407 Driver Posted March 17, 2006 Report Posted March 17, 2006 From Justhelicopters.com ---------------------------------- Subject: Re: Astar AS350 starflex failures After having a starflex arm failure occur on start-up on an starflex with less than 100hrs on it and new shock struts and heel springs on the helicopter I am looking for any information anyone may have concerning starflex failures. THIS WAS NOT GROUND RESONANCE. We were lucky in that the starflex failed prior to reaching groung idle. The aircraft was about to depart from a rig in the GOM and could have been catastrophic. Eurocopter claims a 15 MPH wind with an corrisponding 15 mph updraft probably caused the failure. If thats the case EVERY flight in the GOM off a rig would be susceptible to these types of failures. Any help with info and details would be appriciated, Thanks..... -------------------------------------------------------------------------------------- On February 2, 2004 our AS-350B experienced a failure of a new “0 time” Starflex part number 350A31-1916-00 during a post installation run up. The pilot was slowly advancing the fuel flow lever to the flight detent position. Just prior to the flight rpm, a main rotor blade was observed to go out of track and the aircraft began to bounce violently. The fuel flow lever was immediately retarded as the aircraft continued to bounce and rotate to the right. The aircraft ultimately rotated 270 degrees to the right and sustained substantial damage to the tail boom, I beams, cabin area, and aft fuselage. The aircraft had been positioned in its normal parking spot on dry level asphalt. During two post accident inspections by American Eurocopter technical experts, no installation or maintenance errors were noted that could explain this failure. AEC has suggested that this failure of the starflex was the result of ground resonance, although the Chief Pilot and two senior A&P mechanics present at the time of the accident observed nothing that resembled ground resonance. Subsequent checks of landing gear and other components associated with ground resonance found all items meeting Eurocopter parameters. After some research and discussions with other operators we have learned that this is not an isolated incident. There have been two similar incidents in Southern California, and another in Northern California. Other strikingly similar failures have been reported in Texas, Louisiana, Washington, Canada, and Australia. These incidents have occurred at both a hover and on the ground. Representatives of American Eurocopter have attributed most of these starflex failures to ground resonance and pilot mishandling. Contributing to the confusion is the fact that the starflex is made of composite materials that are not easily analyzed for failure. Quote
PerfectTrack Posted March 17, 2006 Report Posted March 17, 2006 my question to them, since nobody eluded to it, was how do they tie them down in these high winds? Are they tying them down properly? During constant high winds, guys might get the impression you tie them down tight, really tight. You don't. And overall was there a preflight done? They're lucky they didn't just clear the deck when it happened. Regardless of new springs on the skids, they don't do a **** if they're not touching the ground. If i recall, alot of rig decks are covered in a net, can they prove the spirings were in contact with the ground, or can we assume they may have been elevated off the ground because of the net. Yes there may have been a defect internally, but that would mean it got by several non detructive steps without detection. Highly unlikely in my opinion. Starflex's by nature are very tough, I've seen a broken one from a canadian operator who kept flying even though the vibration was getting worse, it fell apart on the ramp as soon as he rolled the throttle off. I've seen them after a rollover with barely a mark on them and have seen them splintered beyond recognition too. These guys are looking to blame someone but the whole story isn't available to us. Quote
southoftheborder Posted March 17, 2006 Report Posted March 17, 2006 Having flown in the GOM I know how windy it can get sitting on the deck, have I seen all three blades tied down thats a good question. I know when I flew A-star's we were told to alway tie the blades down to eliminate the blades flapping in the wind thus possibly leading to premature cracking in the star. Fly often but fly safe SOB ps Saturn Five rocket from Appollo 19 that never went into orbit. Man do I feel small Quote
amodao Posted March 17, 2006 Report Posted March 17, 2006 Of the 10 or so cracked starflexes I have had to deal with all were fixed by filing to the limit specified in the MM. They would last about 400-500 hrs after the initial crack filing before the crack elongated beyond limits. Most of the time the cracks were on the top side and about 4 inchs outboard of the curved areas. The main reason for cracking was the failure of the crew to tie the blades down in windy situations. I once was sent to Nordegg to replace a starflex that had cracked overnight after a storm. The storm was severe enough to break all three tie downs. A 204 at the same job had the blade come down and dent the T/R driveshaft cover. The Star flex didn't look the one in the picture it was less severe. I think someone didn't tie the blades down and then started in some very heavy winds. Quote
amodao Posted March 17, 2006 Report Posted March 17, 2006 I would also like to add that I have changed a tx'd starflex that once removed reveiled 3 layers on corrosion washer on top of the mast attachment flange. This condition can prevent proper torquing of the attachment bolts and possibly lead to some damaging head walking. I believe one operator in Canada had one of these incidents and it negatively affected the aircrafts flight characteristics. We have many -1916 and -1917 starflex's installed in our fleet and most of them have made it to their retirement life. We did have one -1916 starflex debond a coupling last year. Was noticed during maintenance and it didn't move anywhere thanks to the white plug. Quote
PerfectTrack Posted March 17, 2006 Report Posted March 17, 2006 "I know when I flew A-star's we were told to alway tie the blades down to eliminate the blades flapping in the wind thus possibly leading to premature cracking in the star" Yes, you want to restrain your blades from excess flapping but you also do not want to flex them to their lower limit and stress them. The Starflex in that area is made to flex up and down, yet it's main strength is fore and aft. If you notice the curvature of the arms, they are on an upwards angle because for coning. to pull the blade down and leave a force on the starflex after excessive tie down force is applied, you'd just be asking for trouble. I think they found it. Quote
cyclic monkey Posted March 17, 2006 Report Posted March 17, 2006 Here's a Labrador after the blades were pulled down too hard........ Don't try this at home !! Quote
Guest sharky Posted March 17, 2006 Report Posted March 17, 2006 So how tight should the blades be tied down PT? Quote
Blackmac Posted March 17, 2006 Report Posted March 17, 2006 The blades of any 3 + bladed helicopter should be tied down taking the slack snuggly and tied to the helicopter. If the helicopter should bounce, the blades will bounce with it. The blades of a two bladed system should both be tied down as in the above fashion, except at 90 degrees to the helicopter, to prevent flapping of the one blade and causing rocking of the helicopter. This is assuming high winds on the flight deck. Tie the blades to the helicopter and the helicopter to the flight deck. Cheers, Don Quote
DGP Posted March 17, 2006 Report Posted March 17, 2006 We are changing our's as we speak...nice crack on one arm found during DI Quote
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.