Flap assisted take off

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Re: Flap assisted take off

Postby Vertical » Tue Feb 02, 2021 3:13 pm

I'm no expert, but in my experience the more challenging the conditions or the closer you are to the limitations of the aircraft the more nuanced and critical the control input. There are so many variables that affect decision making and how you interact with the conditions and obstacles -STOL comp on pavement/hillside/riverbar/cliff dive/sand/long grass/deep canyon/crosswind/big rock/off camber etc...They all really require their own unique methodology to optimize performance, safety and execution. Flying is one of those things that's complex enough that you can spend a lifetime working at it. That's one of the best things about it.

In my opinion, being highly proficient at the combination of rotation, flap deployment and retraction (on take-off and landing) should be a fundamental goal of any tailwheel pilot, no matter what kind of flying you do. Why wouldn't you want to have those tools in your tool box even if you never leave the pavement?

To write it off as not by the book, extreme or only for the 1% of highly skilled pilots is a mistake.
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Re: Flap assisted take off

Postby counsellj » Tue Feb 02, 2021 3:25 pm

Vertical wrote:
To write it off as not by the book, extreme or only for the 1% of highly skilled pilots is a mistake.



Exactly!
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Re: Flap assisted take off

Postby daedaluscan » Tue Feb 02, 2021 4:29 pm

Vertical wrote:
In my opinion, being highly proficient at the combination of rotation, flap deployment and retraction (on take-off and landing) should be a fundamental goal of any tailwheel pilot, no matter what kind of flying you do. Why wouldn't you want to have those tools in your tool box even if you never leave the pavement?



I think this is spot on. Took me a long time to be able to use the flaps while doing other things (like keeping straight) but I think it is essential. Being able to dump 40 degrees of flap at the right time will really stick the plane to the pavement. Its a very solid feeling lowering the plane onto the runway.

(Flame suit on for this bit) I also really like my EZ Flap handle. Not only do I not have to look for the flap handle, I do not have to reach for it with a large upper body movement. It is literally right next to the throttle. I use zero flaps for pretty much every takeoff, adding twenty smoothly to lift off almost vertically without pitch change as soon as the airspeed is alive. Like everything with these planes I try to do it smoothly and gently, they really don't like being yarded about, and I believe that gross inputs mess everything up airflow wise for a noticeable moment (especially at low airspeeds) and actually degrade performance.Push forward in ground effect and accelerate. Admittedly this works less well at high DAs, where I tend to simply put in 20 and wait. If I am busy with other things, new passengers etc. I will probably just use 20 and standard book takeoff.

Whether it is quicker off the ground I am not sure. I know its fun. Every takeoff surface is different. Would I use it if I was worried about available length? Absolutely as it is my usual short field method.

YMMV.
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Re: Flap assisted take off

Postby c170b53 » Tue Feb 02, 2021 4:34 pm

I’ll confess I seldom get off the pavement so I’m enjoying following the conversation and points of view.Its enjoyable not having a position oneway or the other but do like trying to follow the reasoning. Other than crosswind ops, most times I don’t think about what I’m doing :oops: :oops: Obviously I’m not flying enough into smaller fields.
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Re: Flap assisted take off

Postby DaveF » Wed Feb 03, 2021 12:55 am

Glad to see this thread take a more constructive tone.

I've used the flap pop technique in other airplanes, but never (yet!) in my 170. Now I'm interested, though. Time to head out to a dirt strip and give it a try. Maybe I'll like it enough to install an EZ Flap. 8O More power to you if you have one and like it. It's your airplane! I'd never judge your choices unless you installed a nosewheel, or Ace Demers Super Tips. :lol:
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Re: Flap assisted take off

Postby Vertical » Wed Feb 03, 2021 1:44 am

For all you pavement pounders..haven’t you ever taken off (or landed) diagonal to the centerline to mitigate a nasty crosswind? Runways get really short in the wrong axis, but having the ability to get off the ground quickly, into ground effect and turned into the wind can be an asset to make the take-off significantly safer. I know some of my scariest ops have been on pavement...It’s so sticky..and there are so many light posts and ditches and rules. Dirt and grass is far more forgiving and (for me) inherently safer.
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Re: Flap assisted take off

Postby Ryan Smith » Wed Feb 03, 2021 4:07 am

DaveF wrote:Glad to see this thread take a more constructive tone.

I've used the flap pop technique in other airplanes, but never (yet!) in my 170. Now I'm interested, though. Time to head out to a dirt strip and give it a try. Maybe I'll like it enough to install an EZ Flap. 8O More power to you if you have one and like it. It's your airplane! I'd never judge your choices unless you installed a nosewheel, or Ace Demers Super Tips. :lol:


:lol: :lol: :lol:
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Re: Flap assisted take off

Postby TFA170 » Wed Feb 03, 2021 4:42 am

There seem to be a few folks who think anything not written in the book is 3D (dumb, dangerous, or different) wrong. In reality, it's nothing more than knowing the aircraft, knowing the situation, truly understanding angle of attack and aerodynamics in a practical sense, and flying to the situation, rather than applying a one-size-fits-all technique. If we operated in an objective and binary world, a nested if/then approach might work well. However, we operate in a subjective and dynamic world and it requires a flexible approach to the situations we are presented.

There is no "set it and forget it" method, technique, or configuration that will be perfect for every takeoff, from every surface, in every condition and every plane. It almost always comes down to that standard aviation answer; it depends.

Ground effect is your friend. Induced drag is greatly reduced, you accelerate quicker than either on the ground or out of ground effect, and you have to really try to push it back onto the ground if the power is in, so it's a safe operating regime when accelerating. In other words, the sooner you get into ground effect and off the ground, be it asphalt, gravel, grass, sand or anything else, the better off you are, the less wear/tear on the plane, and the sooner you can gain speed. Because speed is life - altitude is only life insurance. ;)

As for flying off with flaps deployed and never touching them, that's fine if runway length and/or obstacles aren't a major factor. It works well on asphalt and well tended grass strips of reasonable length. But while I don't quite get into the "rough" with my plane (just yet), I do work on the skills specific to my plane because that's how we get better.

I rarely begin a takeoff with no flaps deployed, simply because as an average height guy with average length arms, reaching for the flaps creates a lot of upper body monkey motion that may translate into less than smooth flying. Consequently, I typically start with Flaps 10, get the tail up as soon as it will fly, from there the plane will come off almost immediately after simply by pulling the flap lever. Now, it will not climb yet, but that's not my objective. My goal is to get the flaps back up/in as I accelerate until I'm ready to climb, at which point, I can, if the situation warrants, pull in the flaps with an aggressive pitch up and it's not unusual to tickle the horn on the odd occasion - a reduction in AoA fixes that.

Vx and Vy are based on steady state climbs. If I have excess speed above Vx, I can use this kinetic energy to "zoom" at a much higher climb rate momentarily while playing the pitch to catch Vx. This stairstep approach is useful in certain situations...not all.

At the end of the day, speed is just an approximation of stall. AoA is all that matters and is far more complex than a single number on an ASI based on real world actual conditions. My advice: learn your plane. Learn the idiosyncrasies of your exact combination, the little errors in your gauges (better yet, don't look at them all that much), what your pre power-on stall mush feels like, what your actual power on stall looks and feels like, and many other things more than just a simple approach to stall profile once every other year on your flight review. Regardless, to say "this works and that doesn't because it's not in the book" is myopic at best.

One of the SOF Truths is: Humans are more important than hardware. What this translates to is, the machine is just a tool - hone the operator, not the tool. Learn your plane. Wear it. Make it an extension of yourself. Then, when you need to use that corner of the envelope, you know what it looks like, it's not foreign, scary, or even dangerous - it's just another capability.
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Re: Flap assisted take off

Postby mmcmillan2 » Wed Feb 03, 2021 1:23 pm

This has been a great read. Thanks for sharing!
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Re: Flap assisted take off

Postby Joe Moilanen » Fri Feb 12, 2021 7:59 pm

Here's a link of me landing at my home strip. It's 650' from the trees to the cliff, so there is barely 500' usable. Unfortunately it is downhill to the trees, wish it was the other way around. I have a Sportsman STOL kit and a 8043 prop. I'll have to get a video of me taking off. My strip is very firm, and I clear the trees by more of a margin grabbing 20 degrees at rotation speed. I've tried both ways several times. I've done it before I installed the STOL kit also, but the STOL kit really helps. My thoughts are that the flaps may be obstructing some of the propulsion from the prop on initial takeoff roll.

https://www.youtube.com/watch?v=3ah8SNS ... e=youtu.be
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Re: Flap assisted take off

Postby GAHorn » Fri Feb 12, 2021 8:20 pm

Joe Moilanen wrote:.... My thoughts are that the flaps may be obstructing some of the propulsion from the prop on initial takeoff roll.

.....


Wouldn’t they also simultaneously be generating lift?

And if this were a concern.... wouldn’t a pusher prop be problematical?
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Re: Flap assisted take off

Postby Joe Moilanen » Fri Feb 12, 2021 8:41 pm

GAHorn wrote:
Joe Moilanen wrote:.... My thoughts are that the flaps may be obstructing some of the propulsion from the prop on initial takeoff roll.

.....


Wouldn’t they also simultaneously be generating lift?

And if this were a concern.... wouldn’t a pusher prop be problematical?

Initially as you start the takeoff roll you need propulsion to gain speed... to create lift, and the quicker you get to rotation speed, the quicker you can start climbing. Just my thoughts, I know what works best for my situation. I would like to see a test where a 170 was held stationary on the ground at full throttle and test the prop velocity directly behind the aircraft at all the different flap settings to see how much thrust is lost due to the flaps blanking out the prop blast. In this sense, I would think that a "pusher" would not be problematic because the flaps would not be in the way of the prop blast? Maybe I show turn my engine around, reverse the rotation and mount it on top of the wings...LOL!

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Re: Flap assisted take off

Postby mmcmillan2 » Fri Feb 12, 2021 8:51 pm

Joe Moilanen wrote:Here's a link of me landing at my home strip. It's 650' from the trees to the cliff, so there is barely 500' usable. Unfortunately it is downhill to the trees, wish it was the other way around. I have a Sportsman STOL kit and a 8043 prop. I'll have to get a video of me taking off. My strip is very firm, and I clear the trees by more of a margin grabbing 20 degrees at rotation speed. I've tried both ways several times. I've done it before I installed the STOL kit also, but the STOL kit really helps. My thoughts are that the flaps may be obstructing some of the propulsion from the prop on initial takeoff roll.

https://www.youtube.com/watch?v=3ah8SNS ... e=youtu.be


Man, Nice video! We’re cousins, checkout my similar paint job:

0A725574-A993-41BD-ABBB-5FCD53EDA473.jpeg
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Re: Flap assisted take off

Postby Joe Moilanen » Fri Feb 12, 2021 11:43 pm

mmcmillan2 wrote:
Joe Moilanen wrote:Here's a link of me landing at my home strip. It's 650' from the trees to the cliff, so there is barely 500' usable. Unfortunately it is downhill to the trees, wish it was the other way around. I have a Sportsman STOL kit and a 8043 prop. I'll have to get a video of me taking off. My strip is very firm, and I clear the trees by more of a margin grabbing 20 degrees at rotation speed. I've tried both ways several times. I've done it before I installed the STOL kit also, but the STOL kit really helps. My thoughts are that the flaps may be obstructing some of the propulsion from the prop on initial takeoff roll.

https://www.youtube.com/watch?v=3ah8SNS ... e=youtu.be


Man, Nice video! We’re cousins, checkout my similar paint job:

0A725574-A993-41BD-ABBB-5FCD53EDA473.jpeg

Yes we are! Nice paint job.
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Re: Flap assisted take off

Postby GAHorn » Fri Feb 12, 2021 11:55 pm

JOe, it is my view that thrust from the engine/prop results in a forward “pull” at the front of the crankshaft.
I “get” that prop-blast might be “felt” at the flaps. This prop-blast would result in one thing as far as flap is concerned: relative wind against the flaps...which would result in Lift and drag.

Since ALL prop-blast is felt by ANY portion of the airframe ...then it is UN-avoidable. But a benefit of that relative wind created by the prop would also be LIFT... over by the flaps as well as the wings. To imagine flap deployment as a detriment to acceleration (and therefore to obtaining flying speed) would be equivalent to seeing the much larger and blunter airframe as being such an impediment. The greater resistance to acceleration (and therefore the generation of lift by the wings) would be the drag caused by rolling-resistance, especially on a rough-field/soft-field situaiton.... in-which the lift simultaneously created by deployed-flaps would reduce said drag. That is why soft-field/rough-field techniques recommend take-off flap deployment on rough/soft fields.

If your suggestion (that deployed flaps inhibited acceleration as compared to retracted flaps) then the Cessna performance charts would not reflect shorter takeoff distances with flaps deployed versus undeployed. :wink:
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