Thrust From United States of America, joined Sep 2003, 2668 posts, RR: 16 Posted (4 months 23 hours ago) and read 2231 times:
Hi there. I've been wondering how Air France can operate the A340 non-stop to CDG out of SXM...is there a stop I don't know about, or what? It just baffles me that an aircraft known for eating up runway and climbing at definitely the slowest rate of any commercial airliner is able to get off such a short runway and clear those mountains, yet a 777l, which uses less runway and climbs 1000% better, is almost never operated out of there.
jetblueguy22 From United States of America, joined Nov 2007, 1518 posts, RR: 0 Reply 1, posted (4 months 23 hours ago) and read 2222 times:
From my understanding the flight to SXM is direct while the flight back has a stop somewhere. Not 100% sure where but that stop is I'm not sure. I can't imagine it would even be close to getting off that runway fully loaded.
Blue
LimaFoxTango From Antigua and Barbuda, joined Jun 2004, 574 posts, RR: 0 Reply 3, posted (4 months 22 hours ago) and read 2217 times:
The runway at SXM is not as short as people think. The runway is about 7500' long. The concern in SXM is not so much the runway length, but outclimbing the obstacles after departure. To answer your question, the A340 does SXM-CDG direct. See the proof http://flightaware.com/live/flight/AFR3515 As to performance wise, I'll see someone else answer.
You are said to be a good pilot when your take-off's equal your landings.
If that's the case, how it can it be fully loaded...I've seen videos of it taking off at SXM...it takes much less time to get off the ground than normal and climbs at an astounding rate. Even if the runway is 7500 feet, a fully loaded A340 requires over 10,000 feet of runway to get airborne the last time I checked.
Thrust From United States of America, joined Sep 2003, 2668 posts, RR: 16 Reply 5, posted (4 months 22 hours ago) and read 2200 times:
I'm just saying that I'd be shocked if an A340 can get off the ground and clear mountains and climb like a DC-9 even with full engine thrust and heavily loaded, yet a 747, which is much heavier, uses up less runway typically on a takeoff, and climbs superiorly, can't get out of SXM fully loaded. It makes little sense. AF either has to use full thrust on takeoff or has to carry a much lighter load out of SXM.
vikkyvik From United States of America, joined Jul 2003, 6516 posts, RR: 29 Reply 6, posted (4 months 22 hours ago) and read 2195 times:
Quoting Thrust (Reply 4): Even if the runway is 7500 feet, a fully loaded A340 requires over 10,000 feet of runway to get airborne the last time I checked.
It might be fully loaded with passengers, but maybe not cargo, and certainly not fuel. SXM-CDG is about 3640nm per the great circle mapper. That's nowhere near the A340's max range.
Combine the relatively light weight with a potentially max-thrust takeoff, and you'll generally get pretty good takeoff and climb performance.
EDIT:
I'm just saying that I'd be shocked if an A340 can get off the ground and clear mountains and climb like a DC-9 even with full engine thrust and heavily loaded, yet a 747, which is much heavier, uses up less runway typically on a takeoff, and climbs superiorly, can't get out of SXM fully loaded. It makes little sense. AF either has to use full thrust on takeoff or has to carry a much lighter load out of SXM.
A 747 is heavier, and has higher engine thrust, larger wing, etc. to match. Regardless, it makes perfect sense - all airplanes are NOT created equal.
[Edited 2012-01-25 12:15:27]
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wagz From United States of America, joined Mar 2003, 484 posts, RR: 22 Reply 7, posted (4 months 21 hours ago) and read 2148 times:
I believe the true crux of the matter in SXM's case is engine-out climb performance due to the terrain. In the event of an engine failure on departure, an A340 still has 75% of its total thrust available. A 777 (or any twin) only has 50% of its total thrust available. I'd be surprised if a 777 in a normal scenario with both engines couldn't make the climb performance for a typical trip to Europe. However, an engine-out scenario must be accounted for. Therefore most other aircraft depart with the light fuel load and make the tech-stop to meet the engine-out climb requirements.
I'm certainly not an aerospace engineer, so I can't say why a 747 can't make the same climb performance and always requires the tech stop. Also, many of you need to get away from the idea that every airplane is "fully loaded" just because the passenger cabin may or may not be full. A 747 burns roughly 20,000lbs of fuel per hour (just a round number, and is probably higher at heavier weights). For a 3000nm trip at 500kts (just to make the math easy), that's 6 hours of trip burn for 120,000lbs of fuel. Then add in reserve, alternate and holding fuel. I don't know the actual tank capacity of the 747 off-hand, but considering it is capable of 12 hour missions you would be looking at more than twice as much fuel carried, plus your pax and cargo payload. 450 pax at 180lbs each is 81,000lbs. Adding in a generous amount of cargo and you're fuel weight is easily the same, if not more than your payload weight on the hypothetical six hour mission. At that point you're still probably 150,000lbs or more under Max Takeoff Weight. On the hypothetical 12 hour mission fuel could be twice as heavy as your payload.
A340 numbers will be lower due to decreased fuel burn and lower operating weights, but the ratios are still probably in the ballpark. Essentially you're never going to be able to "fully load" a passenger aircraft that's operating a flight only half of its theoretical range (unless you're doing something like tankering extra fuel).
Any pilots/dispatchers etc. that have the relevant weights and information please feel free to chime in and verify or disprove everything I have just said as I could be completely off base.
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RoseFlyer From United States of America, joined Feb 2004, 7621 posts, RR: 51 Reply 9, posted (4 months 20 hours ago) and read 2122 times:
With a 7,500ft runway, the A340-300 has about a 50,000 pound payload restriction over typical payload as shown on the A340 performance charts. That would limit its range or capacity. Fortunately this is a relatively short transatlantic route so fuel load is less and there likely is little cargo on the airplane. It's not ideal conditions because the A340-300 needs 8,500ft of runway at sea level with a typical payload. The good thing is that SXM is at sea level so the restrictions are not as bad.
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rfields5421 From United States of America, joined Jul 2007, 4871 posts, RR: 21 Reply 10, posted (4 months 20 hours ago) and read 2116 times:
Quoting Thrust (Reply 5): I'm just saying that I'd be shocked if an A340 can get off the ground and clear mountains and climb like a DC-9 even with full engine thrust and heavily loaded,
It has been mentioned on this forum before and I've seen videos - when the wind is light - the A340 takes off headed over the water with a slight tailwind on Rwy 28. While that reduces runway length, it also allows a lower climb rate. Often there is a headwind taking off on Rwy 28, while all the aircraft landing on Rwy 10 are with a tailwind.
Another thing is though the locals don't like it, an aircraft can make a turn right after takeoff on Rwy 10 and avoid having to climb over the hills.
The hills are a bigger issue for landing than for takeoff.
A similar example is LAX where most landings and takeoffs are on Rwy 24L/24R/25R/25L. That is for traffic flow, noise and political reasons, not weather. Frequenlty there is a light tailwind.
But the QF B747 often ask for, and receives permission to takeoff on a Rwy 8 or 9 because of weight they want every knot / foot of runway possible. ATC accommodates that request almost always.
vikkyvik From United States of America, joined Jul 2003, 6516 posts, RR: 29 Reply 11, posted (4 months 20 hours ago) and read 2095 times:
Quoting rfields5421 (Reply 10): It has been mentioned on this forum before and I've seen videos - when the wind is light - the A340 takes off headed over the water with a slight tailwind on Rwy 28. While that reduces runway length, it also allows a lower climb rate. Often there is a headwind taking off on Rwy 28, while all the aircraft landing on Rwy 10 are with a tailwind.
That's something that is often overlooked, because it's not as tangible an idea as runway length. Takeoff weights can be limited by required climb gradients, rather than runway length.
Quoting rfields5421 (Reply 10):
But the QF B747 often ask for, and receives permission to takeoff on a Rwy 8 or 9 because of weight they want every knot / foot of runway possible. ATC accommodates that request almost always.
Nitpick: you mean runways 6 or 7.
The spirit of Massachusetts is the spirit of America!
As far as whether or not the A340 is fully loaded on that route, I'm trying to figure that out...I would assume there is no possible way for it to operate out of SXM with the payload it would fly out of JFK, for example. I would assume there would be weight restrictions of some type, whether it would be passengers or cargo.
vikkyvik From United States of America, joined Jul 2003, 6516 posts, RR: 29 Reply 13, posted (4 months 19 hours ago) and read 2071 times:
Quoting Thrust (Reply 12): As far as whether or not the A340 is fully loaded on that route, I'm trying to figure that out...I would assume there is no possible way for it to operate out of SXM with the payload it would fly out of JFK, for example. I would assume there would be weight restrictions of some type, whether it would be passengers or cargo.
When you say "fully loaded", what exactly do you mean? Payload alone? Payload and fuel? As has already been stated, an A340 does not need full tanks to make that flight. That will cut down significantly on the takeoff weight and payload restrictions.
Beyond that, sounds like it may have further payload restrictions, but again, this does not necessarily mean fewer passengers.
I guess I'm not sure what exactly you're confused about - can you clarify?
The spirit of Massachusetts is the spirit of America!
Viscount724 From Switzerland, joined Oct 2006, 18467 posts, RR: 17 Reply 14, posted (4 months 18 hours ago) and read 2014 times:
Quoting Thrust (Reply 12): I would assume there would be weight restrictions of some type, whether it would be passengers or cargo.
There must be almost no air cargo from SXM. What do they produce that would require shipment by air? The only export I can find a reference to is some sugar, and that's hardly an item that's going to be shipped by air.
LimaFoxTango From Antigua and Barbuda, joined Jun 2004, 574 posts, RR: 0 Reply 15, posted (4 months 17 hours ago) and read 1998 times:
Quoting Thrust (Reply 12): As far as whether or not the A340 is fully loaded on that route, I'm trying to figure that out...I would assume there is no possible way for it to operate out of SXM with the payload it would fly out of JFK, for example. I would assume there would be weight restrictions of some type, whether it would be passengers or cargo.
Comparing JFK to SXM is like apples and oranges. Firstly, JFK is much farther away from CDG thus more fuel is required. It has longer runways and no hills on departure and probably loaded with cargo in the hold. SXM on the other hand, being closer to CDG requires less fuel and probably has no cargo other than bags which compensates for the shorter runway and the performance to outclimb the hills on departure. Air France does that flight every day without a problem so I'm not sure what the difficulty is in understanding why.
You are said to be a good pilot when your take-off's equal your landings.
yyzala From Canada, joined Nov 2009, 142 posts, RR: 0 Reply 16, posted (4 months 17 hours ago) and read 1990 times:
The A340 does not clear the mountain. It makes an immediate right turn to avoid the mountain. As such there no clearance requirements during performance calculations. The slight advantage the A340 has over the twins is increased performance during hot operations. I think the only reason Air France uses the A340 is because it makes economic sense for them in terms of payload.
Starlionblue From Greenland, joined Feb 2004, 15102 posts, RR: 69 Reply 19, posted (4 months 14 hours ago) and read 1912 times:
After all these years on A.nut it still baffles me that people think the 340 is some kind of performance dog and should therefore not "work". It is not the fastest climber but airlines don't buy airliners for their 0-100 km/h times. The 340 has plenty going for it, and on many missions has very good economics.
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wagz From United States of America, joined Mar 2003, 484 posts, RR: 22 Reply 22, posted (4 months 2 hours ago) and read 1693 times:
Quoting Starlionblue (Reply 19): After all these years on A.nut it still baffles me that people think the 340 is some kind of performance dog and should therefore not "work". It is not the fastest climber but airlines don't buy airliners for their 0-100 km/h times. The 340 has plenty going for it, and on many missions has very good economics.
Most don't understand it, but those of us that do still like to make fun of it. I work in ATC and LH flies an A340 to my airport everyday. And everyday they do a FLEX takeoff and climb slower than molasses and generally annoy our departure controller who has to get them to 9000 feet and above the arrival sector's airspace before he can turn them on course. Now I of course know why they're performing the way they do, and that they can do better if conditions warrant. But in reality the A340 climbs the slowest of all the aircraft we work (which is almost everything Boeing and Airbus, besides the A380). The only two aircraft I know of that we get semi-regularly that are worse than the A340, are the AN124 and the Nasa Super Guppy. I've heard stories from co-workers that have worked those that make the A340 sound like a completely empty 757 on a 10 mile ferry flight.
I think Big Foot is blurry, Its not the photographers fault. Theres a large out of focus monster roaming the countryside
PGNCS From United States of America, joined Apr 2007, 2443 posts, RR: 47 Reply 24, posted (3 months 4 weeks 1 day 14 hours ago) and read 1463 times:
Quoting wagz (Reply 22): everyday they do a FLEX takeoff
How do you know when they use TOGA or Flex? I never tell ATC what power setting I use for TO.
Quoting Mir (Reply 21): Quoting Thrust (Thread starter):
yet a 777l, which uses less runway and climbs 1000% better
Not with an engine out, which is what matters.
A fair point, Mir. A twin will perform better all-engines; the three or four-engine aircraft will definitely perform better engine out when similarly loaded, which is what performance calculations are based on.
25 wagz: I don't, but its pretty obvious when they use 9,500 ft of a 10,500 ft runway for takeoff roll on the "short" flight across the pond to FRA. Then they
26 seabosdca: Just like the 727, it doesn't climb very fast, but it gets off the ground in a reasonable amount of runway space even under surprisingly difficult co
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