NUMBER ENGINEERING 

 REPORT #281

SNOW ENGINEERING CO. 

WICHITA FALLS, TEXAS

 ORDER X MODEL

TITLE BY CHK’D See Below

David Ligon LS SERIAL 

DATE 

SERVICE LETTER #281 

PAGE OF 

08/01/09 1 12

SUBJECT:

Split Sleeve Cold Expansion of Lower Spar Cap Holes - Rework of In-service 

Aircraft in the 9-hole Configuration 

MODELS:

AT-802, AT-802A S/N 802-0092 through 802-0269 

REFERENCE:

(1) – Fatigue Technology Inc. Process Specification 8101D 

(2) - Snow Engineering Co. Drawing 20995, sheet 3 

GENERAL:

This Service Letter provides a set of detailed instructions for cold 

working the 2 outboard-most wing center splice block holes in the lower 

spar cap. This document addresses airplanes in the 8 hole block 

configuration. 

For clarification, the splice block bolt holes are numbered from inboard to 

outboard. The inboard-most hole is defined as the “#1 Hole” and the 

outboard-most hole is defined as the “#9 Hole”. See Figure 1 below. The 

terms “#9 Hole” and “#8 Hole” will be used throughout this document to 

identify holes being cold worked. 

Figure 1 - 9 Hole Block Numbering Scheme 

CAUTION:

A MIS-DRILLED OR MIS-REAMED HOLE WILL RUIN THE SPAR CAP. THERE IS NO 

FIX FOR AN OVERSIZED OR EGG-SHAPED HOLE. OVERSIZED OR EGG-SHAPED 

HOLES WILL REQUIRE SPAR CAP REPLACEMENT. REPLACING A DAMAGED SPAR 

CAP CAN LEAD TO SIGNIFICANT COST AND SIGNIFICANT AIRCRAFT DOWNTIME. 

EXERCISE EXTREME CAUTION AND GOOD AVIATION MAINTENANCE PRACTICES 

AND TECHNIQUE WHEN PERFORMING THE STEPS IN THIS SERVICE LETTER.
NUMBER ENGINEERING 

 REPORT #281

SNOW ENGINEERING CO. 

WICHITA FALLS, TEXAS

 ORDER X MODEL

TITLE BY CHK’D See Below

David Ligon LS SERIAL 

DATE 

SERVICE LETTER #281 

PAGE OF 

08/01/09 2 12

EQUIPMENT:

The tools required to accomplish this rework are separated into 3 different 

tool kits and are color coded for ease of identification. The “Yellow” 

Tool Kit A is used when cold working the “#9 Holes”. The “Blue” Tool Kit B 

is used when cold working the “#8 Holes”. The “Red” Tool Kit C contains 

all other general tools used for this process. The instructions in this 

document specify that each hole size be worked separately. This is not 

only to eliminate opportunities for tool selection errors, but also to hold 

the spar cap stackup in place during the cold working process. While 

working from the “Yellow” tool kit, the “Blue” tool kit should be closed, 

latched, and out of reach. While working from the “Blue” tool kit, the 

“Yellow” tool kit should be closed, latched, and out of reach. 

P/N DESCRIPTION 

CASR-60-1 Starting Reamer 

CAG-60 Combination Gage 

CAMG-60 Mandrel Gage 

CAS-60-36F Flared Sleeve (2 ea.) 

CAM-60-2-60-V2 Mandrel 

MEN-26B-1223F Nosecap Assembly 

CAR-60-1-.3750 Gage Finish Reamer 

Table 1 – Cold Work Tool Kit List – 3/8 Finished Holes (STDN = 60) 

P/N DESCRIPTION 

CASD-80-1-C Starting Drill (Ref .453 Dia) 

CASR-80-1 Starting Reamer (Ref .470 Dia.) 

CAG-80 Combination Gage 

CAMG-80 Mandrel Gage 

CAS-80-40F Flared Sleeve (2 ea.) 

CAM-80-2-60-V2 Mandrel 

MEN-26B-1601F Nosecap Assembly 

CAR-80-1-.5000 Gage Finish Reamer 

Table 2 – Tool Kit B “Blue Tool Kit” – 1/2 Finished Holes (STDN = 80) 

P/N DESCRIPTION 

MB-30 Medium Brute Puller Unit 

FT-20 Power Pak 

PS200-1 120 microinch surface finish comparator plate 

SK398-1 Cold Work Tooling Fixture (See SK398-1 for 

complete list of parts) 

Table 3 – Tool Kit C “Red Tool Kit” – General Tools 
NUMBER ENGINEERING 

 REPORT #281

SNOW ENGINEERING CO. 

WICHITA FALLS, TEXAS

 ORDER X MODEL

TITLE BY CHK’D See Below

David Ligon LS SERIAL 

DATE 

SERVICE LETTER #281 

PAGE OF 

08/01/09 3 12

PERSONNEL QUALIFICATION:

In order to perform the steps in this Service Letter, personnel must: 

a.) possess the tooling specified in the “Equipment” section of this 

document. 

b.) be trained and certified for eddy current inspection. 

c.) attend an Air Tractor sponsored training course and receive a 

certificate of completion for the Split Sleeve Cold Expansion 

process. This requirement may also be fulfilled by attending a 

Fatigue Technology Inc. training session and receiving a Certificate 

of Training after the completion of that training. 

PROCEDURE:

SECTION A - CLEAN AND GAIN ACCESS TO REPAIR AREA 

B. 1. Before accomplishing this Service Letter, thoroughly clean the 

airplane, especially the hopper, gatebox, and wing splice area. 

B. 2. Gain access to the repair area as follows: 

B. 2.1. Remove hopper dump push rod mechanism 

B. 2.2. Remove spray pump to spray valve tube 

B. 2.3. Remove bottom load fill tube 

B. 2.4. Remove spray pump supply tube 

B. 2.5. Remove gatebox fairing 

B. 2.6. Remove gatebox 

B. 2.7. Remove fiberglass enclosure skin 

SECTION B - REMOVE HARDWARE, INSPECT #7 AND #8 HOLES

B. 1. Shore aircraft wings as follows: 

B. 1.1. Place wing jacks at wing tie-down ring locations. 

B. 1.2. Simultaneously raise both jacks until jack pads “just 

contact” the tie-down ring on both left and right wings. 

B. 1.3. Simultaneously raise both jacks an additional 11/16 + 1/16 

to unload the bolts in the lower cap splice connection and 

facilitate bolt removal. 

B. 2. Identify the spar lower cap “#8 and #9 hole” bolt locations. See 

Figure 1. 

B. 3. Remove nuts from the two 3/8 bolts, both left and right side, in the 

lower wing spar splice using good aviation maintenance practice. 

Use 1/4” aluminum pin punch to CAREFULLY tap bolts up and out of 

lower spar cap and splice blocks. 

NOTE: USE EXTREME CAUTION NOT TO SCRATCH INSIDE OF HOLES WITH PUNCH.

B. 4. Remove nuts from the two 7/16 bolts, both left and right side, in 

the lower wing spar splice using good aviation maintenance practice. 
NUMBER ENGINEERING 

 REPORT #281

SNOW ENGINEERING CO. 

WICHITA FALLS, TEXAS

 ORDER X MODEL

TITLE BY CHK’D See Below

David Ligon LS SERIAL 

DATE 

SERVICE LETTER #281 

PAGE OF 

08/01/09 4 12

Use 1/4” aluminum pin punch to CAREFULLY tap bolts up and out of 

lower spar cap and splice blocks. 

NOTE: USE EXTREME CAUTION NOT TO SCRATCH INSIDE OF HOLES WITH PUNCH. 

B. 5. Clean #8 and #9 holes using solvent and a soft bristle brush or rag. 

Use compressed air to remove all solvent residue from the holes. 

B. 6. Eddy Current inspect “#8 and #9 Holes” per Air Tractor PS 197. 

SECTION C – COLD WORK #8 AND #9 HOLES

C. 1. Install and locate SK398-1 attach block Tooling Fixture (See SK398): 

C. 1.1. Remove the two #3 5/8” dia. bolts from the center splice. 

Install the tooling fixture with two 5/8” dia. studs, nuts, 

and washers as shown on SK398. Tighten the stud nuts. 

C. 1.2. Install drill press onto the drill press mounting plate. 

Do not tighten 2 mounting bolts. 

C. 1.3. Lock Tapered Alignment Pin into drill chuck. 

C. 1.4. Position drill press so alignment pin slips into hole. 

C. 1.5. With Tapered Pin still in hole, tighten 2 mounting bolts. 

C. 1.6. Withdraw drill chuck from hole and remove alignment pin. 

C. 1.7. Drill fixture is now aligned with hole. 

COLD WORK “#9 HOLE” TO 3/8 (STANDARD TOOL DIAMETER NUMBER, STDN = 60) 

Note: Accomplish the following Cold Work steps concurrently for both 

the left hand and right hand “#8 Holes”.

C. 2. Acquire “3/8 Cold Work Kit A and inventory for proper tools using 

Table 1. 

C. 3. Ream the “#9 Hole” using the CASR-60-1 starting reamer. Sulfur based 

cutting oil should be used for starting hole ream and all subsequent 

ream steps. After reaming, move SK398-1 Tooling Fixture out of the 

way and clean the hole with solvent and dry with compressed air. 

See Figure 2. 

IMPORTANT!

IF BOTH #8 HOLES AND BOTH #9 HOLES PASS THE EDDY CURRENT INSPECTION 

IN PS 197, PROCEED WITH THE STEPS IN THIS SERVICE LETTER. IF ANY HOLES 

FAIL THE EDDY CURRENT INSPECTION IN PS 197, DISCONTINUE THIS SERVICE 

LETTER.
NUMBER ENGINEERING 

 REPORT #281

SNOW ENGINEERING CO. 

WICHITA FALLS, TEXAS

 ORDER X MODEL

TITLE BY CHK’D See Below

David Ligon LS SERIAL 

DATE 

SERVICE LETTER #281 

PAGE OF 

08/01/09 5 12

C. 4. The starting hole diameter must be .348-.351. Check the starting 

hole using the CAG-60 Go-No Go Combination Gage, or a ball gage and 

micrometer. When using the Go-No Go Combination Gage, a gage that 

can only be inserted to the first machined “step” identifies a 

properly reamed hole. The starting hole should be checked for 

ovality by inserting the gage a second time, rotated 90. See Figure 

3. 

C. 5. Select the CAM-60-2-60-V2 mandrel and inspect using the CAMG-60 GoNo Go gage or a micrometer. The mandrel major diameter shall be 

.3428 - .3438. The mandrel shall be checked at the beginning of 

each aircraft job because the mandrel diameter is critical for 

proper cold expansion of the hole. An excessively worn mandrel will 

pass through the CAMG-60 Go-No Go gage and shall be replaced. If 

the mandrel fails the diameter check, contact Air Tractor Customer 

Service Department for a replacement mandrel. See Figure 4. 

C. 6. Clean the hole using solvent and a soft bristle brush or rag. Use 

compressed air to remove all solvent residue from the holes. 

Mandrel Check Fixture

Mandrel Check

Accept Reject and Discard Mandrel

Figure 4

Accept Reject

Figure 3

Starting Drill

Starting Reamer

Figure 2 
NUMBER ENGINEERING 

 REPORT #281

SNOW ENGINEERING CO. 

WICHITA FALLS, TEXAS

 ORDER X MODEL

TITLE BY CHK’D See Below

David Ligon LS SERIAL 

DATE 

SERVICE LETTER #281 

PAGE OF 

08/01/09 6 12

C. 7. Cold expand the hole. See Figure 5: 

C. 7.1. Select the CAS-62-30F split sleeve and slide it over the 

mandrel. Orient sleeve so that the split is pointing along 

the spar cap centerline facing inboard and the flared end 

is toward the Puller nosecap. 

C. 7.2. Insert the mandrel and sleeve into the starting hole. 

Ensure sleeve orientation is correct per step 13.1 above. 

The sleeve should protrude from the topside of the hole 

1/32” or more. 

C. 7.3. Place nosecap firmly against and perpendicular to the lower 

surface of the splice block. 

C. 7.4. Activate Puller. Continue holding the trigger until 

mandrel is through the entire lower spar cap stackup. 

Release trigger when the mandrel is clear of the structure. 

C. 7.5. Remove sleeve from the cold worked hole and discard. 

Sleeves are used only once.

C. 8. Check the cold expanded hole diameter using the CAG-60 Go-No Go 

Combination gage. The gage will fit into a properly expanded hole. 

The cold worked hole should measure .3530 as a minimum before the 

finish ream process. If the Go-No Go Combination gage will not fit 

Figure 5 

SPLIT FACES 

INBOARD 
NUMBER ENGINEERING 

 REPORT #281

SNOW ENGINEERING CO. 

WICHITA FALLS, TEXAS

 ORDER X MODEL

TITLE BY CHK’D See Below

David Ligon LS SERIAL 

DATE 

SERVICE LETTER #281 

PAGE OF 

08/01/09 7 12

 into the hole, check for proper tool selection, check mandrel for 

proper diameter, then follow step 13 a second time. Note that a 

surface upset is created during the cold working process at each hole 

face. This surface upset is normal. See Figure 6. 

C. 9. Follow the Tooling Fixture alignment procedure previously described. 

C. 10. Finish ream the cold worked hole using the CAR-60-1-.3750 gage 

finish reamer. Finish reamed final hole must have a surface 

roughness of 120 microinches or smoother measured with surface 

finish comparator plates. See Figure 7. 

C. 11. Inspect finished hole. Finish reamed final hole must have a 

diameter of .3750 +.002 / -.000 and must have a surface roughness of 

Gage Finish Reamer

Go-No-Go Gage

Combination Gage

or

or Hole has been

cold expanded.

Hole has not been

cold expanded.

Gage Finish Reamer

Figure 6

Finish Reamer

Figure 7 
NUMBER ENGINEERING 

 REPORT #281

SNOW ENGINEERING CO. 

WICHITA FALLS, TEXAS

 ORDER X MODEL

TITLE BY CHK’D See Below

David Ligon LS SERIAL 

DATE 

SERVICE LETTER #281 

PAGE OF 

08/01/09 8 12

120 microinches or smoother measured with surface finish comparator 

plates. Holes may be inspected using a ball gauge and micrometer, 

or air gauge with the proper calibrated hole standards. 

C. 12. Install new hardware in accordance with Drawing 20995, sheet 3. 

SECTION 3 - REMOVE HARDWARE, INSPECT, COLD WORK “#8 HOLE” TO 1/2 HOLE 

(STANDARD TOOL DIAMETER NUMBER, STDN = 80)

C. 13. Acquire “Blue” Tool Kit B and inventory for proper tools using Table 

2. 

C. 14. Identify the spar lower cap “#8 Hole” bolt locations. See Figure 1. 

C. 15. Remove clamp bolts at #7 hole locations. 

C. 16. Clean holes using solvent and a soft bristle brush or rag. Use 

compressed air to remove all solvent residue from the holes. 

C. 17. Follow the Tooling Fixture alignment procedure previously described. 

C. 18. Drill the entire stackup of upper and lower blocks and lower cap at 

the “#8 Hole” location using CASD-80-1-C starting drill. Sulfur 

based cutting oil should be used for starting hole drill and all 

subsequent ream steps. 

C. 19. Ream the “#8 Hole” using the CASR-80-1 starting reamer. After 

reaming, move SK398-1 Tooling Fixture out of the way and clean the 

hole with solvent and dry with compressed air. See Figure 8. 

C. 20. The starting hole diameter must be .470 - .473. Check the starting 

hole using the CAG-80 Go-No Go Combination Gage, or a ball gage and 

micrometer. When using the Go-No Go Combination Gage, a gage that 

can only be inserted to the first machined “step” identifies a 

properly reamed hole. The starting hole should be checked for 

ovality by inserting the gage a second time, rotated 90. See Figure 

9. 

Starting Drill

Starting Reamer Figure 8 
NUMBER ENGINEERING 

 REPORT #281

SNOW ENGINEERING CO. 

WICHITA FALLS, TEXAS

 ORDER X MODEL

TITLE BY CHK’D See Below

David Ligon LS SERIAL 

DATE 

SERVICE LETTER #281 

PAGE OF 

08/01/09 9 12

C. 21. Select the CAM-80-2-60-V2 mandrel and inspect using the CAMG-80 GoNo Go gage or a micrometer. The mandrel major diameter shall be 

.4643-4653. The mandrel shall be checked at the beginning of each 

aircraft job because the mandrel diameter is critical for proper 

cold expansion of the hole. An excessively worn mandrel will pass 

through the CAMG-80 Go-No Go gage and shall be replaced. If the 

mandrel fails the diameter check, contact Air Tractor Customer 

Service Department for a replacement mandrel. See Figure 10. 

C. 22. Clean the hole using solvent and a soft bristle brush or rag. Use 

compressed air to remove all solvent residue from the holes. 

C. 23. Cold expand the hole. See Figure 11: 

C. 23.1. Select the CAS-80-36F split sleeve and slide it over the 

mandrel. Orient sleeve so that the split is pointing along 

Accept Reject

Figure 9 

Mandrel Check Fixture

Mandrel Check

Accept Reject and Discard Mandrel

Figure 10 
NUMBER ENGINEERING 

 REPORT #281

SNOW ENGINEERING CO. 

WICHITA FALLS, TEXAS

 ORDER X MODEL

TITLE BY CHK’D See Below

David Ligon LS SERIAL 

DATE 

SERVICE LETTER #281 

PAGE OF 

08/01/09 10 12

the spar cap centerline facing inboard and the end is 

toward the Puller nosecap. 

C. 23.2. Insert the mandrel and sleeve into the starting hole. 

Ensure sleeve orientation per step 29.1 above. The sleeve 

should protrude from the topside of the hole 1/32” or more. 

C. 23.3. Place nosecap firmly against and perpendicular to the lower 

surface of the splice block. 

C. 23.4. Activate Puller. Continue holding the trigger until 

mandrel is through the entire lower spar cap stackup. 

Release trigger when mandrel is clear of the structure. 

C. 23.5. Remove sleeve from the cold worked hole and discard. 

Sleeves are used only once.

C. 24. Check the cold expanded hole diameter using the CAG-80 Go-No Go 

Combination gage. The gage will fit into a properly expanded hole. 

The cold worked hole should measure .4780 as a minimum before the 

finish ream process. If the Go-No Go Combination gage will not fit 

into the hole, check for proper tool selection, check mandrel for 

proper diameter, then follow step 30 a second time. Note that a 

Figure 11

SPLIT FACES INBOARD 
NUMBER ENGINEERING 

 REPORT #281

SNOW ENGINEERING CO. 

WICHITA FALLS, TEXAS

 ORDER X MODEL

TITLE BY CHK’D See Below

David Ligon LS SERIAL 

DATE 

SERVICE LETTER #281 

PAGE OF 

08/01/09 11 12

surface upset is created during the cold working process at each 

hole face. This surface upset is normal. See Figure 12. 

C. 25. Follow the Tooling Fixture alignment procedure previously described. 

C. 26. Finish ream cold worked hole using CAR-80-1-.5000 gage finish 

reamer. Finish reamed final hole must have a surface roughness of 

120 microinches or smoother measured with surface finish comparator 

plates. See Figure 13. 

C. 27. Inspect finished hole. Finish reamed final hole must have a 

diameter of .4995 +.002 / -.000 and must have a surface roughness of 

120 microinches or smoother measured with surface finish comparator 

Gage Finish Reamer

Go-No-Go Gage

Combination Gage

or

or Hole has been

cold expanded.

Hole has not been

cold expanded.

Gage Finish Reamer

Figure 12

Finish Reamer

Figure 13 
NUMBER ENGINEERING 

 REPORT #281

SNOW ENGINEERING CO. 

WICHITA FALLS, TEXAS

 ORDER X MODEL

TITLE BY CHK’D See Below

David Ligon LS SERIAL 

DATE 

SERVICE LETTER #281 

PAGE OF 

08/01/09 12 12

plates. Holes may be inspected using a ball gauge and micrometer, 

or air gauge with the proper calibrated hole standards. 

C. 28. Install new hardware in accordance with Drawing 20995, sheet 1. 

SECTION 4 - REASSEMBLE AIRPLANE AND RETURN TO SERVICE

C. 29. Reinstall gatebox and all equipment removed in accordance with 

Airplane Owners Manual. 

C. 30. Make the following maintenance log entry in aircraft logbook: 

“This aircraft, Air Tractor (model number)-(s/n), has been reworked 

in accordance with Snow Engineering Co. Service Letter #281 and is 

approved for return to service, this date (date), signed 

(signature), (certificate and number).