Great explanation, I can “see” it as I’m flying now. You have given me a much better understanding of the system. This is very similar to the way I learnt the FCU.
In the event of a propeller overspeed not controlled by the propeller overspeed governor (oil governor), the flyweights in the propeller governor move outward and opens the Py air passage. Py bleeds into the reduction gearbox limiting the fuel supply to the engine. This prevents the propeller/power turbines from accelerating beyond 106 percent rpm.
This is a very good video. I am putting together a PT6 class and was attempting to make some sort of crude animation. There is no way I can do a better job. There are few details here that could be improved if you have the time and energy. The speeder spring "hat" in your animation is constantly in contact with the Py bleed activating lever (its the Nf or fuel topping function of the Constant Speed Unit). During flight, the hat comes in contact with the Py activating lever at 6% over prop selected RPM ( so at cruise with 76% selected, the Nf is activated at 82%). So at under, on or less than 6% overspeed, the hat should not touch the Py bleed lever. This is the fuel side prop over speed protection and is the only "communication" between the prop/power section and the gas generator (free turbine). Since I am here, in full reverse the position of the Py activating lever is re set or lowered. This assures that the pilot valve always remains at under speed condition and that only the Beta valve controls the oil flow. The re set is set at 91%, with the prop gov set at 96% (props full forward). So in full reverse, Nf performs RPM limiting function. The other improvement would be with the Beta lever and the Beta valve movement. The Beta lever has three connections with two inputs. At the prop it is connected to the carbon block which rides in the slip ring. The slip ring translates blade angle at low power settings on approach and then through all ground taxi operations. In flight at higher blade angles, there is a free movement of the propeller piston and the slip ring remains stationary. As power is reduced, blades go towards fine pitch and at the Prime Blade Angle setting (ground rigging by increasing the Np or prop RPM to 77%, the resulting Torque is compared to the prime blade angle chart and adjusted at the prop) slip ring moves forward. This motion through the carbon block and beta lever pulls the Beta valve out, blocking the oil flow. There is actually a small amount of oil flow as there is a constant bleed of oil in the transfer collar. At this point nothing happens with no changes in power lever position. If the power lever is moved further back, the other end of the Beta lever is pulled back. Since the carbon block is fixed in the slip ring (momentarily), this movement also pushes the Beta valve in. The Beta valve now sends more oil to the prop, prop piston and slip ring move forward, lower blade angle is obtained. Beta valve is also re positioned forward blocking the oil flow. A new blade angle is achieved, and will remain until the power lever is moved again. So simply put, the Beta valve responds to power lever and slip ring position, it acts as a 'power steering". It would be awesome if you could capture that relationship, as most pilots don't understand this. The shut off solenoid in a Twin Otter installation is part of the Beta Backup System. As the aircraft was co developed with the then new PT6, there was a concern for in flight prop reversal. This system uses slip ring micro switches to determine 9 or less degrees of blade angle. It this occurs in flight (per power lever idle gate micto switch, closed in flight) the solenoid is activated. This system is prone to prop mounted micro switches shorts and really causes more issues than what it was trying to prevent (especially with seaplanes). The new 400 series no longer utilizes it and I don't know of any other PT6 equipped aircraft with one installed. Ok, sorry for such a long reply. Please don't take it as a criticism. Really enjoyed the video. Thank you
@Pawel Wolski thank you for the comprehensive comment. When I get the energy and motivation I'll revisit this video and will update it. Thank you for educating me further on the PT6 governor.
Hi Roddy, woderful vedio! but, i think if it was in the max.reverse, and then push the thottle from the max.reverse to the idle, i think the pitch of the propeller would not be changed, cause the oil has been stopped by the BETA valve, what do you think?
林剑 In the Beta Mode, I.e on the ground at low RPM, the Power Lever controls the beta valve. By moving the power lever from max reverse to idle it would stop the flow of oil but the action of the counterweights on the propeller blades would cause the blades to move back to the flight idle position.
Thanks. however, as the propeller blades move to the flight idle position, the oil in the propeller should be sumpped to the oil tank. but, cause the oil has been stopped by the BETA valve, it couldnot be sumpped to the oil tank, the pitch of the propeller could not be changed?
In the BETA mode the govenor flyweights are in a collapsed state, i.e. the pilot valve is down. The oil can seep back to the sump this way. It's not very clear from my illustrations but that's how the oil gets back to the tank.
Hi, Would you have more instructional videos on other systems? (Fuel, oil, etc) We have a small fleet of 4 KingAir 350 ER aircraft and I'd like to show this videos to my mechanics. Thanks
No "Systems" videos yet, but as coincidence would have it I've been asked to do some. Fuel / Hydraulics / Landing Gear would be some of the areas I'll probably look into.
Great explanation, I can “see” it as I’m flying now. You have given me a much better understanding of the system. This is very similar to the way I learnt the FCU.
Thank you sir. This video has helped me understand the pt6 more.
I'm pretty sure the lock pitch solenoid produces a hydraulic lock on the prop, thus "pitch locking" the blades in their current position.
That was great Man! Keep it up! Really appreciate the efforts you put into this video!
this is amazing thank you very much
Excellent. Thank you.
FCU next please!!!
What is the purpose of the Py Air on the Propeller Governor?
In the event of a propeller overspeed not controlled by the propeller overspeed governor (oil governor), the flyweights in the propeller governor move outward and opens the Py air passage. Py bleeds into the reduction gearbox limiting the fuel supply to the engine. This prevents the propeller/power turbines from
accelerating beyond 106 percent rpm.
So are you saying the propeller governor is no longer operating normally so you’re using a reduction in fuel to “manage” rpm?
This is a very good video. I am putting together a PT6 class and was attempting to make some sort of crude animation. There is no way I can do a better job. There are few details here that could be improved if you have the time and energy.
The speeder spring "hat" in your animation is constantly in contact with the Py bleed activating lever (its the Nf or fuel topping function of the Constant Speed Unit). During flight, the hat comes in contact with the Py activating lever at 6% over prop selected RPM ( so at cruise with 76% selected, the Nf is activated at 82%). So at under, on or less than 6% overspeed, the hat should not touch the Py bleed lever. This is the fuel side prop over speed protection and is the only "communication" between the prop/power section and the gas generator (free turbine). Since I am here, in full reverse the position of the Py activating lever is re set or lowered. This assures that the pilot valve always remains at under speed condition and that only the Beta valve controls the oil flow. The re set is set at 91%, with the prop gov set at 96% (props full forward). So in full reverse, Nf performs RPM limiting function.
The other improvement would be with the Beta lever and the Beta valve movement. The Beta lever has three connections with two inputs. At the prop it is connected to the carbon block which rides in the slip ring. The slip ring translates blade angle at low power settings on approach and then through all ground taxi operations. In flight at higher blade angles, there is a free movement of the propeller piston and the slip ring remains stationary. As power is reduced, blades go towards fine pitch and at the Prime Blade Angle setting (ground rigging by increasing the Np or prop RPM to 77%, the resulting Torque is compared to the prime blade angle chart and adjusted at the prop) slip ring moves forward. This motion through the carbon block and beta lever pulls the Beta valve out, blocking the oil flow. There is actually a small amount of oil flow as there is a constant bleed of oil in the transfer collar. At this point nothing happens with no changes in power lever position. If the power lever is moved further back, the other end of the Beta lever is pulled back. Since the carbon block is fixed in the slip ring (momentarily), this movement also pushes the Beta valve in. The Beta valve now sends more oil to the prop, prop piston and slip ring move forward, lower blade angle is obtained. Beta valve is also re positioned forward blocking the oil flow. A new blade angle is achieved, and will remain until the power lever is moved again. So simply put, the Beta valve responds to power lever and slip ring position, it acts as a 'power steering". It would be awesome if you could capture that relationship, as most pilots don't understand this.
The shut off solenoid in a Twin Otter installation is part of the Beta Backup System. As the aircraft was co developed with the then new PT6, there was a concern for in flight prop reversal. This system uses slip ring micro switches to determine 9 or less degrees of blade angle. It this occurs in flight (per power lever idle gate micto switch, closed in flight) the solenoid is activated. This system is prone to prop mounted micro switches shorts and really causes more issues than what it was trying to prevent (especially with seaplanes). The new 400 series no longer utilizes it and I don't know of any other PT6 equipped aircraft with one installed.
Ok, sorry for such a long reply. Please don't take it as a criticism. Really enjoyed the video. Thank you
@Pawel Wolski thank you for the comprehensive comment. When I get the energy and motivation I'll revisit this video and will update it. Thank you for educating me further on the PT6 governor.
Nice explanation.
Hi Roddy, woderful vedio! but, i think if it was in the max.reverse, and then push the thottle from the max.reverse to the idle, i think the pitch of the propeller would not be changed, cause the oil has been stopped by the BETA valve, what do you think?
林剑 In the Beta Mode, I.e on the ground at low RPM, the Power Lever controls the beta valve. By moving the power lever from max reverse to idle it would stop the flow of oil but the action of the counterweights on the propeller blades would cause the blades to move back to the flight idle position.
Thanks. however, as the propeller blades move to the flight idle position, the oil in the propeller should be sumpped to the oil tank. but, cause the oil has been stopped by the BETA valve, it couldnot be sumpped to the oil tank, the pitch of the propeller could not be changed?
In the BETA mode the govenor flyweights are in a collapsed state, i.e. the pilot valve is down. The oil can seep back to the sump this way. It's not very clear from my illustrations but that's how the oil gets back to the tank.
Got it. Thank you so much!!!
I would give it a 6.5.
Please Can you make a video on turpoprop controls as well
The video is not visible. Please send me another link or try to fix it. thanks
Hi, Would you have more instructional videos on other systems? (Fuel, oil, etc) We have a small fleet of 4 KingAir 350 ER aircraft and I'd like to show this videos to my mechanics. Thanks
No "Systems" videos yet, but as coincidence would have it I've been asked to do some. Fuel / Hydraulics / Landing Gear would be some of the areas I'll probably look into.
Ohh ok,Thanks, I'll be waiting for them, the propeller-governor one is just superb!! Greetings from Beautiful Baja Mexico!!
😍😍🙏🙏🙏🙏🙏