Packs off fuel saving
 

do we save fuel during a packs off takeoff?
What if its a flex takeoff with packs off?

Thank you.

A bleed demand requires more fuel.
EGT will be higher too, causing more engine wear.

So that's a double saving.

MD83FO
Yes it saves fuel. RTOW charts give you credit for packs off in terms off weight or flex temperature. So for a given OAT you get higher MTOW or for a given ETOW you get higher flex.

Some airlines allow flex AND packs OFF ,some dont.
Different philosophy I guess.
A packs OFF t/o does require the APU to be operating until the packs are returned to their required position for the flight which does increase the fuel burn along with APU maintenance....i guess it all depends on your taxi time:E
Unpressurized t/o is also a possibility.

Not true. No requirement to have the APU running in order to take off with packs off.

Maybe you're thinking of running the packs from the APU to increase Go around gradient?

Surely the only reason you would do a packs off takeoff is for performance considerations? Therefore if you need the performance boost you get for packs off, surely it would be bloody daft to then try to assume (or flex in Bus-speak).

The APU, at least on brand B, is required to be running to provide bleed air for air conditioning and pressurisation.

We do PACKS OFF + FLEX, no need of APU running.

I have never taken off with the packs on on an Airbus.
Fuel saving's the reason.

Boeing has a slightly different procedure, the APU will be on during an no-engine bleed departure since I taking off unpressurised is a bit more problematic on the 737 (pax comfort during rotation due to the open outflow valve) if I remember correctly.

I do not understand your question about flex. What has flex got to do with it?

Savings are tiny, risks and added complexity considerable.
KISS. When it is not necessary for performance reasons, keep your packs/bleeds ON and do your fuel savings where it matters, enroute and during descend.

I don't know how you can justify that statement despegue. What considerable risks and complexity are you adding by turning the packs on after reducing to climb thrust?

There is no real risk on the Airbus. If you forget to turn the packs on the aircraft will gently remind you. On the Boeing it is a different matter.

Just for clarity/completeness on some "Boeings" it is permissible to perform both APU to Pack and/or pure Packs Off Take-Offs (and some do remind you shortly after takeoff if you have been a bit forgetful.:oh:).

Any additional task to accomplish in a high workload environment is adding to the risk of forgetting, omitting or incorrectly execution. With packs, this can be potentially very serious.
I am talking B737 here, not Airbus or better designed Boeing types.

As I said, fuel saving is a good practice, but we are becoming absolutely anal and overdoing it when a company cincreases workload, complexity and risk for a negligeable benefit.
Airmanship oversteps economics. Always.

despegue, the answer is already in your post: reduce the workload of other (non-essential) actions/procedures to be carried out during the phase of flight!

Redesign the SOP to fit the operation, not fit the operation around an SOP to be followed

Fuel saving? Flex takeoffs barely (if at all) save fuel, they reduce wear on the engines. Which is the significant cost saving here. The packs off allow a higher flex temperature.

Flex take off cost more fuel (less efficient climb to altitude). At least that's what the book says :ok:

Airmanship oversteps economics. Always.

The above is how it should be but not in the eyes of management.
A few years ago the thought of landing a 320 on a diversion with one ton of fuel
Would be frightening but a lot of modern F/O's think nothing of it as this is how they are taught.

I don't seem to meet those FO's in my outfit (big orange airline), most are very sensible with regard to fuel.

Indeed, I would argue that most FO's are the opposite, hesitant to take minimum fuel and highly concerned about diversion fuel.