Sitting on a Southwest 737 MAX8 that has been loaded and waiting for about 30 minutes without closing the doors. BWI-BOS. They apparently had to switch to this plane from another that had technical issues.
Pilot just said he’s waiting for a fueler to come over because they need 400 pounds of fuel.
What percentage of the fuel needed for this flight is this? It seems like a small amount of fuel to add before taking off.
Fuel loads are based on wind/weather conditions plus an alternate destination if the weather does not allow for landing. If the Center handling the corridor is experiencing diversions for any reason that is also taken into consideration.
Just Googled to find that this plane has a burn rate at cruise of 4,400 lb/hr. This is a one-hour flight, but mostly climb and descent.
We’re now 70 minutes late, and just closed the doors.
See you later.
400 lbs of fuel divided by 6.75 lbs per gallon times a fuel burn of 850 gallons per hour is about 4 minutes of fuel.
The fuel planning might be based on the next series of flights before another fueling opportunity comes up (costs, scheduling, contracts, etc). A delay in this city is, perhaps, less problematic downstream than a delay in another one.
I’ve only been to BOS once in a commercial plane and it was a beehive of activity. That was not during a holiday. The person on the ground frequency sounded like an auctioneer.
The usual issue here is that if the flight was planned for X fuel, then X is what’s required, period. And X-400 is illegal. Even though as noted, 400# of fuel is about 4 minutes of cruise burn in a 737 NG, and more like 5 or 6 minutes cruise burn in a MAX. This slightly-short-of-fuel situation happens a lot when there’s a plane change. Of course, the earlier the plane change is known, the better the odds HQ can get the revised fuel load or a top-off request to the fuelling contractor in time for them to get their task done to the correct jet before it becomes the pacing item for departure.
In general, if faced with a mere 400# shortfall on a 737-ish airplane the Captain and dispatcher will confer by phone and see if there is any slack or “just in case” fuel anywhere in the plan that can be revised out of existence. Thereby converting X-400 into a legal load. Sometimes that slack is built-in and can be prudently sacrificed in the name of a (more) on-time departure. If that is the case, the Dispatcher can datalink amended paperwork to the plane and pilots and after suitable review the Captain formally legally approves the revised plan which makes X-400 legal, the gate agent closes the door, and they push off the gate.
Sometimes there really isn’t any slack. Further, there are times when a prudent Captain would prefer another couple thousand pounds for “just in case”, but the weights, airport(s), diversion option(s), and weather don’t permit that luxury. Now’s where you earn your money. Do I push the issue and leave people behind, and incur delays for de-boarding, removing luggage or cargo, and for loading the additional top-off fuel, or do I go as planned, recognizing that although we’re 100% legal, our margins for bad luck are small and we’ll have to be extra pro-active about literally everything until we’re at the gate at the destination. And whatever our raw odds of a diversion were today, the extra-tight fuel bumps those odds by 5x. Or 20x. But we’re in the business of a) abiding 100% by the regs 100% of the time, and b) insofar as possible, moving as close to everything as close to every flight as close to on-time as possible.
With the occasional miscue that a diversion represents. Which is not to say that a diversion is proof-positive of a mistake or of corner-cutting gone bad. Sometimes weather or [whatever] just scrambles everything beyond recovery given the statistically sensible fuel planning and then executing the contingency plan of diverting is simply the smart, prudent, and, from our POV, very routine move.
The converse situation is switching to a plane that was fueled for a different mission and has too much fuel for your plan. If the flight isn’t already skoshy (technical term) on weight, we just go with the excess & waste some of it burning extra to carry the useless excess weight to the next station.
But if we’re right up against one of the weight limits for takeoff, cruise performance, landing, or diversion, then we’re faced with either offloading fuel or leaving people or luggage or cargo behind. Often time becomes the decider: which of those 4 offloads (or not-yet-loadeds) can we accomplish quickest with the fewest opportunities for miscommunication amongst all the moving parts? OK, let’s do that one.
Years ago I got held up on a connection out of Ottawa to Montreal due to a winter storm and cascading mispositioned crew and planes.
It became apparent that instead of flying a Q400 every 2ish hours or whatever that they were consolidating all passengers to Montreal onto a single flight. The plane we used was parked at the gate the whole time.
We eventually all boarded, and the plane was full. Many of us were arriving from Europe, so lots of luggage to account for.
Thing is, we weren’t moving. Lots of paperwork and discussion at the front, staff coming and going. Eventually, a fuel truck showed up and connected to the plane.
I could be misremembering, and I don’t know if this is what I assumed or overheard, but I’m pretty sure they were defueling. I don’t think this plane could take off at full pax, lots of cargo, and (presumably) full fuel.
This was over a decade ago, so my memory is very fuzzy other than remembering that it was a Very Long Day. We got home 7 hours later than planned; Ottawa airport to our home would have been a 2 hour drive!
I was once on a flight like that. We swapped planes due to some technical issue, and before we took off we had to taxi over to some remote corner of the airport, set the parking brake, and run the engines for a while to burn off some extra fuel. I assume because this was because this was such a short flight (MSP-LSE, typically ~30 minutes in the air) if we’d left with that extra fuel we would have been overweight when we landed.
Once fuel is in a plane the chain of custody is broken and they aren’t too keen on downloading fuel because of possible contamination.
Fuel that is pumped out of a plane cannot be reused as airplane fuel. It’s now overpriced diesel and is used to fuel baggage tugs, pushback tractors, etc.
In the course of a day at a commercial airport, the total amount of defueling is a rounding error on the total amount of ground equipment fuel consumption. It’s real easy to find a use for any fuel removed from a plane.
Thanks for the clarification. That’s some expensive tug fuel.
At the airline-sized airports around here, Jet-A from the bizjet FBOs is between $5.50 and $8.50/gal today. An airline, even one with only a couple flights pert day there, would get a pretty good price break due to the volume contracts.
Meanwhile, diesel fuel at ordinary gas stations around here seems to run $3.50 to $4.50 per gallon today. And good bet the GSE folks also get a discount versus retail on their bulk fuel purchases too.
So yeah, contaminated Jet-A used as diesel costs between 50% to 100% more than plain old diesel. Or $2 to $5/gallon extra. But at the volumes we’re talking about, it’s still a rounding error in the daily fuel budget.
IIRC my record worst defueling was ~15,000# from a 767-300. So ~2000 gallons so ~$5000 of incremental cost to burn in the GSE.
Surprise Breathalizers snag three FAs in Amsterdam; one at a low .024 (but the rules/laws in that country are the rules/laws) but the other were high enough to get a DUI if they were driving in the US.
ATA103, Standard for Jet Fuel Quality Control at Airports (essentially the Bible for air carrier fueling operations), allows re-use of fuel that’s been pulled from another aircraft. It’s mostly a paperwork issue, provided it isn’t being moved from one “owner” to another. Most airport fuel systems are either run directly by the respective airlines or are a consortium of airlines that contract out to the individual fueling companies. Smaller airports without an FBO tend to be self fueling, but those are not usually the air carrier airports where ATA103 is a thing (though some are). The “owner” of the fuel is usually a wash.
Almost every aircraft fuel servicing tank vehicle can defuel an aircraft through a single-point nozzle (the kind that is used for Jet A, AvGas doesn’t get defueled that way) right back into the truck. There isn’t a separate tank truck for defueling - it’s going directly into the next guy’s plane. Every time jet fuel is moved it’s filtered - there’s a filter before it goes into the tank at the airport, before it goes into a tank truck, before it goes into a hydrant system, and before it gets pumped into a plane (either from the tank truck or on a hydrant truck/cart).
Jet fuel is too expensive to let it go to waste. The fueling companies even re-use sumped fuel after letting it settle to make sure the water and sediment is removed from it (and it gets filtered before it goes into storage).
Another windy day in Wellington for anyone interested in following along:
Forecast is for northerly winds at 30 knots gusting to 50 knots.
Final report on a 737 incident at Bristol where the aircraft took off with 10 feet of altitude at the end of the runway.
The autothrottle disconnected when the TOGA button was pressed, due to an under-voltage condition. The crew had incorrectly set the takeoff thrust to 84%, and did not notice the autothrottle failure alert, until reaching 400 feet altitude, when they advanced the throttles to full.
The crew also missed the two callouts for thrust set and thrust at 80 knots, and did not sense the low throttle settings or autothrottle failure by required hands on the throttle.
That took a lot of willful aligning of the proverbial holes in the proverbial swiss cheese to accomplish.
And goodness gracious are the comments to that article moronic. Sounds closer to YouTube than to the SDMB.
That’s a scary read. If the plane is low why wouldn’t the PIC advance the throttles?