So I was in Idaho last week and tried some climb outs with flaps on and some with flaps off. I noticed most cub drivers were taking the flaps out shortly after lift off, but in the C180 we see better climb keeping them in. For high density altitude flying what are your opinions for flap use on take off and climb out?

With my Stinson I usually clean up quite soon after takeoff and climb out clean. If I leave flaps on I tend to over heat and it doesn't really climb any faster just steeper.

In most airplanes, they help most getting up into low ground effect. After that there is no reason not to use them going away from destination initially. After high DA takeoff, in low powered aircraft, finding natural lift or down drainage is more important.

My C180 POH says retract flaps as soon as practicable and to climb without them. 1956.

I observed a lot of the 180/185 drivers taking off without them this past weekend at JC. Anecdotal evidence.

Not scientific. On mine, at high DA at least, I seem to indicate better climb by accllerating to 90ish and no flaps to establish better climb. Defininatley worse with two notches versus clean.

Bill

hummm...each bird is different i guess...my 182T works best for an agressive climb with 14 deg. flaps..but it does have vg,s and diff leading edge etc...

In mine I get around the same climb in distance with 1 notch vs none.. but 1 notch on these small flaps is barely anything.. I grab full flaps to rip it off the ground at 40ish mph and then leave it in ground effect until flaps up and 60mph then into a climb. Seems to be about the best for getting off really short and climbing good in a short distance.

soyAnarchisto wrote:My C180 POH says retract flaps as soon as practicable and to climb without them. 1956....

Yes. Sort of.

Per page 2-4 in the 1957 owners manual: "if no obstacle is ahead, climb out with flaps up at 100-120mph wih 23"/2450rpm. If maximum climb performance is desired, use full throttle, 600 rpm, and 90 mph IAS at sea level." and "To climb over an obstacle with flaps up, the best angle-of-climb speed (70mph IAS) should be used."

However, per page 3-6: "if 20 degree wing flaps were used for takeoff, they should be left at 20 degrees until all obstacles are cleared. To clear an obstacle with wing flaps at 20 degrees, the best angle-of-climb speed (60mph IAS) should be used."

At high density altitude and underway, we don't want the flaps impeding rapid transition from descending air to rising air. In the mountains, the difference between rising and descending air makes far greater climb difference than flaps. Using flaps in rising air and dumping them in descending air would be technically correct, but pitching up in rising air and pitching down in descending air is more rapid and effective.

Attempting climb, with or without flaps, in descending air is defective and dangerous.

Climbing can be summarised as a battle between drag + gravity, vs thrust + lift.

The wing produces a lot less drag with flaps retracted, so more thrust is available to combat gravity.

Flaps also increase the effective camber and lifting coefficient of the wing, but most flaps are designed to create a lot more drag in the process. So while flaps do increase specific lift, I would think they produce a greater increase in drag in most aircraft. This would be especially true for STOL aircraft.

So in most cases, the climb is faster (Vy) and more efficient with flaps up. Because flaps also increase effective camber, perhaps some aircraft *might* be able to get a better Vx with flaps extended, but that is speculation. I was always taught to retract flaps ASAP to get best climb (Vy).

I believe most airplanes will have better L/D (lift over drag, best glide speed, max aircraft efficiency, whatever you want to call it) with the flaps retracted.

IN GENERAL, deploying the flaps yields a lower L/D, which by definition means that any increase in lift is offset by a larger increase in drag.

So if you are lucky enough to have a large excess of power at high DA, it is possible that the power can overcome the drag, and you can take advantage of the extra lift from moderate flap deployment. But for "normal" airplanes I'm guessing that having the best L/D is more important.

I leave the flaps extended as long as practical for the given departure. Getting up and over a 150-300 foot obstacle I leave them in until clear. Departing a place with no hazards I retract them much sooner. Departing JC I leave them in until I'm over the tree tops mid field. I also don't go straight down the runway. I climb high and fast and skirt to the right over the trees by mid field allowing me to make it back t the runway quicker if needed. Flaps extended help this. Retracting them sooner would mean you must go further down the runway for climb out.

AKT

I normally always use flaps for takeoff. Lower them if I am in ground effect to help gain more speed and use that speed to climb out. I still have the flaps(money in the bank) and will use them if needed. If I am at 30ft AGL in the mountains and want to climb over a ridge I will some times add 1/2 flap to give me some more lift. If you can keep CHT temps under control a climb with partial flaps should be faster than without.
DENNY

aktahoe1 wrote:I leave the flaps extended as long as practical for the given departure. Getting up and over a 150-300 foot obstacle I leave them in until clear. Departing a place with no hazards I retract them much sooner. Departing JC I leave them in until I'm over the tree tops mid field. I also don't go straight down the runway. I climb high and fast and skirt to the right over the trees by mid field allowing me to make it back t the runway quicker if needed. Flaps extended help this. Retracting them sooner would mean you must go further down the runway for climb out.

AKT

DENNY wrote:I normally always use flaps for takeoff. Lower them if I am in ground effect to help gain more speed and use that speed to climb out. I still have the flaps(money in the bank) and will use them if needed. If I am at 30ft AGL in the mountains and want to climb over a ridge I will some times add 1/2 flap to give me some more lift. If you can keep CHT temps under control a climb with partial flaps should be faster than without.
DENNY

I'm in this camp. I don't have my wagon anymore but I always found the climb with 10-20 degrees flaps felt much better than without. Probably a little harder on the flap tracks and mechanisms with the higher power settings on takeoff and climbout, but worth it when you need to climb like a scalded cat. Sure you're slower if the donkey quits, but the stall speed is lower too and you're closer to the area you just departed from in case its the only forced landing spot around. One way to look at it anyways...

bart wrote:....I don't have my wagon anymore .....

What?

My S7 has two notches.
In standard situations I pull all flaps to get off of the ground and then dump them gradually.
Loaded up at gross weight at high density altitude 1 notch is good for max climb--especially if trying to do it at non-max RPM like 5000 on a hot day to keep that precious engine cool.
Story time:
On our second attempt we departed Picabo, ID and had to immediately head for the ridges to the north to use them to climb up to 8000'.
It took an hour going back and forth. I would dump the flaps and burn a little altitude going downwind to keep cool.
After we made some altitude, we had to bump up to the next mountain ridge. It cost us 1000 foot to get there but it all worked out and soon we were in the cool air with max rpm and no flaps...all the way to Wyoming.
Yesterday we had to do it to a lesser extent in New Castle, WY.
It's nerve wracking. Sometimes I don't use a whole notch and just squeeze a little flap to bump over a ridge.
All flaps in those hot desert mountains will not help climb unless you need to bump over something as a last resort. It's good to know that last notch is there if you have to put it down and ease the pain.
-------But sometimes-------
When I'm loaded light and can go balls to the wall, full flaps are handy for a quick 500' climb.
-----Other stuff------
We departed Tok this trip with full flaps and were gaining about 1 foot per minute. We were facing the 30mph wind but it was shoving us down a bit even though the little mountain was miles away. There was no way I was dumping any flap in that situation until like 300' agl.

Too many folks here are mixing best rate with best angle.

Best angle is what will get you up to a specific height above takeoff in the shortest forward distance. For that task, in a Skywagon, I would generally (as in most always) use some flap. How much? Depends on the mods. For example, Robertson wants you to use a LOT of flap for obstacle clearance. With a Sportsman, I'd use 20 for takeoff and either leave them there or reduce to ten degrees. On a stock wing I'd use 20 for takeoff and leave them alone till clear of the obstacle.

No offense intended, but other makes and models generally have different airfoils, flaps, etc. Read the manufacturers recommendations for each airplane.

MTV

I use one notch on my S7s, often. Like the other day in Montana slow flying low to the ground at 9 K, or when dead stick soaring, for sure. Never in trying out climb sink, I clean it up and go faster to get out of that ASAP. Only time I use full flaps, unlike Swingle, is last thing before landing. Going to full flaps is also my thing that means now is the time to really pay attention as a landing is eminent! Half flaps is play time.

The question for me is when do I not use flaps. Got flaps for takeoff, climb, cruise (just a wee little bit, depending on cg), steepish turns, and landing.

Headoutdaplane wrote:The question for me is when do I not use flaps. Got flaps for takeoff, climb, cruise (just a wee little bit, depending on cg), steepish turns, and landing.

Exactly. The Beaver on floats really likes just a bit of flap lowered to level the airplane in cruise.

As noted, look at the flight manual for your airplane. Lots of different airfoils and powerplants out there....and thus a lot of variability.

MTV