It’d be better to do this with a B-52. Fly it over Phoenix and, well, they like golf there don’t they?
That’s not an answer that will get you hired. An interviewer that’s asking that question is looking for somebody who can figure out ways to develop something new. If you tell them that your solution is to wait until somebody else figures out the answer first and then look up the answer he got, the interviewer will decide he’d rather hire that other guy instead of you.
Oh yeah. There’s a whole industry that exists to disassemble dead jets and recover & resell any part large or small that has economic life left in it. When it’s down to just a roughly jet-shaped primitive sculpture of riveted aluminum, then the wrecking crew comes in and chews the hulk into truckable-sized pieces. Which trucks deliver to the same recycling places that take crushed beer cans.
The challenge for parting out an old 747-400 like that is everybody is parking them. The supply of recovered and recoverable parts is growing rapidly while the market for those parts is collapsing. Correctly deciding which parts to spend labor $ recovering and refurbishing is the secret sauce for the disassemblers. The guys who get it right make a pretty hefty margin. The guys who don’t go broke.
The OP specified “full of golfballs”, which implies no room to roll.
But since they are way too heavy even to taxi, the plane ain’t gonna do no rotating.
Thanks everyone. I have now formulated the correct smartarse answer.
Since a golf ball weights 45g, and a consignment of golfballs is a lot denser than airfreight volumetric weight (167kg/m3), you can fit (cargo payload x 20) golfballs in a plane. Eg 747 freighter: 113 tons -> 2 1/4 million.
Slightly tangential question: do large aircraft have to be weighed, or do they typically weigh themselves? It would be pretty straightforward to integrate load cells into the landing gear so that you always know the plane’s weight (on the ground), but does it actually work this way, or are external scales more frequently used?
Short version:
Load cells in the gear are a coming thing, but not in use yet that I’m aware of.
The weigh (heh!) it’s done now is more primitive. All the constituent parts are weighed individually and the total added up.
Long version:
The empty aircraft as a whole is weighed by the maintenance folks after each heavy maintenance event, roughly every 4-5 years. They use 3 really big jacks that incorporate load cells.
Thereafter any modification to the aircraft is recorded and the net weight of stuff added & removed is tracked. So there’s always a number available for the aircraft itself. This includes all the bolted-in equipment such as seats & bins, and the various oil & hydraulic fluids, plus the fuel sitting in lines & sumps.
A standard weight is worked up for each aircraft configuration for galley equipment, consumable supplies, crew, and crew baggage and equipment.
These two together form the “Operating Empty Weight”; the weight of the aircraft ready to be loaded with useful stuff. So this number is individual for each aircraft and is only updated every few years or when a modification is made to the aircraft.
Payload consists of cargo, hold baggage, passengers, and carry-ons. Payload is different on every flight and is weighed / computed before every flight.
Cargo and hold baggage are each weighed on a scale backstage and the total added to the OEW. The weight of any cargo containers is also added in. The hold(s) are logically divided into several sections fore/aft and they track what weight goes into which section. This distribution is monitored to ensure the overall fore/aft balance is both known and within tolerance.
Passengers with their carry-ons are divided into two groups: adults and children. There’s a standard weight assigned to each category. Which also varies between summer season and winter season. The passenger compartment is also logically divided into several sections fore/aft (unrelated to the various classes of service, size of seats, etc.) and how many folks are assigned seats in which section is also tracked to manage the fore/aft balance. Passengers are by far the least dense thing we carry, and they’re skittish about getting on a scale in public, so the FAA agrees with the marketing department that just assuming, say, 200# each is close enough.
Operating Empty Weight plus Payload gets us to “Zero Fuel Weight”. e.g. What the airplane weighs before any fuel is added. Knowing this number is also operationally handy because it’s a number that won’t change inflight. Since the fuel gauges read in lbs (or kilos) we can always add the current fuel gauge reading to the ZFW and know our weight now.
Fuel is ordered, metered, & gauged onboard in pounds or kilos, not gallons or liters. The flight planning process computes how much fuel is needed to haul the planned ZFW over the planned route against the planned winds. That gives the desired fuel load in lbs. That gets communicated to the fueling crew who pumps in fuel until the gauges read the right weight. They also do an error check that difference between on-board fuel weights before and after fueling match the gallonage pumped times today’s average fuel density.
Sources of error in the overall calc are predominantly in the average weight assumed for passengers and their carry-ons, and in inaccuracies in the fuel quantity gauging system.
well, you certainly can’t putter around with it, you must drive the entire range to get the right answer there, chip.
How does filling the body with golf balls cause the wings to pop off?
It wouldn’t be likely with a 747 because they have landing gear under the body as well as the wings, but other aircraft have gear on the wings only so overloading the plane will cause the body to overstress and snap the wing roots.
Main landing gear is attached to each wing, a short way out from the fuselage. So massively overloading the fuselage produces bending stress at the wing root.
Empirically that’s a lot of ways to screw up. Being able to just check the actual, in realtime weight distribution as it is right then sounds a lot better than trying to add 50 things together and hoping you didn’t make a systemic error somewhere. I’d feel a ton better as a pilot if I know, from an instrument system that checks 3+ redundant load cell sensors on each landing gear, that the aircraft is balanced and under the weight limit.
Sure there are a lot of moving parts to the current weight system. But the calcs are all automated and there are lots of external checks and balances along the way.
Actually, the one we worry about most is the fuel gauges being wrong. Not only for weight concerns, but what if slowly over time they’ve drifted and when we think we’ve got 1 hour of fuel left we’ve actually only got 5 minutes. We never burn into that last lump of fuel in the bottom, so we don’t have a routine empirical check that it’s really there. :eek:
One challenge with load cells is the Fed’s attitude to exceedances. We’d be trying to read to the single pound of accuracy for numbers anywhere from 100,000 to 1,000,000 lbs. That’s a lot of significant figures in the required precision.
And these load cells would take a hefty whacking on every landing. But would still expected to remain in calibration despite the beating. And being cooled to -40C for hours at a time then expected to perform accurately.
Supposedly the manufacturers are working on this. But even if we had it, it’d be a decade or more before we could eliminate the rest of the rigamarole as a cross-check. Which rigamarole is really just weighing a bunch of stuff and filling in the equivalent of a spreadsheet with about 6 inputs and a couple outputs.
There are several things that are IMO partly broken in aviation. This is far from the closest snake.
Please elaborate, … New thread if you deem necessary.
Could be very interesting to me & many others. 
Many years ago I was flying out of Detroit to Frankfurt. The plane has been fueled, passengers boarded, luggage stowed and THEN someone decides the plane is too heavy to take off. An extra couple hours on the tarmac while crews unloaded fuel to lighten our load. THEN a change of flight plan to fly to Ireland first for more fuel so that we could get to Frankfurt. All told it was about 15 hours sitting in coach for an 8.5 hour flight.
How did we get to the point of almost backing away from the gate before someone noticed we were too heavy?
Yeah. If the plane could measure it via some kind of reliable load cell (I have a vague idea for sensors that would be capable of a massive magnitude range, high precision, and be able to handle the low temperatures), there could be this little picture of the plane right there in the cockpit. Color coding would indicate the total load and the relative distribution.
There are a few ways that happens.
The schedule is created, and decisions are made about how big an airplane to use based on the expected typical ability to sell tickets, expected typical cargo volume, expected typical winds and weather (for fuel load), etc. These decisions are made months in advance. On the day of a flight you may have unusually heavy cargo volume, extra passengers (perhaps an earlier flight cancelled?), or the winds and weather require an extra large fuel load.
Very long haul flights are especially brittle on fuel loading for adverse weather. A small change in weather forecast can have a huge impact on fuel requirements. And if we need to add, say, 10,000 extra lbs of fuel, that’s the equivalent of leaving 50 passengers behind, or leaving the checked luggage for about 100 passengers behind.
At any rate, during the couple hours before departure everybody involved in planning realizes this one is going to be close; we’ll have to actively manage every pound. We get close to departure time and wouldn’t you know it, damn near every passenger is showing up with extra checked luggage; sometimes that happens. Or the agents have let too much carry-on baggage slide past them onto the jet and now we’re out of cabin overhead space and 50 bags are piling up in the jetway 10 minutes before departure. Bags which now count as cargo weight which used to count as passenger weight. Or 30 minutes ago somebody made a decision to ship a high priority part to Frankfurt to repair a jet that just broke down in Germany and suddenly we’ve got to accommodate 1000 lbs of crated jet parts. Or maybe a new weather forecast came out and now not only is Frankfurt forecasting fog for 9 hours later when we’re supposed to get there as we’d planned for, but so is the whole of Germany and now we need alternate fuel to return to distant Paris instead of just to nearby Heidelberg. Or maybe that extra cargo was known about hours ago but somebody forgot about the sticky note telling them to enter it into the computer and everybody was surprised when it showed up plane-side. Stuff happens, just like where you work.
Oops. Time to fall back and regroup. Ideally these changes all happen an hour-plus before departure when we have time to react. In that case you’re still going to stop in Ireland for gas, but at least you’ll depart Detroit close to on time. If the problem develops in the last hour, delays are inevitable.
Once we’re overweight, either planned on paper or actually on the aircraft, we have a process to solve it. First you see if you can shrink the fuel load safely. Maybe leave a little less generous extra pad for holding or worse-than-advertised winds. Then you leave behind any company employees traveling in otherwise empty seats and their carry-ons, but not any baggage they were foolish enough to check. (It’s too hard to dig it out of fully loaded cargo holds at the last minute). Then you leave low priority cargo behind. Then premium next-flight-out cargo. But not mail. The USPS will punish you grievously for leaving their stuff behind. Then you ask for volunteers to be left behind, like in an oversale situation. Maybe all these steps will get the books to balance.
If all this still won’t square the circle (or you realize in advance that all those steps won’t be big enough to solve a really huge weight problem) you fall back and punt: Plan to stop short for fuel along the way and put all the stuff we just mentioned back into the plan. Obviously it’s much better to do all this on paper or in the computer BEFORE any of it actually gets stowed aboard and has to be physically removed.
Oh yeah, and if we do have to defuel, that fuel is now unusable for aircraft. We can burn it in our various tugs, but we just paid aircraft fuel prices for thousands of gallons of truck diesel. Ouch.
But that’s a minor ouch compared to the money we’re about to lose operating a flight with a fuel stop. We just swung from a WAG $10K profit to a $40K loss for this flight. And by being 4 hours late to Frankfurt we probably force the return flight to be 3 hours late which will force the flight after that to be 2 hours late and the side effects of this single situation will reverberate through our system for the next 3 days.
You can see how deciding what to do and then implementing the plan can take awhile. The pilots and the guys on the ramp loading the jet are dedicated to this departure. The folks at HQ making flight planning and load planning decisions are working another 15 flights at the same time and their phones are going crazy and … When everything is going smoothly they’re staffed adequately to do everything timely. They can handle a couple oddball things going on at once, but if it’s a bad day at work, things can get badly bogged down at HQ where they’re just task saturated and we workers in the field end up waiting for them.
Even down to once the decision is made to stop in Ireland we need to file new flight plans, get all new paperwork, and reprogram the jet for the new plan. On newer machines most of that can be data-linked into the jet and it only takes about 10 minutes to manually cross-check the whole thing. On older airplanes it might take us 20 minutes to keystroke the whole mess into the nav system, followed by the same 10 minutes checking and probably correcting at least one typo. Odds are the pilots won’t be the long(est) pole in the delay tent, but we can be.
Bottom line: A really awesome amount of coordinated effort happens on each and every flight. When it goes smoothly it’s a sight to behold. I marvel at the ballet every time I watch 40 jets leave a big hub in 30 minutes. When even a small piece of it gets snarled, we all get to see graphically just how much stuff has to go right, and go right at the right time, before even a single aircraft moves an inch.
Load cells would provide a useful last-minute check. They would not necessarily detect in advance that the current trajectory of fuel, cargo, and passengers onboard would lead to an exceedance by departure time. As pointed out above, the key to success is early detection through complete and accurate planning.
I hate being so clearly wrong but you’re completely correct. Load cells don’t substitute for good planning. Now, what does bother me about this “add it up” scheme is that systemic error somewhere could throw you way off. A faulty scale used to weigh the bags, a mistake made when you measured the fuel, etc. Load cells are integrating it all - including cases where when you weight something your measurement was too heavy - and giving you the true system status. Similarly, instead of movement arm calculations, you have the true weight distribution including all movement arm effects in the real world.
And as I said, there are efforts to invent exactly this device for exactly the reasons you state. It would be nice to have. Maybe.
You’re in software development as near as I can tell. There’s a rule in database normalization that says in effect: “Only record any given fact exactly once.” Why? Conserving storage space isn’t a compelling reason nowadays. The reason for the rule is that if you record a single fact twice and later discover the two versions are different, now what?
The moment you create a system with multiple versions of reality you create the need for audits to detect differences, and reconciliation processes to resolve differences once detected.
Given my outline above of industry generic loading procedures, what ought we do when the computed numbers and the load cell readings don’t match up immediately before pushback? How often will this happen and will the ensuing disruption actually increase safety or just increase costs, delays, and frustrations?
If indeed we could simply stop doing all the planning and weighing and bookkeeping and just leave it all up to a go/no-go measurement immediately before departure there’d be some actual savings in effort, cost, and complexity to offset the effort, cost, and complexity of developing the new devices, fielding them, developing the procedures to use them, retraining all the relevant folks, and modifying all the relevant software. But I don’t see how we can get away from doing that work.
So far this doesn’t sound like an innovation that my shareholders would see as an obviously good invention. Nor do we have much empirical evidence that unrecognized overweight conditions are leading to safety hazards or undesired aircraft wear in service. This industry is very analytical. Everything is pretty heavily instrumented. By and large, innovation is directed at the largest problems, be they safety problems or cost problems. The mere fact we can conceive of an innovation doesn’t mean it’s necessarily going to be pursued.
In software we’re all familiar with the problem of premature optimization, or even folks who stubbornly want to optimize things that are completely irrelevant, such as compute speed on an I/O bound algorithm on a standalone processor. That’s not smart; that’s dumb. Wisdom lies in correctly locating true bottlenecks and actual weak areas and shoring them up in a cost- and effort-effective, industrially robust manner.
I’d just like to note that I originally read the title of this thread as “747 full of GOOFballs” and thought…the FAA might not condemn it but the DEA probably would.