

Andrew