To full flaps or not to full flaps!

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Go Juice
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To full flaps or not to full flaps!

Post by Go Juice » Sun Mar 20, 2011 1:27 pm

I was having a discussion with a colleague not too long ago about seting full flaps or not when there is a strong crosswind.

I like the full flaps, gives you more drag than lift as opposed to flaps approach.

Whadaya think on that?


We're dealing with a PA31 here.

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Re: To full flaps or not to full flaps!

Post by square » Sun Mar 20, 2011 3:11 pm

I use full flaps. For some reason I've heard a lot of people say the additional "surface area" on the side of the flaps will push you further over in a crosswind, which makes no sense at all. The cross-section of the flaps that exposes when the flaps are down can't be more than 1% of the area on the side of the plane. And as far as the airplane is concerned, the air could be still with reference to the ground anyway. If you're in the air, you'll track with the wind regardless of your configuration.

The only difference is that you would typically use a higher approach speed flapless, and that way you wouldn't have to crab as many degrees into the wind to correct for drift. Makes your approach a little easier. But the better advantage of using flaps is that you'll touch down at a lower speed and raise the flaps to dump your lift, making the airplane way more stable on the ground.
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Re: To full flaps or not to full flaps!

Post by SuperchargedRS » Sun Mar 20, 2011 4:09 pm

I like a lower flap setting on a xwind to have a higher speed
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Re: To full flaps or not to full flaps!

Post by trey kule » Sun Mar 20, 2011 4:48 pm

It is good you mentioned the type of aircraft there, as the rule, I dont think, is a general one, and some bonehead will come on and tell you how you should never land his piper 9977 in a wind with full flaps...

Anyway, with the PA 31. The last part of the flaps comes on when you are assured of the field...right? How does the control feel at that point? How long is the strip? Airspeed, descent rate on the profile? Despite the theory that a long strip is easy peasy, many pilots start adding 10 kts for this relative and 10 kts for that one, and pretty soon we have an approach speed that approximates a space shuttle. Without the flaps you can burn up some pavement trying to slow it down.

So. After flying all the PA 31 series for many thousands of hours, I cannot think of a time when I did not use full flaps to land...And I have landed in many many northern places in wicked winds. The closer you can fly to the normal is the best. When you start adding ref speeds for gramma, or not using flaps you are making changes, that collectively may cause you some grief when you are a foot above the runway, out of speed, out of runway, and out of ideas.

Hope this helps. BTW. How was the plane to land without flaps and with lower flap settings during training?
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Re: To full flaps or not to full flaps!

Post by Cat Driver » Sun Mar 20, 2011 5:45 pm

It's been while since I last flew an airplane, but I seem to remember something about adding flaps, I think what adding flaps does is increase the rate of descent and steepen the flight path with no increase in airspeed.

Maybe I am wrong but I'm almost sure that is what happens.

So unless there is a notation in the POH about using flaps why not use them?
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Re: To full flaps or not to full flaps!

Post by Hedley » Sun Mar 20, 2011 6:02 pm

the type of aircraft
Exactly. I don't think I've ever landed the C421 or L39 without full flaps.

But the story changes with little aircraft.

For example, I rarely use full flaps on the 7GCBC Citabria. Not sure why that aircraft has flaps at all, actually. It so naturally sideslips.

And on the Maule, I have two flap selections, on the johnson bar: 15 degrees and 35 degrees. In a training environment, I only use the 15 degree flap selection, for both takeoff and landing. You really don't need the extra drag of the 35 degrees flaps without an obstacle, and it makes the overshoot procedure far simpler during touch-and-goes.

As Larry King said when asked what kind of underwear he wore: "Depends".
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Re: To full flaps or not to full flaps!

Post by burhead1 » Sun Mar 20, 2011 6:14 pm

Are we talking a steady crosswind or a gusting crosswind?? if it is gusting, i personally would use less flap and again DEPENDS on aircraft and the overall situation.
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Re: To full flaps or not to full flaps!

Post by Go Juice » Sun Mar 20, 2011 6:30 pm

Steady xwind. Even if it was gutsy, i don't see why you would use less. Keep the speed on the up side for sure but why not have them fully extended. The PA31 lands pretty good with no flaps or flapps approach but it eats up a bit of runway because you would be comming in faster than the usual. but if the wind is blowing pretty hard and crosswind, wouldn't you want to have the plane down and slowed ASAP to make sure you are within taxiing speed sooner than having to fly down the runway with lift on the wheels still and the end coming?

Maybe i got it wrong too.

What the old dogs have to say?
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Re: To full flaps or not to full flaps!

Post by Cat Driver » Sun Mar 20, 2011 6:43 pm

to make sure you are within taxiing speed sooner than having to fly down the runway with lift on the wheels still and the end coming?
Landing short means touch down on the start of the landing area and at the lowest airspeed that is safe.

The higher the airspeed during the hold off period of a landing the more you increase the time you are subject to the airplane becoming unstabalized in its path over the runway due to wind gusts and wind direction changes.

So plant the fu.ker at the start of the runway at the minimum airspeed that will maintain control with no drift and pointed straight down the runway.

That is how this old dog does it. :mrgreen:
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Re: To full flaps or not to full flaps!

Post by Go Juice » Sun Mar 20, 2011 7:08 pm

Makes sence. What do you do regarding flaps. If there is a crosswind, Do you think the extra flaps will take you across the runway?
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Re: To full flaps or not to full flaps!

Post by Cat Driver » Sun Mar 20, 2011 7:16 pm

Makes sence. What do you do regarding flaps. If there is a crosswind,
A cross wind will not make any difference to my flap selection unless the conditions are so extreme that a missed approach may be required, in which case I will select a flap setting that allows a safe missed approach.
Do you think the extra flaps will take you across the runway?
The only way an airplane will take you across the runway when you don't want it to go there is when you are no longer in control of the airplane.

So the simple answer is think ahead of the airplane and always keep it under control... :mrgreen:

Generally speaking all the written exams in the world will not teach you aircraft handling skills, these skills are best learned by good instruction and experience as you gain flying time.
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Last edited by Cat Driver on Sun Mar 20, 2011 7:20 pm, edited 1 time in total.
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Re: To full flaps or not to full flaps!

Post by Go Juice » Sun Mar 20, 2011 7:17 pm

Wilco!

thank you sir!!
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Re: To full flaps or not to full flaps!

Post by Cat Driver » Sun Mar 20, 2011 7:22 pm

:mrgreen:
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Re: To full flaps or not to full flaps!

Post by DHCdriver » Sun Mar 20, 2011 8:09 pm

I've never used full flap with the beav. Try using full flap in high winds with a STOL wing and you will think harder the next time you pump them all the way down.
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Re: To full flaps or not to full flaps!

Post by burhead1 » Sun Mar 20, 2011 8:19 pm

DHCdriver wrote:I've never used full flap with the beav. Try using full flap in high winds with a STOL wing and you will think harder the next time you pump them all the way down.
So in your head your saying "get down you fu*er , down" :smt040
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Re: To full flaps or not to full flaps!

Post by Cat Driver » Sun Mar 20, 2011 8:34 pm

I've never used full flap with the beav.


You have never used full flaps on a Beaver?

Do you fly one for a living?

Try using full flap in high winds with a STOL wing and you will think harder the next time you pump them all the way down.
Using full flaps in a Beaver in high winds would be poor judgment making for sure, but the airplane was designed and approved for the flap range available, therefore it is safe to use full flap if needed.
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Re: To full flaps or not to full flaps!

Post by ScurvyDog » Mon Mar 21, 2011 4:50 am

I always use full flaps on the Navajo or any cabin class twin for that matter. Doesn't matter what the wind is. I have never found the flaps to affect the weathercocking. Cabin class twins have such large fuselage side areas that the little flap they have doesn't seem to do much for weather vaning them. The reason I use full flaps all the time is to reduce landing speed and save brakes/tires, wheel bearings etc. I also believe the better you plant it on the runway and the sooner you get down to taxi speed the more control you will have in an wind.

All this changes with the barn doors they put on single cessna's!
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Re: To full flaps or not to full flaps!

Post by DHCdriver » Mon Mar 21, 2011 7:15 am

Cat Driver wrote:
I've never used full flap with the beav.


You have never used full flaps on a Beaver?

Do you fly one for a living?

Try using full flap in high winds with a STOL wing and you will think harder the next time you pump them all the way down.
Using full flaps in a Beaver in high winds would be poor judgment making for sure, but the airplane was designed and approved for the flap range available, therefore it is safe to use full flap if needed.
Yes, I flew one for 13 years. Also I agree it is safe to use full flap if needed(small lakes,small strips). Each airplane is different,you can't compare a fast twin with a slow beaver. Everybody has their own little preference with flap selection.Cheers.
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Re: To full flaps or not to full flaps!

Post by iflyforpie » Mon Mar 21, 2011 8:19 am

The flaps in the PA31 are pretty ornamental. I watched a couple of winners who had never flown one before take off in a PA-31-310 with full flaps.
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Post by Beefitarian » Mon Mar 21, 2011 10:42 am

Cat Driver wrote:It's been while since I last flew an airplane, but I seem to remember something about adding flaps, I think what adding flaps does is increase the rate of descent and steepen the flight path with no increase in airspeed.

Maybe I am wrong but I'm almost sure that is what happens.

So unless there is a notation in the POH about using flaps why not use them?
I flew one this year but that's the exception for me.

I do recall after my first solo X-Country talking with my instructor about the cross wind giving me a hard time in the 172 I drove on it, he asked how much flap I used. I told him all of it. He laughed at me like a Hedley and said, "There's your problem, full flap reduces the rudder's effectiveness on that plane." I don't know what the rudder has to do with landing because I've never flown tail dragger. Sounds like gibberish looking back.
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Re: To full flaps or not to full flaps!

Post by photofly » Mon Mar 21, 2011 10:59 am

"There's your problem, full flap reduces the rudder's effectiveness on that plane."
Perhaps he was thinking that at touchdown, your airspeed is minimized with full flap, therefore the rudder effectiveness is diminished. (Although on a 172 there's hardly an difference in touchdown speed between 20 degrees of flap and full flap, is there?)
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Post by Beefitarian » Mon Mar 21, 2011 11:32 am

Around 10 knots I think. Maybe this could help us figure out the relation of the flaps to the rudder.
ScurvyDog wrote:All this changes with the barn doors they put on single cessna's!
Like I said though, I've only drove tricycles why would I use my feet until I was slamming on the brakes?
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Re: To full flaps or not to full flaps!

Post by iflyforpie » Mon Mar 21, 2011 12:43 pm

I've never had any problems with rudder authority with full flaps on Cessna 172s. With 40 degrees of flap you can crank in 45 degrees of bank and hold the nose straight if you push one of those 'foot rests' to fhe floor. :wink:

In a small Cessna, full flap every landing. If the wind is howling and I am coming in on a three degree (ugh), I'll put in 20 until short final and then put them all on, just so I am not revving the living daylights out of the engine to stay on slope. Otherwise, I will just come in more steeply.
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Post by Beefitarian » Mon Mar 21, 2011 12:53 pm

I did stop using flap for a while after that and my cross wind landings were better.
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Re:

Post by nightbird » Mon Mar 21, 2011 3:19 pm

Beefitarian wrote:"There's your problem, full flap reduces the rudder's effectiveness on that plane."
When you add full flaps some of the airflow that goes to the tail is deflected (high wing), hence the effectiveness reduction in the rudder. Try doing a forward-slip without flaps and full flaps and you will notice some difference. Now when it comes to landing it will only affect if you have to use full rudder.
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