To flap or not to flap

[ghostflyer]

I have listern with awe from my learnered peers about clearing a hundred foot fence or trees and Speed to lift off with etc. But , I waited with baited breath looking for answers regarding lifting off on soft sand the best way. With the old engine O-300 it had reasonable grunt[sort of] But I didnt think 10 degs of flap made any difference. So I never used flap. Now with "rocket power" 180hp+ fitted, I wasnt using flap either until I read that someone used flap all the time with a 180 hp fitted..Then I was thinking I would give it a go again
. When I takeoff in soft sand the tail has to be up and away quickly due to the tailwheel dragging in the sand. With 10 deg of flap on a soft surface you dance across the sand a lot earlier and takeoff roll is reduced You have to pick your situation for it being effective. Big cross wind takeoffs .No. Using 20 degs of flap ,about the same as using 10 degs .
My tools of trade ? Its a Cessna 170A[180 HP] fitted with 180 legs and Cleveland double pak brakes .The tires are 8.5 by 6 and run about 20 psi in the sand.

[Bruce Fenstermacher]

Important to note that you have a A MODEL. There is a huge difference in the flaps of the A compared to the B model. Most discussion here in the past has probably centered around the use of flaps on a B model.

It is always good to review what Cessna had to say about operating their aircraft. The A model owners manual reprint we have states for normal takeoff 0° of flaps are used. It says for the shortest takeoff 2 notches (20°) should be used. The performance charts are with no flap and off a hard surface so no help there. It then goes on to say Land and Ski plane takeoff should be made with 2 notches of flaps. The takeoff check list doesn't call for any flaps. So the owners manual is clearly vague but 2 notches under normal situations will be a shorter take off run.

From my experience in an c-145 powered A model 10° will give you a slightly more positive rate of climb and your ground roll will be slightly shorter. I just use 20° degrees because the book says it's the best. Your not operating under a situation the manual covers. Your on sand and you have much more horsepower. I'd do what you are doing and do what you think works the best.

[KS170A]

I have heard numerous times, usually from people who have little to no experience in 170/170A airplanes, that the flaps are next to useless. I could not disagree more! Granted not as effective as the B model flaps, they can mean the difference between climbing above a ridge or sinking into it, especially in high weight/high density altitude scenarios. Even low weight/low DA, I use 2 notches when operating off my home grass strip, but usually no flaps on pavement.

[Bruce Fenstermacher]

Having flown first and for more time with the B model flap, every time I pull A model's on to 50° I think to myself, why did I bother. But they do have effect and I do use them for nearly every takeoff and landing.

[ghostflyer]

Well we tried the 2nd notch of flap or 20deg for a takeoff. I have never tried that flap setting before with this engine. As the tail came up we were airborne . Climbed away very quickly ,however after 200ft you must milk up the flap as the speed isn't increasing as it would normally. Keep trimming the nose down is a must also. My next project is to do a few circuits and bumps with all the flap settings. I would have tried it off the beach today but the tide was in and there isn't much beach left after the big storms we have had. We learn something new every day .

[edbooth]

This is related more to the 170B; In the years we have owned the plane, I have almost never used flaps for take-off. The B models first notch is 20 degrees and it seemed like it induced too much drag. For whatever crazy reason, when leaving out of a short grass runway (in need of cutting) on a warm humid morning on the way to Sun N Fun with three onboard along with food, camping gear various beverages and full fuel, I elected to use flaps. If I were a cat, this would have been one of the used up lives. The takeoff was slow getting started and when it finally lifted off, I was way past the abort point. This particular strip had a stand of tall pine trees off the end, then a county road and more pine trees across the road. The stall warning was beeping steadily, I nursed the plane over the first set of pine trees and because of the nursing, lost a little speed and altitude which made it obvious to me I would not clear the second set of pine trees. I gently turned the plane down the road, below the tops of the trees on each side of the road and just above the power lines (and to this day don't know how I did that). We remained in this condition for a couple minutes until we could climb above the tree tops and start bleeding the flaps off. No one said anything for about 20 minutes after that ! I think if I had that 10 degree notch cut in the flap handle mechanisam like some folks have done it would have come out better. The 20 degrees was just a bit too much for the conditions at the time. I mostly still take off without flaps.

[c170b53]

Ed I'm with you, I never use flaps for T.O. The CS prop is my advantage in that flight phase. I also seldom use greater than 20 degs on landing unless I find myself floating. Again just what I like to do even though I realize my landings are flatter and not as safe as being nearer to land with a steeper approach.

[ghostflyer]

I have the problem that I over speed on the circuit or landing phase and use the flaps as speed brakes (below 100 kts). With a fixed pitch prop (60ins pitch)it's all about energy management . With the engine at idle flaps are deployed on downward leg .(We are restricted by the size of the circuit that we fly due to noise abatement. )I use the 50deg notch on final and engine rpm at 1200rpm and on touch down back to idle. Nearly a perfect wheeler each time . Plus we have some very strong cross winds ,and thus the use of flaps is then a educated guess.

[krines]

I have a 1950 A model and no experience in the sand but close to 1000 off airport landings. I am sure getting a light footing as quick as possible would be beneficial in the sand. The great thing about the A model is not having huge flaps and therefore taking off is simple with full flaps. Mind you I have the 145 engine, with that 180 you have plenty of power to overcome those small flaps. I would not recommend full flaps for obsticle clearance though but by definition there should be no obsticles to clear on the beach. Watch you tube Valdez Fly In video. The technique is no flaps, full power, tail up, apply full flaps and lift off into ground effect. As soon as you get some altitude and speed very slowly retract the flaps. Practice this on good grass as there is alot going on at once. In the sand it may be that as you raise the tail, the wheels will sink deeper into the sand so getting to full flaps quickly will have to be quick to lift them back out. Go to the Backcountry Pilot website there are many great discussions on landing in the sand, actually sounds dangerous as sand texture can vary greatly and you should be ready for anything. While your at that sight check out the post Cessna 170s in the powder- some of the most stunning pictures of 170s on skis.

[N3243A]

I have a 170B with stock engine BUT with an 80-42 prop. The prop may make a big difference here as it allows higher RPM and more HP to develop during the takeoff run. There is no way I could operate off some of the strips and gravel bars I do without popping the flaps at the end of the take off run. I start with flaps set to 20, hand on throttle. Start the takeoff run and advance the throttle and when it is WFO, turn the lock nut tight so throttle can't back off due to vibration (VERY IMPORTANT STEP). I then put my hand back on flap handle which is convernient to grab at Flap 20 setting without looking. Then pop them full down to 40 degrees when the time is right or the end of the strip is close. The right timing for this is in my gut, I can't give you an airspeed number. It is developed thru continual practice. This act immediately pops the airlane up about 2 or 3 feet. Keep it level for a few seconds to gain airspeed and start climbing. Keeping my hand firmly on the flaps, bleed them off slowly all while looking outside and a maintaining a safe climb rate during flap retraction. This is not great for obstacle clearance but is good for short gravel bars where I just need to get up quick and then can fly over the water or rough ground off the end of the strip at low altitude. If I need to clear obstacles then I must just flat plan on needing more runway.

I use this technique for uphill takeoffs on a measured 900 foot fairly rough bush strip at 2000' elevation. Off the end of the strip is a cut bank with flowing water. With 2 men aboard, 2/3 gas, cooler, gear and guns, I pop the flaps at about 800' down the runway and fly off the end of the strip about 4 feet in the air. Without popping the flaps I really don't think I would make it. The performance chart tells me a stock 170B at Flaps 20 will need 38% of 2050 feet to do it. That distance is 780' and does not account for the uphill slope and rough strip/tall grass factor. Again the 80-42 prop is a huge factor here. Doing this is probably not for everybody. Your Mileage may vary....

Bruce

[ghostflyer]

Well you guys now have me in a flap , what do I do ? What speed am I supposed to be doing when at 20deg of flap and about to pop 40deg and is the tail up on the ground run . When taking off on sand or beach My RPM is normally at 2450 and have 20 deg of flap and tail up and 70 kts and it climbs like a home sick angle. When you moving on sand it is all about getting light on the wheels. The tail has to be up as its like a anchor in soft sand . Once airborne the RPM very quickly rises to 2700rpm.

[Bruce Fenstermacher]

Well you guys now have me in a flap , what do I do ? What speed am I supposed to be doing when at 20deg of flap and about to pop 40deg and is the tail up on the ground run .

Be careful, we are now mixing A model flaps ops and B model flaps ops. Totally different systems. They are not comparable.

[hilltop170]

Ghostflyer-
Hopefully, without sounding too much like a smarta**, the only way you're going to learn how to do what you are asking is to go out and try every different configuration you are curious about enough times each to find out what works best for your individual conditions.

That is the way most of us have determined how to fly our planes, you have to spend the time to get the answers. Of course, don't do your practicing at the short/soft/rough/high/whatever risk place you actually want to be proficient for, find somewhere similar with lots of runway length and lots of margin of safety but with similar conditions of roughness, etc.

You'll get to know your plane and be a better pilot. Stock 170s of any model are not Super Cubs and never will be, but they are great planes. They just have their own limitations which demand to be respected and every single one is different. Go out lots of times and have fun learning the edges of the 170 performance envelope. Just be safe doing it and work into it with caution. Always leave yourself an out. These planes will almost always land shorter than they will take off.

[canav8]

Ghostflyer-
Hopefully, without sounding too much like a smarta**, the only way you're going to learn how to do what you are asking is to go out and try every different configuration you are curious about enough times each to find out what works best for your individual conditions.

That is the way most of us have determined how to fly our planes, you have to spend the time to get the answers. Of course, don't do your practicing at the short/rough/high/whatever risk place you actually want to be proficient for, find somewhere similar with lots of runway length and lots of margin of safety but with similar conditions of roughness, etc.

You'll get to know your plane and be a better pilot. Stock 170s of any model are not Super Cubs and never will be, but they are great planes. They just have their own limitations which demand to be respected and every single one is different. Go out lots of times and have fun learning the edges of the 170 performance envelope. Just be safe doing it and work into it with caution. Always leave yourself an out. These planes will almost always land shorter than they will take off.

If no competent Flight Instructor is available, then do what is stated above. Just do not do it with your family or your buddies onboard.

[GAHorn]

Ed, you're no noobie to this site or this airplane and I know you've got plenty of experience and personal familiarity with your serial number....
But the factory pretty well documented that the airplane requires less runway using 20 degrees of flaps for takeoff. If you had not used flaps on that takeoff....you might not still own that serial number. The insurance company likely would have parted it out the week after, because you'd have not cleared the initial obstacle....and the long-suffering while waiting for additional climb would never have occured.

The problem was, I believe, that your heavy takeoff weight and atmospherics for that day....may have been more than 4,000' density altitude. And the performance figures....which we must believe.... specifically warns us not to use flaps above such altitudes.

In any event, having no "control group" of similar takeoffs to compare.... your memory of that takeoff will likely keep you from attempting it again. (We've all probably got such events etched in our memories.)

Hot/Heavy/High is a dangerous combination.