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When specifying aircraft range?

Posted: Sat Apr 03, 2021 9:02 am
by mafaky
When the airplane manufacturer species the range as say 5.000 km. what factors are involved in this 5.000 km. figure? Particularly, all other factors set aside, does this mean: the plane takes off with its max. fuel payload and when it lands after 5.000 km. does this mean it has exhausted all its fuel payload or is still there some reserve fuel left in its tanks?

Re: When specifying aircraft range?

Posted: Sat Apr 03, 2021 12:47 pm
by Starlionblue
All those public numbers should be treated with a big scoop of salt. They're marketing figures, and will be massaged to be favourable for the manufacturer's product.

Operators need aircraft for specific missions and will negotiate specific performance guarantees.

Re: When specifying aircraft range?

Posted: Sat Apr 03, 2021 1:29 pm
by GalaxyFlyer
True that, brochure ranges, I called them. Business jets post based on a NBAA profile—take-off, cruise, descent, one approach at destination, 5 minute hold for clearance to alternate 100nm away, fly there, land with 45 minutes at normal cruise fuel flow at 10,000’. Then come the details, “normal cruise fuel flow” at 10,000’is LRC, cruise Mach can be somewhat hidden, airways and climb profiles don’t account for ATC, it’s great circle between all three points.

Re: When specifying aircraft range?

Posted: Sat Apr 03, 2021 9:19 pm
by ElroyJetson
Starlionblue wrote:
All those public numbers should be treated with a big scoop of salt. They're marketing figures, and will be massaged to be favourable for the manufacturer's product.

Operators need aircraft for specific missions and will negotiate specific performance guarantees.


As I recall SQ had performance guarantees the MD-11 could fly SIN-LHR in winter with full pax and bags. When it could not it hurt MD-11 sales tremendously.

Without getting too specific, does the aircraft you fly generally adhere to the marketing numbers (I.e. the bouchure range at various payloads)?

Re: When specifying aircraft range?

Posted: Sun Apr 04, 2021 1:37 am
by Starlionblue
ElroyJetson wrote:
Starlionblue wrote:
All those public numbers should be treated with a big scoop of salt. They're marketing figures, and will be massaged to be favourable for the manufacturer's product.

Operators need aircraft for specific missions and will negotiate specific performance guarantees.


As I recall SQ had performance guarantees the MD-11 could fly SIN-LHR in winter with full pax and bags. When it could not it hurt MD-11 sales tremendously.

Without getting too specific, does the aircraft you fly generally adhere to the marketing numbers (I.e. the bouchure range at various payloads)?


Now I have to look at the marketing numbers. :D

It's a bit hard to tell, tbh, because the airport planning document always seems to be based on a "standard three-class layout" or the like, and this layout is anything but "standard". Most operator layouts will be heavier, at least for widebodies. Things like business class seats and galleys have a big impact.

That being said, the graphs in the airport planning doc are reasonably close to the truth. Just not nearly accurate enough for real-world planning.

Re: When specifying aircraft range?

Posted: Sun Apr 04, 2021 2:56 am
by 26point2
When my boss was looking for a new plane and was considering the Bombardier Global 5000 (advertised as having 5000nm range) I mentioned this to the Gulfstream salesman. He quipped, “Global 5000? You mean the Global 4700”. Funny. We ended up buying a Global 5000....with it’s 4700nm range.

Re: When specifying aircraft range?

Posted: Sun Apr 04, 2021 6:20 am
by JayinKitsap
Need to look at the Payload-Range curves available in the Airport Planning Guides. The brochure ranges are cherry picked off of those curves. For an A320 it probably picks 160 passengers, no bags, and the maximum assuming the closest alternate airports etc.

Re: When specifying aircraft range?

Posted: Sun Apr 04, 2021 1:35 pm
by XT6Wagon
Brochure range is "passenger only" range. So its using a manufacture set seating arrangement with assumed weight for that interior configuration. Then the industry standards for passenger and their luggage is added to the empty weight. This means some planes really suffer from range drop with added cargo because they are weight limited on fuel. So a ton of cargo at MTOW pulls a ton of fuel out. Others are lesser affected because they can add cargo without removing fuel.

Oh and as engines get even more efficient, the more paper range is hit more in the real world because each ton of fuel gets the plane farther. So the really high paper ranges we are seeing today is less realistic than the ranges of 50 years ago, because pulling a ton of fuel off those older planes did very little when viewed in miles.

Re: When specifying aircraft range?

Posted: Sun Apr 04, 2021 2:29 pm
by GalaxyFlyer
26point2 wrote:
When my boss was looking for a new plane and was considering the Bombardier Global 5000 (advertised as having 5000nm range) I mentioned this to the Gulfstream salesman. He quipped, “Global 5000? You mean the Global 4700”. Funny. We ended up buying a Global 5000....with it’s 4700nm range.


And, if like lots of bizjets flew NYC to PBI or some such leg. OTOH, no matter how much range the jet has, the Boss wants to go 100nm farther. Finally, lots of bizjet drivers can be incredibly conservative on fuel, landing a G5000 with 5000# had some guys sweating. 1800# is about 45 minutes for FAA reserves, a bit less than that for EU-OPS at 30 minutes at 1,500’. The NBAA reserves for the G5000 are about 3200#.

Re: When specifying aircraft range?

Posted: Mon Apr 05, 2021 2:01 pm
by LCDFlight
On this forum, we have found the maximum practical range for many airliner models. This needs to be year round, bidirectional, full passenger load plus their bags. Usually, plus a little cargo.

It's called the "longest scheduled route" of each aircraft type. This, basically, is what the OEM are attempting to sell us with their "real world range." For the A380, SYD-DFW has been a good example (7500nm). .

Re: When specifying aircraft range?

Posted: Mon Apr 05, 2021 4:30 pm
by mxaxai
Range is not a single fixed value. All aircraft have a payload-range-curve that is published in the airport planning document. Here's an example for the A340-300:
Image
https://www.airbus.com/content/dam/corp ... 00-300.pdf

Note how different engine variants and different takeoff weight ratings can affect range. Also note that long haul aircraft rarely depart with their maximum possible payload. The A340-300 here has a (brochure) range of ~5,500 nmi with its maximum payload but they used to serve some longer routes like SIN-LHR (5,878 nmi), MAD-SCL (5,778 nmi) or YYZ-HKG (6,787 nmi).

These documents use some standard flight profile and configuration, so they're easily comparable between different aircraft of the same manufacturer, and often even between manufacturers. A similar standardized approach is used by engineers for the preliminary design, albeit with some margins to make it more realistic and to account for uncertainties.

Marketing brochures then take these graphs, search for the most favorable conditions and plot colorful range circles on a fancy map. These are generally not realistic for the reasons stated above.

Re: When specifying aircraft range?

Posted: Mon Apr 05, 2021 7:54 pm
by DocLightning
Starlionblue wrote:
It's a bit hard to tell, tbh, because the airport planning document always seems to be based on a "standard three-class layout" or the like, and this layout is anything but "standard". Most operator layouts will be heavier, at least for widebodies. Things like business class seats and galleys have a big impact.


Are they? I always feel like the ACAP layouts are higher density (for widebodies) than I actually see airlines using. I know the seats are not weightless, but nor are passengers.

Re: When specifying aircraft range?

Posted: Mon Apr 05, 2021 8:28 pm
by GalaxyFlyer
The ONLY range question that is at issue is can the plane under consideration do the required mission. The brochures and ACAP are nice charts but it doesn’t mean much.

Re: When specifying aircraft range?

Posted: Tue Apr 06, 2021 1:02 am
by Starlionblue
DocLightning wrote:
Starlionblue wrote:
It's a bit hard to tell, tbh, because the airport planning document always seems to be based on a "standard three-class layout" or the like, and this layout is anything but "standard". Most operator layouts will be heavier, at least for widebodies. Things like business class seats and galleys have a big impact.


Are they? I always feel like the ACAP layouts are higher density (for widebodies) than I actually see airlines using. I know the seats are not weightless, but nor are passengers.


That's a good point. I suppose someone more knowledgeable needs to weigh in. ;)

Re: When specifying aircraft range?

Posted: Tue Apr 06, 2021 11:06 am
by VMCA787
The ACAP is nothing but a guide. The pax loads are generally more than what "real world" operators have but the seats are substantially heavier than what the ACAP assumptions make. The net result is the DOW of the aircraft is heavier than the ACAP assumptions. On a wide body, such as the 744 or 748, the weight increase is something in the vicinity of 10-15 tonnes. Remember it's not just the seats but the galleys are generally heavier, the IFE is heavier than what is in the ACAP and of course, the seat is heavier too.

Re: When specifying aircraft range?

Posted: Tue Apr 06, 2021 12:43 pm
by CARST
Starlionblue wrote:
DocLightning wrote:
Starlionblue wrote:
It's a bit hard to tell, tbh, because the airport planning document always seems to be based on a "standard three-class layout" or the like, and this layout is anything but "standard". Most operator layouts will be heavier, at least for widebodies. Things like business class seats and galleys have a big impact.


Are they? I always feel like the ACAP layouts are higher density (for widebodies) than I actually see airlines using. I know the seats are not weightless, but nor are passengers.


That's a good point. I suppose someone more knowledgeable needs to weigh in. ;)


The people who are really into aircraft interiors usually mention that the airlines these days use very luxurious Business and First Class seats, which are way heavier, then the ones the manufacturers used for a long time in their planning documents. Heck, like 10 years ago, like every reputable airline was changing to the second generation of lie-flat seats in Business (usually from angled lie-flat to fully lie-flat) and Boeing and Airbus still often had old-school recliner seats in their planning documents which obviously were way less heavy.

Example from the 787 mockup from 2007/2008 with "shell type" recliner seats for business class (and no even more heavier first class):

Image

But I would assume that the planning documents today are way closer to the real world weight, because if you look into them, the manufacturers have a adopted a bit and seating is usually less dense and also they now use larger lie-flat-seats in their premium class layouts. So perhaps (a bit typical for a.net) we keep clinging on to something that is not true anymore (but was true in the past); read: planning documents were quite far off with the interior weights in the past, but are closer to reality today, but we keep believing they are not, due to our experience from the past.