NUMBER REVISION ENGINEERING 

 REPORT

#284 SNOW ENGINEERING CO. 

WICHITA FALLS, TEXAS

 ORDER X MODEL

TITLE BY CHK’D See Below

David Ligon LS SERIAL

DATE See Below

SERVICE LETTER #284 

PAGE OF

10/04/09 1 4

REFERENCES

(1) Snow Engineering Co. Process Specification #197 dated 06/04/02 

(2) Snow Engineering Co. Process Specification #204 Revision D dated 03/27/07 

(3) Snow Engineering Co. Service Letter #215 dated 12/13/05 

(4) Snow Engineering Co. Service Letter #240 dated 09/30/04 

(5) Snow Engineering Co. Service Letter #244 dated 04/25/05 

(6) Snow Engineering Co. Service Letter #245 dated 04/25/05 

(7) Snow Engineering Co. Service Letter #281 dated 08/01/09 

(8) Snow Engineering Co. Service Letter #80GG dated 12/21/05 

(9) Snow Engineering Co. Drawing 20975 - “Installation - Wing - 802” Sheet 2 Revision B dated 

03/14/07 

(10) Snow Engineering Co. Drawing 20975 - “Installation - Wing - 802” Sheet 4 Revision A dated 

01/07/09 

(11) Snow Engineering Co. Drawing 20995 - “Modification - Wing Center Splice - 802” Sheet 2 Revision 

D dated 11/25/05 

(12) Snow Engineering Co. Drawing 20995 - “Modification - Wing Center Splice - 802” Sheet 3 dated 

11/25/05 

(13) Snow Engineering Co. Report 1784 - “Test Results - Inboard AT-802 Main Spar” dated 06/21/07 

(14) Snow Engineering Co. Report 1859 - “Test Results - Inboard AT-802 Main Spar” dated 06/27/08 

(15) Snow Engineering Co. Report 2165 - “Inspection Interval Determination for the AT-802/AT-802A 

Aircraft S/Ns 0092 - 0269” dated 10/09/09 

SUBJECT

Wing inspection and lower spar cap replacement times 

MODELS AND SERIAL NUMBERS

AT-802/802A-0001 and subsequent without 80540 computerized firegate. 

SUMMARY

This service letter is to provide information on wing spar center splice inspections and spar cap 

replacement times. The inspection program and replacement times are summarized in the following 

section. Inspection access cover plates are installed per Service Letter #215 (Reference 3) with eddy 

current inspections performed per Process Specification #197 (Reference 1). Extended attach blocks 

(8-hole attach block installation per Drawing 20995 Sheet 2 (Reference 11) for serial number 802/802A0001 through -0091 and 9-hole attach block installation per Drawing 20995 Sheet 3 (Reference 12) for 

serial number 802/802A-0092 through -0178) may be installed when cracks found in the outboard holes 

can be removed by enlarging the hole to the next size. Spar cap replacements are per Service Letter 

#80GG (Reference 8) and Drawing 20975 Sheet 2 (Reference 10) with a subsequent life of 11,700 

hours. 
NUMBER REVISION ENGINEERING 

 REPORT

#284 SNOW ENGINEERING CO. 

WICHITA FALLS, TEXAS

 ORDER X MODEL

TITLE BY CHK’D See Below

David Ligon LS SERIAL

DATE See Below

SERVICE LETTER #284 

PAGE OF

10/04/09 2 4

ACTION

Serial numbers 802/802A-0001 through -0091:

By 1,700 hours time-in-service (TIS), eddy current inspect per Process Specification #197 (Reference 

1). See note 1 below if cracks are found. 

At 800 hour TIS intervals thereafter, eddy current inspect per Process Specification #197 (Reference 

1). If holes have been coldworked per Service Letter #244 (Reference 5), eddy current inspect at 1,600 

hour TIS intervals. See note 1 below if cracks are found. 

Between 3,200 hours TIS and 4,100 hours TIS, eddy current inspect per Process Specification #197 

(Reference 1) and install p/n 20997-2 center splice plate and p/n 20985-1 and 20985-2 extended 8-bolt 

splice blocks per 20995 Sheet 2 (Reference 11) and coldwork lower spar cap holes per Service Letter 

#240 (Reference 5). If the airplane was modified prior to 3,200 hours TIS, eddy current inspect upon 

the accumulation of 4,800 hours TIS after modification, and thereafter at 600 hour TIS intervals until 

reaching the extended safe life of 8,000 hours TIS. At 8,000 hours TIS, replace the wing main spar 

lower caps, the web plates, the center joint splice blocks and hardware, and the wing attach angles and 

hardware and install the steel web splice plate per Service Letter #80GG (Reference 8) and Drawing 

20975 Sheet 4 (Reference 10). Subsequent spar life is 11,700 hours. 

If an airplane has already been modified between 3,200 hours TIS and 4,100 hours TIS to install the 

p/n 20997-2 center splice plate and p/n 20985-1 and 20985-2 extended 8-bolt splice blocks without 

coldworking, eddy current inspect per Process Specification #197 (Reference 1) within 2,400 hours TIS 

after the modification and at intervals not to exceed 1,200 hours TIS thereafter. The coldworking per 

Service Letter #240 may be done at any time to terminate the eddy current inspection requirement. At 

8,000 hours TIS, replace the wing main spar lower caps, the web plates, the center joint splice blocks 

and hardware, and the wing attach angles and hardware and install the steel web splice plate per 

Service Letter #80GG (Reference 9) and Drawing 20975 Sheet 4 (Reference 10). Subsequent spar life 

is 11,700 hours. 

If an airplane has already been modified prior to 3,200 hours TIS to install the p/n 20997-2 center splice 

plate and p/n 20985-1 and 20985-2 extended 8-bolt splice blocks without coldworking and coldworking 

has not been performed subsequently, eddy current inspect per Process Specification #197 (Reference 

1) within 2,400 hours TIS after the modification and at intervals not to exceed 1,200 hours TIS 

thereafter. Eddy current inspect upon the accumulation of 4,800 hours TIS after modification, and 

thereafter at 600 hour TIS intervals until reaching the extended safe life of 8,000 hours TIS. At 8,000 

hours TIS, replace the wing main spar lower caps, the web plates, the center joint splice blocks and 

hardware, and the wing attach angles and hardware and install the steel web splice plate per Service 

Letter #80GG (Reference 8) and Drawing 20975 Sheet 4 (Reference 10). Subsequent spar life is 

11,700 hours. 

Note 1: Install the p/n 20997-2 center splice plate and p/n 20985-1 and 20985-2 extended 8-bolt splice 

blocks per 20995 Sheet 2 (Reference 11) and coldwork lower spar cap holes per Service Letter #240 

(Reference 4) if cracks found in the outboard holes can be removed by enlarging the hole to the next 
NUMBER REVISION ENGINEERING 

 REPORT

#284 SNOW ENGINEERING CO. 

WICHITA FALLS, TEXAS

 ORDER X MODEL

TITLE BY CHK’D See Below

David Ligon LS SERIAL

DATE See Below

SERVICE LETTER #284 

PAGE OF

10/04/09 3 4

size. If this repair installation is performed, eddy current inspect following the accumulation of 4,800 

hours after modification, and thereafter at 600 hour TIS intervals until reaching the extended safe life of 

8,000 hours TIS. At 8,000 hours TIS, replace the wing main spar lower caps, the web plates, the 

center joint splice blocks and hardware, and the wing attach angles and hardware and install the steel 

web splice plate per Service Letter #80GG (Reference 8) and Drawing 20975 Sheet 4 (Reference 10). 

Subsequent spar life is 11,700 hours. 

Serial numbers 802/802A-0092 through -0101:

By 1,700 hours time-in-service (TIS), eddy current inspect per Process Specification #197 (Reference 

1). See note 2 below if cracks are found. 

At 800 hour TIS intervals, eddy current inspect per Process Specification #197 (Reference 1). See 

note 2 below if cracks are found. 

By 4,100 hours TIS, install p/n 20994-2 center splice plate per 20975 Sheet 4 (Reference 10) and 

coldwork lower spar cap holes per Service Letter #245 (Reference 6). See note 2 below if cracks are 

found. 

At 2,000 hour TIS intervals thereafter, continue eddy current inspections per Process Specification 

#197 (Reference 1) until lower spar cap replacement at 8,000 hours. See note 1 below if cracks are 

found at any inspection. Otherwise, at 8,000 hours TIS, replace the wing main spar lower caps, the 

web plates, the center joint splice blocks and hardware, and the wing attach angles and hardware and 

install the steel web splice plate per Service Letter #80GG (Reference 8) and Drawing 20975 Sheet 4 

(Reference 10). Subsequent spar life is 11,700 hours. 

Note 2: The 9-hole attach block installation per Drawing 20995 Sheet 3 (Reference 12) which includes 

coldworking lower spar cap holes per Service Letter #281 (Reference 7) may be performed when 

cracks found in the outboard holes can be removed by enlarging the hole to the next size. If not 

already installed, install p/n 20994-2 center splice plate per 20975 Sheet 4 (Reference 10). If this repair 

installation is performed, no further inspections are required. At 8,000 hours TIS, replace the wing main 

spar lower caps, the web plates, the center joint splice blocks and hardware, and the wing attach 

angles and hardware and install the steel web splice plate per Service Letter #80GG (Reference 8) and 

Drawing 20975 Sheet 4 (Reference 10). Subsequent spar life is 11,700 hours. 

Serial numbers 802/802A-0102 through -0178:

Option 1: 

By 5,500 hours time-in-service (TIS), eddy current inspect per Process Specification #197 (Reference 

1) and coldwork lower spar cap holes per Service Letter #245 (Reference 6). At 2,200 hour TIS 

intervals thereafter, eddy current inspect per Process Specification #197 (Reference 1). See note 3 

below if cracks are found. At 8,000 hours TIS, replace the wing main spar lower caps, the web plates, 

the center joint splice blocks and hardware, and the wing attach angles and hardware and install the 
NUMBER REVISION ENGINEERING 

 REPORT

#284 SNOW ENGINEERING CO. 

WICHITA FALLS, TEXAS

 ORDER X MODEL

TITLE BY CHK’D See Below

David Ligon LS SERIAL

DATE See Below

SERVICE LETTER #284 

PAGE OF

10/04/09 4 4

steel web splice plate per Service Letter #80GG (Reference 8) and Drawing 20975 Sheet 4 (Reference 

10). Subsequent spar life is 11,700 hours. 

Option 2: 

By 5,500 hours TIS, eddy current inspect per Process Specification #197 (Reference 1). See note 3 

below if cracks are found. 

At 1,100 hour TIS intervals thereafter, eddy current inspect per Process Specification #197 (Reference 

1). See note 3 below if cracks are found. 

At 8,000 hours TIS, replace the wing main spar lower caps, the web plates, the center joint splice 

blocks and hardware, and the wing attach angles and hardware and install the steel web splice plate 

per Service Letter #80GG (Reference 8) and Drawing 20975 Sheet 4 (Reference 10). Subsequent spar 

life is 11,700 hours. 

Note 3: The 9-hole attach block installation per Drawing 20995 Sheet 3 (Reference 12) which includes 

coldworking lower spar cap holes per Service Letter #281 (Reference 7) may be performed when 

cracks found in the outboard holes can be removed by enlarging the hole to the next size. If this repair 

installation is performed, no further inspections are required. At 8,000 hours TIS, replace the wing main 

spar lower caps, the web plates, the center joint splice blocks and hardware, and the wing attach 

angles and hardware and install the steel web splice plate per Service Letter #80GG (Reference 8) and 

Drawing 20975 Sheet 4 (Reference 10). Subsequent spar life is 11,700 hours. 

Serial numbers 802/802A-0179 through -0269:

No inspection requirements. At 8,000 hours time-in-service (TIS), replace the wing main spar lower 

caps, the web plates, the center joint splice blocks and hardware, and the wing attach angles and 

hardware and install the steel web splice plate per Service Letter #80GG (Reference 8) and Drawing 

20975 Sheet 4 (Reference 10). Subsequent spar life is 11,700 hours. 

Serial numbers 802/802A -0270 and subsequent:

No inspection requirements. At 11,700 hours time-in-service (TIS), replace the wing main spar lower 

caps, the web plates, the center joint splice blocks and hardware, and the wing attach angles and 

hardware and install the steel web splice plate per Service Letter #80GG (Reference 8) and Drawing 

20975 Sheet 4 (Reference 10). Subsequent spar life is 11,700 hours.