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Today I was going to ride to Dayton and started my journey with 2 bars that went to one after 3 or so miles. I had a station picked out just east of town and when I got there I found that I had forgotten my wallet (and my belt). So I turned around and the bar started flashing about 2 miles from the station. I had about 25 miles left to get back to my house and another 2 to get to a gas station so I was fairly confident I would be fine, but when I did fill up it took 3.5 gallons. First time it had taken over 2.9 gallons for me.
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(07-28-2013, 11:59 AM)Randy_S_imp Wrote: Today I was going to ride to Dayton and started my journey with 2 bars that went to one after 3 or so miles. I had a station picked out just east of town and when I got there I found that I had forgotten my wallet (and my belt). So I turned around and the bar started flashing about 2 miles from the station. I had about 25 miles left to get back to my house and another 2 to get to a gas station so I was fairly confident I would be fine, but when I did fill up it took 3.5 gallons. First time it had taken over 2.9 gallons for me.
Wow, thats the most I 've ever heard of someone putting in one I think.
Anyone else put more than 3.5 gals in one yet?
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In small planes you use a dipstick or sight tube before you take off. Then you monitor fuel flow. Newer planes have totalizators of the actual fuel used but unless you have dipped the tanks before takeoff these are not helpful. You have to know what's actually in the tanks before starting your flight.
Turbine aircraft usually receive a slip showing how many pounds of fuel were pumped into the tank. But older ones still rely on dipping. More than one passenger jet has run out of gas because the ground crew miscalculated a conversion from metric to English or vice verse.
Gentlemen,
For the last 35 years I have been a commercial/instrument rated pilot in both fixed wing and helicopter aircraft. I also worked as the airshow demonstration pilot for the Stoddard-Hamilton Aircraft Company. Over the last 3.5 decades I have flown everything from hot air balloons to supersonic jet fighter trainers, well over 100 different types of aircraft and I have never used a dipstick nor seen anybody use a dipstick to check fuel levels in modern (post-World War II) light aircraft. 95+ percent of aircraft carry the bulk of their fuel in the wing (the wings are the main fuel tank) and because of it's dihedral (the shallow V shape) it is not even possible to use a dipstick to check fuel levels in most aircraft wings (the straight top wing on an Aviat Husky or a Cub would be an exception here). It is possible to use a dipstick in the fuselage tank of an old biplane like the Great Lakes or the early model Pitts Special. Perhaps this is where Stretch observed such a procedure.
A sight gauge is a clear plastic tube attached to fittings on the top and bottom of an aircraft fuel tank. They can only be used on a fuselage tank mounted directly in front of the pilot like later model Pitts Special aircraft or on high wing aircraft like the Aviat Husky that do not have any wing dihedral. As the fuel level in the tank drops the level in that visible plastic tube drops. The sight gauge does not give a precise reading of fuel on board but it does give a reliable indication of approximately how full an aircraft fuel tank is as there is nothing mechanical to fail.
The vast majority of light aircraft have a fuel filler cap on both the left and right wings. Descending down below that gas cap into the wing tank itself is an aluminum tab that sticks partway down to the bottom of the tank, generally with a slot cut into it somewhat higher up. The maximum amount of fuel the wing will hold is clearly labeled outside that cap. The amount of fuel held in the wing if it is filled to the slot cut in that tab is also labeled, and the amount of fuel held in the wing if it is filled to the bottom of the tab is labeled as well.
In my Glasair III for example, when filled to the top each wing will hold 32 gallons. When filled to the slots each wing will be carrying 25 gallons, and when filled to the bottom of the tabs each wing will be carrying 15 gallons. This exact same system is used on Cirrus, Beechcraft, Piper, and Cessna aircraft. Many turbine and jet aircraft use this system as well.
When instructing line personnel on how you want your aircraft filled you tell them you want it filled either to the tabs, to the slots, or to the top. Before taking off the pilot will always visually verify that the aircraft was filled per his instructions. In my case, I fuel my aircraft myself to eliminate any chance of line personnel doing it incorrectly.
I have never flown an aircraft with a fuel gauge that I would trust. Even moderate turbulence has fuel sloshing around in the wing and it's not uncommon to fly with one wing slightly low which results in an inaccurate reading on the fuel gauge. After spending a ton of money trying to get the fuel gauge in my current aircraft to work with an acceptable degree of accuracy, I finally gave up and removed the gauge and the sending units. I now use a fuel flow meter (the totalizator that Stretch described) that very accurately measures the amount of fuel used. These are also called fuel computers. At the start of a flight the pilot must program in the number of gallons in the tank being monitored. Almost every aircraft has more than one fuel tank so if you run out of fuel in one you can simply switch to the other. So if both of my wing tanks are full I program in 64 gallons. As I fly the fuel computer will tell me how many gallons I have burned, how many gallons remain, and how much time I have until I run out at the current fuel flow rate. So if I'm flying along burning 18 gallons per hour and there is 36 gallons left in my wing, the fuel computer will tell me that I will run out in two hours.
This device is incredibly accurate, to within a fraction of a gallon, BUT..... as Stretch pointed out, you must know how much fuel you are starting out with before a fuel computer will do you any good.
There are a lot of older aircraft without fuel computers that still have fuel gauges. No pilot relies upon them. When I started flying back in the 1970s I would make note of how much fuel is on board by opening the caps and looking at those tabs, then I would keep track of hours flown, and fuel burn rate per hour to determine how much fuel I had remaining at any given time. The fuel computer newer planes have does that calculation for you.
The bottom line is, if fuel gauges in million dollar aircraft aren't worth a damn and are not relied upon, it's probably too much to expect for a fuel gauge to be super accurate in a $10,000 motorcycle. After a few tanks of fuel a rider will know pretty accurately how many miles per gallon he can expect. With that knowledge the trip odometer on your motorcycle is almost as accurate as the fuel computer in a modern light aircraft. A gauge reading is only a relative indication. At least it will tell you if your neighbor siphoned your tank dry last night while you were asleep. If you know that your bike gets 45 miles to the gallon, and your tank holds 3.9 gallons, you know you'll run dry in 175 miles. If your trip odometer shows you have traveled 150 miles since your last fill up, you know that you will run out in almost exactly 25 more miles. So if the next station is 15 miles up ahead you're probably in pretty good shape.
Using your trip odometer will keep you from having to push your beautiful CB1100 and lower your stress level when that last bar starts to flash. All the best.
Chip
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Nice detailed explanation Chip and fascinating to me. Thanks.
The point of my first post, which was somewhat lost in the postings was my car cost twice as much as my bike, and I have a truck that costs over 3 times as much, and the fuel guages aren't any more accurate in them either. Nowmwe know multi million dollar airplanes are in the same boat.
Hmm I wonder if boats have inaccurate fuel guages. I'm betting they do lol
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It annoys me no end that Honda couldnt get this right. The fuel gauge was one of only two gripes on the bike on the MC review.
Yeah, I know I can use the trip odo to figure it out, but years of habit make the fuel gauge mentally important. When its red and flashing I feel like I have to get fuel.
Ferret's post it has prompted me to call the dealer today to see what they say. I also got a good response from the national Honda customer service when the dealer couldn't come up with a warranty booklet. If the dealer isn't helpful they wiil be next.
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The design of the fuel gauge seems inherently inaccurate - there's what, 5 bars? Every change is 20%, supposedly. To be of much use, smaller increments, something more like 15 or 20 bars, would be needed. So, it seems by using so few, it's an admission by Honda that they knew the gauge wouldn't be much good. Kinda just a vague approximation.
A good ol' fashioned analog gauge, like the speedo and tach, might have been nice.
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Just to be contrary, the Piper Cub (the Aeronca Chief and Champ had fuel tanks in the same location) had its' tank in front of the pilot and behind the engine. A simple float and rod that rose up in a site tube in front of the pilot showed the fuel level.
When I was a young fellow growing up in eastern Montana Piper Cubs were as common as rifles (I may be exaggerating a tad
). So if you have not flown a Piper Cub yet how can you can yourself a pilot? :poke:
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I guess next weekend I'll carry extra fuel on my bike and take it till it runs out - so we can all put this issue to rest.
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(07-29-2013, 01:32 AM)ART_imp Wrote: I guess next weekend I'll carry extra fuel on my bike and take it till it runs out - so we can all put this issue to rest.
Honda says the tank holds 3.9 gallons. But 3.9 gallons filled to what? The bottom of the filler neck, the top, or ??? If there was an easy way to drain the tank. I'd like to have it bone dry at a gas station and then fill it the way I normally do to find out. I made it to a gas station running on fumes on my HD and proceeded to put 5.3 gallons in that bikes 5 gallon tank.
Chip
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All this talk of fuel gauge accuracy/inaccuracy makes me long for the good ol' days when we had to turn the petcock when the tank got down to a certain level. Pretty foolproof (unless of course you forgot to change it back at fillup...only happened once in almost 40 years of riding). With the 1100, I usually fill up at close to 130 miles on the trip odo, and I seem to consistently put in 2.7 to 2.9 gallons. So it looks like I'd have almost 50 miles more.
