JasonC wrote:
That is what the fuel gauges are for.
Sadly, in the TB20, I have found that the fuel guages are almost completely useless if one wants an accurate reading. (The same in most PA28s I remember) In my plane (which is typical?) even when the tanks are full the gauges do not show full, and so when the tanks are significantly less than full the levels shown by the gauges are of no practical use.
The PIM for the TB20 does list a procedure for re-starting an engine in flight which starts as you suggest Jason, but then deals with what to do if that doesn’t work (close the fuel supply, reduce throttle etc). The issue for me is that the engine will be rapidly cooling and so I wondered what experienced people here know to actually work in flight and whether procedures different to those listed in the PIM are those that ought to be considered.
Howard wrote:
I lie the suggestion of chrisparker wrote:
Instead of adjusting the K factor after each refuel, sum the last 6 or 8 fill ups and do the calculation on that. i.e. as many fills as possible.
Thanks. Common sense really, although I hadn’t thought of it and it is not mentioned in the Manual.
1. Are there fuel totalisers for planes like TB20s and PA28s that measure flow from each tank separately? Are these prohibitively expensive?
Yes, you can get fuel systems that measure each tank separately. It requires additional sensors (twins can have many tanks). The cost of these systems varies a lot according to how much information you want to record or display and whether your engine/s are 6 or 4 cylinder. As a guide you could expect a system like the CGR to cost $3900 before installation and taxes on a 6 cylinder single. Installing these systems is time consuming as well. So get a quote first.
Howard wrote:
2. More importantly – what happens if fuel becomes exhausted from one tank during flight and the engine stops- how easy is a restart of a hot, rapidly cooling engine during flight?
Only had it happen once in 20 years. I blame the mother in law, who asked for an explanation of how a VOR works as we tracked into DET, and then everything went quiet. Switching fuel tanks and putting the fuel pump on, brought the engine back to life in 4 seconds approx or less, as I knew that tank was low and only had 2 tanks. The propeller is windmilling and does not stop so the magneto’s are still producing a spark for the plugs. I wouldn’t recommend running a tank completely dry as there is always the possibility of having some debris in the bottom of the tank.
in the TB20, I have found that the fuel guages are almost completely useless if one wants an accurate reading
You probably have the older gauges… in that case timing the tanks and keeping a written record is the only option. That is what everybody else (PA28, Cessnas, etc) has to do – because their gauges are near-useless too, IME. In fact I think most people who fly those types just fly for x hours and assume the fuel flow is y litres/hr.
Peter wrote:
You probably have the older gauges… in that case timing the tanks and keeping a written record is the only option.
Yes, my plane is 1990 vintage. That’s why I had an EDM700 fitted. Now I know how much fuel is left on board (subject only to unidentified fuel leaks). The fitting of this device instantly allowed me to stretch my legs and relax whilst flying much longer flights :-)
On Extra aircraft wing tanks need to be empty for aerobatics. One can either empty them in flight or drain on ground. I’ve done it in flight a couple of times and restart was super quick. Just a couple of seconds after switching tanks. Wouldn’t worry about engine cooling.
I don’t understand why so many people think that running a fuel tank dry will “suck up debris from the tank”. The fuel supply is always drawn from the bottom of the tank so if any foreign objects are present they can cause trouble regardless of fuel qty remaining. Further, most tanks have an unusable qty and it is here that any foreign objects will collect and it is usually from here that your fuel sample drain will draw from. (At least that is my experience and I would imagine that common sense dictates it to be true of most if not all installations).
Peter wrote:
On long flights, the LOW FUEL light comes on when the lowest tank has 8 USG in it, and that is pretty accurate
I didn’t know that. I’ll try it.
Peter wrote:
(PA28, Cessnas, etc) has to do – because their gauges are near-useless too, IME. In fact I think most people who fly those types just fly for x hours and assume the fuel flow is y litres/hr.
But don’t ignore them completely.
A while back (I think around year 2000) I got checked out in my then flying club’s Cessna 182, an old fastback one (and it was in very nice condition). The plane was new to the club. About a week later I planned to fly it from home (at the time Houston) to Salt Lake City, stopping in Amarillo to pick someone up. Fuel calculations showed with full tanks I would arrive at Amarillo with an hour of fuel left.
The evening before I looked in the tanks because I was planning to leave at 5am, before the airfield opened, so if I needed fuel, I’d have to get filled up the day before. The fuel tanks looked full. The next morning I visually checked the tanks again, and the fuel level hadn’t changed. The fuel was about 1cm below the bottom of the filler.
I keep the fuel gauges in my cross check, even the “useless Cessna ones”. A bit north of Waco, the fuel gauges seemed to be indicating lower than my calculated remaining fuel. Given that it had turned into a beautiful sunny morning, I cancelled IFR and landed to check this out, and had the tanks topped off again. The amount of fuel that went in said that I had just refuelled with half an hour worth more fuel than I should have. I looked in the tanks. I realised that 1cm represented about half an hour of fuel! Good job I didn’t press on or I’d have arrived with 15 minutes of fuel to spare. Had the weather turned out differently and a missed approach had been made, that could have quite easily been a fuel exhaustion accident. Instead, landing early, filling up, and trusting the most conservative source (the gauges showing less than I thought I had) resulted in a simple learning experience.
I wouldn’t rely on a fuel gauge but they are often not as useless as people think. That 1950s Cessna 182 has better fuel gauges than my 2007 car has (it shows half a tank remaining when there’s really only 1/3rd left). Then you’ve got fuel gauges like the Auster main tank one which is purely mechanical and has a readout in imperial gallons, and it’s not only reliable but fairly precise too!
However, is that not the same thing as saying that one should not distrust a broken clock, because it will be right twice a day 
