Low aspect ratio sport plane ideas

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cluttonfred

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Koen (nestofdragons) recently shared a few sketches in another thread of an old low aspect ratio concept, below is one of them. As I have mentioned before, I think a low AR approach makes a lot of sense for a light homebuilt one- or two-seat aircraft: lighter structure, compact size for building and storing, and potentially docile low-speed handling, even if it comes at some cost in power required or top speed. There are many prior examples and influences: Arup, Hoffman, Zimmerman, Vought, Hatfield, Rowe, etc. even if none have ever become popular.

So, let me ask our group...what do you think makes sense for a low AR sport plane? I'll add a few criteria just to keep us talking apples to apples: one or two seats, direct-drive VW power (max 80 hp), able to fit (folded or broken down) in a 20' ISO shipping container (say 2.0 m/6' 7" folded width, 2.0 m/6' 7" folded height, 5.5 m/18' 1" folded length) and with a maximum wing span of 5.5 m/18' 1". That gives a maximum theoretical wing area of 30.25 m2 or 325 sq ft which seems like plenty. Designs could be Part 103 (not likely given the engine), European microlight, or U.S. LSA category.

[EDIT: Also, the aspect ratio (span squared/area) must be 2.0 or less.]

Let the games begin!

1643272794182.png
 
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BJC

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This comes close to your criteria. With a larger chord / shorter span, and a different landing gear arrangement, it could meet your suggested dimensions, but no change is necessary to fit in a shipping container. Good for basic aerobatics, too.


BJC

Specifications
Seats:1
Length:16' 5"
Wing Span:20' (Option for 18'9")
Wing Area:84.4 sq. ft. (Option for 78.0 sq. ft.)
Tail Configuration:Conventional
Tail Height (Std Gear):53"
Tail Height (Tri-Gear):71"
Tail Width--with tail tips:77.5"
Total Width w/Wings Folded:94"
Total Height w/Wings Folded:Under 8' with 20' wing span option
Under 7' with 18'9" wing span option
Main Gear Width:62" (with wheel pants)
Air Foil:64-415
Primary Structure:6061 aluminum
Cockpit Width:27 in. More Info
Fuel Capacity:15 US Gal.
Stall Speed (full flaps):45 mph [72.4 km/h]
Stall Speed (clean):50 mph [80.5 km/h]
Max Flap Extended Speed (Vfe):110 mph [177 km/h]
Maneuvering Speed:151 mph [243 km/h]
Never Exceed Speed (Vne):216 mph [349 km/h]
Aerobatic Category80 hp 2180 AeroVee
Performance80 hp 2180 AeroVee
Empty Weight600 lbs. [272.2 kg]
Range (1)535 miles
Cruise Speed @ Sea Level*135 mph
Cruise Speed @ 8000 ft (TAS)155 mph
Power Loading (GW/HP)11.875
T.O. Distance400 ft
Landing Distance500 ft
Service Ceiling (calculated)16,000 ft
Gross Weight - Aerobatic950 lbs [430.9 kg]
Baggage (Max)20 lbs
Useful Load350 lbs
Rate of Climb700-900 fpm
Positive Load Factor+6.0 Gs
Negative Load Factor-3.0 Gs
L/D10:1
CG Limits20-32% Wing Chord
*Note: All Models meet FAA Sport Pilot Regulations at maximum continuous power at Sea Level, as required. Read More...

(1) Conservative, low altitude calculation: 135 mph TAS @ 35.5 mpg. At 8,000' AeroVee powered Onex can acheive 155 mph TAS @ 44.25 mpg.

Specifications subject to change without notice.
 

Hephaestus

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STITS-SA2A.jpg


a modern variant would be cool ;)
 

cluttonfred

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OK, let me add an additional criterion so we can focus on low AR types. The aspect ratio (span squared/area) must be 2.0 or less. Keeping that in mind and the weight and speed requirements for microlight or light sport aircraft, I don't think any of the suggestions have met the criteria so far
 
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Hephaestus

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OK, let me add an additional criterion so we can focus on low AR types. The aspect ratio (span squared/area) must be 2.0 or less. Keeping that in mind and the weight and speed requirements for microlight or light sport aircraft, I don't think any of the suggestions have met the criteria so far
I think you're firmly planting yourself into Arup / little bird / UFO territory with AR 2.0... I wonder if Mr @bwainfan wanted to let some of his PAV options out into the wild, it's pretty well documented on his site (in the nasa article).

I mentioned the stitts S2A because - it could be modified and structurally built in a fairly easy manner to achieve the goal if the major goal is fitting in a sea-container.
 

Vigilant1

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FWIW, the Facetmobile appears to meet all your requirements except:
- VW power (but I think that can be solved)
- Fits in an ISO shipping container. It would need to have the outboard 4' of each "wing" be removable.
(ETA: Ooops, I cross-posted with Hephaestus).
 

cluttonfred

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I've got nothing against more conventional designs and have sketched out lots of folding-wing concepts over the years, I am just interested in what we might come up with when sticking with low AR. The exact number is not important, but it seems like an AR of not much more than 2.0 makes the most sense to explore low AR. The Hatfield Little Bird (at least one incarnation) happens to have an AR of almost exactly 2.0.

25-5.jpg
 

AeroER

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I've got nothing against more conventional designs and have sketched out lots of folding-wing concepts over the years, I am just interested in what we might come up with when sticking with low AR. The exact number is not important, but it seems like an AR of not much more than 2.0 makes the most sense to explore low AR. The Hatfield Little Bird (at least one incarnation) happens to have an AR of almost exactly 2.0.

View attachment 121425

Add a step at the leading edge for clambering onto the wing.

It won't hurt the cosmetics or the drag.

I need to spend time thinking more about what features of an AR<2 aeroplane earns it's way onto the ramp.

The list is empty for now.
 

Hephaestus

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That's the wainfan report I was referring to. Not sure if barnaby ever looked at closer to the part 103 end of the spectrum or not. the fmx4 was rotax 503 powered.

Seems like a downsized facetmobile like option could be theoretically possible...
 

cluttonfred

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WonderousMountain

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I’d probably increase the chord at the tips to reduce the likelihood of tip stall, but it’s very appealing overall.
Ugh, please no,..

Notice how the Flaps are slot gap?
There's your stall delay mechanism.
Increasing tip chord is creating more
wing area to stall, inventing hazards.

My advice would be add dihedral, but
nothing too difficult and deploy using
a differential. Let's not run around to
fix what's still looking good.

Sincerely,
CK LouPai
 

cluttonfred

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In terms of dihedral, you could add more than enough by using a spar that is dead straight across the top and only tapers up from the bottom.

On the stall delay and tips...well, that depends. There were a number of different Piana-Canova designs, only a few of which used Junkers-style external control surfaces. See below:

piana canova designs.jpg

I think the challenge with the PC approach is that it requires central elevators and outboard ailerons, which is probably good for control harmony compared to elevons. The problem is that at low speed, say landing, the upward-deflected elevators reduce the effective incidence of the center of the wing, making it more likely the tips will stall first.

I'd want to explore the stall behavior with models and work my way up to a full-size aircraft to be sure that wasn't going to be an issue, or to mitigate it with washout or slots or slats or vortex generators or some combination to ensure docile handling. If that problem didn't exist, or turned out to be easy to fix, then the P-C layout seems like a great and easy to build solution.
 

cluttonfred

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The Payen AP10 would make the basis for a great LAR sport plane, folding outer wing panels with Mignet hinges.

At only 4.16 m (13' 8") long, I could also see hinging the wing and fuselage to fold upward behind the pilot like Koen's concept sketch at the beginning of this thread. Tricycle gear would be more convenient in that case.

Payen AP.10
From Wikipedia, the free encyclopedia
Specifications
Data from [1]
General characteristics
  • Crew: 1
  • Length: 4.16 m (13 ft 8 in)
  • Wingspan: 4.95 m (16 ft 3 in)
  • Height: 1.86 m (6 ft 1 in)
  • Wing area: 10.00 m2 (107.6 sq ft)
  • Empty weight: 200 kg (441 lb)
  • Gross weight: 340 kg (750 lb)
  • Powerplant: 1 × Train inverted air-cooled in-line piston engine, 30 kW (40 hp)
Performance
  • Maximum speed: 200 km/h (120 mph, 110 kn)
  • Range: 900 km (560 mi, 490 nmi)
  • Service ceiling: 5,000 m (16,000 ft)
  1. ^ "Payen AP.10". Aviafrance.com. Retrieved 8 February 2019.
 

U+fly

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In low aspect ratio flying wings, you have the Boeing 390 /396 with nice proportions and "airplane" look.
I like the aileron design / placement.
 

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