747-8 Required Landing Fuel Weight

[sbclark]

I recently transitioned from the 747-400 to the 747-8. With the -400, as I always understood it, fuel planning required me to land with at least 30,000 lbs of fuel remaining to prevent the main fuel pumps from overheating?

Now that I am flying the -8, do I still need to land with 30,000 lbs of fuel?

Bill Clark

 

[downscc]

Nope, and in the -400 as little as 22000 lbs would be plenty to keep the oil heat exchanger covered.

[sloppysmusic]

3 hours ago, downscc said:

Nope, and in the -400 as little as 22000 lbs would be plenty to keep the oil heat exchanger covered.

So is there a minimum safe fuel level for the 8 at all? That 400 figure you gave will come in handy, do we need one for the 8 or can you fly on fumes if you don't mind glider landings?

😄

[downscc]

2 minutes ago, sloppysmusic said:

So is there a minimum safe fuel level for the 8 at all? That 400 figure you gave will come in handy, do we need one for the 8 or can you fly on fumes if you don't mind glider landings?

😄

I guess.... not sure how low you'd ever want to push it. You still need alternate and reserves.  In practical terms you will rarely get below 18-22,000 lbs.

I was with a pilot in a light twin that pushed it close to fumes and I never forgave him.  He had to install wing locker tanks after that... not a pleasant experience.  I don't even let my automobile get below a quarter tank.

[sloppysmusic]

3 minutes ago, downscc said:

I guess.... not sure how low you'd ever want to push it. You still need alternate and reserves.  In practical terms you will rarely get below 18-22,000 lbs.

I was with a pilot in a light twin that pushed it close to fumes and I never forgave him.  He had to install wing locker tanks after that... not a pleasant experience.  I don't even let my automobile get below a quarter tank.

I'm the world's worst for not leaving on a trip without topping up the tank first in a car or bike. When new to sims way back my ignorance for YEARS kept me flying always with full tanks, never realizing why my planes were so sluggish....that was 20 years back mind you.

I'm always interested in the tech stuff and what-if situations. If the 747-8 develops a bad fuel line leak (not actual tank leak) due to an unforeseen reason obviously you can isolate the tanks and lines so at worst only one engine should be affected. If you HAD to run an engine until the supplying source ran out would you shut it down before the coughing and spluttering started? I guess by now you'd be descending to your nearest alternate. Apart from the leaky fuel/fire risk, would you ever deliberately shut an engine down after declaring an emergency to stop it running dry and damage occurring in the fuel system? The quick question being, if you isolated an engine and ran it dry completely what if any damage would result?

Oh that scenario you mentioned...definitely not something you'd be laughing about in the bar after.....

[vc10man]

I usually use PFPX to give the Release Fuel, then as a precaution add a further 5-10 tonnes on top to cover. Landed at Bangkok tonight with 22k FOB

[sbclark]

Hi,

Thanks for your responses, but my question is not answered.

I need to know that once I'm on the ground, how many pounds I need to have remaining in the main tanks?

As I said in my original post, I thought 30,000 lbs was the correct amount for the -400...........so what number should be used for the -8?

I now cover the reserves, alternates, and anything else using PFPX, but once I land, there has to be a number, unless the fuel pumps have either been redesigned, or cooled, in a different way on the -8?

Bill Clark

[sloppysmusic]

46 minutes ago, sbclark said:

I need to know that once I'm on the ground, how many pounds I need to have remaining in the main tanks?

Are you talking about legally, or for aircraft care, or for company procedure? I would like to be proven wrong here but I cannot see any commercial or freight aircraft being 'damaged' in any meaningful way by being low on fuel. Otherwise the fuel remaining would be a useless figure, instead it would be 'usable fuel remaining'. Which is silly as you're literally carrying dead weight then. If at 20k lbs you were in trouble then 40 would be the new 20.

So you must mean legally (30 mins flying time?) or just company procedure. which would vary of course.

If it says any official Boeing manual you must land with at least X lbs or kgs fuel on board to avoid some kind of damage to systems I would be very interested to read it! I believe the planes are designed to fly to the last pound if they MUST do so and of course reserves and extras for taxiing and holds would depend on airports and configurations of the plane.

So when you say you want to know how much fuel you NEED to have remaining in the main tanks, to fulfill WHICH need are you referring? Legal, or service based? Legal limits definitely apply but probably differ around the world. Service limits would be more reliable when followed at gate arrival than touchdown.

Trying to help define your question exactly sorry i am not of any actual help!

 

[Jim Erwin]

I recalled reading something about the minimum landing fuel. It was the following in the original Tutorial #1 at p. 0.00.20 (31JAN17):

"The 747-400 cools its hydraulic pumps using fuel in the main wing tanks and you need to land with around 30,000 lbs (13608 kg) total fuel remaining to avoid overheating these pumps, which is the main reason you need so much extra fuel compared to other aircraft you may be used to. Use more fuel if you have a long-distance alternate or other extenuating circumstances." 

I couldn't find anything about it in the manuals. Perhaps the author of the tutorial can provide a source for the statement. 

 

Jim Erwin

[BlueStar]

1 hour ago, sbclark said:

I need to know that once I'm on the ground, how many pounds I need to have remaining in the main tanks?

Enough to taxi with always helps. There are no legal requirements for the amount of fuel that must be on board on landing that I know about, although it is possible that some companies may have that as a policy.  The aircraft's fuel requirement must meet FAA/Military (or the regulatory agency governing the flight) fuel reserve requirements before departure.  Some companies have an additional minimum fuel requirement for departure that varies by company and aircraft.   

Things to consider when carrying fuel in excess of required reserves is it takes about one pound of fuel to carry six pounds of fuel.  Every pound of fuel that is loaded in excess of that required costs money in the forms lost revenue in freight left at the dock and the cost of carry that extra fuel.  I personally have never been denied extra fuel when requested with no questions asked, but on the flip side had to explain why I landed with a low fuel warning light.  

Grace and Peace,   

[BlueStar]

2 hours ago, downscc said:

not sure how low you'd ever want to push it.

Dan,

When I was in SE Asia I landed several times where I was 10 minutes into my 20 minute Low Fuel Light.  Nothing to be proud of. 

Grace and Peace,

[nitsaw]

16 minutes ago, Jim Erwin said:

I recalled reading something about the minimum landing fuel. It was the following in the original Tutorial #1 at p. 0.00.20 (31JAN17):

"The 747-400 cools its hydraulic pumps using fuel in the main wing tanks and you need to land with around 30,000 lbs (13608 kg) total fuel remaining to avoid overheating these pumps, which is the main reason you need so much extra fuel compared to other aircraft you may be used to. Use more fuel if you have a long-distance alternate or other extenuating circumstances." 

I couldn't find anything about it in the manuals. Perhaps the author of the tutorial can provide a source for the statement. 

 

Jim Erwin

I’m curious about this as well! As I have never found anything in the FCOM about it. I would also like to know where they got the information from?

 

Best  regards,

Austin MacDaniels 

[downscc]

The -400, hydraulic fluid cooling (not pumps) and minimum fuel requirements issue was discussed in a number of threads in the period after the QOTSII release.  There is a fuel level below which there will be a gradual increase in hydraulic fluid temperature.  I don't recall the exact amount that RSR discussed when we covered this in beta but it is somewhere around 11000 kgs.  The interested could easily determine this by simply flying her low until the issue arose.  As I recall the heat exchange tube runs thorough mains 2 & 3 only.

This has nothing to do with the -8 fuel system.  The question of how little fuel one may have and still have engines running is a moot point, because you'd never want to be that low.  However, the interested could determine this as well.

[LRBS]

This is amazing how people will come up with numbers that cannot be found anywhere in the manual ex for this instance minimum quantity of fuel requirement for landing,  which is different from minimum fuel requirement for landing based on FAA ICAO etc for a flight.

There is absolutely no  restriction of the minimum quantity of fuel requirement (for the 400 or -8)  for purpose of keeping hydraulic fluid cold, yes it is true the temp will rise insignificant and will pose no thereat for the operation. There is no limitation on that.

There are recommendations for minimum fuel on board on a go-around and also for take off, now if some of you folks want to set a number, go right ahead by any means but that's not a FCOM limitation.

That 11000 KGS it's a bogus number, sometimes we land with 7000, 9000 based on alternate (if required) observing the FAA, ICAO etc laws.

[sloppysmusic]

47 minutes ago, downscc said:

The question of how little fuel one may have and still have engines running is a moot point, because you'd never want to be that low. 

Well thats certainly true but I don't think it's a moot point as the fcom is full of absolutes, in the form of numbers and logic of what happens in non normal situations so that the pilots can make decisions and be sure of results so non normal does not become an emergency. Obviously pilots would not want emergencies or the non normal to happen but they do anyway. A pilot must know at which point the fuel level the plane will fall out of the sky and at which time it will either explode or catch fire or if there is any risk of that at all. I believe it's only a service issue as I can't believe any commercial airliner would not be able to fly and land BEFORE running out of fuel rather that running low is not easy on the systems and will require service after. Much like servicing landing gear and wheels plus tires after a heavy landing, or a wheels up landing. Neither of those situations is wanted by anyone but they are described in the manual. I'm surprised low fuel situations are not described either as they can and certainly do happen in real life.