RJMAZ
Topic Author
Posts: 1625
Joined: Sat Jul 09, 2016 2:54 am

Boeing 777 ACAP anomaly

Mon Sep 16, 2019 12:06 am

I have noticed the 777-200LR and 777-300ER payload range curves are presented differently to all of the other Boeing ACAP documents. It could also be a potential scaling error.

http://members.iinet.net.au/~1300subbox/777LR.jpg

The Y axis has OEW plus payload. The 777 does not start at zero payload like all of the other ACAP documents. The 777-200LR Y axis starts at just over 160t takeoff weight which means it already has payload.

Likewise with the 777-300ER the Y axis starts at 190t.

This curve presented below on a different site has 30t of payload at 9500nm.

Image

The Y axis scaling is potentially wrong on the ACAP and it could start at 145t and 167t. If a member has some has some airline data they could confirm a few data points that would be great.
 
User avatar
zeke
Posts: 13968
Joined: Thu Dec 14, 2006 1:42 pm

Re: Boeing 777 ACAP anomaly

Mon Sep 16, 2019 4:18 am

RJMAZ wrote:
The Y axis has OEW plus payload.


That is normal for Boeing charts
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
RJMAZ
Topic Author
Posts: 1625
Joined: Sat Jul 09, 2016 2:54 am

Re: Boeing 777 ACAP anomaly

Mon Sep 16, 2019 4:53 am

zeke wrote:
RJMAZ wrote:
The Y axis has OEW plus payload.


That is normal for Boeing charts

Yes, but the 787, 767 and 737 charts the Y axis starts at the OEW with no payload. The payload is added as you go up the Y axis.

The 777 charts the Y axis starts at a weight higher than the OEW.

A few websites that have combined multiple payload range charts onto one graph have misread the 777 chart as a result.

That second chart shows the 777-200LR with a max payload of 51t, yet it is 64t. That 13t difference is because the creator misread the chart as the Y axis starts about 13t heavier than OEW.
 
User avatar
zeke
Posts: 13968
Joined: Thu Dec 14, 2006 1:42 pm

Re: Boeing 777 ACAP anomaly

Mon Sep 16, 2019 5:38 am

RJMAZ wrote:
That second chart shows the 777-200LR with a max payload of 51t, yet it is 64t. That 13t difference is because the creator misread the chart as the Y axis starts about 13t heavier than OEW.


The chart was from a 777 presentation I remember seeing on Boeing startup.

The payload figure for the 77L is correct for the conditions they specified.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
flipdewaf
Posts: 2889
Joined: Thu Jul 20, 2006 6:28 am

Re: Boeing 777 ACAP anomaly

Mon Sep 16, 2019 5:41 am

Does the 777 have any minimum weight criteria for performance? Could be why it doesn’t start that low?

Fred


Sent from my iPhone using Tapatalk
Image
 
RJMAZ
Topic Author
Posts: 1625
Joined: Sat Jul 09, 2016 2:54 am

Re: Boeing 777 ACAP anomaly

Mon Sep 16, 2019 6:43 am

flipdewaf wrote:
Does the 777 have any minimum weight criteria for performance? Could be why it doesn’t start that low?

Fred

I originally thought there was a minimum fuel amount that must be kept in the wings at higher payloads to reduce wing root bending moment. But it says zero fuel weight.

If we take the 777-200LR chart with three ACT's if someone assumed the Y axis starts at zero payload and worked from the bottom up then the aircraft would carry 25t to 9500nm. That is the point of the second kink.

However if we assume the max payload is 63,957kg as listed in the ACAP and then work from the max zero fuel weight or top down then the aircraft would carry 39t to 9500nm.

Now most reports and analysis points to the 25t of payload at 9500nm being the correct answer. This would mean the labels for the Y axis are wrong. Each horizontal line in the 777 charts should not represent 10,000lb weight increments but about 12,500lb.
 
WIederling
Posts: 8888
Joined: Sun Sep 13, 2015 2:15 pm

Re: Boeing 777 ACAP anomaly

Mon Sep 16, 2019 7:41 am

ZFW + FUEL is the determinant for range performance.

OEW and Payload are not separable from a ZFW + FUEL over Range diagram.
( what do ACT's weigh for the 777 ? 3 should present quite a bit of extra dead weight.)
Murphy is an optimist
 
User avatar
zeke
Posts: 13968
Joined: Thu Dec 14, 2006 1:42 pm

Re: Boeing 777 ACAP anomaly

Mon Sep 16, 2019 9:50 am

flipdewaf wrote:
Does the 777 have any minimum weight criteria for performance? Could be why it doesn’t start that low?


Fred

That curve is for the 77L with AUX tanks, the AUX tanks increase the OEW, and the additional fuel displaces normal revenue payload.


The OP obviously thinks they can have AUX tanks in the cargo hold and still take normal full revenue payload.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News
 
flipdewaf
Posts: 2889
Joined: Thu Jul 20, 2006 6:28 am

Re: Boeing 777 ACAP anomaly

Mon Sep 16, 2019 10:38 am

zeke wrote:
flipdewaf wrote:
Does the 777 have any minimum weight criteria for performance? Could be why it doesn’t start that low?


Fred

That curve is for the 77L with AUX tanks, the AUX tanks increase the OEW, and the additional fuel displaces normal revenue payload.

Yes, the additional Fuel displaces ~14t of payload but the OEW wouldn't see that effect hence why we see the simple shift in the second kink.

The OP obviously thinks they can have AUX tanks in the cargo hold and still take normal full revenue payload.[/quote]

I don't think that's what he's saying (Sexist of me to assume gender), I think the question revolves almost solely around if there is a technical reason why the payload range chart doesn't bottom out at 0 payload like other Boeing ones do. I don't think that part of the chart is particularly useful outside of ferrying anyway.

Fred
Image
 
RJMAZ
Topic Author
Posts: 1625
Joined: Sat Jul 09, 2016 2:54 am

Re: Boeing 777 ACAP anomaly

Mon Sep 16, 2019 11:18 am

flipdewaf wrote:
I think the question revolves almost solely around if there is a technical reason why the payload range chart doesn't bottom out at 0 payload like other Boeing ones do. I don't think that part of the chart is particularly useful outside of ferrying anyway.

Fred

A technical reason or if there is an error on the Y axis labels.

If the labels are correct surely the 777LR can not carry 39t of payload a distance of 9500nm? That is well beyond the project sunrise requirement. The 329t takeoff weight line crosses at about 28t of payload at 9500nm enough to do around 250 passengers on London-Sydney.

Interesting that the 777-200LR is similar empty weight as the A350-1000. So on the project sunrise route the 777-200LR would burn only 5% more fuel. The chart Y axis labels must be wrong.
 
flipdewaf
Posts: 2889
Joined: Thu Jul 20, 2006 6:28 am

Re: Boeing 777 ACAP anomaly

Mon Sep 16, 2019 12:10 pm

RJMAZ wrote:
flipdewaf wrote:
I think the question revolves almost solely around if there is a technical reason why the payload range chart doesn't bottom out at 0 payload like other Boeing ones do. I don't think that part of the chart is particularly useful outside of ferrying anyway.

Fred

A technical reason or if there is an error on the Y axis labels.

If the labels are correct surely the 777LR can not carry 39t of payload a distance of 9500nm? That is well beyond the project sunrise requirement. The 329t takeoff weight line crosses at about 28t of payload at 9500nm enough to do around 250 passengers on London-Sydney.

Interesting that the 777-200LR is similar empty weight as the A350-1000. So on the project sunrise route the 777-200LR would burn only 5% more fuel. The chart Y axis labels must be wrong.


I see what you mean, it does look as if the Y axis is wrong, I cant imagine that the 77L assumes to be 160t DOW with ~145t OWE.

Fred
Image
 
RJMAZ
Topic Author
Posts: 1625
Joined: Sat Jul 09, 2016 2:54 am

Re: Boeing 777 ACAP anomaly

Mon Sep 16, 2019 1:19 pm

flipdewaf wrote:
I see what you mean, it does look as if the Y axis is wrong, I cant imagine that the 77L assumes to be 160t DOW with ~145t OWE.

Fred

The 777-300ER chart also starts at 186t instead of 168t. So the graph assumes around 18t of payload carried.

I would assume the bottom of the Y axis should be the OEW of 145t and 168t for the 200LR and 300ER charts. As the max zero fuel weights are correct at the top of the graph then the spacing between horizontal lines should be aproximately 12,500lb instead of 10,000lb.

So we can multiply by 1.25. 25t of payload to 9500nm becomes 31.25t which seems spot on to me.

You may have used known payload range charts to help calibrate or tweak your software model. If you used the 777 charts you might want to have a look.

It would be great if someone working at an airline who operates 777's could check their flight planning software.
 
WIederling
Posts: 8888
Joined: Sun Sep 13, 2015 2:15 pm

Re: Boeing 777 ACAP anomaly

Mon Sep 16, 2019 3:41 pm

RJMAZ wrote:
Interesting that the 777-200LR is similar empty weight as the A350-1000. So on the project sunrise route the 777-200LR would burn only 5% more fuel. The chart Y axis labels must be wrong.


A3510 is said to take ~~22..25% less fuel than the 77W.
Do you really think that contracts to just 5% delta in relation to the 777-200LR ?

weight delta relative 77W is just 6% and you have 10m less fuselage drag
Murphy is an optimist
 
RJMAZ
Topic Author
Posts: 1625
Joined: Sat Jul 09, 2016 2:54 am

Re: Boeing 777 ACAP anomaly

Tue Sep 17, 2019 4:16 am

https://leehamnews.com/2015/07/24/bjorn ... all-about/

Leeham assumed a 155t OEW for the 777-200LR not the 145t in the ACAP. That covers most of that missing 13t.

It is hard to accurately compare payload range charts if they are not consistent.
 
flipdewaf
Posts: 2889
Joined: Thu Jul 20, 2006 6:28 am

Re: Boeing 777 ACAP anomaly

Tue Sep 17, 2019 7:02 am

RJMAZ wrote:
https://leehamnews.com/2015/07/24/bjorns-corner-weight-or-fuel-limited-what-is-this-all-about/

Leeham assumed a 155t OEW for the 777-200LR not the 145t in the ACAP. That covers most of that missing 13t.

It is hard to accurately compare payload range charts if they are not consistent.

I do find it odd that in the 777 wiki page ( I know, I know) the 77F is so close to the 77L weight, I would have expected the 77F to be several tons difference.

Fred


Sent from my iPhone using Tapatalk
Image
 
WIederling
Posts: 8888
Joined: Sun Sep 13, 2015 2:15 pm

Re: Boeing 777 ACAP anomaly

Tue Sep 17, 2019 11:57 am

flipdewaf wrote:
... I would have expected the 77F to be several tons difference.


For a comparison the A330-200F is about 8..10% lighter in OEW than the A332 PAX version.

But doesn't the 777F get strongly reinforced upper hold floorbeams?
( Seem to remember some info that reworking the 777-200 airframe as a freighter
is cost prohibive due to the extra light floors.)
Murphy is an optimist

Who is online

Users browsing this forum: ALTF4 and 14 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos