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TripleDelta
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Fuel Reserve Question

Sun Aug 29, 2004 6:42 pm

All aircraft carry more fuel than needed for a route, as a reserve should they have to divert to an alternate airport or otherwise. As far as I understand it, the amount of reserve fuel is measured in minutes of flight provided by it (say, an airliner has 45 minutes of reserve fuel). However, I'm wondering, this is calculated by what fuel flow figures? I'm assuming full throttle at sea level i.e. the maximum burn that the engines can achieve, but I need confirmation on that. Any info is welcome  Smile
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Spitfire
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RE: Fuel Reserve Question

Sun Aug 29, 2004 7:03 pm

The fuel to be put on board is calculated like this (may vary from a:c to a:c or company, etc...)

Taxi fuel (from start up to holding point)
Trip fuel ( take off, climb, cruise, descent)
Approach and landing fuel (depends on IFR or VFR approach)
Contingency fuel (5% or 2% of trip fuel, depends of company fuel saving policy)
Diverting fuel (go-around, climb, trip to diversion, descent, approach and landing fuel)
45 min of reserve fuel for holding above the diversion at 1500 AGL and holding speed.

I hope this can help you.

Rgds
Spitfire
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411A
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RE: Fuel Reserve Question

Mon Aug 30, 2004 6:48 am

The above is, shall we say...not correct, according to regulations with most European/Asian carriers.

Taxi fuel.

Takeoff, climb, cruise, descent, approach and landing fuel.

Contingency fuel...usually 5% of the total fuel burn above (subject to re-release requirements).

Diversion fuel, normally calculated at the long range cruise TAS/mach number, including approach/landing at the alternate.

Holding fuel, at 1500agl above the alternate, for a 30 minute period.

US/European,Asian requirements are definitely different.
In addition, company requirements shall NOT be less than the above.

It must be recognised that some regulatory authorties view these requirements differently...ie: one size does NOT fit all.
 
rendezvous
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RE: Fuel Reserve Question

Mon Aug 30, 2004 7:31 am

Can airlines "cheat" with the fuel reserve? For example if you have a flight that goes from Singapore to Los Angeles and overhead Honolulu. Is it possible to carry only 5% reserve for the Honolulu - Los Angeles section? I'm not assuming a stop in Honolulu, but if you use the total fuel for the entire trip, then you have more than enough for Singapore - Honolulu plus 5% reserve for that. When you get to Honolulu you could have enough for Honolulu - Los Angeles plus the 5% reserve for that section. It would mean less fuel being carried than Singapore - Los Angeles plus the 5% reserve for the whole flight.
 
Goldenshield
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RE: Fuel Reserve Question

Mon Aug 30, 2004 8:31 am

I'm going to assume this for a US flag carrier, as I haven't read any other countries regulations.

Say we have a United flight going on the above mentioned SIN-LAX nonstop. Being that they are operating a flag flight, the flight must:

Have enough fuel to reach the destination on the route planned, then; have enough fuel to fly 10 percent of the planned route, then; be able to fly to the futherst alternate, and; fly for 30 minutes above the farthest alternate ( or the airport of intended arrival, if no alternate is necessary) at 1,500 feet above the airport.

So, to answer your question, Rendezvous, what you suggested is not possible, as you must have contingency fuel for 10% of the total planned trip, per US federal regulations. This will definately be different in other countries, but you get the gist of it. Big grin
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PhilSquares
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RE: Fuel Reserve Question

Mon Aug 30, 2004 8:41 am

Not quite true. What carriers do is use a "redispatch release"

Using the above example SIN-LAX. The original release might be SIN-HNL, using HNL as the re-release point. Once the flight approaches the re-release point, the crew and dispatch coordinate a new release. Not the 10% is calculated on the HNL-LAX segment. All the other reserve requirements stay the same.

If the fuel at the re-release point isn't at or above the minimum required, then the flight is required to land at it's original release point.

When flying from the US to Asia, I have seen a double re-release flight plan used by several US carriers. This is rare and I have only seen it used by the older 747 classics. However, on the 744 a single re-release point isn't uncommon.
Fly fast, live slow
 
Goldenshield
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RE: Fuel Reserve Question

Mon Aug 30, 2004 9:14 am

I'm still not a certified dispatcher yet, but I'm learning. Big grin

With your experience, I will not argue on that point. After browsing though 121 subpart U though, I could not find anything regarding this, so it could be an under-the-table type thing? It would certainly save quite a bit of fuel not having to carry that required 10% for the whole trip, and instead having 10% of the SIN-HNL portion, which in turn would only add up to 5% of trip length in a double release situation.
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OPNLguy
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RE: Fuel Reserve Question

Mon Aug 30, 2004 9:23 am

>>>After browsing though 121 subpart U though, I could not find anything regarding this, so it could be an under-the-table type thing?

Check out 121.631...

Also, everything you could want to know about the general subject (US FARs) can be found at:

http://www.faa.gov/avr/afs/faa/8400/8400_vol3/3_006_04.pdf

There are several examples given...
ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 
PhilSquares
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RE: Fuel Reserve Question

Mon Aug 30, 2004 9:39 am

As mentioned FAR 121.631 covers what I was talking about. A more real world example would be JFK-NRT. Normally the re-release point is a waypoint west of ANC. The original release is to ANC via that waypoint. As you approach that waypoint, if your fuel is at or above the minimum for re-dispatch and the weather is suitable at NRT and the required alternates, you continue. Otherwise, you turn around and divert to ANC.

For your ATC flight plan, it is JFK-NRT. Normally, you know early enough so you don't go all the way to the waypoint, turn around and divert into ANC. Generally, things are coordinated while you are over Northern Canada. A divert into ANC for fuel, if properly coordinated can take less than an hour. I have seen it as quick as 45 minutes.
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Goldenshield
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RE: Fuel Reserve Question

Mon Aug 30, 2004 9:42 am

A very interesting read indeed. Is it safe to assume then, that the redispatch point is somewhere along the lines of 10-20 minutes prior to the letdown point of the intermediate destination?

121.631 is a very cryptic read as far saying "redispatch point."
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PhilSquares
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RE: Fuel Reserve Question

Mon Aug 30, 2004 10:51 am

I wouldn't say the re-dispatch point is 10-20 minutes prior to the letdown point. For example on a JFK-NRT/SEL flight, I have seen the re-dispatch point anywhere up to two hours west of ANC.
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Spitfire
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Fuel Reserve Question

Mon Aug 30, 2004 5:12 pm

Sorry, my mistake....holding fuel: 30min , that's correct.

There are also other ways to caculate fuel needed. But this is a little bit more complex to explain here. You can have " reclearance in flight", "without alternate available",etc...

Spitfire


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