DC9 fuel loading question

[flugkapitan]

Greetings,

I was wondering if anyone has any info about the proper way to load the tanks. For example the 30 series has 3 tanks. It seems from the few times I've flown it fuel is drawn from the center until a certain point (almost empty), then from the main tanks. I'm not sure how it works for a plane that has more than 3 tanks.

My flights are of the shorter variety so I don't need to tanker a bunch of fuel. What would be the proper sequence for loading tanks for each of the types/series?

Thanks,
Scott

[aerofoto - HJG Admin]

I don't have any specific fuel loading info on any of the DC9's .... other than that which indicates the DC9-10 through -30 series were a "basically" 3-tank configuration (1 notable exception though being the PLAYBOY aircraft which was equipped with additional tanking giving it trans-Atlantic range) .... and the later DC9-40 and -50 series aircraft seeming to have 4 and 5-tank configurations depending on airline/operator option.

In section 4 of my DC9 PANEL INSTALLATION & HANDLING NOTES posting .... I've provided "basic" FS flying guides for each of our DC9 series aircraft. These include the fuel adjustement necessary in order to set each of these aircraft at their MGTOW .... without reducing payload. As these fuel recommendations indicate, I keep most of the fuel outboard. Whether that's right, or, wrong procedure-wize .... I can't say .... BUT .... it worked fine for me during all of my quite lengthy test flights over the past 10 months.

Mark C
AKL/NZ

[flugkapitan]

Hi Mark,

Thanks for the reply. I'll play with fuel loads and see what happens.

I did notice with the -30 series, that after I had installed one and loaded it into FS9, I changed the fuel load by emptying the central tank and keeping the mains full. The A/C didn't like that very much as the engines promptly began to wind down I would surmise the same will be true for the other series that have more tanks.

Regardless, thanks to you and the crew for such a great package!

Cheers,
Scott

[aerofoto - HJG Admin]

Regardless, thanks to you and the crew for such a great package!

Thanks foor that "FLUGKAPITAN"

Have a look at those "basic" flying guides which appear in "SECTION 4" of my DC9 PANEL INSTALATION & HANDLING NOTES. "IF" you configure your fuel loading as recommended within these guides .... then you shouldn't have any problems at all.

The only thing you then have to do is .... go to the Overhead Panel .... and make sure all 6 "Fuel Pump" switches (within the OH Fuel section) are selected "ON".

This should all see you right !

Mark C
AKL/NZ

[alemaobaiano]

Scott

I seem to remember from my MD80 material (which should be pretty similar) that you can load wings first, then centre if needed. I flew the -20 yesterday with centre empty and the centre pumps off, no problems at all.

TTFN

[christrott]

All DC-9/MD-80/717 aircraft are fueled the same way -

Wings evenly until full
then Center
then any AUX tanks in order (i.e. AUX 1 before AUX 2)

Basic theory of aircraft fuel systems - each engine has a main fuel tank associated to it. Thus if it has 2 engines, there will be 2 main tanks. Any other tanks will be (technically) auxiliary tanks, including the "Center" tank (and is even placarded as such on some aircraft just for good measure). The Main tanks are always filled even with each other and before filling the auxiliary tanks, however they may not be filled before reserve tanks (as typically you fill the reserve tanks no matter what), depending on the aircraft.

[flugkapitan]

Thanks for the replies!

I am aware of how it works in the real world, but just wanted to check since sometimes things in the FS world are slightly different than in the real world

Cheers,
Scott
KJMS (or thereabouts)

[jonm]

I haven't had any problems with the center tank empty on the series 30.

By the way, Christrott is correct. I was talking to my cousin who used to be an FO on the DC-9 at Eastern years ago, and he confirmed how the fuel was loaded.

[aerofoto - HJG Admin]

"YES" .... Chris is correct !

Incidentally .... those fuel loadings recommended within my DC9 flying guides only represent a quick/convenient means (which I used during testing) by which to reduce weight as near as possible to each aircraft types certified MGTOW .... without sacrificing payload.

As mentioned earlier in this thread .... I never had any fuel loading/distribution information to refer to at the time of my testing, so, my procedures (per those flying guides), despite the fact they work fine, don't reflect how fuel should be be loaded in realworld operations.

Mark C
AKL/NZ

[acourt]

Chris has it correct. Load the wing tanks, then the center, then any aux tanks. Here's a few additions (based on the 717, but mostly accurate for the Nine)...

1) During preflight, only turn on fuel pumps for tanks with fuel in them. Most of the time, you'll run with the center tank empty and its pumps off. (Interestingly enough, the pumps for the center fuel tank are actually located in the right wing.)

2) If you burn fuel from the center tank, the airplane will present a caution five minutes after detecting a low fuel level in the center tank that tells you to turn off the center pumps. In the DC-9, there is no such caution, but five minutes after showing zero center tank quantity is probably a good time to switch off the pumps.

3) Running the center tank pumps with an empty center tank results in an noticeable vibration in the cabin, similar to having the landing lights extended. Why? I don't know. But it is noticeable to everyone in the airplane.

4) The main fuel pumps are AC powered (external power, APU, or engine-driven generator). With only battery power, you'll have to use the DC Start Pump to start the APU. If you're on External Power or have an engine-driven generator running, you'll only need the main pumps. In several thousand hours of operation, I've only used the Start Pump three times that I can remember.

5) Since the fuel pumps are AC powered, they are not available on Emergency Power (batteries only). If you end up on Emergency Power in-flight, the minimum fuel flow is 1700 pph per engine above 17,000 feet (717 only). I don't know if the Nine has such a limitation. But be prepared for an engine failure if you lose normal electrical power at high altitude. You might not want to descend with near idle power.

That's about all I can think of right now. It's kind of quick, but I have to run.

Al