An overview of how to properly perform the hydraulic tests in the AS350 Click Subscribe to be notified of future EuroSafety Videos. www.eurosafety.us training@eurosafety.us
Excellent Video! Thanks! Just one question, in the manual (PMV) it is written: "Collective and cyclic controls... . Hands on. .Move the cyclic control 2 or 3 times on each axis (+/- 10% of travel) and check for accumulator hydraulic assistance on pitch and roll ( no control loads). Check that forces are felt on the pedals ."HYD TEST"(TEST HYDR) pushbutton... OFF: set in up position. .Warning panel...................... Check HYD light goes off.". So, this force felt on the pedals means that I have to check the course as you did? I just feel it under my feet when I push HYD TEST. However, when I cut the Hyd off, I check the pedals travel. "Yaw pedals force should stay low (yaw load compensator effect)."
When you do the accumulator check ... as you stated you need to ensure the pedals go stiff... If you do not move the pedals you dont know if they are stiff with yaw load compensator or stiff with no assist. By moving the pedals after HYD test or ACCU test you are ensuring the resistance is more then after cut off check. Does that answer your question?
@@EUROSAFETYTRAINING Yes, it does. Thanks for your help. I think that is a matter of how far the pedals must be pressed to feel any kind of stiffness. Greetings from Brazil.
Hey Glen. Thank you for the video. An other quick question. The way I understand it when we dump the hydraulics via the collective switch, if the cyclic is not centred there will be some movement in the cyclic controls back to level the disk. The way this was explained to me, it's due to the starflex springing everything back to centre. There maybe some movement back and forth as one servo might fully discharge ever so slightly before the other. Is this correct? Academically speaking, does this mean that when on the ground a pilot can confirm that what they percieve as centre can be confirmed by activating the switch and seeing if the cyclic has deviated from that position? Additionally on some company checklists I noticed that the HYD check is done at Flight RPM. Which to me seems dangerous in the unlikely event something happens to the collective lock, (or the still unlikely, but much more likely event that the pilot does something stupid like habitually or accidentally unlocking the collective ahead of time). As I understand it, the collective will jump. Again it's the starflex that's yanking the pitch up. The way it has been explained to me, it's not enough to become airbourne but maybe enough to get light on the skids and begin to yaw whilst on the ground. Potentially leading to a dynamic rollover or accessing the hidden tail-rotor hedge-trim service function. My company checklist says to do it at 70% (FX2). Do you have any input on this one way or an other?
There is a lot to unpack in your question.... it somewhat requires thousands of more words but I will somewhat try to remain brief....if I miss anything please let me know. Lets go backwards through your questions. Some checklist have full flight rpm for the hydraulic check because thats the way we did it for the majority of the AS350 history. The factory changed it (lawyers changed it) after there were enough helicopters that had flipped over because the pilot was not guarding the collective after activating the switch on the collective. What happens when you engage the hydraulic cutoff switch is the solenoid valves on the main servos open so the pressure going to them passes by and the accumulators empty. Since the Spherical thrust bearings on your rotorhead are manufactured with a pitch in them and the servos are no longer holding that negative pitch in and the rubber in the bearing untwists to static position. This is the reason the collective moves upwards. Over the years when we did the test at flight rpm I have had many many collectives unlock on me due to the locking strip not being adjusted properly. I have always had my hand on the collective and its easy to stop it from going to higher pitch angle. The overall thought on the test being done at idle vs flight was that you get a better test at flight but its "safer" doing the test idle (most things like this is to deal with the lowest common denominator of pilot). Regarding the question about cyclic centering. Yes after you stop the hydraulic fluid from going into the servo (opening the solenoid valve) the servos are not holding an twist in the spherical thrust bearing, so the rubber untwists (takes alot of force to produce that twist). All bearings untwisted is center cyclic (now technically with the collective in the locked lowered position there is a negative twist in, but they are all the same amount of twist so go to that centered position). If the cyclic is moving in that position it does not mean the cyclic has not fully discharged, in fact that is completely contradictory to the operation of the system. There are many reasons the cyclic could slightly move.... Dunlop servos dont have locking pins on the roll servos, the bearings could be worn in the mixing unit, the rotor system could be out of track... etc.
Thanks for the videos...really great stuff. Quick question for you if you have a minute...I have definitely experienced this movement to the left upon system recharging. However, today I experienced movement to the left when initially doing the isolation check (cyclic moves hard left when turning the collective switch OFF, then after a brief moment the cyclic returns to center). I am used to occasionally experiencing the movement when switching the system back on, but never have experienced it when switching the system off. Is this normal behavior in your experience? Thanks again for any thoughts.
If i understand correctly... when you perform the isolation check the cyclic does not center but rather moves past center to the left and then moves on its own to center? The cyclic has a tendency to center when the isolation switch is engaged, if you are not in center the cyclic will move there. I assume its not a dangerous amount to the left? When you turn the system back on after isolation check its is common for the the cyclic to move to left as the left roll servo is the last to get energized and release the locking pin. But what you are saying is that it does the same thing at the beginning of isolation check. I would assume in this scenario that the main servo solenoid valves are not opening simultaneously. perhaps one is "sticky"
@@EUROSAFETYTRAINING Thanks for the reply. Yes...the cyclic moves at the beginning of the isolation check...immediately upon turning the collective HYD switch off, the cylic jerks hard over to the left side, and then after a brief moment it returns to center. In the past I have definitely experienced the movement upon recharging the system, but had never experienced it upon discharging the system. Will look into a sticky solenoid valve as the culprit. Maybe I can convince my mechanic to swap some to see if the direction changes. Thanks again. Cheers.
Excellent Video! Thanks! Just one question, in the manual (PMV) it is written: "Collective and cyclic controls... . Hands on. .Move the cyclic control 2 or 3 times on each axis (+/- 10% of travel) and check for accumulator hydraulic assistance on pitch and roll ( no control loads). Check that forces are felt on the pedals ."HYD TEST"(TEST HYDR) pushbutton... OFF: set in up position. .Warning panel...................... Check HYD light goes off.". So, this force felt on the pedals means that I have to check the course as you did? I just feel it under my feet when I push HYD TEST. However, when I cut the Hyd off, I check the pedals travel. "Yaw pedals force should stay low (yaw load compensator effect)."
When you do the accumulator check ... as you stated you need to ensure the pedals go stiff... If you do not move the pedals you dont know if they are stiff with yaw load compensator or stiff with no assist. By moving the pedals after HYD test or ACCU test you are ensuring the resistance is more then after cut off check. Does that answer your question?
@@EUROSAFETYTRAINING Yes, it does. Thanks for your help. I think that is a matter of how far the pedals must be pressed to feel any kind of stiffness. Greetings from Brazil.
Hi Glen, Thanks for the video! Jim.
You bet
Hi Jim!
Hey Glen. Thank you for the video. An other quick question. The way I understand it when we dump the hydraulics via the collective switch, if the cyclic is not centred there will be some movement in the cyclic controls back to level the disk. The way this was explained to me, it's due to the starflex springing everything back to centre. There maybe some movement back and forth as one servo might fully discharge ever so slightly before the other. Is this correct? Academically speaking, does this mean that when on the ground a pilot can confirm that what they percieve as centre can be confirmed by activating the switch and seeing if the cyclic has deviated from that position?
Additionally on some company checklists I noticed that the HYD check is done at Flight RPM. Which to me seems dangerous in the unlikely event something happens to the collective lock, (or the still unlikely, but much more likely event that the pilot does something stupid like habitually or accidentally unlocking the collective ahead of time). As I understand it, the collective will jump. Again it's the starflex that's yanking the pitch up. The way it has been explained to me, it's not enough to become airbourne but maybe enough to get light on the skids and begin to yaw whilst on the ground. Potentially leading to a dynamic rollover or accessing the hidden tail-rotor hedge-trim service function. My company checklist says to do it at 70% (FX2). Do you have any input on this one way or an other?
There is a lot to unpack in your question.... it somewhat requires thousands of more words but I will somewhat try to remain brief....if I miss anything please let me know. Lets go backwards through your questions. Some checklist have full flight rpm for the hydraulic check because thats the way we did it for the majority of the AS350 history. The factory changed it (lawyers changed it) after there were enough helicopters that had flipped over because the pilot was not guarding the collective after activating the switch on the collective. What happens when you engage the hydraulic cutoff switch is the solenoid valves on the main servos open so the pressure going to them passes by and the accumulators empty. Since the Spherical thrust bearings on your rotorhead are manufactured with a pitch in them and the servos are no longer holding that negative pitch in and the rubber in the bearing untwists to static position. This is the reason the collective moves upwards. Over the years when we did the test at flight rpm I have had many many collectives unlock on me due to the locking strip not being adjusted properly. I have always had my hand on the collective and its easy to stop it from going to higher pitch angle. The overall thought on the test being done at idle vs flight was that you get a better test at flight but its "safer" doing the test idle (most things like this is to deal with the lowest common denominator of pilot).
Regarding the question about cyclic centering. Yes after you stop the hydraulic fluid from going into the servo (opening the solenoid valve) the servos are not holding an twist in the spherical thrust bearing, so the rubber untwists (takes alot of force to produce that twist). All bearings untwisted is center cyclic (now technically with the collective in the locked lowered position there is a negative twist in, but they are all the same amount of twist so go to that centered position). If the cyclic is moving in that position it does not mean the cyclic has not fully discharged, in fact that is completely contradictory to the operation of the system. There are many reasons the cyclic could slightly move.... Dunlop servos dont have locking pins on the roll servos, the bearings could be worn in the mixing unit, the rotor system could be out of track... etc.
Thanks for the videos...really great stuff. Quick question for you if you have a minute...I have definitely experienced this movement to the left upon system recharging. However, today I experienced movement to the left when initially doing the isolation check (cyclic moves hard left when turning the collective switch OFF, then after a brief moment the cyclic returns to center). I am used to occasionally experiencing the movement when switching the system back on, but never have experienced it when switching the system off. Is this normal behavior in your experience? Thanks again for any thoughts.
If i understand correctly... when you perform the isolation check the cyclic does not center but rather moves past center to the left and then moves on its own to center? The cyclic has a tendency to center when the isolation switch is engaged, if you are not in center the cyclic will move there. I assume its not a dangerous amount to the left? When you turn the system back on after isolation check its is common for the the cyclic to move to left as the left roll servo is the last to get energized and release the locking pin. But what you are saying is that it does the same thing at the beginning of isolation check. I would assume in this scenario that the main servo solenoid valves are not opening simultaneously. perhaps one is "sticky"
@@EUROSAFETYTRAINING Thanks for the reply. Yes...the cyclic moves at the beginning of the isolation check...immediately upon turning the collective HYD switch off, the cylic jerks hard over to the left side, and then after a brief moment it returns to center. In the past I have definitely experienced the movement upon recharging the system, but had never experienced it upon discharging the system. Will look into a sticky solenoid valve as the culprit. Maybe I can convince my mechanic to swap some to see if the direction changes. Thanks again. Cheers.
thanks
No problem
The HYD test button, it that the Accu TST button?
Yes, they just relabeled the button or switch
@@EUROSAFETYTRAININGOk, thank you, and for for the videos. Great learning tool, they are helping me alot since I can come to America.
I am glad you find them useful
@@EUROSAFETYTRAINING obviously ment....*can't come to America.
how do u guys connect/ record audio from headset to the youtube video?
I have a special cord that plugs into gopro
In event total failure electric in flight can i actívate hyd test ?
no, the solenoid valves need electricity to work
@@EUROSAFETYTRAINING thanks Nice Information
Do you have an explanation why the idle RPMs drop slightly when cutting of the hydraulics with the switch on the collective?
The should not happen. Can you hear it change? If you just have an indication change without rotor change its a electrical issue
Happens on B3e. Very small, like only a few RPM but repeatable. And I can hear it.
👏🏼👏🏼
R22 life