Revision 1 - Univair Aircraft Corporation
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1. UNIVAIR AIRCRAFT CORPORATION TOLL FREE ORDER 1 888 433 5433 LANT OFFICES AND WAREHOUSES 2500 HIMALAYA ROAD AURORA CO 80011 8156 INFO TELEPHONE 303 375 8882 FAX NUMBERS 800 457 7811 or 303 375 8888 e mail web site www univair com Dear Ercoupe Forney Alon Mooney M10 Owner The attached Service Bulletin No 31 Revision 1 dated June 14 2002 updates Service Bulletin No 31 dated January 29 2002 Compliance with either version of Service Bulletin No 31 meets the requirements of AD 2002 26 02 Univair prefers that Service Bulletin No 31 Revision 1 dated June 14 2002 be used since it includes all options for compliance it includes more detail on corrosion prevention and it matches the AD for continued inspection intervals every 3 years The originat request for Service Bulletin 31 came from the FAA based upon a Memorandum dated December 20 1999 from the Minneapolis FSDO to the Recommendation and Quality Assurance Division of the FAA The Memorandum detailed some of the advanced corrosion found in an Ercoupe 415 during the demonstration of the use of a borescope We were assured by the FAA that this was a flying aircraft and not a wreck used by a mechanics school The Memorandum mentioned 27 other documented cases of corrosion throughout the wing components and other parts of Ercoupe series airframes since 1974 Univair inspected the center section of an Ercoupe that has been stor2. MIL P 6889 or green MIL P 8585 Type I specification 10 Replacement Replacement of unairworthy components of the wing center section may be accomplished in accordance with the Ercoupe Forney Alon or Mooney M 10 Service Manual as applicable Ercoupe Service Memorandum No 53A provides detailed instructions for replacement of rear spar of wing center section It is highly recommended that all interior surfaces of replacement parts be primed with one of the paints listed in step 9 before installation 11 Reassembly and cover plate installation After inspections and repairs are complete if inspection openings were made Method 1 install cover plate assemblies in each opening as shown on drawing SB 31 Sheet 2 Revision None dated 01 29 02 Secure each cover plate with three 3 8 machine screws and three 032 thick washers Univair Service Kit SK 80 1 includes inspection panel assemblies for aircraft with smooth center section bottom skins to comply with this Service Bulletin per Method 1 Kit SK 80 1 also includes rivets and cover plate attaching hardware Univair Service Kit SB 80 2 includes all inspection panel assemblies for aircraft with beaded center section bottom skins to comply with this Service Bulletin per Method 1 Kit SK 80 2 also includes rivets and cover plate attaching hardware Reinstall interior items removed in Step 1 and wing tanks if removed Reinstall outer wing panels if re
3. removed to inspect the front side of the main wing spar even if no corrosion is found elsewhere Method 2 borescope method On each side of the wing center section insert the borescope into the wing center section through the gap between the wing center section and outer wing panel and through lightening holes in the center section ribs Inspect all areas of the wing center section structure through all necessary openings in the wing center section until it has been determined that all areas of the wing center section between the front and Univair Aircraft Corporation Service Bulletin No 31 page 5 of 9 rear spars and aft of the rear spar not accessible from the cockpit have been inspected for corrosion and unrepaired damage FAA Advisory Circular AC 43 4A Corrosion Control for Aircraft dated 7 25 91 or later should be used to identify corroded areas Due to the extensive use of thin materials in the wing center section any parts with corrosion beyond light corrosion as defined in AC 43 4A Chapter 6 Section 4 paragraph 640 is considered unairworthy If corrosion is found on the rear side of the front spar or if corrosion is suspected for other reasons remove wing fuel tanks in accordance with the appropriate Service Manual and inspect the front side of the wing spars for corrosion required no corrosion is found aft of the main wing spar wing tank removal is to be accomplished at the inspector s discretion However i
4. 37 contains required parts to comply with this bulletin 7 On all Ercoupe Forney Alon and Mooney M 10 aircraft accomplish of the following For Method 1 Locate eight inspection openings on the lower wing surface per OR the enclosed drawing SB 31 Sheet 1 Revision None dated 01 29 02 For aircraft with smooth bottom skins all openings should be 4 inches in diameter For aircraft with beaded bottom skins four of the openings should be 4 inches in diameter and four of the openings should be 3 inches in diameter as shown on drawing 5 31 CAUTION if the opening locations specified by the diagram interfere with any skin stiffeners alter the opening location to clear the stiffener Be sure also to provide clearance for installation of reinforcement rings to be installed in Step 11 Cut inspection openings at the locations noted above and deburr For Method 2 Acquire an Endoscope or Fiberscope Borescope that meets the OR following minimum characteristics it must have a high intensity light source The optical system must be of a quality such that it remains constantly in focus from about 4 mm 0 16 inch to infinity e When the tip is approximately 4 mm from the inspected surface a magnification of about 10X must be achieved e The image guide and protective sheath length must be approximately 2 feet long to insure that all areas of the wing center section structure may be properly inspected There
5. MENSIONS SHOWN ARE APPROXIMATE CENTER OPENINGS IN FLAT PORTIONS OF BOTTOM SKIN ALLOW ROOM FOR INSPECTION PLATE REINFORCEMENT RINGS DPENINGS MAY BE MOVED OUTBOARD OF BEADS IF REQUIRED TO CLEAR BEADS AND STRUCTURE INSTALL REINFORCEMENT RINGS AND INSPECTION PLATES AS SHOWN ON SHEET 2 RIGHT HAND PORTION OF WING CENTER SECTION SHOWN INSTALL INSPECTION OPENINGS AND INSPECTION PLATE ASSEMBLIES IN LEFT HAND PORTION OF WING CENTER SECTION USING SAME DIMENSIONS FROM OUTBOARD AND TRAILING EDGES SEE NOTE 2 INSP PLATE INSTL FOR AIRCRAFT WITH BEADED SKIN PLATE FOR AIRCRAFT WITH SMOOTH SKIN ram ween si OO _ ive ei ET W UNIVAIR AIRCRAFT CORPORATION FINISH 2500 HIMALAYA RD PM NONE nl INSPECTION PLATE INSTL DELS SHEET NO DRAWING NO REV NONE MODELS SEE SERVICE BULLETIN NO 31 5 31 DATE 06 14 02 3 DRILL 3 PLACES 40 DRILL 7 PLACES REINFORCEMENT RING Sn VAL LLL aL LER LLLE oS ANAT BOTTOM SKIN OF MS20470AD3 RIVET CENTER SECTION SECTION SCALE 2 1 CLIP NUT REINFORCEMENT RING Sr SSS SSS SSS OA ae BOTTOM SKIN OF CENTER SECTION COVER PLATE AN526C832R8 SCREW VIEW LOOKING DOWN ON WASHER INSTR
6. UCTIONS INSPECTION OPENING SECTION B B FOR EACH INSPECTION OPENING SCALE 2 1 1 CENTER REINFORCEMENT RING OVER OPENING WITH ONE SCREW HOLE ORIENTED FORWARD UNIVAIR AIRCRAFT CORPORATION 3 PLACE REINFORCEMENT RING INSIDE WING CARRY THROUGH AURORA COLGRADO 80011 STRUCTURE CENTERED OVER OPENING RIVET IN PLACE Pars rime INSPECTION PLATE INSTL USING MS20470AD3 RIVETS 4 INSTALL CLIP NUTS OVER 218 DIA HOLES AS SHOWN MODELS SHEET 0 DRAWING NO SB 31 REV NONE 2 OF 2 DATE 06 14 02 6 40 6 J9V d FE ON JOLANSS IN SECTION 8 5 INSTALL INSPECTION PLATE WITH 3 8 32 MACHINE SCREWS INSTALL WITH 032 THICK WASHERS BETWEEN COVER PLATE AND WING SKIN TO PREVENT DEFORMING COVER PLATES
7. and unrepaired damage FAA Advisory Circular AC 43 4A Corrosion Control for Aircraft dated 7 25 91 or later should be used to identify corroded areas Due to the extensive use of thin materials in the wing center section any parts with corrosion beyond light corrosion as defined in AC 43 4A Chapter 6 Section 4 paragraph 640 is considered unairworthy Repair or replace any parts considered unairworthy prior to further operation 4 For Methods 1 2 amp 3 For Ercoupes prior to Serial Number 4869 verify that AD 59 05 04 has been complied with by the installation of the rear spar stiffeners Ercoupe Service Memorandum 53A shows the details of this reinforcement modification If there are no rear spar reinforcements in place install them in accordance with Ercoupe Service Memorandum 53 Univair Service Kit SK 9 contains the required parts to comply with Ercoupe Service Memorandum 5 5 For Methods 1 2 amp 3 On Ercoupes Serial Nos 113 to 2037 inclusive if not already done comply with Ercoupe Service Bulletin No 18 by installation of center section stiffener clips and if required belly skin reinforcements in accordance with Ercoupe Service Bulletin No 18 Univair Aircraft Corporation Service Bulletin No 31 page 3 of 9 6 For Methods 1 2 amp 3 Ercoupes prior to Serial Number 5714 install drain holes and clam shell cover plates in accordance with Fornaire Service Bulletin No 109 Univair Service Kit SK
8. ed indoors all its life in Colorado or Wyoming where one would expect no signs of corrosion Some light corrosion was found in the center section of this aircraft that has spent the last 50 years in desert country We therefore agree with the FAA that there be real corrosion problem and we encourage all Ercoupe Forney Alon Mooney M10 owners to take this Service Bulletin and AD very seriously Univair does not have a preference for method of inspection Please keep the following in mind when you are determining which method you want to use to comply with AD 2002 26 02 Once the inspection openings of Method 1 are in place almost any mechanic or shop can easily comply with the subsequent inspections required every three years If you use one of the other methods for the initial inspection the inspection openings be installed at a subsequent inspection if the inspector does not have access to a borescope or does not feel comfortable removing the wings Please note that the Service Bulletin and the AD require that a borescope meet certain criteria to be used for the borescope inspections One of the requirements for the borescope is that the image guide and protective sheath length must be approximately 2 feet long to insure that alf areas of the wing center section structure may be properly inspected Univair tested a borescope with a shorter image guide and sheath and found it did not adequately reach ail areas of the wing center sec
9. l 8 Inspection procedure Inspect the wing center section using one of the following procedures Method 1 inspection opening method Using a bright light that can fit through the inspection openings and that will properly illuminate each area of the wing center section thoroughly inspect the wing panel structure for corrosion and unrepaired damage Inspect all areas of the wing center section structure through all necessary openings the wing center section until it has been determined that all areas of the wing center section between the front and rear spars and aft of the rear spar not accessible from the cockpit have been inspected for corrosion and unrepaired damage FAA Advisory Circular AC 43 4A Corrosion Control for Aircraft dated 7 25 91 or later should be used to identify corroded areas Due to the extensive use of thin materials in the wing center section any parts with corrosion beyond light corrosion as defined in AC 43 4A Chapter 6 Section 4 paragraph 640 is considered unairworthy If corrosion is found on the rear side of the front spar or if corrosion is suspected for other reasons remove wing fuel tanks in accordance with the appropriate Service Manual and inspect the front side of the wing spars for corrosion required if no corrosion is found aft of the main wing spar wing tank removal is to be accomplished at the inspector s discretion However it is highly recommended that the wing fuel tanks be
10. l corrosion is suspected prior to the end of the three year inspection period repeat the inspections and repairs of this Bulletin prior to further flight INFORMATION AND PARTS AVAILABILITY Copies of Ercoupe Forney Alon and Mooney M 10 Service Manuals are available from Univair Aircraft Corporation Copies of Ercoupe Service Memorandum No 53A Ercoupe Service Bulletin No 18 and Fornaire Service Bulletin No 109 are available from Univair Aircraft Corporation Contact Univair Aircraft Corporation for availability and pricing of wing center section replacement parts and parts for complying with Service Memorandums and Bulletins Cover plate kits SK 80 1 and SK 80 2 are available from Univair Aircraft Corporation LANDING GEAR CUTOUT FORWARD OUTBOARD eaoeecos 4 INCH DIA DPENING FORWARD ene OUTBOARD 4 INCH DIA DPENING 4 PLACES 30 3 INCH DIA OPENINGS 4 INCH DIA OPENING REAR SPAR AIRCRAFT WITH SMOOTH BOTTOM SKIN REAR SPAR AIRCRAFT WITH BEADED BOTTOM SKIN 1 VIEWS LOOKING UP AT BOTTOM OF 41 RIGHT HAND PORTION OF WING CENTER SECTION SEE NOTE 2 gt RIVET SS 415 13281 00 INSP PLATE ASSY 4 50 DIA 415 13280 00 INSP PLATE ASSY 5 50 DIA 0 8 39 4 bE NLININI 391 35 a anes Che re aia DREE NOTES 1 BREAK ALL SHARP EDGES 2 DI
11. lure of the wing center section which could result in loss of control of the airplane Consequently this Service Bulletin provides for the careful inspection of the wing center section to establish the condition of the center section structure using one of three methods Method 1 Install inspection openings in the bottom of the wing center section skins The inspection openings will then allow routine inspections to be accomplished as required under FAR Part 43 Appendix D f Method 2 A Fiberscope Borescope or an Endoscope meeting the minimum characteristics listed in this Service Bulletin may be used to perform the inspections without the installation of inspection openings or outer wing panel removal Method 3 Remove the outer wing panels to gain visual access to the wing walkway box structure Carefully review the following procedures to determine the best method of accomplishing the inspections PROCEDURE 1 For Methods 1 2 amp 3 Remove the forward floorboard seat cushion s seat bucket s and any other interior items necessary to gain clear access to the wing center section where it passes through the fuselage 2 For Methods 1 2 amp 3 Remove ail soundproofing in the lowest belly regions and discard Do not replace soundproofing Inspect and clear all drain holes 3 For Methods 1 2 amp 3 Inspect front and rear spars in fuselage area and surrounding structure for corrosion wrinkles loose rivets skin cracks
12. moved per Method 3 in reverse sequence of removal making sure that mounting bolts are properly fitted and safetied Univair Aircraft Corporation Service Bulletin No 31 7 of 9 NOTE The recommended method for tightening the nuts on the wing attach bolts is to draw nuts down tight and continue tightening as required to line up the nearest slot and cotterpin hole provided you do not exceed 100 46 dry torque on the front bolts and 10 ft lbs dry torque on the rear bolts Safety wing attach bolts with NEW cotter pins AN380 4 4 MS24665 353 for front and AN380 2 2 MS24665 132 for rear fittings DO NOT reuse old cotter pins Reinstail left and right wing fairings between the wing center section and outer wing panels if removed per Method 2 or 3 12 Required documentation Make log book entry stating compliance with Service Bulletin No 31 State which method was used for inspection inspection panel method borescope method or wing removal method and whether wing tanks were removed for inspection of forward side of front spar or not Weight and balance change is considered negligible 13 Continued inspections Assuming no corrosion has been found in the wing center section or that all corrosion has been detected repaired and protected from further corrosion or corroded parts replaced then the inspection procedures must be repeated every three years using one of the accepted methods described in this Bulletin If additiona
13. must be controllable articulation of the last 4 to 5 inches of the tip to insure that all areas of the interior of the wing panel structure may be seen through the endoscope or borescope e Univair has evaluated and found acceptable the Olympus OSF endoscope sigmoidoscope with a Fujinon 150 light source for this alternate inspection means Other scopes and light sources meeting the minimum characteristics above may also be acceptable however no other equipment has been evaluated by Univair Remove self tapping sheet metal screws attaching fairing strips at gaps between center section and outer wing panels Remove fairings Univair Aircraft Corporation Service Bulletin No 31 page 4 of 9 For Method 3 Remove outer wing panels using following procedure for each wing This procedure is best accomplished by two or more people e Remove self tapping sheet metal screws attaching fairing strip at gap between center section and outer wing panel Remove fairing e Remove aileron push pull tube at aileron inboard end Disconnect electrical wires leading to wing tip navigation light landing light if installed and strobe light if installed Disconnect pitot and static line left outer panel only e Place a padded horse under wing tip or have someone support wing at its tip e Remove the two 5 16 inch bolts from the rear spar attachment fitting and the two 5 8 inch bolts from wing hinge fitting at main spar Remove outer wing pane
14. s highly recommended that the wing fuel tanks be removed to inspect the front side of the main wing spar even if no corrosion is found elsewhere 9 Repair Replace parts considered unairworthy parts that are damaged or parts with corrosion beyond light corrosion prior to further operation see Step 10 Remove all light corrosion in accordance with the procedures outlined in Chapter 6 Section 5 of 43 4A Clean and apply chemical conversion coating to the corrosion rework areas as outlined in Chapter 4 of AC 43 4A For further corrosion resistance a zinc chromate zinc oxide or two part epoxy listed on the following chart may be applied by spraying or brushing Univair Aircraft Corporation Service Bulletin No 31 page 6 of 9 after the chemical conversion coated surfaces have thoroughly dried Comply with safety procedures of AC 43 4A as well as paint manufacturer s safety preparation and application procedures during all phases of treating the corroded areas Be sure primer coating is applied evenly and smoothly so it won t be mistaken for corrosion on subsequent inspections Zinc Chromate primer coatings Zine Oxide primer coatings 2 Part Epoxy Primer Part Number Part Number Part Number Epibond off white Rand O Plate dark green ellow Tempo 7 6889 green Any other zinc chromate primer Any other epoxy primer system meeting meeting MIL P 23377 Class 1 TT P 1757 or Type 1 yellow Type 2 dark
15. t is highly recommended that the wing fuel tanks be removed to inspect the front side of the main wing spar even if no corrosion is found elsewhere Method 3 outer wing panel removal method On each side of the wing center section insert a bright light into the wing center section through the lightening holes in the center section ribs With the light a mirror and any other equipment deemed necessary inspect all areas of the wing center section structure through all necessary openings in the wing center section until it has been determined that all areas of the wing center section between the front and rear spars and aft of the rear spar not accessible from the cockpit have been inspected for corrosion and unrepaired damage FAA Advisory Circular AC 43 4A Corrosion Control for Aircraft dated 7 25 91 or later should be used to identify corroded areas Due to the extensive use of thin materials in the wing center section any parts with corrosion beyond light corrosion as defined in AC 43 4A Chapter 6 Section 4 paragraph 640 is considered unairworthy If corrosion is found on the rear side of the front spar or if corrosion is suspected for other reasons remove wing fuel tanks in accordance with the appropriate Service Manual and inspect the front side of the wing spars for corrosion required If no corrosion is found aft of the main wing spar wing tank removal is to be accomplished at the inspector s discretion However it i
16. tion in order to thoroughly inspect the wing center section Univair s concern with the wing removat method of inspection is that unless a qualified and experienced mechanic performs the wing removal and reinstallation worse damage may occur to the aircraft through the wing removal process than the corrosion may create if wing attach fittings are damaged it is difficult or impossible for the average mechanic or shop to replace the large rivets that attach the fittings to the wings Although the AD does not specifically mention removal of the wing fuel tanks Service Bulletin 31 requires that if any corrosion is found in the wing center section remove the wing tanks and inspect the front of the wing spar for corrosion Univair strongly recommends inspecting the areas between the fuel tanks and the front spar whether corrosion is found elsewhere not Please comply with the AD requirement to report any corrosion found to the FAA by submitting a Malfunction or Defect Report The FAA will share this information with Univair so that we know what direction to take in the design and manufacture of replacement parts for the Ercoupe Forney Alon Mooney M10 series aircraft ERCOUPE SERVICE BULLETIN No 31 Revision 1 SUBJECT Wing Center Section Inspection June 14 2002 SERVICE BULLETIN NO 31 WING CENTER SECTION INSPECTION REVISION 1 DATE June 14 2002 SUBJECT Visual inspection of wing center section s
17. tructure for evidence of corrosion and or damage MODELS AFFECTED All Ercoupe 415 C 415 CD 415 D 415 E and 415 G aircraft All Forney F 1 and F 1A aircraft All Alon A 2 and A 2A aircraft All Mooney M10 aircraft COMPLIANCE Initial inspection required within the next 12 calendar months or within the next 100 hours time in service or annual inspection whichever occurs first Continued inspections every three years or whenever additional corrosion is suspected whichever comes first PERSONNEL IMPORTANT All work and inspections required by this Service Bulletin are to be performed by a properly rated and equipped certified mechanic or repair station with experience in the work use of equipment inspections and repairs listed STATEMENT OF DIFFICULTY There have been field reports of severe corrosion in the wing center section structure of several aircraft Additional field reports indicate that hard landings or taxiing over rough terrain may transmit damaging loads to the rear spar carry through structure The most effective means of preventing corrosion damage is early identification and correction However the original design configuration does not provide adequate means for routine visual examination of the wing center section wing walkway boxes during periodic inspections Undetected corrosion or Univair Aircraft Corporation Service Bulletin No 31 page 2 of 9 undetected damage if severe enough could lead to structural fai
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