I watched the fuel gauge drop from half to zero in less than 10 seconds, as though someone had taken the plug out of the sink. On the ground afterwards, it showed half full again. Fuel gauges generally seem to be generally pretty dodgy. With two wing tanks in the TB20 it’s fairly important to keep them balanced as well as knowing how much is left in total – we use a JPI fuel meter for that.
But it got me wondering if I need to note the times of tank changes more rigorously. Or perhaps even log the fuel total at each change. After all, the consumption during the initial climb is a lot greater than in the cruise.
The POH says to switch after 30 mins, then hourly thereafter.
How do you note tank changes and what routine do you use?
On the piston I used to change based on the totaliser and list the amounts in two lines which I would cross off. The left line went 10 30 50 70 and the right 20 40 60 80.
You couldn’t have more than a 10 gal difference due to POH requirements. This helped a lot flying Greenland Faroes as the gauges were wrong and showed a low fuel number. The totaliser was right and we were able to confirm with the manual list.
Edit: we put the time of each change next to the gal number.
A fuel flow totalizer is important if go on long distance trips. However, I take very good care of my faul gauges. Should a fuel gauge show empty, I would treat this as a technical emergency and interrupt my flight at the earliest convenient possibility. There are many ways fuel can be sucked out the aircraft without you noticing it.
The FAA certification requirements for fuel gauges are simple: they have to show empty when the fuel tank is empty. That didn’t encourage the development of reliable and precise fuel gauges…
Should a fuel gauge show empty, I would treat this as a technical emergency and interrupt my flight at the earliest convenient possibility.
Empty yes. But if it shows 40 gallons when you expect 55 and you need to decide whether to turn back or continue, a totaliser is important.
As I mostly fly Cessnas, I don’t normally have the switching tanks issue. That said, I learned to fly on PA28s and my instructor taught me simple trick: switch tanks according to the minute hand on your watch. IOW, right tank from 1-30 mins past the hour, left tank 31-60 minutes. Rinse and repeat. Simple and works well to avoid imbalance.
On the accuracy of fuel gauges….. on most / all spamcans better ignore the damn things, especially if you are renting. There’s one airplane I’ve been renting for many years and know very well, and that’s the only one I even look at the gauges, as I know what they are doing (read – how imprecise they are and what the readings mean).
It’s only natural that fuel measurement via floats is imprecise. Same with my ST-10, although its gauges cleverly under-indicate. I have set myself the rule to never fly below 1/4 of the fuel capacity, except for very short local flights eg. to the workshop on the neighboring airfield.
Do newer SEP (eg. SR20/22) have capacitive fuel measurement?
That said, I learned to fly on PA28s and my instructor taught me simple trick: switch tanks according to the minute hand on your watch. IOW, right tank from 1-30 mins past the hour, left tank 31-60 minutes. Rinse and repeat. Simple and works well to avoid imbalance.
That’s exactly what I do. Sometimes I miss the change by a few minutes, but it usually balances out.
Having said that you tend to get to know the fuel gauges if you fly it regularly. If you so them drop very low when you wouldn’t normally expect it, I’d land asap and check. As achima says……there are lots of ways of losing fuel and not know it.
I use the Garmin (430) reminder every 15 minutes, no chance to forgett it.
Changing tanks based on time doesn’t tell you how much is in the tank though. It just avoids an imbalance. Without a totaliser it is the best you can do though.
