reduces some drag and adds lift

Coefficient of lift increases with camber, so not sure about this. Agree drag increases.

With more flaps the center of lift moves towards the wing roots, and there is some loss of lateral stability. With increased drag and more power, the reduced lateral stability might result in an earlier stall, but I don’t convince myself of this reason for a slightly higher stall speed at F40. Test pilots would plot dozens/hundreds of tests before they convinced themselves that Flaps 30 has a lower stall speed than Flaps 40.

Another theory might be the semi fowler design stops increasing wing area at Flaps 30, and the increase in drag of flaps 40 dominates the camber effect. But F40 is not F90 so wing area is still increasing albeit at a smaller rate.

It is always worth recalling that the Wright brothers got there by experimentation and not through fluid dynamic calculus - in fact the Navier Stokes partial differential equations for fluid dynamics remain incomplete for well over a century, with a large money prize still outstanding for completing them.

The French and British bashed away at calculus while the Wright Brothers tinkered in their wind tunnel.

Yes, Barnstormer, less flap will do fine in 40 MPH headwind. The greater the headwind component, the lesser the pitch attitude necessary to have really slow groundspeed.

I was too lazy to look and just pushed the electric flap lever to the stop, even in 40 MPH winds. I always angled across in any crosswind so 40 was default for me. Care must be taken to flair a bit to touchdown on the mains only and not prang the nosegear.

30 degrees of flap doesn't stall slower than 40 degrees in the 182. Clmax is higher at 40. You can prove it by flying at ground effect at 30 degrees and dialing in 40, and watching the ground move away.

In my 182, it's between 1 and 2 mph slower at 40 degrees after the CAS conversion. Which is no big deal.

40 is nice for steep approaches for the extra drag, especially with slip when one wants to drop down to get an extra 150' or so of runway starting in front of tall trees or other terrain.

30 works nicely for previously mentioned reasons, and I can't think of any reasons why it isn't a better choice for most intents where approach clearance isn't a factor.

I like reduced or zero flaps in significant crosswinds. At 60 ias with zero flap landing in a 182 in a 30 mph crosswind, you are still only touching down at 51 mph along the runway, for example. So the extra control and go around margins are much higher, while the groundspeed means the touchdown is comparable on the tires to a calm wind landing at 40 degrees.

I use the Johnson bar as a reverse collective and use whatever flap is necessary to hit the intended touchdown spot.

All depends on the angle at which I'd like to approach the spot and whether or not I want to drag it in with any power.

Doesn't matter which flap position is needed. I'll use them all.

John 54724 and other 170B drivers. I thought it was common knowledge that slipping a B model with full flaps is known to produce a tail stall. I had an A model back when and heard that was the case for B models but not A models because of different flaps. Be careful. Steve

I have tried it at altitude but only at one CG. No tail stall, but weird behaviour with no more centering of the elevator. It wanted to go to the stop.

I just avoid it, I like power off approaches, go 20 degrees, slip if I need to, then 40. If I am too high I go around. I must admit I have had to stop the impulse to slip just a little, but realistically if you can’t get a 170 down with 40 you are too high or too fast.

duplicate

daedaluscan wrote:.... realistically if you can’t get a 170 down with 40 you are too high or too fast.

I don't feel the need to slip with Cessna barndoor flaps.
If I'm too high on a standard approach,
I pull the nose up to about halfway between normal approach airspeed & stall speed,
and the sink rate dramatically increases.
You can control the sink with power, all the way down to the runway for a slow touchdown,
or when back on the proper glideslope, push the nose back down to a normal approach speed & landing.

Avoid slips with full flaps in a Cessna 170B when you are close to the ground. You can have a very bad day.

What Hotrod 180 is describing effectively is "The Stall Down Landing" page 302 in Stick and Rudder. Even if not too high, deceleration on short final results in enough sink/mush to require power and pitch to near touchdown. If deceleration continues on down to ground effect, power will be required all the way to touchdown...The apparent brisk walk rate of closure short final to touchdown on the numbers slowly and softly. Page 304..."Once the normal glide has been broken, the process of stalling the airplane down can be gauged entirely by watching the spot and the perspective in which it appears and its apparent motion."

I think we are all on the same page here, even if our terms are slightly different.

I dislike the term "stalling it down" because the airplane is not stalled.
"Mushing it down" might be more accurate but some people might not get it.
"Low airspeed, with a high sink rate" is accurate without being too awfully wordy.

Terminology is key in conveying & understanding ideas.
I don't usually get a lot out of your posts, Contact, mainly because of your terminology.
Instead of having to interpret how you explain things,
your posts might be more effective if you would explain things in a way others can more easily understand.

I will try harder, hotrod 180. I like Wolfgang's terms because they predate integrated instrument terms that came into general usage with the PTS in the 70s. Your explanation was fine, but accepted terminology today is way too dependant on V speeds which are less accurate and discount sounds, sights, and feel which are far more accurate and useful. Thanks for the reply. Contact.

"If you can't explain it simply, you don't understand it well enough." – Albert Einstein.

"Hell, if I could explain it to the average person, it wouldn't have been worth the Nobel prize." Richard Feynman

My philosophy on slipping with 40 degrees is "do I really want to kill myself while trying to prove that this is bullshit"? For me the answer is no so I don't do it.

hotrod180 wrote:I dislike the term "stalling it down" because the airplane is not stalled.
"Mushing it down" might be more accurate but some people might not get it.
"Low airspeed, with a high sink rate" is accurate without being too awfully wordy.

I tend to think of the airplane becoming more of a lunar lander when I am behind the power curve. I am using power at that point to arrest my rate of decent. The further behind the power curve the more power I need. Then learning to add more power into the flare to arrest the final decent since there is very little remaining lift reserve. I started making much smoother short field landings wheel or three point once I looked at this way.

I have enjoyed reading this thread. I have been someone who uses 40 degrees of flaps in most situations. When I first started flying the 180 I was concerned that I might need more rudder authority in a crosswind, but I have never experienced this phenomenon and feel comfortable with 40 degrees of flaps in X winds. I am going to experiment with 30 degrees setting in some situations now.

daedaluscan wrote:"Hell, if I could explain it to the average person, it wouldn't have been worth the Nobel prize." Richard Feynman

My philosophy on slipping with 40 degrees is "do I really want to kill myself while trying to prove that this is bullshit"? For me the answer is no so I don't do it.

I've slipped two different 170B's and one 170A at altitude with full flaps. Max slip, with one foot to the floor and

The A model had no issue as expected. One B model shuddered a bit and then spun.

The other B model clearly blanked the tail during the slip and pointed what felt like straight down until it started flying again with no pitch control at all during the event.

Don't try this low to the ground.

Like the B model 170 guys say, there is generally no reason to slip with Cessna's very effective 40 degrees of flap. I have experienced only one real need, the low level engine failure. While spraying or even after a basic low ground effect takeoff, I always found myself with enough zoom reserve to get up and see a short distance. That meant I was always fast for the near hemisphere available. I almost always needed full flaps and full, rudder to the stop, forward slip to make the beginning of the LZ. So that's 12 times in 17,000 hours for me. Hopefully that's not that much of a consideration for most of you.

What lesuther said about touching down at airspeed is absolutely book correct but not physically correct, given a flaired to full stall landing. He knows what he is talking about, no flap in wind being similar to full flaps in no wind, but the POH Vs and Vso thinking has misled him...us.

"I like reduced or zero flaps in significant crosswinds. At 60 ias with zero flap landing in a 182 with a 30 mph crosswind, you are still only touching down at 51 mph along the runway, for example." This is book correct and physically correct. We are still flying. We have not flaired much and the pitch angle is slight and most importantly we have not stalled.

"So the extra control and go around margins are much higher, while the groundspeed means the touchdown is comparable on the tires to a calm wind landing at 40 degrees." Not if the calm wind landing at 40 degrees flaps is flaired properly and touchdown is at the airspeed at which the airplane stalls in low ground effect. The airspeed, don't look, should be well below 51 mph. No, we can't flair as much in the 30 mph crosswind, but we should be able to touchdown well below 51 mph groundspeed. Otherwise we are putting more groundspeed pressure and irritation onto the tires and airframe with the help of a headwind component than without.

A big part of the confusion of Vs or Vso is that we are led into the assumption that this is the in ground effect airspeed at which the wing will stall. It is not. Vs or Vso is the out of ground effect airspeed at which the wing will stall. And unless we want to drop in from around 30 feet (average wing length,) low ground effect stall airspeed is far less than out of ground effect stall airspeed.

Science will take responsibility only for what is strictly stated. Art, on the other hand, might take the pilots point of view (see evil), audio (hear evil), and even speak evil. We need to pay attention to what the airplane wants to do and the relative feel and sound and sight of things. Perspective, apparent motion, relative wind noise, environs of the spot, and such need be a part of the school solution. Instructors need to speak evil as well as school solution.

Ah, but Jim....here's where the rub is: Wind is almost never a "static" force.

When I arrived at the University and started doing stage checks with students in our Warrior airplanes, I was fascinated as these kids tried to land those airplanes in our normally gusty crosswinds, with full flaps.

"Why are you using full flaps?" I asked. "Because that's what we've been taught and that's what the checklists say to do."

"Okay, says I, this one's a freebie. Go around, and try a landing with half flaps." The student did, and it was no big deal at all.

We changed the checklists.

The point being, wind is rarely a constant. Most places and most times, there are gusts, and, the higher the wind velocity, often the greater the gust factor.

Now, first of all, you probably shouldn't be operating, even in ground effect, real close to stall speed. Those gusts are going to cause drag (and lift) to increase and decrease. With full flaps (40 degrees in most Cessnas and also in Warriors), a gust hits, and those big flaps cause a deceleration, and some "Up". If you're really close to the stall, you'll probably stall......which is why we have been told to add half the gust factor to our landing speeds. THat's not much, but it's essential. Of course, many if not most pilots add the entire gust factor, and sometimes twice that in a gusty crosswind.....which can get ugly fast.

So, in Cessnas and Warriors, I raise the flaps to the 20 degree setting in a gusty crosswind. This offers significant reduction in stall speed compared to flaps up, but the flaps don't cause as much drag in the gusts.

As I noted earlier, I view flaps as a tool, just like ailerons, rudder, or any other control surface on an airplane. There are lots of ways to use those tools. Some make life a little easier, and i'm all for that.

But, if you always encounter perfectly static crosswinds, with no gusts, full flaps is fine.

MTV

MTV, I think the difference is in the type of approach and whether power pitch deceleration takes place on short final going into ground effect. Front Range of the Rockys is a pretty gusty place, especially summer mid afternoon. Everywhere I always angled across in crosswind, always used full flaps, always decelerated on short final (only used long final if sent out there for spacing but gave way and entered final angling into wind close in when possible,) and moved the throttle quickly and more than enough and then adjusted as necessary. Up to angled short final was low level cruise. I couldn't see behind and avoided exposing my tail more than absolutely necessary.

Too much technique, in my opinion, has to do more with what others will think and not what works best.

Granted the only passenger was none in single seat, oil man, or student.