As350 Hydraulic System Failures: too many??
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As350 Hydraulic System Failures: too many??
Just read the new of hawaii as350 crash, high experience pilot, with Hydraulic Failure, apparently not being such a difficult procedure, results extrange to me, the sad final result.
Last week I was informed of the way an accident happened in France at SAF helicopters some time ago, with a helicopter property of Heliand.
High time instructor and a pilot training "Gov failure procedures" in a AS350B3.
At some point in flight, having normal rotorRPM variation due to flying in manual mode, helicopter started shaking violently and the controls were extremely difficult to move.(Just like with Hyd Failure but worse due to vibration).
Final result: crashed in a field, both survived.(helicopter completely destroyed)
Eurocopter explanation:Hydraulic system servos entered in resonance due to Hyd Fluid pressure variations caused by Rotor Rpm variations.
There is already an SB to solve it, that as far as i know is not aplied to new AS 350´s.
HOW MANY OF YOU KNOW OF SIMILAR HYDRAULIC SYSTEM FAILURES IN AS350B3??
AND WHAT EXPLANATION OF THE CAUSE WERE YOU GIVEN??
Last week I was informed of the way an accident happened in France at SAF helicopters some time ago, with a helicopter property of Heliand.
High time instructor and a pilot training "Gov failure procedures" in a AS350B3.
At some point in flight, having normal rotorRPM variation due to flying in manual mode, helicopter started shaking violently and the controls were extremely difficult to move.(Just like with Hyd Failure but worse due to vibration).
Final result: crashed in a field, both survived.(helicopter completely destroyed)
Eurocopter explanation:Hydraulic system servos entered in resonance due to Hyd Fluid pressure variations caused by Rotor Rpm variations.
There is already an SB to solve it, that as far as i know is not aplied to new AS 350´s.
HOW MANY OF YOU KNOW OF SIMILAR HYDRAULIC SYSTEM FAILURES IN AS350B3??
AND WHAT EXPLANATION OF THE CAUSE WERE YOU GIVEN??
I think there was an accident in Los Angeles (early last year?) involving a media AS350. Aircraft experienced a hydraulic malfunction and female pilot crashed (fatal) whilst attempting to land.
I am also aware of instances of Training Captains scrubbing female students qualifying on type, due to not enough physical strength to fly the helicopter without hydraulic boost.
Fortunately us 76 & 412 pilots don't get scrubbed for the same reason!
I am also aware of instances of Training Captains scrubbing female students qualifying on type, due to not enough physical strength to fly the helicopter without hydraulic boost.
Fortunately us 76 & 412 pilots don't get scrubbed for the same reason!
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Strength
I do not know about the B3, I know B1s and B2s are stiffer to fly hyd out than the Bs but I am surprised to hear of crashes, and people being chopped due to lack of physical strength. Is it insufficient training? Or is it really a problem EC should be looking at?
It is not easy, but slow steady control movements work for me. Suddenly hoofing loads of power after a quick approach does cause all kinds of wobbles, but as with most helo flying smooth flying and pre-empting what will happen makes life much easier. OK engine out hyd out would be v interesting but then it really would not be your day.
It is not easy, but slow steady control movements work for me. Suddenly hoofing loads of power after a quick approach does cause all kinds of wobbles, but as with most helo flying smooth flying and pre-empting what will happen makes life much easier. OK engine out hyd out would be v interesting but then it really would not be your day.
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Jack Stall / and unfriendly pushbuttons
that are too close together - and suck away the hyd press. (should be toggle switches for the test function - there's an STC out for the swap-around of the push-buttons)
http://www.airsafety.com/reports/ROWS070308B.pdf
http://www.airsafety.com/reports/ROWS070308B.pdf
I have flown several types of helicopters that produced hard to move controls when the hydraulics quit (and some that were impossible to move) but none should have caused a crash during landing.
If one were to add an engine(s) failure forcing an autorotation....I would imagine the result would be a bit interesting.
Why is it the 350 has such a miserable record for inability of controlled flight after a loss of hydraulics? Thus far it is also the only aircraft I have heard of that has "jack stall" issues as well.
Is there something lacking in the design of the flight control system?
Rumors have been heard the particular aircraft has had a history of problems.
If one were to add an engine(s) failure forcing an autorotation....I would imagine the result would be a bit interesting.
Why is it the 350 has such a miserable record for inability of controlled flight after a loss of hydraulics? Thus far it is also the only aircraft I have heard of that has "jack stall" issues as well.
Is there something lacking in the design of the flight control system?
Rumors have been heard the particular aircraft has had a history of problems.
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AS350 Hyds out,
I'm sure this has been thrashed to bits before as a subject, but for a very good reason Auz military do not allow, and Brit mil recommend you don't, fly below 10 knots hyds out. Several lost helicopters have proven this around the world. Last time I was in McAlpines in Oxford there was a victim being repaired. 
In the Gazelle days we had to take 2 pilots up below minus 10(?) degrees C due to Hyds out properties. Lower temp was possible by proof of performance at lower increments with 2 bods on the sticks.
Same reason Brit Mil do not fly thier BBs IFR single Pilot, it can take too long to get it down single pilot Hyds out before fatigue gets you.
(Expect a heap of tosh about friction nuts and more beans for breakfast but I'll ignore them in advance!)
In the Gazelle days we had to take 2 pilots up below minus 10(?) degrees C due to Hyds out properties. Lower temp was possible by proof of performance at lower increments with 2 bods on the sticks.
Same reason Brit Mil do not fly thier BBs IFR single Pilot, it can take too long to get it down single pilot Hyds out before fatigue gets you.
(Expect a heap of tosh about friction nuts and more beans for breakfast but I'll ignore them in advance!)
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i'm going on 2K hrs on type so i have done a number of hydraulic failures in training. i have never had a real one, but in my experience, the astar without hydraulics is entirely manageable. it is a lot of work and may involve getting the appropriate knee involved in order to some of the load of the shoulder, arm, wrist, and hand.
whether or not the hydraulic system is adequate for the job has been debated many times before, but if you are not doing something that you should not be doing, then servo-transparency or jack stall is very unlikely. most of the time i have in this type is doing production longline work all over North America, and in the course of normal duties i have never experienced it.
the design of the system may leave something to be desired. keep in mind i am not an engineer, but there is something about running a constant pressure pump in a closed system that seems questionable. also, the belt drive might be considered "fromage" but again, it has served me well enough.
fly safe.
whether or not the hydraulic system is adequate for the job has been debated many times before, but if you are not doing something that you should not be doing, then servo-transparency or jack stall is very unlikely. most of the time i have in this type is doing production longline work all over North America, and in the course of normal duties i have never experienced it.
the design of the system may leave something to be desired. keep in mind i am not an engineer, but there is something about running a constant pressure pump in a closed system that seems questionable. also, the belt drive might be considered "fromage" but again, it has served me well enough.
fly safe.
A trick that works a treat on the Bell 204/205 single hydraulic versions and Bell 206 as well as the Sikorsky S-58T with the Aux hydaulics out.....was to apply a very gentle pressure in the direction you wanted the cyclic to move and wait while the feedback forces motored the stick to the desired position and then relax until you needed to move it again.
The collective on most Hueys was easy up and hard down which could be a reason to eat Gorilla Grits in the morning but still not a big deal.
I always felt I was carrying the helicopter with my left hand when doing without the Aux Hydraulics on the 58T.....perish the thought of a two hour flight like that.
Having never flown the 350.....does any of that sound like what a 350 flys like without hydraulics?
The collective on most Hueys was easy up and hard down which could be a reason to eat Gorilla Grits in the morning but still not a big deal.
I always felt I was carrying the helicopter with my left hand when doing without the Aux Hydraulics on the 58T.....perish the thought of a two hour flight like that.
Having never flown the 350.....does any of that sound like what a 350 flys like without hydraulics?
I think you will find there is no "motor" on the cyclic on the 350. When you do hyd out training there is a very simple set of rules as to the order in which you disable the system....this is in order to use the reservoir available which will give you around 6 -10 control inputs before it runs out and then when you have slowed the aircraft to say 80 kn you turn off the hyd all together . This is to avoid having partial hyd support to one or other servo. When you turn the main hyd back on you first need to have replenished the reservoir by re pressing the hyd test button. I think sasless has his own issues with 350 ,s and find his " is there a problem with the system ?" somewhat insincere !! Certainly girls have crashed these machines in the past due to very heavy controls without hyd and even for a man they are heavy especially in the hovver. ( i know ...not recommended )
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the flight manual states very clearly that "hovering should not be attempted" because it is a bear to handle in the hover. I know of a machine that was written off in canada because the driver tried to put down a load and then, lay down the longline and he lost control in the hover.
a low speed run on is recommended, which is tough enough, especially with a B3 tail rotor. it is definitely doable though.
i can see how some of the fairer sex would have trouble with a hyd failure as the machine does become very heavy
a low speed run on is recommended, which is tough enough, especially with a B3 tail rotor. it is definitely doable though.
i can see how some of the fairer sex would have trouble with a hyd failure as the machine does become very heavy
I think sasless has his own issues with 350 ,s and find his " is there a problem with the system ?" somewhat insincere !!
Having clearly stated I have not flown a 350.....I posed a question where I asked if the 350 flight controls "felt" like some aircraft I have flown before without hydraulics.
Perhaps you read more into the question than was asked.
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R U strong enuff?
I find it interesting that in most organisations we concentrate on two aspects of a hydraulic failure, immediate actions and the landing.
Certainly the control forces on the AS350B3 are heavy and they are no better, and probably worse, on the EC120. I wonder how many of us would handle a hydraulic emergency say some 60 + miles out to sea with no option but a return to land. I fear that many of us would be absolutely knackered by the time we were ‘feet dry’ that the landing might be rather exciting and that some of us might not even make it; either running out of fuel because they flew so slowly (with less force required on the controls) or just running out of stamina trying to keep the aircraft in a higher speed range.
Does anyone have any experience of a practice, or a real, hydraulic failure in one of these types that lasted for more than just a few minutes? How did you do?
Certainly the control forces on the AS350B3 are heavy and they are no better, and probably worse, on the EC120. I wonder how many of us would handle a hydraulic emergency say some 60 + miles out to sea with no option but a return to land. I fear that many of us would be absolutely knackered by the time we were ‘feet dry’ that the landing might be rather exciting and that some of us might not even make it; either running out of fuel because they flew so slowly (with less force required on the controls) or just running out of stamina trying to keep the aircraft in a higher speed range.
Does anyone have any experience of a practice, or a real, hydraulic failure in one of these types that lasted for more than just a few minutes? How did you do?
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Hello,
We work and train in EC 120 and AS 350. The machines behave quite alike, but 350 need almost 2 times more power to control at low speed.. They are both controllable in flight, landing , hover and take off. A very few tricks but lot of pwer and guts is required.. Most important is the 350 goes right down to 15 knots, then it goes to left with EVERYTHING, be prepared with the controls. If you loose the machine to left it is very tough and you need LOT of control movement to get it back.
SASless, the problem is the elastomeric stuff, straight and level works with small movements w/o any bigger effort but at low speeds it feels like whole world is against you. And wrong rubber parts below -25 C makes it impossible.
fly safe
We work and train in EC 120 and AS 350. The machines behave quite alike, but 350 need almost 2 times more power to control at low speed.. They are both controllable in flight, landing , hover and take off. A very few tricks but lot of pwer and guts is required.. Most important is the 350 goes right down to 15 knots, then it goes to left with EVERYTHING, be prepared with the controls. If you loose the machine to left it is very tough and you need LOT of control movement to get it back.
SASless, the problem is the elastomeric stuff, straight and level works with small movements w/o any bigger effort but at low speeds it feels like whole world is against you. And wrong rubber parts below -25 C makes it impossible.
fly safe
SASless, I've done a lot of practice hydraulics off in the Huey and AS350B and BA, and never noticed one being particularly harder than the other control-forces wise, with run-on landings or in the hover (not common practice, but done a few times).
Never had a real hydraulics failure in the AS350 so can't comment on any differences from the practice case - as nigelh mentioned above, there are accumulators on the cyclic / collective servos that give you a little bit of time to get the speed down, then you isolate the hydraulics and run it on.
Similar magnitude of push and pull forces to the Huey, I reckon, although maybe pedals a bit harder in the Squirrel.
Never had a real hydraulics failure in the AS350 so can't comment on any differences from the practice case - as nigelh mentioned above, there are accumulators on the cyclic / collective servos that give you a little bit of time to get the speed down, then you isolate the hydraulics and run it on.
Similar magnitude of push and pull forces to the Huey, I reckon, although maybe pedals a bit harder in the Squirrel.
350 Hydraulic issues...........
In response to SASless question and NOT pertaining to what may or may not have happened in this accident:-
The gross weight limitation of the 350 is the controllability without hydraulics at the first instance.
Of the models in current production the B3 has the WORST useful load internally due to this restriction. The B2 is lighter and the B4 has Dual Hydraulics and subsequently a higher MTOW (2427 kg). Frankly unless you are conducting sling or high altitude work I have never understood why you would want a B3. There is no significant internal performance over a B2, unless of course you are operating as mentioned before, and you have a slightly lower specific range ~ 2.5 - 3%.
Problems you can have................
Hydraulic failure and assymetric or no pressure in the accumulators meaning one servo will run out of pressure before the others. The hydraulics should be turned "OFF" prior to the deletion of the accumulators to be sure.
Misuse/Misunderstanding of the "HYD TEST" and "HYD OFF" switches.
"HYD TEST" simulates a failure of the hydraulic pump and is a method of testing for the assymetric problem. Move the cyclic until the accumulators deplete and make sure the assistance stops symmetrically.
"HYD OFF" is exactly that. Turn the hydraulics "OFF" and thats what you get no assistance from the accumulators, but you WILL still have assistance in the yaw channel via the compensator.
Now heres the catch - when there is no hydraulic pressure and you push the "HYD TEST" button you will purge the accumulator in the yaw channel compensator which is standard procedure after shutdown. In flight with a hydraulic failure if you activate the switch this accumulator will no longer assist you and you are out of the bounds of the certifcation limits. The pedal pressure required will lift you out of the seat and the yaw will more than likely be uncontrollable to the left on reduction in airspeed. Couple this with a heavy cyclic and it's interesting. Its worse in the B3 than the B2, have a look at the difference in the tabs added on to the TR blades which you are in competition with.
Exceeding gross weight:- In a B3, unless you keep an eye on what you are loading into the helicopter, it is easy to exceed the maximum internal gross weight without seeing any obvious indications of exceeding these limits. This helicopter can exceed its internal gross weight limit by 550 kgs (1212 lbs) using TOP at SL ~ 25 deg C - i.e 25% over internal MTOW!!!!
This accident report will probably enlighten you as to how it all works. Unfortunately there have been numerous cases of misunderstanding of the system.
http://www.tsb.gc.ca/en/reports/air/...2/A03O0012.asp
The gross weight limitation of the 350 is the controllability without hydraulics at the first instance.
Of the models in current production the B3 has the WORST useful load internally due to this restriction. The B2 is lighter and the B4 has Dual Hydraulics and subsequently a higher MTOW (2427 kg). Frankly unless you are conducting sling or high altitude work I have never understood why you would want a B3. There is no significant internal performance over a B2, unless of course you are operating as mentioned before, and you have a slightly lower specific range ~ 2.5 - 3%.
Problems you can have................
Hydraulic failure and assymetric or no pressure in the accumulators meaning one servo will run out of pressure before the others. The hydraulics should be turned "OFF" prior to the deletion of the accumulators to be sure.
Misuse/Misunderstanding of the "HYD TEST" and "HYD OFF" switches.
"HYD TEST" simulates a failure of the hydraulic pump and is a method of testing for the assymetric problem. Move the cyclic until the accumulators deplete and make sure the assistance stops symmetrically.
"HYD OFF" is exactly that. Turn the hydraulics "OFF" and thats what you get no assistance from the accumulators, but you WILL still have assistance in the yaw channel via the compensator.
Now heres the catch - when there is no hydraulic pressure and you push the "HYD TEST" button you will purge the accumulator in the yaw channel compensator which is standard procedure after shutdown. In flight with a hydraulic failure if you activate the switch this accumulator will no longer assist you and you are out of the bounds of the certifcation limits. The pedal pressure required will lift you out of the seat and the yaw will more than likely be uncontrollable to the left on reduction in airspeed. Couple this with a heavy cyclic and it's interesting. Its worse in the B3 than the B2, have a look at the difference in the tabs added on to the TR blades which you are in competition with.
Exceeding gross weight:- In a B3, unless you keep an eye on what you are loading into the helicopter, it is easy to exceed the maximum internal gross weight without seeing any obvious indications of exceeding these limits. This helicopter can exceed its internal gross weight limit by 550 kgs (1212 lbs) using TOP at SL ~ 25 deg C - i.e 25% over internal MTOW!!!!
This accident report will probably enlighten you as to how it all works. Unfortunately there have been numerous cases of misunderstanding of the system.
http://www.tsb.gc.ca/en/reports/air/...2/A03O0012.asp
We operate a fleet of 30+ BBs, each of which has over 5000hrs. Since day one, we have had NO HYD FAILS, so the system is reliable if serviced correctly. A hyd fail in flight gives the pilot at least 20secs of manoevring before the accus exhaust - more than enough time to reduce speed to 65kts. At this speed, there are virtualy no loads on the controls - it's only when speed is reduced on short finals that the loads increase. As long as a run-on lamding is made with 10kts across the disc even small, feeble students are able to put down with no problems. But, ignore the instruction in the RFM and try to reduce speed to a hover, and life gets more difficult (but not impossible).
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If I'm not mistaken, the Australian military did a lot of testing of these machines hydraulics off, and didn't much like the results...
I don't believe the report was ever made public.
I don't believe the report was ever made public.
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wiisp
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We work and train in EC 120 and AS 350.
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We work and train in EC 120 and AS 350.
Australian military-wise, we operated the B, which was then modded to BA, without the compensator in the tail rotor hyd system.
Many, many practice hydraulics off approaches were flown without much in the way of dramas using the flight manual procedure of detecting the problem, slowing to an appropriate speed if required and then operating the hydraulic isolate switch to dump all pressure from the accumulators at once and proceeding to a running landing.
There was an accident where a student wasn't sufficiently strong to control the helicopter during a running landing and the instructor couldn't recover - they rolled it on its side on the grass. I don't know the full details of that one but I vaguely remember hearing it might have been that the hydraulic test switch was used to simulate the failure, but they didn't subsequently use the hydraulics isolate, which may have contributed to the problem.
Some time after I left, I believe they fitted the tail rotor compensator, probably after the investigation Shawn referred to? Perhaps someone in the know can elaborate on that.
Anyhow, my point is that in my experience, flying those variants of Squirrel / Astar with hydraulics off a lot (including hovering although that wasn't done as a rule), there wasn't a problem for the average pilot if flight manual procedures were followed. Maybe the other models are significantly harder, I don't know, but at least in the B and BA there was no big scary issue.
Many, many practice hydraulics off approaches were flown without much in the way of dramas using the flight manual procedure of detecting the problem, slowing to an appropriate speed if required and then operating the hydraulic isolate switch to dump all pressure from the accumulators at once and proceeding to a running landing.
There was an accident where a student wasn't sufficiently strong to control the helicopter during a running landing and the instructor couldn't recover - they rolled it on its side on the grass. I don't know the full details of that one but I vaguely remember hearing it might have been that the hydraulic test switch was used to simulate the failure, but they didn't subsequently use the hydraulics isolate, which may have contributed to the problem.
Some time after I left, I believe they fitted the tail rotor compensator, probably after the investigation Shawn referred to? Perhaps someone in the know can elaborate on that.
Anyhow, my point is that in my experience, flying those variants of Squirrel / Astar with hydraulics off a lot (including hovering although that wasn't done as a rule), there wasn't a problem for the average pilot if flight manual procedures were followed. Maybe the other models are significantly harder, I don't know, but at least in the B and BA there was no big scary issue.
Does anyone have any experience of a practice, or a real, hydraulic failure in one of these types that lasted for more than just a few minutes? How did you do?