Hi real and virtual pilots!
How to fill fuel in tanks, when I need for example only 80% of fuel (about 37500 lbs, assuming flying without external tanks). Should I fill every tank in 80%?
http://img225.imageshack.us/img225/6779/200606201758554fq.th.jpg
Or rather fill four main tanks in 100% an two aux tanks in about 23%?
http://img225.imageshack.us/img225/9715/200606201757079ca.th.jpg
And what if I am flying with external tanks because I need for example 56200 lbs of fuel? Should I fill internal tanks in 100% and externals in 50%?
http://img57.imageshack.us/img57/3062/200606201803373wc.th.jpg
Or should I fill every tank in about 84%?
http://img153.imageshack.us/img153/682/200606201805499jj.th.jpg
How would it be in reality?
regards,
eagle
PS Forgive me my poor english ::)

When I use to flight prep the RAF Hercs we would generally fill the main 4 tanks then use the external and only use the Aux tanks when really required. You would try and leave the main tanks as full as possible to try and stop the wing tips flexing too much and cause additional stresses.

Dax

Thank you very much for so fast answer :)
Regards,
eagle

On one trip to the South Pole one of the Herc tankers came back with a fuel inbalance. They had emptied the front two cargo bay tanks and left the rear two full. We filled the cockpit with 20 guys and the pilot had the four engines in mid range power as I hung out of the right hand para door and defueled the rear tanks. To top it off we were all on our way to a squadron dinner so we were all dressed in three piece suits. Most smartly dressed see in team ever.

Things you do when you were young.

Dax

First thing to remember is to keep 0 to 1000 pounds more in the outboard main tanks. Keep all semetrical tanks within 1000 pounds of each other.  The aux tanks dont matter, you can have 1 full and the other completly empty because its considered a fuselage tank not a wing tank.

Now if your flying the P model things are a little different.  They have the refueling pod out on the outboard portion of the wing, so the fuel distribution changes.  They estimate that the pod weighs 1000 lbs, so you need to keep 0 to 500 lbs more fuel in the inboard main tanks (2+3)

Normally we dont like to put more than 7500 in 1 and 4 and leave 2 and 3 at 7000.  If its the P model we keep the mains at 6800 in 1 and 4 and 7200lbs in 2 and 3 to keep the wings balanced.

Then the aux's always get filled first and then if the externals are needed for the specified fuel load we will use them.

The reason the rescue squadron like mine want no fuel in the externals is so they can do asault landings and other different aproaches without putting a retarded amount of stress on the wings.  

And not to mention the External tanks SUCK!!!  Always have somethign wrong.

Oh by the P model I mean the KC-130 here.  Sorry I work on the P's and they are just about the same thing.

Thanks for informations and interesting story!
Cheers,
eagle

hondaguru wrote on Jun 21^st, 2006 at 4:01pm:

First thing to remember is to keep 0 to 1000 pounds more in the outboard main tanks. Keep all semetrical tanks within 1000 pounds of each other.  The aux tanks dont matter, you can have 1 full and the other completly empty because its considered a fuselage tank not a wing tank. Now if your flying the P model things are a little different.  They have the refueling pod out on the outboard portion of the wing, so the fuel distribution changes.  They estimate that the pod weighs 1000 lbs, so you need to keep 0 to 500 lbs more fuel in the inboard main tanks (2+3) Normally we dont like to put more than 7500 in 1 and 4 and leave 2 and 3 at 7000.  If its the P model we keep the mains at 6800 in 1 and 4 and 7200lbs in 2 and 3 to keep the wings balanced. Then the aux's always get filled first and then if the externals are needed for the specified fuel load we will use them. The reason the rescue squadron like mine want no fuel in the externals is so they can do asault landings and other different aproaches without putting a retarded amount of stress on the wings.   And not to mention the External tanks SUCK!!!  Always have somethign wrong. Oh by the P model I mean the KC-130 here.  Sorry I work on the P's and they are just about the same thing.

We use to avoid using the AUX tanks. They leaked fuel quicker than you could put it in.

Hi,

>We use to avoid using the AUX tanks. They leaked fuel quicker than you could put it in.

was it the -B model you used to fly?

Btw we  have an additional limitation - 1500 max difference wing-to-wing (not counting AUX tanks)

regards

It was the RAF's "K". They are basicly an "E" with "H" wings and other various bits.

Dax

Dax,

ah, ok. I thought that aux leaks were mostly a -B and earlier models problem.

regards,

hondaguru wrote on Jun 21^st, 2006 at 4:01pm:

First thing to remember is to keep 0 to 1000 pounds more in the outboard main tanks. Keep all semetrical tanks within 1000 pounds of each other.

Your limits sound slightly different than ours.

Outbds > Inbds      500-1000
Symmetrical Tanks      <1000(exc Aux)
Wing-to-Wing      <1500(exc Aux)

I personally will usually load up 7000 in the outboards, 6000 in the inboards, and 5000 in the aux's for regional flying.  

wrote on Jun 22^nd, 2006 at 5:40am:

Dax, ah, ok. I thought that aux leaks were mostly a -B and earlier models problem. regards,

This discussion brings up an interesting question. I know that when preparing a vehicle for air transport that all vehicle tanks and external Jerry cans are only partially filled to allow for fuel expansion at altitude. I assume that aircraft would experience similar expansion problems unless sufficient fuel is burnt off getting to altitude to compensate for the expansion? Any rules of thumb here? In my mind it would certainly seem to answer why auxiliary tanks filled to capacity would leak.  :-?--- Ziggy

Not on Hercs. Herc fuel tanks are vented to atmosphere. Unlike a fighter which requires a pressured fuel system to keep fuel flowing in aerobatics a Herc's is just pumped from the tank to the engines. Their is almost no pressure in the tanks at all. That is why the external tanks have two pumps, keep fuel flowing if one fails.

The main reason why the RAF Herc tanks leaked is they are flexible bag tanks. They need to be kept wet at all times to stop them cracking and leaking. Never happend in the RAF. They we so seldom used that they would dry out especially around the fixtures and fitting. Small leaks would start and leak into the dry bays around the tank and come out of the drains at the back of the main undercarriage.

Dax

Hi,

>Not on Hercs. Herc fuel tanks are vented to atmosphere. Unlike a fighter which requires a pressured fuel system to keep fuel flowing in aerobatics a Herc's is just pumped from the tank to the engines. Their is almost no pressure in the tanks at all. That is why the external tanks have two pumps, keep fuel flowing if one fails.

A by-effect of what Dax is saying is that you might have a different problem though - fuel "boil-off" during rapid climbs. Since the tanks are effectively unpressurized, a rapid climb might cause air trapped (and dilluted) in the fuel to expand, causing fuel "foam" to be created (sort of like the effect you get when you shake a coca cola bottle and then rapidly unscrew the cap).
This can cause some loss of engine power, mainly when the fuel is gravity fed. The actual effect depends on various factors (which I do not recall - initial fuel temprature and rate of climb spring into mind). The AFM is pretty detailed on this subject.

Regards,