Sport Pilot Talk

tu16 · Joined: 18 Feb 2010 Posts: 85 Location: Bellevue, WA

Hi, all - as a rookie sport pilot I wanted to ask you how do you manage fuel with pretty rough fuel guages and small appetite of the Rotax.

What I mean is that minimum 30min VFR reserve would translate to ~2.5G which with wing tanks of 26G would translate to 1/10 of the tank.
This number I'd guess is well within of measurement error of these rough guages that I have in low wing LSA I fly.

Watching these guages hands dancing around "empty" would be pretty unnnerving. Carrying reserve say to something more re-assuring like around 1/4 could mean flying with reserves around 1.5-2hr which can look a bit wasteful, say, with two relatively big people in it and you flying out at MTOW with tanks less than half full to begin with...

On my last solo $200 pie and coffee trip I took off with calculated 1hr reserve for a round trip and it was great flying out. But I was a bit surprised how quickly I became paranoid and obsessed with fuel guages arms inching increasingly closer to "empty" on the way back home - flying at 3500' over 7mi stretch of cold ocean water didn't help either. I didn't calibrate the guages personally, I have no idea what their accuracy is, etc. I became increasinlgy nervous - second guessing everything involved in my calculations and quality of gauges and couldn't wait to land instead of enjoying clear sunny weather scenery.

Now everything worked out as expected and I landed with the engine still running - but the experience begged the question. How do you guys deal with fuel management and rough guages in LSA where reserves seem to be within measurement error of the guages which do not seem to offer much more resolution/precision than that of the car. With only difference that unlike a car, running of fuel in the air doesn't always mean a soft stop at the highway shoulder... Do you just learn to relax and trust your reading of these guages and your math?

ArionAv8or · Joined: 20 Mar 2010 Posts: 271

For me that is not an issue as I fly a glass panel. My nifty EFIS tells me fuel quantity and has proven to be very accurate so far, within 2/10 of a gallon. I also fly solo 90% of the time so I always fly full tanks. The one guage I would have and trust more than the others would be a fuel flow meter. This will tell you the amount of fuel you are using in GPH, let you know if your math is correct and let you know if you have an issue such as a fuel leak. Aside from that guage I would personally trust my math and forget about the fuel guage. The only time the fuel guage has to be accurate is when the tanks are empty. This is just my opinion of course and what I have found to work best for me.

billgr1 · Joined: 18 Sep 2009 Posts: 6 Location: jacksonville,fl

I carry as much fuel as I can, you just may need more than you think.

ArionAv8or · Joined: 20 Mar 2010 Posts: 271

billgr1 wrote: I carry as much fuel as I can, you just may need more than you think.

*BINGO* We have a winner, tell him what he has won Bob. He has won enough fuel for that weather diversion he hadn't counted on and making a safe and smooth landing at an alternate airfield of his choice.

That is precisely why I fly full tanks everytime I can. One or two diversions and you learn fuel is our friend.

deltafox · Joined: 06 Apr 2010 Posts: 89

I also have a glass panel, and agree that I trust the fuel flow more then quantity remaining. I visually check tanks during preflight, enter the new fuel quantity into the computer if I've added any and calculate the expected burn for the trip. And on a clear blue "CAVU" day I get REAL nervous if it gets down to 5 gals (1 hour of flight time), so I never let it get that low. Maybe not efficient, but a lot more comfortable.

bryancobb · Posted: Tue Feb 08, 2011 10:46 am Post subject: Don't do THIS

I have a friend who flies 500 to 600 non-business hours per year, mostly IFR.

He had a Comanche 260 with a Shadin fuel management system.

He ALWAYS ran his 1st tank BONE DRY 'til the engine quit, before switching tanks! He said...it was to verify the accuracy of the FMS. It only took him a few seconds to switch tanks and get the engine back online but I didn't feel comfortable with him doing that.

On a plane that old, I would always switch tanks within gliding distance of an airport just in case the handle came off in my hand.

I don't fly with him any more. He has since bought a Seneca II twin.

3Dreaming · Joined: 10 Jan 2010 Posts: 301 Location: noble, IL USA

Here's my 2 centss on fuel management. Get to know your airplane. Check how much fuel you use on every flight. Keep record if you need to. Establish how much fuel you burn per hour of flying. Know how much fuel you have prior to take off by visually checking the quantity. Time you flight to figure your fuel usage. If your gauges show that you have less than what you think you should have and they are getting close to empty. Get on the ground and find out what is going on!!
I had a guy flying my Warrior one time. He was making a 3 hour flight, and started with full fuel. The airplane gave him some clues that something wasn't right , but he did not listen. When he landed the engine quit on roll out with one fuel tank empty, and the gauge sitting on empty. The flight that should have taken 30 gallons of fuel used 45 because of a mechanical problem. The gauges were telling him he was out of fuel, but his math did not agree.
When ever your math or gauges say you are low on fuel get on the ground.

bryancobb · Posted: Tue Feb 08, 2011 11:49 am Post subject: Agree

3Dreaming wrote: Here's my 2 centss on fuel management. Get to know your airplane. Check how much fuel you use on every flight. Keep record if you need to. Establish how much fuel you burn per hour of flying. Know how much fuel you have prior to take off by visually checking the quantity. Time you flight to figure your fuel usage. If your gauges show that you have less than what you think you should have and they are getting close to empty. Get on the ground and find out what is going on!!
I had a guy flying my Warrior one time. He was making a 3 hour flight, and started with full fuel. The airplane gave him some clues that something wasn't right , but he did not listen. When he landed the engine quit on roll out with one fuel tank empty, and the gauge sitting on empty. The flight that should have taken 30 gallons of fuel used 45 because of a mechanical problem. The gauges were telling him he was out of fuel, but his math did not agree.
When ever your math or gauges say you are low on fuel get on the ground.

I have to agree 100%. I have always totally ignored the gauges but that could have gotten me in trouble if my math were to have been invalidated by some mechanical problem that caused excessive consumption.

I will adopt your "either math or gauges" system from now on.

3Dreaming · Joined: 10 Jan 2010 Posts: 301 Location: noble, IL USA

bryancobb wrote: I have to agree 100%. I have always totally ignored the gauges but that could have gotten me in trouble if my math were to have been invalidated by some mechanical problem that caused excessive consumption.

I will adopt your "either math or gauges" system from now on.

I would much rather land when the gauges show my fuel level is low only to find out I have fuel, than not land when they are showing low thinking I have enough, only to find out I didn't.

tu16 · Joined: 18 Feb 2010 Posts: 85 Location: Bellevue, WA

Thanks all for your great input!

Short of getting and trusting flowmeter in EMS instead of those car-like fuel guages and flying solo with plenty of fuel reserve it seems there's not much to address low fuel anxiety in LSA.

I think this is a problem that is especially pronounced in LSA - it is one thing to have a 30 min. reserve for 26GPH engine where 13G is probably well within resolution/errors of the guages, and it is another to look for measly sloshing 2.5G spread thin in wing tanks on questionable guages.

I guess this adds one more consideration for reality and practical ranges of touring in LSA with 2 on board where MTOW take-offs are already done with much less than full fuel tank. Here's economy of Rotax combined with low-tech fuel monitoring actually seems to be contributing to significant waste of practical range as compared to theoretical/advertised one.

Consider that more than third of GA accidents happened due to pilot error are caused by fuel mis-management it'd be great if LSA industry would take it it upon themselves to come up with fuel management systems that have much more resolution and accuracy than is currently used in GA on bigger engines to fully exploit economy of their fuel-efficient engines.

Aerco · Joined: 26 Aug 2009 Posts: 68 Location: Corona CA

A flow meter is nice to have, yes. It will NOT help you determine if you have a fuel leak; only the quantity gauge can give you a clue to that. Unless of course, the leak is downstream of the flow meter, but that is less likely.

The wire sticking out of the tank on the Cub I usually fly does an excellent job!

3Dreaming · Joined: 10 Jan 2010 Posts: 301 Location: noble, IL USA

Aerco wrote: The wire sticking out of the tank on the Cub I usually fly does an excellent job!

That reminds me of a story one of the guys from the local FSDO used to tell. The FSDO guy owned a Cub, and one of his Cub owning friends stopped in for an overnight. The weather turned bad and he had to leave his Cub. The FSDO guy offered to fly the stranded Cub to its owners airport. On arrival the owner of the Cub was frantic saying you almost run out of gas. The FSDO guy says "no I've got a couple gallons left because the wire is that high. The owner says when it's down to there you are out. There was only a tenth or two left in the tank. The moral is each airplane is different. Get to know your airplane.

dstclair · Joined: 06 Mar 2008 Posts: 212 Location: Allen, TX

I was taught that fuel gauges were never right so you always kept track by fuel burn * time. My Cherokee burned 10g/h and had 24g usable per wing tank. I always switched tanks every thirty minutes so after 4 hrs of flight I had 4g usable per side. Ensured that even with error, I wouldn't be dry in either tank. Followed the same principle in my Bellanca which had 3 tanks.

The first thing I asked about my fuel gauge on my Sting was 'Was it accurate?'. I was told that it was and it is. I still use it as a backup, though, and go with 3Dreaming's method of picking the lowest fuel quantity: gauge or manual calculation.

Fuel flow would be another nice backup but I would still not trust it implicitly.

It's one thing to run out of fuel in your car another to have it happen in the air.

tu16 · Joined: 18 Feb 2010 Posts: 85 Location: Bellevue, WA

dstclair wrote: I was taught that fuel gauges were never right so you always kept track by fuel burn * time.

This surely works - with the following obvious assumptions:

1. you know how much fuel you have in the first place. When I pick up rental that seems (by peering inside low wing tanks or at the rough guages) to have "enough" to fly where I plan to, I still do not know exactly how much do I have - and would need to plan for generous reserves.

2. your assumed burn rate is correct. Any malfunctions, deviations, mixture adjustment problems, unusual in-flight engine regime patterns can give you different variations that can be significant enough to change the end-game reserves significantly.

Sure, nothing you can trust completely in airplane - but having instrumentation that even when it works as it should is inefficient and inexact is a bit frustrating.

( As an off-hand fantasy, Rotax could be fed from a small 2.5G - 5G reserve tank that is being maintaned full (by the boost pump/gravity depending on wing configuration) at all times from main tanks - with simple indicator when it cannot be maintained full no longer from main tanks - would guarantee 30min - 1hr reserve to refuel or fix the problem. I don't know - something certainly could be done to address #1 killer mistake in GA in 21st century )

oldsportpilot · Joined: 17 Mar 2006 Posts: 68

Go to the Sporty's web site and buy a clear plastic fuel dipstick (search "fuel gauge." Be sure to buy one long enough so it can't fall into the fuel tank. Next time a tank is low, have a fuel truck come over and put a few gallons in at a time until the tank is full, taking a reading on the sight glass as you go along. There is a simple graph that you draw which translates arbitraty numbers on on teh dipstick to gallons. Of course the airplane must be on a level surface. Doing both tanks will give you confidence in the process.

When flying a Rotax 912 ULS, figure 6 gallons per hour, a high estimate, and land when one hour of fuel is left. If you do this, I don't see how you could ever run out of fuel.