I have read many discussions on flap settings for short take offs and the flap setting that causes the greatest amount of lift is the same angle as maximum aileron deflection..... right? this would be about 15 degrees on my R172K.
Well, if landing on a short field and a steep approach is not a factor nor is avoiding excess speed.... would 15 degrees be the right setting vs 30 or 40 degrees of flap?

Does 30 - 40 degree setting cause more lift than 15... at the expense of more drag, having a detrimental effect on stall speed as compared to 15 degrees and requiring a higher angle of attack to come in slow?

I have bent my tail protector once with 40 degrees and power on the prop ( thankful for that 11 dollar gadget )

What are your opinions on this? I operate out of a small grass field in the amazon that has no obstructions on final.

thanks in advance,

G

I almost always use 20 degrees of flap (second notch) on Cessnas for takeoff. First notch is 10, second is 20, for most Cessnas.

For landing, I GENERALLY use 30 or 40 flaps. With these settings, it is easier to work lift against drag for precision touchdown point. 30 provides a little less drag than 40, and just as much lift as 20, so that often works fine. Note that in later models, Cessna has limited flap travel to 30, because of dumb pilots who were apparently unable to successfully execute a go-around with full flaps. Duh.

I like the full flap position, but I have to admit that 30 works just about as well, except for very steep approaches.

MTV

I almost always use 40. I like a steeper approach to miss the power lines 600 ft from touchdown at 34 with more margin. Always means 95% of the time.

I would try to stay away from a Cessna with a limit of 30 deg.

Tim

gflores

I think that 40 degrees flaps gives the most lift and the most drag. Your stall speed should be the slowest. Your deck angle should be lower at the same reference speed.

I think

flyer

Mike,
Are you pulling in 20 degrees of flap after the take-off roll has started or do you start with 20 degrees from the beginning?
WW

gflores71 wrote:
Does 30 - 40 degree setting cause more lift than 15

Yes.

WWhunter wrote:Mike,
Are you pulling in 20 degrees of flap after the take-off roll has started or do you start with 20 degrees from the beginning?
WW

FWIW I think there's an extensive argument, er I mean discussion, about this technique on another thread.

In my short time as a pilot I have noticed that 10,20 and 30 degrees are flaps and 40 is air brakes. You can feel the air "buffeting" behind the flaps at 40 degrees. I don't think I have ever flown anything that has enough power to make 40 work well for lift. If I want to do short landings, I always approach with 30 and then hit 40 when I know I'm 100% sure of landing. I do this because a Cessna 150 does not climb well with 40 degrees of flaps.

My friend was landing a 150 at an abandon strip he had used before and some smart ass decided to use 2X4's for the X's on the runway since he was there last. He didn't notice what they were till right before touchdown. He hit the power and did one slow bounce just past the 2X4's. He stayed in ground effect till he had enough speed to reduce the flaps. Then the plane started to climb. Ever since my friend told me this I don't do approaches with 40 degrees.

Jaerl,
Does your friend know what the X is for? Is he a senator.

I guess he was thinking "X marks the spot". Some people

We have a 69 172 k and i always use 40, once i know the runway is made. I can usually get down and stopped in 400-600 ft on pavement depending on the wind and approach. Go arounds are not too bad with 40, just really have to push that nose down once the power is on.

Tom

Jaerl wrote:In my short time as a pilot I have noticed that 10,20 and 30 degrees are flaps and 40 is air brakes. You can feel the air "buffeting" behind the flaps at 40 degrees. I don't think I have ever flown anything that has enough power to make 40 work well for lift. If I want to do short landings, I always approach with 30 and then hit 40 when I know I'm 100% sure of landing. I do this because a Cessna 150 does not climb well with 40 degrees of flaps.

My friend was landing a 150 at an abandon strip he had used before and some smart ass decided to use 2X4's for the X's on the runway since he was there last. He didn't notice what they were till right before touchdown. He hit the power and did one slow bounce just past the 2X4's. He stayed in ground effect till he had enough speed to reduce the flaps. Then the plane started to climb. Ever since my friend told me this I don't do approaches with 40 degrees.

Jaerl - if your stall speed is reduced with 40 degrees of flaps from what it was at a smaller flap extension, then the flaps are providing added lift, in addition to the added drag. 40 degrees seems to be a common max flax extension for light aircraft, including Cherokees such as I fly, and the max flap extension provides your aircraft's lowest stall speed.

As for the first poster's (Gflores) problem of hitting your tail cone with 40 degrees of flaps "with power", maybe your issue is you need more down elevator as well as more power to flatten out your short final and round-out to flare. Most light aircraft including C172s will tend to pitch up when adding flaps, and if you're hitting full flaps just over the fence that could be causing the tail-low/pitch up attitude. When you lower the nose to maintain your desired approach airspeed with the addition of flaps, and also keep some power on, that should keep you from hitting your tailfeathers in the dirt, and still let you land on the mains without wheelbarrowing your nosewheel.

nmflyguy, I totally agree with you and 40 degrees is the best for short landings. More drag and more lift equals lower ground speed. I was taught that 10 & 20 have more lift than drag and 30 & 40 have more drag than lift.

GFlores, the more flap you use the more the nose goes down not the tail. Sounds like you should use a little less throttle and don't flair quite so much. What you described sounds like your hanging on the prop pretty heavy. My 175 had a tail ring protector but my mechanic told me to take it off. He said they had repaired planes that had used them because it has more leverage and bends the tie down ring area if it hits hard.

Best lift setting is definitely what you want for short-field departure. But for the shortest-field landing, you want lowest stall speed configuration, which should be the full flap setting, whatever that is. If this setting makes go-arounds a challenge, I would practice a lot. If you can get results that are sufficient with a flap setting that is less of a challenge, perhaps it is better to use that.

When I started learning in a PA-22 up here in the middle of nowhere, Alaska, the old timers around here, who have lots of time in these airframes and have been into all sorts of stuff with them, insisted that all landings are made full flaps with the airplane because it allows the shortest ground roll. So I spent a lot of time practicing to make sure I could handle the go-arounds, and that is part of my test evaluation of any strip.

My two cents.

ps Many airplanes, including mine, can land a lot shorter than they take off. If I land in 400 feet on a 600 foot lake, that's great, but I'm parked there for eternity unless I have a big head wind because that is less room than it takes for me to get off the ground...so remember to plan on having a takeoff margin if you are capable of landing shorter than you are taking off.

dirtstrip wrote:Jaerl,
Does your friend know what the X is for? Is he a senator.

"Cessna 123, turning final for runway X".....

Some days my friend wishes he had small N Numbers too.

Thanks for the replies, as mentioned by Jaerl.. greater flap settings do cause more drag requiring more power to keep adequate speed and thus a higher angle of attack. My R172K has a Sportsman cuff that allows the plane to keep flying at a more than average angle of attack if using power to keep me above stall speed. Will just have to practice a technique that allows me to come in zero power avoiding the higher angle.... I guess bigger mains would help as well haha.

My takeoffs close to sea level are usually shorter than my landings due to the cuff and 210HP stc.