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# SERVICE BULLETIN SA226 SERIES



## FUSELAGEInspection and/or Replacement of the Left Hand and Right Hand Forward and Aft Wingto-Body Attach Fittings.

1. PLANNING INFORMATION A. Effectivity: All SA226-T/-T(B)/-TC/-AT Airplanes.

B. Reason: To provide operators with instructions for the inspection and /or replacement of the left hand and right hand forward and aft spar wing-to-body attach fittings. C. Description: Inspect the left hand and right hand forward and aft spar wing-to-body attach fittings for cracks. If cracks are found, replace fitting(s). D. Compliance: Highly Recommended For aircraft with more than 35,000 Total Aircraft Cycles (TAC), inspect within next 300 cycles from the date of this service bulletin. For aircraft with 20,000 - 35,000 Total Aircraft Cycles (TAC), inspect within next 500 cycles from the date of this service bulletin. For aircraft with 10,600 - 19,999 Total Aircraft Cycles (TAC), inspect within next 1,000 cycles from the date of this service bulletin. For aircraft with less than 10,600 Total Aircraft Cycles (TAC), inspect at 10,600 cycles or within the next 1,000 cycles, whichever occurs later.

TABLE 1 SA226-T/-T(B)/-AT/-TC, ALL

Bolts Replaced With Same Size

10,600 Cycles Original Fitting Bolts Replaced With Oversize

Replacement Fitting 16,600 Cycles 7,700 Cycles

13,100 Cycles Aircraft Cycles Until Recurrent Inspection

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# SERVICE BULLETIN SA226 SERIES

E. Approval: FAA Approved for Engineering Design. F. Manpower: The M7 Aerospace manhour estimate for this service bulletin is as follows: (1) 6 manhours for access to both spars (one side only). (2) 20 manhours for inspection (either method) for both spars (one side only). (3) 100 manhours per pair for replacement of fittings at one spar location only. This estimate is for direct labor only, accomplished by an experienced crew. Adjust the estimate with operator task-hour data if necessary. G. Material – Cost and Availability: (1) Cost: Because of pricing fluctuations, individual cost estimates should be obtained from your normal material procurement outlet. Additional material cost information may be contained in the Index or the Letter of Transmittal. (2) Availability:

Parts are available. H. Tooling – Price and Availability: For tools/kits identified in Supplement A of this service bulletin, contact Mr. Wayne Pickford at Perimeter Aviation, ph 204-791-9848, fax 204-480-4025. I. Weight and Balance: Negligible
NOTE: It is recommended the aircraft operating weight be reestablished after incorporating 20 service bulletins classified as having 'negligible' impact on aircraft weight and balance. This recommendation is derived from data provided in FAA Advisory Circular 120-27.
J. References: SA226/227 Structural Repair Manual.
SA226 Maintenance Manual.

NOTE: References are for manufacturer’s use only.

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# SERVICE BULLETIN SA226 SERIES

K. Other Publications Affected:
SA226 Maintenance Manual. SA226 Airframe Inspetion Manual, ST-UN-M002 SA226/227 Supplemental Inspection Document (SID)

2. ACCOMPLISHMENT INSTRUCTIONS The four (4) fastener locations fastening the Main (Fwd) spar wing-to-fuselage fittings to the spar must be inspected for cracks. Two inspection methods are permissible. A method has been developed to ultrasonically inspect the fittings without removing the fasteners, provided that there is adequate clearance between fastener head and wall of fitting for the tranducer head. Alternately, the fasteners can be removed and the open bore holes inspected using High Frequency Eddy Current (HFEC). The latter method requires additional labor hours and aircraft
access. Access requirements are detailed in step 2.A. Inspection methods are detailed in steps 2.B. and 2.C.

A. Access (1) Remove electrical power from aircraft. Turn off main batteries. Ensure GPU is not connected to aircraft. Tag out circuit breakers and battery switches to prevent injury to personnel or damage to the aircraft. (2) Remove interior furnishings, cabin seats, carpet, floorboards, and side panels as required to gain access to wing carry-thru area from inside the fuselage. (3) Gain access to wing-to-fuselage mount fittings, P/N 27-22121 and 27-22123 at main spar, P/N 27-22135 and 27-22136 at aft spar. (4) At the main spar, remove sealant around the heads of the four fasteners in the base of the fittings (attached to upper spar cap) as necessary to allow inspection per steps 2.B., 2.C., and 2.D. (See Figure 1) (5) At the main and aft spars, remove sealant obscuring the upper outboard fillet radii as necessary to allow inspection per 2.B., 2.C., and 2.D. (See Figure 1) If the fastener bore eddy current inspection method is used (see step 2.B.), continue with steps (6) through (14). Otherwise go to step 2.C. (6) Defuel aircraft and sump fuel in accordance with SA226 Maintenance Manual 12- 30-15. (7) Lift and shore aircraft per SA226 Maintenance Manual 07-10-00. Use fuselage and wing cradles.

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# SERVICE BULLETIN SA226 SERIES

(8) Remove wing belly skins and wing-to-fuselage fairings from WS 27 RH to WS 27 LH fore and aft of the main spar. Note size and type of fasteners for reinstallation. (9) Remove accessories, plumbing, and equipment as required for access to the main spar pressure plate outboard (approx. BL 22) access panels. (10) Remove front and aft side main pressure plate access panels. (11) Remove forward collector tank access panel in WS 27 rib web and upper collector tank baffle. (12) Remove under wing access panel, forward of spar and immediately outboard of WS 27. (13) Remove air conditioning duct valve, anti-ice valve, and water separator inside under-wing access panel. Bag and tag ends of tubes and parts for reinstallation. (14) Remove inboard and outboard tension bolts through spar cap from main spar forward and aft fitting halves (see Figure 1). The fasteners will be replaced with new hardware.

NOTE : Fastener heads may be ground off to facilitate removal. Take care not to damage fitting. Before punching fasteners through into the spar and wing interor, check to ensure clearance with other fasteners through spar and WS 27 rib webs below. Remove other fasteners as necessary to avoid damage. For repair of damaged holes, see step 3. of this bulletin. B. Main spar fitting fastener bore eddy current inspection At the main spar LH and RH wing-to-fuselage fittings (see Figure 2 for probable crack locations): (1) High Frequency Eddy Current (HFEC) inspect the inside diameter of the open bolt holes in the wing-to-fuselage fittings per SA226/227 Structural Repair Manual (SRM) 51-30-07. (2) Proceed to step 2.D. C. Main spar fitting endpad ultrasonic inspection At the main spar LH and RH wing-to-fuselage fittings: (1) Using the method detailed in Supplement A to this service bulletin for aircraft listed in Table 3 , inspect the endpad fitting surface around the heads of the four tension bolt fasteners. See Figure 2 for probable crack locations. If unable to use this method as outlined in Supplement A, step 7 Note, then method per step 2.B. shall be used.

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# SERVICE BULLETIN SA226 SERIES

D. Main spar fitting radii inspection At the main spar LH & RH wing-to-fuselage fittings: (1) High Frequency Eddy Current (HFEC) inspect per SA226/227 Structural Repair Manual 51-30-07 the upper edge of the inboard gusset on both fitting halves. See Figure 2 for probable crack locations. (2) High Frequency Eddy Current (HFEC) inspect per SA226/227 Structural Repair Manual 51-30-07 in the fillet radii of the upper outboard corner on both fitting halves. See Figure 2 for probable crack locations.

NOTE : There is one further inspection required if the main spar fittings are removed and replaced. See steps G.(1)(l). E. Aft spar fitting inspection (1) At the aft spar LH and RH wing-to-fuselage fittings inspect for cracks in the fillet radii of the upper outboard corner on both fitting halves using High Frequency Eddy Current methods in accordance with SA226/227 Structural Repair Manual (SRM) 51-30-07. F. Disposition (1) If a crack is found in any one of the fitting halves, remove and replace both fitting halves. See step G. for removal instructions. See step K. for reporting instructions. (2) If hardware was removed at the main spar fitting and no crack indications were found, wet install new hardware per SA226/227 Structural Repair Manual (SRM) 51-30-03.

Inboard Bolts MS20005-25 Bolt, MS20002C5 Washer, 52LH4367-054 Nut, 4367-05 Washer
Outboard Bolts MS20005-23 Bolt, MS20002C5 Washer, 52LH4367-054 Nut, 4367-05 Washer (3) Torque bolts to 190 - 220 in-lbs in accordance with SA226/227 Structural Repair Manual (SRM) 51-40-07 using a cross sequence tightening schedule (e.g., 12 o'clock to 6 o'clock, 3 o'clock to 9 o'clock, 12:05 o'clock to 6:05 o'clock, etc.).

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# SERVICE BULLETIN SA226 SERIES

(4) Reseal the area where sealant was removed earlier and overcoat nuts in wet fuel tank per SA226/227 Structural Repair Manual (SRM) 51-30-03. G. Removal and Replacement Remove and replace both fitting halves at any location where cracks are found. (1) Main Spar Fittings If bolts have already been removed from fitting for bolt hole inspection, skip to step G.(1)(j). (a) Defuel aircraft and sump fuel in accordance with SA226 Maintenance Manual 12-30-15. (b) Lift and shore aircraft in accordance with SA226 Maintenance Manual 07-10-00. (c) Remove wing belly skins and wing-to-fuselage fairings fore and aft of the main spar. Note size and type of fasteners for reinstallation. (d) Remove accessories, plumbing, and equipment as required for access to the main spar pressure plate outboard (approx. BL 22) access panels. (e) Remove front and aft side main pressure plate access panels. (f) Remove forward collector tank access panel in WS 27 rib web and upper collector tank baffle. (g) Remove under wing access panel, forward of spar and immediately outboard of WS 27. (h) Remove air conditioning duct valve, anti-ice valve, and water separator inside under-wing access panel. Bag and tag ends of tubes and parts for reinstallation. (i) Remove fitting hardware through spar cap. (Refer to step 2.(A)(14)). (j) Remove fitting hardware through fuselage frame webs. (k) Remove 27-22118 Mount Assembly. Permissible to trim 27-22025 Doubler on inner frame cap in accordance with Figure 5 if necessary to remove Mount Assy. Retain shims between frame and fittings noting orientation and location for later installation. (l) High frequency Eddy Current (HFEC) inspect the inside diameter of the open bolt holes (4) in the titanium upper spar cap per SA226/227 Structural Repair Manual (SRM) 51-30-07. Contact M7 Engineering if a crack is found. (m) Build a tooling fixture to capture locations of holes in spar cap.

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# SERVICE BULLETIN SA226 SERIES

(n) Duplicate holes from fixture to new fitting halves. Hole size 0.312/0.316" diameter. Deburr. (o) Assemble the 27-22121 and 27-22123 fitting halves to form the 27-22118 Mount Assembly (Figure 3). (p) Install mount assembly in accordance with the following installation notes: 1 Permissable to remove 0.060" material locally from underside of base of mount assy to match irregularities of mating spar caps. Fittings must maintain minimum base thickness of 0.290". Alodine and prime any reworked surfaces and bare edges per SA226/227 Structural Repair Manual (SRM) 51-30-02. Ensure that more than one-half of forward and aft edge of mount assy is in contact with spar caps. Max allowable remaining gap is 0.020". Fill remaining gaps with Devcon-F per step 2.G.(1)(p) 2. 2 Apply Devcon-F (putty type) between mating surfaces of mount assy and spar to fill any existing gaps less than 0.020" after mount assy is made to contact spar cap along more than half of both fwd and aft edges. Prior to application of Devcon-F, clean and treat mating surfaces with Devcon release agent. 3 Replace bolts and wet install per SA226/227 Structural Repair Manual (SRM) 51-30-03 through spar cap:

Inboard Bolts MS20005-25 Bolt, MS20002C5 Washer, 52LH4367-054 Nut, 4367-05 Washer
Outboard Bolts MS20005-23 Bolt, MS20002C5 Washer, 52LH4367-054 Nut, 4367-05 Washer 4 Torque MS20005 bolts through spar cap to 190 - 220 in-lbs in accordance with SA226/227 Structural Repair Manual (SRM) 51-40-07 using a cross sequence tightening schedule (e.g., 12 o'clock to 6 o'clock, 3 o'clock to 9 o'clock, 12:05 o'clock to 6:05 o'clock, etc.). Overcoat all nuts in fuel tank with sealant per SA226/227 Structural Repair Manual (SRM) 51-30-03. (q) Pick up existing fastener holes through frame webs. Hole size 0.190/0.194" diameter. Reinstall any shims between frame web and fittings that were existing

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# SERVICE BULLETIN SA226 SERIES

in same location/orientation as previous. Shims shall be fay surface sealed per SA226/227 Structural Repair Manual (SRM) 51-30-03. Contact M7 Aerospace if new shims are required (see Note 4, Figures 3 and 4). (r) Pick up existing fastener holes through 27-31264 Support Clips. Maintain fastener type and size. (2) Aft Spar Fittings (a) Defuel aircraft and sump fuel in accordance with SA226 Maintenance Manual 12-30-15. (b) Lift and shore aircraft in accordance with SA226 Maintenance Manual 07-10-00. Use fuselage and wing cradles. (c) Remove wing belly skins and wing-to-fuselage fairings fore and aft of the aft spar. Note size and type of fasteners for reinstallation. (d) Remove accessories, plumbing, and equipment as required for access to the aft spar pressure plate outboard (approx. BL 22) access panels. (e) Remove front and aft side aft spar pressure plate access panels. (f) Remove aft collector tank access panel in WS 27 rib web and upper collector tank baffle. (g) Remove 27-71003 or 27-19097 Tube Assy (aileron control system). (h) Remove flap walking beam. (i) Remove flap. (j) Remove or secure inboard flap hinge linkage parts to allow clear access to nut side of aft, outboard fitting bolt. (k) Remove fitting hardware through spar cap. (Refer to step 2.(A)(14) NOTE , apply to aft spar). (l) Remove fitting hardware through fuselage frame webs. (m) Remove 27-22119 Mount Assy. Permissible to trim 27-22025 Doubler on inner frame cap in accordance with Figure 5 if necessary to remove Mount Assy. Retainshims between frame and fittings noting orientation and location for later installation. (n) Build a tooling fixture to capture locations of holes in spar cap. (o) Duplicate holes from fixture to new fitting halves. Hole size 0.250/0.254" diameter. Deburr.

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# SERVICE BULLETIN SA226 SERIES

(p) Assemble the 27-22135 and 27-22136 fitting halves to form the 27-22119 Mount Assembly (Figure 4). (q) Install mount assembly in accordance with the following installation notes: 1 Permissable to remove 0.060" material locally from underside of base of mount assy to match irregularities of mating spar caps. Fittings must maintain minimum base thickness of 0.290". Alodine and prime any reworked surfaces and bare edges per SA226/227 Structural Repair Manual (SRM) 51-30-02. Ensure that more than one-half of forward and aft edge of mount assy is in contact with spar caps. Max allowable remaining gap is 0.020". Fill remaining gaps with Devcon-F per step 2.G.(2)(q) 2. 2 Apply Devcon-F (putty type) between mating surfaces of mount assy and spar to fill any existing gaps less than 0.020" after mount assy is made to contact spar cap along more than half of both fwd and aft edges. Prior to application of Devcon-F, clean and treat mating surfaces with Devcon release agent. 3 Replace 4 bolts and wet install per SA226/227 Structural Repair Manual (SRM) 51-30-03 through spar cap:
MS20004-22 Bolt, Aft, Outbd & Inbd MS20004-24 Bolt, Fwd, Outbd MS20004-26 Bolt, Fwd, Inbd MS20002C4 Washer, 52LH4367-048 Nut, RM2935-04 Washer 4 Torque MS20004 bolts through spar cap to 100 - 140 in-lbs in accordance with SA226/227 Structural Repair Manual (SRM) 51-40-07 using a cross sequence tightening schedule (e.g., 12 o'clock to 6 o'clock, 3 o'clock to 9 o'clock, 12:05 o'clock to 6:05 o'clock, etc.). Overcoat all nuts in fuel tank with sealant per SA226/227 Structural Repair Manual (SRM) 51-30-03. (r) Pick up existing fastener holes through frame webs. Hole size 0.190/0.194" diameter. (s) Pick up existing fastener holes through 27-30000-087/-088 Bracket on fwd side. Maintain fastener type and size. H. Close Up (1) Reinstall any fasteners through the spar web or WS 27 rib web that were removed to facilitate removal of fitting tension bolts through spar cap. Reinstall same type and size in accordance with SA226/227 Structural Repair Manual (SRM) 51-40- 07.

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# SERVICE BULLETIN SA226 SERIES

(2) Ensure area is fillet sealed and overcoat fasteners in wet fuel tank per SA226/227 Structural Repair Manual (SRM) 51-30-03. (3) Restore collector tank, reseal fasteners, and close collector tank access panel. (4) Reinstall spar access panels and center section equipment and systems per applicable sections of the SA226 Maintenance Manual. (5) Reinstall air conditioning duct valve, anti-ice valve, and water separator and reinstall under-wing access panel. (6) Remove shoring. (7) Refuel aircraft and check for leaks.(8) Reinstall wing-to-fuselage fairing and interior parts and components per applicable sections of the SA226 Maintenance Manual. (9) If aft spar fittings were replaced, continue through step H.(12). Otherwise proceed to step 2.I. (10) Reinstall flap and flap walking beam. (11) Reinstall 27-71003 or 27-19097 Tube Assy (aileron control system). (12) Remove tags from battery switches and circuit breakers pulled in step 2.A.(1). Connect GPU to aircraft. (13) Perform aileron control system operational checks in accordance with SA226 Maintenance Manual 27-10-10. (14) Perform flap control system operational checks in accordance with SA226 Maintenance Manual 27-50-10. I. Complete maintenance entry per 14 CFR 43.9. J. Complete and return Service Bulletin Compliance Form to M7 Aerospace Technical Publications. K. Reporting requirements Damage reporting is required to ensure compliance times are validated. If a crack is found at any location, the following information needs to be relayed to M7 Engineering as soon as possible. (1) State length of crack and a general description of the damage. (2) State aircraft model, serial number, aircraft total flight cycles and total flight hours.

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# SERVICE BULLETIN SA226 SERIES

(3) Using Figure 2, indicate location of damage, show forward orientation using arrows, and orientation of crack. (4) State whether the aircraft has had or is suspected of having a hard landing in the past. (5) Send this information to M7 Technical Support at MetroTech@M7Aerospace.com or (210)-824-9421, ext. 7294.

3. REPAIR OF DAMAGED FASTENER HOLES Damaged fastener holes in the base of the fitting and spar cap (fasteners attaching the fitting to the spar cap) may be repaired within the following parameters. A. Holes may be enlarged for the first oversize, second oversize, or the next full size fastener. (See Table 2) B. Torque settings for fastener installation. Refer to SA226/227 Structural Repair Manual (SRM) 51-40-07 for guidance. Torque fasteners using a cross sequence tightening schedule (e.g., 12 o'clock to 6 o'clock, 3 o'clock to 9 o'clock, 12:05 o'clock to 6:05 o'clock, etc.). (1) 1/4 in. nut 100 - 140 in-lbs. (2) 5/16 in. nut 190 - 220 in-lbs. (3) 3/8 in. nut 220 - 360 in-lbs. C. Washers under heads of fasteners may be trimmed or chamfered to avoid interference with fitting fillet radii. Maintain a full bearing surface for the head of the fastener. D. If a 3/8 in. diameter fastener is used in any main spar inboard location, then all four fasteners at this fitting location must be increased to 3/8 in. diameter. (See Table 2)

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# SERVICE BULLETIN SA226 SERIES

TABLE 2 

## Oversize Hardware for Hole Repair Main Spar Inbd Main Spar Outbd Aft Spar, Aft Fitting

1st Oversize (0.0156) 0.332/0.328 Dia. Hole NAS6205-25X Bolt * NAS1149F0563P Washer 52LH4367-054 Nut

4367-05 Washer



## * If this fastener is too close to the fitting gusset to permit proper installation, a radius block of sufficient thickness to lift the head above the gusset may be employed. Create radius block from 2024-T3 per AMS-QQ-A-250/4. Size to be no less than washer diameter. Max thickness = 0.30 inches. Machine radius to match fitting fillet radius. Finish in accordance with SA226/227 Structural Repair Manual (SRM) 51-30-02. Adjust fastener length accordingly. 0.332/0.328 Dia. Hole NAS6205-23X Bolt * NAS1149F0563P Washer 52LH4367-054 Nut

4367-05 Washer 0.266/0.270 Dia. Hole NAS6204-22X Bolt NAS1149F0463P Washer 52LH4367-048 Nut RM2935-04 Washer
0.348/0.344 Dia. Hole NAS6205-25Y Bolt * NAS1149F0663P Washer 52LH4367-054 Nut

4367-05 Washer 0.348/0.344 Dia. Hole NAS6205-23Y Bolt * NAS1149F0663P Washer 52LH4367-054 Nut

4367-05 Washer 0.285/0.281 Dia. Hole NAS6204-22Y Bolt NAS1149F0563P Washer 52LH4367-048 Nut RM2935-04 Washer 

### 2nd Oversize (0.0312)

0.379/0.375 Dia. Hole MS20006-25 Bolt MS20002C6 Washer 52LH4367-064 Nut

4367-06 Washer **See 3.D. below** 

### Next Size 0.379/0.375 Dia. Hole MS20006-25 Bolt MS20002C6 Washer 52LH4367-064 Nut

4367-06 Washer 0.316/0.312 Dia. Hole MS20005-22 Bolt MS20002C5 Washer 52LH4367-054 Nut RM2935-05 Washer 

## Aft Spar, Fwd Fitting

0.266/0.270 Dia. Hole NAS6204-24X Bolt (Outbd) NAS6204-26X Bolt (Inbd) NAS1149F0463P Washer 52LH4367-048 Nut RM2935-04 Washer 0.285/0.281 Dia. Hole NAS6204-24Y Bolt (Outbd) NAS6204-26Y Bolt (Inbd) NAS1149F0563P Washer 52LH4367-048 Nut RM2935-04 Washer 0.316/0.312 Dia. Hole MS20005-24 Bolt (Outbd) MS20005-26 Bolt (Inbd)

MS20002C5 Washer 52LH4367-054 Nut RM2935-05 Washer

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# SERVICE BULLETIN SA226 SERIES



## 4. MATERIAL LISTING

TABLE 3 

## Replacement Wing-to-Fuselage Attach Fitting Part Numbers <1>

Aircraft Model Serial Number Main Spar Aft Spar
27-22121 27-22123 

## SA226-T SA226-T(B) SA226-TC SA226-AT 201 - 291 276 - 324 201 - 320 001 - 074 -013/-014 -013/-014 -007/-008 -007/-008

SA226-T(B) SA226-TC 325 - 391 321 - 396 -015/-016 -015/-016 -007/-008 -007/-008

SA226-T(B) SA226-TC 394 - 417 398 - 419 -019/-020 -019/-020 -007/-008 -007/-008 27-22135 27-22136



## <1> New replacements have recurring inspections per Table 1 since installation. This bulletin shall be used to detail inspections and instructions.

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# SERVICE BULLETIN SA226 SERIES

Fitting-to-Spar Hardware and Alternates

Location Existing Alternate 1

Main Spar

Inboard MS20005-25 Bolt



### Notes:
1. Alternate parts vary in size from existing parts and may not fit depending on fastener location.
2. The four fasteners at one location must be of the same type. The four fasteners must be substituted together. MS21250-05025 Bolt 2
MS20002C5 Washer
52LH4367-054 Nut

4367-05 Washer NAS1727-5N Nut & Washer Combo

Main Spar Outboard MS20005-23 Bolt
MS20002C5 Washer
52LH4367-054 Nut

4367-05 Washer MS21250-05023 Bolt 2

NAS1727-5N Nut &

Washer Combo

Aft Spar, Aft Side MS20004-22 Bolt MS21250-04022 Bolt 2

MS20002C4 Washer

52LH4367-048 Nut NAS1727-4N Nut & Washer Combo RM2935-04 Washer

Aft Spar, Fwd Side MS20004-24 Bolt (Outbd) MS20004-26 Bolt (Inbd)

MS20002C4 Washer

52LH4367-048 Nut

RM2935-04 Washer MS21250-04024 Bolt 2

MS21250-04026 Bolt 2

NAS1727-4N Nut &

Washer Combo



### TABLE 4

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# SERVICE BULLETIN SA226 SERIES



# B **B**

Note 2 (2 Places) 

# A **A**

Note 2 (2 Places)

Note 1 (4 Places)



### Notes: 1. Remove sealant from around 4 fastener heads in base of fittings. 2. Remove sealant in fillet radius at upper edge and approximately 1 inch along inside vertical corner. 3. For inspection per 2.B., remove inboard and outboard bolts in both fitting halves. Note 3



### Aft Spar Fitting Main Spar Fitting



### FIGURE 1

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# SERVICE BULLETIN SA226 SERIES

PROBABLE CRACK LOCATIONS FIGURE 2 Crack along fillet radius from upper edge (both fitting halves)

Crack starts from bolt hole and may extend through gusset

Crack may form around periphery of outboard holes

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# SERVICE BULLETIN SA226 SERIES

0.190/0.194 Dia Hole (Pick up pilot holes in 27-22124 Splice Plate) NAS1303-4 Bolt NAS1149F0332P Washer MS21042-3 Nut (2 Places) (See Note 1) 0.190/0.194 Dia Hole (Pick up pilot holes in 27-22124 Splice Plate) NAS1303-5 Bolt NAS1149F0332P Washer MS21042-3 Nut (16 Places) 4.064 (See Note 1)

3.534 (See Note 2) See Note 4

27-22121 Fitting

27-22123 Fitting

27-22124 Splice Plate (See Note 3)
27-22124 Splice Strap (See Note 1) 0.23

0.05 (Min. clearance)



### Note 1: Effective for SA226-T(B) 394 and up, TC 398 and up. Note 2: Effective for all SA226 serial numbers not covered by Note 1. Note 3: Fay surface seal in accordance with SA226/227 Structural Repair Manual 51-30-03. Note 4: Dimensions shown are design parameters. Adjust to match aircraft conditions if necessary. Maintain 2D edge distance on all fastener locations. Outboard Up
Aft Up

0.60



### FIGURE 3 MAIN SPAR (LH SHOWN, RH OPPOSITE)

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# SERVICE BULLETIN SA226 SERIES

0.91 0.34

27-22137 Splice Plate (See Note 3) 27-22136 Fitting 2.538 (See Note 1)

2.478 (See Note 2)

27-22135 Fitting

0.190/0.194 Dia Hole (Pick up pilot holes in 27-22137 Splice Plate) MS24694-S54 Screw NAS1149F0332P Washer MS21042-3 Nut (4 Places)
0.190/0.194 Dia Hole (Pick up pilot holes in 27-22137 Splice Plate) NAS1303-5 Bolt NAS1149F0332P Washer MS21042-3 Nut (6 Places) See Note 4



### Note 1: Effective for SA226-T(B) 394 and up, TC 398 and up. Note 2: Effective for all SA226 serial numbers not covered by Note 1. Note 3: Fay surface seal in accordance with SA226/227 Structural Repair Manual 51-30-03. Note 4: Dimensions shown are design parameters. Adjust to match aircraft conditions if necessary. Maintain 2D edge distance on all fastener locations. Outboard Up

Aft Up



### FIGURE 4 AFT SPAR (LH SHOWN, RH OPPOSITE)

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# SERVICE BULLETIN SA226 SERIES

VIEW LOOKING AFT LH SIDE

NOTES:

1. Permissible to trim edge of doubler cutout flush with frame web.

2. Permissible to trim corner to minimum 0.50 radius.
3. The Main Spar is shown but similar modifications are allowed to the 27-22025 Doubler at the Aft Spar location.
4. Conversion coat and prime trimmed edges per SA226/227 Structural Repair Manual (SRM) 51-30-02.



### FIGURE 5

### Technique 001 Wing to Fuselage Mount Ultrasonic Inspection Technique

UT Wing to Fuselage Mount Technique Page 1 of 17 22 June 2012 

# SUPPLEMENT A – SB 226-53-016

1. Applicable Specifications Technique 001
2. Applicability Fairchild Metro SA226 and SA227 aircraft. Aircraft have been divided by serial number, into 3 groups, based upon type of fitting installed on aircraft.

3. Purpose The purpose of this technique is to define the requirements for the Contact Ultrasonic Inspection of Wing to Fwd Fuselage Mount for the detection of minimum 0.06” Bolt-hole Cracks with the Bolts in-situ. Refer to Figure 1 for on-aircraft Fuselage Mount locations.

4. Personnel Requirements
Inspection, including interpretation and evaluation of results, shall be performed by an experienced Level 2 or 3 Ultrasonic Technician, qualified and certified to a standard acceptable to the Operator and Local Regulatory Authority. This technique assumes that such technicians are skilled in the orientation and interpretation of results obtained with the test equipm ent; it only supplies information on how to apply these skills to Fairchild Metro Aircraft. The technician must also have a good working knowledge of aircraft structures, a comprehension of failure characteristics of various metals used in aircraft structures and must know the limitations of nondestructive testing available as applied to the aircraft. Outbd View Inbd/Top View

FIGURE 1 Location of Forward Fuselage Mount (R ight Side Shown, Left Side Typical) Qty. (4) bolt-hole locations to be inspected

using this technique Group 1 SA226-T S/N 201-291 SA226-T(B) S/N 276-324

SA226-TC S/N 201-320 SA226-AT S/N 001-074 Group 2 SA226-T(B) S/N 325-391

SA226-TC S/N 321-396 Group 3 SA226-T(B) S/N 394-417

SA226-TC S/N 398-419 SA227 All models including commuters SA227-CC/DC

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5. Equipment A) Panametrics Epoch 4 Flaw Detector or equivalent with charger & BNC / Microdot Co-axial cable. B) Techna NDT Contact Shear Wave 10MHz Transduc ers as follows (no subs titutions allowed): i) 45°A: P/N TEK-5566 (0.25” x 0.20” long housing – See Figure 2A) ii) 30°A: P/N TEK-5565 (0.20” x 0.16” long housing – See Figure 2B) iii) 30°A: P/N TEK-5568 (See Figure 2C) C) Couplant: Light Oil. D) Reference Standard Part Number NDT001 (See Figure 5) E) Inspection Check Fixture, Group 1, 2 or 3 (See Figures 4A to 4F) F) Techna AMF-MR-8FX Flexible Ext ensions as required - 90° microdot offset preferred (See Figure 3). G) Inspection Kit Qty. (3) Check Fixture Templates (group 1,2 and 3), Qty. (2) Bolt Locating Plugs, Qty. (1) Co axial cable Qty. (1) Reference standard Qty. (3) Transducers and Qty (2) Flexible extensions (kit contains all items needed for inspection ex cept flaw detector and couplant oil)

FIGURE 2A TD P/N TEK-5566 FIGURE 2B TD P/N TEK

- 5565 FIGURE 2C TD P/N TEK-5568

FIGURE 3 Techna AMF-MR-8FX Flexible Extensions

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6. Identity aircraft by serial number and use appropriate check fixture, group 1,2 or 3
7. (Group 1) Part Preparation and Inspection Limitations Top Surface and Inboard / Outboard Edges of Mount shall be sufficiently exposed to allow transducer manipulation, and shall be free of sealant, loose paint and any debris that could impair Ultrasonic Inspection. *Note: 100% inspection of all Fitting Mounts may not be possible due to relative positioning of insitu bolt holes in relation to center web and outer radii. Use of Inspection Check Fixture Group 1, which includes a Check Fixture Template and Qty. (2) Bolt Locating Plugs, is required prior to proceeding with inspection set out in this techni que. If entire circumference of all holes cannot be inspected, this technique shall not be used.
7.1 Use of Inspection Check Fixture Group 1

A) Insert Bolt Locating Plugs in both fastener heads and position Check Fixture Template over each Fitting Mount, flush to Locating Plugs, as shown in Figure 4B. Assure that edge labeled Inboard (IB) is positioned accordingly. Template shall be reversed for use on opposite Fitting Mount. *Note: Prior to Check Fixture Template use, remove all fasteners that impede intimate contact with Locating Plugs and Fitting Mount surfaces including Center Web as shown in Figure 4B. B) Entire circumference of both Bolt Locating Pl ugs shall be within the boundaries scribed on the Check Fixture Template (See Figure 4B). Holes associ ated with any plugs that fall outside the defined boundaries cannot be 100% inspected, and this technique shall not be used.

FIGURE 4B Use of Group 1Check Fixture T emplate + Bolt Locating Plugs FIGURE 4A Check Fixture Template Group 1 Ins p ection Area Ins p ection Area

Bolt Locating Plugs (seated in Fastener head)

Check Fixture Template Orientate This Side Inboard

Scribed Go/No-Go Inspection Boundary Scribed Go/No-Go Inspection Boundary

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8. (Group 2) Part Preparation and Inspection Limitations Top Surface and Inboard / Outboard Edges of Mount shall be sufficiently exposed to allow transducer manipulation, and shall be free of sealant, loose paint and any debris that could impair Ultrasonic Inspection. *Note: 100% inspection of all Fitting Mounts may not be possible due to relative positioning of insitu bolt holes in relation to center web and outer radii. Use of Inspection Check Fixture group 2, which includes a Check Fixture Template and Qty. (2) Bolt Locating Plugs, is required prior to proceeding with inspection set out in this techni que. If entire circumference of all holes cannot be inspected, this technique shall not be used.
8.1 Use of Inspection Check Fixture Group 2 :

A) Insert Bolt Locating Plugs in both fastener heads and position Check Fixture Template over each Fitting Mount, flush to Locating Plugs, as shown in Figure 4D. Assure that edge labeled Inboard (IB) is positioned accordingly. Template shall be reversed for use on opposite Fitting Mount. *Note: Prior to Check Fixture Template use, remove all fasteners that impede intimate contact with Locating Plugs and Fitting Mount surfaces including Center Web as shown in Figure 4D. B) Entire circumference of both Bolt Locating Pl ugs shall be within the boundaries scribed on the Check Fixture Template (See Figure 4D). Holes associ ated with any plugs that fall outside the defined boundaries cannot be 100% inspected, and this technique shall not be used.

FIGURE 4D Use of Group 2 Check Fixture T emplate + Bolt Locating Plugs FIGURE 4C Check Fixture Template Group 2 Inspection Area Inspection Area

Bolt Locating Plugs (seated in Fastener head)

Check Fixture Template Orientate This Side Inboard

Scribed Go/No-Go Inspection Boundary Scribed Go/No-Go Inspection Boundary IB

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9. (Group 3) Part Preparation and Inspection Limitations Top Surface and Inboard / Outboard Edges of Mount shall be sufficiently exposed to allow transducer manipulation, and shall be free of sealant, loose paint and any debris that could impair Ultrasonic Inspection. *Note: 100% inspection of all Fitting Mounts may not be possible due to relative positioning of insitu bolt holes in relation to center web and outer radii. Use of Inspection Check Fixture group 3, which includes a Check Fixture Templates (2) and Qty. (2) Bolt Locating Plugs, is required prior to proceeding with inspection set out in this tec hnique. If entire circumference of all holes cannot be inspected, this technique shall not be used.
9.1 Use of Inspection Check Fixture Group 3 (consists of qty 2 templates the narrow of which is used for the outboard side of the fitting):

A) Insert Bolt Locating Plugs in both fastener heads and position Check Fixture Template over each Fitting Mount, flush to Locating Plugs, as shown in Figure 4F. Assure that edge labeled Inboard (IB) is positioned accordingly. Templates shall be reversed for use on opposite Fitting Mount. *Note: Prior to Check Fixture Template use, remove a ll fasteners that impede intimate contact with Locating Plugs and Fitting Mount surfaces including Center Web as shown in Figure 4F. B) Entire circumference of both Bolt Locating Plugs shall be within the boundaries scribed on the Check Fixture Template (See Figure 4F). Holes associated with any plugs that fall outsi de the defined boundaries cannot be 100% inspected, and this technique shall not be used. FIGURE 4E Check Fixture Templates Qty (2 pieces) one wide and one narrow Inspection Area Inspection Area

FIGURE 4F Use of Group 3 Check Fixture T emplate + Bolt Locating Plugs Bolt Locating Plugs (seated in Fastener head)

Check Fixture Template (Narrow) Orientate This Side Inboard

Scribed Go/No-Go Inspection Boundary Scribed Go/No-Go Inspection Boundary Orientate This Side Inboard

Check Fixture Template (Wide) 3A Wide 3B Narrow

IB IB

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10. Reference Standards
A) The Reference Standard is Part Number NDT001 as shown in Figure 5, and is representative of parts being inspected in composition, condition, surface finish, approximate dimensions, and significant processes. B) The Reference Standard is nominal .380” thick, and contains Qty. (2) ~ .315” diameter holes with nominal 0.060” EDM corner Notches: (2) common to the upper surface (see Items A & B), and (2) common to the lower surface (see Items C & D) as shown in Figure 5. Notches are 0.06” long on bolt-hole surface x 0.60” long on the bolt-hole bore.

Note : Detection of 0.060” Top & Bottom Corner Notches around the entire Hole Circumference was verified during technique development using the Trans ducers specified in this technique.

A

FIGURE 5 Reference Standard NDT001 (curvature not depicted for clarity)

Qty. (2) .315” ± .030” diam.

holes with qty. (4) EDMnotches: .060” long on bolthole surface and bore

Qty. (4) EDM notches: .060” long on bolt-hole surface and bore

.380” nominal 1.775” ± 0.030”

2.835” ± 0.030” B D C NDT001

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11. Inspection Plan (Refer to Figures 6A and 6B for Typical Scanning Surfaces for each Mount Fitting) A) The Ultrasonic Inspection of the Fuselage Mount s shall be performed in accordance with Section 11 of this technique. B) Ultrasonic Inspection coverage shall be 100% of the entire circumference of qty. (4) holes (top and bottom) in both left side Mount and right side Mount pairings (qty. 2 holes each). C) The inspection method is Manual Contact A ngle Beam, and shall be performed from the Top Surface, Inboard and Outboard Edges of each Moun t. Refer to Figures 6A and 6B for inspection surfaces. D) The 30° Angle Beam Transducer P/N TEK-5565 (o r alternate TEK-5568 if space permits) shall be used for inspection from the Inboard and Outboar d Edges for the detection of top and bottom surface bolt-hole cracks (See Figures 6A & 6B). E) The 30° Angle Beam Transducer P/N TEK-5565 (o r alternate TEK-5568 if space permits) shall be used from the Top Surface for the detection of top surface bolt-hole cracks (See Figures 6A & 6B). F) The 45° Angle Beam Transducer (P/N TEK-5566) shall be used from the Top Surface for the detection of bottom surface bolt-hole cracks (See Figures 6A & 6B).

FIGURE 6B Mount – T yp ical Plan View and Transducer Scannin g Placement Inbd Ed g e Outbd Ed g e

FIGURE 6A Mount – Typical Side View a nd Transducer Scanning Placement (curvature not depicted for clarity) Top Surface Top Surface

Top Surface Top Surface Inbd Ed g e Outbd Ed g e

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12. Instrument Settings Panametrics Epoch 4: Gain: Cal. Gain & Scan Gain (as required) Wave: Fullwave Reject: 0% Energy: Max Range: 1.500 in. Damping: 50 Ω Velocity: 0.1230 in/usec. Mode: Pulse-Echo Zero:  0.000 usec. Band: > 8.0 Mhz Angle: 0° Pulser: Square Thickness: 0.000 in. Echo Trigger: Edge *Gate to be adjusted to monitor area of interest.

*Note: Settings defined above are recommended. Alte rnate settings may be used provided that calibration parameters defined in Section 13 can be achi eved. If an equivalent Flaw Detector Instrument is used, settings shall be similarly adjusted to optim ize defect detection as specified in Section 13.

13. Calibration Calibration shall be performed using Reference St andard NDT001 immediately prior to and after part inspection, whenever an indication is detec ted, and anytime Calibration is suspect.
Calibration is required for each transducer / inspec tion set-up to establish baseline amplitude and time base reference points, and to provide technician with typical signal presentation of defect coming off bolt hole. Depending on differences between Reference Standard and Inspection Specimen, on-aircraft adjustment may be required as specified in Section 14.
A) Surface Scan: Bottom Notch (See Figure 7) 1) Connect the 45° TEK-5566 Angle Beam Transducer. Position at ~1⁄2 Sk ip from the Bolt-hole as shown in Figure 7 (Surface distance from transducer exit poi nt to edge of hole for bottom reflection should be ~ .380”, aim towards bolt-hole and maximize response. 2) Position front surface response on left side of scr een and the 1⁄2 Skip Bolt-hole signal at mid screen. Adjust gain to set signal from bolt hole to 100% Full Screen Height. 3) Using the bolt-hole response as a reference, mani pulate the Transducer using a rotational and orbital motion (See Figure 8) to produce a response from the Bottom Surface EDM Notch (See defects C and D in Figure 7). Maximize defect response. You should be able to separate this indication from the Bolt-hole response so that it is easily discernible, and signal amplitude from EDM Notch is minimum 50% Full Screen Height. Screen presentation of signal separation will appear as shown in Figure 11B.

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A

B D C

FIGURE 7 45° TEK-5566 Calibration

FIGURE 8 Transducer Movement

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B) Surface Scan: Top Notch (See Figure 9) 1) Connect the 30° TEK-5568 Angle Beam Transducer (o r TEK-5565 if position on the on-aircraft Mount requires the smaller contact surface). Position at ~1 Skip from the bolt-hole as shown in Figure 9, aim towards bolt-hole (Surface distance from transducer exit point to top edge of hole should be ~ .439”), and maximize response. 2) Position front surface response on left side of scr een and ~ 1 Skip Bolt-hole response at mid screen. Adjust gain to set signal from bolt hole to 100% Full Screen Height. 3) Using the bolt-hole response as a reference, mani pulate the Transducer using a rotational and orbital motion (See Figure 8), to produce a response from t he Top Surface EDM Notch (See defects A and B in Figure 9). Maximize defect response. You should be able to separate this response from the Bolt-hole response so that it is easily discernible and signal amplitude from EDM Notch is minimum 50% Full Screen Height . Screen presentation should appear as shown in Figure 11B.

A

B D C

FIGURE 9 30° TEK-5568 ( TEK-5565 alternate )

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C) Edge Scan: Top & Bottom Notches (Ref. Figure 10) 1) Connect the 30° TEK-5565 Angle Beam Transducer. Position along edge of Reference Standard and aim towards Bolt-hole as shown in Figure 10. Maximize response. 2) Position Front Surface Response on left side of scr een & Bolt-hole response at mid screen & adjust to 100% Full Screen Height. 3) Manipulate the Transducer to aim slightly towards t he Top Surfaces using the Bolt-hole response as a reference to produce a response from the Top Surf ace EDM Notch & maximize. You should be able to separate this response from the Bolt-hole re sponse so that it is easily discernible and signal amplitude from EDM Notch is minimum 50% Full Screen Height

. 4) Manipulate the Transducer to aim slightly towards t he Bottom Surface using the Bolt-hole response as a reference to produce a response from the Bottom Surface EDM Notch & maximize. You should be able to separate this response from the Bolt-hole response so that it is easily discernible and signal amplitude from EDM Notch is minimum 50% Full Screen Height

.

14. Inspection Procedure *Note: Do not proceed with inspection if bolt-holes cannot be 100% inspected as specified per Section 6 of this technique. *Note: Figures 11, 12, and 13 provide typical side and plan view part configuration for clarity. Inspections shall be performed for opposite hand configurations as specified.
Complete all inspections as specif ied in Section 14A through 14D, and per Table 1: Inspection Check Sheet. FIGURE 10 30° TEK-5565 Calibration A

B D C

Transducer placed on edge of reference standard should not produce a response from the reference hole or Defect B

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A) Surface Scan: Bottom Surface Bolt-hole Cracks (Refer to Figure 11) 1) Following the same procedure used when scanning t he Reference Standard NDT001, position the 45° TEK-5566 Angle Beam Transducer at ~1⁄2 Skip from the Bolt-hole, aim towards Bolt-hole & maximize response. Based on a nominal part thickness of 0.380” the surface distance should be ~ 0.380” from transducer exit point to hole-bore & ~ 0.236” from transducer exit point to outer edge of washer. (See Figure 11) Note that part thickness varies from ~ 0.290” to 0. 360”, which will vary surface distances accordingly. *Note: use of Techna AMF-MR-8FX Flexible Exte nsions or equivalent may be required for access. 2) Position Front Surface Response on left side of screen and 1⁄2 Skip Bolt-hole response at mid screen. Adjust gain to set signal from bolt-hole to 100% Full Screen Height. Add 6db Scanning Gain. 3) Using the bolt-hole response as a reference, scan around the entire circumference of all Bolt-holes slowly and carefully using a rotational and orbita l motion as shown in Figure 8. Scanning shall be performed in both clockwise and counter-clockwise directions.

FIGURE 11 45° TEK-5566

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FIGURE 11A T yp ical Res p onse from Bolt Hole

FIGURE 11B Typical Response of Def ect Coming off Bolt Hole Defect

Bolt-h ole Bolt-h ole

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B) Surface Scan: Top Surface Bolt-hole Cracks (Refer to Figure 12) 1) Following the same procedure used when scanning Re ference Standard NDT001, position the 30° TEK5568 Angle Beam Transducer (or alternate TEK-5565 if used for calibration and position on the onaircraft Mount requires the smaller contact surface) at ~1 Skip from the Bolt-hole, aim towards Bolt-hole and maximize response. Based on a nominal part thickness of 0.380” the surface distance should be ~ 0.438” from transducer exit point to hole-bore & ~ 0.294” from transducer exit point to outer edge of washer. (See Figure 12) Note that part thickness varies from ~ 0.290” to 0. 360”, which will vary surface distances accordingly. *Note: use of Techna AMF-MR-8FX Flexible Exte nsions or equivalent may be required for access. 2) Position Front Surface Response on left side of scr een and 1 Skip Bolt-hole response at mid screen. Adjust gain to set signal from bolt-hole to 100% Full Screen Height. Add 6db Scanning Gain. 3) Using the bolt-hole response as a reference, scan around the entire circumference of all Bolt-holes slowly and carefully using a rotational and orbita l motion as shown in Figure 8. Scanning shall be performed in both clockwise and counter-clockwise directions.

FIGURE 12 30° TEK-5568 or TEK-5565 alternate

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C) Inbd Edge Scan: Top & Bottom Bolt-hole Cracks (Refer to Figure 13) 1) Following the same procedure used when scanning Reference Standard NDT001, position 30° TEK5568 Angle Beam Transducer (or alternate TEK-5565 if used for calibration, and position on the onaircraft Mount requires the smaller contact surfac e) along Inbd Edge of Mount, aim towards Bolt-hole and maximize response (See Figure 13). *Note: use of Techna AMF-MR-8FX Flexible Exte nsions or equivalent may be required for access. 2) Position Front Surface Response on left side of screen and Bolt-hole response at mid screen. Adjust gain to set signal from bolt-hole to 100% Full Screen Height. Add 6db Scanning Gain. 3) Start scanning at the outer most corner or Mount Edge. No bolt-hole response should be displayed in this position. Using the bolt-hole response as a re ference, scan along the entir e length of the Inbd Edge slowly and carefully with the Transducer aimed s lightly towards the Top Surface. Scanning shall performed with the transducer directed both Forward and Aft as shown in Figure 13. 4) Repeat Item C) 3 above but with the Transducer aimed slightly towards the Bottom Surface Scanning shall be performed with the transducer directed both Forward and Aft as shown in Figure 13.
D) Outbd Edge Scan: Top and Bottom Bolt-hole Cracks (Refer to Figure 13) 1) Repeat Section 14C Items 1 to 4 for inspection from Outbd Edge.

FIGURE 13 – Edge Scan 30° TEK-5566 Inbd Ed g e Outbd Ed g e

Inbd Ed g e Outbd Ed g e

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15. Acceptance Criteria A) All crack indications are Unacceptable.
16. Discontinuity Evaluation A) All responses similar to the applicable Refe rence Notch on Reference Standard NDT001 (i.e. defect signal able to be separated from the Bolt-hole re sponse) shall be regarded as a Crack indication regardless of amplitude. B) Crack indications shall be verified by performing Eddy Current Bolt-hole inspection after Fastener removal.
17. Part Disposition A) Parts meeting Section 15 Criteria shall be dispositioned as Acceptable. B) Parts not meeting Section 15 Criteria shall be dispositioned as Non-Conforming.

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T ABLE 

## 1 I NSPECTION 

## C HECK 

## S HEET


## Part ID:

Probe Location Clockwise Counter-Clockwise

Top Surface 30° (TEK-5565 or TEK-5568) 45° (TEK-5566) Probe Direction: Aft Probe Direction: Fwd Inbd Edge 30° (TEK-5565 or TEK-5568) Probe Direction: Aft Probe Direction: Fwd Outbd Edge 30° (TEK-5565 or TEK55-68)