AS 350B2 - UnCFIT
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...sending the aircraft into trees. Control was regained and the aircraft appeared to be okay. The group of skiers were dropped off and a subsequent flight attempted when a vertical vibration was noticed...
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It appears the pilot made more than one error...
...sending the aircraft into trees. Control was regained and the aircraft appeared to be okay. The group of skiers were dropped off and a subsequent flight attempted when a vertical vibration was noticed...
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It appears the pilot made more than one error...
Join Date: Apr 2009
Location: Kelowna, BC
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Your words are a bit harsh for someone who wasn't there, don't you think? Well, take it from someone who was there and that has 4000 hours on the Astar, 9000 hours total time and 5 years of heli-ski experience, and yes, it does matter if you are a ski pilot because it is a different flying world when you are heli-skiing for example, you are never more than 3-4 seconds from tree's, on the way up, or, on the way down. I have had a hydraulic belt break once and had a hydraulic pump fail another time and both times the controls were control-able, and both those times there was time to press the collective hydraulic switch, but this time was different, this time it was like the helicopter was being pulled into the mountain beside me. As for hitting the tree's, I was unaware I had hit any trees as there was no indication that I had. I elected to take off again for a bit of a test flight, without passengers, to see if I could identify what was happening to the hydraulics, when just seconds after lift off I wasback on the ground because of a moderate vibration. TSB found 2 hydraulic servo's that failed the extension/retraction speed's, and, they came up with a theory why the hydraulics indeed locked up. One of the servo's drastically failed the test.
you are never more than 3-4 seconds from tree's, on the way up, or, on the way down
One of the servo's drastically failed the test.
He is right on heliski ops that you do spend a lot of time pretty close to trees when on the lower slopes ( below the alpine runs ). I have flown with a number of these canadian heliski pilots over the years in Whistler and Tiax and monashees and have never come across one less than AAA excellent . They are all truly superb pilots and perform impossible landings , toe in , one skid etc with 40 kn winds etc etc Respect !! He was there and did what he did and i can only imagine we would have all done the same . Flying out there IS different to what most of us experience and certain things are done which we wouldnt do ie sometimes you may have to get out and hot refuel yourself leaving controls unmanned ...there is no alternative . I never thought this was jack stall as i would only expect the cyclic to seize up and not the collective . I also believe it is a high G event and would not happen at low torque and lsing height .
At least it ended up happy !!
At least it ended up happy !!
I know it's annoying when people who weren't there try to judge your actions or tell you what your should have done, so I won't do that. I'd be interested to hear (with the benefit of hindsight) whether you would do anything different if faced with the same situation again. Nigelh, not sure why you say "...i can only imagine we would have all done the same...", 'cos I can only imagine I would not have done the same. Also mystified why you don't think the collective would be equally affected if the cyclic "siezed up" due to a hydraulics/servo problem.
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There is an emergency procedure in the 350 FM called Main Servo Valve Seizure - it has no symptoms or indications as to what the pilot will see if there is such a seizure. It is interesting to note that the immediate action is to shut off the hydraulics...
There is also a very old (1990 era) service letter that talks about this in an oblique way - mentions different extend retract times for the servos. Worth looking at if you're an AS350 driver...
There is also a very old (1990 era) service letter that talks about this in an oblique way - mentions different extend retract times for the servos. Worth looking at if you're an AS350 driver...
Mark . IF the pilot had been aware of a blade strike OF COURSE he would have inspected the blades , but he was not aware of any strike . Under the circumstances of wat i thought was jack stall , i would boot the pax out and do a flight test starting with a hovver ...just as he did .
The manual says reduce collective to reduce the G force ....and funnily enough that is the way to do it !!!!
The manual says reduce collective to reduce the G force ....and funnily enough that is the way to do it !!!!
Join Date: Feb 2001
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The AS 350 has a documented history of loss of control events.
I've attached an interesting TSB (Canada) report, as well as the appendix to the report which lists 25 loss of control events.
Aviation Investigation Report
Hydraulic Flight Control Malfunction
Vancouver Island Helicopters
Eurocopter AS 350 B2 (Helicopter) C-GNMJ
Kamarang, Guyana
06 February 2005
Transportation Safety Board of Canada - AVIATION REPORTS - 2005 - A05F0025
Loss of Control Occurences:
Transportation Safety Board of Canada - AVIATION REPORTS - 2005 - A05F0025
I've attached an interesting TSB (Canada) report, as well as the appendix to the report which lists 25 loss of control events.
Aviation Investigation Report
Hydraulic Flight Control Malfunction
Vancouver Island Helicopters
Eurocopter AS 350 B2 (Helicopter) C-GNMJ
Kamarang, Guyana
06 February 2005
Transportation Safety Board of Canada - AVIATION REPORTS - 2005 - A05F0025
Loss of Control Occurences:
Transportation Safety Board of Canada - AVIATION REPORTS - 2005 - A05F0025
I think with a servo valve seizure (or suspected one due to control malfunction), the drill on every helicopter I have flown is to deselect the hyds - in an aircraft with 2 systems it is a question of deciding which system is at fault.
It would appear that there maybe more issues with the 350 servos than just 'transparency' since a sticking servo valve would produce the 'locked up' controls symptom.
It would appear that there maybe more issues with the 350 servos than just 'transparency' since a sticking servo valve would produce the 'locked up' controls symptom.
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Oldbeefer
The failures on the AS350 series seems to be mostly with Dunlap servos, and in particular with servos that do not meet the tolerances for extend retract times. Hopefully your maintenance folks are on top of that sort of thing.
crab:
What other helicopters have a servo jam emergency in the FM? I don't recall seeing it anywhere else as a specific emergency in all the types I've flown.
The failures on the AS350 series seems to be mostly with Dunlap servos, and in particular with servos that do not meet the tolerances for extend retract times. Hopefully your maintenance folks are on top of that sort of thing.
crab:
What other helicopters have a servo jam emergency in the FM? I don't recall seeing it anywhere else as a specific emergency in all the types I've flown.
Shawn, it might not say servo valve seizure but that is what control malfunctions (Sea King, Wessex, Lynx) mean - either a hardover or a seizure and the drill is to select the faulty system off.
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I had a chat to a eurocopter man recently about getting a dual hydraulic system on the b2 to counter this problem, and he said as you guys said that the weak part in the chain is the actuators and not the pump but the reason he gave for a poor performing actuator was if they had one that could handle greater loads the actuator would shatter the starflex, maybe i picked it up wrong but he seemed to be saying that the poor performing actuator was in effect letting you know with SCT that you had gone too far or the turbulance had brought you too far.
would be interested if anyone has another take on that. seeing as my ass is in an an Astar for 6 hours a day 6 days a week!
would be interested if anyone has another take on that. seeing as my ass is in an an Astar for 6 hours a day 6 days a week!
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whatsarunway:
If that were the case, there would be a lot of shattered starflex heads on AS 355s and EC-130s. They all have dual hydraulics, and there is a mod for the AS350B4 for dual hydraulics (if it isn't standard).
If that were the case, there would be a lot of shattered starflex heads on AS 355s and EC-130s. They all have dual hydraulics, and there is a mod for the AS350B4 for dual hydraulics (if it isn't standard).
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I thought that dual hyd only gave redundancy ( if one channel fails the other takes over ) , it does not make the actuators more powerful. As at point of interest are there many cases of "transparancy" on the AS355.
My information (as of 1/29/09), states the EC-130B4 dual hydraulic system is available as an option on a _new_ B3. Retrofitting an existing AS350 is not an approved modification, as it requires replacement of components of the flight controls, hub-shaft, MGB and includes reinforcing the tail boom.
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what i was saying was that the dual hydraulics eliminates the problem of hydraulic failures as a result of a belt or similar but it does not eliminate the problem of the weak actuator and the week actuator is so because if it were stronger it would shatter the starflex.
i have flown b2, b3,(not fitted as standard i know ) and ec130 all with dual hyd and was warned about SCT on them all.
its what i have been told, im not saying its true.
and also if the starflex is so good, why does the ec120 have such a different head although they call it a starflex from memory it has dampers and weights etc.
i have flown b2, b3,(not fitted as standard i know ) and ec130 all with dual hyd and was warned about SCT on them all.
its what i have been told, im not saying its true.
and also if the starflex is so good, why does the ec120 have such a different head although they call it a starflex from memory it has dampers and weights etc.
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It is a JV
Why does the EC 120 have such a different head?
Perhaps it has something to do with the EC 120 not being a French helicopter. It was a JV between France, Singapore and China...and 10 to 15 years 'more modern' than the AS 350.
Perhaps it has something to do with the EC 120 not being a French helicopter. It was a JV between France, Singapore and China...and 10 to 15 years 'more modern' than the AS 350.