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Coriolis vs Conservation of Angular momentum

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Coriolis vs Conservation of Angular momentum

Old 24th Dec 2020, 06:04
  #141 (permalink)  
 
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but it's not a huge angle change (about 5 degrees according to my trig)
Maybe true if you were at the ship's cg, which is down by the engine somewhere.

Up on deck and 50m from the cg, the physical heaving and rolling gets a little exciting. And I have only landed on bigger (for Oz) boats of Supply and Tobruk and the carrier Melbourne. The smaller boats need balls of stainless steel.
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Old 24th Dec 2020, 08:12
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Old 24th Dec 2020, 08:20
  #143 (permalink)  
 
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Then try doing it at night
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Old 24th Dec 2020, 09:37
  #144 (permalink)  
 
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Originally Posted by [email protected] View Post

sorry, I misread your post - it is 180 degrees because the pitch change starts 90 degrees before max rate of pitch increase and hence max rate of flap up.
No I mean 180 degrees peak to peak.

The maximum "rate of flap up" i.e. the vertical speed is reached at the end of upward cyclic component of the aerodynamic force that is controlled by the AoA, not at its peak.

You need the gyroscopic effect to get 90 degrees peak to peak.
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Old 24th Dec 2020, 09:51
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Originally Posted by [email protected] View Post
Then try doing it at night
It is midnight, mid-winter in the North Atlantic in a Force 10 storm. I am sitting in my Wasp perched atop the hangar/flight deck of HMS Tartar. I am lashed to the deck and the swivel link is on, but my AI is telling me that the ship, a Tribal Class designed for the Gulf and without stabilisation, is rolling more than 20 degrees to port and starboard. My rotor disc follows the movement of the ship exactly and I need to make no control movement, except that I push down on the collective and through the detent to remove the last 2 degrees of pitch and cling even more tightly to the deck.

The AI is a gyroscope; the rotor is not.

There is no thrust from the rotor and no blade produces any thrust at any point in its path.

I trim the cyclic forward and the tip-path-plane tilts down. The blades are flapping cyclicly.

There is no thrust from the rotor and no blade produces any thrust at any point in its path.

Explain this and you will have explained why an 'ideal' articulated rotor has 90 degrees phase lag. You will also be able to give an indication of why offset hinges, delta hinges etc reduce the phase lag. You will do this without any mention of gyroscopes, gyroscopic effect or gyroscopic precession.

Of course, this will be a 'simple explanation' of the gross behaviour of a rotor in quasi-steady-states. It will not explain the behaviour in transitory states, when I fully expect the dynamics of rotating masses, 'gyroscopic effects' if you like, to be important.

Last edited by HissingSyd; 24th Dec 2020 at 13:00.
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Old 24th Dec 2020, 15:53
  #146 (permalink)  
 
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The maximum "rate of flap up" i.e. the vertical speed is reached at the end of upward cyclic component of the aerodynamic force that is controlled by the AoA, not at its peak.
If you mean that the journey around the swashplate can be considered as half uphill and half downhill with two 'neutral' positions in the middle, then from one neutral position, the blades start moving up and reach the maximum rate of flap up 90 degrees later but the high point of travel 90 degrees after that - then I agree with you but I don't think that is what you are saying.

The difference between those of us who are helicopter pilots and those who are theorists is that we get paid to do some of exciting stuff mentioned already on these pages, using our training and skills to complete demanding tasks in the machine we are given. As a result, most of use give little thought or worry as to whether the rotor is flapping or precessing (it is flapping btw) so much of your well-intentioned analysis is irrelevant beyond academia.

But don't take it to heart, keep on arguing your case - someone, somewhere cares.
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Old 27th Dec 2020, 00:04
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Symmetry of lift.
E86
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