Three surface Stall Maneuvers

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Evanuel

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Jul 23, 2021
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Hi everyone.

I'm new to the forum but I've got a question that's been nagging at me.

I love the rutan quickie platform and while it's surely outdated, very quirky, and generally not a wonderful plane for anything but cheap range and speed i can't help but love it. It's the looks isnt it?

Anyway i also love aerobatics and one thing that's always dissapointed me about canard and tandem wing aircraft is their inability to perform stall maneuvers

As i see it there are two issues. The first is that they are control limited. The canard or front wing is set at a higher angle of incidence than the main wing so that when you pitch up the front wing will stall before the main wing. It's also more heavily loaded so once that front wing stalls it will pitch back down again. You do not have elevator authority to get the main wing to stall because the front wing stalls first and pitches you down.

The second issue is recovery. Let's say you were able to stall the main wing well that's a deep stall and it's unrecoverable because the front wing, the one that gives you pitch control, is stalled already, so you drop without the ability to recover.

However it would seem to me the only issue here is elevator authority and usability at high angles of attack. So would a three surface design retain elevator authority when the front wing stalls, and be able to continue pitching up to stall the main wing and then obviously be used to recover from the stall.

Could a three surface aircraft give a tandem wing the ability to perform stall maneuvers, or am I missing something fundamental?

Thanks,
Evanuel
 
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Hot Wings

Grumpy Cynic
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I love the rutan quickie platform and while it's surely outdated, Nope very quirky, Agreed, but in a good kind of way and generally not a wonderful plane for anything but cheap range and speed That is what it was designed to do i can't help but love it. It's the looks isnt it? From the cockpit - Yes!
Biased response since one has been my primary aviation project..........for far too long.

I did some X-plane simulations many years ago with a good sized V-tail grafted onto an otherwise stock Quickie. I liked the way X-plane said it should fly but it is more real world experiment than I care to undertake.

Another data point to take a look at is the Durand Mk V. It is a negative stagger biplane with a conventional tail.
 

dog

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Dec 29, 2019
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578
An all flying canard surface such as found on
the wren,or robertson stol aircraft,should spice
up the performance on a three surface tandem
aircraft.
Make the first and third surface operate differencialy.Done right ,control forces will go
up with airspeed,and help to keep it in hand.
And of course this would be all about the looks
first,with no comparisions of two surface aircrafts performance,cost,etc.
 

rv7charlie

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Nov 17, 2014
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Location
Pocahontas MS
The second issue is recovery. Let's say you were able to stall the main wing well that's a deep stall and it's unrecoverable because the front wing, the one that gives you pitch control, is stalled already, so you drop without the ability to recover.
I don't think this is a proper understanding of 'deep stall' in a canard/tandem wing. My understanding is that the reason deep stalls can be unrecoverable is that the main (aft) wing is stalled, and you can't get the canard *to stall*. It's still lifting, holding the nose up and holding the main wing angle up beyond stall AOA. Legend has it (via a magazine article at the time) that during the failed Velocity deep stall test over the Atlantic, the test pilot actually opened the cockpit door during the descent and tried to break the canard's lift by getting his hand out on the canard. Finally gave up and just rode it down into the ocean, since the descent rate was low enough that landing impact wasn't dangerous to him.

Could a three surface aircraft give a tandem wing the ability to perform stall maneuvers, or am I missing something fundamental?
Maybe, but why? Every 3 surface design I've ever seen seems to have been done to enhance safety, which typically means, if not stall-proof, at least spin-proof. Contrary to acro goals.

Most engineers realize that form follows function. It seems to me that trying to make a canard into a hard core acro a/c is pushing it outside its design/function niche for aesthetics instead of functional/engineering reasons.

Of course, there might be some cool maneuver you could manage with 3 surfaces that you can't with 2; I just don't know what it would be.
 
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