As350 Hydraulic System Failures: too many??
The fact is that there have been far too many hydraulic system related mishaps in the AS-350 series. Having been checked out in only the B2 and B3 models my experience is some what limited. But my experience tells me that any extended flight in the AS-350 with the hydraulic system inoperative can be very fatiguing to a point where control may be compromised. While attempting not to sound sexist I cannot help but believe that most women pilots would have difficulty controlling the aircraft after experiencing a hydraulic failure. This may have been evident in AS-350 mishap in Apache Junction Arizona in 2005. The following was copied from a previous post on PPRUNE concerning hydraulic servo transparency. Something has to be said about an aircraft design where even the hydraulic system is not capable of over coming flight load in some situations.
I am really surprised that the AS-350 series was successfully certified with published control forces so high. Even after a single system failure (Hyd or Servo transparency) the resulting control forces must not exceed those outlined as Arm strength N (lb) Design criteria levels in Chapter 14 of the US Federal Aviation Administration Human Factors Guide. Table 14.5.2.1 of this guide clearly states the maximum force for a right hand, lateral control motion to the left should be no more than 6 to 8 pounds. This is far in excess of what is published in the AS-350 RFM. US designed and certified aircraft are required to meet these requirements. These standards were applied when Sikorsky included viscous cyclic control dampers in the H-53 Series to insure that in the event of a control damper bind it could be easily over ridden within the force limitations of the aforementioned table.
I am really surprised that the AS-350 series was successfully certified with published control forces so high. Even after a single system failure (Hyd or Servo transparency) the resulting control forces must not exceed those outlined as Arm strength N (lb) Design criteria levels in Chapter 14 of the US Federal Aviation Administration Human Factors Guide. Table 14.5.2.1 of this guide clearly states the maximum force for a right hand, lateral control motion to the left should be no more than 6 to 8 pounds. This is far in excess of what is published in the AS-350 RFM. US designed and certified aircraft are required to meet these requirements. These standards were applied when Sikorsky included viscous cyclic control dampers in the H-53 Series to insure that in the event of a control damper bind it could be easily over ridden within the force limitations of the aforementioned table.
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I everyone
I am pretty new in this forum .........but not in helicopter operations,I spent 22 years fly and maintenance on 350 most on B2 and B3 series and I never heard so much **** like this.Fortunatly some of you has a brain in the head,Hyd failure means failure!!!!!!red ******* light!!!!!! In B3 series the force on controls without hyd is about 25kg each side in normal helicopter weight.When is at max gross weight is more than 25kg.So I read lot of you very brave ....takeoff whitout hyd just to see if is possible or just to show that the instructor is a good pilot...........the instructor shold be carrefull to teach that never show a student something that is not wrote on FM and never wrote it on a forum where u can find pilots with a lot of experience and pilot with few Hrs and of course everyone take an example .This is the most stupit aeronautical mentality.Red light gives u the time to land immediately and safely.Thats it no bull****.So in every condition red light go down immediately no metter where u are.This is the mentality to save your life.And the biggest **** is to flight back the hely from the field without Hyd.Hyd failure is tested for a short fly time and if u not believe me check the dimensions of the controls bar fron the control to the Hyd sistem.Flight with FM in the brain not under the sit.
I am pretty new in this forum .........but not in helicopter operations,I spent 22 years fly and maintenance on 350 most on B2 and B3 series and I never heard so much **** like this.Fortunatly some of you has a brain in the head,Hyd failure means failure!!!!!!red ******* light!!!!!! In B3 series the force on controls without hyd is about 25kg each side in normal helicopter weight.When is at max gross weight is more than 25kg.So I read lot of you very brave ....takeoff whitout hyd just to see if is possible or just to show that the instructor is a good pilot...........the instructor shold be carrefull to teach that never show a student something that is not wrote on FM and never wrote it on a forum where u can find pilots with a lot of experience and pilot with few Hrs and of course everyone take an example .This is the most stupit aeronautical mentality.Red light gives u the time to land immediately and safely.Thats it no bull****.So in every condition red light go down immediately no metter where u are.This is the mentality to save your life.And the biggest **** is to flight back the hely from the field without Hyd.Hyd failure is tested for a short fly time and if u not believe me check the dimensions of the controls bar fron the control to the Hyd sistem.Flight with FM in the brain not under the sit.
The fact is, a failure of the belt that drives the hydraulic pump will result in the illumination of the hydraulic warning light and an immediate loss of hydraulic pressure. The accumulators are provided to allow for sufficient control of the aircraft to reduce airspeed to 65 KIAS. From this point forward control has to be maintained while overcoming between 15 and 26 lbs of lateral cyclic force. This is not trivial and is part of the justification for going to a duel hydraulic system in EC-130 and having the option for duel hydraulics in the AS-350 series.
Jack, in the second paragraph of your post #41 (which I think you were only quoting) there is some information I believe to be incorrect.
The AS-350 is certified in the U.S. under 14CFR27.
When it comes to a flight control activated by hand, 27.397 would appear to apply. This allows for 100 pounds (45kg) of force to be needed to move a control fore-and-aft, and 67 pounds (30kg) of force to move the control laterally.
This is, as you note, quite high.
The AS-350 is certified in the U.S. under 14CFR27.
When it comes to a flight control activated by hand, 27.397 would appear to apply. This allows for 100 pounds (45kg) of force to be needed to move a control fore-and-aft, and 67 pounds (30kg) of force to move the control laterally.
This is, as you note, quite high.
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Rules Broke...
... er so the AS350 has hydraulic failures , pump drive belt failures , many crashes - NY roof landing on video great example ...
BUT R66 !! oh no ! has a hydraulic system which has none of those problems (like the R44) but can't get certified - because it's against the certification rule....
Shurley shome mistake methinks .... clearly the rules are broken
Must the R66 have hydraulics as bad as an AS350 to get certified - I hope not!
Change the rule - or get the interpretation, "extremely remote", right...
... this is arse-about-face
BUT R66 !! oh no ! has a hydraulic system which has none of those problems (like the R44) but can't get certified - because it's against the certification rule....
Shurley shome mistake methinks .... clearly the rules are broken
Must the R66 have hydraulics as bad as an AS350 to get certified - I hope not!
Change the rule - or get the interpretation, "extremely remote", right...
... this is arse-about-face
FH1100 , 14CFR27.397 pertains to the structural integrity of the flight control system. Should a gorilla enter the cockpit and move the controls then the controls should not break, bend or fail at loads up to those listed. The numbers I sighted are from an FAA human factors report. 14CFR27.141 addresses the control of the aircraft under normal flight conditions and 14CFR27.695 address control after a failure. Both paragraphs are sufficiently vague and list no specific numbers. I can send you a copy of the Human Factors report if you would like.
Jack
Jack
Oh Jack, I'm familiar with the HFDG. I'm just hazy on how you're interpreting the numbers. I get different ones from that chart. In any event, the HFDG does not appear to be regulatory.
Well I don't know about all that, Shawn. All's I know is that there is an FAA Type Certificate Data Sheet Number H9EU that covers the AS-350 and EC-130.
Below is an exerpt from it. Look under "Certification Basis." I took this to mean that the AS-350 was certified under Part 27. No?
Below is an exerpt from it. Look under "Certification Basis." I took this to mean that the AS-350 was certified under Part 27. No?
Well that's not really the point, is it Shawn?
*MY* point is this: Jack Carson wondered how the AS-350 ever got certified with its hydraulic-off control forces so high? He referenced an FAA design document and said the FAA calls for a maximum of only 6-8 pounds of force to be applied to a control (which seemed pretty low to me). He implied that this maximum is/was mandatory. But if you look on the chart that Mr. Carson referenced, look at movement #6 and we see that the recommended force is defined at 71 to 78 pounds. Perhaps Mr. Carson mistakenly referred to this chart and really meant to reference something else.
But even this is all moot because the FAA's Human Factor Design Guide is *not* mandatory, *AND* our U.S. FAR part 27 defines no maximum amount of control pressure. And whether the FAA did the original testing or not, the AS-350 has a U.S. Type Certificate and the certification of the aircraft is based on...wait for it...FAR part 27.
So. Are the hydraulics-off forces in an AS-350 high? Most certainly. Are they unacceptably high? Perhaps for some pilots, yes although no pilot worth his salt will ever admit to it. How did the AS-350 ever get certified with such high control forces? Easy! There are no standards.
For comparison, I had an hydraulic failure once (recently) in a Sikorsky S-55. It made the Astar seem like a piece of cake. Foolishly (and arrogantly) thought I could just fly back to my LZ and land, but abandoned that plan pretty quickly when I realized how much effort it was taking just to fly the bitch. It was horrible. Sometimes you have to admit to yourself that it's not worth it trying to be the hero. So I found a level patch of land and put 'er down. It flew so poorly that I was realistically prepared for it to "not work out so well" (i.e. roll over on landing). It did not...not due to my superior airmanship, but rather sheer dumb luck.
Dang, give me back my JetRanger!
*MY* point is this: Jack Carson wondered how the AS-350 ever got certified with its hydraulic-off control forces so high? He referenced an FAA design document and said the FAA calls for a maximum of only 6-8 pounds of force to be applied to a control (which seemed pretty low to me). He implied that this maximum is/was mandatory. But if you look on the chart that Mr. Carson referenced, look at movement #6 and we see that the recommended force is defined at 71 to 78 pounds. Perhaps Mr. Carson mistakenly referred to this chart and really meant to reference something else.
But even this is all moot because the FAA's Human Factor Design Guide is *not* mandatory, *AND* our U.S. FAR part 27 defines no maximum amount of control pressure. And whether the FAA did the original testing or not, the AS-350 has a U.S. Type Certificate and the certification of the aircraft is based on...wait for it...FAR part 27.
So. Are the hydraulics-off forces in an AS-350 high? Most certainly. Are they unacceptably high? Perhaps for some pilots, yes although no pilot worth his salt will ever admit to it. How did the AS-350 ever get certified with such high control forces? Easy! There are no standards.
For comparison, I had an hydraulic failure once (recently) in a Sikorsky S-55. It made the Astar seem like a piece of cake. Foolishly (and arrogantly) thought I could just fly back to my LZ and land, but abandoned that plan pretty quickly when I realized how much effort it was taking just to fly the bitch. It was horrible. Sometimes you have to admit to yourself that it's not worth it trying to be the hero. So I found a level patch of land and put 'er down. It flew so poorly that I was realistically prepared for it to "not work out so well" (i.e. roll over on landing). It did not...not due to my superior airmanship, but rather sheer dumb luck.
Dang, give me back my JetRanger!
FH1100
The S-55 first flew on 10 Nov 1949. One would wonder exactly what specifications it was designed built and certified to. I would hope that the system (FAA and manufacturers) became a little more intelligent over the years. By comparison the AS-350 was designed, built and certified in the 1970s in Europe. The AS-350 was brought into the US under the bilateral agreement between the FAA and the European authorities cited by Shawn. It was only recently that the AS-350 was certified for complete manufacture in the US. Up until then all aircraft were manufactured, flown and certified in Europe then disassembled and shipped to Texas where they were reassembled for completion and delivery. The question then is: Could the AS-350 have met the entire spectrum of US certification requirement outlined for helicopters in the 1970s? I hope that Shawn may be able shed more light on this subject. To answer FH1100, YES I believe that the B206L-4 Long Ranger is a great machine and under appreciated.
The S-55 first flew on 10 Nov 1949. One would wonder exactly what specifications it was designed built and certified to. I would hope that the system (FAA and manufacturers) became a little more intelligent over the years. By comparison the AS-350 was designed, built and certified in the 1970s in Europe. The AS-350 was brought into the US under the bilateral agreement between the FAA and the European authorities cited by Shawn. It was only recently that the AS-350 was certified for complete manufacture in the US. Up until then all aircraft were manufactured, flown and certified in Europe then disassembled and shipped to Texas where they were reassembled for completion and delivery. The question then is: Could the AS-350 have met the entire spectrum of US certification requirement outlined for helicopters in the 1970s? I hope that Shawn may be able shed more light on this subject. To answer FH1100, YES I believe that the B206L-4 Long Ranger is a great machine and under appreciated.
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Common sense ?
"Equivalent level of safety in lieu of direct compliance"
That's how you certify something which is safe but the rules are wrong - like R66 hydraulics ... which are excellent
Also protectionism is short sighted and leads to worse product and terminally uncompetitive companies which go out of business - many examples (eg Islander etc etc). this regulatory nonsense needs to be fixed asap.
That's how you certify something which is safe but the rules are wrong - like R66 hydraulics ... which are excellent
Also protectionism is short sighted and leads to worse product and terminally uncompetitive companies which go out of business - many examples (eg Islander etc etc). this regulatory nonsense needs to be fixed asap.
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I should like to hear the FAA's take on this matter.
Even better if they would review this matter with a view to requiring Eurocopter to demonstrate (practically) the safety of the AS350's un-boosted flight control capability in all flight modes.
Even better if they would review this matter with a view to requiring Eurocopter to demonstrate (practically) the safety of the AS350's un-boosted flight control capability in all flight modes.
§ 27.397 Limit pilot forces and torques.
(a) Except as provided in paragraph (b) of this section, the limit pilot forces are as follows:
(1) For foot controls, 130 pounds.
(2) For stick controls, 100 pounds fore and aft, and 67 pounds laterally.
(b) For flap, tab, stabilizer, rotor brake, and landing gear operating controls, the follows apply (R=radius in inches):
(1) Crank, wheel, and lever controls, [1+R]/3 × 50 pounds, but not less than 50 pounds nor more than 100 pounds for hand operated controls or 130 pounds for foot operated controls, applied at any angle within 20 degrees of the plane of motion of the control.
(2) Twist controls, 80R inch-pounds.
[Amdt. 27-11, 41 FR 55469, Dec. 20, 1976, as amended by Amdt. 27-40, 66 FR 23538, May 9, 2001]
(a) Except as provided in paragraph (b) of this section, the limit pilot forces are as follows:
(1) For foot controls, 130 pounds.
(2) For stick controls, 100 pounds fore and aft, and 67 pounds laterally.
(b) For flap, tab, stabilizer, rotor brake, and landing gear operating controls, the follows apply (R=radius in inches):
(1) Crank, wheel, and lever controls, [1+R]/3 × 50 pounds, but not less than 50 pounds nor more than 100 pounds for hand operated controls or 130 pounds for foot operated controls, applied at any angle within 20 degrees of the plane of motion of the control.
(2) Twist controls, 80R inch-pounds.
[Amdt. 27-11, 41 FR 55469, Dec. 20, 1976, as amended by Amdt. 27-40, 66 FR 23538, May 9, 2001]
This stuff is probably over 40 years old. It is addressed on some of the later models.
But hey -
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