|
I am omitting the header tank and
have a fwd hinged canopy. I am planning on
mounting the hydraulic
pump fwd of the fwd hinge bulkhead most likely on the
nose gear
tunnel. I would like to review how builders have plumbed their
hydraulic
lines when the hydraulic pump is located fwd of the instrument
panel.
Thank you for your help
John Kezele
John,
If you've already made up your mind to eliminate
the header, then read no further. If you're still considering it, you might want
to read this post of mine from March of 08 in reply to someone who was
considering the pros and cons of the header system:
I'll give you my opinion but I must warn you it's
quite biased. I'm a BIG proponent of header tanks. So much so that I'm building
one into the IV that we're building now. So here it
is:
PUT IN THE HEADER TANK
If you take a look at
accident statistics in Lancairs, the majority are pilot error. If we narrow the
list down to airframe problems, fuel related ones are at or near the top of the
list. The header tank system is beautiful in its simplicity. It's gravity feed,
you don't need to suck fuel UP to the engine and you can burn both wings
together. This feature alone eliminates big potential problems; pump cavitation
and unporting the fuel pickup to name a few. You can forget the slosh
doors.
A big practical as well as safety benefit is range. In many
instances, range is safety. In all instances, range is comfort. I really like
flying our 320 from Florida to Virginia knowing that if the weather is crappy in
Virginia, I've got fuel to fly comfortably to an alternate...like Chicago,
Montreal or Boston...really! The header tank will give you another 10 or 11
gallons. HOWEVER lets assume that the header tank gave you NO more fuel
capacity. Even then it would increase your practical range. Here's my
reasoning;
No header tank. You've got two very long, very flat fuel
tanks. The fuel quantity in a tank of this shape is difficult to measure
accurately. Besides, you really don't want to get the tanks very low for fear of
unporting the pickups. Generally in this situation I'd be getting pretty nervous
when the gauge, or the clock, said that I was getting anywhere close to 1/4
tank. So in a 50 gallon system I'd want to be on the ground (in good VFR
weather) with no less than 13 gallons...probably more.
Header tank.
You've got the same wing tanks but now these are just aux tanks feeding the main
tank, the header. The header is a narrow, short (compared to the wings) and HIGH
tank. This shape of tank makes it easy to measure the fuel quantity with a high
degree of accuracy. The sight gauge is practically failure proof. We've got a
sight gauge and a capacitance gauge that always agree. If the gauges say that
I've got 5 gallons, then I've got 5 gallons. Running the wings dry is absolutely
NO problem. Once the wings are empty you KNOW that you still have 90 minutes or
more in the header. Because of the MUCH greater certainty of useable quantity in
the header, I am very comfortable flying down to 5 gallons or so. I KNOW that I
can make 5 gallons last 45 minutes and I KNOW that I, in fact, DO actually have
5 useable gallons. Same 50 gallons but now I've got at least 8 more gallons that
I'm comfortable using. That's 200 miles!
There's an old saying among the
Bonanza guys that the most effective SPEED mod that you can do to that plane is
to add tip tanks. It doesn't give you more knots, but it eliminates the fuel
stop and THAT makes if faster from A to B if you're going a long way.
If
I've convinced you to build the header tank, then here are some additional
recommendations.
Make it removable. Much easier for maintenance. (the
standard Lancair header can easily be made removable)
Put in a wing tank
cross feed. This is easy. Essentially what we have in our plane is a 3/8 tube
running along the floor from one wing tank to the other wing tank. In the middle
(right under the console) I've got a ball valve. The ball valve has an extended
shaft connected to a knob on the console. Open it and the fuel can gravity flow
freely from one tank to the other. Close it and you've got two separate tank
systems. On either side of the crossfeed valve I've got "T's" that connect to
the respective fuel transfer pumps. With the crossfeed valve open, EITHER pump
can pump all of the fuel from BOTH wings since it will gravity flow to the low
point in the system (the crossfeed valve). A single transfer pump failure still
allows you to access ALL of your fuel. Without a crossfeed, you not only limit
your available fuel but you've just turned the failed side fuel into ballast.
You might not even be able to use all of the good side fuel because of the
unbalance problem.
Put in an automatic fuel transfer system. A couple of
float switches in the header and a simple circuit will allow you to put the
pumps to "auto" and they will keep your header between full and 8 or 9 gallons
with no action from you. The system should also have a "manual" capability where
you can turn the pumps on or off as you wish.
Baffle the float switches.
We've got our float switches in a rather small sub compartment of the header
with smallish holes to allow fuel in or out. This makes sloshing or turbulence
less likely to affect the operation of the auto system. (the sight gauge taps
off the same area)
Add a third float switch (or Pillar Point sensor) in
the header at the 4 or 5 gallon level. This operates your LOW FUEL light (the
big red one) in case your automatic system fails and you don't notice, or in
case you need a reminder to land NOW.
*Optional... We also put float
switches at the bottom of the wing tanks that are connected through the pump
circuit to a "wing low" light. If the wing is empty (or close) AND you've got a
pump on, you'll get the light. This keeps you from operating the transfer pumps
dry for extended periods as well as giving you notice that you've emptied your
wing.
I've attached pictures that I hope will make some of this clear.
Please feel free to call or write (or visit) if I can help further. I'll be in
Milan, TN on the 1st. Are you near there?
Bill Harrelson
N5ZQ 320
1,450 hrs
N6ZQ IV under construction
|