Real range vs. advertised.
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Real range vs. advertised.
In your experience, what percentage of the advertised maximum range for business jets would you say works for max payload at max fuel, "real world" mission profiles?
90%
80%
Less...?
In other words, if one wants to do say, 2,500NM sectors, which advertised class should one be looking for?
Thanks.
SK
90%
80%
Less...?
In other words, if one wants to do say, 2,500NM sectors, which advertised class should one be looking for?
Thanks.
SK
Max payload or max fuel? Many planes can't go both. What airports, as take-off performance can be a major stumbling block. Are the legs overwater? Is ETOPS an issue or regulatory reserves?
GF
GF
If I interpret the question correctly, the OP is asking what percentage of a generic bizjet's published maximum range is practical (not theoretical best case) in the real world. And of course the answer to that question depends upon many factors including those cited above. Invariably, how far an airplane can be flown and still have adequate fuel on board to meet any reasonable contingency is dependent upon weight, altitude, temperature, runway available/required, necessary climb gradient (both AEO and OEI) and winds/temps aloft. And that's just to get out of the terminal area! Enroute and destination wx and contingency planning may further limit how much practical range will be available.
As a "for instance" a simple little jet like the Lear 60 has an "advertised" (from the AFM) max still air range of 2399 Nm. And it can do it too. In perfect conditions with no contingency fuel other than regulatory VFR reserve fuel at destination and no departure or enroute limitations being imposed by airport, diversionary or terrain considerations. If you fly it exactly as called for in the performance section of the AFM, it will fly that far on very near to the scheduled quantity of fuel. Really.
Of course in the real world, we can rarely fly the profiles exactly as called for in the AFM and the actual conditions often don't allow one to match the conditions assumed in the "max range" performance profile. Nor can one rely upon ATC granting unrestricted climbs or tolerating the low speed idle descents assumed in the max range profile. Hence, any responsible flight planning will normally allow for an actual range that is well less than the AFM "maximum range". How much less just depends upon how the variables interact.
Speaking generally, I'd surmise that longer range Biz aircraft like the G-6 and Global series can typically fly a greater percentage of their "max range" than shorter range jets like the Lear or other medium/small bizjets. The longer they are in cruise, the more closely they are likely to be able to match the profile generally. So off the top of my head, best guess ranges from 85-95% of AFM max range with ULR aircraft realizing the higher percentage. In the Lear 60 we would rarely if ever plan for more than 2,200 nm of the 2399 nm (91.7%) of the equivalent still air distance it is capable of in perfect assumed conditions.
That's a similar percentage to what I've flown in the other two jets I've operated. And I've only done 4 N. Atlantic crossings, all in the Lear from Canada to Ireland and back. So I am more than happy to learn from any ULR bizjet pilots with greater long-range flying experience.
As a "for instance" a simple little jet like the Lear 60 has an "advertised" (from the AFM) max still air range of 2399 Nm. And it can do it too. In perfect conditions with no contingency fuel other than regulatory VFR reserve fuel at destination and no departure or enroute limitations being imposed by airport, diversionary or terrain considerations. If you fly it exactly as called for in the performance section of the AFM, it will fly that far on very near to the scheduled quantity of fuel. Really.
Of course in the real world, we can rarely fly the profiles exactly as called for in the AFM and the actual conditions often don't allow one to match the conditions assumed in the "max range" performance profile. Nor can one rely upon ATC granting unrestricted climbs or tolerating the low speed idle descents assumed in the max range profile. Hence, any responsible flight planning will normally allow for an actual range that is well less than the AFM "maximum range". How much less just depends upon how the variables interact.
Speaking generally, I'd surmise that longer range Biz aircraft like the G-6 and Global series can typically fly a greater percentage of their "max range" than shorter range jets like the Lear or other medium/small bizjets. The longer they are in cruise, the more closely they are likely to be able to match the profile generally. So off the top of my head, best guess ranges from 85-95% of AFM max range with ULR aircraft realizing the higher percentage. In the Lear 60 we would rarely if ever plan for more than 2,200 nm of the 2399 nm (91.7%) of the equivalent still air distance it is capable of in perfect assumed conditions.
That's a similar percentage to what I've flown in the other two jets I've operated. And I've only done 4 N. Atlantic crossings, all in the Lear from Canada to Ireland and back. So I am more than happy to learn from any ULR bizjet pilots with greater long-range flying experience.
Depends also on the pilot's attitude to fuel-starvation risk.
Friends who are ex-airline pilots seem much more prepared to plan a flight arriving with minimal legal reserves as that is what they were often expected to do on the airlines. Friends who have come through the GA ranks seem more cautious.
Friends who are ex-airline pilots seem much more prepared to plan a flight arriving with minimal legal reserves as that is what they were often expected to do on the airlines. Friends who have come through the GA ranks seem more cautious.
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Friends who have come through the GA ranks seem more cautious.
OTOH we do operate a lot in EEUR and AFR, places where a lot of WX or unpredictable things happen.
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My record was 98,73% of the advertized range (medium jet brochure).
I remember having landed with minimum (legal) fuel. Not something I want to see on a daily basis.
Ask any passenger if they would like the idea of a minimum fuel policy written in their ticket terms...
I consider that "safety first" implies some margin with fuel and that only occasionnaly, if weather, ATC, airport, pax briefed and agreed beforehand, and all parameters are suitable, then why not fly to the limit
.
My record on ULR was 97% of the advertized range but we landed with minimum + 30 min extra fuel.
I remember having landed with minimum (legal) fuel. Not something I want to see on a daily basis.
Ask any passenger if they would like the idea of a minimum fuel policy written in their ticket terms...
I consider that "safety first" implies some margin with fuel and that only occasionnaly, if weather, ATC, airport, pax briefed and agreed beforehand, and all parameters are suitable, then why not fly to the limit
. My record on ULR was 97% of the advertized range but we landed with minimum + 30 min extra fuel.
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From the replies, I am get the feeling that if one applies a 85% factor to the advertised maximum range with max allowable payload for max fuel, one can make an initial browse-appraisal of advertised commercial proposals.
Obviously, mission-specific requirements must be directly addressed to the manufacturers for binding proposals.
Stiil, the 85% factor, seems to be a good benchmark to weed-out "yes, we can" overoptimistic claims.
Thank you all for your inputs.
Obviously, mission-specific requirements must be directly addressed to the manufacturers for binding proposals.
Stiil, the 85% factor, seems to be a good benchmark to weed-out "yes, we can" overoptimistic claims.
Thank you all for your inputs.
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I my experience CL 604 advertised a 4K nm range...I could never get that but got 3800 a couple of times. Global 5000 advertises 5000 nm range...Gulfstream salesman commented to me...."Global 5000? You must mean Global 4800". He was right.
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In an honest world, the advertised range would be a useful guide on range only in terms of aircraft to aircraft comparison, not in actual performance capability in the real world.
Whilst the stated 'profile' for such comparisons is typically ISA (Sea level 15C std Atmos/pres), no wind with an infinitely long perfectly flat runway, even then we don't know the fuel density being used for the calculation...and that makes a difference. Pax also should have a standard weight as should the additional items beyond the basic crew weights, such as galley stock etc.
Range circles are another useful comparative tool, but are typically based on great circle flying, when in reality airways and ATC dictate actual flight path.
If you want to understand specific routes, then discuss with a manufacturers rep, or on forums with pilots who can run the numbers through real FMS/flight planning procedure. There are too many variables to give a single answer. The issue with running just one flight plan is that it will either have no wind, or a specific days weather. Whilst a better understanding can be gained by using the statistical models such as from Boeing. So a Boeing 85% All year wind model, would mean that 85% the winds would be expected to be more favourable than in the planning model....you can also ask for specific Season only or more stringent winds to be sure to always achieve the mission. However, such models again typically run on great circle or just one specific routing/distance and ATC changes, holding /vectors, different FL allocations all screw up these calcs, as would the availability of different specific density fuel or non ISA conditions.
As a very much rule of thumb......80% of advertised ranges are actually flyable in almost all conditions at advertised loads, drop 50-75nm per pax additonal. Outside this range, get advice and study the books/performance/winds etc, as you're going to be too close to call. However, if any really critical decisions are going to be based outside the 'pub' then don't use advertised ranges for any real world performance studies as that isn't really why they are there....they're comparative to the competition only.
Whilst the stated 'profile' for such comparisons is typically ISA (Sea level 15C std Atmos/pres), no wind with an infinitely long perfectly flat runway, even then we don't know the fuel density being used for the calculation...and that makes a difference. Pax also should have a standard weight as should the additional items beyond the basic crew weights, such as galley stock etc.
Range circles are another useful comparative tool, but are typically based on great circle flying, when in reality airways and ATC dictate actual flight path.
If you want to understand specific routes, then discuss with a manufacturers rep, or on forums with pilots who can run the numbers through real FMS/flight planning procedure. There are too many variables to give a single answer. The issue with running just one flight plan is that it will either have no wind, or a specific days weather. Whilst a better understanding can be gained by using the statistical models such as from Boeing. So a Boeing 85% All year wind model, would mean that 85% the winds would be expected to be more favourable than in the planning model....you can also ask for specific Season only or more stringent winds to be sure to always achieve the mission. However, such models again typically run on great circle or just one specific routing/distance and ATC changes, holding /vectors, different FL allocations all screw up these calcs, as would the availability of different specific density fuel or non ISA conditions.
As a very much rule of thumb......80% of advertised ranges are actually flyable in almost all conditions at advertised loads, drop 50-75nm per pax additonal. Outside this range, get advice and study the books/performance/winds etc, as you're going to be too close to call. However, if any really critical decisions are going to be based outside the 'pub' then don't use advertised ranges for any real world performance studies as that isn't really why they are there....they're comparative to the competition only.
