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F70100
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Full disclosure: I'm coming back to VFR from 25 years of airline flying so by all means take all this with a pinch of salt.
I'm finding one of the terms used in SkyDemon to describe the various categories of fuel required for any particular flight somewhat misleading.
SkyDemon uses the term "Holding Time" fuel to describe what in IFR flying would be "Final Reserve" fuel. i.e. the quantity of fuel loaded which you hope never to have to burn. If it becomes apparent that an IFR flight will land with less than the full amount of Final Reserve fuel on board, it is expected that an emergency will be declared. IFR flight planning also requires a minimum of 30 minutes "holding fuel" to be carried, but this is fuel that you can use if required, and is in addition to Final Reserve fuel.
Part-NCO requires VFR flights to carry "minimum fuel reserves", and this is analogous to "final reserve" in IFR.
I respectfully suggest that the term "Holding Time" be changed to "Minimum Fuel Reserves" to emphasise the point that this fuel is the last drop available, and align the terminology with Part-NCO. If fuel is required for "holding", it might more appropriate to account for it separately, or even add it to the contingency fuel.
I'm new around here; not trying to change the world, just thinking out load really.
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marioair
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SD team - can this be checked again?
The fuel plan uses term “holding time”
Based on this the fuel plan suggests you’ll land on vapours with no final reserve.
Suggestion is to add an optional final reserve and use 30/45 based on flight rules
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lhe
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I second the suggestion by F70100. With a change of part-NCO the other year, it is clear from EASA regs that "Final reserve fuel" applies to both VFR and IFR. This is an amount that must be in the tanks after landing. If any parts of this reserve gets used in flight, it is an automatic emergency.
Of course holding fuel and contingency fuel are still relevant, but the pilot should be able to specify at least the holding fuel for each flight separately.
I see that over the years there have been suggestions in this forum to allow for separate entries of contingency fuel, holding fuel and extra/discretionary fuel (fuel that the pilot for other reasons considers necessary in addition to the other amounts of fuel). That would be a good idea, too. As it is I have to keep track of these manually during flight planning.
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Tim Dawson
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I think I've said previously on another thread here that we can't really change the "holding time" way of doing things that we currently have, because thousands of aircraft profiles have been set up with this carefully set.
However, I'm definitely open to adding another fuel line in our fuel calculations, and it sounds like "Final Reserve Fuel" would fit the bill for everyone, is that right? You would enter an amount per aircraft (not a time) and that would simply be added to your fuel calculations and weight and balance too of course.
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F70100
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+xI think I've said previously on another thread here that we can't really change the "holding time" way of doing things that we currently have, because thousands of aircraft profiles have been set up with this carefully set.
However, I'm definitely open to adding another fuel line in our fuel calculations, and it sounds like "Final Reserve Fuel" would fit the bill for everyone, is that right? You would enter an amount per aircraft (not a time) and that would simply be added to your fuel calculations and weight and balance too of course. Sounds good to me Tim; I'm sure folks can enter a Final Reserve Fuel number representing 10, 30 or 45 mins worth of fuel according to the requirements of any particular flight, and if that means that holding fuel has to be reduced to zero to accommodate it, that would highlight the issue. This would be a big help from an instructing perspective for me.
Keep up the good work!!
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lhe
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+xYou would enter an amount per aircraft (not a time) and that would simply be added to your fuel calculations and weight and balance too of course. That would be helpful, but the time corresponding to this amount should be included in the endurance figure as well. Even if you're not supposed to use it, it can still be used in an emergency.
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grahamb
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I’m not keen on that approach. Like it or not, there are many pilots who don’t fully understand Part NCO and its definition of emergency fuel, and may be lured into thinking it’s some optional thing. Anyway, SD does nt know what consumption I’ve assumed when I’ve specified an amount of fuel in litres I may have specified my legal IFR 45 minutes using the required method and SD show it as a different calculated time. I would rather see the PLOG changed to show an endurance figure plus the emergency amount separately.
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lhe
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+xI’m not keen on that approach. Like it or not, there are many pilots who don’t fully understand Part NCO and its definition of emergency fuel, and may be lured into thinking it’s some optional thing. Anyway, SD does nt know what consumption I’ve assumed when I’ve specified an amount of fuel in litres I may have specified my legal IFR 45 minutes using the required method and SD show it as a different calculated time. I would rather see the PLOG changed to show an endurance figure plus the emergency amount separately. There are two different but related issues. - That the pilot understands how long it will take before the aircraft runs out of fuel - That the endurance figure in flight plans reflects how long it will take before the aircraft runs out of fuel
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F70100
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If there’s a line for Minimum Fuel Reserves in the fuel calculation, the user gets to decide how many litres to allocate for this use. The number of litres chosen will depend on the power setting / consumption rate, and the time that the fuel is required to last for. Both of these are decided by the user.
My motivation for raising this issue is that there is no obvious way in the SkyDemon fuel breakdown to account for Part - 21 minimum fuel reserves (or non Part - 21 recommended 30 minutes worth). I’m hoping that the SkyDemon team can find a way to introduce this.
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Tim Dawson
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We're implementing a Final Reserve fuel line in our next version, which I am pretty sure will be specified in minutes. In addition, it will be possible to reduce the existing (and somewhat anachronistic) Holding Time value down to zero.
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lhe
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+xWe're implementing a Final Reserve fuel line in our next version, which I am pretty sure will be specified in minutes. In addition, it will be possible to reduce the existing (and somewhat anachronistic) Holding Time value down to zero. That sounds great! Do note that according to part-NCO, the Final Reserve Fuel should be computed using the holding speed fuel flow. (Except for the unlikely special case where you are taking off and landing at the same airport, having it in sight during the whole flight, in which case you can use 10 minutes of fuel at the maximum continuous power fuel flow.)
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grahamb
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+x+xWe're implementing a Final Reserve fuel line in our next version, which I am pretty sure will be specified in minutes. In addition, it will be possible to reduce the existing (and somewhat anachronistic) Holding Time value down to zero. That sounds great! Do note that according to part-NCO, the Final Reserve Fuel should be computed using the holding speed fuel flow. (Except for the unlikely special case where you are taking off and landing at the same airport, having it in sight during the whole flight, in which case you can use 10 minutes of fuel at the maximum continuous power fuel flow.) Whereas the UK Part NCO regs state that FR fuel should be calculated based on ‘fly for at least 10/30/45 minutes at normal cruising altitude’
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lhe
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+xWhereas the UK Part NCO regs state that FR fuel should be calculated based on ‘fly for at least 10/30/45 minutes at normal cruising altitude’ Do you mean cruising altitude or cruising power? There is no single normal cruising altitude for the kind of aircraft typically used with SD. On the other hand, unless you have a turbine engine, the altitude would have very little (if any) effect on the holding fuel flow.
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grahamb
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+x+xWhereas the UK Part NCO regs state that FR fuel should be calculated based on ‘fly for at least 10/30/45 minutes at normal cruising altitude’ Do you mean cruising altitude or cruising power? There is no single normal cruising altitude for the kind of aircraft typically used with SD. On the other hand, unless you have a turbine engine, the altitude would have very little (if any) effect on the holding fuel flow. I've quoted the regs exactly as they are. Ask our CAA what they mean!
The difficulty with this sort of thing is that there are many scenarios which might drive a pilot to encroach into emergency fuel, so it's best to just use a sensible figure. Arrive back at airport and find runway obstructed temporarily* - fly at a speed for maximum endurance while you orbit overhead. Arrive back at airport to find that a glider has just had a fatal crash on the threshold* - fly at best range speed to an alternate (or a good field if that's your only option). Final Reserve fuel will last longer in the former scenarion that the latter.
Tim is taking a good step forward with SD by making this change, and it would be impossibly complex to try and accommodate every subtle nuance, expecially with regulations that diverge. I don't envy his job trying to keep everyone happy (and I don't envy the Regulators trying to come up with something realistic without it being over complex).
*BTW, both of these scenarios have happened to me, but I invariably carry significantly more fuel than I need, and certainly more than the regulations require, so encroaching Final Reserve wasn't a consideration on either occasion.
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F70100
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+x+x+xWhereas the UK Part NCO regs state that FR fuel should be calculated based on ‘fly for at least 10/30/45 minutes at normal cruising altitude’ Do you mean cruising altitude or cruising power? There is no single normal cruising altitude for the kind of aircraft typically used with SD. On the other hand, unless you have a turbine engine, the altitude would have very little (if any) effect on the holding fuel flow. I've quoted the regs exactly as they are. Ask our CAA what they mean!
The difficulty with this sort of thing is that there are many scenarios which might drive a pilot to encroach into emergency fuel, so it's best to just use a sensible figure. Arrive back at airport and find runway obstructed temporarily* - fly at a speed for maximum endurance while you orbit overhead. Arrive back at airport to find that a glider has just had a fatal crash on the threshold* - fly at best range speed to an alternate (or a good field if that's your only option). Final Reserve fuel will last longer in the former scenarion that the latter.
Tim is taking a good step forward with SD by making this change, and it would be impossibly complex to try and accommodate every subtle nuance, expecially with regulations that diverge. I don't envy his job trying to keep everyone happy (and I don't envy the Regulators trying to come up with something realistic without it being over complex).
*BTW, both of these scenarios have happened to me, but I invariably carry significantly more fuel than I need, and certainly more than the regulations require, so encroaching Final Reserve wasn't a consideration on either occasion. Both those scenarios make the case for separate fuel allocations:
Want to wait for a runway which is temporarily obstructed to be cleared? Use Holding Fuel. Find that your planned destination is going to be closed for some time? Use Alternate Fuel. Of course, Non Commercial Ops don't require Holding Fuel or Alternate Fuel but if you want to cover the risk that these scenarios present, fuel for that should be extra to Minimum Fuel Reserves.
I fully accept that most of this is semantics. In the NCO world, people rarely operate on minimum fuel. The economies that commercial operators gain by doing so are not really relevant in the NCO world. I'm pleased though that Tim and the team are changing the fuel planning terminology in SkyDemon to reflect what Part 21 requires.
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lhe
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+xOf course, Non Commercial Ops don't require Holding Fuel or Alternate Fuel but if you want to cover the risk that these scenarios present, fuel for that should be extra to Minimum Fuel Reserves.
Actually they do. The relevant parts of NCO.OP.125: The pilot-in-command shall ensure that the quantity of fuel/energy and oil that is carried on board is sufficient, taking into account [...] any delays that are expected in flight [...]
And a non-commercial IFR flight generally needs an alternate.
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Tim Dawson
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The way we work out the fuel burn for the "holding time" part of the flight, and the new "final reserve" part is to look through all the power settings for the aircraft and find the one with the lowest fuel burn, and we assume that's the one you'll be using if waiting around. We multiply that by the number of minutes defined.
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