Fuel management for safety

Published by: Henry Trikelife on 9th Mar 2014 | View all blogs by Henry Trikelife
My most biggest concern during the flights is always an engine quit. So, I always try to use flesh gas from the major brands and I replace the gas in the tank, if it is older than 4 weeks. I always use Mr. Funnel, when I fill the tank.

I heard 40% of mechanical problems in GA aircrafts are related to the fuel management. Fuel starvation, vapor lock, pump malfunction, filtration issue, etc.

I started flying over some unforgiven terrains since few years ago. I didn't have any safe landing spots in many flights and BRS is only the option to go down.

I recently added the following to my trike for the additional safety. I learned some of these during upgrading my engine. Rotax recommends these measures in the engine installation manual. My trike is 7 years old and didn't have any of these additional safety functions.

1. Fuel return line for the prevention of vapor lock.
2. Ancillary electric fuel pump.

In addition to the above, I'm planing to do the flowing soon.


3. Fire sleeves on the fuel lines. (especially the lines directly over the engine)

4. Fuel pressure sender and gauge.

How do you manage your fuel related issues ? Are there any additional measures I should take into consideration ?

 

Comments

18 Comments

  • Abid Farooqui
    by Abid Farooqui 3 years ago
    Hi Henry:
    With ethanol in fuel, vapor lock at altitude or hot weather is even a bigger concern. You have done a very good thing to add a full return line to your fuel system. In the fuel distribution block that Rotax provides a small orifice allows air or vapor bubbles pop up to where the return line should be. The return line is supposed to carry this gaseous gasoline back to the fuel tank or at least the gascolator. You'd be surprised how many trikes and LSA's do not have a return line.
    Recently on Delta Jet II fuel system I forgo a very nice feature (fuel flow sensor) so I could do a full fuel return line all the way back to the fuel tank. I know a lot of trikes using ethanol gas experience some kind of hickup especially at full power. Part of the reason I am convinced has to do with tendency of vapor lock and part of it is bad fuel pumps from Rotax in recent years after they changed their supplier (not by choice). I believe vapor lock prevention is better than knowing by looking at a gauge how much fuel is being used. To do it right, one has to use 2 fuel flow sensors and then have a circuit board that subtracts fuel flow 1 - flow fuel 2 to give you the real fuel flow. Dynon has this nicely. MGL, not so much. Plus 2 fuel flow sensors alone are more than $500 and add a lot of connections and complexity and weight to the system. Thus I decided to do away with fuel flow sensor and do a proper full length return line to the tank. After all, your fuel flow at same speed at same weight isn't going to change much. With a proper fuel level sensor that is nicely calibrated, and proper fuel planning you shouldn't need a gauge to tell you what you are using. Many certified aircraft for decades didn't have this.

    Fire Sleeves on fuel lines in heated areas are not just "good idea" for protection against tendency to vapor lock, with an engine cowling/cover, they are mandatory to comply with ASTM design standard. If you ever watch the video on Rotax 912 installation by Homebuilt Help, they specifically show a popular brand 912 trike and focus in on no fire sleeve on the fuel lines right above the engine, stating that even the worse installed firesleeve is better than nothing. It had me on the floor when I saw that clip but its out there in the public and a lot of experimental builders are buying and watching that clip.

    The backup fuel pump can act as a primer as well as something that can help you get through some rough spots. It should be between 2 - 4 psi max and used in conjunction with mechanical fuel pump 912ULS has. I use it when taking off and when I come in to land (in case I have to execute a go around). Your main fuel pump is still the mechanical fuel pump. This is an add on to get you out of rough spots only. It should be after a fuel filter. For low fuel pressure system like the 912 series engine, I have also found that having a fuel filter or gascolator that you can see into during pre-flight is a very good idea. I came to this conclusion after experience with Searey production line and certification. I used to be a fan of metal gascolator from ACS and surely a lot of GA airplanes use this type of gascolator but they do not have ethanol is their gas either.
  • Mike-in- Thailand
    by Mike-in- Thailand 3 years ago
    4 weeks to throw away your fuel - is this right?
  • Abid Farooqui
    by Abid Farooqui 3 years ago
    Mike with ethanol laden fuel we start to see octane number come down and water absorption happen in as little as 6 weeks. If the fuel you got from a gas station is say a week old in the tanker, it is a good idea to use fuel that is as fresh as possible
  • Henry Trikelife
    by Henry Trikelife 3 years ago
    Hi Abid, thank you for your detailed explanations why those measurements are so important. I will feel lot safer when I finish my small project on my trike. I didn't mention that I also have installed MGL FF-1 fuel computer. I can see instant fuel consumption as well as the gas left in the tank. But I messed up the instant consumption reading as soon as I installed the fuel return line, because it reads both gas flows. One is the flow actually used by the engine and the other is the flow going back to the tank. I adjusted K factor of the fuel computer several times after series of test flights. It now indicates the fuel left in the tank that is accurate enough for long XC flights. Several of us also replaced the small fuel filter came with the trike to Racor fuel filter. This filter has a large filtration area like an engine oil filter. It separates water in the fuel too. It has the drain at the bottom and I can check the contamination as well as water separated from the fuel.
  • Abid Farooqui
    by Abid Farooqui 3 years ago
    Henry: Yes adjustment of the K factor can approximately get you there for one cruise speed/weight combo but for obvious reasons it cannot be reliable for all situations. Something that cannot work in a compliant trike well. I simply decided to omit the complexity of 2 sensors and a circuit board and 6 additional connections and weight.

    IMO, the bigger problem in something like your fuel tank/filter is actually what is inside the tank. If the pilot is not careful and lets dirt, pieces of leaves etc. end up in his/her jerry can, then they can end up inside the fuel tank. If these are bid enough to block the ID of the fuel line and small enough to enter the fuel line, you have got a bad problem. In previous Aluminum tanks that I designed and used, we had a fuel pickup with soldered metal screens on them or in Apollo we made fuel pickups with long tubes with holes drilled at many places to allow fuel in but not large debris. In the latest tank I used a machined AN welded flange and fit in this strainer. Part 23 suggests that such a coarse strainer area be 5 times the area of the fuel pickup line and this strainer is more than enough to satisfy.

    http://www.aircraftspruce.com/catalog/appages/fingstrainers.php?clickkey=9926

    I am not sure that on crosslinked Polyethelene roto molded tanks like yours, its possible to mold in NPT female fittings to accept such an item after the roto molding has been done or not. But if something like this could be added, that would be the final touch. If not, I am sure the tank has some barbed fuel pickup line coming out with straight fine threads and a copper or Aluminum crush washer (usual in Europe) and that if separate can be replaced by the kind of thing older Apollo metal tanks we made here did with an internal tube drilled about 25 times acting as a fuel pick up filter
  • Henry Trikelife
    by Henry Trikelife 3 years ago
    Abid, you are right. Actually Tanarg didn't have a strainer at the fuel intake. I think it was why they didn't install one on their tank. The issue was discussed here and David O. requested Air Creation to take care the issue. Few months later, Air Creation came up with the solution. Similar shape with the strainer in your link. The metal strainer in the small diameter can be pushed in through the rubber grommet hole at the intake. It has several long slits on the surface that goes in the tank.
  • Abid Farooqui
    by Abid Farooqui 3 years ago
    That's great Henry. You are in business my friend. Fly with confidence and safely.
  • Paul Hamilton
    by Paul Hamilton 3 years ago
    Henry, fuel this is one of the most important issues for minimizing the engine out (quit sound as I say). You have covered the important points but another very important issue is the actual amount of usable fuel when the tank gets low. This is very important for anyone flying cross country or the flight instructor trying to figure out when to stop training and get fuel. A basic fuel calibration is needed for this important question. How have others calibrated the usable “ACTUAL USABLE FUEL” at low levels with this important question?
  • Henry Trikelife
    by Henry Trikelife 3 years ago
    Hi Paul, my trike has the fuel level tube at the outside of the tank. I can read actual fuel level during the flight. My least fuel level after the long xc flight was about 3 gallons. If you count on a fuel level sender or a flow sender, correct calibration will be very important.
  • Paul Hamilton
    by Paul Hamilton 3 years ago
    Henry and others concerned about this very important safety issue,
    Nothing better than a visual for fuel level but here is the safety tip I have learned. Drain the fuel tank. Add a gallon and make sure the visual reading is the same as what you know you have. Attitude is very important for this calibration. Many times this is different at nose up, down or cruise. Never depend on any calibration but your own of low fuel readings. Add a gallon and do the same. Add a gallon and do the same. ETC...

    Another problem is that this fuel calibration is done with the aircraft at an ATTITUDE it is on the ground. Depending on any visual or tank level indication, this can vary. Some systems will read very differently based on your attitude (fuselage angle with the earth). If anyone has any issue or misunderstanding about this concept contact a CFI to resolve this very important issue. I installed a pitch bubble that allows me to get the same pitch attitude which is at idle throttle and approach nose down attitude that equals pitch attitude on the ground to assess the best situation of actual fuel in real life.
    Summary: Question any low fuel level reading you get and verify that is what it is IF you are going to operate at low fuel level situations.

    Otherwise do what I do, figure that more fuel is better than less fuel.


    The only final check for you is to make sure the visual is reality. empty the fuel tank
  • Drew Pawlak
    by Drew Pawlak 3 years ago
    I'm an up and coming trike pilot and came across this interesting discussion. So as I understand fuel level monitoring there are two ways to do it today:

    1. Visual - either you have a translucent tank or a sight tube to see the level of fuel in the tank or
    2. Digital Readout based on calibrated fuel flow/consumption

    Both seem problematic based on this conversation due to flexibility needed to visually inspect fuel level while in flight or inaccuracy of the fuel flow method.

    Has anyone considered installing a simple float and sender system like in pretty much every car on the road to accurately show actual fuel load on board? This could be connected mechanically to a dial gauge or more practically to a digital EFIS. A simple resistor setup with a shunt (to dampen motion induced variation) would work well and is proven in the automotive industry. I would still want an accurate fuel consumption method so between the two I would know what I have in the tank on the dash without being a contortionist and based on my current consumption do some basic assessment of range left.

    I am not clear where the fuel return goes but would it be possible to put the fuel flow monitor after the fuel return branch so you are then truly monitoring what is going to the carbs more accurately? I would think that would significantly simplify the installation and set up. Just a thought based on limited understanding of the fuel flow layout.

    I hope the question or approach isn't something that has been discounted in the past. If it has then I apologize for wasting your time with it.

    Drew
  • Larry  Mednick
    by Larry Mednick 3 years ago
    Hey Drew, I probably talked so long about your new REVO you forgot the first method that I told you about which was the fuel float like you're suggesting. They all have that. :-)
  • Drew Pawlak
    by Drew Pawlak 3 years ago
    Wow. Way to show I'm a noob! Where is it displayed? On the enigma? I recall us checking often visually (good practice) and not always trusting what was on the screen. Did I miss something? Maybe a screenshot? Thanks for the continuing education!
  • Larry  Mednick
    by Larry Mednick 3 years ago
    Hi Drew, yes the fuel LEVEL is directly next to the fuel CALCULATED. so in essence you have 3 fuel gauges. Although the CALC only works if you set it each flight. And of course the gauge is only as good as the sender and the programming. Without the proper K factor set to the fuel flow meter, the Calc is worthless. And without entering the proper resistance numbers from the fuel float as feel is added to the gas tank during set up, the fuel float is useless. Checking the sight gauge before flight and using the old common sense should calculation should go hand-in-hand with checking the digital guages. Because most flights in trikes are not flight plans where we calculate out fuel burn and time in the air, but more go up and play in the sky, we need to be careful we don't run out of fuel. And if it's going to happen it's going to happen when you are having the most fun you've ever had in your life. Time flies when you're having fun which also means the gas tank goes down quicker than you might think.
  • Drew Pawlak
    by Drew Pawlak 3 years ago
    Thanks Larry - I do recall you going over that now and the importance of calibrating BOTH the fuel level and fuel flow sensors. Its nice to know the Revo has that capability. However, I've flown in Airborne a few times in the past (912XT + Redback) and looked at many trikes as I shopped around for my own and was surprised by the simple lack of a dash mounted fuel gauge. Sight tubes and translucent tanks seemed typical. In Airborne's defense - a 20 gal tank is HUGE and once full highly unlikely to run out of fuel...I'd have to land and go to the bathroom before I burned through that fuel load! However with other smaller tanks the risk is real. Given there have been a number of incidents in the past due to fuel out, I would think the addition of a dash mounted and ACCURATE fuel gauge would be mandatory and simple to execute.

    If that is too complex for some trikes then how about a simple fluid level sensor mounted in the tank such that once you get to say 1 GAL left, a low fuel light would illuminate on the dash telling you to land? Clearly running out of fuel is still an issue so I can't assume this has been solved by all trike manufacturers. Just my novice input based on what I have seen and based on this AWESOME statement:

    "And if it's going to happen it's going to happen when you are having the most fun you've ever had in your life. Time flies when you're having fun which also means the gas tank goes down quicker than you might think."

    SO TRUE and when you are having that much fun - having something alert you to potential trouble is helpful. If I didn't have the low fuel light and friendly reminder "ding" in my car, I would have driven right past my reserve and been stranded waiting for AAA. Easy to get distracted in a car and no where as much fun as flying!! Just throwing out ideas that have probably been discussed in the past so I'll apologize if I'm repeating content.
  • Paul Hamilton
    by Paul Hamilton 3 years ago
    Yes the MGL Enigma and Extreme used on many trikes has a low fuel warning light that can be set for both the measured fuel sensor in the tank and the calculated fuel level from the fuel flow sensor. I have them set for 2.7 gallons and they get your attention.
  • jeff trike
    by jeff trike 3 years ago
    A sight gauge is the only one you can trust.
    Do what you have to do to install one on your trike.
  • Gregg Ludwig
    by Gregg Ludwig 3 years ago
    Jeff trike, please change "you" in your first sentence above to "I".
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