I agree with Cary that keeping it simple is sometimes the better solution. It is hard to maintain a good low ground effect when messing with stuff inside the cockpit.

Thanks for the input guys. Lots of good ideas. Now let me ask this, whats the best way to measure your takeoff roll and climb performance while trying out these techniques? I was thinking about setting up my gopro on the ground, doing several takeoff, and then reviewing the footage.

I agree with Cary that cockpit distractions can be problematic. It can be difficult to manage low ground effect and even missing things laterally when looking for, twisting, or reaching for things.

contactflying wrote:I agree with Cary that cockpit distractions can be problematic. It can be difficult to manage low ground effect and even missing things laterally when looking for, twisting, or reaching for things.

Not a problem for the video game generation.

My $.02 (I have a 172 with Horton STOL kit and electric flaps)

All of this really depends on whether you have manual or electric flaps. A manual flap handle will allow you to feel the effects of how drag and lift react to your inputs and you can adjust accordingly. If you have electric flaps then use none in high density altitude (too slow to react and induces a distraction) and set the flaps to the deflection angle of your aelerons and do what MTV suggested and add some flap at rotation and bleed them off in climb if performance is not a factor.

I miss manual flaps. Its like having another control input and can be used to tighten up a steep turn too. You just need to ensure that you set the friction lock tight on the throttle if you are going to have the flap handle in your hand on takeoff and of course, use an EZ Flap handle for improved ergonomics.

I've spent a lot of time working both Cessna 185s and 206s, the 185 with manual flaps and the 206 with electric flaps. I always hear griping about electric flaps, but I never really felt like they were particularly limiting, and in fact they offer some advantages....like just prior to touch, reach over and pop the flap selector up....much less fussing than dumping manual flaps. Like anything, get in there and WORK the thing some and you get used to it.

Now, then bear in mind that I flew a Beaver for a number of years, and the flaps on that airplane are hydraulic, with a selector switch (up or down) and a hand pump. To change flap setting, you select up or down, then pump the flaps to where you want them. Then, you move the selector back to neutral, which prevents the flaps from moving.

Lots of thrashing around in that machine (amphib floats, and gear was also hydraulic, again with a hand pump to raise/lower gear) but again you get used to it pretty fast.

And, by the way, matching the flaps to the down aileron deflection was how I set flaps on the Beaver for takeoff. Do that on a Cessna, the flaps will wind right close to 20 degrees.

MTV

The International Seaplane Fly-in in Greenville, ME starts 3 weeks from today. During this fly-in there are various contests, spot landing, water bombing, step taxi, bush pilot canoe race and the short take off contest. The pilots that fly in the short take off contest take it very seriously. I have spent a lot of time discussing technique, power vs. weight, flap settings, different float models and modifications with my mechanic who happens to be the head judge of the contests during the fly-in. This will be my first year flying in the contests and I think my plane has the capability to do good in the short take off contest. I will have about 100 hours of flying floats this summer in my plane, quite a bit of that has been operating out of a small lake.

I would like your opinion on flap settings for this short take off contest. Keep in mind that the plane is a 1968 172 with a O-320 with electric flaps on EDO 2000 floats. It is very light as it is and I will pull out all the seats except mine, ditch the survival gear and waders and ropes on shore, and have the minimum 1 hour of fuel on board.

The guy who has taught me the most about flying on floats and skis, my mechanic, has recommended 35 degrees of flaps, get it on step and yard it off as soon as there is any sign of airspeed.

In practicing this I have found that I works but it has to be timed perfectly. If to slow on airspeed and it drags the heels of the floats and it wallows at a high angle of attack for a while before lifting off. Wait one second longer and it is fine. But there is hardly any air speed to work with once in the air and the under powered plane has a hard time building speed with this much flap.

Keep in mind the lake is at 1000' MSL and in September the air is cool and there is usually some wind.

Does this flap setting seem reasonable for a 150 hp 172? The 180/185 drivers pop the flap to the last notch ever time as they pull the yoke back to the stops during this contest. This works for them, they have the HP. I'm in a different category, thankfully. I will be going against 170's, 140's 172's and maybe a maule in the 125-179 HP category.

Maybe it is just a matter of getting a feel for the right airspeed? (The ASI is useless at this slow speed and my stall horn hasn't worked for the past 70 hours or so)

What do you guys think?

I think full flaps in a 172, whether 30 or 40 depending on model, under any circumstances is for landing only. My 2c. 20, maybe with a stock 150 or 160hp engine. I'd be more inclined to use 10, but why not experiment a little before the contest?

Cary

Cary,

For normal operations you are right. For every day flying with a load on floats I will use 15-20 degrees and roll a float.

But I have taken off with 0 flaps and with 40 flaps and every setting in between. I have been practicing but it is difficult to tell how far the take off run is other that with a timer. As I think more about this contest I will probably be conservative use something like 25 degrees. It is not worth wrecking a $50K plane for a $5 dollar trophy.

Come on man, priorities!! Where's your winning spirit?!

"I live my life one take-off at a time. For those 10 seconds or less, nothing else matters."

Go out and practice practice practice.

Levi,

You have precisely described the seaplane short takeoff conundrum: More flaps will get you off the water shorter (to a point), BUT to be effective, your technique has to be near perfect. Botch it just one tiny bit and your takeoff distance will nearly double. Do it perfectly, and it's magic.

For the twenty years I worked seaplanes in interior Alaska, I worked crews in and out of a small, round lake. My loads were always two field biologists and their camp gear, two 10 foot canoes, food, water (lest someone jump in here with the notion of using water filters, i invite you to try drinking northern Alaska swamp water that's been filtered. Whatever is in that filter media has no effect whatever on the taste of that stuff . And, it still gives you the shits . Don't ask how I found that out.) and some miscellaneous field and personal gear.

The lake was about 2500 to 3000 feet across, and surrounded by 50 to 70 foot trees. On one end, there was a small creek, which offered a departure route, assuming no wind or favorable wind. The drill was always two loads to get them in there, simply because of the canoes, and two equal loads to get them out. Bear in mind I also had to carry a good bit of gas to move them 60 or so miles to their next stop, then go 100 miles or so home.

Working that lake with the 185 taught me a lot about working seaplanes, even though I already had a lot of seaplane experience. It's the only LZ that I fairly frequently aborted a takeoff because not everything was going perfect....I'd botched one little thing.

Configuration was always 20 flaps. The rule was a turning or "J-Hook" takeoff....accelerate in one direction, getting the plane on the step, then throttle back and step turn to the opposite direction. As soon as that turn is nearly complete, full power, accelerate, then at just the right moment pull in 30 degrees flap while rolling hard left aileron, with just a touch of right rudder and a smooth pull on the yoke, all at the same time. The flaps came smoothly back to 20 detent right after the liftoff.

If all that was done perfectly, the airplane would break water with the right float, and a second or two later, the left float would break water. Then, lower the nose to accelerate in ground effect, smoothly go to flaps 10. And start the climb over the trees.

This was often done at 90 degree plus temps, though the elevation was low. Nevertheless, DA effects seaplanes FAR more than wheel planes.

The point of this looooong post is that IF you figure out what technique your seaplane wants to optimize takeoff performance, you can do great things with it. BUT, if you screw up one little thing......

As I noted (if you've stuck with me this long) if you're going to roll up onto one float, be sure to use just enough opposite rudder to keep the floats straight in the water. If you don't, those boats will definitely slow you down. That roll/yaw/pull thing has to happen all at once, or it won't work.

But, different floats demand different techniques. That 185 was replaced with a 206 with an IO 550, and Wip 4000 floats. Huge floats, by the way. I had a hard time figuring that thing out....electric flaps, you know . It would get up on step nicely, then accelerate alright, but it was like it was stuck to the water.......

Finally, having tried all the tricks I knew, one day I got it on the step nicely, then stepped pretty hard on the right rudder.....no aileron, mind you. Plane rolled up on the right float, and launched. That technique worked every time. I can only assume that the water hitting the steep bottom of the left hull forced the plane up out of the water.

Whatever...it worked. Spooked at least one check airman using that procedure.

Burn some gas and try a little of everything, and remember, loaded is vastly different than light in seaplanes.

I'd start working takeoffs with about 25 degrees, or a touch more. If you can be precise enough try knocking that flap switch down just a bit after having got it on step with just 20.

Good luck!

MTV

Jeredp wrote: I was thinking about setting up my gopro on the ground, doing several takeoff, and then reviewing the footage.

That is exactly what I did when I was flying 172's since you can get a much better idea what your takeoff roll really is by cross referencing google earth. As I did this I slowly progressed into smaller and smaller strips, then I bought my Savannah and solved all my problems

MTV,

Your description of the J-turn departure exactly matches departing the pond I am based on.

My standard departure goes like this.
The wind is usually SW and the lake is 2300' from one corner to the 75' tall pines on the other end (the rocks keep me at least 100' off the shore). I will taxi out of my cove and idle for about 3 minute, do a run up and then get on step and reduce the throttle for a nice step taxi. I go to the opposite end of the lake and make a gentle step turn. Half way through the turn add 10 degrees of flap and add throttle. Three quarters of the way through the turn go to full power and start to straighten it out. I then add some more flaps and roll the right float, wait a few seconds and roll the other float and its flying. I drop the nose to build speed, bleed off the flaps to 10 degrees and aim for a gap in the pine trees. I favor having speed over altitude when crossing this line of trees as there is another lake on the other side of this tree line. ( Me and another 180 driver will use to pick up gear when we are going to be loaded and it is a hot day)

If I can't make the trees I will enter a climbing turn and try to stay over the lake. This happened one hot day when I miss judged the wind and the plane refused to climb until I got about 90 degree of the way through a turn. That scared the crap out of me. It turned out to be a gusty quartering tail wind it the direction I had departed. Like 3 gusting to 15. So it was just swirling around the lake, with not much indication for direction. I had assumed it was a SW wind because that's what it had been all week.

This is a routine take off. The take off contest at Greenville is a little special, is it our equivalent to the STOL contest at Valdez.

After flying a buddy out to a bachelor party today on a remote lake I experimented with the flap setting during take offs for an hour or so when I got back home. I was nearly empty with 5 gallons in each tank. There was maybe 5-7 knots of wind. With 35 degrees of flap, I could got to full power, get on step and wait until the ASI started to move a little and the pull the yoke back to the stops. It broke the water and didn't settle back on. Maybe a 12-13 second take off run based on my IFR wind-up stop watch. I found, as MTV stated, if you pull to soon or even to slowly and it will drag the heels of the floats and will not fly. I think rotating as quickly as possible to break the water is necessary for the shortest take off run.

I would not do this during a normal take off and I would not do this if it were gusty. I can only do this when it is very very light. There is no aileron authority at the slow speed and it is hanging on the prop. Also i think in this light configuration it will fly by popping it up with abusive yoke movements before it would fly by rolling a float.

As for practice, I will be. I can probably get 30 hours in the next 3 weeks before the fly-in.

Thanks for the advise guys, I will let you know how I place.

-Levi

I played with the ideas a little this morning. My first takeoff was 20* from the start of the roll. I broke ground in about 2 runway lights(400') the 2nd takeoff i 'popped' 20* at rotation. I was early and extended the takeoff run to probly 600*. More to come.....

I played with the ideas a little this morning. My first takeoff was 20* from the start of the roll. I broke ground in about 2 runway lights(400') the 2nd takeoff i 'popped' 20* at rotation. I was early and extended the takeoff run to probly 600*. More to come.....

Levi,

Every airplane (yes, even airplanes of same make and model) is a little different.

I agree that your ailerons aren't very effective at the point you're describing, but don't underestimate what just a little control effectiveness can sometimes do.

Try it all.....you never know.

MTV

Jeredp wrote:I played with the ideas a little this morning. My first takeoff was 20* from the start of the roll. I broke ground in about 2 runway lights(400') the 2nd takeoff i 'popped' 20* at rotation. I was early and extended the takeoff run to probly 600*. More to come.....

Here's an idea to try since you are experimenting. First, figure out your minimum speed and distance to where you can rotate briskly. I don't mean a nose-high-from-the-start soft field type takeoff, I mean a brisk rotation at maybe 38-42 mph. Figure out how far down the runway this takes, using a gopro or someone else marking the rotation and takeoff points.

For the moment, forget about the time and distance between rotation and liftoff.

Then, after you have this point marked on the runway, go back and pop the flaps to 20 degrees after the nose has started coming up at during rotation. Not flaps before rotation, but flaps halfway through rotation. The airplane should leave the ground at this point, eliminating the previous time and distance interval between rotation and liftoff.

Once you have verified that you can reliably do this at the same point down the runway, THEN start the rotation and flap deployment 5 feet sooner than you did previously. This is to see whether a combination of flap deployment during rotation can shave off any more distance. Keep testing this 5 foot sooner rotation-flap maneuver until you achieve the shortest distance under the specific conditions.

I'm guessing this will depend on your particular airplane's condition, how tired the engine is, prop pitch, and many other little things. Your CG will also have a big effect on this rotation (and thus liftoff) point.

20 or more degrees of flap deployment creates a nose-down pitching moment. This makes rotation a little harder, because the tail (and elevator deflection) has to overcome this pitching moment as well as generating the force to raise the nose. (This is part of the reason that setting flaps before takeoff creates more drag and slightly worse takeoff performance). Remember the early 172's like yours and mine have a shorter stabilizer/elevator span to make it even worse.

So raising the nose upward will be easier, meaning it should be able to be done sooner and with less drag, when you don't have flaps deployed. This is why I'm recommending that you start the nose coming up half a second before popping the flaps.

probably doesn't help, but i always pull full flaps in the cub on takeoff, and pull back. It usually pops off the ground and then back up to half, i only have two notches. If i pull to soon, doesn't help, makes the takeoff run longer. So you have to get out there and see what works best for you.

Jeredp wrote:Now let me ask this, whats the best way to measure your takeoff roll and climb performance while trying out these techniques? I was thinking about setting up my gopro on the ground, doing several takeoff, and then reviewing the footage.

I just did this last week testing out a bunch of short field techniques, my setup was an iPhone suctioned to the window recording video over the dash (could also see the airspeed and altitude gauge) along with an ipad recording my gps track with altitude info. At home I imported the gps tracks into google earth, which gave me a 3-d view of each takeoff profile. With this and the video footage and some deducing I was able to get a pretty good idea of how each technique worked.