Low g
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Baobab72,
I am not sure I can answer your question with physics (other chaps have tried), so I will answer it in a practical way. Rule number one flying a two blade helicopter is to keep the disk loaded. i.e. you don't want it acting by itself, keep the pressure on it, and all will be good.
And yes, that does apply to all two blade helis...not just Robbies.
Arrrj
I am not sure I can answer your question with physics (other chaps have tried), so I will answer it in a practical way. Rule number one flying a two blade helicopter is to keep the disk loaded. i.e. you don't want it acting by itself, keep the pressure on it, and all will be good.
And yes, that does apply to all two blade helis...not just Robbies.
Arrrj
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I do remember back in my training days, retruning from a Nav Ex in an R44 with my instructor calmly sitting in the LEFT seat not touching the controls, relaxed, looking out of the side window ..... probably plotting some fuses to pull for emergency drill training.
Being a little high to duck under the Gatwick zone to rejoin EGKR, I pushed forward with cyclic and at the same time dropped the collective sharply, but opnly a little. I have never seen anyone react more sharply - it was like something out of the MATRIX film as he grabbed collective to load the disc and took the cyclic. The look on is face told me more about how wrong that manouver was than the detailed, lengthy debief with diagrams and examples from the AAIB publications that followed.
Safe to say, I have not done that since in any teetering head machine. Smooth control movements, and never use cyclic fwd / power down to lose height in a 2-blade.
Being a little high to duck under the Gatwick zone to rejoin EGKR, I pushed forward with cyclic and at the same time dropped the collective sharply, but opnly a little. I have never seen anyone react more sharply - it was like something out of the MATRIX film as he grabbed collective to load the disc and took the cyclic. The look on is face told me more about how wrong that manouver was than the detailed, lengthy debief with diagrams and examples from the AAIB publications that followed.
Safe to say, I have not done that since in any teetering head machine. Smooth control movements, and never use cyclic fwd / power down to lose height in a 2-blade.
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baobab72
Maybe this explanation corresponds somewhat to what you are looking for: NEGATIVE G AND MAST BUMPING | Becker Helicopters .
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A fatal low g situation (in a teetering head helicopter) is usually produced by a rapid lowering of the collective (harsh entry to auto) accompanied by pushing instead of pulling with the cyclic - this will produce the effects described by Krypton John and AOTW.
I believe harsh entry to auto is never a risk to mast bumping, as it is referred on Robinson's safety notice 11 " the low G which occurs during a rapid autorotation entry is not a problem because lowering the collective reduces both rotor lift and rotor torque at the same time"
Not quite true I think mate...
I believe harsh entry to auto is never a risk to mast bumping, as it is referred on Robinson's safety notice 11 " the low G which occurs during a rapid autorotation entry is not a problem because lowering the collective reduces both rotor lift and rotor torque at the same time"
29th Apr 2013 20:49
I believe harsh entry to auto is never a risk to mast bumping, as it is referred on Robinson's safety notice 11 " the low G which occurs during a rapid autorotation entry is not a problem because lowering the collective reduces both rotor lift and rotor torque at the same time"
29th Apr 2013 20:49
Robinson are correct if they mean that a normal entry to auto will involve bringing the cyclic back to reduce speed and increase Nr - that will help keep the rotor loaded.
I suspect their notice is worded the way it is to prevent pilots being nervous about rapid entry to auto which IS needed in the event of an engine failure to preserve the Nr due to the low inertia head.
Negative g is negative g regardless of any reduction in rotor torque.
