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Author Topic: Final notch of flaps on final in X-wind:  (Read 1322 times)

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Dan_Root

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Final notch of flaps on final in X-wind:
« on: July 13, 2016, 07:27:07 AM »
http://www.pilotworkshop.com/tips/crosswind_landings_flaps.htm

Interesting read and comments.  Also N/A to me since the L8A doesn't have flaps.

I completed my flight review a few months back and specifically flew one of SFS's (Harvey) C152's.  I hadn't flown a tricycle gear or used flaps in two years.  It was good practice to be in something different.

Curious though:  My mind always likes that I don't have flaps = I'm always ready to return to clean flight.  I remember getting checked out in a C172 once.  The CFI put on full 40 flaps and told me to climb.  It was all I could do to keep the nose from pointing up too much, the climb was slow.
« Last Edit: July 13, 2016, 10:43:21 AM by Dan_Root »
L8A - Slightly modified

Pilawt

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Re: Final notch of flaps on final in X-wind:
« Reply #1 on: July 13, 2016, 09:02:56 AM »
The last line of the article says, "Follow the guidance in your POH, get the approach stabilized early and don't add unnecessary speed."  That's very good advice.

In the case of the 172 (all of 'em, from '56 right up to the current 172S), POH guidance is simple:  "Normal landing can be made with power on or power off with any flap setting within the flap airspeed limits"; and "When landing in a strong crosswind, use the minimum flap setting required for the field length."

Cessna's former Manager of Aerodynamics and Flight Test, William Robinson, wrote that the recommendation for minimum flap in crosswind was "for better rudder control."

The article also says, "For what it's worth, most airline and corporate aircraft always land with full flaps."  Well, for what it's worth, a C-172 is not "most airline or corporate aircraft," and trying to fly it like it is can lead to trouble.  Most airline and corporate aircraft use partial flap for every takeoff.  Is that a reason to do likewise in a 172?

Moral of the story:  Fly the airplane you're in, not the one you might or might not fly someday in the future.
« Last Edit: July 13, 2016, 09:04:58 AM by Pilawt »
Jeff Jacobs
C-172N-180
KGYR / Phoenix AZ

chavycha

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Re: Final notch of flaps on final in X-wind:
« Reply #2 on: August 03, 2016, 03:36:59 PM »
Some food for thought:

A 172 can land very slowly with full flaps - 41kts is Vs0 on a 172N. 
Maximum crosswind component is 15 knots.
However, many 172s are placarded against slips with 40 degrees of flaps.

How are you going to make a good landing in a 15 knot direct crosswind WITHOUT slipping?
« Last Edit: August 03, 2016, 03:38:52 PM by chavycha »
Based in beautiful Creswell, Oregon (77S)

skywag

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Re: Final notch of flaps on final in X-wind:
« Reply #3 on: August 03, 2016, 04:28:21 PM »
''''How are you going to make a good landing in a 15 knot direct crosswind WITHOUT slipping?"""


Flaps on light aircraft are greatly over rated. Not needed at all in most landings, especially with cross winds. In a Cessna, flaps contribute a turning moment into the wind, contributing to poor controlled landings.

Swept wing jets with pod mounted engines NEVER slip to cross wind landings.

https://www.youtube.com/watch?v=x-X-Ih7cBHw

About to kick out the crab.
Desert Aire Airport Manager (M94)

chavycha

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Re: Final notch of flaps on final in X-wind:
« Reply #4 on: August 03, 2016, 10:24:02 PM »
Correct, you don't *have* to slip the aircraft to land in a crosswind.  However, I can't think of many even passable de-crab (kick-out) landings that I've seen by 172 drivers... flaps or no flaps. 
Based in beautiful Creswell, Oregon (77S)

hotrod180

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Re: Final notch of flaps on final in X-wind:
« Reply #5 on: August 04, 2016, 08:52:56 AM »
IMHO a "crab to kick-out" approach in a taildragger is a recipe for disaster, at least for me.
FWIW I use flaps for every landing, generally full flaps (40*), even in a crosswind.
Why NOT use the flaps? 
I've heard people mention avoiding wear on the rollers, etc-- IMHO that's like avoiding using the brakes to avoid wear on the pads.
Why TO use the flaps?
 They lower the stall speed, let you put the nose down for better viz without gaining excessive airspeed, and eliminate excessive float as long as you nail your desired airspeed.
I sometimes dump the flaps after touchdown to get more weight on the wheels in a gusty situation.
IMHO you should operate the airplane the way it was meant to be operated, and replace the consumable parts when required.

skywag

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Re: Final notch of flaps on final in X-wind:
« Reply #6 on: August 04, 2016, 11:14:06 AM »

FWIW I use flaps for every landing, generally full flaps (40*), even in a crosswind.
Why NOT use the flaps? 

Flaps in a high wing Cessna contribute a turning moment into the wind. Using full flaps increases the possibility of ground loop, for good aerodynamic reason. Just like the Cessna engineers said in Jeff's post above.
« Last Edit: August 04, 2016, 11:16:02 AM by skywag »
Desert Aire Airport Manager (M94)

chavycha

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Re: Final notch of flaps on final in X-wind:
« Reply #7 on: August 04, 2016, 02:04:10 PM »
I'm not advocating for one technique or the other, but it seems that most pilots of GA aircraft are much more comfortable with the sideslip method of crosswind landings.  Adding some flaps into the equation (20 or 30 degrees) makes everything happen a little slower.   That's a good thing.  Slower touchdowns - shorter ground rolls, less likelihood of a flat approach and bounce, more time to compensate for the 'whoa!' factor of gusty winds, etc.

I think Jeff nailed it : Moral of the story:  Fly the airplane you're in, not the one you might or might not fly someday in the future.
Based in beautiful Creswell, Oregon (77S)

HAL

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Re: Final notch of flaps on final in X-wind:
« Reply #8 on: August 25, 2016, 02:40:29 AM »
''''How are you going to make a good landing in a 15 knot direct crosswind WITHOUT slipping?"""


Flaps on light aircraft are greatly over rated. Not needed at all in most landings, especially with cross winds. In a Cessna, flaps contribute a turning moment into the wind, contributing to poor controlled landings.

Swept wing jets with pod mounted engines NEVER slip to cross wind landings.

https://www.youtube.com/watch?v=x-X-Ih7cBHw

About to kick out the crab.



Actually we do put the planes into a slip as we straighten the nose in the flare in big planes. A normal X-wind approach in the A330 (my current plane) is in a crab both for passenger comfort as well as performance. But as we begin the flare we'll push the rudder to straighten the nose and drop the wing a bit to counter the drift. Because of our higher landing speeds the amount of slip - and resulting wing dip - is relatively less than that of a slower GA plane. It's been the same in all the other planes I've flown for the airlines too: 767, A320, and DC-10. Also, just like GA planes we often land with a notch less flaps in strong crosswinds.

P.S., that YouTube video is nice, but it's as it's all flight sim it's not totally accurate.

David
David Sperry CFII MEI ATP FE
Hawaiian Airlines A330, 767, DC-10
And... 152, 172, 182, 337, 340, BE76, PA28, SR20, PA31, SF340, A320
KRNT