Wing Flaps (Gusty Conditions)?

[jrenwick]

At the Petit Jean fly-in two years ago I had an opportunity to observe the landing techniques of a number of experienced 170 pilots, and I was surprised how many of them raised the flaps immediately after the wheels touched down. As much as my 170 seems to want to fly again after landing (it has a Horton STOL mod), I can certainly see the advantage of doing it. I haven't tried it yet, but I suppose it's about time. It's just another manual skill that we can add to our bag of tricks as advanced 170 pilots -- do it smoothly and in sequence. And don't forget to practice missed approaches!

John

[jrenwick]

Just to follow up on this thread with some new information --

I never did try retracting flaps immediately after landing, and I don't think it's the answer to the problem I mentioned. The problem is the strong tendency of the Horton STOL-equipped 170B to take off again after it's landed, if the winds are even a little bit gusty. More than once my 170 has lifted off while rolling out after being down on all three wheels. An unmodified 170B doesn't have this characteristic; I've owned both.

I've often heard some generic advice that in gusty conditions, you should use a less-than-full flap setting, and increase airspeed by 1/2 the gust factor. I bought into that, and didn't ever question it until recently. I still agree about increasing the airspeed on final, but the Cessna owner's manual recommends landing with full flaps, period. I'm doing all my landings now with full flaps, including with crosswinds, and having much better results. The airplane slows down so fast after touchdown that the danger of becoming airborne again passes very quickly. The 40-degree flap setting seems to give much more drag than lift on a B-model, so that I don't really see any need to retract them quickly upon landing. Leaving things alone until you've cleared the runway is still probably the best advice, IMHO.

John

[GAHorn]

The primary reason to retract flaps after landing is to increase weight-on-wheels for better braking.

If you find the airplane still wanting to fly after touch-down..... you've landed too fast.

[blueldr]

My solution when this problem arises is to fly to another airport where the wind is right down the runway, land, tie down, rent a car and drive home.

[jrenwick]

If you find the airplane still wanting to fly after touch-down..... you've landed too fast.

I guess that's axiomatic. In my case, with the STOL wing, I can three-point it with full up elevator, and it might still try to fly again. Yes, that's because it's rolling fast enough to fly. But the use of full flaps slows it down quickly enough that the danger is soon past. I'm not too concerned about braking effectiveness at that point, because I'm already pretty slow by the time I start braking. I haven't found the runway that's too short to land on. Too short to take off -- that's another matter.

John

[GAHorn]

... I haven't found the runway that's too short to land on. Too short to take off -- that's another matter.

John

The same as a non-STOL C-170... (poke-poke)

[jrenwick]

... I haven't found the runway that's too short to land on. Too short to take off -- that's another matter.

John

The same as a non-STOL C-170... (poke-poke)

Exactly. I believe I can out-climb a stock 170, though, for what that's worth.

John

[Joe Moilanen]

I always dump the flaps on touchdown. To me it is just as automatic in my sequence as pulling carburator heat on downwind. Maybe its a habit I've acquired from landing on my 650' strip. Not that its the right or wrong way, it just works well for me. Everyone's mileage may vary.

Joe
4518C

[170C]

Joe----650 ft strip! You must have been a Navy carrier pilot in another life

[mit]

The flaps on a 48 don't hardly have any effect. I used full in crosswinds. I have run out of aileron's on final, when that happened I just went somewhere else.

[rhymes]

Well.... this topic brings up a real sore spot for me.
I've kept this to myself for the past three months. I'd like to 'fess up, and would welcome input from other 170 drivers.
As a new 170B pilot, I followed my instructor's guidance of routinely using full 40º flaps on landing. Worked great, until the absolutely calm day I came in to land at our 4,150'MSL runway. Lined up on the centerline with 30º of flaps, I decided to pull in that last notch; just to hit my spot.
A sudden gust from the west, strong enough to force me off the centerline over the dirt and scrub brush resulted in my decision to go around and try this one again... Except that our stock 0-300A at this altitude (cool day) wasn't gonna go around with 40º of flaps.
I recognized it instantly, and with full power decreased the flaps to 30º... too quickly! (New pilot, remember.)
We hit that dirt, hard. Bounced, slid, bent the left gear leg (and prop, I later found out.) I still got her back on the runway as I killed the engine and fought the imminent ground loop. Never touched any part of the airframe or wingtip, but my bad day has still resulted in an engine overhaul, gear leg replacement and upcoming belly skin work.
So: While I understand that we could possibly have gone around with full flaps, (and sloooowww flap reduction) do most of you feel that a full-flap approach is a commitment to land? Is going around still an option? (We were obviously real close to touchdown when I tried to balance on the head of a pin.)
Oh yeah: that sudden gust? We live here on the Eastern side of the Sierras and the forecast weather system arrived early. Gusty pre-frontal conditions are common here, and I'm now a bit wiser...
Thanks,
B.R.

[mit]

The 48 and the B are not the same animal. I had a 48 for 10 years, now I have a B and hardly ever use Full 40. I use full 40 to descend but I like just 30 for touch down. On floats it comes down just fine at 30 and a go around is much easier also.

[jrenwick]

The last notch of flaps on a B model will slow the airplane down a lot. That means, if you're not descending quite steeply, you'll have to be ready to add power when you go to 40-degrees of flaps, in order to maintain flying airspeed. If you've done that and kept the speed up, the go-around should go much better. It's a too-low airspeed that commits you to landing; not full flaps on a 170B.

John

[mit]

The last notch of flaps on a B model will slow the airplane down a lot. That means, if you're not descending quite steeply, you'll have to be ready to add power when you go to 40-degrees of flaps, in order to maintain flying airspeed. If you've done that and kept the speed up, the go-around should go much better. It's a too-low airspeed that commits you to landing; not full flaps on a 170B.

John

That is dependent on where your landing some of the places around here you better be as slow as you can go or you need to land somewhere else.

[Robert Eilers]

The proper use of flaps has been a discussion among flight instructors for as long as I can remember. I personally believe it is bad advice and lazy flight instruction to tell a student to always land with full flaps. The more responsible teaching technique is to instruct the student on the purpose of the flaps. Flaps were designed to allow the pilot to change the configuration of the wing to allow for different operations, i.e., a short takeoff, short landing, a step descent without busting Va, canyon turns. When discussing the use of flaps during landing, I find students get the most out of explaining the purpose of flaps (during landing) is to allow the pilot to land the airplane at the slowest possible forward speed. Speed for the landing discussion is ground speed - speed across the ground at touch down. Once the student understands this principle, they quickly learn they can adjust flap deflection based on wind speed acting on the airplane during landing. If full flaps produces a 40 MPH touch down in calm wind, a headwind on landing can produce the same touch down speed and better control effectiveness with less flap deflection. A good demonstration of how the aircraft performance is affected by flaps in high density altitude situations or when surrounding terrain is a factor teaches them to make decisions regarding flap deflection on landing based on a possible go-around scenario. Flap use should never be thought of, or taught as, an all up or all down situation.