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Why does a plane have to 'dump' fuel before landing?

Discussion in 'AviatorChat.com' started by 96redLT4, Jan 17, 2020.

  1. norcal2

    norcal2 F1 Veteran
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    I still remember when I was stationed at Moffett field, and deployed overseas with my car in storage under a car cover in an outdoor storage lot, i would come back to fuel spots all over the car as there were a lot of times when we would dump, flying over the area, this was the late 70's though dont know if those rules were in place we dumped a lot of fuel...
     
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  2. tazandjan

    tazandjan Three Time F1 World Champ
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    I flew on a US Air flight from Albuquerque to Pittsburgh one time with the government footing the bill since I was active duty. They had the contract to fly DOD personnel to what was then Washington National. They called me up to the desk and upgraded me to first class because I was the only person on the aircraft with a frequent flier number. Do not see that much any more.
     
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  3. David_S

    David_S F1 Veteran
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    I can see how such operations might be strictly regulated/restricted, but surely the added fuel consumption would be a huge plus in this case?
     
  4. tazandjan

    tazandjan Three Time F1 World Champ
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    David- Depends on whether you are trying to burn down fuel to land or actually get somewhere.
     
  5. Nate2046

    Nate2046 Rookie

    Oct 15, 2006
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    That’s a fair question. First, consider there is absolutely no way you’re making the destination. The amount of drag is huge and your altitude is going to be down in the teens. Diverting to an airport along the route might make sense in certain cases, but you’re going to need an entire new flight plan to ensure you have all the fuel required to meet reserve and alternate airport rules. You’d also need to make sure you have permission to land at those airports. You don’t just drop in on say, Narita, with a 747-8 unannounced with a load of cargo cleared to a different country. Once the airplane is parked, it’ll need to be fixed, so maintenance capability is a major factor. How much time we burn up flying slow and low will also factor into whether the crew can continue the flight after repairs are made.
    So, there’s a lot of factors to take into consideration and sometimes the most cost effective and expeditious solution is going to be dump, return, fix, and relaunch.
     
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  6. Ak Jim

    Ak Jim F1 Rookie
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    Dec 23, 2007
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    There are several considerations for heavy weight landings. One is if you are single engine you always must have the ability to do a single engine go around, that could be a big factor in dumping fuel. Also for other emergencies there can be system degradation. As an example with certain hydraulic issues the anti skid brakes can become less effective. Also certain problems can require a back up system to lower or raise the flaps, this back up is usually electrical instead of hydraulic and can take a really long time to raise and lower the flaps. Not sure the details of this incident but there are definitely times to dump fuel (we use to say adjust gross weight so it didn't sound as bad!) and other times when an overweight landing is no big deal. Also on a somewhat unrelated side note. If you have two engines and you lose an engine 50% of your power is gone. On a four engine plane you only lose 25% of your power.
     
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  7. tantumaude

    tantumaude Formula Junior
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    It is actually correct. We can, and often do, determine that an aircraft is experiencing an emergency. I've done it myself twice, cleared the approach and called out the ARFF for a CRJ (once with inop flaps from an airline whose SOPs include 'take the time to evaluate whether a master warning light on takeoff truly warrants rejecting--it costs the company money'). The pilots were asked if they were declaring, said no, and we said too bad, we're declaring it for you.
     
  8. jcurry

    jcurry F1 World Champ
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    I believe that ATC has the authority to handle any situation as an emergency, regardless of whether the PIC specifically declares an emergency. The two are not mutually inclusive.

    Consider if I were flying on an IFR clearance, under Part 91. The controller could start issuing instructions as if there were an emergency. If I were in VMC and outside controlled airspace I could cancel the IFR and no longer be under ATC control, regardless of what they thought the emergency was.
     
  9. donv

    donv F1 World Champ
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    That really does depend on the aircraft. For example, the Learjet 35 has a maximum amount of fuel in the tip tanks (925 pounds/tip) for landing, which is quite an important limitation-- and is unrelated to max landing weight.
     
  10. tantumaude

    tantumaude Formula Junior
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    I see your point. Not entirely sure how it works in the USA. Here at YYZ we are class C airspace, anybody inside is under our control.
     

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