Fuel at destination

[Peter47]

Out of interest, and as an enthusiast, not professional, I'm looking at ultra long haul flights and wondering the maximum length that is achievable with a viable payload. Could someone answer the following for me:

What is the minimum fuel required at the destination airport before diverting? Presumably it is enough to reach the nearest alternate with suitable weather plus enough for a go around. I presume that this could be as low as 30 minutes if the alternate(s) is/are nearby.

How often is tactical reclearance used? For example, a flight from Dallas to Sydney may be filed to Brisbane and then "diverted" to the advertised destination if the en route contingency fuel is not used. Is is used much?

How accurate are flight plans? (Its interesting how the eta indicated on the moving map always seems to change up or down by around 10 minutes on every long haul flight. I suppose it depends upon traffic en route (optimum altitude & routing, etc) together with whether head or tailwinds are correctly forecast and the runway used.

Is it possible for an airline to "swap" flights in the hold? For example I've heard stories of flights arriving at their destination with only ten minutes fuel (newspaper speak, I think that they meant ten minutes before having to divert). Other, short haul flights might not be so fuel critical and could easily cope with a delay. (Obviously this would work at the airline's hub, you might need a reciprical arrangement at an outstation).

In other words, for UHL flights how low a level of reserve fuel can you get away with before offloading SLF?

I have a historical timetable in my collection that quotes a block time 14:40 for a 747-200 from HKG - LHR. (This was before the 744 & China granting overflying rights). Did it ever leave with a full passenger load?

[wiggy]

In other words, for UHL flights how low a level of reserve fuel can you get away with before offloading SLF?


TBH your diversion fuel and 30 minute reserve are fixed..you are generally not at liberty to lower them. Back in the day (around the time of the HKG you are looking at ) there used to be various opinions as to whether or not you could reduce contingency fuel to get people on - in the days when contingency was often a fixed 5% of trip fuel you had a lot of flex..your contingency could be 6 or 7 tonnes....these days with statistical contingency fuels your margins are much tighter and there isn’t the wriggle room to reduce anything.

[Duchess_Driver]

There will be company “minimums” as well as regulatory final landing fuel. It is not often the two are different these days. In addition, the contingency fuel is at the discretion of the commander to load what he feels based on..... and then “some for granny.”

As for estimates, that’s exactly what they are, based on planned winds and altitudes with both forecast and historical wind data to give a rough (but good) estimate of trip burn. However, winds are never as forecast and often ATC will give a different altitude to that planned. All of which cause burn and time differences. Sometimes we have to plead with ATC for higher levels as the assigned level against plan starts to look “not so clever.”

Usually, on our trips, planned burn is often within a couple of hundred lbs of plan. But we monitor it regularly and when the calculated landing fuel starts to trend away from plan we’ll re think as appropriate.

[Atlas Shrugged]

Legally, all that is needed is to have 30 minutes of fuel remaining at the end of the landing roll. It may vary slightly, but generally not very much.

Fuel requirements vary depending upon whether you are at the planning stage or in actual flight. Different airlines will have their own planning methods but typically it's:

A fixed reserve - 30mins
Approach fuel - to get from 1,500' to end of the landing roll
Flight fuel - from the start of take off roll to 1,500' at destination.
Taxi fuel - from the gate to the end of the runway.
Variable reserve - 10% of the flight fuel
Holding fuel - for nominated ATC holding.
WX holding fuel - to cover any TEMPO or INTER where the weather is below the nominated holding criteria.
Diversion fuel - if the WX holding periods exceed the ability to hold.

When in flight things change and all you need is:

1) Fuel to go somewhere (anywhere)
2) 10% of (1)
3) Approach fuel
4) Minimum reserve
5) WX holding AND but not always, ATC holding
6) Alternate fuel, but only if you can't manage (5)

There is no requirement whatsoever to routinely carry an alternate.

In some places there might be perfectly acceptable airports within only a few miles and the alternate is almost in the circuit - Heathrow/Gatwick/Stansted for example. In such cases you can have an alternate, basically without carrying any extra fuel although these are not 'real' alternates as they are almost certain to have exactly the same weather conditions.

In contrast, on a Pacific crossing, if you take somewhere like Tahiti, which is the only decent runway within a very long way, you cannot reasonably carry an alternate so generally there's some form of remote fuel allowance which might be something like 90 minutes of holding on top of anything else that might be required.

On arriving at destination you could have enough fuel to fly to an alternate 200 miles away, but if you're held for any length of time that alternate option will disappear. You might still be able to carry a closer airport, but eventually, you'll be left with one choice. Managing when to hold and when to divert and more importantly if you'll let options disappear.

If for whatever reason you cannot consider one place, then another may be of interest. The option to go to somewhere may exist right to the gate or it could disappear whilst airborne. There really is NO fixed answer.

[Harry Wayfarers]

In my day I recall it was something like an approach or two, 45 minutes holding, enough to get to No.1 alternate and a 5% contingency for luck.

Had an interesting one last year in my neck of the woods with my local airport (concrete strip) being IAO, both flights had departed CEB with an Air Philippines Q400 5 minutes behind a Cebu Air ATR72, at IAO there are no navigational aids, no lights, no radar, no fuel and a short runway that I still reckon is questionable in length for a loaded Q400.

The approach procedure is that they fly over the top before circling to land and with no radar they can have only have one A/C doing this at a time so the Q400 was told to hang around for some 10 minutes whilst the ATR72 came in, needing to carry round-trip fuel combined with a short runway the Q400 didn't have sufficient fuel to hold for even 10 minutes and diverted back to CEB, whatever reserves they were required to carry they were planning that same amount of fuel twice, for IAO except that whilst legal they couldn't use it because they needed that fuel for their reserves back to CEB.

[wiggy]

As people say it's operator/regulator dependant - for the sake of the question about HKG-LHR the basic rule set for one of the 747-200 operators operating too/from, the far east in the late 80s was, at the planning stage..loading /offloading SLF stage :eek:

At start Fuel in tanks >= the sum of:

Taxi (out) fuel.
Trip fuel ( departure to destination)
Contingency fuel ( usually 5% of trip fuel)
Diversion fuel ( typically LHR-LGW from the go-around, if LGW weather was OK).
30 min reserve...

Reclearance was an option, routine use of 3% contingency by use of a nominated en-route alternate came in I think in the 90's...

A much current 747-200 operator will be more up to date on the exact numbers for fuel than I now am but I'd have a rough punt from memory that your 30 min reserve could be 5-6 tonnes, div fuel (LHR-LGW) ?3 or ?4 more.. .very open to correction.

[condor17]

P47, think you have several valid answers to choose from , Here may be a few more thoughts .
Modern a/c generally have much better payload/range than older types , so the need for exploring the edges of the fuel rule book is much reduced .
Some of the techniques used are ...
HKG non stop LHR in the early days , and even SIN-LHR in a recent 744s , can be payload limited in strong headwinds .
Some pax and freight would be Weight [ not wait ] limited . Thus on the day with light winds they could be got on , other days freight and standby pax would be offloaded to enable enough fuel wt to be loaded for a non-stop service .
Another technique is to replan in flight ... 25yr old Tristar -100 with 393 pax Bahrain - Gatwick , winter , thus strong headwinds . we'd leave perhaps 5000kgs of fuel short of flight plan . ATC flight plan stayed to LGW , our fuel plan to Cyprus -div Athens .. Climb well and get a short cut , optimum level , best range speed , burn contigency in flight . Shame the opposite direction RAF Tristar had to dump fuel to get to landing wt ! If we'd had a probe we could have had it . Approaching Athens fuel looked good to plan to Brussels -div LGW . Approaching BRU and top of descent , fuel looked good to plan LGW -div Bournemouth . Landed above legal limits , had to be good weather , and no holding delays.
If we'd not been able to save enough fuel for the above , then it would be a Gas 'n Go for a top up somewhere along the route .
Approach swops ... holding at LHR , if really short get on company frequency , ask them to arrange an approach swop with another co. a/c with more fuel ...
Mind you early days of A320s at LHR , someone ups and says '' in 10 mins we need to divert '' ..... ''Where '' says ATC . ''27R from 27L'' say a/c
''.....'' ! says ATC ... 2 more a/c pipe up with same info .. A320 management had to back off fuel savings a bit .
Island Reserve was another tool in the fuel tool box . Something like LHR-Bermuda in the old days , nearest div. is New York JFK [ 700nm ]nto wind . 707s could not do that , so at the PNA [ point of no alternate ] decision was made to go on or div. If to go on , weather had to be good , airfield open , etc. and 2 hours holding fuel at BDA had to be onboard.
2 hours should have been enough to bulldoze any smoking wreck of the runway reserved for you .

rgds condor .

[blind pew]

Instances where engines flamed out whilst taxing in or using trim fuel as the rest had been used...covered up under the old boys act.
In the old days planned to an enroute airfield and then recleared to destination followed by committed to land.
Then we had island reserve..happy days

[Harry Wayfarers]

Instances where engines flamed out whilst taxing in or using trim fuel as the rest had been used...covered up under the old boys act.
In the old days planned to an enroute airfield and then recleared to destination followed by committed to land.
Then we had island reserve..happy days

And alsdo in the old days aircraft would be declaring fuel emergencies for priority landings ... So they changed the rules where such aircraft needed to declare a PAN or MAYDAY, of course then lots of paperwork etc. would be involved so the practice was curtailed.

[ETOPS]

Peter47

Is it possible for an airline to "swap" flights in the hold?

Yes - have actually done that a couple of times. Holding at LHR, awaiting my turn for a Cat III autoland, I had a call from ops asking if I was going to divert. Told them I had plenty of fuel so they asked the favour to allow a company flight above me to go first due getting close to minimum. After ATC had picked him out of the hold I had another call from ops.....:rolleyes:

That's how I learned to keep my trap shut.