MarkW

Calculating correct Reserves

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Here is my PFPX fuel plan.  My question is based on these numbers below, what is the appropriate value to put in the PERF INIT page reserves ?

 

FUEL CORR ENDUR
TRIP 69393 ........ 02:58
10 PCT 6666 ........ 00:18
ALTN KFLL 12063 ........ 00:29
INTL HOLD 10826 ........ 00:30
MIN T/O 98948 ........ 04:14 .....................................
EXTRA ...... ........ ..... 
TAXI 1000 ........ 00:10
RELEASE 99948 ........ 04:24 
ARR FUEL 29055 ........ 01:11

I would normaly add the 10 PCT, ALTN, HOLD to get 29,555 Kgs but if you enter this value you always get a message saying Insuffient Fuel.  

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Hi Mark,

You can put any figure you want in there as the idea is simply to flag up if the predicted fuel at destination falls below that value.

Conventionally you would want to put in the final reserve (which doesn't seem to be in your fuel plan? About 30 minutes -- around 4.5 tonnes) plus the alternate fuel. This will then flag up if you are expecting to land with less fuel than you need to get to your alternate.

If you do decide to divert you would then want to change that to your final reserve figure.

Everything else is fair game to be burnt.

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Thanks Simon, this is using the default PFPX format, I do have the BA one as well from BAV but did not use it in this example....no sure why it does not have the final reserve fuel listed.

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Looking again, I think the final reserve is what PFPX has labelled "INTL RESERVE".

So in this case it your reserve figure would be INTL HOLD (10826lb) plus ALTN KFLL (12063lb) for a total of 22,889lb.

Next time you use the CIRRUS format plan you'll see there is a TOT RES figure which is calculated as above to save you the maths :)

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Okay, I realize I am posting on a dated thread but have a question that is in the same ballpark as this one so rather than start a new I'd like to know the following,,,,

When putting a value into the reserve such as 2.0 what is that value representing? I've seen tutorial videos where they say 2 tons, 2000lbs, 2000kg or 2% of total capacity what is it it exactly? Thanks in Advance.

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6 minutes ago, Blaze said:

Okay, I realize I am posting on a dated thread but have a question that is in the same ballpark as this one so rather than start a new I'd like to know the following,,,,

When putting a value into the reserve such as 2.0 what is that value representing? I've seen tutorial videos where they say 2 tons, 2000lbs, 2000kg or 2% of total capacity what is it it exactly? Thanks in Advance.

Depends on your units setting in the options.  If kg then 2 is 2x1000 kg or 2T.  If your option is lbs then 2 is 2x1000 lbs or 2000 lbs.

Your question is not in the ballpark..., maybe the parking lot. No problem. Stay away from tutorials, use the documentation that comes with the product and feel free to ask here where to find info.

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Used the search feature to try not to post a new/duplicate thread, this was the closest I saw so I asked.

Thanks for the answer Dan.

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Hi,

Simon is right, the reserve value that you should enter in the init ref page is the sum of the absolute minimum reserve (30' flight) + the alternate fuel.

That reserve value gives you the minimum you should at least be expecting when you reach your destination airport. If you find on your way to your destination airport that you may go below the reserve value, you'd better start thinking of a backup plan (diversion to another or to the alternate airport, turn back to your origin airport...).

If I'm not wrong you may go below that value in some particular cases but never go below the absolute minimum fuel reserve or you may faces some legal troubles. :wink:

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52 minutes ago, Budbud said:

If I'm not wrong you may go below that value in some particular cases but never go below the absolute minimum fuel reserve or you may faces some legal troubles.

Not according to FAA regulations, maybe company policy but legally you can burn any of the 30 or 45 min reserve you are carrying... that's why it is there, it is for contingency.  Unexpected delays due to traffic, weather or incidents come to mind.  Afterall, most delays are in the terminal environment and it is not unlikely that delays can eat into much of the reserve. That is what the alternate is for.

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I can't speak for the FAA, but in EASA land it is the PIC's responsibility to ensure that the aircraft touches down with the 30 minute final reserve intact and to take steps to ensure that is the case. Perhaps 'legal problems' is a bad way of describing it, but if at any point it becomes apparent that landing with final reserve is not going to be possible then that is a MAYDAY and, essentially, land ASAP.

Yes, it is there to be burnt in the event of an emergency: but certainly not to be planned/expected to be used routinely in the event of delays etc and if it is dipped in to that implies something has gone very wrong somewhere along the line.

Touching down with less than 30 minutes in the tanks would require an MOR with accompanying investigation to establish why it happened and how it could be prevented in future.

Under normal circumstances you should touch down at your destination with at least final reserve + alternate fuel if all has gone well. In the event of a diversion if you have not put any extra on then you should touch down at your alternate with at least final reserve fuel.

You can legally burn the 5% (or whatever) contingency fuel at any point.

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30 minutes ago, skelsey said:

Under normal circumstances you should touch down at your destination with at least final reserve + alternate fuel if all has gone well. In the event of a diversion if you have not put any extra on then you should touch down at your alternate with at least final reserve fuel.

This is where the FAA FAR Part 121 and you do not exactly line up.  The contingency varies with US Domestic or International policies but the wording is essentially the same.  There must be enough fuel to fly to destination, then to alternate and then (in the case of US Domestic) fly for an additional 45 min.  The FAR does not specify how much fuel you must have on board when you land.  This does not superseded such operational considerations as minimum desired fuel on board for mechanical  or company policy of course. But the law is coming after the pilot if he lands with less than the planned minimum.

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Not sure if it is handled as a mayday in europe but definitely with a high priority, panpan at least, if you touch your min res. It has happened in EDDM in the past that airplanes were sent to hold late in the evening for ages and then had to panpan to be pulled out of the holding before running out of fuel. Pilots were assaulted for mismanagement but under the line it was Munich that had not enough controllers to handle the late approaches... money money money... 

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For a long time (years) I set Reserves=5.0 and Cost Index=85 in all PMDG planes (747 v2, 747 v3, 737NGX and 777) for any flight plan. Never had side effects. I wonder if I am wrong ….

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Posted (edited)
1 hour ago, trisho0 said:

For a long time (years) I set Reserves=5.0 and Cost Index=85 in all PMDG planes (747 v2, 747 v3, 737NGX and 777) for any flight plan. Never had side effects. I wonder if I am wrong ….

It's simple and works for you, but you are missing out on a valuable management tool.  I use the amount of fuel that the flight plan projects will be remaining if I don't use any contingency or rerouting, and therefore if the fuel remaining message appears it acts as a precautionary notice to take a look at what's trending.  Perhaps the winds are not as favorable, or there is a mechanical/performance issue. Often I'll see the message early in the flight during climb to cruise, where I ignore it and it goes away once established in cruise.  Regardless, things are not as planed and it's good to know why.  It's a simple matter to adjust the reserve value on the PERF page to accommodate whatever is going on, for example I might change it to a lower amount that leaves me with 45 min reserves if the winds are unfavorable.

CI 85 is different in the 737 than it is in the 747 or 777.   I'll use 40-80 in the Queen and often use 220 in the 777. These aircraft have different CI ranges.... most of my B736 BBJ flying is CI=80 (very fast), but if I'm flying an airline route I'll dial it back to 35-45 in the NGX.  Again, you're not wrong but you have simplified the process to make it extraneous to mission accomplishment.

Edited by downscc

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On 1/22/2018 at 12:31 AM, downscc said:

This is where the FAA FAR Part 121 and you do not exactly line up.  The contingency varies with US Domestic or International policies but the wording is essentially the same.  There must be enough fuel to fly to destination, then to alternate and then (in the case of US Domestic) fly for an additional 45 min.  The FAR does not specify how much fuel you must have on board when you land.  This does not superseded such operational considerations as minimum desired fuel on board for mechanical  or company policy of course. But the law is coming after the pilot if he lands with less than the planned minimum.

Dan, I was about to write a long post about why you where wrong in your interpretations of the FAA regulations. I have both a FAA and an EASE CPL, and it has been my understanding that the 45 minutes of reserve fuel had to be in the tanks upon landing.

But, before clicking submit, I did some research and found this document written by the FAA:
https://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/info/all_infos/media/2008/info08004.pdf

According to this document there are no requirements in the regulations that may not use any of the 45 minutes of fuel for unforeseen circumstances. Companies themselves can of course have stricter procedures in place. So unless I have misunderstood something, there appears to be a difference between FAA and EASA when it comes to fuel requirements.

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Posted (edited)

That's an interesting bulletin I've not seen, thanks Marius.  It reminded me of the time I had to declare "minimum fuel,"  in an AF Aero Club Arrow landing at Scott AFB  picking up ice on my leading edges while the controller there were notorious for holding aero club aircraft on an extended downwind if there was "real traffic" within 40 miles.  We exchanged some words once I was on the ground because I was getting near empty.  The "emergency fuel" declaration was a pretty common thing among F-4's landing at Ramstein AB... those birds have enough fuel to get them on target and back home with minimum delays... if four or five of them stacked up waiting their turn on the GCA at least one of them would go "bingo" which was the term used to mean they need to land or punch out.

Edited by downscc

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4 hours ago, downscc said:

aiting their turn on the GCA at least one of them would go "bingo"

Dan,

In SE Asia I have been 10 minutes into a 20 minute fuel light on a GCA to minimums into Phu Bai or Da Nang on several occassions. Not something to be proud of but it came with the territory.  I swore that when I got back to the "World" I would never put myself in that position again. 🙂

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23 hours ago, downscc said:

It's simple and works for you, but you are missing out on a valuable management tool.  I use the amount of fuel that the flight plan projects will be remaining if I don't use any contingency or rerouting, and therefore if the fuel remaining message appears it acts as a precautionary notice to take a look at what's trending.  Perhaps the winds are not as favorable, or there is a mechanical/performance issue. Often I'll see the message early in the flight during climb to cruise, where I ignore it and it goes away once established in cruise.  Regardless, things are not as planed and it's good to know why.  It's a simple matter to adjust the reserve value on the PERF page to accommodate whatever is going on, for example I might change it to a lower amount that leaves me with 45 min reserves if the winds are unfavorable.

CI 85 is different in the 737 than it is in the 747 or 777.   I'll use 40-80 in the Queen and often use 220 in the 777. These aircraft have different CI ranges.... most of my B736 BBJ flying is CI=80 (very fast), but if I'm flying an airline route I'll dial it back to 35-45 in the NGX.  Again, you're not wrong but you have simplified the process to make it extraneous to mission accomplishment.

Many thanks for your great help! I will see what I get then with CI 40 for 737NGX but keeping Reserves 5 right? Also, CI 220 for the 777 not too high?

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There have been some very interesting points raised in this discussion and if I didn't know any better I would now be very confused as to what my Reserve Fuel actually is.

By keeping things simple we are less likely to get caught out, so it is important that we always use the correct Reserve Fuel figure as calculated in our Fuel Flight Plan and not, as some have already suggested, use whatever 'tickles our fancy' or change it later if we divert (this is what Contingency Fuel is for; i.e. to cover unforeseen variations from the planned operation and it is this fuel that can all be used up at any time after aircraft push-back or engine start)

Reserve Fuel is a planned fuel figure and it is defined as the minimum fuel required to be remaining in tanks at a normal landing.

However, this definition may vary depending on the Authority's Regulations (e.g. FAA) under which the aircraft is operating and it may also depend on type specific factors, such as an allowance for unreliable or unuseable fuel, gauge configuration errors etc.  For example, in the UK Reserve Fuel is calculated as the quantity of fuel required in the tanks equivalent to holding at the Alternate (or the Destination if no Alternate is available) for 30 minutes at the planned holding weight, with the aircraft clean at 1,500ft AGL.  So, if you are landing at your normal Destination with an Alternate available you should expect to land with at least your Diversion Fuel plus your Reserve Fuel (you might have some or all of your Contingency fuel as well).

Bertie G 

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Reserve and Cost Index are calculated for emergency fuel too? If so, that is the reason why my birds never had side effects with my settings as Reserve 5 and Cost Index 85. I did Reserve 5 and CI 220 with PMDG T7 and found no differences. I have to mention that I use ILS landings. Barely I do manual landings (I need more practice).

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57 minutes ago, berts said:

it is important that we always use the correct Reserve Fuel figure as calculated in our Fuel Flight Plan

I am new on this step. How do you calculate? Is it explained in the manual? If so, what page?

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Posted (edited)
13 hours ago, trisho0 said:

Reserve and Cost Index are calculated for emergency fuel too

I use the minimum legal reserve for my Reserve setting on the scratch page PERF INT.  Some captains use more, it's a personal preference thing and only a reminder.  I never leave operations until I'm happy with the planned fuel for the flight.  The last thing I want to do is have to file an ASRS or have my heels locked in front of the CP's desk because the fuel got screwed up. 🙂

The cost index used is the one flight planned.

Edited by Bluestar

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4 hours ago, Bluestar said:

The cost index used is the one flight planned.

Please, can you detail? When I do flight plan I enter FMC info Departure/Arrival and waypoints accordingly. But, for CI input I use 85 for 777 - 747 and 40 for 737NGX, leaving entered Reserves at 5 for all PMDG planes. I learned also I should enter CI 220 just for 777 but either entries work for me. 

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On ‎1‎/‎21‎/‎2018 at 4:57 PM, skelsey said:

Under normal circumstances you should touch down at your destination with at least final reserve + alternate fuel

Simon,

One of the real world problems that is not a problem in flight sim is fuel density.  Ten thousand gallons of Jet A may weigh 69,000 lbs. in one corner of the world, but it may only weigh 65,000 lbs. in another part of the world.  That difference can make a substantial difference in range. 

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