Calculating max pax/bags out of a max payload

mrezee

Living the dream!
Hey all, I'm in my 3rd month of dispatching at a 121 that flies CRJ2's and 9's. I've been feeling pretty good about it and learning a lot so far. However, the one area I still want to improve on is calculating a max payload and weight restricting.

In our software (the ever-so-popular Sabre dispatch monitor), the system pulls the passenger booking total and automatically calculates for each passenger the standard weight (190 in the summer) plus a bag and a half (30+15) to equal out 235/passenger. Therefore, for a CRJ200 (the CRJ900 will automatically calculate the max payload and split it into max pax/bags on the ramp release), the payload assumed for a full 50 passengers is 11750 lbs. Frequently when it's full and especially when you add on a destination alternate, it either pushes you over max landing weight or leaves you room to take about 100 extra pounds of gas. So I've been putting on the contingency/hold fuel I want to put on, and having the system calculate the max payload I can take with that much fuel (putting MP in the HowFP box, for those that are familiar with Sabre DispMon). Obviously if the flight is booked full or oversold, I need to call the station and give them the payload restriction in max pax/bags they can take.

I've observed my fellow dispatchers use a few different methods to do this during my OJT. For example's sake, let's say the max payload that Sabre spits out is 11,020 lbs.
  • The first guy I trained with divided the payload by the system-calculated per-passenger weight with 1.5 bags/person included (235). In this example, it gives us 46.894. So he would call the station and restrict them to 46 pax and 46 bags.
  • The second guy I trained with arbitrarily dropped the payload in the flight plan calculation. So he would just manually change the 11750 payload in the CFP to 11000. He said it's never backfired on him and that the system grossly overestimates the payload every time.
  • The third guy calculated the total passenger weights based on standard weight (190x50=9500). He then subtracted 11020-9500=1520, which should be the max weight of all the bags. Finally, he divided 1520/30=50.667. So he would tell the station that the flight was restricted to 50 pax and 50 bags. Should the MP have been lower, he still would have kept the restriction at 50 pax and just lowered the max number of bags.
  • And finally, the guy who sits next to me now simply reads the station the max payload of 11,020.
We never learned about payload restrictions in dispatch school, and during training we just briefly touched on it. I feel pretty comfortable with most other dispatching concepts but never really felt too comfortable with this. I don't know if there's a correct or a "preferred" method, but I'm interested to see what everybody's methods are, and if you can break it down into a step-by-step, that would be great. I really want to learn and be comfortable with it as we go into the winter months with contaminated runways, more alternates, etc. Thanks for any input you have.
 

PHL_Approach

Well-Known Member
The second guy I trained with arbitrarily dropped the payload in the flight plan calculation. So he would just manually change the 11750 payload in the CFP to 11000. He said it's never backfired on him and that the system grossly overestimates the payload every time..
That was my philosophy for 4 years at the regional I was at. I'm having a very hard time remember what weights I would go down to exactly cause it's been 18 months since I've had to use Disp. Mon but I think with Summer weights it would calc like 11300 and I would take it to 10800 and Winter weights it would run about 11900 and I would take it to 11300. Anything lower than 10700 in either season and you were very likely taking one body off. The number is very bloated because a full plane of people are not each checking a bag. Certain cases in or out Mexico or the Caribbean you need to be more mindful because yes more people check bags and yes most natives go into heavy weights range for their bags.
 

N77022

Descending Via
That was my philosophy for 4 years at the regional I was at. I'm having a very hard time remember what weights I would go down to exactly cause it's been 18 months since I've had to use Disp. Mon but I think with Summer weights it would calc like 11300 and I would take it to 10800 and Winter weights it would run about 11900 and I would take it to 11300. Anything lower than 10700 in either season and you were very likely taking one body off. The number is very bloated because a full plane of people are not each checking a bag. Certain cases in or out Mexico or the Caribbean you need to be more mindful because yes more people check bags and yes most natives go into heavy weights range for their bags.
This. I've been dispatching 145XR, LR, and 135 (who could that be?). If the flight is oversold, and headed to Veracruz from Houston by way of San Antonio due to storms around Brownie, than I'm knocking the Payload box from 11688 or whatever it calculates, to 11000 or 10800 if I'm desperate for every drop. After that I'm HowFP with MF for max fuel.

Then, to help clarify what the fuel is meant to be used for, I'll go back through, and whatever additional fuel was thrown into SCF/TNK I'll put into HOLD. That last step is more of a company preference, which I agree with from a pilot perspective. If I was a captain I'd appreciate the fuel being put into the column for which it's intended to be used. I don't want to be dispatched into thunderstorms with 0 Hold and 2300 Scf/tnk. Even though it's still technically the same ramp fuel.
 

Mainline_or_bust

Airplanes fly on PFM, Change my mind
Keep in mind that the restriction that you give the flight is only for planning purposes only. If the flight is a 50 seat 200 then to restrict them to 46 and 46 means that a gate gent is going to be looking for 4 vols. They will also be smart enough to allow ANY bag that will fit in the overhead to be placed there. I used to even encourage pax to try while giving them a tag just in case. In the end there may be extra bags that you didn't account for so only 44 may be able to go, likewise there may be less and 50 could go. The 200s are always CG forward so if there isn't very many bags it is possible to have to boot pax from Zone A/1. I've seen it happen twice. They do stand right behind the pilot, or run between the gate and CA to see exactly how many they can take. Typically a good agent will give current PAX count and bag count upon arrival to get an idea right then. Your restriction will get the ball rolling at the ticket counter and gate as far as volunteers.

My answer, guess, round down and don't sweat it.
 
F

Flying Saluki

Guest
Understand that the purpose of a payload input into Sabre (or any dispatch software) is strictly for the purpose of enabling the software to select the correct fuel burn tables from which to calculate a burn. On a given flight, an aircraft that takes off at 50,000 lbs. is going to burn more fuel than an aircraft that takes off at 40,000 lbs. Your job is to ensure that the flight plan represents a reasonable approximation of the actual conditions, not to determine the final make-up of passengers and cargo that gets loaded on the aircraft. That is for the flight crew and load planners to determine.

The way I see it, your order of operations is to determine the minimum fuel supply necessary for the flight. That will drive the final payload, the make-up of which is determined by the flight crew and load planners.
 

Flagship_dxer

Legacy Airline Dispatcher
The way I see it, your order of operations is to determine the minimum fuel supply necessary for the flight. That will drive the final payload, the make-up of which is determined by the flight crew and load planners.
Some airlines dont have load planners. Flight crews get to the aircraft and look at the release maybe 45-30 minutes prior to departure. In this time, the station needs to know how many they can take so they dont board everyone and have to offload a bunch once the pilots realize they are way overweight.

Ive worked for a carrier where the dispatcher did all the load planning. You are correct in saying dispatchers shouldnt be part of that but at some of the regionals sadly they are.
 

Salkadi

Well-Known Member
Just to throw my 2 cents into the mix...

When I was at the regionals, we used the same weights that you mentioned per passenger (190 standard pax weight + 30 for checked bag + 15 half bag weight.) This seems to be pretty standard for planning, at least at the regionals. When I dispatched the CRJ-200's, I would bump the payload from 11,750 to 11,000 like you mentioned one of your trainers did. My reasoning behind this was that if you did the math on it, all I was doing was eliminating the half bag per pax. I was only planning a total of 50 pax and 50 bags. I only did this when I needed the weight though.

Same thing for the CRJ-900, but that was less common since it wasn't as weight restricted.

I will also note that I used this as a starting point. If I could add weight back afterwards, or if I needed to take more weight off then I would. But I knew if I went below 11,000 then I would be bumping actual passengers and not just the half a bag.
 

bilbolinski

Well-Known Member
This is an interesting read OP as I am in a similar situation as yourself being a green-horn dispatcher; this question has popped in my head too and I have seen similar theories as well.

Our shop uses slightly different weights due to a lack of a carry-on baggage program, but regardless... I like to confer with the station first to see how many people are actually checked in (closing in on the time the release is due) and what we're actually looking at for checked bags. I've seen others just limit the payload and can understand with experience they can take a very educated guess at what the pax/bag count will be for a certain city pair. Personally, I think it is just "nice" to try and work with the station as well.

But at the end of the day the fuel you need for WX is the fuel you need for WX. If that means bumping someone then that's the sad reality.
 

pljenkins

Resident Knucklehead
Ah the old CRJ-200. If it ain't clear and a million and the density altitude wasn't below 3500 feet or it was ISA+anything, you were leaving folks behind. Good times, those. Good times.

Anyway, back in the day I would fuel for the mission, then put the payload on. I would rather get 35 people to the destination then 50 people to the alternate. It wasn't always the popular way to do it, but when I was working 75+ flights in a shift with bad weather, I didn't have time to sweat every flight on the desk. Fuel for a solid plan, seat who you can, let the bean counters figure out that you can't pull off Denver to Edmonton with an alternate in a -200 at any time ever.
 

Flagship_dxer

Legacy Airline Dispatcher
Fuel for a solid plan, seat who you can, let the bean counters figure out that you can't pull off Denver to Edmonton with an alternate in a -200 at any time ever.
This is something that happens at all airlines. Management at all airlines tries to push the range of how far they can fly any plane with maximum payload. Many if not most dispatchers and pilots myself included try hard to not let management's decisions cause people to not be able to travel where they want to go. Whether it be revenue or non-revenue, it sucks having to offload payload for whatever the reason. While there are good reasons to bump payload, it is our job to make a decision on when it is reasonable to fly with reduced contingency fuel in order to maximize payload.

The downside to all this is that every time we do make the payload work and get most if not everybody on, it boosts the positive numbers that the bean counters look at. It is true that even if we just threw on the fuel regardless of payload that the bean counters might still keep that aircraft on the route. But they might also choose to get rid of the route altogether instead of upgauging. We do encourage management to keep adding more similar long range and challenging routes by helping to get everyone on. It is a really bad position to be in. It is our job to make these things work even if it is a terrible idea to be doing such flying. We are in the business of carrying payload, not gas but we need the gas often to operate safely. Its kind of a big catch 22.
 

pljenkins

Resident Knucklehead
Indeed. No one likes to leave revenue behind, myself included. We are in the business to make money. I'm afraid I've been pigeon-holed into the category of "screw the customers, I want gas". Anyone who has worked with me knows that's not true, so I'm not going to try to defend myself here. My point is, I've seen a lot of dispatchers put themselves in very precarious positions because they didn't understand either their role, their authority, or their duty. Sometimes as dispatchers we have to make unpopular decisions. Failure to recognize those times where that is necessary puts you and your co-workers in precarious positions, costs the company more money then they would have lost compensating displaced passengers, and in some instances compromises safety. Getting everyone where they need to be on time and under budget is and should be the goal of everyone involved in the operation, but it's important to recognize when meeting that goal is impossible or unwise and work instead to come up with a solution that minimizes the damage and disruption to the customer and the operation. Diverting is expensive, and dispatchers need to seriously consider whether they are "rolling the dice" when it comes to operational decisions. If at any point in the decision process either the dispatcher or the pilot utters the word "hope", and you haven't come up with an alternative plan, you're rolling the dice. In a scenario like that, you'd better hope you don't find yourself having to answer questions to the Feds. I myself am far more comfortable having to explain why I was cautious then why I was not.
 
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