Native Air
Well, if what 407 is correct then there must be some other explanation other than simple loss of hydraulic assistance. The 212 is no problem to approach to hover and land except in the case of the SCAS fitted with SI-65, the collective/yaw interlink, when it is more tricky but not impossible.
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Correct 212Man, there seems to be something in this particular B3 aircraft that made it more difficult to control without boost than the average 350 (B2 or B3).
Each aircraft tends to be slightly different, I recall a few 212's in my day that I really had to stand on those pedals to maintain directional control during practice one-HYD-off landings....others seemed as easy as a 407 or B2...go figure?
Each aircraft tends to be slightly different, I recall a few 212's in my day that I really had to stand on those pedals to maintain directional control during practice one-HYD-off landings....others seemed as easy as a 407 or B2...go figure?
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212man
I conducted the certification program on the AS350 BA when it first flew for the military in Aus. (BA has 355 blades on an AS350B plus some changes to the tail rotor). While control at the point of failure and recovery to landing in the degraded mode is OK throughout most of the CG/AUW envelope, there are parts of the envelope where the forces are extremely high and unpredictable (ie beyond the rated strength of control runs in the yaw axis). Despite us later instrumenting an aircraft and proving the high forces to be well above what the FARs allow, CASA and FAA took no action because they had grandfathered the certification from the DGAC (France). The FAR requires that for a failure mode "anywhere in the envelope", pilot skill and strength to control the failure and subsequently land is not be excessive. This is where interpretation is everything! According to the OEM (hence DGAC), the benign points are somewhere (=anywhere) within the envelope and therefore by testing those and ignoring the bad ones, they meet the FAR! Bottom line is, never try to hover a heavy AS350 with a forward CG. Even maintaining level flight is extremely difficult after about 25-30 minutes due to high forces in the collective.
forget to mention in my previous post. The reason we instrumented the aircraft was because we lost an AS350BA in an accident that sounds almost identical to the Native Air one. Uncontrollable yaw and pitch oscillations ending up on its side after attempting to come to a hover in a degraded hydraulic mode. Despite the lack of CASA action after the results of our testing were passed to them, the military stopped using the AS350 for loadmaster training due to the frequent exposure to high AUW hover operations. Despite OEM assurances about MTBF for the HYD system, we tracked down enough occurances world wide to deem it an uneccessary risk. Native Air just adds one more to the record. Just glad all the crew were OK.
I conducted the certification program on the AS350 BA when it first flew for the military in Aus. (BA has 355 blades on an AS350B plus some changes to the tail rotor). While control at the point of failure and recovery to landing in the degraded mode is OK throughout most of the CG/AUW envelope, there are parts of the envelope where the forces are extremely high and unpredictable (ie beyond the rated strength of control runs in the yaw axis). Despite us later instrumenting an aircraft and proving the high forces to be well above what the FARs allow, CASA and FAA took no action because they had grandfathered the certification from the DGAC (France). The FAR requires that for a failure mode "anywhere in the envelope", pilot skill and strength to control the failure and subsequently land is not be excessive. This is where interpretation is everything! According to the OEM (hence DGAC), the benign points are somewhere (=anywhere) within the envelope and therefore by testing those and ignoring the bad ones, they meet the FAR! Bottom line is, never try to hover a heavy AS350 with a forward CG. Even maintaining level flight is extremely difficult after about 25-30 minutes due to high forces in the collective.
forget to mention in my previous post. The reason we instrumented the aircraft was because we lost an AS350BA in an accident that sounds almost identical to the Native Air one. Uncontrollable yaw and pitch oscillations ending up on its side after attempting to come to a hover in a degraded hydraulic mode. Despite the lack of CASA action after the results of our testing were passed to them, the military stopped using the AS350 for loadmaster training due to the frequent exposure to high AUW hover operations. Despite OEM assurances about MTBF for the HYD system, we tracked down enough occurances world wide to deem it an uneccessary risk. Native Air just adds one more to the record. Just glad all the crew were OK.
Thanks for that; I was genuinly curious and had no idea either way. Cheers.
Sounds simple to me really.
This pilot allowed the aircraft to get too slow. The Astar flight manual allows for a running landing only. Stick to those parameters and its a doddle. The Astar is no worse than any other aircraft (bar the 76...
) without hydraulics. Read the FM, follow the proceedure and accept the run on landing.
This pilot allowed the aircraft to get too slow. The Astar flight manual allows for a running landing only. Stick to those parameters and its a doddle. The Astar is no worse than any other aircraft (bar the 76...
) without hydraulics. Read the FM, follow the proceedure and accept the run on landing.
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southcoast
excellent work on those BA tests - viewed your report a while back.
as I understand your post you are saying that within the C of G envelope, and specifically with a high AUW and forward CG, control forces without hydraulics will be unmanageable (in the hover).
What other C of G situations are dangerous & is it collective force only or both collective and cyclic and why fwd CG vs aft CG (since forward cyclic requires more force than aft cyclic) without hydraulics?
excellent work on those BA tests - viewed your report a while back.
as I understand your post you are saying that within the C of G envelope, and specifically with a high AUW and forward CG, control forces without hydraulics will be unmanageable (in the hover).
What other C of G situations are dangerous & is it collective force only or both collective and cyclic and why fwd CG vs aft CG (since forward cyclic requires more force than aft cyclic) without hydraulics?
" The Astar is no worse than any other aircraft (bar the 76... ) without hydraulics"
Oh really? Do you have experience of a 76 with no TR hydraulics? I would doubt very much that you'd get much response from the pedals. There is no way of simulating it either (maybe FSI do but I would take it with a pinch of salt if they do, having seen their 212/412 TR failure simulation).
I think the reference to "any other a/c " is a bit sweeping; do you mean any other small singles in the same class? Anything bigger than, say, a Bo105 and I think you'll be lucky to be able to move the pedals without assistance (any 105/117 drivers able to comment?) Can't in a 365/155 and certainly not in bigger types still (61/332). 365/155 has a definite advantage in this area though; umpteen square feet of tail surface!
Oh really? Do you have experience of a 76 with no TR hydraulics? I would doubt very much that you'd get much response from the pedals. There is no way of simulating it either (maybe FSI do but I would take it with a pinch of salt if they do, having seen their 212/412 TR failure simulation).
I think the reference to "any other a/c " is a bit sweeping; do you mean any other small singles in the same class? Anything bigger than, say, a Bo105 and I think you'll be lucky to be able to move the pedals without assistance (any 105/117 drivers able to comment?) Can't in a 365/155 and certainly not in bigger types still (61/332). 365/155 has a definite advantage in this area though; umpteen square feet of tail surface!
212,
Many BK117's don't have hydraulic assistance for the T/R, mine is one. Not a problem flying all day, yaw control is lightly loaded, but sometimes needs extreme inputs due to the short couple from the Bo105 tail boom. Putting 117C tail rotor blades makes a huge difference to control authority, but still light forces without any need for hydraulic assistance.
Many BK117's don't have hydraulic assistance for the T/R, mine is one. Not a problem flying all day, yaw control is lightly loaded, but sometimes needs extreme inputs due to the short couple from the Bo105 tail boom. Putting 117C tail rotor blades makes a huge difference to control authority, but still light forces without any need for hydraulic assistance.
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"The instructor simulated a hydraulic system failure by pressing the HYD TEST (hydraulic test) button. When the student pilot began to experience control difficulties, the instructor took over and asked the student to turn the hydraulics back on. The student mistakenly selected the HYD OFF button, by which time the helicopter was uncontrollable in yaw. The instructor managed to reset the HYD TEST button, but hydraulic power was not restored. He was unable to prevent the rotation continuing so elected to place the machine on the ground before the situation worsened. The helicopter rolled onto its side upon touching down. Hydraulic failure is normally simulated in the AS350 series by depressing the HYD TEST button. This depressurises the system, and the three accumulators in the roll and pitch circuits will continue to provide hydraulic assistance long enough for the pilot to reduce speed to the safe operating range of between 40 and 60 knots. Once the accumulator pressure has been exhausted, the aircraft is effectively under manual control, and the pilot will feel significant loads on the controls. The flight manual actions for hydraulic failure are firstly to reduce collective pitch and adjust the airspeed to between 40 and 60 knots, and secondly to operate the HYD OFF switch on the collective lever. This switch serves to eliminate any residual pressure on the servo pistons, minimising the mechanical loads required to move the control linkages. It also cancels the warning horn, which sounds when hydraulic pressure is lost. The B2 model has an additional accumulator in the yaw control circuit. Operating the HYD TEST button depressurises this accumulator immediately, but in the case of an actual hydraulic failure, this accumulator remains pressurised indefinitely (according to the flight manual), when the collective switch is operated and the HYD TEST Button is NOT pushed. Simulating hydraulic failure in the B2 model by using the HYD TEST button will result in control loads being felt immediately in the yaw circuit, with the normal delay in the roll and pitch circuits. There is a note in the emergency section of the flight manual that states: "Do not press the HYD TEST button; this will cause immediate depressurisation of the accumulator and the resulting control loads may be heavy." In this occurrence, when the instructor simulated hydraulic failure by means of the HYD TEST button, the student would have immediately felt control loads though the yaw pedals but normal forces on the cyclic and collective until the accumulator pressures discharged. By the time the latter occurred, he should have had the speed within the recommended range and operated the Hydraulic Cut-Off switch on the collective lever. However, the collective switch was not reset to ON in this case, and the instructor did not reset the HYD TEST button until after control difficulty was experienced. This action did not immediately restore the hydraulic system to its normal operation as the HYD OFF switch was still in the OFF position and the T/R accumulator remained discharged."
This is one area where it can come unglued. Could be entirely unrelated as to what happened in this incident but it is worth putting forward to address the conjecture here!
southcoast sez "there are parts of the envelope where the forces are extremely high and unpredictable (ie beyond the rated strength of control runs in the yaw axis". The contol runs in a 350 don't look much different downstream of the servo, in fact have a look at the size of the bolt at the end of the bellcrank attached to the pitch change mechanism??
Go try an A109E it will lift you out of the seat nearly.
"Uncontrollable yaw and pitch oscillations ending up on its side after attempting to come to a hover in a degraded hydraulic mode" which would be outside the procedures in the RFM no?? Caveat Emptor.
Another area for potential problems is under OR overpressure in the accumulators which has been discussed here before. Underpressure is obvious and overpressure leaves the accumulator with less oil in it.
This is one area where it can come unglued. Could be entirely unrelated as to what happened in this incident but it is worth putting forward to address the conjecture here!
southcoast sez "there are parts of the envelope where the forces are extremely high and unpredictable (ie beyond the rated strength of control runs in the yaw axis". The contol runs in a 350 don't look much different downstream of the servo, in fact have a look at the size of the bolt at the end of the bellcrank attached to the pitch change mechanism??
Go try an A109E it will lift you out of the seat nearly.
"Uncontrollable yaw and pitch oscillations ending up on its side after attempting to come to a hover in a degraded hydraulic mode" which would be outside the procedures in the RFM no?? Caveat Emptor.
Another area for potential problems is under OR overpressure in the accumulators which has been discussed here before. Underpressure is obvious and overpressure leaves the accumulator with less oil in it.
Go try an A109E it will lift you out of the seat nearly
Hyd off (#1 sys) knocks out the yaw in the 109E, and is quite controllable. What was the problem that you allude to?
JB,
The 109E is currently 2850kg MAUW, and is no better or worse than the earlier A or C models. A little twitchy with #1 hyd off, as with many of its ilk, but I wouldn't subscribe to your description "lift you out of your seat nearly".
ISTR the 212 was a bit of a handful with hyd failure, and I do recall that I had to be specifically checked out hyd off when I returned to the North Sea after a fractured femur (I was still using a walking stick
). Someone thought it may be too much strain, in retrospect they were probably right!
The 109E is currently 2850kg MAUW, and is no better or worse than the earlier A or C models. A little twitchy with #1 hyd off, as with many of its ilk, but I wouldn't subscribe to your description "lift you out of your seat nearly".
ISTR the 212 was a bit of a handful with hyd failure, and I do recall that I had to be specifically checked out hyd off when I returned to the North Sea after a fractured femur (I was still using a walking stick
). Someone thought it may be too much strain, in retrospect they were probably right!
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JE,
Sorry, was referring to pedal pressure required not MTOW! There was a little bit of pontification here prior to issuing a HB badge for the side. Grandfather saved the day again though.
Sorry, was referring to pedal pressure required not MTOW! There was a little bit of pontification here prior to issuing a HB badge for the side. Grandfather saved the day again though.
