Use of flaps during heavy crosswinds

[Skyway]

Hello all, I normally don't post here much, but I need some help. Apparently a very big debate about the use of flaps during landing has come up at the flight school where I teach. I guess an instructor told the director of flight training that flaps should never be used during crosswinds or gusts for student pilots. Now all of us instructors have to come up with some input backed up with facts. I normally teach the use of flaps but to increase approach speed with half of the gust factor applied. If the winds are really kicking then maybe deploy partial flaps. I usually will teach a student how to make a no flap landing but, I don't normally teach that method for strong gusts. I thought that I would at least start here for some theories or what not. Everybody here on this forum seems to know their stuff.
I remember when I flew for the airlines, even during gusty crosswinds @ KMKE we still had to deploy full flaps as per procedure SOP's. That was done even in the Dornier 328. Thoughts?

[Blackhawk]

[minitour]

I have numbers to land with Flaps up (0), Takeoff/Approach (15) and Land (35), so I guess I could do any of those. Normally for a single engine landing, we've trained to land flaps 15 and for all other landings (two engines), we land flaps land (35). If the winds are gusting so bad that I run out of rudder, I either pick a different runway or pick a different airport. It's just not that important for me to land at that specific airport 99.99% of the time.

It's been a while since I've taught primary, but if I got to teach a student pilot again, I'd probably teach landing in the landing configuration every time for normal operations. Emergency ops are obviously different.

That's my $.02 and it's worth what you paid for it.

-mini

[drunkenbeagle]

If it is gusting enough for it to be an issue either way, I don't think it is a good day for students to be in the pattern.

My personal opinion is that 10 - 20 degrees is ideal for a Cessna when it is gusting bad, mostly because of the higher likelihood of going around. I'd like to already be in a configuration that will get a decent rate of climb if necessary.

On a practical note, students should be comfortable with any flap configuration, as they can and do break. That is enough reason alone for teaching no flap landings.

[Nihon_Ni]

The use of flaps in a cross-wind is just a technique. Here's my technique for a C-172: When I have more than 5 kts of cross-wind component (it's not uncommon for us to have 15+ kts x/w component where I live) I generally stop my flap deployment at 20 degrees. My reason is that from 0 to 20 degrees of flaps I get more lift and more drag, but it's mostly lift. From 20 to 40 degrees I mostly get an increase in drag with very little additional lift. (There's a large change in stall speed from 0 to 20 degrees of flaps, but there's only a few knot change in stall speed from 20 to 40 flaps.) Since I'm going to be using a side slip, I'll generate all the drag I need so I don't add the "mostly drag producing" section of the flaps. Having said that, there's nothing "wrong" with using full flaps in a cross-wind. The danger is that you can get the airplane so loaded up with drag that you can get a big descent rate if you're not careful. That's my reason for stopping at 20 degrees.

If someone has a different technique, that's fine. There really is no right or wrong answer, except for the guy who says he should "never" use flaps. I could think of a bunch of reasons to use them/not use them/do something different given the right scenario. To me, the reason behind the rule of thumb is more important than the rule of thumb. (And it is only a rule of thumb.) I try to stress this to my students, and flaps in a cross-wind is a great area to have them make up their own mind based on their own reasons. I have my reasons, but I'd rather have them adopt a different technique based on their own reasons than to blindly follow my technique based solely on "my instructor says so."

As for gusts, I generally add half the gust factor and stop at 20 degrees of flaps. I have the luxury of a long runway with no obstacles, so might change my mind if I was faced with different circumstances. My reason for 20 flaps is that puts me in the initial go-around configuration. If I need to cob on the power as a result of a lull in wind, the airplane is already configured to give me good climb performance.

[Skyway]

Thank you all for the replies. Some of you have made some very good points about partial flaps keeping the aircraft in a position for a go around and minimizing sink rate. I don't know why I didn't think of that at first, but that is a very good point. Please keep your thoughts and opinions coming.

[SteveC]

Originally Posted by Nihon_Ni

The use of flaps in a cross-wind is just a technique.

< balance removed for brevity >

Excellent post.

[nosehair]

Originally Posted by Nihon_Ni

My reason is that from 0 to 20 degrees of flaps I get more lift and more drag, but it's mostly lift. From 20 to 40 degrees I mostly get an increase in drag with very little additional lift.

This is my technique and thinking also. However, that mix of lift over drag is only valid during the stabilized approach portion. When you start the flare, think about a full flap configuration: as the nose pitches up the flaps go more perpendicular to the runway. The bottom surface of the wing with full flaps down is more of a "cup" to catch a sudden upgust, and while the latter portion of flaps is more drag than lift, it is still an increase in lift so that this sudden upgust will cause more of a ballooning effect, and with full flaps of a high wing blanking out downwash airflow over the elevator, there is less positive elevator and rudder control.
More flaps=less positive control.
Less flaps=more positive control.
Consider available runway length and practice landings in all flap configurations and wind conditions so you can decide the appropriate setting.

[tgrayson]

Originally Posted by Nihon_Ni

My reason is that from 0 to 20 degrees of flaps I get more lift and more drag, but it's mostly lift.

That doesn't have any real meaning for an aircraft in flight. If you actually increased lift you'd balloon, which you'd immediately suppress by lowering your AoA, reducing lift again. After the 20 degree flap deployment, you'd have Lift = Weight, just like before, except with a slight increase in drag.

There is only one real effect of flaps on crosswind landings: a reduction in rudder authority. At the extreme, this will limit the amount of crosswind the aircraft can handle, so it's not completely a technique issue.

[Jbroz04]

I think you should use whatever works for you. I land full flaps almost all the time because we have a short runway. With proper techinque a full flap landing in gusty wind conditions can be done. All that really matters though is what do you feel comfortable doing and what will accomplish the mission. The mission being getting on the ground safetly.

[BrewMaster]

Originally Posted by Jbroz04

I think you should use whatever works for you. I land full flaps almost all the time because we have a short runway. With proper techinque a full flap landing in gusty wind conditions can be done. All that really matters though is what do you feel comfortable doing and what will accomplish the mission. The mission being getting on the ground safetly.

I agree. Without worrying about SOP's, do what feels right. There is no black and white when it comes to using flaps in wind. There are too many factors and ways of doing it. What feels comfortable for one pilot may not necessarily feel right to another.

[PilotBeckfizzle]

I've heard valid arguments for both. Less flaps, higher approach speed more efficiency from the control surfaces, etc. The argument I've heard for using full flaps is that if you look at the aircraft from the side how much surface area is full flaps actually adding to the aircraft? It's virtually none; hence no affect on the aircraft.

I personally just use whatever I need. I do find myself using less flaps (typically 20 on a 172, 182) in high crosswinds.

[ppragman]

I usually use full flaps unless its really blowing really hard, then I'll use whatever makes it most comfortable for the passengers. Sometimes getting tossed around like a kite makes people nervous when you're close to the ground. A little extra speed (though not usually my style) can definitely smooth out the feeling of getting yawed willy nilly left and right.

[mshunter]

Originally Posted by Blackhawk

, You want some more Coke?

Edit: P.S. Just make sure that whatever you do, put the damn airplane on the ground w/out bending it.

[Maurus]

Originally Posted by tgrayson

That doesn't have any real meaning for an aircraft in flight. If you actually increased lift you'd balloon, which you'd immediately suppress by lowering your AoA, reducing lift again. After the 20 degree flap deployment, you'd have Lift = Weight, just like before, except with a slight increase in drag.

There is only one real effect of flaps on crosswind landings: a reduction in rudder authority. At the extreme, this will limit the amount of crosswind the aircraft can handle, so it's not completely a technique issue.

Yup. I can take a Cherikee 140 into 15 knot Xwind with full flaps. Find winds above 15 and you will landing crooked with full flaps. If you like having a little swerve after a landing, be my guest to land with full flaps in high winds.

[Jbroz04]

Maurus I would have to disagree with you. Being that my family owns a 140 and I have about 200 hours in it as PIC you can land them full flap in 15 knot xcross and above. The flaps are very small on the 140. Now if you were talking bout a cessna with those monster flaps then yes I would agree above 15 they would cause you to be alittle sideways on landing.

[jynxyjoe]

Eh, until I'd get up to the 20knt x-wind mark I left the flaps in on a SEL. Of course, getting close to the 20knt mark I'd just take them all out. On a faster plane, V tail or the Viking, I always had the flaps in. The plane was heavy enough I didn't feel much.

I've been known to make things tougher than they need to be sometimes... maybe a lot.

[MidlifeFlyer]

True:

In my primary training, I was given the "no flaps for landing in a crosswind" spiel. For years I wondered what I would ever do if confronted with a short runway and a crosswind

Fast-forward to my CFI training. Cessna 172. BIG xwind

My instructor tells me he wants a short field landing. I look at him like he has three eyes.

It was a complete non-event.

[mooneyguy]

cross wind is just a wind. fly the plane as you would normally fly it. if you use flaps on a calm day use flaps in a cross wind. Why increase airspeed in a crosswind (I think this is a crutch because the person is afraid of the crosswind thinking extra airpseed is safer)? so now your a foot above the runway with 10 extra knots to bleed off in a cross wind trying to hold centerline...come in on speed, flaps set (at normal setting), land. You do not want to float in a cross wind.

with Gust, add half the gust factor into airspeed.

someone pass the and a coke

[clestudentpilot]

Apparently no one uses a POH to gather information anymore!

[minitour]

Originally Posted by clestudentpilot

Apparently no one uses a POH to gather information anymore!

Care to elaborate?

-mini

[clestudentpilot]

Originally Posted by minitour

Care to elaborate?

-mini

I know not all, but some, especially Cessna's recommend flap settings for crosswind landings. While I know someone will ridicule me for saying it is only a "recommendation", that doesn't mean to ignore the information. Generally info isn't in a POH just because the typist is a union worker and had to read 10,000 words to get paid the full amount.

I also do realize that some POH's don't even mention crosswind landings. I know for myself, if I am unsure about a procedure to be used for a specific airplane, I think the POH is usually a pretty good place to start

[tgrayson]

Originally Posted by clestudentpilot

I think the POH is usually a pretty good place to start

It's a good place to start, but that doesn't mean that you have to end there. Being satisfied with that answer is simply memorizing procedures without understanding them. That isn't what this thread is about.

[shdw]

Originally Posted by Maurus

Yup. I can take a Cherikee 140 into 15 knot Xwind with full flaps. Find winds above 15 and you will landing crooked with full flaps. If you like having a little swerve after a landing, be my guest to land with full flaps in high winds.

I personally took a 152 in at full flaps to gust 37, I never land without full flaps regardless of the wind or the gust. That said, I also don't use a slip technique to land, I crab and then straighten out in the flare while flying approach speeds of between 65-70.

Slip technique is great for teaching the student how much wing dip will be needed in the flare, so I use it for that. But for the approach phase the slip, IMO, is a pointless technique.

To the OP: Tgray gave you the only real issue as to why flaps in a crosswind can become an issue, that is the limit to rudder authority. The best reason I can give for you to tell your buddies is that flaps increase stability, they should all remember this from their ME training. We also know that an increase in stability means a decrease in control. The why is all speculation, but you might find this topic thread a good place to do some further research: http://forums.jetcareers.com/cfi-cor...ull-flaps.html

That said, if you don't use a forward slip and instead crab the aircraft till flare you shouldn't have any issues on rudder authority. It really depends on what technique your students are being taught to use.

As mentioned previously the use of partial flaps is certainly still a good idea to decrease stall speed without a drastic increase in drag. Some aircraft don't have a lot of power, like a 152, so if you get slow on a real gusty day and the student doesn't react with near full power quickly it can become dangerous quick. This is also what I typically teach my students, to stop at 20/25 flaps depending on aircraft instead of using the 30-40 range. But I never limit them to the use of full flaps or make them think it is some cardinal sin that will cause a subatomic eruption of the aircraft.

[Maurus]

Originally Posted by Jbroz04

Maurus I would have to disagree with you. Being that my family owns a 140 and I have about 200 hours in it as PIC you can land them full flap in 15 knot xcross and above. The flaps are very small on the 140. Now if you were talking bout a cessna with those monster flaps then yes I would agree above 15 they would cause you to be alittle sideways on landing.

I have been in 15 knot xwinds in the 140 where I had to have full rudder to keep the plane aligned with the runway.

Originally Posted by shdw

I personally took a 152 in at full flaps to gust 37, I never land without full flaps regardless of the wind or the gust. That said, I also don't use a slip technique to land, I crab and then straighten out in the flare while flying approach speeds of between 65-70.

Only problem with that is the stronger the x-wind the more of a jerk the passengers will get when landing because of having to kick the rudder in right before touchdown. For purposes of controlling an aircraft, that technique works well.