hopper theory & practice

[vicenterc at comcast.net]

I agree with Bob.  It is just pressure drop on the lines.  The longer the lines more pressure drop we will have.  That is why we need to add a pump when we don't have the hopper thank abd the fuel tank is close to the CG..  Also, the hopper tank acts as a reservoir that will supply the additional fuel required during critical positions.  If the critical posistion last too long you could have a problem as Brian said.  That is why the pumps are more reliable in the long critical positions.  
Vicente Bortone

-------------- Original message -------------- 

> I know everyone ignored my first response about this - but I think it deserves 
> consideration, guys. The hopper setup probably WORKS simply because it is 
> closer to the suction source (proximity to the spraybar/venturi). Being closer, 
> it is easier for the engine to "draw" the fuel. 
> 
> I really don't think there's a lot more to this issue than suction. 
> 
> Bob P. 
> Pump-running-non-suction OS user and ARF flier 
> > 
> > From: Brian Young 
> > Date: 2004/08/13 Fri AM 08:52:12 EDT 
> > To: discussion at nsrca.org 
> > Subject: Re: hopper theory & practice 
> > 
> > Dave I think that your last couple of questions are what occur. If someone 
> would put one in a hover for a few minutes to setup equilibrium it should lean 
> once replenishment from the main tank becomes established in the new 
> orientation, anyone want to try that? ;) 
> > 
> > 
> > ronlock at comcast.net wrote: 
> > 
> > Ive been a hopper tank diss-believer for years. I also wonder why many 
> continue to report benefits. What's responsible for the benefit? 
> > 
> > I'm in agreement with Nat, and what "I think" Jerry has said regarding the 
> fuel system with a FULL hopper tank being a column of fluid, and the hopper 
> would have no benefit. 
> > 
> > Maybe hopper serves to eliminate foaming and bubbles? Do I understand heli 
> pilots use hoppers for that reason? 
> > 
> > In practice do we usually have some air in the hopper? Or do we usually have 
> a hopper tank that is flexible? Might we be drawing from the hopper without 
> replenishing from the main tank during a vertical? Then the hopper gets 
> replenished during level lines? 
> > 
> > Still wondering, Ron Lockhart 
> > -------------- Original message -------------- 
> > 
> > > >Matt, 
> > > >With or without the hopper tank we still have a solid column of 
> > > >incompressible fluid for gravity and G's to play its tricks on. I 
> > > >contend if it runs ok with the hopper it will run just as well 
> > > >without. Nat 
> > > 
> > > Nat, 
> > > 
> > > While not exactly accurate as stated, your point is well taken. Your 
> > > hypothesis has some merit when the tank is full, but it falls short 
> > > anytime else (which is most of the flight). Adding just a small 
> > > amount of air causes the system to become compressible (just like the 
> > > brakes on your car). 
> > > 
> > > Jerry 
> > > -- 
> > > ___________ 
> > > Jerry Budd 
> > > mailto:jbudd at qnet.com 
> > > ===================================== 
> > > # To be removed from this list, go to http://www.nsrca.org/discussionA.htm 
> > > and follow the instructions. 
> > > 
> > 
> 
> Bob Pastorello, El Reno, OK, USA 
> rcaerobob at cox.net 
> www.rcaerobats.net 
> 
> ===================================== 
> # To be removed from this list, go to http://www.nsrca.org/discussionA.htm 
> and follow the instructions. 
> 
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