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Bit confused - holding - when to divert to alternate??

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Hello thereThis may seem dull in comparison with the announced A320!!!!! Yippee!!!!!!!!!!!!!!!!On my flight from Singapore to London tomorrow, I am going to carry this in reserve fuel in accordance with company policy:- 4000kg route reserve fuel- 4200kg/ 30minutes holding fuel- 2000kg approach fuel- 5900kg fuel to alternate- 2200kg additional fuel - roughly 20 minutes extra holding.Total reserves: 18300kgMy question is this:If I fly into heathrow having spent none of my reserve fuel (ie all 18300kg of reserves still there), and am asked to hold for say, 30 minutes, am I legally bound to divert to my alternate airport if my fuel approaches a point at which I wouldn't be able to divert anymore?When do I have to divert?It will take 5900kg to get to the alternate, and I will need 5500kg (minimum landing fuel) plus my approach fuel (2000kg) at the alternate. This would mean that I will have only 4900kg (18300- {5500+2000+5900}) of fuel for holding at my destination.Am I right, or am I wrong?? I am very confused.Hopeign someone can help me!


Rudy Fidao

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Hi there,You do not say where your alternate is and if you actually need one or not. At the flight planning stage you would most likely plan for one, however this is dependant upon an individual airlines fuel policy. Technically all you have to do is land somewhere and then the engines stop with fuel exhaustion but of course this would be foolish.With what you have stated you will arrive overhead with 18300 kg and that this includes 4000kg of route reserve fuel (is this contingency fuel?). 4000kg is approx 30 min holding for a start and you wont even have started to burn into your diversion gas. If you wanted to hold for longer then you could consider the following:1. Hold at an optimum altitude.2. Look at closer alternate airport options. Stanstead, Gatwick3. Does the weather at destination need an alternate. If the weather is fine then why do you need to preserve alternate fuel? Normally you would plan to land at your alternate with 30 min holding fuel, which in your case, is 4200 kg. In other words you have 18300 - 4200 = 14100 kg to get to your alternate and you B to C burn is only 5900kg. That gives you 8200 kg to play with...stacks.The reserve figure you should enter in the PERF page should be around 11400kg being the sum of 4200 kg hold fuel (30 min) + 5900 kg (B to C) and around 1300kg (Approach at C). When you go into a hold then you should have an indication of holding time avail on the hold page of the FMC until you get down to your entered reserve figure. CheersSteve


Cheers

Steve Hall

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That definitely clears things up. Thanks for the fantastic explanation.So, I understand that if (in some very odd turn of events), weathers was only fine at my destination, and farthest alternate, it is okay to use my diversion fuel if I am asked by heathrow to hold for 40 minutes or something, providing weather will be fine and holding time is not going to completely eat up all reserves?Yes, the 4000kg route reserve is contingency. I suppose I was talking about the worst case - if no other alternates bar my farthest one (EGCC Manchester) were available.Thanks again for your helpful reply.CheersRudy


Rudy Fidao

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In the US, the FAA has a procedure for pilots in these situations, where perhaps the hold is due to traffic instead of weather. The pilot may declare "minimum fuel," which is not a declaration of an emergency but it tells ATC that you need handling pretty soon. Of course, this is a judgement call but it is another alternative to consider in the situation.


Dan Downs KCRP

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Whatever you do don't keep circling because you are too worried about loss of face if you declare a fuel emergency.At least one plane crash has been due to fuel running out whilst circling.Generally alternate fuel is for when you can't land due to weather accidents or French air traffic controller strikes etc. and need to go far far away. Most alternates are quite a way away so that a big storm etc. that shuts down your main will not be shutting down the alternate as well due to it being so close. (And if it is then you should have enough fuel to go somewhere where the storm isn't.)Most pilots would add in some extra to the contigency fuel for circling busy airports in addition to the alternate fuel. Rush hour is no different in the air except you can't hear the horns pipping.That way you can circle for a while until it is clear you can't land there and need to divert.Alternatively do what Ryanair do and land at the nearby military airbase :)

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Thanks Guys, everything is perfectly clear now. I'll stock up a bit of additional holding fuel for heathrow, although I don't think there'll be heaps of delays at 0530.I remember watching on televsion a show about that Avianca 707 that ran out of fuel - extremely sad situation, caused by confusion between the traffic control and the cockpit, and the differences between spanish and english and the word "emergency" and "priority".Anyway, again, thanks for all the fantastic replies!CheersRudy


Rudy Fidao

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"So, I understand that if (in some very odd turn of events), weathers was only fine at my destination, and farthest alternate, it is okay to use my diversion fuel if I am asked by heathrow to hold for 40 minutes or something, providing weather will be fine and holding time is not going to completely eat up all reserves?"yes this is a fair assumption. Just be aware that if your destination only has one runway what would you do if the preceding aircraft crashed on it just in front of you???? By the way normal contingency enroute is around 2% of A to B fuel (This varies from operator to operator and state to state. You will have stacks of gas with what you are planning (No airline would employ you!!!:) ) There are also plenty of enroute airfields to divert to if you run short for some unexplained reason.CheersSteve


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Steve Hall

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Guest benhoffman

Here's a short list of when one airline does not allow landing:- Crosswind greater than max allowable- Tailwindg reater than max allowable - RVR 2400 or less than 3/4sm visibility and precision instrument (all weather) runway markings, runway centreline lights along with airborne and ground equipment are not operational.- Snow, slush or water on landing runway of 1in or more and braking action is less than

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