URGENT COWL DOOR INSPECTION NOTICE

[jlwild]

Following the Oct. 15th Dalton, GA fly-in, 1953 Cessna 170 B left cowl door (Fig. 48-35) popped open in flight shortly after departure Luckily the door did not rip off and the pilot returned to Dalton. It appears the forward latch (the high cowl pressure side) failed. The door was badly wrinkled. With the help of Roger Rollins tools, the wrinkles were repaired and door relatched. To make sure the door held on the flight home, a sheet metal screw and some duct tape completed the temporary repair .

Based on this pilots experience, I would urge all of you to inspect your cowl door fitment, latches and hinge for wear before your next flight . Our planes are getting older. These parts are subject to wear that can, and will, cause them to fail in flight . If the cowl door, upper cowl door opening, latches, or hinge assembly show signs of excess wear, it's time to make repairs

[mit]

Yep I need to figure out how to reconstruct the flange that is spot welded into the top cowl?

[Jr.CubBuilder]

Following the Oct. 15th Dalton, GA fly-in, an early model 170B left cowl door (Fig. 48-35) popped open in flight shortly after departure Luckily the door did not rip off and the pilot returned to Dalton. It appears the forward latch (the high cowl pressure side) failed. The door was badly wrinkled. With the help of Roger Rollins tools, the wrinkles were repaired and door relatched. To make sure the door held on the flight home, a sheet metal screw and some duct tape completed the temporary repair .

Based on this pilots experience, I would urge all of you to inspect your cowl door fitment, latches and hinge for wear before your next flight . Our planes are getting older. These parts are subject to wear that can, and will, cause them to fail in flight . If the cowl door, upper cowl door opening, latches, or hinge assembly show signs of excess wear, it's time to make repairs

Yep, been there, done that, got the proverbial T-shirt, and it was a traumatic experience. I switched to the Dip Davis cowl latches which work well, however in hind sight I think I would rebuild the stock latches and add some sort of a post to poke through the lever with a clip for positive retention. The advantage of the sotck latches is that they are spring loaded and allow a little bit of give the fitup of the top cowl when reassembling. With the Dip Davis system it is simplier, but there is no flexibility, so when the cowl goes back on everything has to be exactly lined up.

[c170b53]

During the last convention some eagle eyed southerner whilst judging spotted a fine crack that actually cracked through both the doubler and the skin of one of my doors. I'm with you Tim, I'd like to make a new top cowl with a later style oil door and get rid of the barn doors. I believe our president may have went that route.

[robw56]

Reminds me of this NTSB report I read: http://dms.ntsb.gov/aviation/AccidentRe ... 120000.pdf

[jlwild]

I'm with you Tim, I'd like to make a new top cowl with a later style oil door and get rid of the barn doors. I believe our president may have went that route.

Jim McIntosh is correct. About 10 years ago my left cowl door let go while in cruise mode, with my wife in the right seat. It was not a fun experience for her . As I am going thru my emergency checks to find out what has happened, I can remember her saying something like "we are going to d.." With power back to idle, the noise quit and I could see the door now stabilized but wide open and badly bent Luckily there was an airport close by where I landed for repairs. However, my ultimate fix was to remove the cowl door, latches and hinge and replace them with a new flush rivited patch in place of the old barn door. Then a much smaller oil inspection door, off a later model Cessna 172, was installed in the upper center of the patch. It turned out to be a very simple easy solution. Now using the smaller door I can check and add oil thru it. The down side is I need to remove the upper cowl to inspect and/or service the battery. However, that has never proven to be a problem and I don't have to worry about the door coming open any more .

[jlwild]

This is the only picture I have when the Oil Inspection Door was modified. However, it does show the large flush rivited patch and a small part of the smaller 172 inspection door.

170 Oil door.jpg

[cmsusllc]

I had a front latch wear thru the doubler so I cut out the doubler about an inch above and below the latch. I then drilled out a couple more spot welds and formed a new piece that replaced the cut out doubler and overlaped the existing then rivited it all together thru the drilled out spot welds. I also put anti chafe tape on all the mating surfaces and where the latch contacts the doubler. Seems to have solved my problem. I'll try to snap a picture next time I'm at the hanger.
Scott.....53B

[GAHorn]

...Yep, been there, done that, got the proverbial T-shirt, and it was a traumatic experience. I switched to the Dip Davis cowl latches ... With the Dip Davis system it is simplier, but there is no flexibility, so when the cowl goes back on everything has to be exactly lined up.

The subject airplane Wildman is describing is a later B-model, I believe....(?) The "Dip Davis" latch system is for the earlier, 1952 and prior cowls which have the inner air-box.

[runerider]

Another use for duct tape. Apiece across the top and bottom latch and it won't open in flight, any adhesive left on the cowl comes off with goof off.

[bagarre]

How are the latches failing?
Are they wearing out the over center mechanism and 'popping' open?
If so, I have a little camloc on mine to prevent that.
Or is the latch failing in some other way (hinge or part actually breaking and the little camloc provides no benefit)?

[Bruce Fenstermacher]

How are the latches failing?

First it is important to note we have two different cowls with two different latching systems and two different cowl door latch failures.

It seems by Jim's initial post description that the plane in question that had the cowl door issue was a '52 with the internal pressure box. These latches wear both in the area of the latch that catches the spring and the spring itself, that holds the latch over center. These MUST be secured in a secondary fashion IMO no matter what condition the latch and spring are in. It is these latches only that the Dip Davis system replaces.

The later B model which is one that Jim pictured has issues with the access doors. Over time from vibration the door edges and the areas the Hartwell latches contact, wear thin. They eventually start to pop open with vibration and flex unless secured with some other secondary system.

[falco]

I had a left cowling door pop open about 50' in the air immediately after takeoff, banging and flapping up and down. ('54B, big doors, hartwell latches) A slight left slip pinned it in one (the open) position, radioed tower that I wanted the runway NOW. (3 others in the pattern, 2 waiting for the runway.) The rest of it was uneventful and the door stayed where it was with the slip. No damage. No bad latch. Some wear on the metal as described above, but not enough to make it fail on its own.

I am NOT suggesting that the cases above were not mechanical issues -- but my incident was MY FAULT. I took a phone call after checking the oil level. And I didn't close the door properly.

Lesson learned: NEVER NEVER NEVER let your freakin phone distract you during something important like the preflight.

Lesson reenforced: Fly the airplane. Dont let something serious like an open cowl door distract you from something more serious like flying the airplane.

[GAHorn]

I also have experienced this .
While descending to land for fuel, just turning final, the door popped open and banged away... I also found it would quit banging by slipping the airplane. When I landed...both Hartwell latches were still in the latched posiitons. I have no idea how the door popped open, and it has never occured since. (And I have deliberately dived at 160 mph to try to duplicate the failure.)

It's been an occasional thought to develop a secondary latching system. Cleo Bickford endorsed adding a screw or Cam-Loc fastener to the upper/forward corner...but I"ve resisted that as it would require a tool to open the door.

Perhaps some day, after the door is damaged beyond repair, I'll regret not taking his advice.

[jlwild]

First it is important to note we have two different cowls with two different latching systems and two different cowl door latch failures.

It seems by Jim's initial post description that the plane in question that had the cowl door issue was a '52 with the internal pressure box. These latches wear both in the area of the latch that catches the spring and the spring itself, that holds the latch over center. These MUST be secured in a secondary fashion IMO no matter what condition the latch and spring are in. It is these latches only that the Dip Davis system replaces.

The later B model which is one that Jim pictured has issues with the access doors. Over time from vibration the door edges and the areas the Hartwell latches contact, wear thin. They eventually start to pop open with vibration and flex unless secured with some other secondary system.

To clear the issue up a little . The plane in the initial post description was a 1953 170B, s/n 25531, N4578C. My plane, pictured above with the addition of the smaller 172 door, is a 1955 170B, s/n 26958, N3415D. In these two cases it was the left door that failed. Also from other comments above, it appears most of the door failures were on the left doors. Has anyone had a right door failure on any of the models?