Cowling Latch Shearing the Rivets

[JackHart]

Hello,
As a new owner of a 52 170B, with a 180hp, I would like to hear what other members/owners have done in the following situation:
As I was entering base at my local airport, my cowling on the left side decided to come loose at the two latch points and imitate a bedsheet!
Do any of you have any ideas for keeping my two left side latches closed, beside the wingnut that I currently have in place over the latch.
The actual latch on the lower cowling is operable, it's the top "catch" that has broken at the rivets.

Thanks in advance for your thoughts and help,
Jack
N2354D

[jrenwick]

Years ago I owned a 170 with the older style cowling, and I seem to remember it had a Dzus fastener or similar on each cowl latch lever (part # 0452110) to hold it down. My memory of this is fuzzy, and it could have been a 10-32 screw fastened through the cowling and projecting outward through a hole in the latch lever, and drilled to accept a safety pin to keep the latch lever closed.

Isn't there something in the association's "170 book" about this? (Mine is at the hangar, so I can't look at it right now.)

[JackHart]

John,
Thank you for your reply. I'll check the 170 book and look forward to fixing this issue.

Jack

[GAHorn]

One of the slickest mods for this latch is the "Dip Davis" mod.
It installs type "V.I.C.C.L." type cowl latches. (This completely removes the existing latches, and in their place, installs a solidly, smooth plate containing the female socket to a "Camloc" and an upper strap with the male, phillips-head Camloc. If the instructions are followed, (detailed drawing accompany the STC, as well as instructions, etc.) this will end up looking like Cessna should have made it to begin with. It does not preclude the airplane from being returned to the original configuration should it be desired in the future, with very little effort. (Merely drill out a few rivets and replace them.

STC # SA01139CH
W.D. "Dip" Davis
411 Pawnee Trail
Marengo, IL 60152
815-568-6811

email: birddr@mc.net

[Jr.CubBuilder]

Thanks in advance for your thoughts and help,
Jack
N2354D

Here's some thoughts Jack.

Somewhere in here I posted a picture of what happened to my cowl, you were lucky it happened in the pattern my incident happened at 130 and scared the *^$# out of me.

I still have to get/make a third set of cowl doors for mine as the replacement doors are a pooched attempt by a mechanic with very poor craftsmanship, and I've got the DipDavis latches to go on it. However I will be looking at adding some additional measure of retention. With the conversion to the 180hp the cowl changed to a pressure cowl. If you aren't already aware, the origional setup on your plane included a sub cowl pressure box that was underneath your outside cowl doors. That handled all the air blast, while the outside door just sat there.

You can probably just have the top catch riveted back in place, but I would suggest at the very least considering something to retain the latch lever in the closed position. My latches were in fine shape, but the mechanic that did my motor conversion only clearanced the exhaust pipe by .25 inches, and it was buzzing the cowling, I am convinced that helped the latch vibrate off the spring clip.

[GAHorn]

...
Somewhere in here I posted a picture of what happened to my cowl, .....

[JackHart]

Jr. Cub Builder,
Thank you for the insight and story regarding your cowling issue. Your information was very helpful.
Thanks again,
Jack
N2354D

[hilltop170]

Jack-
I read a report from a D.E.R. who was trying to get FAA approval to convert a C-170 cowling from the airbox style to pressure cowling. It was a detailed engineering exercise. One conclusion made was in order to convert from the airbox style to pressure cowl, the Dip Davis STC must be installed.

From your experience, it looks like a good call.

[JackHart]

Richard,
Thanks for you note. It looks like the Dip Davis STC is the way to go.

Again, thank you for your insight,
Jack
N2354D

[GAHorn]

Jack-
I read a report from a D.E.R. who was trying to get FAA approval to convert a C-170 cowling from the airbox style to pressure cowling. It was a detailed engineering exercise. One conclusion made was in order to convert from the airbox style to pressure cowl, the Dip Davis STC must be installed.

From your experience, it looks like a good call.

I don't think it's necessary to get FAA approval to make this conversion. (The manufacturer already did this change.) All you have to do is exactly copy Cessna's solution... because it's already approved (although some FSDO's might argue that it's only valid for B-models.)

[blueldr]

George,
It seems to me that to do the above mentioned cowling conversion as per Cessna on a '52 or earlier aircraft you would have to replace the whole cowling.

[hilltop170]

blueldr-
I don't know why anyone would want to convert from an airbox to pressure cowl unless it was required for a different engine installation. In that case, I would be very careful about doing it.

The DER package I read converting from the air box to pressure cowl using the old style, large hinged upper door cowling only required changing the internal baffles and seals. Plus, the Dip Davis latches were mandatory for the extra strength they provide. Apparently the old clip latches are not strong enough. I sure wouldn't trust them on a pressure cowl.

If I was inclined to do anything, it would be to convert TO an airbox, not away from one. The current thinking on reducing cooling drag and cooling efficiency is leaning toward air box cowling designs. Look at the top Reno Sport Class racers, they all have air box designs. Lowering cooling drag on our 170s could increase airspeeds in the order of maybe 1/4 to 1/2 mph. Who wouldn't want that? Maybe that's one real reason A models are so much faster than B's?

I would rather have an air box with the lagre cowling doors than a pressure cowl with the small access door. I can do a much better pre-flight when the whole side of the cowl hinges up.

Look at the inside of a cowling that has a pressure cowl such as a Super Cub, C-180, or 185. Every place the baffle seals rub against the cowling is removing cowling material due to the constant rubbing of the seals against the cowl. Throw in a little grit and grime and it really wears fast. The air box eliminates that contact except for the front run over the top of the airbox. Sure, you can put a strip of "Prop Guard" over the eroded areas, and that's what many have done, but not having the wear in the first place would be more desirable.

[GAHorn]

George,
It seems to me that to do the above mentioned cowling conversion as per Cessna on a '52 or earlier aircraft you would have to replace the whole cowling.

Yes, of course that is correct. Thanks for making that observation.

[blueldr]

I converted my '52 with the IO-360 engine and converted the cooling system to a pressure cowl using the original latches. However, even prior to the conversion I had installed safety pins on the latches. Never had a known problem.

[n2582d]

I converted my '52 with the IO-360 engine and converted the cooling system to a pressure cowl using the original latches. However, even prior to the conversion I had installed safety pins on the latches. Never had a known problem.

I flew an L-19 with a O-540. It too had safety pins (AN415-2) holding the latches secure. Here's a fuzzy picture from Fig. 28 of the L-19 manual.

L-19 Cowl Latch.jpg (16.79 KiB) Viewed 12300 times

Item 26, "retainer", is p/n 0652070. It is basically a "U" shaped bracket with two holes in either end to accept the lock pin. Item 25, is "pin, lock", p/n AN415-2.