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EspressoDan created the topic: PNR and holding fuel
I have been given some advice about PNR and holding fuel that I am unhappy with - can I check your view?
The scenario. You leave on a PNR flight. The TAF at origin is fine, the TAF at your intended destination has an INTER, which includes your arrival time, of SCT010.
Now, the question was - do I need holding fuel. The advice was 'No, PNR is just interested in your departure, which is also your destination.'.
However, CAAP 234-1 clearly states, in the definition of PNR, that it is "The last possible geographic point at which an aircraft can proceed to an available en-route alternate (ERA) aerodrome for a given flight. It is the point beyond which diversion to the en-route alternate aerodrome is no longer possible and the PIC is committed to proceeding to the destination aerodrome."
Therefore, when you hit PNR and chose to proceed, your departure is not your destination. Your destination is, and in this case you have no alternate and there is an INTER below VFR minima, therefore I believe that 30 minutes of holding fuel is still required.
Am I right or wrong?
I clarified this and it's worth a note of caution. We were both wrong but one of us moreso than the other.
It is correct that, for a PNR calculation alone (which is not a fuel calculation, just a PNR) you do not need the additional holding fuel. However, the person with whom I was speaking, who has only recently acquired his licence had got himself very confused and had given himself the impression that you did not need the additional fuel at all - he had done too many theoretical 'trick questions' and these had clouded the practical side.
If you're going to an aerodrome where the weather is below VFR minima you still need an alternate or may carry holding fuel for the INTER or TEMPO. You cannot throw it away because you're on a PNR. It's more important in those cases, not less! You just do not need to consider the fuel in the PNR calculation IF your departure (and pre-PNR alternate) are above VFR landing minima.
The PNR has nothing to do with the destination. If the destination required holding you would have included that in the fuel you loaded before take-off. Nobody said that you are going to 'throw that away'. You have planned for it so that you will be covered IF you do not decide to return to base from the PNR and continue the flight as planned. However, when you calculate the position of the PNR you begin with all of the fuel in the tanks including the holding fuel for the destination.
The fuel used for the PNR calculation is simply the total fuel on board, when you dip the tanks, minus the fixed reserve minus any holding at the base aerodrome, minus the taxi fuel then divided by 1.1 to remove the variable reserve. If you do decide to return to base. you will not be going to the destination so you wont need the destination holding fuel. You can't do both.
A PNR simply tells you how far you could fly from base and still return to base with all reserves and holding fuel that applies to the base aerodrome. Holding at the destination was included in the original flight plan, but it's not a consideration in the PNR calculation. If you return to base from the PNR you will not be holding at the destination.
EspressoDan replied the topic: PNR and holding fuel
It turns out we were talking across purposes. Yes, a PNR does not take the weather a the (intended) destination into account. I had got myself confused though because the fellow with whom I was speaking was insistent that "you don't need holding fuel for a PNR if the departure is in limits", in that he had the impression that for a PNR you NEVER need holding fuel.
It turns out that, because he had been doing these questions to check that he understood what PNR was he had formed the impression that you didn't need holding fuel at all when using a PNR "because your origin is your destination". The problem is that at some point in a PNR you get to the NR bit, at which point, if your destination is above VFR landing minima save for a TEMPO or INTER, you do need holding fuel in the tanks for the general trip fuel calculation.
Just an interesting effect of answering a lot of exam questions that don't always work the full scenario through to the conclusion.
shaungandrews replied the topic: PNR and holding fuel
This is a scenario I seem to struggle with a little. Is my understanding of the following correct?
Given a situation where you plan fuel loading for a trip from A - B, the weather forecast requires 60min holding due TEMPO at Bravo. When calculating a PNR, the holding fuel planned for Bravo then becomes part of safe endurance fuel for your 'destination' at ALPHA since you no longer need it for landing at BRAVO?
That's correct. The PNR considers only the flight out to the PNR and back to Alpha, Bravo has nothing to do with the PNR calculation. If Bravo did require holding, you would of course consider it in your original flight plan as part of the fuel on board at take-off. But the actual PNR calculation considers only the flight out to the PNR and back to the departure point.
I have come across a PNR question that included a TAF at Departure aerodrome that was similar to stating:
For ease it is fine until 1606-16/12 where there is a TEMPO for storms. IE holding fuel for 60mins in a PNR.
The bit that got me was that the arrival was planed for 16-1230 at bravo. doing the Wind and GS that made for a departure of say 1020 at alpha. this placed you right in the middle of the TEMPO window for planning 0530-1230. The actual answer did not include the TEMPO holding required fuel. if it was not include the PNR was 1.7 hours from Alpha and a return would be outside the TEMPO but at a time before that it would be as you should legally have the HOLD fuel?
Is there a rule of thumb or just purley what would be the total time out and back to the PNR and what would be the arrival time?
If you were given a TAF for the departure aerodrome and a departure time, you would calculate the time to the PNR plus the time to return from the PNR to the departure aerodrome. That would give you an ETA for the return flight to the departure aerodrome. If that happens to be during the currency of an INTER or TEMPO on the departure aerodrome's TAF, then you would have to take that fuel out when you calculate the trip fuel available for the PNR calculation. At no point would the destination need to be considered because, when you do a PNR, you are planning to return to the departure aerodrome - so the departure aerodrome is your destination.