P.O. BOX 3689 BRISTOL, TENNESSEE 37625-3689 USA 

TELEPHONE: 423-538-5151 TOLL FREE: 800-251-7094 

TELEFAX: 423-538-8469 E-MAIL: sales@aero-access.com 

techsupport@aero-access.com

ALERT SERVICE BULLETIN 

ASB No. AA-07109 

No Revision 

SUBJECT: High Landing Gear Aft Crosstubes

P/N 412-321-104 / 412-321-304 

MODELS AFFECTED: Bell Helicopter Textron model 412, 412EP and 412CF and 

Agusta S.p.A. model AB412, AB412EP helicopters with 

Aeronautical Accessories, Inc. P/N 412-321-104 / 

412-321-304 High Aft Crosstubes installed in accordance 

with STC SR01052AT. 

COMPLIANCE: Part A: Within the next 50 flight hours, but not later than 

June 30, 2008, establish a high aft crosstube takeoff/landing 

life limit of 20,000 on P/N 412-321-304. 

 High aft crosstubes for which flight hours are unknown, or 

the number of takeoff/landings cannot be determined, must 

be replaced within the next 450 takeoff/landings. 

 High aft crosstubes with historical information establishing a 

number of takeoffs/landings greater than 20,000 must be 

replaced within the next 450 takeoff/landings. 

Part B: Prior to 2500 takeoff/landings. 

 High aft crosstubes with historical information establishing a 

number of takeoffs/landings greater than 2500 must accomplish 

Part B within 50 flight hours or 250 takeoff/landings, whichever 

comes first, of the receipt of this bulletin. 

Part C: Within 450 takeoff/landings after accomplishment of 

Part B, and every 450 takeoff/landings thereafter. 

IF OWNERSHIP OF AIRCRAFT HAS CHANGED, PLEASE FORWARD THIS BULLETIN TO NEW OWNER 
412, 412EP, 412CF ALERT SERVICE BULLETIN ASB No. AA-07109 

AB412, AB412EP HIGH AFT CROSSTUBE No Revision 

Part D: Prior to 2500 takeoff/landings and every 12 months or 

2500 takeoff/landings, whichever comes first, thereafter. 

 High aft crosstubes with historical information establishing a 

number of takeoffs/landings greater than 2500 must 

accomplish Part D within 1 month of the receipt of this bulletin. 

Part E: Prior to 7500 takeoff/landings and every 5000 

takeoff/landings thereafter. 

High aft crosstubes with historical information establishing a 

number of takeoffs/landings greater than 7500 must 

accomplish Part E within 3 months of the receipt of this 

bulletin. 

 Part F: Within the next 25 flight hours, but not later than May 

15, 2008. 

DESCRIPTION: Aeronautical Accessories, Inc. has conducted a review of 

the high aft crosstube in response to three reported field 

failures. Our analysis indicates a takeoff/landing life must 

be assigned to P/N 412-321-304 high aft crosstube and 

additional scheduled inspections must be conducted on 

both P/N 412-321-104 and 412-321-304 high aft crosstubes. 

Part A of this bulletin establishes a 20000 takeoff/landing 

life on P/N 412-321-304 high aft crosstube. P/N 

412-321-104 high aft crosstube is already subject to the 

retirement life. This bulletin provides the information 

necessary to calculate the number of takeoffs/landings. If 

the total number of takeoff/landings is less than the 

recommended life, record all takeoff/landings until 

component life is achieved or component is otherwise 

removed from service. 

Part B of this bulletin provides instructions to clean and 

inspect two areas on the bottom of the high aft crosstube. 

Means to protect this area with primer and a clear coat are 

also included. P/N 412-321-104, serial number AA-1274 

and subsequent, crosstubes are manufactured with the two 

inspection areas primed and clear-coated. 

Part C of this bulletin provides instructions to conduct a 

recurring visual inspection of the two primed and clear 

coated areas of the high aft crosstube after the 

accomplishment of Part B. 
412, 412EP, 412CF ALERT SERVICE BULLETIN ASB No. AA-07109 

AB412, AB412EP HIGH AFT CROSSTUBE No Revision 

Part D of this bulletin provides instructions to conduct a 

recurring dimensional inspection of the skid gear to identify 

permanent deformation of the crosstube. 

Part E of this bulletin provides instructions to conduct a 

recurring fluorescent penetrant inspection of the high aft 

crosstube. 

Part F of this bulletin provides clarification on helicopter 

towing instructions to prevent crosstube damage or failure 

as a result of ground handling or towing. 

APPROVAL: The engineering aspects of this bulletin are FAA/DER 

approved. 

MANPOWER: PART A: Approximately 0.5 hours. 

PART B: Approximately 3.0 hours. 

 PART C: Approximately 0.5 hours 

PART D: Approximately 1.0 hours. 

PART E: Approximately 24.0 hours. 

Manhours are based on hands-on time and may vary with 

personnel or facilities available. 
412, 412EP, 412CF ALERT SERVICE BULLETIN ASB No. AA-07109 

AB412, AB412EP HIGH AFT CROSSTUBE No Revision 

AERONAUTICAL ACCESSORIES, INC. 

April 3, 2008 Page 4 of 15 

MATERIAL: 

The following Customer supplied materials are required to comply with this 

bulletin: 

TABLE 1 – PARTS LIST 

CUSTOMER SUPPLIED CONSUMABLE MATERIALS 

Qty Description

AR MIL-R-81294, Type I or II Chemical Paint Remover 

AR MIL-PRF-85582 Primer (PRC-DeSoto EWDE 072A/B) 

AR MIL-PRF-85285, Type I Gloss Clear Coat Paint (Deft 03X085) 

AR MIL-PRF-87937 Cleaning Compound, Aerospace Equipment 

 

NOTE

The MIL-PRF-85582 primer (PRC-DeSoto EWDE 072A/B)

[packaged as a 1-gallon, 1-qt (Parts A&B) kit (P/N 

EWDE072)] and the MIL-PRF-85285, Type I clear coat paint 

(Deft 03X085) [packaged as a 3-qt kit (P/N MIL-PRF-85285)] 

may be procured from a Bell Helicopter Supply Center. The 

primer and paint may also be procured [packaged in 1-qt, 

primer and paint, kits (P/N 1272K)] from Aerospace 

Products, Inc., 6413 Midway Road, Halton City, TX 76117 

(817-332-1669). 

SPECIAL TOOLS REQUIRED: 10X magnifying glass 

WEIGHT AND BALANCE: Not affected 

PUBLICATIONS AFFECTED: 

Installation Instructions, report number AA-95005 

Instructions for Continued Airworthiness, report number AA-01136 

ADDITIONAL INFORMATION: 

Any questions regarding this bulletin should be addressed to: 

AERONAUTICAL ACCESSORIES, INC. 

P.O. Box 3689 

Bristol, 37625-3689 TN 

PRODUCT SUPPORT 

1-800-251-7094 

techsupport@aero-access.com
412, 412EP, 412CF ALERT SERVICE BULLETIN ASB No. AA-07109 

AB412, AB412EP HIGH AFT CROSSTUBE No Revision 

AERONAUTICAL ACCESSORIES, INC. 

April 3, 2008 Page 5 of 15 

ACCOMPLISHMENT INSTRUCTIONS 

Upon receipt of this bulletin, determine by part number if affected high aft crosstube is 

installed. If affected crosstube is installed, perform the actions contained in this bulletin. 

Any crosstube failing inspection shall be removed from service and replaced with an 

airworthy crosstube. 

PART A INSPECTION REQUIREMENTS AND HISTORICAL RECORDS 

1. Verify all high aft crosstubes, P/N 412-321-104 and 412-321-304, comply with 

the inspection criteria of the Instructions for Continued Airworthiness report 

number AA-01136 and BHT-412-MM-2 (Bell Helicopter model 412 Maintenance 

Manual). 

A retirement life has been established for the following high skid gear aft 

crosstubes. A Historical Record is provided (Figure 4) for recording of 

takeoff/landing operations for the listed life-limited crosstubes. 

PART NUMBER (1) COMPONENT LIFE LIMIT 

(EVENTS) (2)

412-321-104 Aft Crosstube, High Skid Gear 20,000 

Takeoff/Landings

412-321-304 Aft Crosstube, High Skid Gear 20, 000 

Takeoff/Landings

NOTES: 

(1) The airworthiness limitation for part number listed applies to all successive dash numbers 

for that component unless otherwise specified. 

(2) Either landings or takeoff may be counted. 

These Airworthiness Limitations are FAA approved and specify maintenance 

required under §§ 43.16 and 91.403 of the Federal Aviation Regulations unless 

an alternative program has been FAA approved. 

2. Create a Historical Record form to track P/N 412-321-304 high aft crosstube 

takeoff/landing life per the compliance section of this bulletin. Those operators 

that have recorded the number of takeoff/landings are subject to the 20,000 

takeoff/landing limit. 

NOTE

Helicopters with takeoff/landings that are higher than the 

average of 10 per hour must substitute the higher value in all 

estimated calculations. 

3. If the actual takeoff/landing information is not available it is permissible to 

estimate the number. To determine the number of takeoff/landings on the 

crosstube, multiply the airframe hours by a factor of ten. 

4. Place the calculated takeoff/landing information on the Historical Record form 

and track the applicable life as per the compliance section of the bulletin. 

5. Replace life limited crosstubes per the Instructions for Continued Airworthiness, 

report number AA-01136. 
412, 412EP, 412CF ALERT SERVICE BULLETIN ASB No. AA-07109 

AB412, AB412EP HIGH AFT CROSSTUBE No Revision 

AERONAUTICAL ACCESSORIES, INC. 

April 3, 2008 Page 6 of 15 

NOTE

Aeronautical Accessories Inc. has discontinued sale of P/N 

412-321-304 high aft crosstube Assembly. P/N 412-321-104 

high aft crosstube is completely interchangeable with P/N 

412-321-304. 

PART B INITIAL INSPECTION REQUIREMENT FOR P/N 412-321-104 AND 

P/N 412-321-304 CROSSTUBES 

NOTE

Crosstube visual inspection is conducted with aircraft at rest 

on skid landing gear; minimum gross weight at inspection is 

9,000 pounds. 

CAUTION

Chemical removers shall be used only in areas of 

adequate ventilation. Suitable goggles or face masks, 

chemical resistant gloves, boots and clothing shall be 

worn to avoid contact of chemical removers with eyes, 

skin and clothing. Chemical removers shall further be 

handled in accordance with applicable OSHA 

regulations, state and local safety codes, and company 

established safety standards and policies. 

NOTE

P/N 412-321-104 Crosstubes with serial number AA-1274 

and subsequent are manufactured with the two inspection 

areas primed and clear-coated. Steps 1 through 3 of Part B 

may be skipped unless opaque paint has been applied to 

either inspection area described below and in Figure 1. 

1. Prepare crosstube inspection areas by chemically removing crosstube paint and 

primer from an area 2.0 ±0.25 inches wide extending between BL 18 and BL 30 

at the center-bottom surface of the crosstube on both the left and the right sides 

of the crosstube (see Figure 1). 

2. Apply MIL-R-81294, Type I or II chemical paint remover with a brush and allow it 

to set from 15 to 45 minutes to soften paint. 

3. Using a stiff fiber brush and clean water, rinse paint from crosstube. If required, 

use abrasive pad (Scotch-Brite, Type A) and MIL-R-81294, Type I or II chemical 

paint remover to aid in lifting paint. Brush crosstube with abrasive pad in the 

longitudinal direction, using care so as not to abrade crosstube metal surface. 

4. Rinse part clean with clean water and dry thoroughly. Reapplication of chemical 

paint remover may be required to ensure that paint and primer is completely 

removed so that the metal surface of the cross tube is clearly visible. 

5. Using at least 10X magnification and a strong light source, visually inspect the 

stripped areas for indications of cracking. If cracking is suspected, fluorescent 

penetrant inspect crosstube per ASTM E1417, Type I, Method B, C, or D, Level 2 

in accordance with Bell Helicopter Standard Practices Manual (BHT-ALL-SPM). 
412, 412EP, 412CF ALERT SERVICE BULLETIN ASB No. AA-07109 

AB412, AB412EP HIGH AFT CROSSTUBE No Revision 

AERONAUTICAL ACCESSORIES, INC. 

April 3, 2008 Page 7 of 15 

WARNING

IF CRACKING IS DISCOVERED, THE CROSSTUBE IS NO 

LONGER AIRWORTHY AND MUST BE IMMEDIATELY 

REPLACED. REPLACE CROSSTUBE PER APPLICABLE 

INSTRUCTIONS IN INSTRUCTIONS FOR CONTINUED 

AIRWORTHINESS, REPORT NUMBER AA-01136. 

6. Following crosstube inspection, coat the stripped crosstube area with 

MIL-PRF-85582 primer (.0006 – .0009 thick) by spraying in accordance with 

manufacturer’s instructions. Allow primer to cure per manufacturer instructions. 

NOTE

The MIL-PRF-85582 primer (PRC-DeSoto EWDE 072A/B)

[packaged as a 1-gallon, 1-qt (Parts A&B) kit (P/N 

EWDE072)] and the MIL-PRF-85285, Type I clear coat paint 

(Deft 03X085) [packaged as a 3-qt kit (P/N MIL-PRF-85285)] 

may be procured from a Bell Helicopter Supply Center. The 

primer and paint may also be procured [packaged in 1-qt, 

primer and paint, kits (P/N 1272K)] from Aerospace 

Products, Inc., 6413 Midway Road, Halton City, TX 76117 

(817-332-1669). 

7. Following primer cure, paint the area with polyurethane clear coat paint per 

MIL-PRF-85285 by spraying in accordance with manufacturer’s instructions. 

Allow paint to cure per manufacturer instructions. 

8. Annotate aircraft records that Part B of this bulletin has been accomplished. 

9. Return aircraft to service. 

PART C SCHEDULED VISUAL INSPECTION REQUIREMENTS FOR 

P/N 412-321-104 AND P/N 412-321-304 

NOTE

The following crosstube inspection is to be incorporated into 

the inspection intervals/methods identified in Instructions for 

Continued Airworthiness, report number AA-01136. 

NOTE

Crosstube visual inspection is conducted with aircraft at rest 

on skid landing gear; minimum gross weight at inspection is 

9,000 pounds. 

1. Use MIL-PRF-87937 cleaning compound prepared in accordance with the 

manufacturer’s recommendations to clean all residue and dirt from the cross tube 

surfaces shown in Figure 1. 

2. Using at least 10X magnification and a strong light source, visually inspect the 

clear coated areas for indications of cracking. 
412, 412EP, 412CF ALERT SERVICE BULLETIN ASB No. AA-07109 

AB412, AB412EP HIGH AFT CROSSTUBE No Revision 

AERONAUTICAL ACCESSORIES, INC. 

April 3, 2008 Page 8 of 15 

3. If cracking is suspected, remove clear coat and primer per steps 2 thru 4 of Part

B, and fluorescent penetrant inspect crosstube per ASTM E1417, Type I, Method 

B, C, or D, Class 2, in accordance with Bell Helicopter Standard Practices 

Manual (BHT-ALL-SPM). If cracking is not confirmed, reapply clear coat and 

primer per steps 6 and 7 of Part B. If cracking is confirmed, remove crosstube 

from service. 

WARNING

IF CRACKING IS DISCOVERED, THE CROSSTUBE IS NO 

LONGER AIRWORTHY AND MUST BE IMMEDIATELY 

REPLACED. REPLACE CROSSTUBE PER APPLICABLE 

INSTRUCTIONS IN INSTRUCTIONS FOR CONTINUED 

AIRWORTHINESS, REPORT NUMBER AA-01136 

4. Annotate aircraft records to indicate that Part C of this bulletin has been 

accomplished; and return aircraft to service. 

PART D SCHEDULED LANDING GEAR DEFLECTION INSPECTION 

REQUIREMENTS FOR P/N 412-321-104 AND P/N 412-321-304 

NOTE

The following crosstube inspection is to be incorporated into 

the inspection intervals/methods identified in Instructions for 

Continued Airworthiness, report number AA-01136. 

1. Hoist or jack the helicopter until no weight is on the skid gear. 

2. Measure the lateral distance between the two forward Crosstube cap 

assemblies. Measure the lateral distance between the two aft Crosstube cap 

assemblies. Divide these dimensions by two to determine the helicopter 

centerline, BL 0.00. 

3. Measure the Crosstube horizontal deflection from the centerline of the helicopter, 

BL 0.00, to the outside of the skid tubes. 

4. The Crosstube horizontal deflection as measured in step 3 above must be within 

the limits as shown in Figure 2. Crosstubes that measure outside of the limits 

must be replaced. 

5. Inspect landing gear assembly in accordance with Instructions for Continued 

Airworthiness report number AA-01136 and BHT-412-MM damage limits. 

6. Repair or replace components that are damaged in excess of repairable limits. 

7. Annotate aircraft records to indicate that Part D of this bulletin has been 

accomplished; and return aircraft to service. 
412, 412EP, 412CF ALERT SERVICE BULLETIN ASB No. AA-07109 

AB412, AB412EP HIGH AFT CROSSTUBE No Revision 

AERONAUTICAL ACCESSORIES, INC. 

April 3, 2008 Page 9 of 15 

PART E COMPONENT OVERHAUL REQUIREMENTS FOR P/N 412-321-104 

AND P/N 412-321-304 

The Component Overhaul Schedule, Table 2, summarizes the overhaul interval for 

high aft crosstube components. 

NOTE

Neither the assignment of a time period overhaul of a 

component nor failure to assign a time period for overhaul of 

a component constitutes a warranty of any kind. The only 

warranty applicable to the component is that warranty 

included in the Purchase Agreement for the component. 

Time between overhauls and inspection periods is based upon experience, testing, 

and engineering judgment and is subject to change at the sole discretion of 

Aeronautical Accessories Inc. or an appropriate government agency. 

WARNING

ALL PARTS REMOVED, DUE TO REACHING THEIR 

LIMITS OR AS A RESULT OF AN ACCIDENT/INCIDENT 

AND DEEMED UNAIRWORTHY, SHALL BE 

PERMANENTLY MARKED AS SCRAP OR PHYSICALLY 

DESTROYED TO THE EXTENT THAT THERE IS NO 

CHANCE OF REPAIR OR INSTALLATION ON ANY 

HELICOPTER OR COMPONENT. 

TABLE 2 – COMPONENT OVERHAUL SCHEDULE 

PART NUMBER NOMENCLATURE OVERHAUL INTERVAL 

412-321-104 Aft Crosstube, High 

Skid Gear 

Prior to 7500 Takeoff/Landings and 

every 5000 Takeoff/Landings thereafter 

412-321-304 Aft Crosstube, High 

Skid Gear 

Prior to 7500 Takeoff/Landings and 

every 5000 Takeoff/Landings thereafter 

 

E.1 Disassembly Instructions 

1. Remove Aft Crosstube Assembly in accordance with Instructions for Continued 

Airworthiness report number AA-01136. 

2. Remove Aft Crosstube Beam Assembly in accordance with Instructions for 

Continued Airworthiness report number AA-01136. 

NOTE

The Upper Center Support on the Aft Crosstube is bonded 

with structural adhesive and is not designed for removal. 

3. Remove both Aft Crosstube Clamp Assemblies in accordance with Instructions 

for Continued Airworthiness report number AA-01136. 
412, 412EP, 412CF ALERT SERVICE BULLETIN ASB No. AA-07109 

AB412, AB412EP HIGH AFT CROSSTUBE No Revision 

AERONAUTICAL ACCESSORIES, INC. 

April 3, 2008 Page 10 of 15 

E.2 Cleaning and Preparation 

1. Remove aged sealant by scraping with a sharp piece of plastic. Finish by lightly 

sanding with 400 grit abrasive cloth or paper in the longitudinal direction of the 

crosstube. 

WARNING

DO NOT SAND CROSSTUBE IN A CIRCUMFERENTIAL 

DIRECTION. 

2. Prepare crosstube by chemically removing crosstube paint and primer outboard 

of the Upper Center Support to top of saddles. See Figure 3. 

CAUTION 

Protect Upper Center Support area to prevent 

contamination by paint strippers and penetrant 

inspection chemicals. 

a. Apply MIL-R-81294, Type I or II chemical paint remover with a brush and 

allow it to set from 15 to 45 minutes to soften paint. 

b. Using a stiff fiber brush and clean water, rinse paint from crosstube. If 

required, use abrasive pad (Scotch-Brite, Type A) and MIL-R-81294, Type I 

or II chemical paint remover to aid in lifting paint. Brush crosstube with 

abrasive pad in the longitudinal direction, using care so as not to abrade 

crosstube metal surface. 

c. Rinse part clean with clean water and dry thoroughly. Reapplication of 

chemical paint remover may be required to ensure that paint and primer is 

completely removed so that the (bare) metal surface of the cross tube is 

clearly visible. 

3. When parts are not to be processed immediately after cleaning, apply corrosion 

preventive oil, to all parts to protect against corrosion. Wrap parts in barrier 

material and secure with tape. 

E.3 Inspection 

1. Inspect crosstube outboard of Upper Center Support area using fluorescent 

penetrant method per ASTM E1417, Type I, Method B, C, or D, Level 2, in 

accordance with Bell Helicopter Standard Practices Manual (BHT-ALL-SPM). 

Refer to BHT-ALL-SPM for fluorescent penetrant inspection procedures.

2. Damage limits are specified in Instructions for Continued Airworthiness, report 

number AA-01136 and BHT-412-MM-2 (Bell Helicopter model 412 Maintenance 

Manual). 

E.4 Repair 

1. Repair damage within repairable limits in accordance with Instructions for 

Continued Airworthiness report number AA-01136. 
412, 412EP, 412CF ALERT SERVICE BULLETIN ASB No. AA-07109 

AB412, AB412EP HIGH AFT CROSSTUBE No Revision 

AERONAUTICAL ACCESSORIES, INC. 

April 3, 2008 Page 11 of 15 

2. Refinish crosstube by applying MIL-PRF-85582 primer and MIL-PRF-85285 paint 

(or equivalent) per manufacturer instructions to the stripped areas. The areas to 

be inspected per Part B should be masked to omit MIL-PRF-85285 paint as 

shown in Figure 1. Paint inspection areas with MIL-PRF-85285 Type I Gloss 

Clear coat as described in Part B of this bulletin. 

E.5 Assembly Instructions 

1. Assemble both Aft Crosstube Clamp Assemblies in accordance with Instructions 

for Continued Airworthiness report number AA-01136. 

2. Assemble Aft Crosstube Beam Assembly in accordance with Instructions for 

Continued Airworthiness report number AA-01136. 

3. Install Aft Crosstube Assembly to aircraft in accordance with Instructions for 

Continued Airworthiness report number AA-01136. 

4. Annotate aircraft records to indicate that Part E of this bulletin has been 

accomplished; and return aircraft to service. 

PART F TOWING AIRCRAFT 

Helicopter towing operations must be conducted in accordance with BHT-412-MM-2 

(Bell Helicopter model 412 Maintenance Manual) and 412-OSN-07-32 (Landing 

Gear Maintenance and Handling). Manufacturer towing requirements are applicable 

to any aircraft being towed with weight on gear. This includes towing aircraft with 

ground handling wheels installed and aircraft resting on moveable platforms. 

CAUTION

Failure to follow manufacturer towing instructions may 

result in crosstube damage and/or failure. 
412, 412EP, 412CF ALERT SERVICE BULLETIN ASB No. AA-07109 

AB412, AB412EP HIGH AFT CROSSTUBE No Revision 

AERONAUTICAL ACCESSORIES, INC. 

April 3, 2008 Page 12 of 15 

FIGURE 1 – CLEAR COAT AND INSPECTION AREA 
412, 412EP, 412CF ALERT SERVICE BULLETIN ASB No. AA-07109 

AB412, AB412EP HIGH AFT CROSSTUBE No Revision 

AERONAUTICAL ACCESSORIES, INC. 

April 3, 2008 Page 13 of 15 

 

“A” “B” Part Number Model Effectivity in. mm in. mm 

412-321-104 / 412-321-304 412 Aft Crosstube (High) 57.00 1448 59.00 1499 

FIGURE 2 – HIGH LANDING GEAR DEFLECTION LIMITS 
412, 412EP, 412CF ALERT SERVICE BULLETIN ASB No. AA-07109 

AB412, AB412EP HIGH AFT CROSSTUBE No Revision 

AERONAUTICAL ACCESSORIES, INC. 

April 3, 2008 Page 14 of 15 

FIGURE 3 – PAINT REMOVAL AREA 
412, 412EP, 412CF ALERT SERVICE BULLETIN ASB No. AA-07109 

AB412, AB412EP HIGH AFT CROSSTUBE No Revision 

AERONAUTICAL ACCESSORIES, INC. 

April 3, 2008 Page 15 of 15 

FIGURE 4 – HISTORICAL SERVICE RECORD