Highlander Usable Fuel

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Highlander Usable Fuel

Postby barry767 » Thu Aug 14, 2014 12:49 am

Here's something that came up today while returning from a relatively long flight. With the aircraft in a level attitude at around 6000 feet I could see that I had about an inch to an inch and a half of fuel showing through the plexiglass in both fuel tanks, which gave me confidence that I had plenty of gas remaining, perhaps well over an hour's worth. I would estimate that the tanks were about 1/4 full. However, about 10 miles out when I lowered the nose to descend I noticed that the gas shifted forward in the tanks and that the fuel pickup points in the rear of the tanks were very close to being unported. I was wondering if an extended descent in this attitude could result in the header tank running dry followed by the engine quitting from fuel starvation. If this is true, then there's a lot more unusable fuel in these tanks than I thought. Has anyone else seen this or thought about it? After the descent while approaching the field to land I pitched the nose up for a while to ensure that the header tank had filled back up. Comments?

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Re: Highlander Usable Fuel

Postby jak » Thu Aug 14, 2014 6:23 am

This is a common problem (situation) pertaining to the type of aircraft I have heard of planes running out of fuel with over half tank of fuel when pointing the nose down for a decent. To keep the fuel pickups ported all the time with this aircraft descend by pulling power and keep the nose up. the standard highlander header tank is only good for 4 to 6 min of fuel. Jak
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Re: Highlander Usable Fuel

Postby danerazz » Thu Aug 14, 2014 7:40 am

I put a 3 gallon header in for this reason, and will have a warning light to notify me when about half of that is empty. A bunch of guys have put front pickups in but unless you run fuel lines from those down in FRONT of the doors you are not helping the situation. If you never fold the wings it is no problem, but if you do you would need some kind of disconnect.
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Re: Highlander Usable

Postby barry767 » Thu Aug 14, 2014 10:03 am

Dane, That sounds like a great solution. How did you install the your 3 gallon header tank? Due to the increased weight I would guess that you'd need more than adell clamps that the smaller tank uses.
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Re: Highlander Usable Fuel

Postby Gil T » Thu Aug 14, 2014 2:20 pm

I have an early Highlander and as you can see the header tank has about 15 minutes in it until you become a glider. I have got all the fuel out of the main tanks by kicking a wing up and flying sideways for a while but that's not a recommended method unless you just want to see that they drain all the way. Supposedly with my 26 gallons 2 of this is unusable but if you're desperate you can get to it. On a few occasions on decent from high altitudes I have watched the header tank start down and get down to a cupful before I leveled off and filled it back up but that's when I'm in sight of home. That's with a shallow decent angle and power on. If you have power off and are making a rapid decent you probably won't be using much fuel. Having a way to tell the quantity of fuel in your header tank should be a necessity. I try to plan my fuel needs pretty close since I have to fold the wings when I get through for the day and that means 7.5 gallons max so it doesn't vent overboard. I do have a fuel flow indicator on my fueling system which I have posted on the forum before.

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Re: Highlander Usable Fuel

Postby danerazz » Thu Aug 14, 2014 8:02 pm

I had just aircraft make the tank, it is 6" diameter and I think 24" long, but I would have to measure it (whatever length 6" turns into 3 gallons). They put a "V" at the top that fits in the tube cluster above the stock header location, and a tab at the bottom that I built a bracket for that attaches to the two vertical side tubes. There are two adel clamps at the top, and four attach the bracket at the bottom to the fuselage, with two bolts holding the tank to the bracket. I did the math and the clamps are more than adequate, the geometry of the bracket is all that is in question.

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Re: Highlander Usable Fuel

Postby R Rinker » Fri Aug 15, 2014 12:23 am

So the guys that put outlets in the front of the tanks then don't need a header tank?? No sumps in the tanks but the gascolator would provide a drain for water contamination...
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Re: Highlander Usable Fuel

Postby danerazz » Fri Aug 15, 2014 7:48 am

If they run the front pickup lines in front of the doors, then you could probably get away without the header, though I would put at least a small vented collector tank in to separate air from the system. All of the front pickup installations I have seen run the lines BACK past the rear pickups and this really doesn't do anything for you. Fuel will not run uphill just because you have a ported pickup.
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Re: Highlander Usable Fuel

Postby bluemax » Fri Aug 15, 2014 8:51 am

danerazz wrote:Fuel will not run uphill just because you have a ported pickup.


Dane,
I will be using the Viking engine, which uses a high pressure fuel pump for the fuel injection. Wouldn't a fuel pump provide enough suction to draw the fuel "uphill " for that short distance? I'm not familiar...does the Rotax 912 use a fuel pump?
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Re: Highlander Usable Fuel

Postby danerazz » Fri Aug 15, 2014 10:41 am

Not if it can pull air from unported rear pickups more easily.
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Re: Highlander Usable Fuel

Postby barry767 » Fri Aug 15, 2014 3:09 pm

Maybe another solution would be to instal an identical left side header tank from the left tank and then tee it into the fuel line going from the other header tank to the on/off valve. This would be a relatively less expensive and easy installation that would provide another gallon or so of fuel to the engine during a nose down attitude. Has anyone done this? BTW, I am very happy with Troy's on/off valve. The fuel level seems to stay at about the same level in each tank and there is virtually no chance of screwing it up, assuming you remember to turn it on before starting (which I've forgotten to do at least a couple of time). Troy told me that's what he had in mind when designing the fuel system this way.
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Re: Highlander Usable Fuel

Postby danerazz » Sat Aug 16, 2014 1:27 am

I can't remember who, but there is somebody on here that has put two "stock" headers in, one on each side.
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Duel Header tanks

Postby gkremers » Sat Aug 16, 2014 11:17 am

Barry,
I did install 2 stock header tanks. SS braided lines from the tanks to the in-line 100 micron filters with fuel shut offs built in down to the tanks. From there they run to the Andair rule selector.The return line only goes to the right header tank.

I've got 26 hours on the plane now and about 85 landings. I'll post a report on the 40 hour test period as soon as its finished.

The only hiccup so far happened this week 4 miles south of my home field. I was on the left tank with about 3 gallons left (right had 9) and the engine started to loose power rapidly. It never quit all together but it sounded like it was starving for fuel. After switching to the right tank the engine regained power after 4 or 5 seconds. I had a hunch it may be junk in the fuel filter because as much as I tried to clean the tanks before covering I could still see fiberglass shavings from the manufacturing process. I had cleaned and checked both filters after taxing around for close to an hour before my first flight. I should have taken a picture of what I found but needless to say the filter was pretty clogged with fiberglass shavings. The right side wasn't to bad. Just in case I also pulled the finger strainers in the wings but they were clean. The shavings are so fine they just flow past the finger strains. The carb bowls looked fine so the 100 micron filters are doing there job. I plan on checking the filters agin at 40 hours.

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Dual "stock" header tanks


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Andair fuel selector


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Dual fuel drains


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Early flight sunrise


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Re: Highlander Usable Fuel

Postby barry767 » Sun Aug 17, 2014 12:28 pm

Thanks, Gary. I will most likely instal another stock header for the additional amount of fuel it will provide. Your installation looks very professional. Did you have to weld another tab on the left side to mount the left side fuel drain?BTW, Steve from Aircraft Specialty has already sent me the hoses for the Thermostasis installation. Looks like I've got a project to look forward to next week!
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Re: Highlander Usable Fuel

Postby gkremers » Sun Aug 17, 2014 2:17 pm

Barry,
I made a bracket and used adel clamps to secure. Mine was done before covering which simplified the install of the second curtis drain valve.
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