Reading the report – the pilot ignored not one but two low fuel advisories. So if anything the system worked as advertised.
Totaliser shows you how much fuel flew through the meter. Not how much fuel you actually have.
Uhm … how should I say it. If I subtract the fuel used from the fuel I had, what do you think the result could be? ;-) Actually there’s a very smart computer in my Entegra MFD, it can do that all by itself!!
Flyer59 wrote:
Uhm … how should I say it. If I subtract the fuel used from the fuel I had, what do you think the result could be? ;-) Actually there’s a very smart computer in my Entegra MFD, it can do that all by itself!!
And how does that method account for a potential leak before the flowmeter? You can do whatever calculations you want, fact is that a totaliser doesn’t measure the amount of fuel in your tanks. It can show you what should be there, but not what’s actually there. Lets call things what they are.
As I said: I do compare the indication of the totalizer with the gauges, and I know what indications make sense.
Of course you can make up all kinds of scenarios. When was the last time you heard about a “fuel leak” in flight?
I am yet to see an airplane fuel gauge that shows me “what’s actually there”. It might exist (probably in a Socata airplane ;-)) but I haven’t seen one.
If I had my own aircraft, it woud be one of the first things I’d put in it. Seeing it work in your aircraft, I can see how it really allows you to use the range without ever finding yourself in the position where you might be tempted to think “It will be ok…I was conserative with my estimates.” It’s very black and white…..either there is enough fuel or there isn’t. (Leaving aside of course a safety margin for unexpected events).
But as a renter, I obviously don’t have that choice.
What surprises me more, is that “regular renters” don’t make more of an effort to understand the aircraft. Most seem to use a consumption rate that their instructor told them. Some feel really proud that they ignored that and went to the POH. But all these are largely theoretical as we all tend to fly an aircraft slightly differently. That could be different power settings, different altitudes, different climb rates, more ground running time, throw in a few circuits or just go straight. Even those who think they are using the same power settings often have slight differences which make a significant difference to the fuel flow, and that’s leaving aside differences in leaning technique which is enormous between individuals.
In fact most of us don’t even have an accurate dip stick, so we only know the fuel we have when it’s full or at tabs.
Many years ago, I ran one thank down until the bottom was clear of fuel (It’s on a slope, so still 16 ltrs left). I then filled it 10ltrs at a time and got really accurate measurements, and used this to calibrate a dipstick.
Then for the next few months I made accurate logs of my fuel consumption during the flight (fuel at take off less fuel dipped after landing), the amoutn of airbourne time, the amount of ground time, the altitude of the flight and the power settings.
From this I found a really consistent fuel rate per hour for MY flying technique. Out tank holds 183 ltrs, and I can predict the fuel that will be loaded to full tanks to within 5 ltrs. But it’s only true for my flying. If someone else flys it, my accuracy is much less.
Of course this doesn’t give the confidence of a totaliser, and there are occasions when I’m further out than that, so you can’t really push it. But it does go to show that the “uncertainty factor” can be reduced a lot, with a bit of work, even if you can’t install a totaliser.
Colm
I am yet to see an airplane fuel gauge that shows me “what’s actually there”
An admirable example was shown in #07. Ok, that IS a simple aircraft – if you choose to fly something more complex, the consequences are up to yourself.
Yes, that kind of “gauge” works in a simple high wing airplane like the Cub, but not in a low wing. Probably what WOULD work best is the type where a floating part with a thin wire on top extends from the fuel cap. I’d actually rather have those than the normal gauges ;-)
One more reason to not fly a low-winger… but that’s another discussion, and I think we had our part of it.
The kind of “cork with a needle” you describe works only for a fuel tank between cockpit and engine, such a tank can never be big enough for any kind of touring. Plus it is a bit far from the center of gravity, changing the balance as it empties, plus I for one do not like the idea of having all that fuel so close to the engine AND so close to my person.
dublinpilot wrote:
In fact most of us don’t even have an accurate dip stick, so we only know the fuel we have when it’s full or at tabs.
That is exactly the problem because of the notoriously inaccurate fuel gauges on most light aircraft, and that is true whether you have a fuel totaliser or not because you need to be able to verify that the FOB given by the totaliser is correct.
There is only one entirely reliable way of knowing your fuel on board before flight: eyeballing it. Full or to the tabs. That does however require that you know your aircraft’s fuel capacity, and in a club with similar aircraft, some with long rage and others with normal tanks, it may be a challenge to some.
Other ways:
On the airplanes I currently fly, I have gained confidence in the gauges and in the totaliser. Most of the time I will leave with full tanks, IOW a known quantity of fuel and the totaliser reset accordingly.
During the flight my PLOG contains a running estimate of FOB that I compare to the value reported by the totaliser and cross-check with the gauges.
After the flight I compare my estimated fuel burn to fuel burned during the flight as per the totaliser. That allows me to gradually improve my fuel estimates.
Before fueling I estimate the amount of fuel to full tanks and compare that to the amount of fuel actually uplifted.
Once, while flying a Bonanza I had fuel venting from the fuel cap. Fortunately it was during the day and we caught it quite soon after takeoff. Had I not been able to visually spot the fuel leak, the only way I would have had to catch it is by detecting a discrepancy between my estimated FOB and the gauges. The totaliser would not have helped.
I have a very accurate fuel totalizer with all the bells and whistles that exist today.
I could do fine without. I know my endurance in hours because I know the fuel consumption for my cruise setting. It is accurate enough. Still nice to have a totalizer but it does not increase my mission capability nor enable anything that I couldn’t do without.
