Re: Need a Sparrow Strainer alternative


Jerry Marstall
 

All I know is that if one comes off in flight, you are flipped negative G's nose down with a violent roll to the near inverted.  Don't ask me how I know.  

On 9/18/2013 5:14 PM, Sam Hoskins wrote:
 
The Sparrow Strainers are draggy and slow our planes down.  There must be an alternative.  Every time a speed specialist looks at the the sparrow strainers they go "WTF"?

So, let's start at the beginning.  Why are there in the first place?

As I understand it, they are an aerodynamic trim designed to counteract the high pressure on the bottom of the canard elevator.  Air wants to push the TE of the elevator up, causing the plane to dive, so the sparrow strainers help by pushing it back down.

Is this logic correct?

So, what would be a drag-free alternative?  Well, I suppose one could increase the spring tension already used for the control stick.  Why didn't QAC do something like that?  Maybe it would increase the stick forces.  Just guessing but when they first flew flew the new  LS-1 airfoil, they probably found they needed an extraordinary amount of nose up trim.  Followed by going with the cheapest fix - add sparrow strainers.

Another issue with using internal trim, is you are applying a constant torque to the joint there the elevator bellcrank slips into the elevator torque tube.  Maybe it's not a big deal, bit it's there.

This is all supposition.  Is anyone privy to the real story?

So, all of you aerodynamic tinkerers, what could be a viable way to eliminate the sparrow strainers?

Thanks for reading.

Sam

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