When to Divert for Low Fuel

[deckerloyd 0]

Good evening ladies and gentlemen,

 

So I'm in the middle of a calming 11 hour flight on BAW17 from EGLL to RKSI. I've run into some less-than-favorable winds that are pushing me pretty far into my reserve fuel. To make matters worse, I'm flying pretty far north where it's -70C at altitude and I've been flirting with my minimum fuel temperature, forcing me to speed up and stay lower than I'd like. 

 

Long story short, I'm cutting it very close to my alternate/reserve fuel of 17,000lbs (7700kgs). How low should I let it get before I divert? If I'm still an hour out and I hit 17,000lbs do I divert then or sooner or later? Is there a point when I pretty much have to discontinue the flight and land once my fuel gets low enough? I've torn through the manuals and couldn't find it anything.

 

Thanks for your help!

W. Decker Loyd

[downscc 1,327]

It won't be in the manuals.  In general (there are many company policies so I am staying in general), it is prudent to divert when your 30 min plus alternate reserve is on the line. Don't drink from that cup. If the weather at destination and alternate is good then you have a little wiggle room but your destination can close down and divert you for reasons other than weather such as an accident.

 

On a flight of that length, I like to have a redispatch point so my go/nogo decision past the redispatch point is based on numbers.

[deckerloyd 0]

Hmmm, that all makes sense. Thanks for the response. I guess I should start using redispatch procedures for those extra long hauls. What's the best software that has redispatch capabilities? Simbrief.com doesn't does it?

[MarkW 1,491]

PFPX. There is a very good video on this posted on their website.

[skelsey 765]

PFPX will do redispatch (BA don't do it in the real world as far as I know, though).

 

The key word is airmanship. The absolute minimum legal landing fuel (under any circumstances) is your 30 minute reserve -- if you expect to land with less than that you should be declaring a Mayday and you'd have questions to answer afterwards.

 

You may decide to "commit" to your destination and burn your alternate fuel in the hold (for example). However, as Dan says, you need to weigh up the options that are available to you: if the weather forecast is good and has more than one runway, for example, you might consider that the likelihood of needing to divert is low. However, this needs to be weighed against the risks: what if there's a security alert/natural disaster and the airport is completely closed? What if the aircraft ahead of you has a landing gear failure on touchdown and blocks the only runway? On the other hand, landing at your original destination is good news for you, your company and your customers in the back -- if you divert, will you have enough crew duty hours to continue to your destination once you've refuelled? What about passengers connecting on to other flights -- missing those connections could be expensive for the company. What about the return flight -- you could end up disrupting the whole airline's schedule with the knock-on effects. That's why captains get paid the big bucks -- to make these sort of command (and commercial) decisions.

[Boeing or not going 578]

Isn't there a -47c limit on the fuel?

[scandinavian13 5,192]

 

 

The absolute minimum legal landing fuel (under any circumstances) is your 30 minute reserve -- if you expect to land with less than that you should be declaring a Mayday and you'd have questions to answer afterwards.

 

Just to clarify, over in the United States (perhaps not relevant to this thread, but in general), if you're planning based on the FARs, you must plan to land with that fuel. If you're in flight an encounter a situation where you might land with 29 minutes instead, there's no reg against it. It's all up to the PIC at that point. I'm not saying it's smart, but it's not necessarily against the regs (FAA).

 

 

Isn't there a -47c limit on the fuel?

 

Depends on the fuel.

 

Sign your posts please.

[tcas_climb 45]

Just to add and reiterate what everyone else says, reserves (30/45 minute) plus alternate fuel should not be touched. If at any point with reasonable certainty that you will be eating into this fuel, then divert, maybe not immediately but to an airport closer to your destination where your company will allow you to refuel. Some airlines/regs will allow you to use the alternate fuel and just land with the 30/45 minute reserve alone so you get more wiggle room, of course there has to be "reasonable certainly" that you will be able to land at your destination. I've seen something similar happen multiple times, where the airport I work at closes it's single runway because of emergency repairs for so long that some pilots divert, while others chose to use their alternate fuel to hold while advising you that they are committed to land here.