Is it true?

[bike21]

Last spring I was riding home from SBA in a CRJ jumpseat and I noticed the "arrival fuel" number was less than 1000lbs while we were holding short of the runway. I looked at the total fuel and it looked right so I figured it was either a flight plan problem or he forgot to reset the Perf Init number. I mentioned it, but for a second I felt a twinge of panic like "Oh crap, are we going to have to taxi back for gas? Am I going to have to embarrass this captain?"

There are a few "old-timers" who will use 'measured' vs 'predicted' for fuel planning. The 'measured' number isn't accurate until reaching cruise power setting and will give the sense of being under fueled. So that could have been the culprit. What was the outcome?

 

[Cal Goat]

There are a few "old-timers" who will use 'measured' vs 'predicted' for fuel planning. The 'measured' number isn't accurate until reaching cruise power setting and will give the sense of being under fueled. So that could have been the culprit. What was the outcome?

They simply hadn't updated the FOB in the perf init page after being fueled.

 

[bike21]

They simply hadn't updated the FOB in the perf init page after being fueled.

Cool. I'd definitely appreciate a heads up from a jump seater and encourage it.

Years back I was in the jump on a Mesa bird with the APU inop & the crew couldn't figure out why we weren't pressurizing after departure. I gave it a few minutes and asked them about the bleeds. Poor fellas, their brains were cooked. When we got to our destination the ground crew wouldn't plug in ground air so the crew said hell with it & took an ice cream delay.

 

[Cal Goat]

Cool. I'd definitely appreciate a heads up from a jump seater and encourage it.

Years back I was in the jump on a Mesa bird with the APU inop & the crew couldn't figure out why we weren't pressurizing after departure. I gave it a few minutes and asked them about the bleeds. Poor fellas, their brains were cooked. When we got to our destination the ground crew wouldn't plug in ground air so the crew said hell with it & took an ice cream delay.

Yeah, I'm not going to let something go unsaid if needs to be, even if I'm a guest in the house. Obviously, safety trumps ego and courtesy. Helps that I knew the airplane well.

 

[ASpilot2be]

The Anchorage controllers call out a lot of landmarks that someone that doesn't fly here often wouldn't know.

One time riding up front on a Delta flight the crew was trying to find traffic they were supposed to follow. I pointed out the location to them. We are all in it together.

 

[Rocketman99]

Not true, totally. Li cells don't have a memory like NiCD did, but they have a limited number of charge cycles. Typcially about 200-500, and they will lose a good bit of capacity near the end of that life cycle. Best life obtained by charging no more than 80%, and letting drain to 50% before charging.

If it is a device with a replaceable battery - who cares? They cost like $8, just replace them.

They also require computer chips to control charging, often times these limit how much they will charge a cell in a trade off between cell life and capacity, data sheets on the chips and batteries are the only way to know how a particular one is designed to behave.

True, they have a limited number of charge cycles. Important to note though, is that a cycle is a complete charge to discharge. Plugging your phone in to top off say from from 60-80% five times counts as one cycle not five. The high end of that scale is debatable depending on which article you read. The only universal truth so far is that there is no such thing as "conditioning" a battery, at least on an android device.

 

[drunkenbeagle]

True, they have a limited number of charge cycles. Important to note though, is that a cycle is a complete charge to discharge. Plugging your phone in to top off say from from 60-80% five times counts as one cycle not five. The high end of that scale is debatable depending on which article you read. The only universal truth so far is that there is no such thing as "conditioning" a battery, at least on an android device.

There is really only one reason to fully discharge lithium rechargeable batteries - and that would be determining capacity. You can't reliably determine the charge remaining looking at the open terminal voltage, as it is pretty flat around 3.5 volts, and then rapidly drops. So better designed devices will measure how much current they get out of the cell discharging from a full charge, and then use that to figure out how much charge capacity the cell still has. This is why the battery meters will seem to show 50% charge for hours, and then drop to almost zero in a few minutes. They can also be destroyed if operated below a minimum voltage (usually around 2.7 volts or so), so they are designed not to allow you to do that.

Cell life is directly related to the the depth of discharge for both Lithium cells, and lead acid cells. You can often get 5000 charge cycles if they are depleted no more than 20%, that might drop to 200 cycles depleting them 100%. Ball park numbers, they last about 5 times longer if you don't let them go below 50%.

(Example from an Li-Po datasheet)
Depth of Discharge: Cycles:
100% DoD 300 – 500
50% DoD 1,200 – 1,500
25% DoD 2,000 – 2,500
10% DoD 3,750 – 4,700

 

[Autothrust Blue]

There is really only one reason to fully discharge lithium rechargeable batteries - and that would be determining capacity. You can't reliably determine the charge remaining looking at the open terminal voltage, as it is pretty flat around 3.5 volts, and then rapidly drops. So better designed devices will measure how much current they get out of the cell discharging from a full charge, and then use that to figure out how much charge capacity the cell still has. This is why the battery meters will seem to show 50% charge for hours, and then drop to almost zero in a few minutes. They can also be destroyed if operated below a minimum voltage (usually around 2.7 volts or so), so they are designed not to allow you to do that.

Cell life is directly related to the the depth of discharge for both Lithium cells, and lead acid cells. You can often get 5000 charge cycles if they are depleted no more than 20%, that might drop to 200 cycles depleting them 100%. Ball park numbers, they last about 5 times longer if you don't let them go below 50%.

(Example from an Li-Po datasheet)
Depth of Discharge: Cycles:
100% DoD 300 – 500
50% DoD 1,200 – 1,500
25% DoD 2,000 – 2,500
10% DoD 3,750 – 4,700

What I'm getting from this is "don't bother to draw them down all the way if you can avoid it."

 

[Rocketman99]

What I'm getting from this is "don't bother to draw them down all the way if you can avoid it."

"Charge your damn phone."

 

[GaTechKid]

Jumpseaters are part of the crew so I always tell mine to speak up if they see something they don't like. I'd rather have my ego bruised than wind up violated or worse.

 

[derg]

Not only are jumpseaters part of the crew, they'll also get yanked into the hearing if the crew screws up.