Full flaps. . . .

[acroeric]

What method do you guys use to get in and out short with full flaps. I almost learned the hard way playing around without a back seater at low airspeeds. . . I found that it ran out of elevator well above stall speed and had to add a bit of power to get it back. I have since been flying approaches with power when using full flaps Also- when taking off with full flaps it does get off quick but the airspeed in which it feels like it wants to climb makes me a bit nervous.

BTW- the plane is a 1963 PA-18-160, stock wing, no VG, and it has a Borer prop. The empty weight is around 1150.

[mvivion]

eric,

First, the best angle of climb speed for the Super Cub is 45 mph. The configuration recommended for that performance maneuver is full flaps.

Full flaps and 45 mph in a Cub provides a pretty "interesting" attitude, but that's what will get it over an obstacle if it's tight. Of course, if you've needed that sort of dramatic launch, you probably screwed up in the first place.

Note that that is all Vx--which is purely obstacle clearance performance. That isn't, in my opinion, the best way to get underway on a regular basis. Note that if you experience a powerplant failure at that pitch attitude, the airplane WILL stall before you can get the nose over. If that happens close to the ground, it's going to be a little ugly. So, I demonstrate this at altitude, practice it, do it a few times on takeoff, then tell students to use this technique only when you really really have to get over an obstacle.

As to using full flaps on a "normal" takeoff, I generally don't. If you want to launch really really short, you can practice starting the takeoff run with half flaps, then pulling the flaps to full, airplane fairly level, to get it airborne, then smoothly retract the flaps to half right after takeoff. That technique works, but it takes a good bit of practice before it will shorten your takeoffs much.

As to landing, there shouldn't be any issue landing with full flaps, even empty. What do you mean you almost learned the hard way? I don't understand what you mean by "running out of elevator prior to the stall". If this means you have the stick at the aft stop and the airplane still hasn't stalled, so......? Please explain a bit more explicitly your concern.

Most folks who are landing short are working power against drag to get teh airpalne as slow as possible, and therefore, most very short field landings are accomplished with some power on right up close to or into the touch. REmember, power ON stall speed will always be a bit slower than power OFF stall speed. Distance on landing is primarily a function of how much energy (speed) the plane has remaining when it touches.

MTV

[flynlow]

My short/rough field takeoffs involve pulling both sticks (elevator and flaps) as soon as the tail wants to fly. As soon as airborn I begin forward slowly with the flaps when the airplane feels like it wants to fly.

I don't understand the 'running out of elevator prior to the stall' either.
My 1951 125 Cub doesn't want to stall when light, the elevator is full back and I am still mushing, not a bad thing.

[Luke_theDrifter]

One term that is consistent with Cubs is that they don't really "stall", in the since that they break-over like a Cessna. Most everyone agree's that most Cubs "mush" and will lose altitude.

The simple version of short take off with flaps is as follows....For the shortest take-off, on a flat & smooth surface, from a dead stop;
1) put the whip to the engine up while holding the brakes,
2)release brakes
3) keep the stick in a somewhat nutrual position as you begin to roll
4) feet working the rudders as nessesary
5) when the tail begins to fly...you'll have an indication that this plane is ready to become airborne
6) very shortly after the tail flys, jack-it-off with FULL flaps to break ground
7) raise about 1-3 feet above ground, hold it there
sometimes you can bleed off a little flap at this stage
as you're building speed in ground effect you can hang it on the prop
9) slowly begin bleeding off the flaps
10) this plane should have proper speed for safe flight...short field take off complete

A couple of interesting points. Do NOT set flaps prior to roll, this will actually create drag at the begining portion of the roll, before it creates lift, and will cause you to use more runway.
There are many different aspects to improving the shortfield take-off that include, a rough surface, wind, something on the ground to "jump" that will throw the plane in the air a few moments before its really ready to fly, but you can still hang on the prop while you're building flying speed.
If you can turn, back taxi, right before take off and carry some energy forward..this always helps some, and many things can help. Taking off from a flat-smooth "runway" will always use more room than just about any other surface.

If you have big tires, try laying a 4x4 board across the "runway" at about 75' distance, get a running start for 75 feet and then hit the "jump", as soon as you hit the board...jack it off, hold it in ground effect, and then start bleeding the flaps off.

[cubflier]

One term that is consistent with Cubs is that they don't really "stall", in the since that they break-over like a Cessna. Most everyone agree's that most Cubs "mush" and will lose altitude.

Byron - I know that your are saying but for the sake of any reader that may misconstrue what you have written I add my two cents:

I agree that a cub, especially with vg's will give the impression that you will run out of control surface before making it to critical angle thus mushing toward the earth.

This is an allure that can create the misconception of an extraordinary safety net.

But a cub will stall and it will spin and there are pilots (some of which have a ton of cub time) that unfortunately prove that every year.

Jerry

[acroeric]

Thanks for all the replies. . . In my earlier post I mentioned running out of elevator - what I meant is that when landing with full flaps and the engine at a low power setting I found that the elevator went away before it felt like it should. It felt as if I needed some weight in the baggage area to get the cg aft a bit. It does have the borer prop, heavy starter, generator, and a vaccum system- not the lightest setup on the nose.

[mvivion]

Eric,

This may sound dumb, but first, do a weight AND balance for your plane in the configuration and loading you discuss here.

Second, are you using stabilizer trim to trim off the forces in the approach? Some folks leave in a lot of trim throughout the approach, and this will definitely change the effectiveness of the tail.

Remember, the horizontal stabilzer creates negative lift, so if you are actually "losing" elevator authority, that would mean the tail is coming up on you. You could be out of forward CG or it's possible that the stabilizer trim adjustment isn't set properly.

I agree with Red Baron regarding the notion of Cubs being "stall proof". They are clearly not, and they clearly can stall at inopportune times, with very experienced pilots flying them.

Luke, I don't totally disagree with you on setting the flaps prior to takeoff, though I doubt setting the flaps to half makes an inch of difference in takeoff distance. My reason for setting half flaps from the start is so they're easier to reach for a guy with short arms.

MTV

[BritishCubBloke]

REmember, power ON stall speed will always be a bit slower than power OFF stall speed

Mike,

May I ask why this is? I can see why rudder and elevator authority may be btter into the stall, but why would presence or absence of power alter AoA? I presume that's what we're talking about.

Best,

David

[acroeric]

MTV- the weight and balance (calculated) indicates I am within tolerance but towards the forward end of the range. I just replaced the old heavy starter with a lightweight unit- I plan to re-weigh as we finish the annual to make sure the old numbers are correct. As for trim- I trimmed the plane to fly with a light feel at the desired approach angle and airspeed. . . it just feels heavy on the nose- again. . . when I have a back seater it feels much better which makes me feel it is a CG thing.

When I first started flying it I went up a few mistakes high and really pushed it in each of the configurations ( flaps/ power/ turning/ un-coordinated/ high AOA etc.) to see how it felt as it let go. Overall it was a non-event and it is a really straight forward plane. I am comfortable with spins so I did a few to either side- again it was totally predictable. Maybe I just need to carry a bit more power if I land with full flaps. . . . .

[Lance]

Eric,

My bird is forward in CG, and with me in it (205lb) and nothing else it acts just like yours if I let it get slow. Even worse with lots of fuel on board.

If I am coming in real slow and high it will be sinking pretty good so I blip the trottle, right above the ground, to arrest a bit of sink and let it hit. If you come in flat just ride the throttle in and you will not have that issue.

This is all assuming that you are wanting to come in real slow. If you are coming in with a bit of speed you should have plenty of elevator without the throttle.

Lance

[SuperCub MD]

Carry power with full flaps on the approach, chop the throttle and dump the flaps at touchdown, (or when the mains are within about a foot of the ground and you are over your touchdown point). Hold the stick full back and stand on the brakes as hard as you can to hold the tail up without flipping on the nose.

Dumping the flaps transfers the center of lift forward which means more weight on the tail.

I only use flaps on takeoff when necessary to clear a obstical, get out of deep mud/snow, or honestly, just to show off. Using full flaps at high airspeeds or high power settings will twist them because they are only supported on the inboard ends. It's not that you can't or shouldn't do it, it's just hard on the equipment. It's usually best to hold the plane on the ground running on the mains a little longer to get sufficient speed for safe flight before rotating, especially in strong crosswinds or gusts.

[mvivion]

David,

Simple answer: The propeller thrust keeps the airflow attached over the inboard sections of the wing, where the stall normally propagates initially, and over the tail.

With the inboard section of the wing and the tail "blown", you can drive the airplane to a higher AOA.

Anyone cares to take a more accurate whack at that, have at it.

The Model A-1 Husky, being a part 23 airplane, publishes 43 mph as power off stall speed, and 37 mph as power on stall speed, so the difference can be substantial. Note that these speeds were derived using a calibrated test pitot boom.

MTV

[72A]

Use caution on dumping the flaps on touch down, it is a major change in in your flight configuration at a critical moment of your flight. This will shorten your landing distance by anchoring you to the ground and dumping your lift, but you had better be ready for the sudden change in attitude, and it is a distraction to do this at a critical time.

If you are as slow as you can go on touch down the lift will be down to the point you will not bounce, and the flaps are then just air brakes.

John
72A
Chugiak
AK

[BritishCubBloke]

Thanks, Mike. Makes sense to me.

[flynlow]

The micro VG's kit that includes the VG's for the underside of the horizontal stab helped my Cub with the loss of elevator authority. Carrying a smidge of power also helps a bunch.