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turbines
02-05-2009, 12:48 PM
I recently examined a C-421 with several scab patches applied with blind rivets to the trailing edge of the elevator. I am wondering what data was used to apply such a repair. I don't see anything similar in AC 43.13-1B. Even if the static balance could be achieved after the repair how would one determine what effect the repairs had on the dynamic balance of the control surface? There is nothing in the records and I suspect there is a good reason why.

Bubba1090
02-05-2009, 01:15 PM
I recently examined a C-421 with several scab patches applied with blind rivets to the trailing edge of the elevator. I am wondering what data was used to apply such a repair. I don't see anything similar in AC 43.13-1B. Even if the static balance could be achieved after the repair how would one determine what effect the repairs had on the dynamic balance of the control surface? There is nothing in the records and I suspect there is a good reason why.

...it meets the criteria of the Cessna MM. They tell you you can effect repairs (patches) if the damage doesn't exceed 15% of the skin thickness but it has to be done I/A/W the prescribed Special Repair Procedures in the manual.

Personally, I detest scab patches...

B 8)

Captainkirk
02-05-2009, 09:08 PM
...it meets the criteria of the Cessna MM. They tell you you can effect repairs (patches) if the damage doesn't exceed 15% of the skin thickness but it has to be done I/A/W the prescribed Special Repair Procedures in the manual.

Personally, I detest scab patches...

B 8)

Bubba, your comment doesn't address the question of whether or not this is a major repair. I believe it would be. Therefore, no documentation (i.e. form 337) would render the repair illegal regardless whether or not it was performed IAW the Cessna M/M. Also, any logbook entry should document verification of static balance check, along with the 337.

Bubba1090
02-06-2009, 05:12 AM
Bubba, your comment doesn't address the question of whether or not this is a major repair. I believe it would be. Therefore, no documentation (i.e. form 337) would render the repair illegal regardless whether or not it was performed IAW the Cessna M/M. Also, any logbook entry should document verification of static balance check, along with the 337.

...but since you brought it up & since you say it is, I say it isn't! :mrgreen: Just kidding, I could argue this either way but I'd have 2C the repair for a definitive answer. If it's a small patch - no, but if it's 2' x 4' oh yeah...

B 8)

Cessna Master Beta
02-08-2009, 05:38 AM
We have a C310 with the same ugly platches. No idea who came up with the idea but if it wasnt freshly painted I would remove them. Looks like something a 2 year old installed.

ppolstra
02-10-2009, 12:10 PM
Bubba, your comment doesn't address the question of whether or not this is a major repair. I believe it would be. Therefore, no documentation (i.e. form 337) would render the repair illegal regardless whether or not it was performed IAW the Cessna M/M. Also, any logbook entry should document verification of static balance check, along with the 337.

If this is a major repair it is spelled out in FAR 43 Appendix A:

(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.

My interpretation is that this is definitely a major repair. However, the 337 for a major repair need not be kept forever, only for 1 year. A major alteration 337 must be kept forever.

Bubba1090
02-10-2009, 12:34 PM
If this is a major repair it is spelled out in FAR 43 Appendix A:

(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.

My interpretation is that this is definitely a major repair. However, the 337 for a major repair need not be kept forever, only for 1 year. A major alteration 337 must be kept forever.

What's wrong with this picture? Oh, where do I start. Well first, the definition of a Major Repair does not come from FAR Part 43, it comes from FAR Part 1. Second, you're using the example of a repair but you're quoting an alteration, apples & oranges.

A Major Repair means a repair that, if improperly done, might appreciably affect weight, balance, structural strenght, performance, powerplant operation, flight characteristics or other qualities affecting airworthiness,

Like I said, I could argue this either way. Pick a side & we'll discuss it...

B 8)

BTW, the 337 for a major repair isn't automatically discarded after one year so that's not altogether true! Do you know why?

Captainkirk
02-10-2009, 09:32 PM
I'll pick a side. I'll say this is a major repair, as it constitutes a repair to a control surface (flight control) by metal repair procedures involving riveting, which incidentally, requires control surface balancing check after the repair. This repair would require a form 337 be filed at least in duplicate, one which could potentially navigate it's way to the circular file after a time; and the other, which would take up permanent residence in an Oke City filing cabinet.

Bubba1090
02-11-2009, 06:25 AM
I'll pick a side. I'll say this is a major repair, as it constitutes a repair to a control surface (flight control) by metal repair procedures involving riveting, which incidentally, requires control surface balancing check after the repair. This repair would require a form 337 be filed at least in duplicate, one which could potentially navigate it's way to the circular file after a time; and the other, which would take up permanent residence in an Oke City filing cabinet.

Just b/c it's a flight control doesn't mean it's a Major Repair. If you think so, I'm from Missouri-show me! Go read FAR Part 1...

B 8)

Captainkirk
02-11-2009, 08:02 AM
(b) Major repairs(1) Airframe major repairs. Repairs to the following parts of an airframe and repairs of the following types,involving the strengthening, reinforcing, splicing, and manufacturing of primary structural members or their replacement, when replacement is by fabrication such as riveting or welding, are airframe major repairs.

(i) Box beams.

(ii) Monocoque or semimonocoque wings or control surfaces.

(iii) Wing stringers or chord members.

(iv) Spars.

(v) Spar flanges.

(vi) Members of truss-type beams.

(vii) Thin sheet webs of beams.

(viii) Keel and chine members of boat hulls or floats.

(ix) Corrugated sheet compression members which act as flange material of wings or tail surfaces.

(x) Wing main ribs and compression members.

(xi) Wing or tail surface brace struts.

(xii) Engine mounts.

(xiii) Fuselage longerons.

(xiv) Members of the side truss, horizontal truss, or bulkheads.

(xv) Main seat support braces and brackets.

(xvi) Landing gear brace struts.

(xvii) Axles.

(xviii) Wheels.

(xix) Skis, and ski pedestals.

(xx) Parts of the control system such as control columns, pedals, shafts, brackets, or horns.

(xxi) Repairs involving the substitution of material.

(xxii) The repair of damaged areas in metal or plywood stressed covering exceeding six inches in any direction.

(xxiii) The repair of portions of skin sheets by making additional seams.

(xxiv) The splicing of skin sheets.

(xxv) The repair of three or more adjacent wing or control surface ribs or the leading edge of wings and control surfaces, between such adjacent ribs.

(xxvi) Repair of fabric covering involving an area greater than that required to repair two adjacent ribs.

(xxvii) Replacement of fabric on fabric covered parts such as wings, fuselages, stabilizers, and control surfaces.

(xxviii) Repairing, including rebottoming, of removable or integral fuel tanks and oil tanks.

Bubba1090
02-11-2009, 08:55 AM
(b) Major repairs(1) Airframe major repairs. Repairs to the following parts of an airframe and repairs of the following types, involving the strengthening, reinforcing, splicing, and manufacturing of primary structural members or their replacement, when replacement is by fabrication such as riveting or welding, are airframe major repairs.

(i) Box beams.

(ii) Monocoque or semimonocoque wings or control surfaces.

Where did putting a patch on a tail surface meet the criteria you posted? I'll tell you, it didn't! The key word in the paragraph is AND meaning both criteria must be met (it's legalese). You are correct in the 1st part but you're not correct in the 2nd. You never strengthened, reinforced, spliced, or manufactured a primary structural members or their replacement. And the fact that you riveted does not, in itself make a repair major. The fact that the piece you manufactured by riveting (i.e. making a rib with braces) makes it Major. Ergo, NOT a Major Repair! If it was, every time you riveted in an OEM skin it would qualify & we all know that it doesn't. Nice try but sorry, try again... :mrgreen:

B 8)

ppolstra
02-12-2009, 06:48 PM
What's wrong with this picture? Oh, where do I start. Well first, the definition of a Major Repair does not come from FAR Part 43, it comes from FAR Part 1. Second, you're using the example of a repair but you're quoting an alteration, apples & oranges.

A Major Repair means a repair that, if improperly done, might appreciably affect weight, balance, structural strenght, performance, powerplant operation, flight characteristics or other qualities affecting airworthiness,


BTW, the 337 for a major repair isn't automatically discarded after one year so that's not altogether true! Do you know why?

OOPS! I cut and pasted from the wrong part of the FAR! I stand corrected, I was quoting from the major alteration section.

As to the 337, it doesn't automatically get discarded after a year. I was just trying to make the point that unlike the 337 for an alteration it need not be kept forever (under most circumstances). As a practical matter, most people keep all records forever, despite no FAA requirement (mostly because of the hit to aircraft value for missing logs).

Captainkirk
02-12-2009, 08:34 PM
Sorry, Big B, I gotta disagree with ya on this one. I've filed many a 337 for the replacement of factory skins and never had one returned as unnecessary. I don't follow your interpretation.....

Repairs to the following parts of an airframe and repairs of the following types, involving the strengthening, reinforcing, splicing, and manufacturing of primary structural members or their replacement, when replacement is by fabrication such as riveting or welding, are airframe major repairs

Let's break this down....

Repairs to the following parts of an airframe ....
They continue on with a list of the affected parts......
(i) Box beams.

(ii) Monocoque or semimonocoque wings or control surfaces.

(iii) Wing stringers or chord members.

(iv) Spars.

(v) Spar flanges.

(vi) Members of truss-type beams.

(vii) Thin sheet webs of beams.

(viii) Keel and chine members of boat hulls or floats.

(ix) Corrugated sheet compression members which act as flange material of wings or tail surfaces.

(x) Wing main ribs and compression members.

(xi) Wing or tail surface brace struts.

(xii) Engine mounts.

(xiii) Fuselage longerons.

(xiv) Members of the side truss, horizontal truss, or bulkheads.

(xv) Main seat support braces and brackets.

(xvi) Landing gear brace struts.

(xvii) Axles.

(xviii) Wheels.

(xix) Skis, and ski pedestals.

(xx) Parts of the control system such as control columns, pedals, shafts, brackets, or horns.

(xxi) Repairs involving the substitution of material.

(xxii) The repair of damaged areas in metal or plywood stressed covering exceeding six inches in any direction.

(xxiii) The repair of portions of skin sheets by making additional seams.

(xxiv) The splicing of skin sheets.

(xxv) The repair of three or more adjacent wing or control surface ribs or the leading edge of wings and control surfaces, between such adjacent ribs.

(xxvi) Repair of fabric covering involving an area greater than that required to repair two adjacent ribs.

(xxvii) Replacement of fabric on fabric covered parts such as wings, fuselages, stabilizers, and control surfaces.

(xxviii) Repairing, including rebottoming, of removable or integral fuel tanks and oil tanks.

You will kindly note that CONTROL SURFACES falls into this group......

Call me ignorant, but my interpretation says that repairs to a control surface that involve strengthening or reinforcing when replacement (or installation...MY interpretation) is by.....riveting...constitutes a major repair.

When you install a Piper landing gear rib doubler kit on a Seneca II, do you mean to tell me you don't file a form 337?!!!!
I've done that service kit 4 times, on four different aircraft...submitted four separate 337's....and never had one sent back saying, "Aw, geez, guy...you REALLY didn't need to file this......" You are drilling out rivets and adding doublers into a spar, and riveting them to the spar....a major repair, no?

The key word in my opinion are not simply riveting, but riveting on one of the aforementioned parts.....control surfaces being one of them, along with the words strengthening and reinforcing, which both apply to a doubler/patch.

That's my interpretation, anyway.

Where is a fed when you need him?:coffee:

Bubba1090
02-13-2009, 06:35 AM
Sorry, Big B, I gotta disagree with ya on this one. I've filed many a 337 for the replacement of factory skins and never had one returned as unnecessary. I don't follow your interpretation.....

Repairs to the following parts of an airframe and repairs of the following types, involving the strengthening, reinforcing, splicing, and manufacturing of primary structural members or their replacement, when replacement is by fabrication such as riveting or welding, are airframe major repairs

Let's break this down....

Repairs to the following parts of an airframe ....
They continue on with a list of the affected parts...
(i) Box beams.

(ii) Monocoque or semimonocoque wings or control surfaces. O.K. this is what we're debating!

(iii) Wing stringers or chord members.

(iv) Spars. (You're Piper example)


You will kindly note that CONTROL SURFACES falls into this group... (Agreed)

Call me ignorant (I wouldn't do that), but my interpretation says that repairs to a control surface that involve strengthening or reinforcing when replacement (or installation... MY interpretation) is by...riveting... (Here's where you're missing it) constitutes a major repair.

When you install a Piper landing gear rib doubler kit on a Seneca II, do you mean to tell me you don't file a form 337?!!!! (Bad example)
I've done that service kit 4 times, on four different aircraft...submitted four separate 337's....and never had one sent back saying, "Aw, geez, guy...you REALLY didn't need to file this... "You are drilling out rivets and adding doublers into a spar, and riveting them to the spar... a major repair, no? Yes, agreed but that's to a SPAR not control surface)

The key word in my opinion are not simply riveting, but riveting on one of the aforementioned parts... control surfaces being one of them, along with the words strengthening and reinforcing, which both apply to a doubler/patch. (Not true-I'll explain below)

That's my interpretation, anyway.

Where is a fed when you need him?:coffee: Who sez we NEED him?

I like this, I feel like I'm in English 101 again! I'll diagram this sentence... First of all you're talking apples & oranges with the Piper kit, that's a spar & I agree-337! But I must emphasize & clarify Repairs to the following parts of an airframe AND repairs of the following types, involving the strengthening, reinforcing, splicing, and manufacturing of primary structural members or their replacement, when replacement is by fabrication such as riveting or welding, are airframe major repairs & what they mean by that. Just b/c you do a repair to a control surface does not constitue a Major Repair in itself! Just b/c you use riveting does not constitute a Major Repair in itself! The first element of this crime is that the repair must meet BOTH criteria! This doesn't! Now before you go getting you're lanyard caught in a lathe, I'll explain in a sec... The last (& most important) element of this crime is, "...that if improperly done might appreciably effect weight, balance, structural strengh, performance, powerplant operation, flight characteristics, or other qualities effecting airworthiness (Ya think? I say no but let's say yes for arguement sake) OR that is not done according to accepted practices or cannot be done by elementary operations. (C'mon, I got ya here)

So I'm back to my "I'll explain" but it took more than a sec... When they say "involving the strengthening, reinforcing, splicing, and manufacturing of primary structural members or their replacement, when replacement is by fabrication such as riveting or welding, are airframe major repairs" they mean that the part manufactured to effect the repair is made by those means. E.g., when you are repairing one outbd LE skin for a Cessna 182 & its not available so your talented SM guy sez I'll just make it. He bends the metal, rivets on two stringers & a rib cap, that now becomes a Major Repair b/c he riveted parts together to make one whole part. You'll agree that if it were an OEM skin it's not major! That's how that has been interpreted by legal for years. Our's is a simple repair done with common practices that doesn't effect strength, flight characteristics, W&B etc-Not a Major Repair!

Luv ya, brother...

B 8)

turbines
04-09-2009, 07:31 AM
I appreciate all the contributions to this thread. Inspite of this
I am convinced, that lacking approved data, installing an external scab patch on any control surface is a Major Repair. The technician can not predict the affect of the repair on the dynamics of the control surface. Any repair, on control surface or other external structure, that affects aerodymanics is Major and requires approval.

Bubba1090
04-09-2009, 07:40 AM
I appreciate all the contributions to this thread. Inspite of this
I am convinced, that lacking approved data, installing an external scab patch on any control surface is a Major Repair. The technician can not predict the affect of the repair on the dynamics of the control surface and any repair, on control surface or other external structure, that affects aerodymanics is Major and requires approval.

...ASK! Call your PMI & ask him the question. There's a 50-50 chance he'll get it right...

B 8)

turbines
04-09-2009, 08:42 AM
I have asked several and will post their replies when received. I am sure the 50-50 will be right. As always, if you don't hear the answer you want to hear ask someone else..hehe!

Bubba1090
04-09-2009, 08:48 AM
I have asked several and will post their replies when received. I am sure the 50-50 will be right. As always, if you don't hear the answer you want to hear ask someone else..hehe!

...is the TECHNICIAN determines whether a repair is Major or Minor, NOT the FAA. Use the Alteration Tree, make a determination, bring your testicles with you & TELL them what it is!

B 8)