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Racerx

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Service Bulletin (SB) 1375C supersedes SB 1375, SB 1375A, and SB 1375B in their entirety. If any of the four factory
original screws in the upper flange were replaced with oversize fasteners as part of compliance with SB1375A,
contact Piper for disposition. Aircraft that have complied with SB 1375B are in compliance with SB 1375C.

WARNING: SB 1375A SPECIFIED INCORRECT REPLACEMENT SCREWS FOR THE UPPER FLANGE.
ACCORDINGLY, IF ANY OF THE FOUR FACTORY ORIGINAL SCREWS IN THE UPPER
FLANGE WERE REPLACED WITH OVERSIZE FASTENERS AS PART OF COMPLIANCE
WITH SB1375A, THE AIRCRAFT MAY NO LONGER BE AIRWORTHY, CONTACT PIPER FOR
DISPOSITION
 
Landing gear attachment bolts. SB 1375C does not seem to be posted to the official Piper on-line tech docs system yet. From what I understand, this applies to most fixed gear Pipers with at least 2,000 hours or 7 years service and had installed oversized bolts as per SB 1375A.
 
it just showed up in registered owners email today. the issue is, if you complied with rev a or b as they instructed, then your aircraft could now be un-airworthy. who is going to pay for this screw up?
 
unsafervguy said:
it just showed up in registered owners email today. the issue is, if you complied with rev a or b as they instructed, then your aircraft could now be un-airworthy. who is going to pay for this screw up?
Click to expand...

What is the cost of compliance if your airframe is no longer airworthy due to this clusterf***?

-Skip
 
unsafervguy said:
it just showed up in registered owners email today. the issue is, if you complied with rev a or b as they instructed, then your aircraft could now be un-airworthy. who is going to pay for this screw up?
Click to expand...

It only applies to aircraft modified per 1375A, not 1375B.
 
3393RP said:
It only applies to aircraft modified per 1375A, not 1375B.
Click to expand...
Do you know what the bolt size/type differences are between A and B? Whats interesting is they use "may" be unairworthy like they dont know either.
 
I guess I'm not following with what has been posted. And I cant get PDFs to download at moment. But the oversize repair bolt sizes are 1/32 and 1/64 over the nominal 1/4 and 3/8 after a calculation of the hole size. I dont see where is states to replace a 1/4 with a 3/8? The 1/4 repair bolts are only about .015 to .030 larger so no where near a 3/8. Does B and C still call out for the use of 1/32 and 1/64 repair bolts?
 
Bell206 said:
Do you know what the bolt size/type differences are between A and B? Whats interesting is they use "may" be unairworthy like they dont know either.
Click to expand...

I don't have the information handy. I imagine that "may" is rather alarming for those affected.
 
upload_2023-5-25_17-9-20.png

Even this is messed up. 3/8" is .375, a long ways from .3130. 5/16" is .3125, which is maybe what they meant.

So what is it? 3/8" or 5/16"?
 
I think piper allowed an oversize bolt if the holes were a little wallowed out. But they screwed the pooch and said you could use a 3/8" bolt so some people may have drilled a 3/8 hole in their spars for the main landing gear strut to fit the 3/8 bolt. As @Dan Thomas pointed out a .375 bolt ain't fitting in a .3130 hole.

I assume the original bolts were 1/4". But could up size up to 5/16. Piper never intended that 3/8 bolt size to be used.
 
Racerx said:
I think piper allowed an oversize bolt if the holes were a little wallowed out. But they screwed the pooch and said you could use a 3/8" bolt so some people may have drilled a 3/8 hole in their spars for the main landing gear strut to fit the 3/8 bolt. As @Dan Thomas pointed out a .375 bolt ain't fitting in a .3130 hole.

I assume the original bolts were 1/4". But could up size up to 5/16. Piper never intended that 3/8 bolt size to be used.
Click to expand...

Oh, sh#t. This is a monumental screwup. I didn't notice the error.
 
Racerx said:
But they screwed the pooch and said you could use a 3/8"
Click to expand...
Thats the part I dont see. In the limited page you posted it shows the 1/4 and 3/8 as the "nominal" size per the chart. That to me means there are existing 1/4 and 3/8 bolts. And the oversize bolts are 1/32 and 1/64 larger to the existing 1/4 and 3/8. So unless it states somewhere else in the bulletin to use a 3/8 in place of a 1/4, it was the installer who screwed the pooch and not Piper. If someone did install a 3/8 bolt then I can definitely see Piper in full CYA mode to protect their interests especially with the previous spar failure. What does the calculation look like in 4b1 and 4b2 listed above?
 
Bell206 said:
Thats the part I dont see. In the limited page you posted it shows the 1/4 and 3/8 as the "nominal" size per the chart. That to me means there are existing 1/4 and 3/8 bolts. And the oversize bolts are 1/32 and 1/64 larger to the existing 1/4 and 3/8. So unless it states somewhere else in the bulletin to use a 3/8 in place of a 1/4, it was the installer who screwed the pooch and not Piper. If someone did install a 3/8 bolt then I can definitely see Piper in full CYA mode to protect their interests especially with the previous spar failure. What does the calculation look like in 4b1 and 4b2 listed above?
Click to expand...
Their are no 3/8 bolts on the main landing gear. That's where they goofed.
 
Racerx said:
Their are no 3/8 bolts on the main landing gear. That's where they goofed.
Click to expand...
Even easier. Can you post the page containing 4b1 and 4b2 from A as noted in Post #7? Its that calculation that determines the hole oversize limits and not the chart in Table 1.
 
Bell206 said:
Even easier. Can you post the page containing 4b1 and 4b2 from A as noted in Post #7? Its that calculation that determines the hole oversize limits and not the chart in Table 1.
Click to expand...

Even a decent a/p should have caught this. So hopefully nobody drilled a 3/8 hole in their spar. The first is 1375b . Which removed the 3/8 and .3130 hole size fiasco altogether. Between this and washergate...Screenshot_20230525-205155~2.png

Screenshot_20230525-204619.png
 
Good design practice is to, if possible, design any fitting to be adequately strong if drilled out for the next size bolt. In most cases this is 1/16 larger, i.e. 1/4 to 5/16. It looks like the "next size" for these close tolerance bolts specified in the SB 1/32 or 1/64 oversize, but if somebody drilled out a 5/16 to a 3/8 as RacerX said, oops.
 
Bacho said:
I don’t interpret those instructions as direction to drill a 3/8 hole. Any decent mechanic should’ve been asking questions before that happened.
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I agree, but I'm guessing there's one or two who did :eek:

I doubt anyone gets a new airplane out of the deal, but a bet a couple lawyers are going to get new boats...
 
Racerx said:
So hopefully nobody drilled a 3/8 hole in their spar.
Click to expand...
Since both 1375A and B require the use of the same paragraph 4 hole inspection criteria, its definitely not a direct Piper issue regardless of the 3/8 bolts listed in the A table charts. Hopefully its just a case of Piper receiving a number of calls questioning the 3/8 bolts and making a correction to cut the possibility of someone drilling a 3/8 hole. However, if someone did drill the hole they own it and owe someone a new spar or wing.
 
I've just completed a review of all my PA-32 aircraft maintenance logs. Some A&Ps specify exactly which ADs are completed while some just write "all current ADs complied with". Only one maintenance shop noted that "all current SBs are complied with". Piper has now posted SB 1375C to their website and it states that this inspection/correction must be done within 100 hours of TIS. For me that means next annual. I'm guessing that the A&P will have to remove each of the bolts and check if they are oversized. Maybe they can check them without removal?
 
I’m not familiar with this application. I would think it should be obvious if 3/8 bolts are installed. Removing them should not be necessary.
 
dfw11411 said:
Piper has now posted SB 1375C to their website and it states that this inspection/correction must be done within 100 hours of TIS. For me that means next annual.
Click to expand...
Need to put this into context first. While entries like "all current AD/SB are complied with" are basically meaningless, unless you have a specific write up showing SB1375-A was performed the "3/8 bolt issue" is moot. Now if you do have an -A entry, look for a SB1375-B sign off which would have already dealt with the "3/8 bolt issue" and provided a compliance method for -C as noted in the OP initial post. But if you have neither entry for A or B, then the compliance of SB1375-C is simply at your option as SBs are not mandatory for private Part 91 aircraft unless associated by rule like an AD. Regardless, as mentioned above it would be quite obvious if someone swapped a 3/8 bolt for a 1/4 bolt. And just to note, while it is prudent to review all OEM SBs/SLs for possible compliance it is usually not common to find a Part 91 aircraft with "all current SBs complied with" in my experiences.
 
My focus would be on preventing the issue. I’ve been vocal on the need to

check torque on lower nuts EVERY INSPECTION. I often find loose LOWER fasteners

and also broken bolts. This obviously overloads the remaking fasteners and can

lead to holes wearing oversized. My policy is broken bolts require replacement

of adjacent hardware. One slightly loose is just retighten.


Since I find an issue on about 50% of the Cherokee Inspections my guess is it’s

not related to age or TIS. Number of landings and/ or HARD landings on various

runway types are significant. The lower fasteners are exposed to tension loads

more than the upper ones. I’ve tried torque paint and enlisted a metallurgist to

determine the failure mode. Tension , shear or the nut loosening are all culprits.

Jury still out on this.


Bolts can be replaced w/o tank removal by using “ Special Words”.

A quick torque check using an open end wrench is easy to accomplish.

I urge folks to check for this condition BEFORE the spar is damaged.
 
Have you measured the length of any of the bolts there were loose?
 
Magman said:
My focus would be on preventing the issue. I’ve been vocal on the need to

check torque on lower nuts EVERY INSPECTION. I often find loose LOWER fasteners

and also broken bolts. This obviously overloads the remaking fasteners and can

lead to holes wearing oversized. My policy is broken bolts require replacement

of adjacent hardware. One slightly loose is just retighten.


Since I find an issue on about 50% of the Cherokee Inspections my guess is it’s

not related to age or TIS. Number of landings and/ or HARD landings on various

runway types are significant. The lower fasteners are exposed to tension loads

more than the upper ones. I’ve tried torque paint and enlisted a metallurgist to

determine the failure mode. Tension , shear or the nut loosening are all culprits.

Jury still out on this.


Bolts can be replaced w/o tank removal by using “ Special Words”.

A quick torque check using an open end wrench is easy to accomplish.

I urge folks to check for this condition BEFORE the spar is damaged.
Click to expand...
My A&P started doing this every annual a handful of years ago to every 28/32 after finding bolts not even finger tight.
 
dfw11411 said:
I've just completed a review of all my PA-32 aircraft maintenance logs. Some A&Ps specify exactly which ADs are completed while some just write "all current ADs complied with". Only one maintenance shop noted that "all current SBs are complied with". Piper has now posted SB 1375C to their website and it states that this inspection/correction must be done within 100 hours of TIS. For me that means next annual. I'm guessing that the A&P will have to remove each of the bolts and check if they are oversized. Maybe they can check them without removal?
Click to expand...
SB1375a came out March 2022. 1375 B came out February this year. So was only out for 11 months before it was supercede.

As Bell said, I doubt many part 91 guys complied unless their was other work in the area.
 
No I haven’t. If loose I just tighten. Usually about 1/4 turn. Broken bolts can be

another issue if the nut and part of the shank have departed.

My presumption is there is some variance in length between mfg.

I don’t recall any necking indicative of stretching.
 
Anyone who's done any machine work also knows that using any drill will likely make an out-of-tolerance hole; all commercial drills make oversize holes, by a thousandth or two, or up to much more with an unskilled drill operator. So even getting 0.251" out of a 1/4 drill would be spectacular. Drilling undersize and reaming is required for precise holes; I'm sure that's in the instructions we aren't seeing here.
 
Kenny Phillips said:
Anyone who's done any machine work also knows that using any drill will likely make an out-of-tolerance hole; all commercial drills make oversize holes, by a thousandth or two, or up to much more with an unskilled drill operator. So even getting 0.251" out of a 1/4 drill would be spectacular. Drilling undersize and reaming is required for precise holes; I'm sure that's in the instructions we aren't seeing here.
Click to expand...
Many drills are a bit undersized, and can be used to advantage by drilling a slightly smaller pilot hole first so that the final size drill's point doesn't make the hole larger if it's a bit off-center. Just use a micrometer to measure the drill flutes first.

Using a reamer is useful if the bolt is a close-tolerance bolt. Otherwise, you will find that AN bolt diameters can vary by .002" or even .003". An AN4 bolt is nowhere near .250", either.
 
Magman said:
My focus would be on preventing the issue. I’ve been vocal on the need to

check torque on lower nuts EVERY INSPECTION. I often find loose LOWER fasteners

and also broken bolts. This obviously overloads the remaking fasteners and can

lead to holes wearing oversized. My policy is broken bolts require replacement

of adjacent hardware. One slightly loose is just retighten.


Since I find an issue on about 50% of the Cherokee Inspections my guess is it’s

not related to age or TIS. Number of landings and/ or HARD landings on various

runway types are significant. The lower fasteners are exposed to tension loads

more than the upper ones. I’ve tried torque paint and enlisted a metallurgist to

determine the failure mode. Tension , shear or the nut loosening are all culprits.

Jury still out on this.


Bolts can be replaced w/o tank removal by using “ Special Words”.

A quick torque check using an open end wrench is easy to accomplish.

I urge folks to check for this condition BEFORE the spar is damaged.
Click to expand...

Is there a comparable set of bolts on PA28R that is often overlooked?
 
Kenny Phillips said:
And I see that they assume the technician has the proper technique and tools in their memory bank.
Click to expand...

Are you surprised? I was reviewing Cessna ADs the other day and 76-07-09 "to prevent separation of the vertical fin & rudder" One step is to "inspect attachment rear spar fitting bolt holes for excessive elongation" of course it does not define that at all.. Apparently eyeballs "looks round" is fine. Hole limits and bolt size is far from an interference fit despite being a shear loaded joint.
 
I seldom do Arrows so I can’t contribute on this.

Possibly a Type Club!

All aircraft have “ trouble areas “ that should be monitored.

These can vary by model and year/s/n but also how operated.
 
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