Shortfield Takeoff Technique

Robert Eilers · Post by **Robert Eilers** » Sat Feb 16, 2008 12:44 am

I would like to explore, with those of you who have owned your 170 for a while, short field takeoff techniques. My 170 seems to me to behave peculiarly in the shortfield configuration. I have 40 degrees of flaps, so my first notch is 20 degrees. With 20 degrees my 170 will come off the ground at 40 IAS (assuming my ASI is accurate). The airplane seems to levitate off the ground in a three point attitude. I have to consciously lower the nose to gain airspeed while still trying to gain altitude. The result is I may only be indicating 60 at 50 feet. The airplane seems to accelerate very slowly - I have the 7653 McCauley. I am used to accelerating to Vr , accelerating to Vx and then climbing at Vx - the 170 just seems to perform oddly with 20 degrees of flaps. Am I the only that feels this way?

voorheesh · Post by **voorheesh** » Sat Feb 16, 2008 2:44 am

With your flap settings you probably have the B model which should provide for additional lift with 20 degree setting. I fly an A and practice holding the brakes, yoke full aft, full power then gently release brakes and be ready with some right rudder. As speed builds, gently raise the tail (but keep it low) and let the airplane fly off when it is ready. As you leave ground effect let the nose come down slightly and achieve the desired speed. In an A it doesnt seem to matter whether the flaps are used or not but I typically use the first notch and I retract it when the climb is stable. I have a Horton STOL kit which seems to help get it off pretty good. I don't pay much attention to airspeed until I'm out of ground effect and even then I try and fly an attitude that delivers the right speed. I would expect a B model to out perform the A because of the flaps.

mit · Post by **mit** » Sat Feb 16, 2008 4:57 am

i'm usally showing 0 on the airspeed when I get airborn

buzzlatka · Post by **buzzlatka** » Sat Feb 16, 2008 6:10 am

Same here,

I have a 52b with the same prop. On takeoff I use one notch of flaps and get the tail off the ground as soon as possible. I then try to hold it a few inches off the ground. After a few seconds try and pull the airplane airborne by pulling the tailwheel back to the ground. The timing of when the airplane wants to get airborne is soley a function of having tried this many times. Practice Practice Practice. Most of the time there is zero IAS and the airplane climbs like and elevator in the 3 point attitude. I agree with you that the 170 seems to take a while to accelerate a few knots to where you can clean up. I typically wait until about 40 ias and then gradually lower the flaps while accelerating. Going from 0 airspeed with 1 notch of flaps until Vx clean does seem to take a while.

Post by **GAHorn** » Sat Feb 16, 2008 7:30 am

Allowing the tailwheel to come off the ground and holding it there until the airplane lifts off... while a fine technique...and one that I usually recommend.... will, in a short-field/soft-field takeoff, result in longer takeoff ground runs. Keeping the tail on the ground and immediatly as the airplane lifts off in the 3-point attitude, lowering the nose slightly will result in shorter takeoff ground rus.

ak2711c · Post by **ak2711c** » Sat Feb 16, 2008 8:43 am

If you are on a soft field the last thing you want is your tail on the ground digging a corn row back there. That is like dragging an anchor.
If you have a stock motor use 20 degrees and tail low til lift off. Then stay in ground effect until you reach Vx, once your obstacle is cleared bleed your flaps off. If you don't have an obstacle to clear then bleed your flaps off in ground effect and climb out at Vy. With the bigger motors there is enough extra lift created by the prop blast that you can get off considerably shorter by starting with 20 degrees of flaps then pulling full flaps on your take off run. After lift off stay in ground effect and bleed your flaps down to 20 and follow the above procedure from there. This takes a lot of practice to learn the feel of when to pull it off and should be practiced very carefully. This technique does not work with the stock motor though. Good luck and like buzzlatka said practice practice practice.
Shawn

N9062A · Post by **N9062A** » Sat Feb 16, 2008 11:23 am

I have a stock 170A. My best run is to push the tail up asap and hold for two seconds. Relax the yoke back while pulling in all the flaps. Keep the nose low , build airspeed and slowly bleed off the flaps. I've tried the 3 point take off but that requires flying speed. This method seems to get you up in ground effect.

flat country pilot · Post by **flat country pilot** » Sat Feb 16, 2008 1:36 pm

Keeping the tail on the ground and immediatly as the airplane lifts off in the 3-point attitude, lowering the nose slightly will result in shorter takeoff ground rus.

George, How does keeping the tail on the ground shorten the take off run?

Having a B model and 4 notches of flaps, I put one notch of flaps in until the tail wheel lifts and then add the second. This seems to get the plane out of the starting blocks a bit quicker. I haven't taken any field measurements so this might be a feel good thing. But it feels good compared to starting with 20 degrees of flaps. The plane leaves the ground at about 40 IAS.

However, I don't like messing with extra adjustments while in the take off run or landing roll out because this is where ground loops occur.

What do you guys consider a short take off run?

What do you consider a soft field?

1280 lbs empty weight, B model stock engine, Pilot, full fuel, no wind and freshly mowed grass - 500 feet plus or minus? Not a soft field and haven't measured it.

If you have a stock motor use 20 degrees

Shawn is right about this and I think it is stated in the owners manual/POH(what ever you call it). A stock engined 170 does not climb out very well with 30 degrees of flaps, IF AT ALL.

Bill

Post by **GAHorn** » Sat Feb 16, 2008 4:21 pm

flat country pilot wrote:
Keeping the tail on the ground and immediatly as the airplane lifts off in the 3-point attitude, lowering the nose slightly will result in shorter takeoff ground rus.
George, How does keeping the tail on the ground shorten the take off run?...

Bill

I was only intending to point out that raising the tailwheel ... lowers the angle of attack ... reducing the lift and lengthening the takeoff run before lift off occurs. I was making the comment in an effort to discourage lifting the tailwheel any higher than necessary to reduce it's drag thru the grass/mud/sand/whatever.

I was also pointing out that I usually recommend the tailwheel off the ground (a tailwheel low takeoff attitude) ... which is what the factory also recommends.

At some time I once posted an observation I'd made on how this airplane has a natural tendancy to fly. If the elevators are held nuetral (instead of either full back or forward) ... as the airplane accelerates the tail will naturally lift itself. If slight backpressure is applied at this point a short-field takeoff will occur. (The shortest takeoff will occur with takeoff flaps also applied.) If instead, aft-yoke or up-elevator is used, then drag is slightly increased because of the tailwheel on the ground and induced drag from the out-of-alignment control surfaces. How much drag is created by the tailwheel on the ground is dependent upon how soft the field is. A hard/dry surface has the least and is probably negligible.

If forward yoke/down elevator is used in an effort to raise the tail prematurely, then excess induced-drag is created by the tail and excess friction/drag is created by the added weight on the main gear. Any kind of created drag will extend the takeoff.

If crosswinds permit a relaxed or nuetral elevator... the tail will fly itself off the ground without extra induced drag, thereby reducing the drag produced by the tailwheel's interaction with the surface. As soon as that tail is off the ground, if the pilot can sense that moment, then a slight back-pressure on the yoke will apply any further lift gained by acceleration towards the effort of lifting the entire airplane. (Shoving the yoke forward lifts the tail further creating unnecessary induced drag, and simultaneously reduces angle-of-attack and reduces lift produced by the wings.)

It's a fine point I was making, and it deserved more attention that what I previously gave in that short quote of mine. Sorry not to have been more clear.

AR Dave · Post by **AR Dave** » Sat Feb 16, 2008 5:12 pm

George, How does keeping the tail on the ground shorten the take off run?

By maintaining a greater angle of attack. The airplane will fly at a greater angle of attack than it sits on the ground. This is how 8.50 tires shorten a takeoff run. Even with the tailwheel off the ground, the angle of attack is considerably more with the larger tires.

AR Dave · Post by **AR Dave** » Sat Feb 16, 2008 5:24 pm

I know a skilled pilot that will use one wing to indicate take off timing.

buzzlatka · Post by **buzzlatka** » Sat Feb 16, 2008 5:25 pm

If I am trying to take off short on pavement (not sure why I would try this) I just leave the tail on the ground and like george said, It just takes right off in the 3 point attitude.

TRIM. One thing I noticed is that my takeoff trim position was not enough. I needed more nose up trim so I didn't have to hold the yoke back on takeoff. Removing that artificial force helped a lot in flying the 170 off the ground SLOW.

I think pulling the flaps in at the last minute probably works for some, but I did a lot of testing on soft grass and dirt for my short strip. What I found is that starting the takeoff roll clean and then popping in the flaps didn't give me any appreciable increse in performance and was hard for me to do. My strip is very soft and bumpy. I am bouncing around hard on the roll trying to keep the tail from bouncing around. I use full forward elevator to get the tail dug out and then really concentrate on keeping it low without hitting the dirt again. Also I like the fact that on the start of the roll the prop blast hits the flaps and gets the 170 light on the gear immediately. This helps me accelerate in the soft ground.

I think the tail low 20 degrees of flaps is the common method. The other little details are dependent on preference, and application.

Even after I finally got into my short strip I modified my techniques a little in order to increase my payload on the way out.

I would like to say I am smart enough to figure all of this out on my own but AR Dave helped me a little with technique. He seems to be pretty good with the short field stuff.

Robert, Drop me a PM if you want to get the 170's together on some dirt or grass to trade some tips.

AR Dave · Post by **AR Dave** » Sat Feb 16, 2008 5:54 pm

Ditto here Buzzlatka - most of my thinking was picked up from other pilots!

SteveF · Post by **SteveF** » Sun Feb 17, 2008 11:16 am

Above is an example of why this is such a fantastic organization.

Pilots and mechanics who share their vast storehouse of knowledge and experience with everyone on these forums!

Many of the discussions here have improved my flying and the maintenance of my 170.

THANKS !!

Robert Eilers · Post by **Robert Eilers** » Sun Feb 17, 2008 3:32 pm

AR Dave,

What do you mean "use the wing" to determine takeoff timing?

The International Cessna 170 Association

Shortfield Takeoff Technique

Shortfield Takeoff Technique

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