Textron sevice letter SE73-37

[Gary Ward]

Can anyone help me find this letter? SE 73-37
TIA

 

[Mikey52]

Are you sure you got the number right? If so what does it might address?

 

[Gary Ward]

Are you sure you got the number right? If so what does it might address?

I did double check and that is the number I got off of the AD 74-04-01. It is a older AD from Feb 1974 so things might have changed? It pertains to cracks found in the aft bulkhead back by the rear window in a 1980 172N.
I have talked with one of my APs and he is doing his research as we speak. So I am not sure what he is going to come up with?
The AD does mention that Cessna service kit is SK 172-44 that is used to repair the crack. Not sure if that is still a good number and hopefully available .
Thanks for your help.

 

[Ryan Klems]

Gary, it's SE73-37R1. Not much in it however, it even mentions a "Figure 1" but none is in the PDF. Also attaching the SK172-44 instructions. Also, the bulkhead in question in the bulletin/service kit appears to be considerably further aft than the rear window.

 

[Dan Thomas]

I did double check and that is the number I got off of the AD 74-04-01. It is a older AD from Feb 1974 so things might have changed? It pertains to cracks found in the aft bulkhead back by the rear window in a 1980 172N.
I have talked with one of my APs and he is doing his research as we speak. So I am not sure what he is going to come up with?
The AD does mention that Cessna service kit is SK 172-44 that is used to repair the crack. Not sure if that is still a good number and hopefully available .
Thanks for your help.

AD 740-04-01 refers to the bulkhead way aft of the aft window. The vertical fin's forward spar attaches to it. The AD applies to 172Ms, not the N, as well.





That shot is from the service kit doubler mentioned in the Service Bulletin. Another:



The SB:




Edit: I see Ryan beat me to it. Good to have several sources on this forum.

 

[Dan Thomas]

Gary, is the crack in one of the vertical sections of that bulkhead under the rear window? Toward the bottom of the section, in the bent flange? If so, that's a common place to crack, and it's caused by flexing of the fuselage around that window as the tail yaws the airplane. You can see it flex if someone pushes sideways on the fuselage at the bulkhead under the front of the vertical fin. Don't let them push on any area not supported by internal structure!

When Cessna put that rear window into their singles, it weakened the structure there, and cracks are common. I've found them in 150s and 172s and 182s. The 150 tends to crack in the top horizontal member, near the corners where it is riveted to the verticals.

A patch has to be made and formed to fit that area. AC43.13-1B has the means to do that.

 

[Gary Ward]

Thank you Gentleman for setting me straight. I haven't heard from my AP since this morning as he does have a day job for an airline. I was as always trying to get a jump on what I was gonna need to repair it.
Late last night before bed I glanced through some ADs and found that one. I wasn't sure if it was pertaining to my problem.
Because of you Dan I looked there during my annual and low and behold there was a crack! I was so deflated and it was late, hot and I was tired. But thank you, you motivated me to strip all that plastic off and look closely.

"A patch has to be made and formed to fit that area. AC43.13-1B has the means to do that."
I will be looking that up as soon as I get off work. Thank you

Ryan thank you for taking the time for me.

 

[Gary Ward]

Any idea why the duct tape was there? That is not original is it? I feared it was hiding cracks.
I have been in the back several times during annuals.

But it has been a couple years since I removed all the plastic, glad I did last night. It is no fun but after I found that crack I got a little more motivated and removed all of it. Not easy and tough to keep track of all those small screws.
This is as far as I had it last year, so didn't inspect that bulkhead on that side.
Edit: This picture was from several years ago. I am looking all my old photos to see if I have pictures of the bulkhead bare since I did put some new plastic in this plane since I owned it including that piece that was hiding that bulkhead.

 

[Gary Ward]

Gary, is the crack in one of the vertical sections of that bulkhead under the rear window? Toward the bottom of the section, in the bent flange? If so, that's a common place to crack, and it's caused by flexing of the fuselage around that window as the tail yaws the airplane. You can see it flex if someone pushes sideways on the fuselage at the bulkhead under the front of the vertical fin. Don't let them push on any area not supported by internal structure!

When Cessna put that rear window into their singles, it weakened the structure there, and cracks are common. I've found them in 150s and 172s and 182s. The 150 tends to crack in the top horizontal member, near the corners where it is riveted to the verticals.

A patch has to be made and formed to fit that area. AC43.13-1B has the means to do that.

YES!

 

[Dan Thomas]

Lay on your back on that lower baggage shelf and look up at the top horizontal of that bulkhead, too. It's covered on its front by a plastic panel that almost never gets removed, and that bulkhead can also crack, especially near the connections with the verticals.

That duct tape is to prevent stuff from getting under the plastic trim and dropping onto that pulley cluster and jamming controls, and keeping stuff out of the tailcone in general. You might check the cables where they run over those pulley. Have someone moved the elevator and rudder and trim controls and watch the cables as they come aft from under the pulleys. Holding a finger on them as they move aft might find broken wires from wearing cables. See, too, if all those pulley are turning freely. You should be able to rotate them against cable friction; if there's a gummy, sticky feel to it, the bearings have dried out. They will someday seize. I have used small disposable medical syringes with a piece of that skinny tubing that comes with a WD-40 can, or similar, and applied a few drops of light oil to the tiny gaps between the inner races of the pulley bearings and the outer seal. Then rotate them to work the oil into the grease to soften it.

 

[Gary Ward]

Part of my old dragster body is now part of my plane, permanently.
I cut and bent a few pieces until I got the right grain orientation so it wouldn't crack when I bent and stretched it .035" thick.

 

[Gary Ward]

Moving on to the next issue or repair.
I used.035 over .025 cracked bulkhead with a .030 factory bulkhead behind it that had 2 rivets that were drilled out and replaced with longer rivets through the patch.