Piper is such a clusterF SB1375D emphasis on 'D'

Wonder how many folks complied with 1375A
 
It’s sort of good that Piper is addressing the issue but I think much is left

out. I‘ve been finding loose and broken bolts for many years. Long before

the SB came out. I check torque at every inspection . If loose my policy is

to re-tighten. Broken is replace obviously and also adjacent on that side.

In the absence of more in-depth guidance I thought this was fine.

The issue is always the Lower Attach Bolts which would be in tension.

If i read the SB correctly; now the requirement is a NDT of the Spar if

damaged bolts are found. So just what is a ” damaged bolt”?

Broken is obvious, but how about loose? Is the bolt stretched or has the

nut backed off? Recently I tried Torque Check paint to see if it could be

determined. Based on how many I find defective with only a few aircraft

there could be a long , long line waiting for NDT.
 
tceq24443 said:
What I feel whenever I see these SBs like this: How many has Piper had to re-issue in recent years.
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Well considering revision D provides the owner an additional option to repair the damage vs a spar change or major repair I think that would be a positive thing? Regardless, OEMs revise bulletins for a number of reasons to include fix errors and improve the process based on field reports just like 1375.
TCABM said:
Wonder how many folks complied with 1375A
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It is my understanding none did, but Piper rec'd a number of calls on the error.
Magman said:
If i read the SB correctly; now the requirement is a NDT
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In general:
SB1375C called for the eddy current. Revision D provides a more specific damage calculation to allow for a greater range of repair.

SB1375: Replace the L/G bolts
SB1375A: Replace L/G bolts and allow for repair of worn holes
SB1375B: Replace bolts and fix FU in Rev. A for repair of worn holes
SB1375C: Replace bolts, allow for repair, and add eddy current procedure to aid in inspecting worn holes
SB1375D: Replace bolts, allow for repair, and revised worn hole calculation to cover a greater range of situations to include reevaluation of worn holes performed under previous revisions.
 
Magman said:
The issue is always the Lower Attach Bolts which would be in tension.
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I thought that every bolt holding that assembly into the spar was in shear. Trying to remember the configuration so I could be incorrect.
 
My belief is landing loads put the lower bolts in tension

and also a smaller shear component.

Not really a valid sample but I’ll say I see about 3 out of 10 Cherokees

with a least 1 loose bolt. Broken bolts maybe 1 out of 25.

Either way that would keep an NDT tech busy.
 
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Magman said:
My belief is landing loads put the lower bolts in tension

and also a smaller shear component.

Not really a valid sample but I’ll say I see about 3 out of 10 Cherokees

with a least 1 loose bolt. Broken bolts maybe 1 out of 25.

Either way that would be a NDT tech busy.
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Sounds plausible. In any case, will be looking closely especially at the lowers.
 
Magman said:
My belief is landing loads put the lower bolts in tension

and also a smaller shear component.

Not really a valid sample but I’ll say I see about 3 out of 10 Cherokees

with a least 1 loose bolt. Broken bolts maybe 1 out of 25.

Either way that would keep an NDT tech busy.
Click to expand...
I'm surprised at the frequency you have encountered of loose/broken bolts. Since the SB isn't mandatory, how would you deal with a situation where an owner has inspected all the bolts, found none to be broken and all the torques to be correct? Replacing all the bolts per the SB is a major effort. Is that a situation where "don't fix something that isn't broken" may apply? Certainly this does seem like an area where increased attention and inspection is in order.
 
Since it’s an SB I do disagree with Piper‘s approach of changing ALL based on

time alone. I ALWAYS check the lower bolts at Inspections and see the

issue. My belief is the lower bolts can be over- stressed while the rest

are under-stressed if that makes sense.

Gary: Since everything is in order I would discuss with the Owner but

would likely do nothing . If a bolt is broken it gets replaced along with the

adjacent one. I started doing this even for bolts that are loose.

Since Piper has opted not to provide guidance related to individual

bolts I did some Research. A major aerospace firm analyzed the remains

of a failed bolt and determined the cause to be “ fretting”. I’m not sure

if this applies to all failures though.

By no stretch of the imagination do I consider myself a Metallurgist but

my belief is fretting involves a small amount of movement.

Hence replacing lower hardware when found loose in order to maintain

a rigid structure makes sense.


So; is a loose bolt “damaged” and trigger the need for an Eddy Current

Inspection per SB?
 
Magman said:
Since Piper has opted not to provide guidance related to individual bolts
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I believe rev. D formalizes guidance (on-condition) for individual bolts even though you could have used rev. C as guidance without having to complete the entire SB. Regardless, its my understanding the reason for the bulletin was due to the number of field reports of loose bolts as you mentioned earlier.

Keep in mind, the original version of the SB was simply a bolt replacement to ensure those bolts received additional attention within a reasonable timeframe. However, subsequent to that the field reports of damaged holes were more than anticipated and the revisions followed with increasing methods to keep installed parts in service.;)
 
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