Ok, Jal. I agree with your last message. However these things cannot be understood as black and white.
I totally agree that the factor which triggers all the problems is a 0 g or very low g situation.
It is true that the ELA is a very slight HTL gyrocopter. Magni is a slight HTL too, but it is more HTL than ELA. Both have a very similar HS which provides a neat negative lift push down in the tail in flight.
If you fly an Ela and with the aircraft perfectly trimmed you add power and let the stick free, the gyro will pitch its nose up. However it will pitch up too much and the final trimmed speed will be clearly lower than the initial airspeed.
In a Magni, in the same situation, the result will be smaller nose up pitch, which will keep the final airspeed closer to the initial one. We can say that Magni is better tunned than Ela…
However the important thing is what the reason is? I think that it is because the propeller blow into the tail generates an additional negative lift which Magni compensates with a higher HTL than Ela.
Be aware: more power implies more tail negative lift, that is to say, more nose up. It is the tail the main responsible for compensating the HTL, not the rotor.
And this is special for Arnaud:
If you drop your power out in Magni in the top of this stupid and dangerous maneuver that you are defending you will be reducing your tail nose up tendency originated by the HS. Of course, this will be totally compensated by the absence of HTL (no power no trust).
I have seen the film and I don’t see any abnormal bell shape maneuver. The rate at which the Magni is lowering the nose is comfortably slow. I cannot say the same about the string: the pilot seems unable of flying correctly coordinated. So I think it would be of much more benefit to him to take some turn classes with a competent gyro instructor that showing us his poor flying abilities.
The case is that this kind of bell shaped maneuver is against the teetering rotors flight nature and must be avoided. There are other much more secure ways to down a too high nose than just pushing naively the stick forward (for example turning hard and letting the nose drop in the turn: you will be lowering the nose at a safe g load factor).
Ferran
Ferran I also agree with what you are saying.
However most slip maneuvers are done as a way to steepen an approach and therefore the engine thrust is low so the tail is not getting a great blast of air from the prop. Instead the stabilizers are blocking the airflow which is coming from the side in a aggressive slip so the gyro is now HTL without the counterbalance of the tail.
The reason why I use drag over instead of PPO, which technically it what I think it should be referred to, is that it is the increased drag vector due to the increased surface area of the pod exposed to the slipstream is the main force of rotation and not engine thrust and therefore is the "power" in PPO, although I am sure even at low rpms the propeller is still providing some residual thrust and being HTL will add something to this moment force.
I have no idea where the drag vector acts, but it obvious to me that it i is below the CoG, and the further below CoG it is applied then has the additional benefit of leverage
Vance not sure of the incidence of the tail on my MTO. Chuck has already explained how the tail works on these machines. The tail work as a dampener that corrects the nose down pitching moment without pilot input as long as there is sufficient airspeed. Also a large proportion of the tail is within the prop blast. The yaw you experience in the MTO is normal, it is designed with the middle vertical stabilser with offset incidence so that it compensates for propeller thrust at cruise power setting, so when you reduce power below 3000 rpm you get a noticeable yaw that needs to be corrected with rudder. It was designed so you didn't need to hold rudder in cruise.
If the tail is in disturbed air it will not produce the aerodynamic force it was designed. I am just speculating but I suspect it is the vertical stabilizers that are disturbing the airflow if the gyro is an aggressive slip and the tail is stalled. If the tail is stalled the you are flying a pure HTL gyro and the only counterbalance force is the RTV. This would make the gyro susceptible to both PPO (drag over) and PIO.
There are many fixed wing aeroplanes where spins are prohibited for a similar reason. That in a spin the airframe disturbs the air flow over the elevator which becomes stalled and the pilot cannot then lower the nose to reduce the AoA of the wing to unstall the aircraft. It the same thing with aggressive slips in gyro with a tri-tail and large cabin/pod, the disturbed airflow stalls the HS and therefore the pilot only has the RTV to balance the drag and thrust vectors, a quick reduction in RTV for whatever reason may result in the gyro tumbling if the drag and propeller thrust forces are strong enough.
Cheers Jordan