The International Cessna 170 Association

Well, I made it through my first annual with flying colors... almost! I bought my 170A at the end of last year and couldn’t be happier. At the initial inspection, I noted that the flaps were both hard to pull from the inside as well as outside. I figured it was okay because stiffer springs meant less worry about tailwinds moving the flaps. It was after the purchase that I learned of the small latches that are meant to be a gust lock on 170A’s. Mine were disconnected.

I got the gust locks back operational but at annual realized that my flap springs were still so strong that they put a bind on the latch bracket when at the 1st and 2nd notch. The bracket is only riveted to the passenger side of the tunnel and twists under the load at that angle. I can only imagine the load when flying and the air is tensioning the cable also!

I have used a fish/baggage scale to measure the force needed to lower my flaps when on the ground. With a hook at the top of the handle (right below the button), it takes 33 lbs of force 90 degree to the flap handle to get initial movement of the flaps. The force lessons as the handle is pulled further.

Looking into the wings, I can see that my springs on both sides are stretched some when the flaps are full up. By shape and size, they appear to be factory springs, but no promises. I believe I can put spacers behind the spring tab where it is riveted through the spar to lessen the spring tension with the flaps full up and thus decrease the spring force.

My question is how much should I decrease the spring deflection with a spacer? Could some of you measure a flap handle force on your 170A’s and report back?

Thanks in advance for any and all help. I apologize for the long post but wanted to provide every bit of information I could.

I was informed that the flap handle should have no more than 22 lbs of force to move handle initially and then 18lbs. My flap springs either came from aero Home Depot or aero Lowe’s . Cost was a staggering 87 cents each. [this was over 10 years ago] Couldn’t buy springs from anybody when rebuilding my aircraft . Coated them in LPS3 when installed and have not had any problems since. I “think” Cessna quoted me $83 dollars each on back order.

jklaerner wrote:Well, I made it through my first annual with flying colors... almost! I bought my 170A at the end of last year and couldn’t be happier. At the initial inspection, I noted that the flaps were both hard to pull from the inside as well as outside. I figured it was okay because stiffer springs meant less worry about tailwinds moving the flaps. It was after the purchase that I learned of the small latches that are meant to be a gust lock on 170A’s. Mine were disconnected.

I got the gust locks back operational but at annual realized that my flap springs were still so strong that they put a bind on the latch bracket when at the 1st and 2nd notch. The bracket is only riveted to the passenger side of the tunnel and twists under the load at that angle. I can only imagine the load when flying and the air is tensioning the cable also!

I have used a fish/baggage scale to measure the force needed to lower my flaps when on the ground. With a hook at the top of the handle (right below the button), it takes 33 lbs of force 90 degree to the flap handle to get initial movement of the flaps. The force lessons as the handle is pulled further.

Looking into the wings, I can see that my springs on both sides are stretched some when the flaps are full up. By shape and size, they appear to be factory springs, but no promises. I believe I can put spacers behind the spring tab where it is riveted through the spar to lessen the spring tension with the flaps full up and thus decrease the spring force.

My question is how much should I decrease the spring deflection with a spacer? Could some of you measure a flap handle force on your 170A’s and report back?

Thanks in advance for any and all help. I apologize for the long post but wanted to provide every bit of information I could.

Congratulations on getting an A-model…and also on figuring out this problem!
However, any home-made solution to the issue will not likely have a basis of approval …. while obtaining the correct springs from Cessna will.

ghostflyer wrote:I was informed that the flap handle should have no more than 22 lbs of force to move handle initially and then 18lbs. My flap springs either came from aero Home Depot or aero Lowe’s . Cost was a staggering 87 cents each. [this was over 10 years ago] Couldn’t buy springs from anybody when rebuilding my aircraft . Coated them in LPS3 when installed and have not had any problems since. I “think” Cessna quoted me $83 dollars each on back order.

Thats the number I was looking for! Any idea where this 22 lb. number came from? General consensus is a sufficient answer for me.

As stated, my springs appear to be original Cessna springs, in terms of shape and design. Does anyone know the “spring constant” of Cessna springs so that I could check them if I removed them from the plane? (Spring force = Spring constant x spring deflection)

GAHorn wrote:Congratulations on getting an A-model…and also on figuring out this problem!
However, any home-made solution to the issue will not likely have a basis of approval …. while obtaining the correct springs from Cessna will.

Thanks George! At this point my mentioned solution was just a thought. I still want to confirm that I have a problem and get others to provide flap handle force numbers. As I mentioned, the springs on my 170 appear to be factory original in size and shape.

I can pull them out and measure the undeflected lengths and then the amount of deflection under a known force to get the associated spring constant. I just don’t have access to spare factory springs to get these numbers from. Any help on the physical spring characteristics would be appreciated.

Recieved a heap of information from Harry Delicker at Porterville,California . Unfortunately Harry has passed on. He had so much knowledge and could he talk . He told me about the flap settings and spring tensions. He also showed me a illegal mod to do to the flaps on the A series . One was to cut a extra notch on the flap ratchet for 10 deg and to rivet a strip on the trailing edge of the A series flap to make it larger by about a 1 1/2 inches. Only have seen one aircraft like that in Fairbanks . Do not know the legality of that one. I haven’t done those mods as I do not really require the extra performance .