767 Fuel Jettison Load Shed

[NSEU]

According to one informative 767 website....

"Electrical load shedding will occur during fuel jettison :

- Equipment cooling fans (equipment cooling system reverts to OVRD mode)
- Bulk cargo vent fan
- Selected lights (landing lights, wing illumination, logo lights, galley lights)
- Window heat 3L & 3R
- PAX entertainment equipment
- Water line heaters"

Discussing this with fellow engineers and pilots from various airlines, no-one has been able to confirm that Water Line Heaters and external lights are affected by fuel jettison.

Would someone be able to independently confirm this?

Our schematic diagrams show the landing lights and water heaters may share primary circuit breakers, but relays exclude them from being affected by Fuel Jettison Load Shed.

Thanks in advance.

Rgds.
NSEU.

Boeing wiring schematic ref: 24-51-08... and many others.

[Twitter n Bisted]

Hey
I am not sure where you get your info from.
You only get electrical load shedding on the 767 during fuel jettison when you only have 1 "one" electrcal sourse. eg when testing the system on the ground external power or APU supply.

For the life of me I cannot understand why you would worry about inline water heaters when you are in a situation requiring fuel jettison.
Landing lights some but not all are powered from the essentials bus...not load shed.
Hope this helps

[NSEU]

Hey, I am not sure where you get your info from.

Hey, yourself.

I'm told the info is available at:

http://www.smartcockpit.com/

You only get electrical load shedding on the 767 during fuel jettison when you only have 1 "one" electrcal sourse. eg when testing the system on the ground external power or APU supply.

Our company B767-300ER wiring and wiring schematic manuals indicate that the single source requirement is not required. Only one aircraft in our CF6 fleet had the single source requirement (our oldest one) and I believe the wiring has since been modified to remove this requirement on this particular aircraft. A maintenance engineer from another airline, KLM, has told me that variations exist in his airline, too.

Information on the smartcockpit website suggest that Austrian Airlines loadshed their lights.

Rgds.
NSEU

[Twitter n Bisted]

Hey again. (didnt mean to offend)

I have worked on 767s with CF6 PMC/FADEC Rolls/R and PW. All only load shed the systems you list when the aircraft is in single electrical supply config...There is no reason to shed so many systems to power 2 extra CAT (Center Aux Tank)boost pumps when you have 2 servicable 90 KVA IDGs powering the aircraft.
Maybe this is a software conflict I will have to check next time I fit another operators BPCU

Perhaps the the wiring/config you speak of is in the latest of the 767
You could try the web site www.myboeingfleet.com
I could only retrieve info on my companies A/C

[NSEU]

Hey again. (didnt mean to offend)

OK, thanks for the clarification, TnB.

Like you, I don't understand why you would need loadshed with both engine gens running (unless there is a reliability issue... extra relays removed for simplicity).

Unfortunately, I don't have access to MyBoeingFleet (too low down in the pecking order... and since it is only out of interest that I asked the original question, I don't think I'll bother our Maint Centre with this kind of thing until I am asked to do carry out a check on this system).

Thanks for your input.

Best rgds.
NSEU.

[Twitter n Bisted]

Hey

You got me thinking so chased up the info from our fleet to confirm latest Mod status.

OK it goes like this....Early 767...did not have any load shedding.

Then next mod was if both BTBs closed (one power source) aircraft load shed but NO load shed if 2 power supplies (normal config)

Latest Mod ( I do stand corrected)
But now with incorp. of SB 28-0025 Rev 1,
Load shedding happens when Jettison selected whether with 1 or 2 power supplies
Items IFE and PES are shed plus #3 L/ R cockpit window
Load shedding is there to prevent possible source overloads?
Equipment cooling fans are not load shed.

Hope this helps and ends the discussion