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%)
1 comment:
Some comments:
1) If you want to have twin engine, you maybe have to increase the empty weight factor. Remember that all engine parts, supporting structures, fuel lines, propellers, gear boxes are doubled and that will add weight.
2) The second funny fact is that twin engines have more accidents than single engines. Even if they are better against engine failures.
(Must be the more complex handling?)
3) I have chosen a different approach: add parachutes or similar devices and you can live with the single engine concept. The fatalities happen mostly flying high and there you might as well use the parachutes, since there is more time.
4) Yes, sure carbon fiber adds less weight. But at least I have very little experience with it. It needs vacum bagging and everything.. ?
5) I agree with the idea to use high lift devices and higher wing loading. After all any plane is primaly made for flying and the take off and landing situations are only transition phases. So the wing should be designed primaly for flying. I would first design the plane for flying and then add the landing gears and high lift devices and what ever additional it needs.
***
I have a similar twin propeller design, but I use there twin propellers with single engine and transmissions.
Lately I have consentrated on the strucutures mostly (I have made some styrox models of the structures and tested their strength just to be able to understand where the loads will be and how to handle them). I have some nice FEA programs available, which should be able to calculate laminates also, but I need time to learn how to use them to do that.
Janne.
Post a Comment