Drilling a bulkhead~2 questions

[Richard]

RE: 1962 Cherokee, Airtex interior

I didn't get any answer on the Cherokee board so I ask here.

1st Q: The bulkhead immediately aft of the baggage area, can I drill into this to rivet nutplates to secure a heavy fabric partition? The partition is designed to keep baggage, etc from entering the tail section and exposed control cables.

2nd Q: Would tinnermans be better than nut plates? I'm thinking the drilled holes need to be 'bridged' by the nutplates in order to preserve bulkhead integrity. Due to tight quarters I may have a problem getting a rivet gun into the work area.

 

[Michael]

RE: 1962 Cherokee, Airtex interior

I didn't get any answer on the Cherokee board so I ask here.

1st Q: The bulkhead immediately aft of the baggage area, can I drill into this to rivet nutplates to secure a heavy fabric partition? The partition is designed to keep baggage, etc from entering the tail section and exposed control cables.

2nd Q: Would tinnermans be better than nut plates? I'm thinking the drilled holes need to be 'bridged' by the nutplates in order to preserve bulkhead integrity. Due to tight quarters I may have a problem getting a rivet gun into the work area.

I dunno Rich, Wouldnt that be concidered an alteration?

 

[Richard]

I dunno Rich, Wouldnt that be concidered an alteration?

Oh, I guess the rest of the story is needed. My A&P says go ahead with the work. The existing screw holes are sloppy and oversized, hence the need for new holes. I have yet to do the work but it needs to be done soon because I don't like an unsecured baggage compartment and nearly unfettered access to exposed cables to the rear.

 

[Michael]

I don't like an unsecured baggage compartment and nearly unfettered access to exposed cables to the rear.

I agree there. I would have fixed it long before flying it. After seeing what you are referring to, Something as simple as a fuel tester or AFD could easily jam the cables and there would be little or nothing you could do about it. I still think a removable wood frame with velcro would be the easiest answer for you Rich.

 

[gismo]

RE: 1962 Cherokee, Airtex interior

I didn't get any answer on the Cherokee board so I ask here.

1st Q: The bulkhead immediately aft of the baggage area, can I drill into this to rivet nutplates to secure a heavy fabric partition? The partition is designed to keep baggage, etc from entering the tail section and exposed control cables.

2nd Q: Would tinnermans be better than nut plates? I'm thinking the drilled holes need to be 'bridged' by the nutplates in order to preserve bulkhead integrity. Due to tight quarters I may have a problem getting a rivet gun into the work area.

AFaIK, small holes (diameter less than 1/10 the cross section) have little or no effect on strength, but holes filled with rivets are as strong or stronger than the unmolested material. The nutplate itself probably adds a little strength as well. In any case nutplates are a much stronger attachment method than Tinnermans IMO. They can also have a retention ability that's not possible with Tinnermans that can keep a screw from backing out over time.

 

[tonycondon]

if the a&P says go for it, do it.

 

[SkykingC310]

Install new nutplates using pop rivets and you won't need your rivet gun!

 

[Richard]

Install new nutplates using pop rivets and you won't need your rivet gun!

Just how do you propose to install pop rivets without the gun?

 

[Tom-D]

Please don't use pop rivets, the next annual the IA will have a fit.

 

[Let'sgoflying!]

do thorough preplanning on where these are going - draw it out on the bulkhead, use the minimum holes required, use pre-existing holes if possible widely spaced as possible, not in a straight line where able, as far as possible from any supporting brackets, maximize edge distance, have a good look behind before drilling!, don't damage the bulkhead when bucking.

 

[Stache]

This would be considered an alteration and will require a FAA Form 337 to be filled out and field approved before you drill any holes for nut plates or any other hardware. The bulkheads are designed to take a certain stress load this can be found in CAR-3 or part 23 depending on the certification of your aircraft.

Just because an A&P says to do it may get you in some trouble down the read. Ask you A&P to fill out the 337 and submit it to your local FSDO for approval. Better to be safe than sorry.

Just one man’s opinion.

Stache

 

[Tom-D]

This would be considered an alteration and will require a FAA Form 337 to be filled out and field approved before you drill any holes for nut plates or any other hardware. The bulkheads are designed to take a certain stress load this can be found in CAR-3 or part 23 depending on the certification of your aircraft.

Just because an A&P says to do it may get you in some trouble down the read. Ask you A&P to fill out the 337 and submit it to your local FSDO for approval. Better to be safe than sorry.

Just one man’s opinion.

Stache

Show me where this is a major modification.

 

[gismo]

Show me where this is a major modification.

Yeah, we're talking (non-pressurization) bulkhead here, not wing spar. There's probaby more stress on a stringer under the floor.

 

[John Reed]

14CFR43 AppA (a) Major alteration:
(1) (viii) elements of an airframe...


14CFR43 AppA (b) Major repairs:
(1) (xiv) ... or bulkheads.

 

[Tom-D]

14CFR43 AppA (a) Major alteration:
(1) (viii) elements of an airframe...


14CFR43 AppA (b) Major repairs:
(1) (xiv) ... or bulkheads.

John please quote the whole reg.

Appendix A Major Alterations, Major Repairs, and Preventive Maintenance

(a) Major alterations

(1) Airframe major alterations. Alterations of the following parts and alterations of the following types, when not listed in the aircraft specifications issued by the FAA, are airframe major alterations:

(i) Wings.

(ii) Tail surfaces.

(iii) Fuselage.

(iv) Engine mounts.

(v) Control system.

(vi) Landing gear.

(vii) Hull or floats.

(viii) Elements of an airframe including spars, ribs, fittings, shock absorbers, bracing, cowling, fairings, and balance weights.

(ix) Hydraulic and electrical actuating system of components.

(x) Rotor blades.

(xi) Changes to the empty weight or empty balance which result in an increase in the maximum certificated weight or center of gravity limits of the aircraft.

(xii) Changes to the basic design of the fuel, oil, cooling, heating, cabin pressurization, electrical, hydraulic, de-icing, or exhaust systems.

(xiii) Changes to the wing or to fixed or movable control surfaces which affect flutter and vibration characteristics.

Do you see any thing mentioned about non structural components?

This part that this thread is about is to hold the cabin upholstery, and is not considered structure.

Adding anchor nuts has never been interperated as a major modification by anyone but here.

Thusly, any A&P would sign this off in the return to service entry, and be done with it.

Stache,,,,,,,,,I'm suprised that you don't follow FAA doctrine, and want un-needed 337s

 

[John Reed]

Tom,

Aren't you altering a structural member (the bulkhead) by installing a bunch of nutplates? Isn't that bulkhead an "element" of the airframe? Aren't you weakening and also altering the same element by drilling holes in it? The phrase "elements of an airframe" seems to me that there's more to their phrase than what they include in their description. Yes, the Baggage covering is non-structural but attached to something structural isn't it?

Don't let me give you a headache.

 

[Stache]

Show me where this is a major modification.

John has already pointed the reference in part 43, so let's take it a step further and look in FAR 1.1.

Major alteration means: an alteration not listed in the aircraft, aircraft engine, or propeller specifications—
(1) That might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or
(2) That is not done according to accepted practices or cannot be done by elementary operations.

Major repair means a repair:
(1) That, if improperly done, might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or
(2) That is not done according to accepted practices or cannot be done by elementary operations

From the above statement you can see drilling holes will change the structural strength and other qualities affecting airworthiness. So is a Form 337 required I would say yes because you are adding something that has to meet a flame resistance rule, are drilling additional holes, and installing additional hardware.

Look at it another way ask your aircraft insurance company if they will approve it as a minor alteration.

Any change to the type design is a alteration be it minor or major. I would want to cover myself and submit a 337. I’m sure most A&P’s would want to do the same.

Stache

 

[Tom-D]

Tom,

Aren't you altering a structural member (the bulkhead) by installing a bunch of nutplates? Isn't that bulkhead an "element" of the airframe? Aren't you weakening and also altering the same element by drilling holes in it? The phrase "elements of an airframe" seems to me that there's more to their phrase than what they include in their description. Yes, the Baggage covering is non-structural but attached to something structural isn't it?

Don't let me give you a headache.

In the list of fuselage components given in FAR 43 A do you see bulkhead listed?

(1) Airframe major alterations. Alterations of the following parts and alterations of the following types, when not listed in the aircraft specifications issued by the FAA, are airframe major alterations:

(i) Wings.

(ii) Tail surfaces.

(iii) Fuselage.

(iv) Engine mounts.

(v) Control system.

(vi) Landing gear.

(vii) Hull or floats.

(viii) Elements of an airframe including spars, ribs, fittings, shock absorbers, bracing, cowling, fairings, and balance weights.

You would need to research the Piper structural repair manual to see if the P/N is listed as a structural part.

I looked, it isn't.

That makes this a minor alteration.

 

[Tom-D]

John has already pointed the reference in part 43, so let's take it a step further and look in FAR 1.1.

Major alteration means: an alteration not listed in the aircraft, aircraft engine, or propeller specifications—
(1) That might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or
(2) That is not done according to accepted practices or cannot be done by elementary operations.

Major repair means a repair:
(1) That, if improperly done, might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or
(2) That is not done according to accepted practices or cannot be done by elementary operations

From the above statement you can see drilling holes will change the structural strength and other qualities affecting airworthiness. So is a Form 337 required I would say yes because you are adding something that has to meet a flame resistance rule, are drilling additional holes, and installing additional hardware.

Look at it another way ask your aircraft insurance company if they will approve it as a minor alteration.

Any change to the type design is a alteration be it minor or major. I would want to cover myself and submit a 337. I’m sure most A&P’s would want to do the same.

Stache

Let's remind every body who makes the decision if it is a major or minor alteration..

The A&P does.

they make that decision by following the rules set by the FAA.

FAR 43 A gives what a major alteration is, I do not see this as one of the listed alterations.

By using your reference you say

"1) That, if improperly done, might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness;"

Please explane how adding anchor nuts to a non structural part might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness?

Next, this statement

"Any change to the type design is a alteration be it minor or major. I would want to cover myself and submit a 337. I’m sure most A&P’s would want to do the same."

leads this audience to believe the FAA wants 337s on minor repairs, and or alterations, and that simplly isn't so.

otherwise the FAA would not have a minor anything listed in the FAR 1.1

 

[Tim]

Sigh .............. lets make a mountain out of a nut plate!

 

[Richard]

I appreciate this dialog. I do have a question concerning a comment made by Stache. Isn't it pretty black & white concerning the requirement for a 337? I mean, it should be already spelled out by the regs if a 337 is required. "...to cover my butt..." simply sounds pre-emptive for if and when the FAA changes the rules.

What am I missing?

BTW: velcro won't work due to the eneven surfaces at the perimeter of the fabric partition and the probability of adhesive failure on the aluminum bulkhead. I've discussed this attachment method with 2 different A&Ps and they both agree.

 

[Tim]

What am I missing?

About 30 years worth of history about Field approvals and the use of the form 337 and the fight within the FAA and outside. FSDO standardization. Instructions for continued airworthiness. CYA on major and minors...... and unclear understanding by owners, Mechanics and The FAA. Oh here come the lawyers to clear it all up! Nothing that 100 pages of regulation can't fix. Dang I'm getting cynical in my old age! Have another drink and think about it.......