Tgrendl: You are right about the yaw, well spotted. I think the roll component is what grabs your attention first, and when you think about it, any right yaw in a right hand angle of bank can be appear to the pilot as dropping the nose downwards similarly to pitching down. I totally agree with your comments on looking up and seeing something unexpected, that although the fuselage rolls right, the disc would be offset to the left. I think that is the exact reason why the technique gets you to look up and fly the disc – because it is not where you expect it to be. Thus my point was that the recovery may not be “natural” in the sense that countering the right roll/pitch down may bring you unstuck.
To Lu:
In response to your comments;
1) Bell blades do lead and lag. I guess we will have to agree to disagree on this one.
2) As you indicated: the 18-degree offset is yet to be proven to have an effect in zero G recovery, thus I would avoid attributing characteristics to it that appear to be shared by other teetering heads without it, i.e. the tendency to mast bump if using incorrect piloting techniques. I cannot agree with your comment that: >> on the Robinson the effect of left aft cyclic in the recovery will introduce very high flapping loads resulting in either mast bumping or rotor incursion or both<< I do not accept that the introduction of cyclic causes flapping, even though I have never flown the Robbie. Flapping is related to induced flow over the blades and will occur during acceleration OR deceleration. Although I would accept that as the blades fly up or down in response to cyclic feathering, there is a change in induced flow, this is irrelevant in the context of mast bumping. See my explanation in the previous post (9) which explains the situation devoid of flapping.
3) See 2) above.
4) Lu, I seem to have put my point across poorly here. My point is that the Bell teetering head is subjected to the exact same dangers of mast bump in zero G even though it does not have coning hinges or an 18 degree offset. I.E. the coning hinges and 18 degree offset are CANNOT be relevant factors in mast bump if it occurs even when they are absent from the design.
5) You state that: >>Flapping to equality does not enter into this discussion as it is mainly encountered during forward flight and can be countered with cyclic input<< When you start talking about flapping loads due to cyclic inputs, etc, in YOUR discussion, I believe you are demonstrating some misconceptions about flapping (see (2) above), hence I again suggest you learn this concept. I have said on previous posts that I believe that the credibility of some of your theories suffers due to the fact that they can sometimes be seen to ignore the basics.
6) Got it.
7) Several issues here, firstly Lu you said: >>free flapping blades in a sense go wild [in zero G] which can have several effects<< This is another disagreement we continue to have. The rotor disc DOES NOT suddenly become wild or unstable during zero G. In fact the problem is the opposite: that it maintains its stability and does not follow the fuselage. If you REALLY subscribe to your gyroscopics theory, wouldn’t that tell you that the disc will maintain stability due to its gyroscopic tendencies?
Also you said: >> there is a discrepancy between the teachings of one instructor and the POH<< Simple problem here Lu, there is no such thing as perfect standardization. I know nothing about the techniques best suited to a Robbo, but I do know as an instructor that if I teach something to a student and it gets him killed, I need to be able to fully and scientifically justify the technique. If the technique is in accordance with the manufacturers requirements, I have justified myself and the problem belongs to the manufacturer. If on the other hand, I have taught a technique in contravention to the manufacturers instructions and I cannot scientifically justify why, then surely there would be a liability (and moral) issue. IMHO. This is not intended to in any way discredit, nor disagree with the instructor you mention as I reiterate I have no knowledge of the ins and outs of the Robbo. Each to his own.
Lu, in regards to your theories of low inertia blades “slowing down under maneuvring”: they dont! This is, however, irrelevant to the discussion, perhaps another thread?
8) I think my misunderstanding is with your grammar. All things flying can be subjected to zero G, but you used the word “susceptible”. Perhaps you meant “susceptible to mast bump in zero G situations?”
9) Thanks.
10) The reason the Oz record was mentioned was that you seem to keep inferring that the Robbie is at fault here, and that inference is continued with your discussion about the training rotor head. I would suggest that ANY rotor head with a severe imbalance would eventually cause mast/head/blade fatigue and possible separation if you had a brain failure that meant you kept flying it.
Nothing Robbie specific.
My overall summary was that zero G and its dangers ARE NOT Robbie specific, the course is reputedly excellent. The “what they don’t teach you” appears to be for a very good reason .