Full span flaps effect on NASA LS417-karoliinamod

I changed the LS(1)-417 so that the trailing edge gap is zero (=sharpest achievable) instead of the large gap present in that airfoil (Janne's Mini-Sytky does not have this gap while Panu's Mini-Sytky has). According to simulation with Javafoil, this decreases the drag quite significantly. The airfoil has good Clmax at the same time with the low drag (approaches almost NLF414F).

I calculated that Clmax of 2.88 is possible with this profile with full span flaps with fowler inboard section. 

Quick calculation with aerocalc shows that the following might be theoretically achievable:

AR 9

Clmax 2.88

Wing area 4.6 m2

span 6.4 m

Wing loading 144 kg/m2 29 lbs/sqft

L/D max 22

Stall speed 55 kts

Max level speed 260 kts 480 km/h with Rotax 914 (90 hp required out of 115, max continuous 100 hp->ok)

best glide speed 150 kts

empty weight 366 kg

mtow 666 kg

Idea: Full span flaps

Full span flaps with flapped ailerons:

In board wing has 60% span fowler flaps. Outboard wing, the remaining 40% consists plain flap type flaperons with similar mechanism than used in Mini-Sytky.

deltaClmax_fowler = 0.6 * 1.67 + 0.4 * 0.9 = 1.362

For airfoil with Clmax 1.2 the maximum Clmax on landing configuration is thus 1.32 + 1.362 = 2.68

This allows smaller wing area and higher wing loading to be used without sacrificing takeoff and landing performance too much.

Another variation with single slotted flaps:

deltaClmax_singleslotted = 0.6*1.18 + 0.4*0.9 = 1.06

+1.06 in Clmax still is a very good value and better that would be obtained with full span flaperon (+0.9). For airfoil with Clmax of 1.32 this yields Clmax of 2.37.

This idea has not been tested in practice and is not guaranteed to work.

Effects on aircraft:

Aircraft with 60% span plain flap and Wortman FX 38-153 (no full span high lift device):

Clmax = 1.3 + 0.9*0.6 

deltaClmax = 0.54

Clmax => 1.84

86 hp required for 200 kts cruise

wing loading: 92 kg / m2

wing area: 7.2 m2

stall speed: 55 kts

design cruise: 200 kts

Cdtot = 0.011 (with boundary layer suction)

Same aircraft with full span flaperon and Wortman FX 38-153:

Clmax = 1.3+0.9 =  2.20

Same aircraft parameters:

76 hp required for 200 kts cruise

wing loading: 110 kg / m2

wing area: 6 m2 

Aircraft with full span flaps with slotted inboard section:

Clmax = 1.3 + 1.06 = 2.36 

Same aircraft parameters:

74 hp required for 200 kts cruise

wing loading: 118 kg / m2

wing area: 5.6 m2

Aircraft with full span flaps with fowler inboard section:

Clmax = 1.3 + 1.362 = 2.66

70 hp required for 200 kts cruise

wing area: 5 m2

wing loading: 134 kg / m2

For the most extreme case theoretical savings over usual configuration:

Power = 86-70 = 16 hp (18%)

wing loading: 134-92 = 42 kg/m2 (31%)

wing area: 7.2 m2 - 5 m2 = 2.2 m2 (30%)

Karoliina model 1 iteration 1

Karoliina model 1 concept iteration 1

200 kts with Rotax 914

Specs:
2 places: side by by side staggered seating (co-pilot a bit behind pilot)
Configuration: Pusher with Y-tail.
Engine: Rotax 914 115 hp (100 hp continuous), Propeller: Woodcomp SR3000
Body: 60% laminar flow body.
Body laminarity target: 100% laminar flow with suction.
Landing gear: Trigear, retractable nosegear, Steve Wright noselift. Main gear connected to wing spars at 90 degrees angle.
Wing configuration: Conventional, midwing position
Wing loading: 82 kg/m^2 (16.8 lbs/sqft)
Airfoil: NASA NLF(1)414F.
Flap config: Single slotted flaps with external hinges
AR = 10
L/Dmax = 19.8 at 115 kts
L (wing chord) = 0.8 m
wing area = 8 m^2
wing span = 8 m
Re min (stall) = 1829224
Re cruise = 4217074
Re max cruise = 5586254
empty weight = 366 kg
gross weight = 666 kg
fuel capacity = 140 liters
max cruise speed = 200 kts 370 km/h at 7000 feet
stall speed = 50 kts 92 km/h
approach speed = ~70 kts 130 km/h
drag coefficient target = < 0.016 (total drag). Lower is better. With 100% laminar flow body, a much lower drag coefficient might be possible, this figure is conservative.

Hello

Hello, my name is Karoliina Salminen and the intention of this blog is to follow topics related to light aircraft design. I do have a dream and want to share it with you.