Christian,

 

There must be as many different ways to fly these airplanes as there are different wee Lancairs.  The techniques I use work for me, but there are other pilots that use totally different methods with respect to flap management.  I tend to use distances, altitudes and speeds that would be similar to GPS instrument approaches.  From about 10 NM out I will slow to 160 KIAS merely by reducing power and nearing a safe maneuvering altitude.  Over the next 5 NM the flaps are moved in 2 steps to down about 7 degrees (from full up), level flight is then stabilized at around 120 KIAS.  For the next 3 miles, I descend to about 1100 AGL with power set to 15-17" MAP.  Depending on the type of pattern entry and with about 3 miles to fly (downwind entry or straight in), flaps are brought down another few degrees, gear is extended and speed is stabilized at about 100 KIAS.  Descent is then managed so that when field is made, flaps usually go to full down and power is controlled so that the over the fence speed is also about 85 KIAS.  I am not sure of the other speeds as I am looking outside, but it seems touch down is at about 70 Kts since the round out also reduces speed and throttle reduction finishes it off.  The runway I generally use is 6500 feet, but the exit I use is 2450 feet from the landing end (I see your runway is 2300 feet long) with very little braking.  If there is a good crosswind I will land with less flaps.

 

My flap is marked so that all take offs are at 10 degrees down and lift off is at about 80 KIAS although the stick is pulled back to lighten the load and gain better directional control as 40 knots is passed.  I start every takeoff run with the elevator trimmed to the same neutral position and I think I never could fly off the runway without gradually pulling back on the stick.  Every pre take off configuration is the same so that conditions different from the norm are under pilot control.  For me, the most efficient climb out is at about 135 KIAS for good cooling and a very good climb rate while escaping the airport environment quickly.

 

Since I enter the "pattern" at no more than 120 KIAS, gear extension on a downwind takes the speed down quickly.  I do not fly the killer square pattern - downwind to final is accomplished in a continuous turn so that any adjustment for runway alignment can be made throughout the turn and not as a correction to an already tight 90 turn from base to final.  I do not fly "close in" patterns.

 

My airport is at 700 MSL and I can understand your adjustments for altitude, shear, slope and runway length.  I know several pilots that are happier landing with no more than 30 degrees of flap.

 

I have glider type gap seals on the bottom of the flaps, and both sides of all other control surfaces.  Speeds increased by about 6-8 KIAS.  Rudder control became effective about 5 Kts sooner than before the seals.  It becomes more difficult to go down and slow down at the same time.

 

Scott Krueger

N92EX

 

Scott,

this is very interesting!

Could you write down some more flap positions which you use for take off and landing in different take-off weight configurations.

And also when you arrive in the landing-circuit in cruise speed. How best to slow down to flap speed in the downwind.

Actually when I arrive from cruise, I put the engine to idle pull nose up to reach 120kt drop gear, set flaps to +10 (17 from full reflex) 

and drop nose and put back low power setting. After all this I get my 100kt and turn to base leg. In final I use +20 / +25 and will also land

in this setting. My runway is 700m long and has a 1% down slope and is located in 2200ft alt. If I use more flaps to land the plane won't sit down.

Speed over the fence is 90-85kts because of shear winds just before the runway...

What speeds do you use in short final?

Does it help to stick some gap seals over the hinges of flap and aileron like all the gliders do?

Christian

OE-CCM

Am 16.04.2012 um 14:13 schrieb Sky2high@aol.com:

Ed, Rob, et al,

 

The purpose of reflexed flaps (wing TE) is for reduction of drag at cruise speeds.  After certain minimum speeds, induced drag is lessened by reducing lift through a reflexed TE (also reducing anti lift at the horiz stab).  Parasitic drag in a laminar flow environment may also be reduced by reattaching the airflow at the reflexed flap.  The basic fat wing design helps when the leading edge gets dirty (disrupts laminar flow) because lift is only slightly reduced but draq increases (ice, rain, bugs - see note 1).  This is as opposed to a thin laminar wing which may lose lift when dirty.  The fat wings allows our grocery cart wheels to be stowed within. 

 

When the flap is reflexed, the point of lift moves forward where higher speeds require more nose down trim (less negative AOA at the horiz stab) and lower speeds require a higher angle of attack to achieve adequate lift.  In general, below a max Vf (160 to 140 KIAS), the flaps may be taken out of reflex (to 0 degrees) where the attitude of the airplane can be changed by up to 6 degrees nose down (as measured digitally at the longeron) and this will require substantial nose up trim for level flight while the speed drops (about 15 KIAS) from increased drag.  For this wing, further reflexing beyond -7 has little effect on speed in cruise (Note 2).

 

This form of wing is not unique - reflexed trailing edges are used in all tailless (and non-canard) aircraft.  In such aircraft, changes in CG are compensated for by changing the angle of reflex (changes fwd/aft point of lift).  Remember that the same is true with the 200/300 series wings. (hint: aft CG wallow may be reduced by taking a bit of reflex out of the wing).  Remember also that slow speed operation with flaps fully reflexed requires a high AOA to compensate for the reduction in lift from the reflex.  Be careful out there.

 

Max lift, min drag at 70-100 KIAS is with the flaps at TO position (about +10 degrees down from full reflex).  After about +17 degrees down from full reflex, the flaps seem to merely add drag that is useful in higher than 3 degree descent angles (preservation of kinetic energy) - keeping the speed controlled (below 100 KIAS) at low power settings and also keeping the nose low.

 

Maybe next time I will record AOA digital display data in some of these configurations.

 

Scott Krueger

N92EX

 

Note 1: In an Air Venture x-ctry race, KARR was a turning checkpoint that required I descend over the monitor.  In that descent I ran through a mass of little black bugs (so did others) and my return to level flight as the same race power resulted in speeds 6-7 KIAS less than before the encounter.  Later, I noted that the splattered bugs were very close together (less than a 1/4") and had completely messed up the laminar flow at the leading edge of the wings.  Slow downs have also occurred in flight through rain.

 

Note 2: Certain 320/360 racers experimented with more reflex with the conclusion that there was no significant improvement in speed.

 

 

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