I agree with all of this.
Mooney_Driver wrote:
Really? For me that IS the interesting part. PLOG’s are imho still something I would never ever leave the ground with unless I stay in the circuit and keeping a fuel track record is about the essence of situational awareness. Cases like the Air Transat A330 show that brutally, where a hyper-modern airliner runs out of fuel due to the loss of situational awareness.From what I see looking at how most people operate their airplanes, far too many are blissfully unaware of what their airplanes really can do and how to set up professionally for flying airplanes to their max efficiency and range available. It is not enough to fly “by ear” but the only way to really being able to achieve POH figures is to keep at them very carefully and more over to keep to the fuel schedule your flight planner has used to calculate your PLOG.
While this should be obvious, it rarely happens. Most flight planners use fixed percentage of power fuel flow, so i.e. 65% as the probably most common. However, 65% power is hardly an absolute value, you can achieve it with various RPM and MP settings to achieve the 65% fuel flow, but the way its done has impact on TAS. So unless you know for sure which power setting exactly was used in the PLOG by the flight planner, you won’t achieve the result the plan gives you. And way too many pilots will then blame the differences on “inaccurate wind forecasts” and similar excuses.
Performance imho is the crown jewel of flight planning and is very often not taken anywhere serious enough in our GA world to enable us to really fly to the limits of our planes. I would think that knowing exactly what figures to see and maintaining the awareness of whether what you see is what corresponds to the basis of your planning is far more important than any gadgets, however practical they can be. Having said that, a fuel flow instrument with verified performance and a totalizer are certainly the most valuable tools in this game.
Done any good trips lately, guys?
It would be great to see you fly to join us at EDNY – we have ~30 for the dinner.
I’m not sure it’s necessary to set ‘precise power’ to have any idea of fuel flow in the absence of a fuel flow indicator or a totaliser.
Our TB10 has neither and, from experience as well as studying the POH, I use 40 litres per hour as a planning number. This works well for two reasons: firstly, because cruise fuel flow is never going to be more than 40 litres per hour – it usually ends up being in the region of 34-38 litres per hour depending on altitude and power setting. Well, it might be more than 40 litres per hour if you fly everywhere at 2,000ft, full rich and 25"/2500rpm, but I don’t do that. So it gives a nice margin that adds comfort when working without precise instrumentation. Secondly, it holds 204 litres (call it 200) so that is a nice round 5 hours fuel with full tanks.
I have never flown it on a leg longer than 3.5 hours. Whether than constitutes going places or not is a different question, but after 3.5 hours I am thoroughly ready to stretch my legs. Such flights are invariably with 2 on board, so one takes full fuel and then fuel is hardly a consideration – such is the margin.
The other common scenario is 4 on board MTOW departure. Obviously this needs none of the 4 to be ‘big’ and careful W&B management, but I do it a fair bit and now have a good idea of what works and what doesn’t. I do the calculations, but I know pretty much where it’s going to come out. Typically 4 up I am restricted to 120 litres which is 3 hours fuel. I never plan to land with less than an hour on board, so my max planned leg in this configuration is 2hrs.
Pretty simple and doesn’t require precise power settings. For anything of this nature I’m much more comfortable using approximations that are well on the safe side than I am using precise values that may not reflect reality if one of many variables are not in my favour that day.
Graham wrote:
I have never flown it on a leg longer than 3.5 hours. Whether than constitutes going places or not is a different question, but after 3.5 hours I am thoroughly ready to stretch my legs. Such flights are invariably with 2 on board, so one takes full fuel and then fuel is hardly a consideration – such is the margin.
Same airplane, same approach on my end. I just got my first ever fuel flow + totalizer setup, and I’m still learning to trust it. I’ve flown 7-10 hours one way before I had this, and I used exactly the same estimates. People flew for decades without these devices and managed ok, but clearly there’s a huge safety improvement when you do have one.
7-10 hours in a TB10… is that even possible?
The kit just allows you to use more of the range capability and run closer to the margins, assuming you trust the kit of course. Whether you feel range limited and want / need to get closer to the full capability, that’s one question.
For me it’s more about wanting large margins for error, especially in a 2 tank setup with no ‘both’ setting, such that when your fuel is low it’s not how much is onboard that is uncertain but how it is distributed. I’ve never had any kind of diversion or anything go wrong that prevented me landing at the time planned, but one day that will happen and there’s no telling how badly wrong things might go. When it does, I want to proceed somewhere else knowing that it’s all fine and well within range. I don’t want to divert while doing mental gymnastics to try and work out exactly how much time I have left and whether I can reach airport X but not Y.
There are a lot of factors here, as always in GA. The detail is what matters.
People flew for decades without these devices and managed ok
Many did not. And many do not today because they have have accurate fuel metering. The seabed between S. UK and the Channel Islands, particularly Jersey (cheapest avgas) is lined with wreckages of planes (particularly twins) with empty tanks (well they will be full of water now) and often with bodies inside. See my EGKB-LGKR example above; nobody can argue with a straight face that was “good planning”, not only because “planning” is impossible when working with such tight margins.
A very significant % of crashes are with empty tanks, and it would be far worse if people flew trips “longer than the bladder” etc.
I’m still learning to trust it.
Check it regularly against your airport pump. In N Europe it is probably accurate. Elsewhere, often not. Bowsers, less likely.
Mine gets checked every fillup.
after 3.5 hours I am thoroughly ready to stretch my legs
Sure; most people do that, and that is probably how GA gets away with the traditional crappy fuel metering. I have posted about my PPL training experiences previously, but googling the G-OMAR crash report will get you an idea of what went on. That was an AOC company, BTW 
The problem with not having accurate fuel metering (a totaliser is the only way) is that one wastes a big chunk of the aircraft range. In Europe there are too few runways, too much PPR, plans have to be so rigid… For me, flying where one can drive in a similar time is hardly worth flying.
I don’t think many pilots set their target mixture by nailing LFOB & ETA at destination?
Nobody does that. You set the mixture for peak EGT/LOP and fly, and accept whatever GS you get. With LDLO closing 1300 UTC you need to leave early but that’s obvious.
7-10 hours in a TB10… is that even possible?
It may be, but at a power setting which won’t get you anywhere useful 
One can get a TB20 to “stay airborne” on about 8 USG.hr which is > 10hrs endurance.
Peter wrote:
The problem with not having accurate fuel metering (a totaliser is the only way) is that one wastes a big chunk of the aircraft range.
Sure, but I think for a lot of the GA population that isn’t a major limiting factor – we don’t usually fly 4 up in 4 seat aeroplanes so we can usually take full fuel. With 5hrs fuel in the TB10 I could of course plan and fly a 4hr leg, and one day I may do – my ‘system’ is good enough to work with those margins. Would I ever plan a longer leg than that, even if I had a totaliser? No. I plan to land with a minimum of one hour on board, come what may. So it doesn’t give me any more range.
What I’d find more limiting with the TB10, if I were to tour Europe, would be the ceiling.
That’s all fine but the OP has a PA28R which has more capability, and he does do longer trips.
I fully accept most GA does short trips only. That is how this business gets away with crappy fuel metering.
But the point still holds. Unless he’s prepared to go down to LFOB <1hr (and who is, on a flight of non-trivial length?) he doesn’t get any more range using a totaliser than he can get with a rule of thumb.
Sure, it is nice to have the accurate numbers in front of you and it makes it easier and perhaps more comforting. But your LFOB on any given flight is highly predictable (save for large variations of headwind – which is why endurance is sometimes a more useful measure than range), given that precision is not so important because we like large safety margins.
The safety margin desired drives the necessity or otherwise of precision. It’s a bit like the debate about GPS accuracy with regard to ADS-B collision avoidance kit – I don’t need it to be accurate to ~5 metres because I am not planning to avoid them by that small a margin.
Graham wrote:
7-10 hours in a TB10… is that even possible?
Not all at once. My point was that I did make longer trips pre-fuel totalizer. I also frequently take 4 people and bags on these trips, so I have to manage fuel closely. I like having the gadgets, but I plan conservatively anyway to avoid getting into trouble.
