the infuriating AD: 2004-06-52
The March 18, 2004 AD might just fall apart from illogic.
Supposedly, it's based on two instances of fatigue cracking, possibly from moisture penetration and corrosion. Fatigue cracking is a result of stress and number of cycles, right? But for most of the fleet's blades (-2's), the number of cycles is unchanged: 2200 hours. So the AD which purports to reduce fatigue cracking does not reduce the number of cycles on the blades. ?!? Say what?
But then the FAA (and Robinson) try to dazzle/hoodwink us, without even benefit of smoke and mirrors, and supposedly solve a fatigue-cycle crack by instituting a 10-year CALENDAR life limit! (New deal--previously the FAA had no requirement, and Robinson's 12-year-life was irregularly applied by the maintenance community.)
And there has never been, so far as I can discover, a single shred of evidence that any rotor blades have failed because of calendar age--for instance, by being bolted to a dormant R22. ("Dormant": for instance, one which accumulates 100 hours in 18 years).
Whatever committee wrote the AD is seriously out of contact with reality. They would have us believe they're trying to reduce fatigue cracking, but their "remedy" (for -2's) allows the same number of hours-in-service (2200), so the entire fleet's blades will ultimately be allowed the same number of fatigue cycles as before the AD. What do they think they're changing? Did the authors have any aviation background, or is this equal-opportunity-employment at its worst?
The maximum-calendar-life limit is absurd, unless they know something they're not telling us! Fatigue cycles, as we all know, do not accumulate while the helicopter is not flying. Calendar AGE of the blades has yet to be shown to be a cause of failure (anybody know of a study?). Even IF the fatigue cracking has a root cause in moisture, and even IF it were true that old-age-blades accumulate more moisture, they've ignored the 10%-40% (?) of the fleet that IS stored in humidity-controlled hangars.
One hopes that this AD will soon be revised. Radically. As is, it's an embarrassment to both the FAA and Robinson. Incredible! Preventing flight-induced fatigue cracking by scrapping blades because they've been sitting (unstressed, unflown) in the hangar too long? Absurd!