To the 170/172 guys, what are you using for degrees and procedure when taking off with flaps. I have always "popped" 10* at rotation but I know the book says 0* for short-field. My home airport is 1800' with 50' obstacles at about 2000'. I used my method of 10* the other night with my family on board. It was 85* and a little over 3,000' D.A. I was off in probably 2/3 of the runway length with room to spare over the trees, but it got me thinking about the best practice in a short field/high D.A. Situation. I have a friend that cut his teeth flying in papua new guinea years ago and he swears that 20* in any cessna high-wing is your best configuration.Thoughts???

20 degrees in any high wing Cessna I ever met is pretty much ideal. If you have manual flaps, you can push the button on the flap lever, pull in almost 30 degrees to get the plane up into ground effect, then ease the lever back down to 20 for initial climb.

I've flown them all, up to the 210, and most on floats, where takeoff can be a real challenge, and that technique has always worked well.

If you're going to pull on more than 20 to rotate, though, you need to practice that procedure somewhere on a big runway till you get the hang of it.....botch it just a little on the timing and you'll lengthen, not shorten the takeoff. You need to practice it, preferably with a competent instructor, till you're really good with it.

But, just using 20 flaps from the start of the roll will get you 90 + percent of that anyway! and no monkey motion.

MTV

Don't know why your checklist says "0" flaps for short field. As I recall, Cessna 100 Series is 0-20 degrees normal, and 20 degrees flaps short field.

Gump

mtv wrote:20 degrees in any high wing Cessna I ever met is pretty much ideal.
...
But, just using 20 flaps from the start of the roll will get you 90 + percent of that anyway! and no monkey motion.

MTV

Yep. Although to add to MTV's point, if you want to pop them on, start with 10 degrees and pull 20 when the time is right. It's not that much drag to start the roll and having 10 degrees already in makes the handle much easier to reach when looking out the windshield.

I've never bought that a few degrees plus or minus early in the takeoff run really creates that much drag. There may be some minor benefit.....maybe, but it prolly isn't due to drag reduction.

In any case, just setting 20 is easy and reduces the opportunity for error later.

Maybe

MTV

I agree with MTV and ZZZ. Set twenty and forget it. May pull more flap early to get off a high drag surface.

I use 10 normally and 20 for soft rough strips, I flew a stock engined 170b that had no 10 notch and found 20 to draggy when heavy you were better off with none.

On my 172m I just set the flaps to match the aileron droop. This gets me light on the running gear quickly on the rough stuff. My standard take off is:
- set the flaps to the ailerons
- full power and yoke back to get the nose light
- mains usually lift off about 40/45 mph with my standard weight
- lower the nose to keep the wheels about 1' above the ground
- as the speed builds I bleed off the flaps slowly
-in ground effect the speed builds quick and at 80 mph I start my serious climb
This gives me the best take offs for what I am doing on the gravel bars.
If I have trees out front I just leave the flaps in and climb at 65 mph till I clear the trees then lower the nose .
On hard surface no flaps give me the best results.

A lot of it depends on how much power you have, versus how lightly or heavily loaded you are, as well as the conditions. The more favorable situation you have, the less the flap setting/usage matters to takeoff performance. Even with 145HP, if you are lightly loaded and have reasonable density altitude, then not much is really critical. When you have your family on board, and it's high DA, then maximizing the benefit of the flaps starts to matter more.

BCP member 182 STOL Driver mentioned to me once that he hear someone at the factory did a proper flight test and found that something like 14 degrees flap deflection gave the best L/D on climbout. I have no idea if this is correct or not.

A large percentage of the Cessna owners I've spoken to at the Alaska Airmen's show indicated that popping 20 degrees just as you rotate, then easing the flaps off very slowly as you accelerate from best angle to best rate, is the preferred method used by experienced pilots out in real-world conditions.

But MTV is absolutely right, you want to eliminate the monkey motion. Leaning back and forth during takeoff like a chimpanzee reaching for a banana on the floor, sticking your face into the panel when you're supposed to be looking where you're going, bumping your chest into the control yoke... definitely do whatever it takes to cut out all that monkey motion

170-172 Flaps

This is one of those rare instances where I vary somewhat from MTV.

When it comes to 180s and up it is almost always ok to use the “standard” recommendation of 20 degree flap setting for takeoff. For those with lectric flaps you can lower the flaps close to full aileron deflection.

The question of flap use on take-off in a (assumed stock 145 hp) 170-172 is not as simple as most like to make it out to be. As with most flying situations there are many variables.

The main variables are; People load, fuel load, Temperature, Altitude, thus DENSITY altitude, (the real killer) the planes general rigging conditions, and the engine hours / fatigue, as well as the pilots currency with the required light fingered - finesse skills.

If you take a look at section V, page 36, of a 170 owners manual you will see a blacked out section of the chart. This blacked out section is a warning that the use of any flaps at these combinations of altitude and temperature is not recommended because there is no longer enough horsepower to overcome the induced drag of adding ANY flaps.

In the older 180 manuals they make it look like you can always use twenty degrees for take off, but look carefully at how the temperature drops from sixty degrees at sea level to freezing at 7,000 feet. Hmm looks like the implication is that you may not want to use the full twenty degrees ALL the time.

For those of us who have flown regularly in the Idaho backcountry we are well aware that there are runways at the 7,000 plus altitude to start with before adding in TEMP, slope, winds, surface condition, etc. So – according to the 180 chart they recommend flaps only at zero degrees temperature at 7,000 feet. Now that is 7,000 feet at standard temperature, not 7,000 feet at 70 degrees of temperature.

Now I am willing to assume that these numbers are for a new plane, with a new engine, and an old, or at least professional, test pilot with the plane loaded to gross weigh and at either sea level or the field level of Kansas on a nominal temperature day. My implication is that if you are by yourself, minimal load, minimal fuel for a breakfast run in a stock 170-172 then maybe 10 degrees may have a benefit. Take the time to test it empirically, several times at several temperatures, then load it up and run the tests again.

Note: I have seen the ten-degree notch added to the earlier models 170s.

My last plane was a 170B with a 180 hp conversion and an MT prop, and a utility interior. Most of the early, and or cool day, take-offs were done with the “standard” twenty degrees of flaps. However we ran some tests on hot days up to 80 degrees and ten degrees of flaps worked best. So there really is a sliding scale of how much flaps are the best to use. Experience is required more than the opinions of others. Test it empirically until you KNOW what you and yours will do.

My personal flap habit, even at civilian airports, is to set them to ten degrees after run-up and before departure. If the wind is relatively quiet I always re-set them to twenty degrees and always practice a short field take-off with a slight off-set to the side away from the wind just in case the fan quits I am already set up to execute a practiced “canyon turn” into the wind and back towards the runway. I have practiced enough to know that I can easily make it back from 600 feet with room to spare, BUT-- the plane is already configured in anticipations of the shit hitting the fan.

I did my COM ASEL in a 172 retrac. The book said that although take off distances were shorter with flaps applied during the run (electric flaps), the additional drag increased the 50' obstacle distance so short field settings were flaps 0*

I did exactly what the book said since it simplified the checkride.

Jeredp,

Don't remember the year model of your 172 but since your avatar shows an earlier straight tail it should to be similar to mine, a '60 model, albiet mine is a swept tail. Ironically I was just out doing a little short field practice last night and since I hadn't flown the 172 in nearly a month I was rereading my Operaters Manual and mine states 10* flaps for short field. I use either 10* or 20* depending on the situation. My practice though is generally with the above mentioned 20*.
I have tried the 'yank' procedure and while it helps a little, I am of the set it and forget it camp. Other issues make it difficult to do the 'monkey chasing a banana' business that EZ talks about. Take offs and landing for me are busy enough that I like to have 1,000% of my attention on the task at hand and any other hand/feet movement that is not absolutley neccessary, is avioded.

I'll throw my hat in the, it depends ring.
If you have enough power 20 degrease works way better than 10, but a stock 145 horse with a load and your rate of climb is substantially hurt with any flaps.

The flaps will hurt climb out of ground effect, but in ground effect, you're still at an advantage with best L/D flaps to get off the runway.

Gump

GumpAir wrote:The flaps will hurt climb out of ground effect, but in ground effect, you're still at an advantage with best L/D flaps to get off the runway.

Gump

Yes. Use a healthy flap input to break ground, reducing the drag/friction if the tires rolling over the surface. Then build airspeed and start milking them off to clean up for climb out. There's a lift penalty initially when doing that but again... depends. ...as in, you'll probably need Depends when you shit your pants doing this on a hot day in a 172.

I agree with everyone that flaps help get us off the surface quickly. I also agree with 175 Magnum that low ground effect is the source of greater extra kinetic energy on takeoff than flaps.

I totally agree that everyone should try all combinations available in their own airplane in a safe (as in long runway) environment, then use what works best for them.

I've done some flying at relatively high DA, but I've also done a lot of flying of low powered airplanes on floats, which is a very good test of technique. A good bit of that was at higher than standard temps, by the way. Some folks don't realize that Fort Yukon, AK sometimes hits 100 degrees in summer .

Put a stock engine 170 on EDO 2000 floats (which are too small for the airplane, limiting LEGAL g/w) and load it up to "purt-near gross" Alaska style for a little flight to the cabin. Air temp at FAI is 85 degrees, but hey--field elevation is only 434 feet msl.

Now, if you DON'T use 20 degrees of flap deflection in that situation, you will not get airborne off that 5400 foot long float pond.

Float operations are a great test of technique, because there is buckets more drag to overcome to accelerate to flying speed, and anything you can do to lower that speed at which the airplane will fly, like lowering flaps ( the manufacturers all seem to agree that flap deflection lowers stall speed, and Cessna says 20 flaps lowers stall speed more than 10 degrees, which is true at all altitudes, near as I can tell) will get you off the water sooner.

I believed that the initial question had to do with takeoff, not climb. What you do with flaps after takeoff is a different story altogether, particularly at high DA and with obstacles.

Also, bear in mind that everything most manufacturers recommend in their operating procedures are pretty simple procedures, designed for the "average pilot". I doubt you'll find cranking in 30 flaps during takeoff in any Cessna POH, but in fact it's a common and well proven technique in a heavily loaded seaplane.

BUT, that technique takes a good bit of practice, and if you botch it, your takeoff run gets a lot longer.....not something a manufacturer is going to put in print as a recommendation, generally.

So, just because the POH says this is the best procedure doesn't NECESSARILY imply that there may not be better techniques out there.....maybe

Which also supports the assertion that you should see what works best in your airplane, with your skill set. And that is best done with a competent instructor who is well experienced in your airplane type.

MTV

MTV, I completely agree with you on situational best technique vs blanket techniques (POH).

I just mentioned that because it offered the info of why the POH called for 0* instead of the 10-20* most other Cessnas seem to call for.

I have rarely used 20 for take off on my 180hp/CS prop 63 P172D, but I have often used 10, mostly on softer fields. Back 11 years ago when I first got the airplane, I tried 20 and didn't like it--took too much right rudder to keep it straight on climb out.

But when I took my seaplane training in Seattle last month, the airplane was almost identical to mine, and the normal take off scenario called for 20 flaps until the floats lifted off, reduce to 10 flaps right away, then milk off the 10 flaps to zero on climb out. In fact, the one time I forgot the flaps (during my check ride of all places), the floats wouldn't come unglued till I noticed the flaps were at zero and yanked them to 20. Of course, that's at sea level, and even at 85 F, that's only 1600' DA, whereas I'm flying out of typically higher than 7500' DA up to around 10,000' DA.

So when I got home, just for the heckuvit I tried the seaplane take off, and it worked pretty well. But it's a lot more pilot motion than I like, especially on a confined strip, and it didn't seem to shorten the take off roll much if any at all. So I think I'll stick with 10 for soft fields, and in any event, I'd rather put them in before starting the take off roll.

Cary

20* until airborne and milking off from there is the same procedure my buddy told me to use in his 185 on floats. Seems pretty standard for most Cessnas.