Quote:
Originally Posted by wdfifteen
Oh yeah. I flew Ohio to Denver last month and there was a strong headwind. They ask a passenger to get off (threw them off, actually) so they could put an extra 180 pounds of fuel on board. Told us it would take an extra 20 minutes flight time. I'm not real comfy with them cutting it that close. "Just fill it up - I'll loan you the $$ for the extra gas, just get me there."
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They aren't actually cutting it as close as you believe. There are FAA rules for minimum fuel that must be carried. The absolute minimum Reserve fuel that must be on any airline flight is 45 minutes worth of fuel projected to be on the jet at anticipated touchdown time, taking into account all variables that can affect the flight time for that given flight. No pilot or dispatcher I know will be comfortable with only 45 minutes worth of extra fuel however, so more is typically added as a buffer.
Now, throw in forecast and/or actual bad weather at the destination airport, and the flight will need to have a viable alternate airport added to the flight plan - and occasionally TWO alternates, if the first alternate planned is considered slightly marginal. Obviously that will require even more fuel - oftentimes a LOT more fuel.
Throw in some extra fuel for possible holding delays enroute, and the fuel load goes up even more.
Anyway, realize that there is no "cutting it close" on an airline flight with regard to fuel.
Now, on the other hand, if an airline were to "fill it up" on every flight, yes the flight would arrive with LOTS of excess fuel, however, quite possibly 1/3 of the passengers would have to be left behind due to weight constraints - usually maximum certificated landing weight. That certainly would NOT make those passengers happy.
As for shifting passengers, yes, believe it or not, a 50,000 pound jet's BALANCE can be thrown out of the acceptable range through the placement of just one or two 180 pound passengers. Will it crash? Almost certainly not. However, flight stability and pitch authority margins will be compromised - even if only a little. Every aircraft has a Center of Gravity range that allows acceptable flight characteristics. It's called a CG envelope. If the CG is out of the envelope, no matter how close it may be, it's out of the envelope and must be corrected. Oftentimes, that will only require one or two passengers to be shifted for or aft.
Large jetliners have these very same issues, however - due to the fact that the larger jets all store their cargo under the passenger cabin in long compartments - cargo will get shifted fore or aft by ramp personnel if a weight and balance issue arises. This is transparent to the passengers, of course. A smaller Regional Jet usually has most of its cargo loaded in a cargo hold that is not under but AFT of the passenger cabin, where it has a great effect on CG. Since there is nowhere else to shift cargo to, the only other way to shift CG is by moving one or two passengers.