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Author Topic: 980 Won't Fill to Capacity  (Read 2933 times)

donv

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980 Won't Fill to Capacity
« on: October 20, 2015, 11:33:42 pm »
My 980 has the long range tanks. I know this because, on the pre-buy, we opened up the panels and looked at the bladders.

Yet, for the past 4 years, I cannot get more than 3,000 pounds in the airplane. Lately, it's been more like 2,900 (but that might be due to warm fuel). We calibrated the fuel gauges, so I know they're right, and in that process took it down to completely empty and filled it up-- 3,000 pounds.

Anyone ever seen this before?

Adam Frisch

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Re: 980 Won't Fill to Capacity
« Reply #1 on: October 21, 2015, 02:30:43 am »
Could the bladders be wrinkled or not connecting properly?
Slumming it in the turboprop world - so you don't have to.

ghancock

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Re: 980 Won't Fill to Capacity
« Reply #2 on: October 21, 2015, 08:49:13 am »
First thought would be whoever put them in last didn't get them all straightened out and they can't fill up completely.
--glenn
You can't win an argument with an ignorant person,  they'll just drag you down to their level and beat you with experience.

donv

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Re: 980 Won't Fill to Capacity
« Reply #3 on: October 21, 2015, 02:58:48 pm »
Wrinkled bladder could be an issue. We have looked at them from the outside, and they appear to be fine, but I should follow up on that.

donv

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Re: 980 Won't Fill to Capacity
« Reply #4 on: October 27, 2015, 05:37:56 pm »
I was chatting with Norm Ralston yesterday, and he suggested a vent problem. I'm going to follow up on that, as I think he might well be on to something.

Adam Frisch

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Re: 980 Won't Fill to Capacity
« Reply #5 on: October 27, 2015, 05:47:04 pm »
Could be.

I had a cockroach nest completely blocking my fuel vent on the old 520 once. Pure chance I found it. After that I was always adamantly clearing fuel vents on pre-flight.
Slumming it in the turboprop world - so you don't have to.

donv

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Re: 980 Won't Fill to Capacity
« Reply #6 on: July 07, 2016, 12:33:09 pm »
At the 150 hour, we went all through the fuel system. Everything seems to be as it should be, yet going from empty to completely full (during the calibration of the fuel gauges), it took only 420 gallons.

No one, including Geoff at Twin Commander, can figure out where the missing fuel is.

Vents are all good, long range tanks are there and fill with fuel, foam in the bottom of the bladders seems to be correct. They even measured the distance to the fuel fillers, to see if maybe they were placed incorrectly at the factory... nope. They're in the proper place.

Adam Frisch

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Re: 980 Won't Fill to Capacity
« Reply #7 on: July 07, 2016, 01:42:27 pm »
Could you send in a probe camera and see if there's creases somewhere or something?
Slumming it in the turboprop world - so you don't have to.

donv

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Re: 980 Won't Fill to Capacity
« Reply #8 on: July 07, 2016, 02:36:54 pm »
They did that. All looked good.

Could you send in a probe camera and see if there's creases somewhere or something?

Adam Frisch

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Re: 980 Won't Fill to Capacity
« Reply #9 on: July 07, 2016, 04:23:39 pm »
Bizarre.

Checked center tank? Problem could be there maybe.
Slumming it in the turboprop world - so you don't have to.

donv

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Re: 980 Won't Fill to Capacity
« Reply #10 on: July 07, 2016, 06:43:52 pm »
The 980 fuel system is a little bit different. It has a wet wing outboard, and four bladders on each side, inboard. They looked at all the bladders, as well as all the tubes connecting them. It's also odd in that the missing fuel is symmetrical-- you might expect to have an issue on one side or the other, but not both together.

Bizarre.

Checked center tank? Problem could be there maybe.

Bruce Byerly

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Re: 980 Won't Fill to Capacity
« Reply #11 on: July 07, 2016, 09:44:10 pm »
54 gallons missing ??  :o

I've had one that was indication and another now which I don't know what the facts are yet.  But 50+ is huge - I'd guess the tanks are missing.

donv

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Re: 980 Won't Fill to Capacity
« Reply #12 on: July 07, 2016, 11:57:20 pm »
Nope. That was the first thing we checked. They are definitely there, and definitely filling with fuel.

54 gallons missing ??  :o

I've had one that was indication and another now which I don't know what the facts are yet.  But 50+ is huge - I'd guess the tanks are missing.

Bruce Byerly

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Re: 980 Won't Fill to Capacity
« Reply #13 on: July 09, 2016, 07:26:50 pm »
Nope. That was the first thing we checked. They are definitely there, and definitely filling with fuel.

54 gallons missing ??  :o

I've had one that was indication and another now which I don't know what the facts are yet.  But 50+ is huge - I'd guess the tanks are missing.

Yeah where is the air hiding? Wrong part number fuel cells could be somewhere in the system.  Full, complete and total defuel followed by refuel by weight (checking quantity while you do it) with temp density noted would be the only thing to give me confidence in it.  54 gallons is 100% of reserve in some cases!  :o

Bruce Byerly

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Re: 980 Won't Fill to Capacity
« Reply #14 on: July 25, 2016, 11:50:26 pm »
Don, I was taking to Mike G in Indy and he recalled planes being short of capacity when new. In fact the plane I was picking up, a 1000, has one wing that differs much more than I would have expected from the other.  I can get the numbers for you.  Not a great answer but makes me want to ask Geoffrey P at Twin if he recalls any solutions.