747-400 Fuel Plan

[VFE]

Hi folks,

Could any kind soul here give me a rough idea of the fuel plan for a B747-400 flying from HKG to LDN please? Contingency, taxi, etc... and the likely differences for the return leg?

Also, I am looking for information on the fire extinguishing systems for the -400 please. If anyone can offer some salient points I would be very grateful.

Many thanks!

VFE.

PS: Have done a search but couldn't find what I was loooking for.

[Mercenary Pilot]

Lamidanda (LDN) Nepal?

Also, I am looking for information on the fire extinguishing systems for the -400 please

*There are two fire extinguisher bottles in each wing for the two engines on that wing, one or both bottles can be discharged in either engine on a wing.

*There is one APU fire extinguisher bottle controlled by the APU Fire switch.

*There are four fire extinguisher bottles for the forward and aft cargo
compartments. Pushing the Cargo Fire Discharge switch discharges two bottles immediately. The other two bottles discharge after a brief delay, or upon touchdown.

Are you looking anything more specific than that?

[VFE]

That is great thanks Mercenary Pilot! Just one other (possibly silly) question: Is it possible to crossfeed fire extinguisher contents from one wing to the other?

Thanks again,

VFE.

[Mercenary Pilot]

No it's not possible to crossfeed the extinguishers from one wing to the other. It's 2 bottles per wing but just pulling the handle out will close the related engine & spar fuel valves, the bleed valve, trip off the related engine generator, shut off hydraulic fluid and depressurise the engine-driven hydraulic pump so hopefully that would be all the fires 'fuel' and ignition sources removed. :ok:

For fuel burn, a rough estimate is 10 ton per hour with taxi burn of 1500kg per 10 mins. HKG-LDN (Nepal) is GC distance of 1750 so a 744 at LRC should do that in just over 3.5 hours, so add a little for airways and departure from HKG and I think the fuel required would be in the ballpark of 40,000KG plus normal reserves.

[VFE]

That is great thanks MP! Must confess I meant LHR not LDN, d'oh!

If you had to list them, what operational reasons make the 744 a better aircraft than a 777-300ER? Obviously the 744 can carry more pax but specifically, would there be any operational advantages from the RB211-524HT over the GE90-115 or anything else blindingly obvious which I cannot spot that would give the 744 the edge in a popularity contest?

Thanks again,

VFE.

[wiggy]

It's 2 bottles per wing

Well I never - The 744s I flew for the best part of two decades, all with the same company, very definitely had two bottles per engine - I didn't realise that a two bottles per wing option existed on the 744..... :hmm:

what operational reasons make the 744 a better aircraft than a 777-300ER?

Is it? The 400's great when you can fill it with passengers paying full fare, has a superb first class, bunks adjacent to the flight deck, and you don't have ETOPS criteria to contend with. OTOH the 777 is more modern, cheaper to run (alledgedly ) than a 744 and some argue often has a greater freight (weight) capacity......oh and it can autoland in 40 knots across :D, and it's newer, and it's got ADS/CPDLC by default, etc, etc.

Whatever your preference they're both top aircraft.

[VFE]

Just a thought here, but 1500KG for 10mins taxi seems a lot....

How long would one expect to be held/taxiing for at peak time in HKG as a matter of interest?

Thanks again,

VFE.

[wiggy]

1500KG for 10mins taxi seems a lot

Errr, you're right, it is a rather a lot, that equates to 9 tonnes an hour...:=

Seem to recall that the rule of thumb for the 744 was about 4 tonnes an hour (roughly) for taxi...any other takers?

FWIW 10-11 tonnes per hour over the whole flight is about right.

[Mercenary Pilot]

HKG-LHR, GC distance of 6000nm, flying East to West so I'll use a headwind of lets say 60kts average, take-off mass of 380,000Kg, using LRC with optimum step-climbs gives me a burn of 145,000kg and just under 14 hours flight time.

I'm sure someone who flies this route often will know much more accurate figures using their Econ speeds, known average winds and actual ground distance etc but I did my calculation straight from the 744 Perf manual so hopefully its in the park.

If you had to list them, what operational reasons make the 744 a better aircraft than a 777-300ER?

As a Pax aircraft its hard to list many reasons nowadays due to extended ETOPS routes allowed on the 777 and its ability to lift almost the same numbers but burn around 30% less fuel so I'm told. Also the old advantages of not having to turn back or divert after an engine failure are becoming mute as I understand many companies SOP's these days advise their jumbo crews to divert even though the 744 is more than able to safely continue on 3 engines with no loss of capability other than a reduction in cruise level and range.

From what I understand the purchase price of second hand 777 equipment is still high so some airlines are unable to replace them for the time being but as the fuel prices and competition increase the more the 777 becomes a necessity and the more the 744 will be converted to freighters, and there is actually a very strong demand for said 744 conversions at the moment as it is fantastic in this role.

[Mercenary Pilot]

I didn't realise that a two bottles per wing option existed on the 744.....

That's interesting as I never knew a 2 bottles per engine option existed ether. I'll try to copy and paste the schematic from my FCOM.

How long would one expect to be held/taxiing for at peak time in HKG as a matter of interest?

From the freight ramp, I'm usually airborne within 10-20 mins at HKG.

1500KG for 10mins taxi seems a lot


Quite correct, I should have said 20 mins. typo.

[eckhard]

Hi VFE,

Yesterday's HKG LHR flight (with RB211 engines) was into an abnormally weak headwind of only 4kts average, so these figures are unusual:

TOW 358000kg
Trip fuel 120000kg 12.00hrs 5550nm
Cont 800 kg 0.05min
Div 3800kg 0.20min 80nm
Res 4100kg 30min
Taxi 1200kg 25 min

TOTAL 129900kg

As far as fire extinguishers are concerned, the RR engines have 2 extinguishers per engine and the GE engines have 2 extinguishers per wing.

On the RR, you cannot cross-feed any engine's extinguisher into another one on the same wing, let alone across the wing. But as they have two each, I guess it was considered unneccessary.

On the GE engines either of the two bottles can be fired into either engine on the same wing, but you cannot cross-feed across to the other wing.

Don't know about PW engines.

Ball-park fuel flow for RR at heavy weight is 12000kg per hour initially, then after 12 hours it's down to about 8000kg. Taxi fuel is 2800kg per hour.

Hope this helps.

Eck

[Mercenary Pilot]

Don't know about PW engines.


They must be the same as the GE as I've flown both types and that is my understanding of the system from the FCOM's I have, I never knew that about the Rollers though, thanks for the info.

[VFE]

Thank you Eckhard, Mercenary Pilot and Wiggy!

Very helpful of you all - muchly appreciated.

VFE.

[SMOC]

The RR bottles are in the inlet nacelle of each engine, while with the P&W & GE engines the two much bigger bottles are in the wing LE inboard of pylons 2 & 3.

Edit: Apparently nacelle wasnt specific enough.

[Whinging Tinny]

Actually, the RR ones, are located in the nose inlet cowl, lower, L/H side.

[VFE]

Thanks guys, very useful. A couple more starters for ten...

1) What is the PSI of the (TE) flaps hydraulic system?

2) Are the LE flaps still pneumatic?

3) What is the air composition of the tyres?

4) Compared to the 777, does the 747 have greater redundancy in the flying controls following single and double hydraulic failure?

Many thanks again.

[Mercenary Pilot]

1) What is the PSI of the (TE) flaps hydraulic system?

The trailing edge flaps are powered by hydraulic systems 1 (Inboards) and 4 (Outboards) which are pressurised to appropriately 3000 psi

2) Are the LE flaps still pneumatic?

Yep by bleed air. LE and TE flaps can also be driven by electric motors if their respective hydraulic/pneumatic system fails.

3) What is the air composition of the tyres?

I think its nitrogen gas only (not a mixture with other gasses but im not 100% sure) to a pressure of 200 PSI

4) Compared to the 777, does the 747 have greater redundancy in the flying controls following single and double hydraulic failure?

I've never flown the 777 but 747 has 4 systems of which any one alone is still capable of offering power to an aileron, elevator and rudder to give the pilot some control in all 3 axis.

[VFE]

Thanks MP!

Can anyone clarify the hydraulics reduncancy available on the 777 please? And whether the tyres are filled with 100% nitrogen on the 744?

Thanks,

VFE.

[irishpilot1990]

somebody has an interview soon :cool:

[FRQ Charlie Bravo]

What is the order of fuel use on a long-haul flight and the theory behind the aerodynamics?

I know that using the fuel from the tail first or last is supposed to be of aerodynamic benefit but I cannot remember which way it goes and why. I have looked it up in the books I have here at home but I was hoping for a bit more of an explanation.

Thanks in advance,

FRQ CB