The International Cessna^® 170 Association

I went out today and did my version of a "BS eliminator" flight. I did over 15 T.O. & landings to a full stop in my stock engine stock wing C-170A with 6.00-6 tires and Cleveland single-puck brakes. I had never done this exact senario before and it both confirmed what I had previously found to be true and surprised me in other ways.

The conditions were OAT 85°, 1700'MSL, paved runway, 30° steady crosswind from the left at 10mph, one person, 28 gal down to 22 gal gas, 4 seats, and no other payload in the plane.

On each takeoff, power was set to full throttle, brakes held until max RPM, then released. Flaps, trim, and method of lift-off were varied.

I have a helicopter airspeed indicator that starts at 10mph indicated and climbs at 5mph increments. 50mph is at about the 4 o'clock position so lots of low speed resolution. The plane will fly at about 35mph indicated, whatever that really is with all the built-in errors, but it is repeatable and indicates the plane will lift off in ground effect (but not climb) well before the white or green arc starts.

Basically what I found was that with the stock C-170A, I can lengthen a take-off run with poor technique but no matter what I did, the best takeoff runs were within 50' of 600' (three landing lights).

The smoothest and shortest run was with the elevator in trail, trim set to just lift the tail, two notches of flap, hold pitch attitude with elevator when the tail just starts to lift, let the plane fly off when it is ready. Anything else lengthened the run.

- No-flaps lengthened the run.
- Four notches flap lengthened the run.
- Holding the tail on the ground until the plane flew off lengthened the run.
- Trying to horse the plane off early lengthened the run.
- Starting with no flap then pulling two or four notches in just after the tail came up did not shorten the run.
- Lifting the tail with the elevator, with or without flap then pulling back on the elevator when airspeed started climbing did not shorten the run

Since I usually try to fly smooth takeoffs and stabilized approaches, I'm sure I was not at optimum proficiency in trying to perfectly time jerking in flaps and horsing the plane off the ground (and neither would anyone else that doesn't do it every day). So I think the exercise was fairly representative of the performance that can be expected under those conditions.

Approaches were flown at 55mph with full flaps, airspeed was held just above the bottom of the white arc although the plane will fly a little below the white arc with power. Landings were all wheel landings and stopped in about the 600' range from touchdown with heavy braking. I'm not a big fan of dragging the plane in with power then chopping it. I can hit my spot consistently much better, brake harder, see over the nose better, crosswind or not, with a wheel landing. This method showed I can land in the same or less distance than the takeoffs and I'm carrying a little safety margin by not being behind the power curve. Of course, considerable changes would have to be made with a soft runway and that's another whole discussion.

I believe the stock plane does not have enough power to horse itself off. It must patiently be allowed to build airspeed until the wing makes enough lift then it will fly itself off. With more horsepower it would accelerate faster and some of the short field techniques would probably work better.

I'm satisfied with the stock engine performance. The stock plane will carry gross weight, take off in about 1000', climb about 500fpm at std conditions, and cruise on 7.2gph at 110mph. That's good enough for me.

It would be interesting to see how some other 170A's compare in performance. How about it guys? Today was a lot of fun and I re-learned a bunch about my plane and its performance.

Big flaps on the 170B will no doubt improve performance but it remains to be seen how much.

How about one or all of you 180hp Lyc O-360 or 210hp Cont IO-360 or 220hp Franklin guys go out and try the different things and see what happens?

Everybody has their own ideas on what works best and they're entitled to them. I found out what works best for me in my airplane and that's what I have and will be using. Only two things count in bush flying, either you make it or you don't. Everything else is just opinion.

Thanks Richard!

What does "horsing the plane off the ground" mean? It would be really nice to get that kind of input from fellow members with more powerful engines.

My engine is a bit underpowered, that's why I'm looking for a new one, but behaves pretty much the same at T.O.'s and landings. I have to really measure the difference, but I would say it takes off a little past 600' with one notch of flap.

You can tell a difference during climb and cruise though. It climbs 500 fpm at 70 kts if MCP is applyed. The cruise I feel more comfortable with is at 2200 RPM and 80 Kts, because it keeps noise levels low and it's really smooth. At 2400 RPM it will do 90 Kts, but it gets too noisy.

Take care,
Pedro.

wenetz wrote:Thanks Richard!

What does "horsing the plane off the ground" mean?

Well, in a stock 170, it means pulling back on the yoke multiple times to try to get it to fly before enough lift is being generated, thus increasing the drag, extending the takeoff roll, and more often than not running off the end of the runway if it is at all short

Not that I have any experience in this area...

Pedro, just to confirm something for you, ... the recommended climb power setting for the standard engine is FULL power until reaching the desired altitutde. Maximum Continuous Power (MCP) is 2700 RPM or Full Throttle, whichever is less.

Richard/futr_alaskaflyer-
Thanks! That's exactly what I meant by "horsing". It's a real frustrating exercise.

wenetz-
I agree with George on power settings. In my opinion, you're really not doing the engine any favors by running it below normal cruise. Lower power tends to allow combustion products/lead deposits to build up causing sticking valves and fouled plugs. The engine was designed to make full TBO at rated power. Lots has been already said about this subject but the bottom line is I think your engine will do better with 2450 rpm leaned at cruise and full throttle for all climbs. I also don't throttle back to descend in an effort to capture airspeed lost on climbout. But, to each his own.

When my engine was torn down for overhaul with 1750hours since the last O/H, the lower end was still in good condition so running it at 2450rpm did not hurt that engine. Of course the cylinders were worn out and were replaced but that was expected.

Your engine is probably producing full power unless you know of some definite defect such as burned valves or stuck rings. Continental did an experiment years ago where they REMOVED the rings from an engine then ran it on the test stand dyno. It used oil like crazy but made RATED power.

Pedro, check your prop. From your RPM description it sounds like you have a standard or perhaps cruise prop which are 76/53 and 76/56 respectively. Having your prop re-pitched to to a climb prop will give you the best short field performance increase for the money you spend. If you can have the prop re-pitched for a reasonable cost to a 76/51 I think you will be pleasantly surprised at the take off and climb improvement, the motor should spin up to about 2500-2550RPM on take off and climb. It cost me $150 US (back when the dollar was worth a bit more) to have mine repitched, balanced, and they dressed up the leading edge.

I had a 76/51 on mine with the stock motor, and I also had a float plane prop on it 76/48. The float plane prop was great for take off and climb, but my cruise was only 85-90mph indicated. With the 76/51 my cruise improved to 100-105mph indicated.

I suggest trying that before you spend a bunch of money on bushwheels or similar tire solutions that cost much more. Bushwheels are cool but remember they weigh a LOT more than regular tires and they will wear out fast on pavement, they cannot be retreaded so you have no choice but to throw them out when the rubber wears off.

Another suggestion to shorten your take off on rough fields is to make the plane lighter. You can take 28-30 pounds of weight off the plane by removing the rear seat, and that only requires some patience and the time to remove four bolts. Ok actually you have to also remove one of the arm rests and probably one of the front seats to get the rear seat out the door.

I've landed mine on a bunch of dirt strips and one of them is fairly rough with 800-6 main tires. Like someone else said if you can drive a car across it at about 40mph (about 50kph) without to much trauma then you will probably be fine. Holes and ditches can really ruin your day though.

The best thing to do is spend some time on foot looking at your landing sites very carefully before you try to take the plane in there, it's just to hard to see stuff from the air and the people who do judge new ground from the air know they risk smashing the plane when they land. The 170 will do just fine as long as you don't assume it will do things that it won't. It will never be a supercub, but on the other hand you can't put three people and some bags in a supercub and enjoy a summer flight down the coast.

hilltop170 wrote:I went out today and did my version of a "BS eliminator" flight. I did over 15 T.O. & landings to a full stop in my stock engine stock wing C-170A with 6.00-6 tires and Cleveland single-puck brakes. I had never done this exact senario before and it both confirmed what I had previously found to be true and surprised me in other ways.""



"" Everybody has their own ideas on what works best and they're entitled to them. I found out what works best for me in my airplane and that's what I have and will be using. Only two things count in bush flying, either you make it or you don't. Everything else is just opinion.

RICHARD, THERE IS A BUNCH OF GOOD STUFF IN BETWEEN THE FIRST PARAGRAPH AND THE LAST ONE. WOULD YOU POST THE WHOLE THING OVER IN THE THREAD TITLED "Shortfield Takeoff Technique" ?

One thing that will help you on your short field take off performance is a SeaPlane Prop. It will hurt your cruze speed but does make a differance in short field take off.

Bill