More of my random designs

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Sockmonkey

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For fun I decided to mess around with a small passenger/cargo plane design.
Not just neat looking, it's based on specific traits I wanted to include.


Twin engine redundancy without serious off-axis problems if one fails means a lot of design compromises to make it push-pull or the fiddly bits of a co-axial.
A pair of pullers close together is the next best thing.
That means the fuselage can't protrude ahead of the wing, which shifts the CG back, which means it has to be a tandem wing.
Tandem wings have advantages of their own, so it seemed a better compromise.
Aside from the high lifting capacity it also accommodates clamshell doors at the tail for easy loading.
The aft wing has a single flap to adjust trim to account for load variances.
The front wing has "flapelevons" for takeoff, roll, and climb.
Made the aft wing a high delta for dihedral effect and the additional directional stability, plus big twin rudders.
Engines are a pair of liquid cooled inline sixes.
 

Sockmonkey

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Unique enough that it’s hard not to like it.

Obviously a taildragger though?
Yup. Aside from using the rear of the engine nacelles to house the main gear, it's convenient to have the aft loading door close to the ground.
Oh, forgot to mention the small window in the forward floor of the cockpit for landing visibility.
I think I've covered the bases in that there don't seem to be any dealbreakers AFAIK.
 

ScaleBirdsScott

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Pretty neat, and I like that it was all explained out and seems to make sense. Would it have a single tailwheel, or a pair of tailwheels to either side of a loading door? I don't know what it would be like to control such a beast, but if they were full caster and used differential brake steering up front I guess it'd work?
 

Sockmonkey

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Pretty neat, and I like that it was all explained out and seems to make sense. Would it have a single tailwheel, or a pair of tailwheels to either side of a loading door? I don't know what it would be like to control such a beast, but if they were full caster and used differential brake steering up front I guess it'd work?
I was thinking single tailwheel, but two might be better. It would steer like a standard taildragger.
 

Doggzilla

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Interesting design but it would actually have some stability issues.

The rear wing will stall first and is in the wake of the front wing during stall, making it even worse.

With the CG between the wings and with the rear wing stalled first it would tumble backwards during a stall.
 

Sockmonkey

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Interesting design but it would actually have some stability issues.

The rear wing will stall first and is in the wake of the front wing during stall, making it even worse.

With the CG between the wings and with the rear wing stalled first it would tumble backwards during a stall.
Why would the rear wing stall first? The fore wing is has the higher area loading. Plus the leading edge of the aft wing sweeps back at 55 degrees.
Nice, very Payen-looking design. Is that a civilian version of his model P.321?
Very cool. Came up with it independently, but probably by the same reasoning
 

Doggzilla

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Stall is about the angle. Swept wings stall at lower angles due to lateral flow. Since they are both at very similar angles the rear swept wing will always hit its lower stall angle first.

And having it behind and above causes “deep stalls”. This is why aircraft don’t use T tails very often anymore.
 

bmcj

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Stall is about the angle. Swept wings stall at lower angles due to lateral flow. Since they are both at very similar angles the rear swept wing will always hit its lower stall angle first.

And having it behind and above causes “deep stalls”. This is why aircraft don’t use T tails very often anymore.
Low aspect ratio wings have a higher stall angle, and the high LE sweep of deltas in particular can drive vortex formation above the wing and delay the stall even further. Watch some videos of deltas landing and you will see some ridiculously high nose angles at touchdown. That is one of the reasons the Concorde had a droop nose cone.
 

Doggzilla

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That’s a common belief but not so.

Delta aircraft require high angles of attack to produce the same lift at low speed, that does not give them superior stall angle. If they come in at normal angles the sink rate is unsafe. Basically like landing on an aircraft carrier.

Any other airliner could do the very same thing, but it would be at a much lower airspeed before they required such a high angle of attack.

There is a reason nobody uses Deltas without canards anymore.
 

Sockmonkey

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That’s a common belief but not so.

Delta aircraft require high angles of attack to produce the same lift at low speed, that does not give them superior stall angle. If they come in at normal angles the sink rate is unsafe. Basically like landing on an aircraft carrier.

Any other airliner could do the very same thing, but it would be at a much lower airspeed before they required such a high angle of attack.

There is a reason nobody uses Deltas without canards anymore.
As in canards for improving the airflow over the delta yes?
So are we wanting to switch to a straight rear wing?
 

pictsidhe

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That’s a common belief but not so.

Delta aircraft require high angles of attack to produce the same lift at low speed, that does not give them superior stall angle. If they come in at normal angles the sink rate is unsafe. Basically like landing on an aircraft carrier.

Any other airliner could do the very same thing, but it would be at a much lower airspeed before they required such a high angle of attack.

There is a reason nobody uses Deltas without canards anymore.
Rubbish
 

Doggzilla

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Just because I won’t indulge an unsafe fantasy doesn’t mean I am talking “Rubbish”.

That kind of attitude already got two people killed after they ignored my warnings.

Im going to listen to the chief engineer of the Concorde over random people on the internet.
 

Sockmonkey

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Using a straight rear wing, it should be stall-proof as long as the fore wing is set at a higher AOA and it's not overloaded.
There's also this fellow, but he's not as pretty.
 
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