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747-400 horizontal stabilizer tank question

Posted: Wed May 06, 2020 12:27 am
by AFROBINSON808
Hi,

Does anyone know how much the B747-400's horizontal stabilizer tank weighs when empty?

Thanks

Re: 747-400 horizontal stabilizer tank question

Posted: Wed May 06, 2020 2:44 am
by LH707330
Not much, really. It's just a sealed interspar region with a few bits of plumbing.

Re: 747-400 horizontal stabilizer tank question

Posted: Wed May 06, 2020 10:03 am
by AFROBINSON808
LH707330 wrote:
Not much, really. It's just a sealed interspar region with a few bits of plumbing.

Do you know how much it weighs in pounds (lb)?

Re: 747-400 horizontal stabilizer tank question

Posted: Wed May 06, 2020 12:03 pm
by AFROBINSON808
Does anyone know how much the tank weighs in pounds (lbs)?

Re: 747-400 horizontal stabilizer tank question

Posted: Wed May 06, 2020 2:13 pm
by 747classic
All the 747-400 series horizontal stabilizers are identical.
Only on the 747-400,-400ER and -400M you can optionally have a part of the horizontal stabilizer sealed and used as a tail fuel tank.
The added weight will be the weight of the installed sealant.
Only the piping, fuel valves and the vent surge tank add some extra weight.

Note : Also the 747-8I features a tail tank in the horizontal stabilizer.

Re: 747-400 horizontal stabilizer tank question

Posted: Wed May 06, 2020 3:18 pm
by AFROBINSON808
747classic wrote:
The added weight will be the weight of the installed sealant.


Do you have any pictures of the sealant?

Re: 747-400 horizontal stabilizer tank question

Posted: Wed May 06, 2020 3:52 pm
by AFROBINSON808
747classic wrote:
All the 747-400 series horizontal stabilizers are identical.
Only on the 747-400,-400ER and -400M you can optionally have a part of the horizontal stabilizer sealed and used as a tail fuel tank.
The added weight will be the weight of the installed sealant.
Only the piping, fuel valves and the vent surge tank add some extra weight.

Note : Also the 747-8I features a tail tank in the horizontal stabilizer.

My question is: How much does the entire tank weigh when empty, i.e. without fuel?

Re: 747-400 horizontal stabilizer tank question

Posted: Wed May 06, 2020 4:28 pm
by SAAFNAV
AFROBINSON808 wrote:
747classic wrote:
The added weight will be the weight of the installed sealant.


Do you have any pictures of the sealant?


It is probably just aviation-grade petroleum resistant compound, to seal all the joints. Just think of very expensive caulking, like for a bathroom.
Thick, nasty black stuff.

People can't really give you the weight, because the tank isn't really a tank like you would think. It just uses the available space, same as an aircraft wing. What does the tank weigh? Same as the wing. There's really no reason to know the weight of it.

Seems that people already said they don't know the specific weight. It won't help to keep on asking..

Re: 747-400 horizontal stabilizer tank question

Posted: Wed May 06, 2020 6:27 pm
by AFROBINSON808
SAAFNAV wrote:
What does the tank weigh? Same as the wing.


That's with the tank empty, right?

Re: 747-400 horizontal stabilizer tank question

Posted: Wed May 06, 2020 7:24 pm
by unimproved
There is no tank, you just make part of the stabilizer leak proof and add plumbing.

Re: 747-400 horizontal stabilizer tank question

Posted: Wed May 06, 2020 11:41 pm
by LH707330
Call it maybe 10 kg of sealant, plus fuel lines and pumps, gives a differential weight of maybe 100 kg for the whole system. As far as the stabilizer weight, you'd have to sort out what the spars and wing skins weigh.

Re: 747-400 horizontal stabilizer tank question

Posted: Thu May 07, 2020 3:06 pm
by 747classic
For some detailed info - about the 747-400 fuel system (ATA28), see :
http://203.72.21.28/arm/images/files/Do ... ___045.PDF

Look for effectivity "airplanes with horizontal stabilizer tank" at the lower side of the page(s).

2356 pages to study :white:

Re: 747-400 horizontal stabilizer tank question

Posted: Fri May 08, 2020 5:13 am
by JayinKitsap
747classic wrote:
For some detailed info - about the 747-400 fuel system (ATA28), see :
http://203.72.21.28/arm/images/files/Do ... ___045.PDF

Look for effectivity "airplanes with horizontal stabilizer tank" at the lower side of the page(s).

2356 pages to study :white:


A quick bedtime read. I looked at it for a good while, got to page 163 a few more to go.

I found the horizontal stabilizer has a capacity of 3,300 gallons, which is 440 cubic feet. Looking at the tank outline in the above reading material the tank is about half of the stabilizer area, so around half of the weight but what is tank and what is structure not in the tank seems moot. Anyway around 3,500 lbs for the portion of the stabilizer that contains the tank.

Table 9-2 in Torenbeek gives the ratio of horizontal tail surface/wing surface as 0.267 in table 9-2, for both the 100 and the 200. Wikipedia gives the wing area as 511 m2, so horizontal tail area is 136 m2.

In the same book table 9-3, vertical tail surface ratio is given as 0.196 so vertical tail area is 100 m2.

https://aviation.stackexchange.com/ques ... ng-747-400

Weight for the 747-100/200 is therefore:

Horizontal stabiliser = 136/236 * 11,850 = 6,830 lbs
Vertical stabiliser = 100/236 * 11,850 = 5,020 lbs
Above weights is with all equipment installed: actuators, hydraulic system lines, rudder & elevators, stabiliser incidence electric motors etc.

Re: 747-400 horizontal stabilizer tank question

Posted: Fri May 08, 2020 2:36 pm
by AFROBINSON808
Two new questions regarding the 747 stabilizer tank:

1) What specific changes were made to the tail assembly to accomodate the tank?
2) On stock 747-400's operating without the stabilizer tank, is the entire tank removed, or just the outboard sections of the tank?

Thanks

Re: 747-400 horizontal stabilizer tank question

Posted: Fri May 08, 2020 6:31 pm
by DL_Mech
AFROBINSON808 wrote:
2) On stock 747-400's operating without the stabilizer tank, is the entire tank removed, or just the outboard sections of the tank?


unimproved wrote:
There is no tank, you just make part of the stabilizer leak proof and add plumbing.


:white:

Re: 747-400 horizontal stabilizer tank question

Posted: Fri May 08, 2020 7:05 pm
by trpmb6
I suspect you're doing some sort of mod or some sort of work relating to this. Relying upon forums for data in such is bad business. Do your own research and ensure the data is sound.

From my personal perspective, I would never approve a drawing or mod without proper data sourcing. Use this forum as a guide to get you there, but should seriously do more diligence. The data is out there.

Re: 747-400 horizontal stabilizer tank question

Posted: Fri May 08, 2020 7:32 pm
by spudsmac
AFROBINSON808 wrote:
Two new questions regarding the 747 stabilizer tank:

1) What specific changes were made to the tail assembly to accomodate the tank?
2) On stock 747-400's operating without the stabilizer tank, is the entire tank removed, or just the outboard sections of the tank?

Thanks


I don't know why you keep asking this question when people tell you it's literally just the inside of the horizontal stab sealed up with plumbing.

It's like asking a auto mechanic how much does the car cabin weigh. It's literally just the inside of the car. You can't weight it and you can't remove it without destroying the car.

Jeeze....

Re: 747-400 horizontal stabilizer tank question

Posted: Fri May 08, 2020 9:35 pm
by Ty134A
The weight of those things is not "existing". There is no such thing as weight for an auxtank like there is for a jet engine or a coffee maker. If you want such a thing and you order it, it will get installed. Then the empty plane is going to finishing and receives all the nice airline stuff such as seats and coffee makers. Then it get's to be weight out. So for example imagine an airline ordering 2 frames of 747-400. One with the trim tank, the other without. They get the same finishing and cabin fitting. Everything is the same except when they get weight. Then you'll end up with one slightly heavyer 744. And that still is of no importance. The plane gets it's weight measurements for the determination of it's CG and not so much for the weight of a few kilos of sealant and plumbing.

Re: 747-400 horizontal stabilizer tank question

Posted: Sat May 09, 2020 6:38 am
by SAAFNAV
Ok let's try one more time:

Suppose you have a car with a trunk/boot. Suppose you look at the trunk and think 'hey, let's seal this sucker up, so I can have a long range tank'.
So you use a lot of sealant, you add one pipe and maybe a pump.

Then someone comes around and keeps asking what does the tank weigh?? How would you answer him that question? It is a ready-made structure just used now to be useful. You cannot take it out and weight it, and it is of no use knowing what it weighs. What part of that is actually car that you can't do without, what is 'tank'.
On a plane that weighs 100's of tonnes, the weight of the pump is negligible.

I do hope you're not working on any planes close to me, that's for sure.

Re: 747-400 horizontal stabilizer tank question

Posted: Sat May 09, 2020 8:56 am
by JayinKitsap
AFROBINSON808 wrote:
Two new questions regarding the 747 stabilizer tank:

1) What specific changes were made to the tail assembly to accomodate the tank?
2) On stock 747-400's operating without the stabilizer tank, is the entire tank removed, or just the outboard sections of the tank?

Thanks


The tanks use the skin of the horizontal stabilizer just like a wet wing does. Look at section 5 in the attached.
https://www.aircraftsystemstech.com/p/w ... s-are.html

The spars, ribs, and stringers form the structure of the wing. The skin is applied over this on the top, bottom and side of the wing. Parts of the wing just contain air, those compartments will include all the wiring and most piping. Other parts are filled with fuel. So the only added weight of the tank is the where the ribs and spars that form the sides of the tank within the wing are solid, not with openings. Inside the tank the openings are designed for the fuel to flow to the fuel inlet. Probably 95% of the tank weight is structure that would be there anyway.

So the only changes was making the spar and rib webs solid.

On all 747's if the stabilizer tank is taken out of service it would be drained and cleaned, an open vent to the space would be added, probably the original tank vent. Fuel piping from the tank to the fuel system would be removed if in accessible spaces.

Re: 747-400 horizontal stabilizer tank question

Posted: Mon Jun 01, 2020 9:54 am
by 747classic
Found this KLM 747-400 maintenance video from Hangar 14 at AMS, with some interesting shots from the -400 stabilizer tank acces panels,
See : https://www.youtube.com/watch?v=MSr04_Y ... e=youtu.be

Time 07.08 minutes : stabilo tank acces panel
Time 07.28 minutes : stabilo spindle + tank acces panel

Re: 747-400 horizontal stabilizer tank question

Posted: Mon Jun 01, 2020 9:07 pm
by 889091
747classic wrote:
Found this KLM 747-400 maintenance video from Hangar 14 at AMS, with some interesting shots from the -400 stabilizer tank acces panels,
See : https://www.youtube.com/watch?v=MSr04_Y ... e=youtu.be

Time 07.08 minutes : stabilo tank acces panel
Time 07.28 minutes : stabilo spindle + tank acces panel


Great find 747classic. Thanks for sharing. Pretty sad to see them chopped up at the end....

Re: 747-400 horizontal stabilizer tank question

Posted: Tue Jun 02, 2020 6:29 am
by JayinKitsap
747classic wrote:
Found this KLM 747-400 maintenance video from Hangar 14 at AMS, with some interesting shots from the -400 stabilizer tank acces panels,
See : https://www.youtube.com/watch?v=MSr04_Y ... e=youtu.be

Time 07.08 minutes : stabilo tank acces panel
Time 07.28 minutes : stabilo spindle + tank acces panel


Really cool video, learned a lot. Lots of questions on things now.

One question, on the 747 era all of the control wiring, what is the minimum wire gauge. In facilities, the smallest wire within the panel is #18, field wiring #16 so it is sturdy enough to not fail. This wiring looks quite tiny in the electronics bay.