## RC::U:3ENSUN HELICOPTER COMPANY 2901 Airport Drive, Torrance, California 90505 Phone (310) 539-0508 Fax (310) 539-5198 Page 1of3 R44 SERVICE BULLETIN SB-72
DATE: 30April2010 TO: R44 and R44 IIowners, operators, and maintenance personnel SUBJECT: Main Rotor Blade Bond Inspection ROTORCRAFTAFFECTED: R44 helicopterswith C016-2 main rotor blades, and R44ll

helicopters with C016-5 main rotor blades. TIME OF COMPLIANCE: At next 100-hour inspection, annual inspection, or by 31 July

2010, whichever occurs first, and at each 100-hourand annual inspection thereafter. BACKGROUND: Debonding of rotor blade skins can occur when the bond line is

exposed due to erosion ofthe blade finish, or when corrosion occurs on the internal aluminum tip cap. Proper inspection and protection (refinishing) of bonded areas is required. Debonding resulting from improper inspection and maintenance could cause a catastrophic accident. COMPLIANCE PROCEDURE: NOTE To facilitate inspection, blade may be teetered down, collectivefully raised, and cyclic stick positioned to apply maximum up pitch. 1. Refer to Figures 1 and 2. Remove both main rotor blade tip covers and clean the blades. 2. Using 1 Ox magnification, visually inspect uncovered skin-to-tip cap bond joints. Using a 1965-or-later United States quarter-dollarcoin, tap test skin-to-tip cap bond joints on both upperand lowersurfaces. Ifcorrosion, separation, orvoids are detected, blade is unairworthy. Tap testtutorial video is available at: www.robinsonheli.com/support.htm. 3. Using 1 Ox magnification, visually inspect any exposed skin-to-spar bond line forgaps (empty space between skin and spar). Blade is unairworthy ifany gap, including "pin hole(s)", is detected in the bond line. 4. Refer to Figure 2. Mark outboard 135 inches of blade lower surface as shown to identify skin-to-spar bond joint area. (OVER)R44 SB-72 Page 2 of3 5. Verify no visible dents within the bond joint area. Blade is unairworthy if bond joint area is dented. 6. Taptestthe lowerskin-to-sparbondjointand verify novoidsexist. Blade is unairworthy ifavoid is detected. 7. Refinish all exposed bare metal per R44 SL-32B. 8. Install bladetip covers, ensuring cover edges are flush with blade profile. 9. Make appropriate maintenance record entries. Approximate Cost: Parts: $5 for Kl-200 Kit ifordered by 31 July 2010. Kl-200 Kit includes: 1ea MT332-44tool 1ea SAN30001 Sharpie® marker Labor: Less than 1 man-hour. GAP in bond line requires blade replacement (example). PIN HOLE in bond line requires 1 __**-..:::.::::.::~** replacement (example).
SKIN-TO-SPAR BOND LINE, located 1.15 inch from leading edge of blade (requires inspection and evaluation if exposed, see text) REMOVABLE TIP COVER

SKIN-TO-TIP CAP CRITICAL BOND JOINT

1.37 inches for P/N C016-2 & C016-5 FIGURE 1 TIPAREAAND LOWER SURFACE (Example, Bladewith Excessive Paint Erosion) EXPOSED PAINT PRIMER (example)

YELLOW PAINTHold MT332-44 (R44-series) tool against main rotor blade surface and leading edge while moving it spanwise.

Lines

Insert felt tip of Sharpie® (brand) 30000-series "FINE POINT PERMANENT MARKER" thru holes in tool and mark two spanwise lines along lower surface from tip inboard 135 inches. R44 SB-72 Page 3 of3

FIGURE 2 MARKING LOWER SKIN-TO-SPAR BOND JOINTAREA

THE DESIGN ENGINEERINGASPECTS OF THIS BULLETIN HAVE BEEN SHOWN TO COMPLY WITH APPLICABLE FEDERALAVIATION REGULATIONSANDARE FAAAPPROVED.