Packs off fuel saving
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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.
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.
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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
Unpressurized t/o is also a possibility.
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
Unpressurized t/o is also a possibility.
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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
Maybe you're thinking of running the packs from the APU to increase Go around gradient?
Last edited by Blantoon; 17th Dec 2014 at 13:02.
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.
The APU, at least on brand B, is required to be running to provide bleed air for air conditioning and pressurisation.
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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?
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?
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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.
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.
Last edited by despegue; 17th Dec 2014 at 12:59. Reason: Spelling
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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?
Last edited by Blantoon; 17th Dec 2014 at 13:07. Reason: spelling
On the Boeing it is a different matter.
).
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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.
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.
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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
Redesign the SOP to fit the operation, not fit the operation around an SOP to be followed
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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.
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.
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.
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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.
Once you get about 10% below max rated thrust, incremental reduction of engine wear is miniscule. Engine speed and EGT which are the main drivers of wear -- are already significantly below max. In fact, on the 744 and 748 we too often take off with thrust set SIGNIFICANTLY below climb thrust! That is simply a beancounters' exercise to reduce engine lease payments, and has NO operational value.