SERVICE BULLETIN TRANSMITTAL SHEET

Service Bulletin No.: V3/0002 Date of Original Issue: 22-September-2010

Revision No.: Revision C Date of Issue: 30-April-2014

DHC-3 COMPLETE WING BOX INSPECTION – BORESCOPE AND VISUAL

Viking has received SDRs related to cracking of the DHC-3 wing upper skin corrugations as well as 

cracks in the main spar lower cap. The intent of this Service Bulletin is to detect and repair these 

cracks and to obtain as much information as possible from operators to evaluate the overall condition 

of the fleet to assess if further action is required.

NOTE 1: NO RETROACTIVE THRESHOLD INSPECTION IS REQUIRED IF THRESHOLD 

INSPECTION FROM SB V3/0002 REVISION A OR B HAS BEEN COMPLETED –

CONTINUE WITH REPEAT INSPECTIONS IN ACCORDANCE WITH SB V3/0002 

REVISION C AT APPROPRIATE REPEAT INSPECTION SCHEDULE.

NOTE 2: ALL OTHER AIRCRAFT MUST INCORPORATE APPLICABLE INSPECTIONS IN 

ACCORDANCE WITH SB V3/0002 REVISION C.

NOTE 3: This revision supersedes the previous revision of this Service Bulletin.

NOTE 4: Revision bars in the left margin of this Service Bulletin denote changes from the 

previous revision.

This page transmits Revision ‘C’ of Service Bulletin V3/0002, pages 1 thru 12, dated 30 April 2014.

Service Bulletin re-issued to include incorporation of MOD 3/1005 (MOD for inspection access holes)

and detailed compliance and accomplishment instructions for the inspection of the entire wing box 

assembly.

Remove Service Bulletin V3/0002 Revision ‘B’ dated 03 July 2013 and replace with attached.

Previous issues of Service Bulletin V3/0002:

Initial Issue – (22-Sep-2010) - effectivity – All DHC-3 aircraft

Revision A – (22-Feb-2013) - effectivity – All DHC-3 aircraft

Revision B – (03-Jul-2013) - effectivity - All DHC-3 aircraft

Page 1 of 2 ATA Ref: 57-00

30-April-2014 Service Bulletin V3/0002
THIS PAGE INTENTIONALLY LEFT BLANK

Page 2 of 2 ATA Ref: 57-00

30-April-2014 Service Bulletin V3/0002
1959 De Havilland Way 

Sidney, B.C. Canada 

V8L 5V5 

Tel: (250) 656 - 7227 

SERVICE BULLETIN 

ATA SYSTEM: 5700 NUMBER: V3/0002

SUBJECT: DHC-3 Complete Wing Box Inspection – Borescope and Visual

I. PLANNING INFORMATION

A. Effectivity

The complete wing box inspection requirement laid out herein, has an effectivity of

ALL DHC-3 aircraft.

NOTES: To perform this inspection, improved access is required. Refer to Section 

II.A. of this Service Bulletin for details.

Before you do this Service Bulletin, read ALL Sections of the bulletin 

and examine all Supplemental Type Certificate (STC) or equivalent 

action changes to make sure this Service Bulletin can be completed.

FOR AIRCRAFT EQUIPED WITH STCs or EQUIVALENT CHANGES, 

THE OPERATOR MUST CONTACT THE STC HOLDER TO EVALUATE 

CONFLICT POSSIBILITIES.

B. Reason 

Viking has received Service Difficulty Reports (SDR’s) related to cracking of the 

DHC-3 wing upper skin corrugations as well as cracks in the main spar lower cap. 

The intent of this Service Bulletin is to detect and repair these cracks and to obtain as 

much information as possible from operators to evaluate the overall condition of the 

fleet and assess if further action is required. All wings require internal inspections in 

order to maintain long term structural integrity.

The purpose of incorporating additional inspection openings is to provide sufficient 

access to complete a thorough inspection of the DHC-3 wing.

C. Description

Inspections are required to identify possible cracking, corrosion or any other damage 

of the wing box assembly.

To accommodate these inspections, access panels are incorporated in the wing lower 

skin in accordance with MOD 3/1005 (MOD Kit DWG C3MK1005; MOD Kit 

C3MK1005-1).

DHC-3

OTTER

30-April-2014 S.B. V3/0002

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SERVICE BULLETIN V3/0002

The purpose of this Service Bulletin is to: 

1. Borescope inspect and visually inspect the wing box for cracks and corrosion.

2. As soon as possible following the first inspection accomplished in accordance 

with Revision C of the Service Bulletin, complete the Operator Reply Form 

included with this Service Bulletin even if no cracks or damage is found.

3. Repair damage prior to next flight.

D. Compliance 

The compliance time for actions associated with this Service Bulletin is listed in 

Table 1 below.

NOTE 1: To accomplish inspection (action) from Table 1 below, incorporate lower 

wing skin access openings as defined in Section II.A. of this Service 

Bulletin.

NOTE 2: If actual flight hours of wing are not known, contact Technical Support at 

Viking Air Limited (see Sec. I.J for contact information) to assist in the 

determination.

NOTE 3: If SB V3/0002 Rev A or B has been complied with prior to the issue date of 

SB V3/0002 Rev C, continue with the repeat inspections, in accordance 

with Table 1 below, from the last completed inspection in accordance with

SB V3/0002 Rev A or B.

NOTE 4: Damage shall be repaired prior to next flight in accordance with accepted 

data (such as PSM1-3-3) or other approved data.

TABLE 1 – WING BOX INSPECTION - COMPLIANCE DETAILS

Action Action Detail Effectivity Threshold 

Inspection

Repeat 

Inspection

Complete wing box 

inspection

Do a borescope

and visual 

inspection on ALL 

areas of the Wing 

Box in 

accordance with 

(Sec. II).

a. <31,200

wing flight hours 

Within 800 wing flight hours or 

within 6 months of issue date of 

this SB (whichever occurs first)

Also see note 3 Every 1600 

wing flight 

hours or 2100 

flight cycles 

(whichever 

occurs first)

b.

31,200≤

wing flight hours 

<31,600

Before accumulating 32,000 

wing flight hours or within 6 

months of issue date of this SB 

(whichever occurs first)

c. ≥ 31,600

wing flight hours

Within 400 wing flight hours or 3 

months of the issue date of this 

SB (whichever occurs first)

E. Approval

The technical content of this Service Bulletin has been approved under the authority 

of Transport Canada Civil Aviation (TCCA) Design Approval Organization (DAO) 04-

V-02.

30-April-2014 S.B. V3/0002

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SERVICE BULLETIN V3/0002

F. Manpower

An estimated 36 man-hours per wing will be required to complete this Service 

Bulletin (16 man hours to install access panels and 20 hours to inspect the wing 

components).

All costs to complete the inspection of the wing components are the responsibility of 

the Operator.

G. Weight and Balance

FOR MOD 3/1005 (Current) FOR MOD 3/1002 (Original)

AIRCRAFT STATION WEIGHT AIRCRAFT STATION WEIGHT

STA 139.25 +1.58 lbs STA 134.15 +1.58 lbs

STA 159.63 +0.60 lbs STA 159.63 +0.60 lbs

H. Electrical Load Data 

Not affected. 

I. Publications Affected 

None.

J. References 

This Service Bulletin contains a Survey to be completed and returned to Viking. The 

following drawings have been provided with this Service Bulletin to illustrate the 

technical activities: C3MK1005, C3Z1001, and C3Z1002. For more information 

please contact:

Viking Air Limited Technical Support

1959 De Havilland Way

Sidney, British Columbia

V8L 5V5

technical.support@vikingair.com

FAX: 250-656-0673

Telephone Numbers:

Regional: 250-656-7227

North America: 1-800-663-8444

International: 1-800-6727-6727

30-April-2014 S.B. V3/0002

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SERVICE BULLETIN V3/0002

II. ACCOMPLISHMENT INSTRUCTIONS

A. INTRODUCTION OF NEW ACCESS HOLES IN THE LOWER WING SKIN

1. To perform this inspection, Viking is providing MOD 3/1005 (MOD KIT DWG 

C3MK1005) for the incorporation of access holes which is only suitable for 

incorporation on OEM wings used on OEM aircraft.

NOTE 1: (a) If MOD 3/1002 (MOD Kit DWG C3MK1002) has been incorporated in 

accordance with SB V3/0002 Revision A or B, the incorporation of MOD 

3/1005 (MOD Kit DWG C3MK1005) is not required in order to accomplish 

the inspection requirements of this Service Bulletin.

(b) If the inspection opening at wing station 53.75 has been incorporated 

in accordance with SB V3/0002 Revision NC, no change is required at this 

location, but the remaining inspection openings specified in MOD 3/1005 

(MOD Kit DWG C3MK1005) are required unless MOD 3/1002 (MOD Kit 

DWG C3MK1002) was also incorporated.

NOTE 2: MOD 3/1005 (MOD Kit DWG C3MK1005) is compatible for wings fitted 

with STC SA94-114 (or US STC SA00287NY) STOL Kit.

NOTE 3: For aircraft fitted with Viking STC SA03-50, refer to Service Bulletin

SB 3-STC(03-50)-001 for applicable access instructions.

NOTE 4: For Wings / Aircraft equipped with STCs or equivalent changes, 

other than mentioned in Section II.A.1. above, the operator must 

contact the STC holder to evaluate conflict possibilities.

2. Add applicable new access holes in accordance with MOD Kit C3MK1005-1 on both 

Left Hand (LH) Wing and Right Hand (RH) Wing.

3. Parts can be fabricated by qualified individuals or purchased from Viking Product 

Support.

B. COMPLETE WING BOX INSPECTION

The Left Hand (LH) Wing:

1. Remove all inspection access panels / plugs between wing root and wing tip, 

including those for the access holes incorporated in Section II.A. above, and 

remove wing tip in accordance with PSM1-3-2 Section 2.15.1.

2. Using a flexible borescope, inspect for cracks, corrosion, missing/smoking/working

/broken fasteners or other damage on the entire internal structure of wing between 

wing root and wing tip, upper/lower skins, ribs (webs, upper/lower flanges), fore 

and aft surfaces of nose spar, main spar and rear spar (including caps and webs). 

Pay particular attention to the following areas for cracks in fastener holes and 

open holes:

(a.) Skin splice;

(b.) Spar Web splice;

(c.) Spar cap splice;

30-April-2014 S.B. V3/0002

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SERVICE BULLETIN V3/0002

(d.) Hinge attachments on rib and rear spar;

(e.) Fastener holes on skin (especially those common to the inboard/outboardend-row of fastener holes on the reinforcement doublers);

(f.) Access cutouts and lightening holes on spar/rib webs;

(g.) Rib attachment to the webs and caps of the nose spar, main spar, and rear 

spar, looking for cracks in flanges, bending radii and at fastener heads;

(h.) Corrugations at rib attachments (both forward and aft of the main spar). See 

Figure 1A and 1B for typical corrugation cracks;

(i.) All fastener holes on the lower spar caps (main and rear spar), lower stringers 

and lower skins between wing root and wing tip. Note that fatigue prone 

areas may be located between Sta 135 and 185. See Figure 1C for example 

of cracks on main spar lower cap.

3. Carry out a detailed inspection of the exterior surface of the wing for cracks, 

corrosion, missing/smoking/working/broken fasteners or other damage. Pay 

particular attention to skin splice, and access cutouts.

4. Do a visual inspection around doubler area of inspection holes at every repeat 

inspection.

5. Document all findings and cracks (noting length, direction, wing station position, 

smoking fasteners, oversized or broken fasteners, etc.); include pictures identifying 

the location (use station number) and orientation of all findings.

6. Complete the attached Post Inspection Survey Report Form (even if no damage 

was found) and forward to Technical Support as soon as possible (see Sec. I.J for 

contact information).

7. Repair damage prior to next flight.

NOTE: Repairs shall be in accordance with accepted data such as PSM1-3-3 or 

other approved data.

8. Re-install inspection panels and wing tip in accordance with PSM1-3-2 Section 

2.15.2.

The Right Hand (RH) Wing:

9. Repeat Step II.B.1 to Step II.B.8 on the RH wing.

D. RECORDING

1. Make an entry in the aircraft flight log book upon completion of access hole 

incorporation associated with MOD 3/1005: “INCORPORATION OF MOD 3/1005 

ACCESS HOLES COMPLETED IN ACCORDANCE WITH SECTION II.A OF SB 

V3/0002 Revision C AT XX,XXX WING FLIGHT HOURS FOR WING S/N XXX.”

2. Complete Operator Reply Form attached following the first inspection incorporated 

30-April-2014 S.B. V3/0002

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SERVICE BULLETIN V3/0002

in accordance with Revision C of Service Bulletin V3/0002, and send it to Viking 

Air Limited Technical Support.

3. Make an entry in the aircraft flight log book upon completion of Section II.B of this 

Service Bulletin: “INSPECTIONS COMPLETED IN ACCORDANCE WITH 

SECTION II.B OF SB V3/0002 Revision C AT XX,XXX FLIGHT HOURS FOR WING 

S/N XXX; INSPECTIONS RESULTS SENT TO VIKING AIR LIMITED.”

III. MATERIAL INFORMATION AND TOOLING 

A. Material 

• Modification Kit C3MK1005-1 (includes MOD Kit DWG C3MK1005 and DWGs 

C3Z1001 & C3Z1002)

B. Tooling – Price and Availability 

(a) Flexible Borescope Kit with light

(b) Flashlight and mirror

(c) Wing Support Stand

(d) Standard AME hand tools

30-April-2014 S.B. V3/0002

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SERVICE BULLETIN V3/0002

IV. FIGURES AND TABLES

FIGURE 1A – TYPICAL CORRUGATION CRACKS

 

FIGURE 1B – CORRUGATION CRACKS ON ONE OF THE WING SDR

Typical Corrugation Cracks

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SERVICE BULLETIN V3/0002

FIGURE 1C – CRACKS ON MAIN SPAR LOWER CAP FROM ONE OF THE WING INSPECTION SDR

30-April-2014 S.B. V3/0002

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SERVICE BULLETIN V3/0002

Service Bulletin V3/0002 – Operator Reply Form (Left Hand Wing)

Operator Name: 

Contact Person: 

Contact Phone/Email: 

A/C Serial Number: 

Wing S/N: Total Time on Wing (in hrs): 

Inspection Findings (use Figure 2 diagram below to indicate location of findings):

Additional Comments:

Please return form via email to technical.support@vikingair.com or via fax to 250-656-0673

30-April-2014 S.B. V3/0002

Revision ‘C’ Page 9 of 12
SERVICE BULLETIN V3/0002

4 3 2 1 37.15

8 7 6 5 47.5

11 10 9 60

14 13 12 72.5

17 16 15 85

20 19 18 97.5

23 22 21 110

26 25 24 122.5

29 28 27 135

32 31 30 147.5

35 34 33 160

38 37 36 172.5

41 40 39 185

44 43 42 197.5

47 46 45 210

50 49 48 222.5

53 52 51 235

56 55 54 247.5

59 58 57 260

62 61 60 272.5

65 64 63 285

68 67 66 297.5

71 70 69 310

74 73 72 322.5

FIGURE 2 – FINDING LOCATION DIAGRAM 335

Rear Spar Main Spar Front Spar Sta. No.

NOTE:

NOT TO 

SCALE 

–

FOR REFERENCE 

PURPOSES 

ONLY

LEFT HAND WING – LOOKING UP AT TOP SKIN

Document all findings and crack locations on this page

Noting length, WS position, rivet locations, loose, oversized or blind fasteners, etc.

30-April-2014 S.B. V3/0002

Revision ‘C’ Page 10 of 12
SERVICE BULLETIN V3/0002

Service Bulletin V3/0002 – Operator Reply Form (Right Hand Wing)

Operator Name: 

Contact Person: 

Contact Phone/Email: 

A/C Serial Number: 

Wing S/N: Total Time on Wing (in hrs): 

Inspection Findings (use Figure 3 diagram below to indicate location of findings):

Additional Comments:

Please return form via email to technical.support@vikingair.com or via fax to 250-656-0673

30-April-2014 S.B. V3/0002

Revision ‘C’ Page 11 of 12
SERVICE BULLETIN V3/0002

1 2 3 4 37.15

5 6 7 8 47.5

9 10 11 60

12 12 14 72.5

15 16 17 85

18 19 20 97.5

21 22 23 110

24 25 26 122.5

27 28 29 135

30 31 32 147.5

33 34 35 160

36 37 38 172.5

39 40 41 185

42 43 44 197.5

45 46 47 210

48 49 50 222.5

51 52 53 235

54 55 56 247.5

57 58 59 260

60 61 62 272.5

63 64 65 285

66 67 68 297.5

69 70 71 310

72 73 74 322.5

FIGURE 3 – FINDING LOCATION DIAGRAM

Front Spar Main Spar Rear Spar Sta. No.

335

RIGHT HAND WING – LOOKING UP AT TOP SKIN

Document all findings and crack locations on this page

Noting length, WS position, rivet locations, loose, oversized or blind fasteners, etc. 30-April-2014 S.B. V3/0002

Revision ‘C’ Page 12 of 12