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  #171  
Old 05-09-2019, 10:58 PM
gasman gasman is offline
 
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Originally Posted by Red Rooster View Post
In between the firewall and turboprop, you have options. BRS, Header tank, or batteries for the turbine. Or a combination of any two. So the engine doesn't have to be pushed to far out in the front. IMHO.
Running out of fuel AND creating an aft CG would make for a bad day..................
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  #172  
Old 05-09-2019, 11:23 PM
Turbine Aeronautics Turbine Aeronautics is offline
 
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Location: Adelaide, South Australia
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Originally Posted by gasman View Post
Running out of fuel AND creating an aft CG would make for a bad day..................
Yes, a header tank there is not such a good idea in my view for exactly the reasons you have stated. But batteries, a BRS chute i.e. fixed items, those are logical.

Dave
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  #173  
Old 05-10-2019, 10:19 PM
Red Rooster Red Rooster is offline
 
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Originally Posted by gasman View Post
Running out of fuel AND creating an aft CG would make for a bad day..................
Im not very familiar with the RV3. I have a 6, but the 3 i was looking at had a Header Tank. Maybe he knows something you don't?
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  #174  
Old 05-11-2019, 06:24 PM
Turbine Aeronautics Turbine Aeronautics is offline
 
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Originally Posted by Red Rooster View Post
Im not very familiar with the RV3. I have a 6, but the 3 i was looking at had a Header Tank. Maybe he knows something you don't?
Hi Jereme,

I think you will find that gasman was differentiating between an aircraft that has been designed to have a header tank which takes into consideration the effect of either a full or an empty tank on the cg (such as the RV3 you refer to) versus an aircraft that has a header tank installed which was not a part of the original design.

A header tank used to shift the cg forward to help balance a light engine may have the aircraft within its cg envelope when full or partially full, but unless the calculations have been done properly could compromise the aft cg limit when empty.

This clarification is provided for those who may not be familiar with the effect of burning off fuel on the cg and the potential for the aircraft to be within cg limits for takeoff but after burning off fuel, may lead to the aft cg limit being compromised.

Dave

Last edited by Turbine Aeronautics : 05-12-2019 at 04:32 PM.
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  #175  
Old 05-12-2019, 09:13 AM
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rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Quote:
Originally Posted by Red Rooster View Post
Im not very familiar with the RV3. I have a 6, but the 3 i was looking at had a Header Tank. Maybe he knows something you don't?
Possible, but it was probably the primary (and only) fuel tank.
Early RV-3's had just a single tank mounted fwd of the instrument panel (similar to a J3 Cub). There was no other fuel tank(s).

A header tank by definition is a smaller tank that is fed by the other aircraft tanks, that is positioned at a higher level than those tanks so that some head pressure is provided for in the feed to the engine.
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  #176  
Old 05-13-2019, 11:27 AM
breister breister is offline
 
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Quote:
Originally Posted by rvbuilder2002 View Post
Possible, but it was probably the primary (and only) fuel tank.
Early RV-3's had just a single tank mounted fwd of the instrument panel (similar to a J3 Cub). There was no other fuel tank(s).

A header tank by definition is a smaller tank that is fed by the other aircraft tanks, that is positioned at a higher level than those tanks so that some head pressure is provided for in the feed to the engine.
My 2 cents worth.

If the plane was ALREADY designed with a header tank, it will be no help at all with CG in compensating for the lighter weight of the turbine. Battery, BRS, permanent O2 tanks (since you now have an engine that will happily fly to the high teens) are all candidates to add forward CG to avoid having to move the engine far out front.
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  #177  
Old 05-13-2019, 12:34 PM
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Mel Mel is online now
 
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Default Yes, CG is a factor, BUT..............

Am I the only one who thinks that having a fuel tank forward of the firewall is a bad idea?
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Last edited by Mel : 05-13-2019 at 12:37 PM.
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  #178  
Old 05-13-2019, 12:47 PM
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airguy airguy is online now
 
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Originally Posted by Mel View Post
Am I the only one who thinks that having a fuel tank forward of the firewall is a bad idea?
Or an oxygen tank, and for the same reason.
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  #179  
Old 05-13-2019, 07:01 PM
Turbine Aeronautics Turbine Aeronautics is offline
 
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Location: Adelaide, South Australia
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Quote:
Originally Posted by Mel View Post
Am I the only one who thinks that having a fuel tank forward of the firewall is a bad idea?
I don't think anyone is advocating having header tanks/oxy tanks etc. forward of the firewall. If anyone did do that, they should probably be reported to the TSA as a suspicious person.

However, if the firewall could be moved forward 6-12", there would be scope to add weight aft of the new firewall location, but well forward for cg purposes.

Dave
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  #180  
Old 05-14-2019, 10:32 AM
breister breister is offline
 
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Quote:
Originally Posted by airguy View Post
Or an oxygen tank, and for the same reason.
While O2 tanks do lose some weight slowly as they discharge, the difference in weight change over a flight is far less than for fuel. Locating them where a header tank would have been would result in far less CG change than a comparable fuel tank.
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