rcpete347

My Feedback: (251)

Hi all, the problem is to slow your Bobcat jet for landing.
The latest info is to change the alerions to flaps and setting about 1 quarter inch up flaps mixed with 1 eight down elevator,
Havent tried it yet, would like some comments.
Thanks Rcpete

Ollie

Reflexing both ailerons will increase drag and help bleed off excess speed. However, reflex also reduces the maximum coefficient of lift which increases the stall speed. When the stall speed is increased so is the landing speed for a given stall margin. Lowering both ailerons (just like lowering flaps) will increase the maximum lift coefficient available and lower the stalling speed allowing a slower landing speed. As you lower the landing speed, you also lower the aileron control authority and increase adverse yaw. So, make sure that you have excess rudder and aileron control authority at slow speed berfore trying to lower both ailerons. Lower the ailerons in small increments at a safe altitude and check for control authority and tip stall tendencies to see if you can get the desired results without undesirable consequences. If tip stall is a problem you may have to resort to seperate flaps and ailerons.

Johng

My Feedback: (4)

By reflexing the ailerons, tip stall can be avoided. While possibly reducing the local lift coefficient, it can delay the stall of the whole wing to a higher lift and slower speed. It also allows the whole plane to sit at a higher angle of attack, icreasing drag for the approach.

Geistware

My Feedback: (16)

Doesn't the higher angle of attack have to be matched with a higher approach speed or at least more air over the airfoil (higher engine RPM) to prevent stall?

Johng

My Feedback: (4)

No, the reflex does that

rcpete347

My Feedback: (251)

Does reflex mean up ailerons and flaps mean down ailerons
Thanks Rcpete

Ollie

When the ailerons go up the airfoil is reflexed. Reflexing the airfoil reduces the mean camber which lowers the maximum lift coefficient available and decreases the angle of attack at which the reflexed airfoil stalls. The decrease in maximum lift coefficient along the aileron when combined with the unreflexed airfoil of the rest of the wing can only lower the average maximum lift coefficient of the wing. This has the net effect of raising the stalling speed of the wing. The increase in drag of the reflex will slow the plane but not below a higher stalling speed than without reflex. It is for this reason that very, very few full scale planes reflex both ailerons at once. The Minimoa is the only one that comes to mind. When full scale designers want to lower the landing speed, they use flaps and slats to increase the lift coefficient available.

You can't reliably judge the airspeed by just looking at the model. With a radar gun you can only measure the ground speed. It takes special instrumentation to measure the airspeed.

Ed_Moorman

My Feedback: (1)

Here's how they work. I've been using them for years, 3 or 4 anyway. I recall they were first used on fun fly planes. They make spot landings and quick landings easier because they kill the lift on your wing. Since I have started using spoilers, I set all my planes up with them, fun fly, scale or sport.

Set slightly up, start with a quarter inch, they will stop the float many planes have and make touchdown easier to control. You will have to play with the amount for your particular airplane. They work very well on windy days and also very well in cross winds. The plane seems to cut through the wind better and doesn't bounce around as much.

The higher you set the spoilers, the faster the plane will come down. 45 degrees on a fun fly plane and it will drop harrier style or like a rock. You'll probably be using full up elevator also and be controlling descent with power. Work up to this point gradually.

As the spoilers deploy, the nose wants to rotate upward, then as the plane loses speed it will start to descend. If your plane is a little tail heavy, it will tend to stay nose up so you may have to hold some down for a descent.

For normal flying, I set my spoilers so I get a good descent, but still have enough elevator to flare. As you increase the spoiler height, you'll notice you are getting to full back stick on landing. For normal operations, back off a little from this point and fly this setting.

There are three ways to operate spoilers. The first, and this works well for sport flying, is to set a flaperon wing type and mix throttle master and flaps slave. Set the flaps to go up a quarter inch or so with idle throttle, starting at about half throttle. After you arm the switch, when you throttle to idle the spoilers deploy. When you add power for a go-around or touch-and-go, the spoilers retract. I use this set-up on sport planes.

A second method it to put the flaps on a separate switch, like the landing switch, and set them upward the amount you like. You can also dial them up with the flap knob.

A third method is to set the flaperons backwards so you get up flap, spoiler, with up elevator and the reverse, down with down. On some planes, down flaps with down elevator helps waterfalls.

rcpete347

My Feedback: (251)

Hi all I have crashed the same Ohio Extra two times now because the engine quit at the wrong time and the wrong place.When the Extra is flown to slow the left wing stalls( snaps) and it's to late to recover.
Know the Extra is rebuilt again, Question other than loosing a few pounds is their anything I can do to to stop her from snapping.
I would like to see her just drop the nose.
Thanks Rcpete