Very nice video. I will have my guys look at it before ground school. I would like to add few clarifications so your comments mirror values in all the training manuals for the Twin Otter installation. At about 2:25 sec you state: "When the piston is in normal operation", this statement suggests the constant speed operation. As you know the piston does not contact the beta nuts in constant speed range. It would be awesome if you simply moved the piston back and forth without approaching the beta nuts. What you are showing, happens when the prop comes out of feather typically after start or if power is reduced close to idle and prime angle is established. I know that you understand all this, but without good knowledge of this system this part can confuse viewers. Here are the Twin Otter training manuals numbers. All based on rigging, for STOL or our seaplane operations, we like a flat blade angles so all these values would be less, for more prop disking on approach. 21 deg, contact angle, the prop piston makes contact with the beta nuts 17 deg, prime blade angle, beta valve has full control of oil pressure 11 deg, idle, power levers are at the gate. Reduction of blade angle from 17 to 11 is in the approach beta phase (in flight), increase from 11 to 17 happens during initial power application for fast taxi or take off - 15 is full reverse, prop piston at end of it's travel and power levers in full back position. Other aircraft installations might have different values, but the above relationship always exists. Beta range always has contact angle, prime angle, lower idle angle and then progressively zero angle and finally negative reverse angle. Also during taxi, the engine does not produce above idle power, until a negative blade angle is achieved. Again thank you for great video, as this relationship is hard to explain "on paper" without a mock up, I just added few details to tell the entire story. Please don't take this as any sort of criticism. Thx, Pawel
Great video Hal. It really helps me to see the interaction between the piston, beta ring and valve. Very nice. Great success
Very nice video. I will have my guys look at it before ground school. I would like to add few clarifications so your comments mirror values in all the training manuals for the Twin Otter installation.
At about 2:25 sec you state: "When the piston is in normal operation", this statement suggests the constant speed operation. As you know the piston does not contact the beta nuts in constant speed range. It would be awesome if you simply moved the piston back and forth without approaching the beta nuts. What you are showing, happens when the prop comes out of feather typically after start or if power is reduced close to idle and prime angle is established. I know that you understand all this, but without good knowledge of this system this part can confuse viewers.
Here are the Twin Otter training manuals numbers. All based on rigging, for STOL or our seaplane operations, we like a flat blade angles so all these values would be less, for more prop disking on approach.
21 deg, contact angle, the prop piston makes contact with the beta nuts
17 deg, prime blade angle, beta valve has full control of oil pressure
11 deg, idle, power levers are at the gate. Reduction of blade angle from 17 to 11 is in the approach beta phase (in flight), increase from 11 to 17 happens during initial power application for fast taxi or take off
- 15 is full reverse, prop piston at end of it's travel and power levers in full back position.
Other aircraft installations might have different values, but the above relationship always exists. Beta range always has contact angle, prime angle, lower idle angle and then progressively zero angle and finally negative reverse angle. Also during taxi, the engine does not produce above idle power, until a negative blade angle is achieved.
Again thank you for great video, as this relationship is hard to explain "on paper" without a mock up, I just added few details to tell the entire story. Please don't take this as any sort of criticism.
Thx, Pawel
This is really great, please make more videos!
Super informative.
Thank you
good job
Good interested video 😁 I wan to do but never source
No no nuts 😂