AS350 Astar/Squirrel
Goose boy - we operate 27 AS350s with 2 axis autopilots, and that's what my chief engineer told me a couple of days ago.
TheFlyingSquirrel - as I understand it, the Squirrel was found to have numerous vibe problems. Some were removed/reduced by the antivibrator on the rotor head - some ground resonance (or something similar) difficulties were reduced by adding the springs on the back of the skids and dampers to the skid mountings. The anti vibration units under the floor are lumps of lead on flat springs and are mounted one under each pilot's seat. They are tuned in the factory to reduce the vibration levels felt by the front crew (engineers speak of 'nodes' whatever they are). It's probably the size and weight of the lead that makes them a problem if the spring or mounting fractures in flight!
TheFlyingSquirrel - as I understand it, the Squirrel was found to have numerous vibe problems. Some were removed/reduced by the antivibrator on the rotor head - some ground resonance (or something similar) difficulties were reduced by adding the springs on the back of the skids and dampers to the skid mountings. The anti vibration units under the floor are lumps of lead on flat springs and are mounted one under each pilot's seat. They are tuned in the factory to reduce the vibration levels felt by the front crew (engineers speak of 'nodes' whatever they are). It's probably the size and weight of the lead that makes them a problem if the spring or mounting fractures in flight!
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I have been told that they reduce vibration substantially , they were not going to be installed on EC120 but after first flights they changed their mind , with a 20 to 30 lb weight penalty there must have been good reason.
A "node" is a stationary point in a vibrating system.
Visualise a skipping rope, or tail rotor drive shaft. Start shaking it at one end, keeping the other held firm. As it vibrates, one part of the rope/shaft won't move - that's the node. Shake it / turn it faster, the node moves.
The lead weights I assume move the nodes in the AS350 cabin to near the seat attachment points - less movement, less bounce in the pilots' step when they get out.
Visualise a skipping rope, or tail rotor drive shaft. Start shaking it at one end, keeping the other held firm. As it vibrates, one part of the rope/shaft won't move - that's the node. Shake it / turn it faster, the node moves.
The lead weights I assume move the nodes in the AS350 cabin to near the seat attachment points - less movement, less bounce in the pilots' step when they get out.
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Thanks for the pics Chopperdr - know I can see what everyone is yappin about. I personally can't see how a dumb piece of lead can have any significant advantage - but I presume it acts as a counter-balance? I've glued it up if you don't mind - i'll remove it if you like - thanks again. Also, how can it fall onto an acutator?
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The relevant Eurocopter Alert Telex equires a visual inspection at the next, and each, ALF check (after last flight of day) until they introduce a modification to prevent any interference with the trim actuator rod in the event of failure of the vibration damper blade.
No mention of engineers needing to do it. Extension of Check A, so effectively daily.
Anyone ever come across such a damper blade crack/failure or know the TT/history of the incident that triggered this?
No mention of engineers needing to do it. Extension of Check A, so effectively daily.
Anyone ever come across such a damper blade crack/failure or know the TT/history of the incident that triggered this?
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So, can we take it that AS350s are not 'Grounded Worldwide' and all that's happened is Eurocopter has issued an AD requiring an additional check to be added to the other daily checks?
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Heliport
Yes, at least seems clear to me.
Oldbeefer
Tend to agree it is OTT, which is why I'm interested to try and find just how many incidents anyone knows of. What worries me is the added risk of finger trouble on a pretty big cowling that I reckon could cause some serious damage if it came undone.
OK it's got 3 latches but it is not light and a bit awkward. History tends to prove that if pilots (and engineers) open cowlings, sooner or later they'll forget to close them properly.
Balance of risk then. And allocation of responsibility!
Yes, at least seems clear to me.
Oldbeefer
Tend to agree it is OTT, which is why I'm interested to try and find just how many incidents anyone knows of. What worries me is the added risk of finger trouble on a pretty big cowling that I reckon could cause some serious damage if it came undone.
OK it's got 3 latches but it is not light and a bit awkward. History tends to prove that if pilots (and engineers) open cowlings, sooner or later they'll forget to close them properly.
Balance of risk then. And allocation of responsibility!
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TheFlyingSquirrel-
That thing is a vertical vibration absorber, designed to "twang" probably at 4 per revolution frequency, kind of like a person standing on a diving board can make the board bounce at its natural frequency. It is resonant at the frequency, and so it absorbs those vibrations from the surrounding structure. It is very effective, that kind of absorber is used in the industry quite a bit. If it is not tuned right, that area of the cabin will feel like a rocky road. Two absorbers like that are located in the UH-60L near the pilot's step. The stiffness of the diving board and the amount of lead are selected to make it "like" the 4 per rev (which is probably about 21 to 25 Hz).
The place near its mount that is to be inspected is where the vibration gets passed through, so it is subject to high stresses, and thus the crack inspection.
I think I see a place on the weight for a vibration pickup to be mounted (the circle with a hole). If so, this is probably used at the factory to fine tune the absorber by reading how much it shakes in flight, and adding or subtracting weight until it is peaked out.
That thing is a vertical vibration absorber, designed to "twang" probably at 4 per revolution frequency, kind of like a person standing on a diving board can make the board bounce at its natural frequency. It is resonant at the frequency, and so it absorbs those vibrations from the surrounding structure. It is very effective, that kind of absorber is used in the industry quite a bit. If it is not tuned right, that area of the cabin will feel like a rocky road. Two absorbers like that are located in the UH-60L near the pilot's step. The stiffness of the diving board and the amount of lead are selected to make it "like" the 4 per rev (which is probably about 21 to 25 Hz).
The place near its mount that is to be inspected is where the vibration gets passed through, so it is subject to high stresses, and thus the crack inspection.
I think I see a place on the weight for a vibration pickup to be mounted (the circle with a hole). If so, this is probably used at the factory to fine tune the absorber by reading how much it shakes in flight, and adding or subtracting weight until it is peaked out.
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nicks correct, you can see the cross hairs where the 6 attach bolts p/u the airframe, that is the pickup point. also note the washer glued to the hammer weight, this is very common to see washers or various amounts of loose change glued on the hammer face to fine tune the airframe.
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chopperdr,
If that loose change are Franc coins, it means someone has found a use for the Franc!
If you guys would like, I can post some comments on the type of absorbers commonly used.
If that loose change are Franc coins, it means someone has found a use for the Franc!
If you guys would like, I can post some comments on the type of absorbers commonly used.
Nick,
Please do provide us a topic for some vibrant discussion....hopefully the frequency of posts in reply will vary with the source. Maybe that bit of information will dampen any misunderstandings and smooth any inconsistencies.
Please do provide us a topic for some vibrant discussion....hopefully the frequency of posts in reply will vary with the source. Maybe that bit of information will dampen any misunderstandings and smooth any inconsistencies.
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nick: your correct, however if you order by part no. from eurocopter, the face value increases by a factor of 4, lead time approx 90 days and the service bulletin requires that the head side is up : )
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hilico: for that a/c hose your okay, in stock, ready to ship, reasonable price, call platinum aviation.
now if i can just figure out how to finance an stc installation of PW207E engine we would really be cooking with gas.
dr
now if i can just figure out how to finance an stc installation of PW207E engine we would really be cooking with gas.
dr
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CD I thought first plan was a RR250 in EC120 , surely with all the disposable income on this site we could raise enuff capital !!! As350b207E is a bit long , any shorter names ? Is Jack K still around talking of platinium ?.
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widgeon: so many more eligable airframes with regards to the astar. the 120 is ok as long as its kept light. as for jack K not sure if he is still involved.
will be at ecl monday
will be at ecl monday