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PolymerPlane
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Hot And High Performance B773ER Vs. A346

Sat May 31, 2008 7:16 am

I read from several discussions stating that A346 has hot and high advantage. I decided to punch in the numbers myself.

I take the extreme scenario, 8000 ft altitude at ISA+15 C, with 12,000 ft (3660 m) runway

Here are the basic numbers (assuming 365 pax and TOW from the take off perfomance graph)

____________A346_________B773ER
OEW____ 176,364 kg____ 167,829 kg
TOW____ 310,000 kg____ 290,000 kg
Payload__ 34,368 kg ____ 34,368 kg

Now, Boeing's ACAP includes payload range at different take off weights. at that given payload and 290 tonnes take off weight, B773ER have ~5300 NM range.

Airbus's ACAP however does not include such payload-range curve at different take off weights. I try to estimate this range reduction by using Boeing's curve. I think this is pretty reasonable assumption and should give the high side estimate since B773ER is more efficient than the 346.

From Boeing's graph, for every 11.3 tonnes drop in TOW, there is around 500 NM drop in the range.

Now, for a 310 tonnes TOW of A346, there is a 71,200 kg reduction from MTOW, thus having a 3150 NM range reduction. That means A346 have a range about 4600 NM

So in conclusion, B773ER does have lower takeoff weight under hot and high condition, but it has clear advantage in the bottom line of transporting more payload longer than the A346.

This is just one scenario though. I would love to see if others have other scenario that have other conclusions.

Cheers,
PP
 
Arniepie
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RE: Hot And High Performance B773ER Vs. A346

Sat May 31, 2008 9:14 am

Why make 2 threads about basically the same thing???

Also, where is that picture of beating over the death horse?
 
ThirtyEcho
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RE: Hot And High Performance B773ER Vs. A346

Sat May 31, 2008 10:31 am

The term "hot and high" means an aircraft that is both over profile speed and altitude on final approach. The term "hot" means airspeed and "high" means altitude relative to the desired glide slope.

For both aircraft, being "hot and high" would dictate a go-around.

Maybe, you would like to rephrase your topic? Otherwise, it makes no sense.
 
hotelmode
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RE: Hot And High Performance B773ER Vs. A346

Sat May 31, 2008 11:18 am

ISA +15 is not hot at all. Its only +14 degrees at 8000ft. Hot and High would be 5-8000ft at ISA +30 or more. Like Nairobi or Mexico.
 
hotelmode
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RE: Hot And High Performance B773ER Vs. A346

Sat May 31, 2008 11:21 am



Quoting ThirtyEcho (Reply 2):
The term "hot and high" means an aircraft that is both over profile speed and altitude on final approach. The term "hot" means airspeed and "high" means altitude relative to the desired glide slope.

Wrong Hot and High. Title makes perfect sense

In this case it means high elevation airfield in hot temperatures.
 
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Starlionblue
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RE: Hot And High Performance B773ER Vs. A346

Sat May 31, 2008 12:08 pm



Quoting ArniePie (Reply 1):

Also, where is that picture of beating over the death horse?

That's almost better than the real expression, which "beating a dead horse". Big grin
 
PolymerPlane
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RE: Hot And High Performance B773ER Vs. A346

Sat May 31, 2008 1:34 pm



Quoting ArniePie (Reply 1):
Why make 2 threads about basically the same thing???

Did you even read the other thread? I was not comparing the OEW of B777 and A340. It was about why there's a 50klbs difference between 773ER and 772LR  Yeah sure

Quoting Hotelmode (Reply 3):

ISA +15 is not hot at all. Its only +14 degrees at 8000ft. Hot and High would be 5-8000ft at ISA +30 or more. Like Nairobi or Mexico.

I would love to see ISA+30 if the data is available

Cheers,
PP
 
A342
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RE: Hot And High Performance B773ER Vs. A346

Sat May 31, 2008 7:23 pm



Quoting PolymerPlane (Reply 6):
I would love to see ISA+30 if the data is available

IIRC there is public data for something like ISA+22 (because certain engines are flat-rated to that temperature), but that's for 747-200s.
 
sanjet
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RE: Hot And High Performance B773ER Vs. A346

Sat May 31, 2008 9:30 pm



Quoting ThirtyEcho (Reply 2):

You're completely wrong on that issue. Hot and high does actually mean an elevated surface with hot temperatures. We don't use "hot & high" to describe an approach.
 
TropicalSQ744
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RE: Hot And High Performance B773ER Vs. A346

Sun Jun 01, 2008 2:30 pm

I remember reading an article from AIrline Business mag here on Anet. It was analysing the 346 against the 77W for various city pairs and they mentioned that the 77W was not even in South African Airways' list of suitable 744 replacements because of wheel temperature issues related to taking off from a hot-and-high airport like Johannesburg.

Anyone remember that article? Perhaps things have changed since that article was written. The article was published before the 77W entered service.
 
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sunrisevalley
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RE: Hot And High Performance B773ER Vs. A346

Sun Jun 01, 2008 7:39 pm



Quoting TropicalSQ744 (Reply 9):
because of wheel temperature issues related to taking off from a hot-and-high airport like Johannesburg.

Aircraft Commerce had an article in Feb/March 2001 saying that the 77W would be restricted in TOW at JNB because of tire speed. The charts dated December 2007 while not covering a range that includes JNB ( 24C Ele. 5568 feet) are unchanged from the earlier ones dated June 2004. Very roughly the MTOW for the 77W from JNB based on the afore mentioned standard appears to be about 675K lbs.
 
Mir
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RE: Hot And High Performance B773ER Vs. A346

Sun Jun 01, 2008 8:32 pm



Quoting ThirtyEcho (Reply 2):
The term "hot and high" means an aircraft that is both over profile speed and altitude on final approach.

In this case, hot and high means an airport with high density altitude (as part of the three things that adversely affect takeoff performance - high altitude, hot temperatures, and heavy aircraft). It makes perfect sense.

Quoting TropicalSQ744 (Reply 9):
I remember reading an article from AIrline Business mag here on Anet. It was analysing the 346 against the 77W for various city pairs and they mentioned that the 77W was not even in South African Airways' list of suitable 744 replacements because of wheel temperature issues related to taking off from a hot-and-high airport like Johannesburg.

If I'm not mistaken, quads have better engine-out performance than twins in hot and high conditions.

-Mir
 
Max Q
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RE: Hot And High Performance B773ER Vs. A346

Sun Jun 01, 2008 10:44 pm

It is quite reasonable to use the expression 'hot and high' for both the aforementioned scenarios !
 
EA772LR
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RE: Hot And High Performance B773ER Vs. A346

Mon Jun 02, 2008 2:43 pm



Quoting SunriseValley (Reply 10):
Very roughly the MTOW for the 77W from JNB based on the afore mentioned standard appears to be about 675K lbs.

That can't be right.....a 100K lb penalty for the airport conditions at JNB??
 
sierra1bravo
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RE: Hot And High Performance B773ER Vs. A346

Mon Jun 02, 2008 3:32 pm

Slightly off-topic, but here is an example of a hot-high-heavy accident (IUX, India, 1993). The Aurangabad airport is close to 2000 ft in elevation, and temperatures in April would be close to 38-41 degrees Celsius:

http://aviation-safety.net/database/record.php?id=19930426-1

One of the pilot was a woman (no prejudice), and there seems to have been a weight-and-balance issue as well.

s1b
 
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Starlionblue
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RE: Hot And High Performance B773ER Vs. A346

Mon Jun 02, 2008 3:38 pm



Quoting Sierra1bravo (Reply 14):
One of the pilot was a woman (no prejudice),

If there's no prejudice why are you even mentioning it?  Wink
 
sierra1bravo
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RE: Hot And High Performance B773ER Vs. A346

Mon Jun 02, 2008 3:50 pm

I guess you do not know the context...especially that this was about 15 years back in India, when women *car* drivers were looked down upon as accident-prone. I wouldn't perhaps mention the bracketed text today...

Don't want to stir up a controversy with my very first post  Smile

s1b
 
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sunrisevalley
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RE: Hot And High Performance B773ER Vs. A346

Mon Jun 02, 2008 5:09 pm



Quoting EA772LR (Reply 13):
That can't be right.....a 100K lb penalty for the airport conditions at JNB??

go to http://www.boeing.com/commercial/airports/acaps/777rsec3.pdf and look at pages
3.3.7 and 3.3.8 and track the 6000' altitude curve on both.
I think you will find that I am not too far off.
 
Pihero
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RE: Hot And High Performance B773ER Vs. A346

Mon Jun 02, 2008 6:01 pm



Quoting PolymerPlane (Thread starter):
Here are the basic numbers (assuming 365 pax and TOW from the take off performance graph)

____________A346_________B773ER
OEW____ 176,364 kg____ 167,829 kg
TOW____ 310,000 kg____ 290,000 kg
Payload__ 34,368 kg ____ 34,368 kg



if I understand the gist of your post , you are looking into max range with x pax out of an 9,000 ft high airport ? Right ?
In this case your demonstration is very flawed.
The way to do it is to determine the *Zero fuel Weight*, ZFW to which there is a structural limitation, MZFW, not reached here.

ZFW = OEW + LOAD

Then, determine the amount of fuel you can load on that airplane; its called Fuel on board or FOB. That load is limited by the max take off weight for the conditions you have determined, so :

FOB = MTOW - ZFW,

and you have the ways to estimate the range of these aircraft with the specific fuel consumption between TOW and (ZFW + Reserve ) . It's only then that you'd have an accurate result.

Dealing a lot with ball park figures before accurate computations, I find thus that the fuel put on board both aircraft is :
1/- For the 340 :
310 - ( 176.4 + 34.4 ) = 99. 8 tons and compute specific range between 310 tons and 220 tons.

2/- For the 777 :
290 - ( 167.8 + 34.4 ) = 87.8 tons and compute specific range between 290 tons and 211 tons.

Why the specific ranges ? It's because the lighter a given plane, the less fuel it burns for a given distance, and then even less for it has burn the fuel for that distance......ad infinitum.

Try and find on the forum the guys who could do a quick NAM table extraction. Try Zeke, he's generally full of info. Or others.
What I can tell you is that IMO, the 340 with 12 tons more fuel than the 777 while being just nine tons heavier should surpass the 777 range.

regards
 
PolymerPlane
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RE: Hot And High Performance B773ER Vs. A346

Mon Jun 02, 2008 7:22 pm



Quoting Pihero (Reply 18):
if I understand the gist of your post , you are looking into max range with x pax out of an 9,000 ft high airport ? Right ?
In this case your demonstration is very flawed.

it's 8000 ft, and yes that's what I was trying to show.

What I did was not flawed. I just took the the maximum TOW given the runway and elevation limitation from the ACAP, and use the payload-range curve at a given TOW. It is available from Boeing's website. From that particular payload-range curve, I found the payload and get the range.

While Airbus does not give the payload range for various TOW's, I estimated the range penalty for the TOW reduction from the graph, given the range penalty from B773ER

Quoting Pihero (Reply 18):
What I can tell you is that IMO, the 340 with 12 tons more fuel than the 777 while being just nine tons heavier should surpass the 777 range.

That is not really unheard of. Using the formula you mentioned at MTOW
A346
380-(176.4 + 34.4) = 169.2 for a range of 7800 NM

777
351.5-(167.8+34.4) = 149.3 for a range of 7900 NM
However, 773ER at that condition does not take off at MTOW. It is fuel volume limited with useable fuel only 145.5 tonnes. So, the difference in fuel consumption is roughly 25 tonnes of fuel.

Maybe my estimate is a bit on the high side, but the basic premise is still the same. At hot and high B773ER can still carry similar payload-distance as A346, thus not inferior to the latter

Cheers,
PP
 
Pihero
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RE: Hot And High Performance B773ER Vs. A346

Mon Jun 02, 2008 9:25 pm



Quoting PolymerPlane (Reply 19):
, I estimated the range penalty for the TOW reduction from the graph, given the range penalty from B773ER

And I say you are wrong. It's the fuel carried that would make any difference, not some substract from MTOW.
This is the case when you announce :

Quoting PolymerPlane (Reply 19):
However, 773ER at that condition does not take off at MTOW. It is fuel volume limited with useable fuel only 145.5 tonnes.

Another case for the goose and the gander, perhaps.

This reminded me of a discussion we had some eighteen months ago and, just taking JNB as an example, I demonstrated that a 772 wasn't the sparkling phoenix some thought of against as derided a lowly bird as the 343.
 
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sunrisevalley
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RE: Hot And High Performance B773ER Vs. A346

Mon Jun 02, 2008 10:44 pm



Quoting PolymerPlane (Reply 19):
777
351.5-(167.8+34.4) = 149.3 for a range of 7900 NM

I don't have time right now to go through the detail but the MTOW of the 77W at 8000' elevation on a standard day is about 293t according to the reference I gave in reply 17.
If you plot that on the load range table on page 3.2.2. you get about 7300nm range at OEW. So the best that can be done is ferry an empty aircraft 7300nm at that MTOW.
PP, I'm afraid I don't understand where you are coming from on this example.
 
PolymerPlane
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RE: Hot And High Performance B773ER Vs. A346

Mon Jun 02, 2008 11:28 pm



Quoting SunriseValley (Reply 21):
PP, I'm afraid I don't understand where you are coming from on this example.

That particular example I choose is to illustrate the difference in fuel at MTOW at ISA and sea level condition. that's why I came up with 25 tonnes fuel difference.

The example in the thread starter was for 8000 ft standard temperature +15. At that TOW, the range is only about 5300 NM.

Cheers,
PP
 
Pihero
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RE: Hot And High Performance B773ER Vs. A346

Tue Jun 03, 2008 5:20 pm



Quoting PolymerPlane (Reply 22):
The example in the thread starter was for 8000 ft standard temperature +15. At that TOW, the range is only about 5300 NM.

I just had a look at your graphs, PolymerPlane.
Forget them, they are for Hot-and-High conditions useless as they only refer to runway length conditions and brake energy limits, conveniently omitting climb performance, especially the 2nd segment requirements, which is the limiting factor at altitude.

Therefore, your study is worthless.
Sorry, better chance next time.

Nb : If I am in error, I'll be glad to accommodate you to the best restaurant in Paris. Your choice. And a promise.

Regards
 
PolymerPlane
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RE: Hot And High Performance B773ER Vs. A346

Tue Jun 03, 2008 6:25 pm



Quoting Pihero (Reply 23):
I just had a look at your graphs, PolymerPlane.
Forget them, they are for Hot-and-High conditions useless as they only refer to runway length conditions and brake energy limits, conveniently omitting climb performance, especially the 2nd segment requirements, which is the limiting factor at altitude.

First of all it's not my graph, it's Boeing's graph.

It says it is F.A.R take off runway length requirement. I take it that the F.A.R take off requirment includes reaching V2 from 35 feet to 400 feet with a certain climb gradient. Well I'm not an expert in the regulations, but I read the FAR runway take off requirement, which includes achieving crucial speeds after the take off to determine the take off distance.

I am sure this certification does not include all of the real world conditions such as obstacles, wind, etc. And there are places that B773ER won't be able to take off with anything close to n A346 economics (SXM for instance). But this is at least a generic place where we can compare apples to apples.

Quoting Pihero (Reply 23):
Nb : If I am in error, I'll be glad to accommodate you to the best restaurant in Paris. Your choice. And a promise.

Would love that, Never been to Paris though  wink .

In all seriousness, I may be wrong. I don't know the certification method Boeing took to publish that chart.

Cheers,
PP
 
Pihero
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RE: Hot And High Performance B773ER Vs. A346

Tue Jun 03, 2008 7:16 pm



Quoting PolymerPlane (Reply 24):
It says it is F.A.R take off runway length requirement. I take it that the F.A.R take off requirement includes reaching V2 from 35 feet to 400 feet with a certain climb gradient. Well I'm not an expert in the regulations, but I read the FAR runway take off requirement, which includes achieving crucial speeds after the take off to determine the take off distance.

 checkmark   checkmark   checkmark 

Quoting PolymerPlane (Reply 24):
I am sure this certification does not include all of the real world conditions

 checkmark  But second segment requirement is part of the certification. It has nothing to do with obstacles

Quoting PolymerPlane (Reply 24):
But this is at least a generic place where we can compare apples to apples.

That's the point, PP. As soon as you talk about high elevation runway, you're bound to hit the main performance wall of the second segment required gradient. By design, a twin is far more sensitive to it (loss of 50% thrust + addition of the major drag of a stopped engine.) than a quad which loses 25% of thrust and the additional drag of a much smaller-fronted engine.

Quoting PolymerPlane (Reply 24):
I don't know the certification method Boeing took to publish that chart.

It's called airport compatibility study. Not a lot to do with real life performance.
I think it will be my choice of restaurant...a lot cheaper but I know of a few that will blast your taste buds.


 Big grin
 
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zeke
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RE: Hot And High Performance B773ER Vs. A346

Sun Jun 08, 2008 2:23 pm

Some real numbers for JNB on a 30 deg day, QNH 1013, no wind, runway 03L :

Maximum takeoff weight under the conditions with most favorable takeoff configuration (optimum flap setting, optimum thrust, and packs off)

744 - 346,800 kg
346 - 346,000 kg
77W - 302,800 kg
343 - 248,000 kg
333 - 215,000 kg

Payload available (fuel, passengers, cargo etc) for each type would be about

346 187,700 kg
744 183,700 kg
77W 134,200 kg
343 122,800 kg
333 95,100 kg

The 77W only lifts about 11,400 kg more total payload (fuel, passengers, cargo) over a 343, but the 77W burns about 1,200 kg more an hour than the 343.
 
A342
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RE: Hot And High Performance B773ER Vs. A346

Sun Jun 08, 2008 8:00 pm



Quoting Zeke (Reply 26):
Payload available (fuel, passengers, cargo etc)

Maybe I'm nit-picking, but wouldn't this be called useful load?  Smile
 
rheinwaldner
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RE: Hot And High Performance B773ER Vs. A346

Mon Jun 09, 2008 9:03 am



Quoting Zeke (Reply 26):

That's why SA choose the A346. It's a winner for them.
 
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seabosdca
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RE: Hot And High Performance B773ER Vs. A346

Mon Jun 09, 2008 6:09 pm



Quoting Zeke (Reply 26):
Payload available (fuel, passengers, cargo etc) for each type would be about

What flavor of A346 were these numbers for? I assume the early CX birds? If so, the HGW versions with Trent 560s will look even better.

SA might be able to fly nonstop to the US from JNB with 345s, at least most of the time. Too bad such flights would be unlikely to make much money.
 
PolymerPlane
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RE: Hot And High Performance B773ER Vs. A346

Wed Jun 11, 2008 2:45 am



Quoting Zeke (Reply 26):
744 - 346,800 kg
346 - 346,000 kg
77W - 302,800 kg
343 - 248,000 kg
333 - 215,000 kg

I am sure you have the real world number, but these numbers doesn't seem to match the Airbus/Boeing's charts. Especially when we compare 744 and A346.

According to Boeing's 744's chart, at 5000 ft ISA + 17.2 the TOW is somewhere around 380 tonnes, while according to Airbus's A346's chart, at 5000 ft ISA + 15 the TOW is somewhere around 355 tonnes. while 77W at 5000 ft ISA + 15 TOW is somewhere around 325 tonnes. Lastly 343 at 5000 ft ISA + 15 has TOW around 250 tonnes

Is there any other consideration exept altitude and temperature flying out of JNB?

I know that it is not at 30 C, but it seems to me that only boeing's planes takes more penalty from ISA+15 to 30 C than Airbus's planes. Especialy considering that the 744 takes a huge weight penalty while being a quad.

Cheers,
PP
 
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keesje
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RE: Hot And High Performance B773ER Vs. A346

Tue Sep 29, 2009 9:09 am



Quoting Zeke (Reply 26):
Payload available (fuel, passengers, cargo etc) for each type would be about

346 187,700 kg
744 183,700 kg
77W 134,200 kg
343 122,800 kg
333 95,100 kg

How much of this would be revenue payload and how much fuel?
 
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zeke
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RE: Hot And High Performance B773ER Vs. A346

Tue Sep 29, 2009 10:48 am



Quoting PolymerPlane (Reply 30):
Is there any other consideration exept altitude and temperature flying out of JNB?

I know that it is not at 30 C, but it seems to me that only boeing's planes takes more penalty from ISA+15 to 30 C than Airbus's planes. Especialy considering that the 744 takes a huge weight penalty while being a quad.

The other way to use those charts is to use the field evelation and temps/QNH to calculate the density height. You can then use the density heght calculated on the "standard day" chart.

e.g. for JNB 03L
TODA 4478 meters
Elevation 5558 ft
QNH 1013
Temp 30
Dew point 27
Density height = 9015 ft

Using the 744 chart with RB211 engines, you get pretty close to the 346,800 kg calculated.



Quoting Keesje (Reply 31):

How much of this would be revenue payload and how much fuel?

That all depends on sector length.
 
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keesje
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RE: Hot And High Performance B773ER Vs. A346

Tue Sep 29, 2009 11:35 am



Quoting Zeke (Reply 32):
Quoting Keesje (Reply 31):

How much of this would be revenue payload and how much fuel?

That all depends on sector length.

Well say 5000 nm (Europe).

I guess the 773ER has better fuel consumption, but not enough to compensate the 50.000 kg pay load disadvantage..

Not surprising even without the numbers, I'm not looking forward to experience a 1 engine MTOW take-off from a hot & high airfield. I've been on training flights but those were light & not hot/ heigh, cold & below sea level actually  Wink
 
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zeke
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RE: Hot And High Performance B773ER Vs. A346

Tue Sep 29, 2009 1:32 pm



Quoting Keesje (Reply 33):
Well say 5000 nm (Europe).

You would need to run a real flight plan to get an accurate view, in the ballpark of

346 78,000 kg
744 62,000 kg
77W 36,000 kg
343 37,000 kg
333 20,000 kg

Running real flight plans would get the real track miles, actual alternates, contingency fuel, ETOPS buildup, and level available. I think Pherio posted some numbers for the 343 and 772ER from JNB to CDG at one stage.
 
rheinwaldner
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RE: Hot And High Performance B773ER Vs. A346

Tue Sep 29, 2009 2:41 pm



Quoting Zeke (Reply 34):
346 78,000 kg
744 62,000 kg
77W 36,000 kg
343 37,000 kg
333 20,000 kg

That would mean that the 77W would use 10000 kg less fuel but the payload would be almost 40000 kg less.

What will SAA do, once there are no more quads?
 
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Stitch
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RE: Hot And High Performance B773ER Vs. A346

Tue Sep 29, 2009 5:01 pm



Quoting Rheinwaldner (Reply 35):
What will SAA do, once there are no more quads?

Probably go for ULR-spec twins like the 777-200LR and planned A350-900R in order to try and load up as much payload as you can before you hit tire limits.

They could also commission and pay for development of more durable tires able to take higher speeds to allow large twins (777-300ER / A350-1000XWB) to hit higher runway speeds.
 
A342
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RE: Hot And High Performance B773ER Vs. A346

Tue Sep 29, 2009 5:30 pm



Quoting Stitch (Reply 36):
They could also commission and pay for development of more durable tires able to take higher speeds to allow large twins (777-300ER / A350-1000XWB) to hit higher runway speeds.

Don't forget higher-performance brakes, which are also a deciding factor when operating from high airports.
 
borism
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RE: Hot And High Performance B773ER Vs. A346

Tue Sep 29, 2009 6:22 pm

Where will the quads go?

I thought A380 and maybe even B748 will be produced for years to come?
 
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keesje
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RE: Hot And High Performance B773ER Vs. A346

Tue Sep 29, 2009 7:37 pm



Quoting Zeke (Reply 34):
in the ballpark of

thnx.

Quoting Rheinwaldner (Reply 35):
What will SAA do, once there are no more quads?

I dreamed up a XWB trijet after Airbus patented a new tail engine technology but did not do the numbers yet. Most people think a trijet can never be succesfull again. I think maybe for the 380-500 seat category it might theoretically the best compromise between 2 engine efficiency and 4 engine redundancy.

https://www.airliners.net/aviation-forums/tech_ops/read.main/256943
 
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zeke
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RE: Hot And High Performance B773ER Vs. A346

Tue Sep 29, 2009 9:05 pm



Quoting Rheinwaldner (Reply 35):
What will SAA do, once there are no more quads?

The simplest suggestion would be to have more night departures when the temp is lower, below 20 degC most twins out of JNB seem to fair better. During the day it would pay to first fly to CPT before heading to Europe.

Quoting Stitch (Reply 36):
Probably go for ULR-spec twins like the 777-200LR and planned A350-900R in order to try and load up as much payload as you can before you hit tire limits.

The 77L has the same problems as the 77W, it is slightly better, but nothing to write home about. No idea on the A350XWB performance yet, but I expect it would have better runway performance than the 777.
 
OldAeroGuy
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RE: Hot And High Performance B773ER Vs. A346

Wed Sep 30, 2009 3:09 pm

The A346 OEW implied in your useful load calculation looks to be a bit suspect.

TOW = OEW + Useful load

Quoting Zeke (Reply 26):
Payload available (fuel, passengers, cargo etc) for each type would be about

346 187,700 kg
77W 134,200 kg



Quoting Zeke (Reply 26):

346 - 346,000 kg
77W - 302,800 kg

Using the numbers you supplied, you get these OEW values:

A346 - 158.3 tonne
773ER - 168.6 tonne

From the OEM's you get the following OEW numbers:

A346 - 176.4 tonne
773ER - 167.8 tonne

http://www.airbus.com/fileadmin/medi...s/tech_data/AC/AC_A340-500-600.pdf
(page 18)

http://www.boeing.com/commercial/airports/acaps/777rsec2.pdf
(page 3)

With the revised OEW's, the new useful load would be:

A346 - 169.6 tonne
773ER - 135.0 tonne

Quoting Zeke (Reply 34):
You would need to run a real flight plan to get an accurate view, in the ballpark of

346 78,000 kg
77W 36,000 kg

If you use the new useful load calculation, the ball park available payload would be:

A346 - 59.9 tonne
773ER - 36.8 tonne

The A346 still has more revenue payload, but the delta is about 23 tonne, not 52 tonne.

To look at it in another way, the 773ER can carry a full load of passengers while the A346 can carry full passengers plus cargo for the approximate 5000 nm mission you quoted.

Quoting Zeke (Reply 32):
The other way to use those charts is to use the field evelation and temps/QNH to calculate the density height. You can then use the density heght calculated on the "standard day" chart.

This method works OK as long as the same engine thrust limits are being used. It's common for the engine OEM to offer thrust "bumps" for high, hot conditions. If the airline needs to use the "bump", they pay the OEM for it if the additional revenue payload is worth it. Use of a thrust bump will throw off the density height method.

Quoting Zeke (Reply 40):
The simplest suggestion would be to have more night departures when the temp is lower, below 20 degC most twins out of JNB seem to fair better.

This is what DL does on their JNB - ATL 772LR non-stop. The flight has a 2100 takeoff with a 0600 arrival. This inceases available payload and provides a useful schedule. Taking off at 1600 with a 0100 arrival wouldn't make sense for the airline or its customers.

Quoting Zeke (Reply 40):
The 77L has the same problems as the 77W, it is slightly better, but nothing to write home about.

While the 772LR and the 773ER will have similar TOW's, the 772LR OEW is 22.2 tonne less than the 773ER (145.6 vs 167.8).

This means its revenue payload for the mission quoted above is 59.0 tonne, about equal to that of the A346. It will far outlift the 37.0 tonne of the similar sized A343.

This type of performance means SAA will still be OK as Quads become less numerous.

Quoting Zeke (Reply 40):
No idea on the A350XWB performance yet, but I expect it would have better runway performance than the 777.

Considering that the A350XWB wing area is larger than the 777 and it is supposed to have a much lower OEW, it should have better takeoff performance. It does depend on the engine thrust selection though which is also less than the 777.

The large A350XWB wing should help with the tire speed limit for high, hot operation.

[Edited 2009-09-30 08:22:59]
 
OldAeroGuy
Posts: 3928
Joined: Sun Dec 05, 2004 6:50 am

RE: Hot And High Performance B773ER Vs. A346

Thu Oct 01, 2009 4:36 am



Quoting Pihero (Reply 23):
Forget them, they are for Hot-and-High conditions useless as they only refer to runway length conditions and brake energy limits, conveniently omitting climb performance, especially the 2nd segment requirements, which is the limiting factor at altitude.

Many performance limits are show on the takeoff field - takeoff weight charts.

Let's take the Boeing charts from this link as an example:

http://www.boeing.com/commercial/airports/acaps/777rsec3.pdf

Look at page 10 and consider the 6000' elevation line. The lowest part of the line, from about 425K lb to 490K lb is for the highest deflection takeoff flap but limited by Vmcg.

From 490K lb to 640K lb, the highest takeoff flap is still be used but at the minimum speed for a given weight.

At 640K lb, weight has increased to the point that the 2nd segment climb limits can no longer be met at minimum speed.

From 640K lb to 650K lb, increased speed for a given weight is being used to meet the minimum 2nd segment climb limit. This is characterized by an upwards break in the field length - weight line.

At 650K lb, it's now better to use a takeoff flap with a lesser deflection and lower 2nd segment drag.

This why that the curve breaks downwards from 650K lb to 665K lb. At 665K lb, the 2nd segment climb limit is again reached and the same set of improved climb speeds/flap deflection choices are made.

This continues until the liftoff tire speed limit is reached at 705K lb.

Quoting A342 (Reply 37):
Don't forget higher-performance brakes, which are also a deciding factor when operating from high airports.

Improving brake performance will not always improve high, hot takeoff performance. In the example cited above, there is no brake energy limit below the tire speed limit. For this case, better brakes will not help.
 
User avatar
zeke
Posts: 16447
Joined: Thu Dec 14, 2006 1:42 pm

RE: Hot And High Performance B773ER Vs. A346

Thu Oct 01, 2009 6:51 pm



Quoting OldAeroGuy (Reply 41):
The A346 OEW implied in your useful load calculation looks to be a bit suspect.

I went back and had a look at the spreadsheet I did for that, all the payload numbers were out because of a column I did not reference correctly (alternate takeoff config). The OEW I used were real ones, about 5t heavier than the respective manufacturers documents for the 77W and 346.

The list should be

744 177
A346 179
77W 131
A343 119
A333 90

Approx payload for 5000 nm

744 55
A346 72
77W 33
A343 33
A333 15

The numbers above again are ballpark only.

Quoting OldAeroGuy (Reply 41):
This method works OK as long as the same engine thrust limits are being used. It's common for the engine OEM to offer thrust "bumps" for high, hot conditions. If the airline needs to use the "bump", they pay the OEM for it if the additional revenue payload is worth it. Use of a thrust bump will throw off the density height method.

The numbers I used included the bump were we have it (e.g. 77W).

Quoting OldAeroGuy (Reply 41):
While the 772LR and the 773ER will have similar TOW's, the 772LR OEW is 22.2 tonne less than the 773ER (145.6 vs 167.8).

This means its revenue payload for the mission quoted above is 59.0 tonne, about equal to that of the A346. It will far outlift the 37.0 tonne of the similar sized A343.

Comparing the 77L to the 343 is like comparing the 345 to the 772. The 345 would out-lift the 77W and 77L.
 
OldAeroGuy
Posts: 3928
Joined: Sun Dec 05, 2004 6:50 am

RE: Hot And High Performance B773ER Vs. A346

Thu Oct 01, 2009 8:49 pm

Quoting Zeke (Reply 43):
The OEW I used were real ones, about 5t heavier than the respective manufacturers documents for the 77W and 346.

You qouted the following TOW's:

Quoting OldAeroGuy (Reply 41):
Quoting Zeke (Reply 26):

346 - 346,000 kg
77W - 302,800 kg

Your new useful loads are:

Quoting Zeke (Reply 43):

A346 179
77W 131

That means your new OEW is:

A346

OEW = TOW - Useful Load
OEW = 346.0t - 179t
OEW = 167t

773ER

OEW = TOW- Useful Load
OEW = 302.8t - 131t
OEW = 171.8t

From the OEM's you get the following OEW numbers:

A346 - 176.4 tonne
773ER - 167.8 tonne[/quote]

Relative to the OEM OEW's, your new OEW's have the A346 being 9.4t lighter and the 773ER being 4.0t heavier.

You can confirm the Airbus A346 OEW from page 18 of this link.

http://www.airbus.com/fileadmin/medi...s/tech_data/AC/AC_A340-500-600.pdf

If you want to add 5t to the OEM OEW to represent an airline OEW, that's fine, but you need to start with the correct OEW.

Not even Airbus thinks the A346 has a lower OEW than the 773ER.

Quoting Zeke (Reply 43):

A346 72
77W 33

The relationship of these numbers is still incorrect because of your erroneous OEW calculation.

PS

Your 744 OEW looks to be incorrect as well.

OEW = TOW - Useful Load
OEW = 346.8 - 177.0
OEW = 169.8t

Boeing says the 744 with RR has an OEW of:

179.9t

Your OEW value is 10.1 less than the OEM.

http://www.boeing.com/commercial/airports/acaps/7474sec2.pdf
page 5

[Edited 2009-10-01 14:27:19]
 
User avatar
zeke
Posts: 16447
Joined: Thu Dec 14, 2006 1:42 pm

RE: Hot And High Performance B773ER Vs. A346

Thu Oct 01, 2009 10:15 pm



Quoting OldAeroGuy (Reply 44):
OEW = 346.0t - 179t

Should be 364, not 346.

Quoting OldAeroGuy (Reply 44):
OEW = 346.8 - 177.0

Should be between 360-365, must had 346 my brain. OEW still about 5t heavier than manufacturers spec.
 
OldAeroGuy
Posts: 3928
Joined: Sun Dec 05, 2004 6:50 am

RE: Hot And High Performance B773ER Vs. A346

Fri Oct 02, 2009 1:38 pm

Really? In Reply 32, you were very confident that the 744 takeoff weight at JNB on a 30 deg C day was 346.8t.

Quoting Zeke (Reply 32):
Using the 744 chart with RB211 engines, you get pretty close to the 346,800 kg calculated.



Quoting Zeke (Reply 45):
Quoting OldAeroGuy (Reply 44):
OEW = 346.0t - 179t

Should be 364, not 346.

After reviewing the the takeoff data from the following link, it appears that the A346 TOW from JNB on a 30 deg C would be on the order of 338.5t, not 346t or 364t.

http://www.airbus.com/fileadmin/medi...s/tech_data/AC/AC_A340-500-600.pdf

See pages 58 and 60.

To summarize:

TOW @ JNB 30 deg C

744 - 346.8t
A346 - 338,5t
773ER - 302.5t

OEM OEW

744 - 179.9t
A346 - 176.4t
773ER - 167.8t

OEM OEW + 5t

744 - 184.9t
A346 - 181.4t
773ER - 172.8t

Useful Load

744 - 161.9t
A346 - 157.1t
773ER - 129.7t

5000 nm Fuel

744 - 122t
A346 - 107t
773ER - 98t

Approximate Payload

744 - 40t
A346 - 50t
773ER - 32t

The A346 has a very respectable payload, especially in relation to the 744, since that's a Quad-to-Quad comparison, The A346 advantage is mainly due to its later generation engines that significantly reduce fuel burn.

Quoting Zeke (Reply 43):
The 345 would out-lift the 77W and 77L.

Will it?

While I agree that the A345 will deliver more payload on the mission being discussed than the 773ER, it's not obvious that it will out perform the 772LR by a significant margin.

The takeoff weights and mission fuel burns will be about tne same for the A345 compared to the A346 for the mission being discussed. The same is true for the 772LR compared to the 773ER. Therefore the difference in mission payload will be the OEW differences.

From OEM data:

OEW

A346 - 176.4t
A345 - 170.4t
Delta - 6t

773ER - 167.8t
772LR - 145.2t
Delta - 22.6t

Applying these increments to the previous Payload numbers:

Payload:

A345 - 56t
772LR - 54t

So the A345 would have a 2t advantage.

As a final word however, Airbus does have revised OEW's for the 380t MTOW versions of the A345 & A346

OEW

A345 - 174.8t
A346 - 181.9t

http://www.airbus.com/en/aircraftfam...0a340/a340-500/specifications.html

http://www.airbus.com/en/aircraftfam...0a340/a340-600/specifications.html

If these 4t higher OEW's are applied to the previous mission Payloads, the new bottom line becomes:

744 - 40t
A346 - 46t
773ER - 32t
A345 - 52t
772LR - 54t

So the 772LR would have the best payload for the route in question.
 
User avatar
zeke
Posts: 16447
Joined: Thu Dec 14, 2006 1:42 pm

RE: Hot And High Performance B773ER Vs. A346

Sat Oct 03, 2009 9:22 am



Quoting OldAeroGuy (Reply 46):

After reviewing the the takeoff data from the following link, it appears that the A346 TOW from JNB on a 30 deg C would be on the order of 338.5t, not 346t or 364t.

That chart is for a single flap setting and CG position. That is where the performance software can generate optimum thrust/flap configuration and alternate CG. The numbers I used are not from those charts, but from the performance mainframe. It has given better takeoff data for all the types I mentioned, and it looks at post takeoff climb gradients, it is approved data.

You know all this, and you are using an airport planning chart that is not approved for operational use to try and extract data that you know that covered in pages and pages in a performance manual. It just does not work, you know better, I KNOW you do, I do not understand why you are pretending anything different.

You seem have a bee in your bonnet about the poor 777 performance, I can send you the spread sheet if you want, just PM me.

Fact is the 777 is very poor for such a large expensive airframe out of JNB on a hot day, and yes the 345 would be better the the 77L, it will also be better than the 346 as well.

Quoting OldAeroGuy (Reply 46):
TOW @ JNB 30 deg C

744 - 346.8t
A346 - 338,5t
773ER - 302.5t

OEM OEW

744 - 179.9t
A346 - 176.4t
773ER - 167.8t

OEM OEW + 5t

744 - 184.9t
A346 - 181.4t
773ER - 172.8t

Useful Load

744 - 161.9t
A346 - 157.1t
773ER - 129.7t

5000 nm Fuel

744 - 122t
A346 - 107t
773ER - 98t

Approximate Payload

744 - 40t
A346 - 50t
773ER - 32

Those numbers are wrong.

Quoting OldAeroGuy (Reply 46):
As a final word however, Airbus does have revised OEW's for the 380t MTOW versions of the A345 & A346

The OEWs for the HGW versions are LOWER than the ones we had, by some margin, our first 346 had a 2t higher OEW than our following ones, and that was not even with the HGW. Again you know this, I KNOW you do. That is why early 345 operators had their aircraft go back for wing rework, to cut weight out.

Quoting OldAeroGuy (Reply 46):

So the 772LR would have the best payload for the route in question.

No, time to get back to reality.
 
slz396
Posts: 1883
Joined: Tue Oct 02, 2001 7:01 am

RE: Hot And High Performance B773ER Vs. A346

Sat Oct 03, 2009 10:31 am

I stepped in way too late to go deeply into all the numerical details, but I must say I agree with Zeke some seem a bit all too eager to proof the 777 is just as capable as the A340 under hot and high conditions, which obviously isn't the case as we all know: Hot an high conditions quickly turn ANY twin into a lemon really and no matter how admired the 777 may be, it is no exception to this rule really! If it were to be, it would be a greatly overpowered plane, with terrible CASM on the normal runs, something which we know it isn't!


Quoting Zeke (Reply 47):
You seem have a bee in your bonnet about the poor 777 performance

I don't know if it is done on purpose, but:

Quoting Zeke (Reply 47):
using an airport planning chart that is not approved for operational use to try and extract data that you know is covered in pages and pages in a performance manual just does not work, you know better, I KNOW you do, I do not understand why you are pretending anything different.

If it would be that easy, airlines operational departments wouldn't be using software to get the optimum settings and loadings; flightcrew could just do the calculation in a second on the spot!

One can discuss the exact OEW for real airline configuration, but this can only give a few tons of difference and has to be added across all types, so it's really a non-issue in this relative appreciation.

Quoting Zeke (Reply 47):
Fact is the 777 is very poor for such a large expensive airframe out of JNB on a hot day, and yes the 345 would be better the the 77L, it will also be better than the 346 as well.

That's what real word facts show.

A 77W can lift out merely half of what an A346 can at JNB. The 77W is a lemon under those conditions, as is clearly demonstrated if you use professional performance software, whether that difference is 28 or 32 tons, is of no importance really as the gap is so huge, they aren't in the same league!
 
User avatar
zeke
Posts: 16447
Joined: Thu Dec 14, 2006 1:42 pm

RE: Hot And High Performance B773ER Vs. A346

Sat Oct 03, 2009 2:26 pm



Quoting Slz396 (Reply 48):


A 77W can lift out merely half of what an A346 can at JNB. The 77W is a lemon under those conditions, as is clearly demonstrated if you use professional performance software, whether that difference is 28 or 32 tons, is of no importance really as the gap is so huge, they aren't in the same league!

To be fair, the 77W is very comparable to the 744 at seal level conditions, JNB is on the outer edge of the bell curve of airport operations. As JNB is not anywhere near a financial/business center (compared globally), the second best option with higher airfares seem to be accepted.

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