The International Cessna^® 170 Association

Why would the flap handle on some 170B's have only three detents, with the first one being a very large flap deployment setting? Others have 4 detents providing more gradual flap use. What was Cessna's thinking on this design?

The '52 170B only had 3 flap settings.
20, 30 adn 40 degrees.
Later models (53 and on???) have 4 flap settings
10, 20, 30 and 40.

Swapping out or modifying the quadrant to convert a 20/30/40 to a 10/20/30/40 is a very simple task that an A&P can perform.
There is a drawing of the quadrant that details the 4 cutouts around on the forum somewhere.

The only advantage to a 10 degree setting is you don't have as much pitch change in the plane when removing the flaps after takeoff - if you used flaps for takeoff. With 20 degree flaps on takeoff, I would slowly raise the flaps to avoid this.

I like the 10 setting for slow flight while sight seeing etc. It gives you a reasonable pitch attitude for visibility and lower power setting.

The ten degree setting provides no better takeoff performance than the 20 degree setting, but it's helpful for soft-field ops.

The change came after 53 I have 54 with 3. I think is was mid year 54 you can look in the parts book for the S/N blocks.

It is hard to say from the IPC. But the 10 degree notch may not have come into play until 26505 or 1955.

When my '53 model (sn 25713) developed a slight "hitch" in it's flap system a few years ago, I replaced the quadrant with the later 5-position part.
I used the ten degree setting a few times when departing my grass strip, thinking it would make a big difference.
It didn't. I use the 20-degree setting for takeoff because it gets me off the ground as short or shorter if I'm light, thereby transmitting less vibration/shock to my airframe on rough ground.
For that reason I cannot recommend going to any trouble to convert earlier 4-position quadrants to 5-position.

Seems like acceleration would be improved with the lesser flaps. Also, with crosswinds it just seems like a better flap selection (10).

My 'Timeless Classic' book on page 10 indicates the change happened in 55 between 26505 & 26995.

In strong crosswinds (and paved runways) I use no flaps at all for takeoff, for better directional control and less drift at lift-off.

There used to be a great controversy over whether it was OK to convert early systems to the later system, and whether or not it was a major alteration.
I believe most folks now realize it's a minor alteration (logbook entry only) and blessed by the "authorities" since Cessna's IPC specifies (for the early airplanes) to use the early sector "until supplies depleted".... then to use the later sector.

That was helpful. Thanks. Believe I'll go for the extra notch just for the extra 'arrow in my quiver,' Slow flight situations, and Feel like it'll be helpful in the pattern too. A more gradual slowing.

I will try to find the drawing referred to in the forums, and any directions would be appreciated. Thanks to all.

It's one of the easiest mods to perform as the sector is a one-bolt "drop-in" activity, once the tunnel-cover is removed at the flap handle base.

Here's a link to the drawing: http://cessna170.org/forums/viewtopic.p ... ee+drawing

gahorn wrote:When my '53 model (sn 25713) developed a slight "hitch" in it's flap system a few years ago, I replaced the quadrant with the later 5-position part.
I used the ten degree setting a few times when departing my grass strip, thinking it would make a big difference.
It didn't. I use the 20-degree setting for takeoff because it gets me off the ground as short or shorter if I'm light, thereby transmitting less vibration/shock to my airframe on rough ground.
For that reason I cannot recommend going to any trouble to convert earlier 4-position quadrants to 5-position.

8.00x6 tires would do a better job of reducing the vibration/shock and could be used in conjunction with the 20 degree flap setting

Tim

bat443 wrote:[...8.00x6 tires would do a better job of reducing the vibration/shock and could be used in conjunction with the 20 degree flap setting

Tim

And they would sling mud and gravel up under my wings and all over my tail and water from puddles all over my windshield since they won't fit under wheelpants.

Aryana wrote:Yep, I haven't found a dirt/grass strip yet that my 6.00x6 tires and wheel pants didn't like or couldn't handle. It's amazing how much crap they capture from getting fling all over the wing/horizontal stab. Just my opinion, but I think the majority of big tire folks in my area do it for looks instead of functional neccesity.

If Napolean was a pilot, I think he'd have 850x6 tires.

Are you sure Napoleon wasn't a pilot, I'm sure I flew with him or some of his descendants!