MD-11 freighter - ballast question

[HighBypass 2,339]

A question for anyone familiar with real-world operations of the lovely tri-holer freighter.

If an MD-11 had to be flown to an MRO (maintenance, repair, overhaul) facility, then would there be a specific pallet of ballast added so that she could fly empty? Would this be subject to a whole load of variables such as range and fuel quantity required?

I would think that if possible, some cargo of some sort (for the destination) would be loaded to maybe generate some revenue on the flight.

Thanks.

[Pat Mussotte 92]

I don't know for the MD11 but when we flew the DC10 to the maintenance base for overhaul, we had to ballast it, particularly the ER. Most of the time we had some parts on pallets, mainly tyres and a few boxes. If it is a flight to the maintenance base you can't transport cargo for generating revenue because this is not a commercial flight.

Cheers

Pat

[Dick 47]

A freighter MD-11 would indeed need either ballast fuel in the center tank or other "weight" in the front part of the aircraft when flying empty. ( be it to MRO or even ferry or positioning). We would ( IRL) not even park an MD-11F empty in between flight.  Wind and sloping ramp ( tail down) could bring the aircraft in an unsafe situation. The tipover alarm ( optional on freighters) could be activated in cases like this. We had special pallets with 2 tons of concrete poured on top that would be loaded on the first Belly1  position or one of the maindeck A positions .  Of course also other "weight" could be used.

This would not be subject to variables as the aircraft needs to be in safe condition also in ZFW condition therefore range/fuel do not play a role in this. When you land on your  alternate after a possible 30 mins of holding you are nearing zfw condition anyway.

Pax aircraft would normally be able to fly empty as there are many seats/galleys etc( =weight) in front of the wing compared to aft of the wing. Therefore pax md-11 were less critical.

 

b rdsg / Dick

Edited September 8, 2019 by dick

[HighBypass 2,339]

Thank you for the replies, gents!

I "need" to take my Western Global MD-11 to Shreveport Regional for a C-check and as per advice will be loading some palletised concrete for the trip.

(Of course I don't "need" to do anything with a virtual plane, but you get the idea! 😂)

[ABurek 3]

FDX would put 20.0 in the upper aux.  also make sure you put it in the MCDU under ballast fuel so the FSC doesn’t take it out.  

 

Ballast pallets aren’t typically used to ferry airplanes for maintenance. 

Edited September 8, 2019 by ABurek

[HighBypass 2,339]

Hi ABurek,

Sorry - should have specified that I don't have the PMDG MD, but the Sky Sim one, so no fancy option for recording ballast fuel AFAIK.

I'm not sure I understand: Fedex would just use fuel in the upper aux tank (20 tons?) and not use anything to make sure the ZFW was within limits?

Would large amounts of fuel be left in the tanks whilst undergoing intensive checks and maintenance?

Would ballast be loaded prior to the plane being de-fuelled?

[Dick 47]

Ballast fuel is unusable fuel and is therefore included in the ZFW.  It becomes "dead weight" and nothing more. In real life indeed in many situations ballast fuel would be used for ferry flight. Disadvantage is that your aircraft is 20 tons heavier and therefore consumes more tripfuel. If the ferry flight is short that would not be such a problem however.  SkySim may not have this option...

Problem with a pallet with concrete (when used on a ferry flight ) is how to get it back on the originating station if e.g. the return is not returning to the originating station. Jerrycans with water or sandbags could also be used. Mind you that sand is in some countries is seen as biological material and therefore can only be disposed of under certain conditions. ( the sand may contain "life" as in seeds/plants or life animals)

Note that the MD-11 is not certified to use a tailjack as support on the ground . The aft fuselage structure may be damaged ( bend)

Alternative ways to make sure your MD-11 does not tip while on the ground could be to use a cart with concrete attached to the nose gear or some airport stand have fittings in the tarmac where you can tie you nose wheel down with straps to the ground.

All options to make sure your center of gravity is within required ranges or tip prevention do have their specific advantages and disadvantages..

There could indeed be a need to defuel the aircraft depending on type of maintenance.

[HighBypass 2,339]

Thank you for your collective insights, gents!

I shall have to have a play around loading and unloading "ballast" and/or fuel to see exactly when the cofg out of limit warning is displayed (we're talking Sky Sim here), and when I can get it to extinguish. I think I messed around with this kind of thing a while ago before I understood the subject better!

I fear that the automatic fuel usage is simplified - whenever I've used a max fuel load, she uses the tail fuel combined with the aux tank first. She doesn't appear to transfer fuel TO the tail under any circumstances, nor leave any fuel in the aux or tail tanks apart from a couple of hundred kgs (presumably un-pumpable/ unusable). I don't think that switching the system to manual would help, apart from actually preventing the use of tail or aux fuel..