Hobart accident
Is this a similar situation? https://www.liveleak.com/view?i=fb8_1511190190
This looks more like a tail rotor (control) failure.
Bears some similarity to this. https://www.youtube.com/watch?v=f3yncJ2TF80
You would have thought that the high loads on all three controls would have been a clue.
Not sure how you could mistake hydraulic failure with TR failure I agree! As Crab says surely the control loads would be obvious . There have now been a shed load of Hyd off accidents in the AS350 , some with very competent pilots , which makes me think something else may be happening during these training sessions. Are they letting the reservoirs deplete and putting hyd back on before they have filled ..or similar ?? Just asking ...
You would have thought that the high loads on all three controls would have been a clue.
Not sure how you could mistake hydraulic failure with TR failure I agree! As Crab says surely the control loads would be obvious.
HYD Pump failure will remove assistance from the TR servo immediately yet the accumulators on the MR servo's would result in no immediate change.
Of course you would have a HYD caption and HORN blaring. If you didn't notice the caption and were a bit slow on the uptake as to what is going on in
the first instance you could suspect a TR control failure as the pedals would be pretty stiff and thats all. (AS 350 B & BA sans TR accumulator)
Continuing on the MR accumulators can deplete rapidly and asymmetrically which makes for more fun and if you are slow as was the case here very
interesting especially if you have further effect of yaw rate from stiff pedals.
On the 350 if you have a HYD failure you need to get the aircraft sorted, slowed down if necessary and then turn the HYD OFF on the collective. This will dump the
accumulators and silence the HORN.
Some people get confused with the use and purpose of the HYD TEST switch. Reason being it is the only one they actually use regularly during pre-takeoff checks
and they assume it is the HYD OFF which it isn't. Correct use of the HYD TEST is imperative.
To all intents and purposes to be sure the HYD TEST switch should never be used in flight operationally. It has a training function in flight but that needs careful consideration.
extract form EASA EXPERT DEPARTMENT / CERTIFICATION DIRECTORATE - OEB Report -
Simulated Hydraulic failure
(Except EC 130 B4 & T2 and AS 350 B3 equipped with the optional dual hydraulic system):
- In steady flight conditions, simulate the hydraulic failure by depressing HYD TEST push button on the System Control Unit (Honeywell or SCU console panel):
HYD + Gong sounds while the student adjusts speed to obtain between 40 and 60 Kt.
CAUTION: The Instructor must ensure that the trainee adjusts the speed and attitude prior to isolating the hydraulics.
- Once safety speed is set, and prior to activating the hydraulic isolation switch reset HYD TEST pushbutton to restore hydraulic pressure in tail rotor accumulator (except for AS 350 B3e, B and BA).
- If necessary during the training exercise, hydraulic assistance can be recovered immediately by setting the HYD TEST push button to the UP position or by resetting the hydraulic cut off switch to ON.
- If the HYD TEST pushbutton is not reset on the control panel, no hydraulic assistance can be restored. Before hydraulic isolation with the switch on the collective lever, do not forget to reset the HYD pushbutton on the console.
- Do not let the student attempt hover flight or low speed maneuver, as the intensity and direction of the control feedback force will change rapidly. This will result in a loss of control
On previous versions of AS350 equipped with a HONEYWELL console control, do not silence the HORN by using the HORN switch.
The HORN will be silenced when the pilot selects the hydraulic cut-off switch to off.
If the pilot uses the HORN switch to silence the HORN before using the hydraulic cut-off switch, this crucial step could be forgotten. This could then result in significant unbalanced lateral cyclic feedback forces, especially at low speed, if one of the lateral accumulators depletes before the other one.
In addition, de-activating the HORN using the HORN switch, makes it unavailable to warn the pilot of low or high rotor RPM.
Pay attention to the following:
- Hydraulic accumulators gives energy during approximately 20 seconds, in proportion of controls movements, so reduce to safety speed in this time frame,
- Anticipate to perform a shallow approach,
- Perform a running landing,
- Hover flight or any low speed maneuver must be avoided,
- Keep in mind that higher All Up Weight increase the risk of aircraft loss of control at low speed,
- The statistics show that failure to strictly comply with the procedure consequently increases the risk level.
Notes:
Left hand collective lever is not equipped with “HYD” switch,
- To be well prepared, brief your Trainee for setting the collective lever HYD switch to on, if necessary.
- If the Instructor decides to take over the controls, he must plan to continue the flight up to the landing
without the hydraulic assistance.
- CAUTION: when hydraulic pressure is restored in flight, the forces disappear which can lead to an abrupt left roll movement.
- Anticipate the power application to avoid induced increase in nose-up attitude.
(Except EC 130 B4 & T2 and AS 350 B3 equipped with the optional dual hydraulic system):
- In steady flight conditions, simulate the hydraulic failure by depressing HYD TEST push button on the System Control Unit (Honeywell or SCU console panel):
HYD + Gong sounds while the student adjusts speed to obtain between 40 and 60 Kt.
CAUTION: The Instructor must ensure that the trainee adjusts the speed and attitude prior to isolating the hydraulics.
- Once safety speed is set, and prior to activating the hydraulic isolation switch reset HYD TEST pushbutton to restore hydraulic pressure in tail rotor accumulator (except for AS 350 B3e, B and BA).
- If necessary during the training exercise, hydraulic assistance can be recovered immediately by setting the HYD TEST push button to the UP position or by resetting the hydraulic cut off switch to ON.
- If the HYD TEST pushbutton is not reset on the control panel, no hydraulic assistance can be restored. Before hydraulic isolation with the switch on the collective lever, do not forget to reset the HYD pushbutton on the console.
- Do not let the student attempt hover flight or low speed maneuver, as the intensity and direction of the control feedback force will change rapidly. This will result in a loss of control
On previous versions of AS350 equipped with a HONEYWELL console control, do not silence the HORN by using the HORN switch.
The HORN will be silenced when the pilot selects the hydraulic cut-off switch to off.
If the pilot uses the HORN switch to silence the HORN before using the hydraulic cut-off switch, this crucial step could be forgotten. This could then result in significant unbalanced lateral cyclic feedback forces, especially at low speed, if one of the lateral accumulators depletes before the other one.
In addition, de-activating the HORN using the HORN switch, makes it unavailable to warn the pilot of low or high rotor RPM.
Pay attention to the following:
- Hydraulic accumulators gives energy during approximately 20 seconds, in proportion of controls movements, so reduce to safety speed in this time frame,
- Anticipate to perform a shallow approach,
- Perform a running landing,
- Hover flight or any low speed maneuver must be avoided,
- Keep in mind that higher All Up Weight increase the risk of aircraft loss of control at low speed,
- The statistics show that failure to strictly comply with the procedure consequently increases the risk level.
Notes:
Left hand collective lever is not equipped with “HYD” switch,
- To be well prepared, brief your Trainee for setting the collective lever HYD switch to on, if necessary.
- If the Instructor decides to take over the controls, he must plan to continue the flight up to the landing
without the hydraulic assistance.
- CAUTION: when hydraulic pressure is restored in flight, the forces disappear which can lead to an abrupt left roll movement.
- Anticipate the power application to avoid induced increase in nose-up attitude.
Last edited by RVDT; 20th Dec 2017 at 20:04.
RVDT,
Right on the money. But the reference to the B3e in your training notes is not correct. That info must be prior to the retrofitting of the load compensator after the accidents with the Chinese weights (what a brilliant idea
)
The New York and Hobart machines both were BA's.....
Right on the money. But the reference to the B3e in your training notes is not correct. That info must be prior to the retrofitting of the load compensator after the accidents with the Chinese weights (what a brilliant idea
) The New York and Hobart machines both were BA's.....
Nubian,
I think it is the current OEB Report but probably before the B3e retro. dtd Revision 4 : 06 08 2012 probably now covered by OSD info held by the manufacturer.
It was my comment to add that B and BA don't have a compensator.
The "single family" goes in order of release B,D,B1,B2,BA,BB,B3,B4,B2 VEMD,B3+,B3e and finally T2.
Dual HYD models is another kettle of fish with their own little traps!
I think it is the current OEB Report but probably before the B3e retro. dtd Revision 4 : 06 08 2012 probably now covered by OSD info held by the manufacturer.
It was my comment to add that B and BA don't have a compensator.
The "single family" goes in order of release B,D,B1,B2,BA,BB,B3,B4,B2 VEMD,B3+,B3e and finally T2.
Dual HYD models is another kettle of fish with their own little traps!
All that makes for scarey reading for someone not familiar with AS350. I'm surprised there aren't more loss of control accidents with hydraulics off training in this type.
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First training flight at a pretty decent company whom I worked for when I first went to Canada back in 2006.
It was a B1 Squirrel.
When we went to do a HYD off landing, the check and training guy said he wanted me to touch down on the piano keys. Ok I said. Thinking thats where he wanted me to run it on from. A target to aim for.
On short finals the conversation went like this.
Him "your going to overshoot"
me "No I'm not, I'm going to touch down on the piano keys and run it on" (like he asked)
Him "but your going to overshoot the PK"
me" I will as I'm running it on"
Him " you can't run it on, there is nowhere to run it on in the tundra, you need to hover first"
OK, so at this point I realised just what he wanted. For me to hover over the keys and land it with no forward speed.
So doing what the C and T guy asked, I started to slow down to try and come to a hover over the spot. I should have gone round at this point.
As I came to a hover, I was still tail low and was struggling to level the ship.
Next thing we are going backwards. With both of us now on the controls it was a fight between each other and the machine.
Next we spin 180deg and end up being nose low towards the ground. I tried to get had back by hitting the accumulator dump switch but nothing occurred!
Finally after a wild ride he hit the hyd test switch and we got hyd back!
A few wobbles later and everything was under control.
It was pretty bloody close to being a disaster.
He didnt say much at all.
From now on i ensure this doesn't happen to me again during my check rides, and also when I do C and T myself, the whole event is discussed prior and the hyd test is reset before the accumulator is dumped.
Scary ****
It was a B1 Squirrel.
When we went to do a HYD off landing, the check and training guy said he wanted me to touch down on the piano keys. Ok I said. Thinking thats where he wanted me to run it on from. A target to aim for.
On short finals the conversation went like this.
Him "your going to overshoot"
me "No I'm not, I'm going to touch down on the piano keys and run it on" (like he asked)
Him "but your going to overshoot the PK"
me" I will as I'm running it on"
Him " you can't run it on, there is nowhere to run it on in the tundra, you need to hover first"
OK, so at this point I realised just what he wanted. For me to hover over the keys and land it with no forward speed.
So doing what the C and T guy asked, I started to slow down to try and come to a hover over the spot. I should have gone round at this point.
As I came to a hover, I was still tail low and was struggling to level the ship.
Next thing we are going backwards. With both of us now on the controls it was a fight between each other and the machine.
Next we spin 180deg and end up being nose low towards the ground. I tried to get had back by hitting the accumulator dump switch but nothing occurred!
Finally after a wild ride he hit the hyd test switch and we got hyd back!
A few wobbles later and everything was under control.
It was pretty bloody close to being a disaster.
He didnt say much at all.
From now on i ensure this doesn't happen to me again during my check rides, and also when I do C and T myself, the whole event is discussed prior and the hyd test is reset before the accumulator is dumped.
Scary ****
Reading all these posts one thing stands out as if it had sirens blaring, a high vis paint scheme and flashing strobe lights all over it......the design, layout, and complexity of the systems, procedures, and mis-matched control forces are flat screwed up!
All that sets Pilots up for failure it seems to me.
At least the series seems to retain the spinning bits unlike one of its big brothers!
All that sets Pilots up for failure it seems to me.
At least the series seems to retain the spinning bits unlike one of its big brothers!
And additionally there are the machines with yaw compensators -
The scenario - loss of hydraulics - pump belt has broken or pump puked.
People go - turn off hydraulics - inadvertently or ignorantly hit the HYD TEST.
Due to the requirement to unload the compensator after shutdown - pushing the switch will unload the compensator - which you do not need in flight and
HYD OFF will NOT unload the compensator. HYD OFF or HYD failed AND HYD TEST will dump the TR compensator hence the instructions above.
Reset HYD TEST then HYD OFF to recharge the compensator when training.
The reason for the compensator is that as they needed more thrust from the TR with the increase in gross weight they added a tab to the trailing edge.
Uncompensated machines have the same TR but at the lower gross weight it is manageable.
Heavier machines - you will lift yourself out of the seat before you get enough pedal fighting against the tab.
Back to the issue of the now dumped compensator - you ain't getting it back because you have no HYD pump.
More than a few have ended up on their side because of this and some very high time guys that I know personally.
DUAL HYD machines also have the ability to get airborne without the TR compensator charged and no pressure as a few have found that are no longer with us.
The preflight test has moved to post flight to try and address the issue on DUAL machines.
You need a very clear understanding of the issues on this type.
The scenario - loss of hydraulics - pump belt has broken or pump puked.
People go - turn off hydraulics - inadvertently or ignorantly hit the HYD TEST.
Due to the requirement to unload the compensator after shutdown - pushing the switch will unload the compensator - which you do not need in flight and
HYD OFF will NOT unload the compensator. HYD OFF or HYD failed AND HYD TEST will dump the TR compensator hence the instructions above.
Reset HYD TEST then HYD OFF to recharge the compensator when training.
The reason for the compensator is that as they needed more thrust from the TR with the increase in gross weight they added a tab to the trailing edge.
Uncompensated machines have the same TR but at the lower gross weight it is manageable.
Heavier machines - you will lift yourself out of the seat before you get enough pedal fighting against the tab.
Back to the issue of the now dumped compensator - you ain't getting it back because you have no HYD pump.
More than a few have ended up on their side because of this and some very high time guys that I know personally.
DUAL HYD machines also have the ability to get airborne without the TR compensator charged and no pressure as a few have found that are no longer with us.
The preflight test has moved to post flight to try and address the issue on DUAL machines.
You need a very clear understanding of the issues on this type.
RVDT
agreed, but only a control issue (stuck pedals) not a TR drive failure which is what was intimated by Nubians comment - hence why I mentioned other control loads.
However the rest of your info is very interesting and, like Gullibell, puts me off the idea of flying the 350. Perhaps an engine or transmission driven pump (directly, rather than via a belt) might have been a better design solution.
the first instance you could suspect a TR control failure as the pedals would be pretty stiff and thats all.
However the rest of your info is very interesting and, like Gullibell, puts me off the idea of flying the 350. Perhaps an engine or transmission driven pump (directly, rather than via a belt) might have been a better design solution.
Originally Posted by [email protected]
...However the rest of your info is very interesting and, like Gullibell, puts me off the idea of flying the 350.
Hughsey,
Ok, it would not be the first time this training procedure has been done incorrectly! The check airman should know this very well before he can do a flight check imho, but some just think they know...... which is not enough.
The other part of your story, seems there was no briefing of the manoeuvre, as to transfer of controls if things go pear shaped. It is not a good scenario if 2 guys wrestle each other HYD off, and to top it off with no load compensator.. Amazing you did not crash, really.
Airbus came out with a mod a while ago addressing the issue with the HYD test button being used incorrectly for training. Post mod, the HYD caption will blink and therefore you get the GONG repeatedly instead of one time as it did pre mod. This is a direct result of training crashes and incidents.
I personally know a pilot which has part of the ''honour'' for this mod to be put in place. That happened due to 2 pilots (none being instructors) being clever, and wanted to use a ferryflight to do some ''training'', and ended up on the side with a brand new machine, with the HYD-test button still depressed.
Crab,
The belts installed now is a different type than the ones that used to fail, which probably came from a Citroen or a Renault in the 70's....
On the DUAL Hyd machines there is a MGB driven pump, but that reduces the TBO of the MGB with 1000 flight hours.
I tried to get had back by hitting the accumulator dump switch but nothing occurred!
Finally after a wild ride he hit the hyd test switch and we got hyd back!
Finally after a wild ride he hit the hyd test switch and we got hyd back!
The other part of your story, seems there was no briefing of the manoeuvre, as to transfer of controls if things go pear shaped. It is not a good scenario if 2 guys wrestle each other HYD off, and to top it off with no load compensator.. Amazing you did not crash, really.
Airbus came out with a mod a while ago addressing the issue with the HYD test button being used incorrectly for training. Post mod, the HYD caption will blink and therefore you get the GONG repeatedly instead of one time as it did pre mod. This is a direct result of training crashes and incidents.
I personally know a pilot which has part of the ''honour'' for this mod to be put in place. That happened due to 2 pilots (none being instructors) being clever, and wanted to use a ferryflight to do some ''training'', and ended up on the side with a brand new machine, with the HYD-test button still depressed.
Crab,
The belts installed now is a different type than the ones that used to fail, which probably came from a Citroen or a Renault in the 70's....
On the DUAL Hyd machines there is a MGB driven pump, but that reduces the TBO of the MGB with 1000 flight hours.
Nobody seems to have mentioned, the hopefully never occurred scenario, where after coming to a hover (first mistake) and struggling “someone” turned the Hydraulics back on.
That might explain a violent maneuver from the hover.
Pure speculation.
That might explain a violent maneuver from the hover.
Pure speculation.
The AS350BA was the Australian Defence Force ab initio helicopter trainer for almost 30 years, as well as being used by the RAN for utility and embarked operations during that time. A fantastic aircraft and extremely reliable, despite all the talk on this forum of engine failures and hydraulic disasters waiting to happen. In fact I am unaware of any actual hydraulics or engine failures during its time in military service. Hydraulics failure was taught as part of the basic syllabus and regularly practiced during the course, and has therefore been successfully handled by students literally thousands of times over 30 years. I don't know of a single instance of an aircraft being damaged while practicing this manoeuvre on pilot's course. The whole "emergency" was relatively easy to handle with proper instruction. Consequently I believe any accidents resulting from real or practice hydraulic failures are more likely a result of poor instruction/technique than poor design.
Mark Six - The Brit Mil have been using it since 1995 as a basic trainer, again with regular hyd off training and again, without (to my knowledge) any incidents so perhaps you are right.