Most of the time my little plane....barbie jet as I call it...can take all the passengers, bags and fuel safely from point A to point B.
Every now and then weather or a MEL comes into play and complicates things.
Right now I'm sitting in a Hampton Inn in a crappy city in no where anyone should live USA. I have one leg home tomorrow for Thanksgiving.
Last night, about forty minutes before departure, the gate came down and asked if she knew we were weight restricted....but one passenger. I said I wasn't and then took a look at the numbers. Sure enough due to low ceilings at the destination we had an alternate of flying all the way back to the Hub. It was a short one hour flight. The Captain was away getting dinner.
I told her I would see what I could do. The restriction was that we were landing weight limited. To keep things easy lets use the following:
Basic Empty Weight 40,000 lbs
Release Fuel: 6996 lbs
Minimum Takeoff Fuel: 6450 lbs
Maximum Landing Weight: 55,000 lbs
Actual fuel on board at the time was 7100 pounds. I immediately started the APU. I transmitted exactly 6996 pounds to the "load room". The load room is really a computer system that works out weight and balance. I then called the load room over the radio and inquired about the weight restriction. They stated they planned on 2500 pounds of cargo due to several military passengers. There were 47 paying passengers waiting.
My airline assumes each passenger weighs 184 pounds in winter (they weigh 10 pounds less in summer). Kids weigh 76 pounds. They were restricting it to 46 passengers due to all the cargo. Taking the above numbers they planned on a takeoff weight of 57,964 pounds.
En-route fuel burn + taxi = 2980 pounds. Taking a ramp weight of 57,964 - 2980 fuel burn = 54,984.....or 16 pounds to spare.
Taking things further the airline assumes each checked bag weighs 30 pounds unless it is marked heavy (being over 50 pounds) then they assume it weighs 60 pounds. My barbie jet overhead bins can't take normal carry on bags. The bags checked plane side are assumed to weigh 20 pounds. If the bag is able to be brought on board and stowed it weighs zero pounds. Keeping up?
The one passenger that was going to be left behind was going to his Grandmothers funeral. He had problems getting to the airport and missed his earlier flight. If he was denied boarding the airline owed him NOTHING.
We had no control over checked bags. We could "control" kids on board and valet bags that aren't checked plane side.
The Flight Attendant was very forgiving on bags being brought on. If they could safely fit she let them on. Nine minutes to push we got the final numbers. We were 240 pounds under PLANNED weight.
I called the load room and asked why the passenger wasn't on board. They stated they didn't want to take a delay. I looked over at the Captain and he said, "if you don't mind can you run up there and bring the passenger back with you." At this point we had 7 minutes.
I bolted up from my seat and sprinted up the jet bridge. There alone in the boarding area was a very upset twenty-something guy. I just pointed to him and said, "Hey, let's get you to where you need to be."
He was surprised as was the gate agent. She quickly began typing. Thankfully he only had a backpack. The Flight Attendant told him to sit where ever he wanted. The agent rushed down the final paperwork and we blocked out with 2 minutes to spare.
We weren't done though. We had a very short taxi and didn't use all the planned taxi fuel. I had to fly in fuel burning mode to make sure we were below 55,000 pounds on landing. With a shallow climb and early descent I was 100 pounds under while 20 miles out.
It's all funny math. The plane knows how much it weighs. On final approach I've had situations where I needed much less thrust than normal as we are lighter than we think we are. I've also needed much more thrust as we are heavier than we think we are. The low speed awareness cue is very telling. The margin between VREF and the TOP of the low speed cue (not stall speed!) is normally 5-10 knots. Sometimes it's 1 or 0 knots. That's when we are heavier than we think we are. Nonetheless we have to abide by the funny numbers.
In and done. I then spent ALL day at a hotel. Tomorrow is a very early 4:15 AM van for a 5:15 AM departure and a 6:09 arrival. I'm then off until the 7th.