By David Collogan
The epoxy tape application process developed by Airwolf Aerospace LLC to help prevent de-bonding of the stainless steel rotor blades on Robinson Helicopter R22 and R44 models has been purchased by some 300 Robinson operators, officials say, and that number is likely to increase in the wake of an FAA AD early this year and a series of safety recommendations by the National Transportation Safety Board this month (BA, June 16/272).
The stainless steel blades on both models of Robinson helicopters have a stated service life of 2,200 hours time in service. But following its investigation of a number of rotor blade delamination accidents, NTSB said FAA should require non destructive testing of all Robinson rotor blades "at intervals appropriately less than 596 hours time in service...to evaluate the bond joints between the skin and spar at the tip of the main rotor blade..."
Airwolf began working on developing a fix for the Robinson blade delamination problem a couple of years ago. John Kochy, director of engineering for Airwolf, said he and other company officials sought help from 3M, which had developed an epoxy tape erosion barrier for use on military helicopters operating in the Mideast. During Operation Desert Storm, Kochy said the military was being forced to replace blades on its large transport helicopters every 20 hours because of sand damage. After some experimentation, 3M developed a tape for those helicopter blades that extended the life to approximately 200 hours.
"3M was very, very nice to us" when Airwolf officials approached the company for help in addressing the Robinson blade problem, Kochy told BA in a telephone interview last week. There was considerable effort to find a material that had the properties to protect the blade, but which was light enough not to affect the performance of the helicopter. Kochy is a fixed- and rotary-wing pilot and Airwolf has R22 Serial No. 12, which it has operated for years. Kochy did much of the flight testing that led FAA to issue Airwolf a Supplemental Type Certificate late last year. Installation of the STC fix is approved as an Alternate Method of Compliance for the AD the agency issued Jan. 18, 2008.
Technically, FAA regulations permit an operator to apply the specialized tape that 3M custom manufactures for Airwolf, Kochy said. But he strongly recommends that Robinson owners who buy the blade tape kit employ the services of a licensed Airframe & Powerplant mechanic to perform the installation. "A lot of people underestimate how complicated it is," he told BA. "It's not as simple as 'just send me some tape.'"
It is possible to apply the epoxy tape while the rotor blades are still attached to the helicopter. But that is "a miserable job" that requires standing on a ladder while attempting to place the tape in precisely the right area, a task that Kochy says he "would not wish on my worst enemy." Airwolf advises operators to have the rotor blades removed - which requires an A&P - so tape application can be accomplished more easily and accurately on a stable work surface.
We use 3M tape on all our 500s &300 saves a lot of damage buy it by the role,
If I remember the kit is very expensive, must make sure no air under tapes, don't know if they supply mastic for edges as well.
3M make a fair no of tapes for leading edges
Erosion Protection
3M? Polyurethane Protective Tape 8681HS Transparent, 1 in x 36 yd, 9 per case, Non-Skip Slit
go to documentation lots of useful tips on removing, repairs &installing
Tapes will affect lift, especially noticeable in hot & high conditions.