Hi Bob,

I was working through the text book and couldn't find any information regarding the use of TEMPO and INTER with the PNR calculations. Obviously having a TEMPO or INTER would require holding fuel - which isn't included in the flight fuel but does the holding fuel apply just for the destination or also for the departure aerodrome. I'm assuming you are not 'planning' to return to point A therefore would only require holding fuel for point B if there was a INTER or TEMPO requirement...

Can you please confirm?

Thanks.

When you are calculating a PNR you ARE planning to return to the departure aerodrome. Your departure aerodrome IS your destination. The PNR calculation tells you how far away from your departure aerodrome you can fly with a given amount of fuel and still return to the departure aerodrome. The destination has nothing to do with the calculation of the PNR. The only things that matter are the amount of fuel you have on board when you leave, the TAS and the wind component along track.

Apart from the wind and the TAS, the ONLY thing that matters when calculating the PNR is the fuel you have on board when you start up at the departure aerodrome and it doesn't really matter where you are planning to go, since the PNR is assuming that you are returning to the departure aerodrome. Any holding at the departure aerodrome must be taken into consideration because you may need it if you have to return.

If the planned destination requires holding, you would have to carry that extra fuel but, apart from that, it is of no interest in the calculation of the PNR.

Bob

Hi Bob.

I have since passed performance but was thinking of another scenario.. what if you departure aerodrome had a PROVN forecast, and you are calculating a PNR, would you have to do your PNR to another point?

Edited

Yes, you are missing something.

First you must remember that the calculation of a PNR considers only the total fuel on board at take-off. As far as the PNR calculation is concerned, there is no destination - you are flying to the furtherest point from which a return to the departure aerodrome can be made with all reserves and allowances in tact. Those allowances must include any holding that applies to the departure aerodrome.

However, the actual amount of fuel on board on departure for the proposed flight would have to include any holding or alternate requirements for the proposed destination. So if your destination required holding or an alternate, you would have to allow for that in your flight planning. So the total fuel on board at take-off would include that extra fuel.

So, if the destination required holding or an alternate, the calculated PNR would be further away from the departure aerodrome than it would otherwise have been. It could even be possible, if you departed with much more fuel than you required for the proposed flight, that the PNR could be beyond the destination. In this case, there would effectively be no PNR because you could fly all the way to the destination and still return to the departure point with fuel to spare.

Bob

Thanks Bob!
I was just getting very confused and really overcomplicating the situation!
The key sentence: "As far as the PNR calculation is concerned, there is no destination".
No matter what the destination forecast is, it doesn't matter because all we are considering is the fact that if we need to get back home, we can.
I do have one question though, what if the destinations weather is worse than the departure aerodrome? Technically, when conducting a normal flight plan and provisions, we would need to deduct reserves for it, but when figuring out the PNR, this is disregarded, because all our intention is, is to get back home if something goes wrong. Is this correct? (I hope so!)

Just remember that whatever the destination weather might be, you will need to allow for any operational requirements during your initial flight planning. When you know how much fuel you will have on board on departure, you use that figure to calculate the PNR. The PNR is a completely separate calculation which is done after you have decided how much fuel you will be carrying.

STEP 1....Plan the flight to the destination considering any OPRs that may apply.
STEP 2....Determine the fuel that will be required to conduct the flight to the destination.

STEP 3....As a completely separate calculation, determine the PNR using the fuel figure arrived at in Step 2.

Ok, I think I've got it now.
Question 12 in the text was confusing me because it is asking to calculate the PNR with the tanks at 145 gallons. So what you're saying, if I'm understanding you correctly, is that the 145 gallons at start up has taken the INTER at BRAVO into consideration already. This allows us to calculate the remaining total fuel (minus the reserves, taxi and holding for ALPHA) for working out the PNR which will include that INTER fuel allowance for BRAVO as like you said earlier (there is no destination), even though that allowance has been made when planning the flight initially.
Am I getting warmer?