Jaerl wrote:Don't let some of the guys here scare you off, these guys would give Bob Hoover crap.

Bob Hoover escaped from a German POW camp in WWII, stole a Focke Wulf 190, and flew it over to the allied side. A real man would have stolen a Messerschmitt 262!

See what I mean

kevbert wrote:

Jaerl wrote:Don't let some of the guys here scare you off, these guys would give Bob Hoover crap.

Bob Hoover escaped from a German POW camp in WWII, stole a Focke Wulf 190, and flew it over to the allied side. A real man would have stolen a Messerschmitt 262!

Careful, now. There are some folks around here with an underdeveloped sense of appreciation for fine sarcasm.

The serious people are always watching.

I've put some thought into this, and the odd, interesting thing to me is that prior to the STOL kit, raccoon62 could take off by holding the yoke to the rear and the tail did not hit the ground, and after the installation the tail would hit the ground. I couldn't see how the STOL kit would make that happen.

Then, while reading his original post again, I noticed he mentioned vortex generators. I now theorize that the VGs were added at the same time as the STOL kit. The VGs are what are causing the tail to hit now. Prior to the installation of the VGs, there was turbulent airflow coming off of the wings hitting the elevator. Now, it's getting a cleaner airstream, and its effectiveness is increased. Raccoon62, can you confirm that the VG's were installed at the same time as the STOL kit? If that is the case, does everyone agree that the VGs are the explanation for the change in takeoff behavior?

Finally, most people DO consider it appropriate to start your takeoff with the yoke all of the way back if the runway is soft and you've got a nose wheel. Of course, you have to ease the yoke forward as you gain speed. Raccoon62 was pretty vague and terse about the details, but really, the best answer I can see is that he needs to relax the back pressure sooner.

Another thing to consider is that the Sportsman STOL adds 3 sq/ft of wing. It is added to the leading edge. Seems like that alone would lift the forward edge of the wing more making the tail easier to push down? Or in other words, move the center of the cord forward. Who knows.

My 175 had a skid plate over the tail ring. My mechanic told me to take it off because he said he has seen them bend the tail. I guess being 4" long it can put a lot more leverage on the tail ring.

kevbert wrote: Finally, most people DO consider it appropriate to start your takeoff with the yoke all of the way back if the runway is soft and you've got a nose wheel. Of course, you have to ease the yoke forward as you gain speed. Raccoon62 was pretty vague and terse about the details, but really, the best answer I can see is that he needs to relax the back pressure sooner.

Some folks consider grass as soft field. I do not as far as this conversation is concerned. With my plane trimmed neutral, I pull the yoke back about 1/3 and that is about it. Big gopher holes are a different story. I flood irigate so I have few gophers.

Up at Grahm Idaho they have that miserable Townsand ground squirel (excelent target) and they do not make a hole large enough to hurt a Cessna Nose Gear. Now badger holes could be a very different story. Even a 600 x 6 could get lost in one of those.

Tim

Jr.CubBuilder wrote:Here's a hint/suggestion

That Sportsman STOL kit (which I would like to put on my plane one of these days) made your wing fly a little sooner, thus the plane starts to lift sooner and the the tail hits the ground because you are rotating at a slightly slower speed.

This can get a little interesting/dangerous because essentially if you are light enough and/or have enough extra power the wing can fly before the tail has enough airspeed for good control. You can get into a situation in ground effect where the plane is nosing up and you don't have enough airspeed to bring the tail up, this can lead to the stall/splatter scenario. That is essentially what happened to a SuperCub pilot near here when his motor burped on a maximum performance takeoff, he lived but his back was broken.

I know you can drag the tail on a 152 doing exactly what you described, so you aren't the only one who's smacked the tail down

Be careful, you changed the performance characteristics with the STOL kit so think long and hard about unintended consequences before you push you or the plane again.

I completely disagree with your argument. On a "normal" airplane (wing in front, tail in back, as opposed to a canard wing) the center of lift is behind the center of gravity. Therefore, the stabilator/elevator has to provide a down force to keep the tail down, not a lifting force to keep it up. If you don't have enough airspeed for your elevator to be effective, then your tail will rise, not fall (assuming correct center of gravity and that the weight is on the wing as opposed to on the wheels). If you're hitting your tail on the ground in a nose gear airplane with full back elevator, then that is proof that you've got good elevator control. The elevator is effective and being over controlled.

I have a Horton STOL kit on my C172 Taildragger conversion. I started off doing soft field landings and takeoffs with the neteral control force on the elevator which has always worked well for my Piper taildraggers of the past. When I did this in my new (to me) C172 with a tailwheel, I experienced the same kind of issues that were described in the original post. Fortunately my tail is supposed to drag. I have since rolled in some nose down trim for takeoff (especially with any weight in the aft seats or baggage) and managed to finess my takeoffs and landings.

There is lots of good information exchanged in this thread on the basic aerodynamics and damn good advice for keeping it safe. Some good ball busting too.

I would agree with QMDV's post a ways back that a rolling start beats a "stand on the brakes til full power" one. It doesnt' take very long for the engine to develop full power and I think you gain more on the roll.
I haven't flown a 172 with the stol kit, but I have flown 170, and the sportsman with vg's is a great setup. I assume it's a full kit with vg's on the tail too, this will give you the increased tail power, moreso than the 2 1/4 inches of extra lead edge. So, as usual, it's just a case of adjusting your flying habits to suit the plane.

ok, i am not thin skinned so none of the posts are offensive. i hail from KMAL. my strip is about 13 miles east near the wind towers. i have 320 hours. about 300 hours are in this plane. i bought it from my cfi. the stol kit and vg's were added together. i suspected the tail banging was from the aerlions/elevators have more authority from the vg's. i have always taken off with the full power/brakes on. i am to fly tomorrow.shall try a rolling start to see if that matters on the take-off. when i take off from the grass strip, i usually am facing the take-off end of the field. i am at a stop, not moving. i am leary to try a rolling start. in my mind, hey mtv no wise cracks, i cannot see how the plane develops more speed from a slow moving start then full power. i am an avid reader. i read alot of these posts. also alot of books about flying off the pavement. as an aside: my cfi was killed in nov 2009. he hit a mountain south of here. they were 400 feet too low. 2 theories are carbon monoxide or did not reset the altimeter. i only had the standard wing at the time. and was trained by him for fullpower, 20 degrees of flap, stay on the brakes. he thought my airfield was too short for any other lift off. he had about 15,000 hours of time. i land in many of the farmer's fields up here. they all get a charge outta it!thanks for the welcome/advice.coon.

Racoon, if your plane is already sitting stopped at the end of your strip, you should keep doing what you were doing. I think what these guys are saying is if you already have forward momentum as in turning onto the runway or turning around at the end of the runway, use it to your advantage and keep moving. Just punch it as soon as you can to get the plane to full power.

You won't gain anything stopping and then starting out with full power. You will just loose all the runway that it takes to get back to the speed you were at before you stopped.

Sorry about your CFI.

Let me try this in a little more "politically correct"manner--something I'm not always good at:

Go find an experienced instructor. By that, I mean someone who's worked airplanes in confined areas. Someone who has experience with those modifications and your airplane type would also be in order.

I can tell you that holding full nose up elevator till the airplane lifts off is NOT the best STOL approach for a C-172 with those mods, and yes, I've flown that kind of setup. The Sportsman cuff does not like really high deck angles. It won't do anything ugly at very high deck angles, but it won't lift as well, which is what you need it to do. It works largely because it adds a lot of wing area (and the camber changes,of course). Note that I'm talking DECK ANGLE here, not alpha.

If you're banging the tail, there are a couple issues: First, it is entirely possible to damage the tail doing this. It is also possible to jam some things in the tail, causing control problems--not good. Finally, doing so puts the wing at such a high angle of attack that I'm betting it's well above critical AOA while on the ground. Now, you're rolling along, eating up runway, while the wing makes all sorts of aerodynamic drag and darn little lift. Again, not good. Especially on a short runway.

Now, as to whether you should stop, apply brakes, then full power, etc, or do a rolling takeoff: I would almost (always gotta have those weasel words) NEVER stop on an off airport unprepared surface then use full power with brakes applied, due to the potential for prop damage. Even if you have a very narrow strip, and turning around is a bit tight, you still have to turn around and face the takeoff run.

Unless you are turning around, then shutting down, and pushing the airplane BACK further to give you more takeoff area (which would be a holy crap kinda deal) you will still benefit from keeping it rolling as you complete the turn, accelerating away. As Tim said, even if you start the takeoff with 2 kt forward speed, that's 2 kts you don't have to accelerate to. Get the thing configured for takeoff as you back taxi, and as you near completion of your turn to the takeoff heading, come in smoothly with full power and STAY OFF THE BRAKES. It is REALLY easy in these airplanes to ride the brakes a bit without really realizing it. Keep your feet flat on the floor once you start the t/o run, with just the tips of your toes on the bottom of the rudder pedals. I think you'll find that your performance will be better, and you'll really be doing your prop a favor.

Now, as to getting used to the Sportsman/VG combo--I really, really, really strongly suggest getting some dual instruction with someone who has experience there.

Test pilots generally get paid a LOT more money that most of us do. There's a reason for that.

MTV

Nothing PC about it. THAT was an excellent response befitting of a professional educator!

Everyone on here knows that the general aviation world suffers from a lack of qualified flight instructors, and it's not likely to get any better. It is very, very difficult to find an instructor to teach a student what the rudder does, much less finding one with the experience to know what a Sportsman kit on a C172 is for.

I have always appreciated any advise I could pry out of an old timer, regardless if I agree with them or not.

gb

With respect to mtv's last post. I would add, that the rolling turn (J turn) takeoff is best made to the right as power can be added earlier than when turning left as P factor can thus be used to advantage. If turning left, P factor can cause over turning which needs correction which is drag.

Thia has been a GREAT thread with useful discussion. MTV pretty well summed it up, but even I learned smething. Maules comment about turning right is something I never thought of. Makes perfect sense though. So, Raccoon, even if you can't find the mythical CFI that knows your plane and situation, there is enough here to experiment with that you should figure it out. Let us know your conclusions though!!

maules.com wrote:With respect to mtv's last post. I would add, that the rolling turn (J turn) takeoff is best made to the right as power can be added earlier than when turning left as P factor can thus be used to advantage. If turning left, P factor can cause over turning which needs correction which is drag.

Is this advice specific to tricycle gear aircraft (as opposed to taildraggers)?

In a Cessna 170 (with its notoriously-poor tailwheel steering) a turn to the right will require a fair amount of right brake (and the resulting drag) to avoid shooting off into the woods, where a left turn rolling takeoff will require only right rudder to counteract the left-turning forces and straighten out to the takeoff heading.

my strip is 1200 feet long about 40 feet wide. mtv you are spot on about the wing. i am pulling back to hard. it is eating up alot of strip to get ole betsy off. i also think iam too anxious about vastly improving the take-off run. when i just let it come off it does much better. there are no pilots in my area, al least that i know of with stol experience. i come back to the farm from the airport. park the plane do chores and then head out to fly. i cut a couple of trees down at the end of the strip. whew! what a difference that makes! while you guys are throwing pearls to this swine...any thoughts on angle of attack indicators?

raccoon62 wrote:...any thoughts on angle of attack indicators?

Spend your money on gas instead, and learn how to read AOA, lift, and weight transfer through the seat of your pants.

Gump

Jr.CubBuilder wrote:

once&futr_alaskaflyer wrote:

maules.com wrote:With respect to mtv's last post. I would add, that the rolling turn (J turn) takeoff is best made to the right as power can be added earlier than when turning left as P factor can thus be used to advantage. If turning left, P factor can cause over turning which needs correction which is drag.

Is this advice specific to tricycle gear aircraft (as opposed to taildraggers)?

In a Cessna 170 (with its notoriously-poor tailwheel steering) a turn to the right will require a fair amount of right brake (and the resulting drag) to avoid shooting off into the woods, where a left turn rolling takeoff will require only right rudder to counteract the left-turning forces and straighten out to the takeoff heading.

Hmmmmm, I'm gonna go experiment with this. I'm thinking it will be real easy to get to much momentum built up in a left turn on wheels for the rudder to fix when you want to straighten out.

Depends on your equipment...with my little c-85 and big rudder it is no issue. But trying to turn to the right is a pain.

Jeremy is spot on with his comment. The J-turn takeoff is the real deal.

Once and Futur: A Cessna 170 need not be a lame steering machine. Mine steers at least as well as ANY 180 or Cub, and better than most. I worked to modify the steering to improve. This was field approved out of the FAI office. It's pretty much a no brainer. Get in touch if you want more info. IT's not hard, and makes a world of difference.

As to AOA indicators: If you are flying an F/A 18 Super Hornet, they are a great deal. But that airplane doesn't have a big fan out front, pushing air around the fuselage. The F/A 18 AOA system has a sensor on each side of the nose. Every one of these devices intended for little airplanes has ONE sensor, intended to be mounted out on one wing a ways. So, you MAY in fact be measuring AOA accurately, but of only that ONE spot on the span of the wings. There's a lot of span on those wings, and therefore a lot of variability to be had when it comes to AOA.

Look at the "sensor" on the most common of these things intended for light aircraft. Interestingly, it looks almost identical to the AIRSPEED pitot mast installed on a PA-28 Piper Warrior. Which is mounted in about the same location outboard on one wing. So, precisely HOW might these things accurately represent the AVERAGE angle of attack of our wing span, which by the way, is what we really care about?

In fact, we can much more accurately detect proper AOA on most small aircraft by getting a feel for the airplane by experience, as Gump suggests.

Go fly it as much as possible, feel what it's telling you, and learn to FEEL the airplane, and what it's telling you.

MTV