Please load as many carryons as possible
 

Sounds it may have been a Payload Optimized flight, perhaps.

This 95% of time means they have bunch of cargo and don't have weight or space available for carryons to go below.

It’s still an odd and seemingly unnecessary request from a gate agent.

Perhaps it could have been worded better. But it does sound like it was a payload optimized flight. More than likely, a passenger checking a bag at that point would have resulted in either that bag or someone else's bag not making the flight.

I'll admit I'm confused why these MD-90s end up payload optimized so frequently. Seems that most threads on this topic that pop up have MD-90s as the aircraft in question. PHL-ATL is a short flight for an MD-90 and MTOW/MLW are not that far apart (7 tons) so there should usually be plenty of excess cargo capacity on a normal short flight even if overfueled due to WX causing distant alternates or other issues. And Delta runs enough flights between PHL-ATL that I'd be surprised if they picked an MD-90 to haul some heavy cargo.*

Does anyone know if something get MEL'd on MD-90s frequently that results in significantly reduced range/payload capacity?

*edit: I see now that ATL-PHL seems to be an MD-90 only route. So disregard that last point..

It's actually not, and its because of how the FAA allows carriers to use "standard weights" for weight & balance purposes. Standard weights include you AND your carry-on items too. In the summer, you and your carry on bags weigh 190lbs according to the government. If the overhead bins are full, any bag that has to be gate-checked and put into the belly of the airplane, now has to be "accounted for" to the tune of 30 lbs per bag. I know, it seems asinine, because your 22" rollerboard is still on the airplane whether its in the bin above your head, or in the cargo hold, but the minute the bag goes into the cargo hold, it now counts as more weight.

The agents know the flight is payload optimized, so they are trying to prevent having to gate-check bags which just eats into the available payload margin. Or, think of it like this: every 6 gate checked bags equates to about 1 SDSB passenger who is trying to get on the flight!

Strange is in but true it also is. I flew the CRJs for years and we would often bring carryons that had been planned to be put in the cargo hold back up into the airplane where they magically no longer counted in Weight and Balance. Carryons in the cabin are included in passenger weights. Carryons loaded in the cargo hold weigh 30 lbs each. That's the magic of the FAA for you.

I realize that there are obviously tolerances with regards to W&B, but this seems like playing with fire a bit, no? If there's a reason that there are limits in the cargo hold, ostensibly for ensuring safe operation of flight, it seems like a bit of a logical fallacy that suddenly it's safe to operate and within acceptable limits because the same bags, with the same weight, are in the cabin.

I realize that this is all ostensibly taken into account as part of overall dispatch, but man, this one just seems strange.

One can argue with precisely how scientific it is, but there is a thread of logic here. The plane cabin has known storage space (underneath seats, overhead bins), and theoretically the standard passenger weights assume that those areas are fully loaded with passenger luggage (at least assuming it is a full flight).

If anything, since (I believe) standard passengers weights are the same for both mainline and regional jets, regional jets will chronically overestimate passenger weights because most of the luggage cannot fit into the overhead bins. On the flip side, planes with the new "pivot bins" that can carry more luggage are potentially underestimating a full plane load (at least relatively in comparison).

That said, given the tolerances in question, I'd rather underestimate on a regional jet and overestimate on a 737/A320 than the other way around.

For what it's worth, standard weights have slowly crept up over the years due to our expanding waistlines as well as increased use of carry-on luggage. It's possible we're due for another increase.

The FAA does occasionally adjust the average weights (esp to accommodate our fattening population). It used to be 180lbs for avg pax weight just a few years ago. Additionally, if you are an airline that doesn't allow carryons, the FAA has slightly different averages.

As a former agent, usually the first thing that's done in a "weight restriction" is to count the children. Children only count as 82lb. Back in my day (and perhaps still the same), airlines didn't discriminate between kids and adults in the PNR. So all pax were assumed to be adults. Hence, why we'd count if it were going to be close to limits. That could give you a nice deduction if you have a kid heavy flight.

Considering the weather was abysmal all over the Eastern US yesterday, it's far more likely the issue was additional fuel for deviations, holding and alternate requirements.

I flew DTW-RDU yesterday on a full A320 and we were also at our weight limit. That's only a 500mi flight. We had to wait at the gate a few extra minutes for dispatch to re-work our numbers (likely they just increase the taxi fuel burn because we were so close to limit).

Weight restrictions happen for lots of reasons (weather, tankering, MEL, IROPS), but cargo is rarely one of them. If it's going to be close, it's simply not loaded until they know they have enough capacity.