To Lu,
I note that you continue to avoid discussion on specific points by diverting discussion. Until you can keep it on track, I do not think you will be able to achieve your stated aim of being able to understand some of the POF discussed on the forum. An example?
You said on the “vote” thread, Page 3 post 5: >> Here is the way I would teach it and actually it is the way I teach it<< and then you went on to describe your method.
In post 7 on the same page, I dissected your statement to show you where your understandings are incorrect and in need of flapping to equality/cyclic feathering understanding.
Your response to that was in post 8 on the same page, and I quote:
>>To: Helmet Fire
I do not teach it that way.<<
Lu, can you not see the contradiction from what you said in post 5? Why do you deflect the discussion to irrelevant details such as wether or not you do/don’t teach it that way rather than try and benefit from the explanations offered? You did not acknowledge that any points were even made.
For example, you have avoided any response to my opening posts on RBS, and on which parts of your understanding are flawed. Even in your new explanation of how you “really” teach it you are mixing concepts. You said:
>>In a retreating blade stall condition the right side of the disc is generating more lift than the left side. It is this differential of lift that causes the disc to raise 90-degrees later and the disc flaps back.<<
This is not true Lu. The disc does not raise at the back, the rear blade is just unable to climb as high as it did in the pre stall condition, creating an apparent lowering of the tip path plane at the rear of the disc. Flap back is a completely different phenomena unrelated to this discussion, rather it is applicable to changing of airspeeds over the disc and flapping to equality/cyclic feathering (see explanation by Arm out the window on gyroscopic thread). This use of incorrect terminology is continued in your repeated reference to pitch instead of Angle of Attack, amongst other things. Unfortunately, the incorrect usage hints at a lack of understanding of application, so you might want to tighten up your terminology, and I am using US terminology here.
You continued by saying: >>However it is not instantaneous [ie the stall] so the disc will become unstable and the lift differential will generate a left rolling moment.<<
As stated in the posts above (that you ignored), the disc does NOT become unstable. The disc cannot be thought of as a solid entity. As pointed out above by ShyT, only sections of an individual blade enter and leave the stalled state during its revolution through the retreating side. Perhaps it is semantics, but I would say that even the individual blade is not “unstable” in this condition. It was bought to your attention in previous posts on this thread that the blade does not suddenly drop, etc (you ignored this too).
Lastly, you finish your explanation with:
>>Shortly thereafter the rolling moment will manifest itself by causing the disc to flap back due to gyroscopic precession.<<
Flap back is not related to this discussion, as per above (see Arm out the window’s explanation on flapping to equality/cyclic feathering). I will not go into the gyroscopic bit as I do not full understand the dynamics of gyroscopes, but in my original post, I had a go at describing recovering from RBS. In that description I noted that you get a pitch down in the absence of a rolling moment. I note that you ignored it too.
There is not a difference of opinion being discussed here (Mr Prouty and Ft Rucker teach flapping to equality and cyclic feathering), so please do not divert the conversation by saying its just a difference of opinion. You will never develop in your knowledge if you cannot start from sound first principles.
A disclaimer: I am no expert, and some of you will no doubt see flaws in my explanations, so dig in, I am here to learn too. I need a drink now…..