How big of a dent is too big??

How to keep the Cessna 170 flying and airworthy.

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Bruce Fenstermacher
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Re: How big of a dent is too big??

Post by Bruce Fenstermacher »

I think the nature of the damage is someplace in the middle of what we think we see in the pictures. Truth is many of us would probably walk past damage on the ramp and think nothing of it. And there really may not be much to see.

My visit to the Grand Canyon was much the same. As we drove up to a parking site and looked in the direction we thought it was, it didn't look like much. But then when we walked to the edge we got a different perspective.
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c170b53
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Re: How big of a dent is too big??

Post by c170b53 »

Looking at the pics, I’ll guess this plane has been in the bush and neglected. The widespread corrosion should be addressed. Can the stab be fixed easily, sure, cherry max’s and filler, fixed so it appears as if it never happened that would take more time and cash.
My mention of putting a ruler in the pic to aid in determining the perspective seems simple but it aids in the interpretation. The closer the pic is taken to an object, the less you can judge dimensions unless there’s another objects such as rivets or fasteners for reference. Same thing judging the size of a defect using a non measuring boroscope whereas measuring is just easy using a boroscope with an phase array tip.
Looking at the first pic, it was a bit difficult to see the skin pulling away from the rivet line, but its there. Further pics from different angles tell the tale.
George is right, inspect the bulkhead attach points for cracks /deformation to ensure the damage was limited to a local point.
Bruce your right, most of us would walk right past it unless of course it was a plane we owned.
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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c170b53
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Re: How big of a dent is too big??

Post by c170b53 »

19-14. NEGLIGIBLE DAMAGE. Any smooth dents
in the wing skin that are free from cracks, abrasions and sharp corners, which are not stress wrinkles
and do not interfere with any internal structure or mechanism, may be considered as negligible damage. In areas of low stress intensity, cracks, deep scratches or deep, sharp dents, which after trim- ming or stop drilling can be enclosed by a two-inch circle, can be considered negligible if the damaged area is at least one diameter of the enclosing circle away from all existing rivet lines.
This is info from the 62 and prior MM, whether it applies is up to debate but in absence of an existing documentation applicable to our planes, it will do as guidance.
The principles are pretty much the same across airframes, its just common sense when you break damage down into its individual components.
As an example; dents in the middle of a panel, the metal has just yielded in a local area whereas in areas where there’s rivets, the structure is more robust and a dent and its size has ramifications to the surrounding structures and the rivets themselves.
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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abushey123
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Re: How big of a dent is too big??

Post by abushey123 »

Alrighty! All the attach points have been inspected. The horizontal is off and now the time for repair starts. Do any of you know where one might find pn 0332128-5? This would be the right inboard leading edge. If I can avoid replacing the whole horizontal that would be best as the engine and mount put me back a bit more than I was expecting. :D :D :D :D :D :D
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abushey123
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Re: How big of a dent is too big??

Post by abushey123 »

Bruce Fenstermacher wrote:Yes, I'd have to look at this damage little closer and likely at least have to repair the leading edge skin.
Screen Shot 2022-03-25 at 6.35.58 AM.png
And if you are wondering what this cable outlet is for, your plane probably had wing leveler installed at one time. The wing levelers of the time used the rudder to level the wings and that was controlled via extra cables to the rudder.
What exactly do you mean by a wing leveler?
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GAHorn
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Re: How big of a dent is too big??

Post by GAHorn »

abushey123 wrote:
Bruce Fenstermacher wrote:Yes, I'd have to look at this damage little closer and likely at least have to repair the leading edge skin.
Screen Shot 2022-03-25 at 6.35.58 AM.png
And if you are wondering what this cable outlet is for, your plane probably had wing leveler installed at one time. The wing levelers of the time used the rudder to level the wings and that was controlled via extra cables to the rudder.
What exactly do you mean by a wing leveler?
An early, rudimentary single-axis auto-pilot.

Contact Air Repair, Inc, Cleveland MS for the leading edge. http://www.airrepairinc.com/L-19-parts- ... large.html
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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c170b53
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Re: How big of a dent is too big??

Post by c170b53 »

Just curious , Guess the dent was close to a rib and it was just straightened once the L/E was removed. Any pics of the stab once the skin was off ?
Jim McIntosh..
1953 C170B S/N 25656
02 K1200RS
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abushey123
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Re: How big of a dent is too big??

Post by abushey123 »

c170b53 wrote:Just curious , Guess the dent was close to a rib and it was just straightened once the L/E was removed. Any pics of the stab once the skin was off ?
I can get some this weekend! Horizontal is all ripped apart in my garage
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GAHorn
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Re: How big of a dent is too big??

Post by GAHorn »

It’s a shame it’s not an A-model…. (the complete horiz-stab from the February Auction is still available.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons. ;)
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jetguy
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Re: How big of a dent is too big??

Post by jetguy »

Hey Bruce! I actually stumbled onto this post but I think you might just have cleared up a mystery that’s been bugging me for years. My ‘55 has those exact same cable outlet fairings but I never knew why they were there. Nothing really in the logbooks that would explain it. I’ve always blamed them on the “MetCoAir” nosewheel kit that some jackass installed back in the 50’s when the airplane was new but, even that never made any sense. Thanks for solving a true dilemma!
Greg Anderson
'55 170B N4316B
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Bruce Fenstermacher
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Re: How big of a dent is too big??

Post by Bruce Fenstermacher »

jetguy wrote:Hey Bruce! I actually stumbled onto this post but I think you might just have cleared up a mystery that’s been bugging me for years. My ‘55 has those exact same cable outlet fairings but I never knew why they were there. Nothing really in the logbooks that would explain it. I’ve always blamed them on the “MetCoAir” nosewheel kit that some jackass installed back in the 50’s when the airplane was new but, even that never made any sense. Thanks for solving a true dilemma!
Greg, at the risk of highjacking the thread, those planes that have the extra slots for the wing leveler cables under the horizontal stab are also likely to have an extra hole in the instrument panel, through which a push pull control, similar to a prop control, was run. This push pull control was used to engage/disengage the clutch of the servo of the leveler system. If anyone would be interested in junk my partner Leroy still has the control cable and servo motor from the system but no electronics to drive it.
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