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Do Airlines Use Their A/C To The Max Performance?  
User currently offlinec5load From United States of America, joined Sep 2008, 917 posts, RR: 0
Posted (3 years 6 months 3 days 20 hours ago) and read 4752 times:

With airliners getting heavier and longer range these days, do airlines really max perform their airplanes? Take a couple of the biggest planes nowadays: A380, B777-300ER, and the 747-400. The A380s MTOW is around 1.2 million lbs. Do airlines really try and pack fuel, cargo, and pax to reach that weight? That's the only way it'll make money won't it? That goes for the 77W and the 744

77W: MTOW-775K
744: MTOW-910K

If airlines don't need the fuel for that particular mission, would they try and make up that weight in extra cargo, if it can fit? I guess the point of my question is would airlines want to max out weight on their airplanes all of the time, conditions permitting, or do they try and spare them that for sake of extending life?

[Edited 2011-01-24 15:40:25]


"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
20 replies: All unread, jump to last
 
User currently offlineFlighty From United States of America, joined Apr 2007, 8403 posts, RR: 3
Reply 1, posted (3 years 6 months 3 days 20 hours ago) and read 4736 times:

Quoting c5load (Thread starter):
I guess the point of my question is would airlines want to max out weight on their airplanes all of the time, conditions permitting, or do they try and spare them that for sake of extending life?

You'll get a better professional response from our other members. But from my experience, airlines are happy to launch a flight at MTOW assuming the heavy cargo is making money. Otherwise, weight increases fuel consumption, which needs to be justified by the revenue of what is being carried. The MTOW isn't some emergency number; the airplanes are designed to perform for decades being used to the max.

The 744 is known to take off at MTOW (875,000 most often) on long-range routes, limiting its cargo load in the process. This means, they reject cargo that is above the legal capacity of the airplane, after adding the fuel. This is also known as "weight restricted."

I haven't heard too many stories about 77W or A380 being weight restricted. Maybe they do carry a lot of cargo.

Quoting c5load (Thread starter):
If airlines don't need the fuel for that particular mission, would they try and make up that weight in extra cargo, if it can fit?

Sure, if the price is right. An aircraft like A333 has a huge cargo hold. Selling that space makes $$, so long as it pays for the loading and the fuel. It's part of the business model.


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 2, posted (3 years 6 months 3 days 15 hours ago) and read 4619 times:

Quoting c5load (Thread starter):
Do airlines really try and pack fuel, cargo, and pax to reach that weight?

You don't target MTOW, you target maximum payload. For long routes, this may mean you're at MTOW because you're full of fuel and then you take as much payload as you can. For short routes, you're more likely to hit MZFW first (maximum payload), then just carry the fuel that you need for the mission.

Quoting c5load (Thread starter):
That's the only way it'll make money won't it?

You make money with full payload, and just enough fuel to get you to the destination. That may or may not be MTOW (or MZFW).

Quoting c5load (Thread starter):
If airlines don't need the fuel for that particular mission, would they try and make up that weight in extra cargo, if it can fit?

If it can fit *and* if they're haven't hit MZFW yet. If you're at MZFW, it doesn't matter if it's a 100 mile flight and the tanks are 10% full, you still can't stuff more payload on.

Quoting c5load (Thread starter):
I guess the point of my question is would airlines want to max out weight on their airplanes all of the time, conditions permitting, or do they try and spare them that for sake of extending life?

You want the most profit per cycle you can get. I'm not aware of anyone who limits weight to protect life (the airplane is certified to operate at MTOW for its design life). Almost everybody limits engine thrust to preserve engine life, but the relationship between increased thrust and decreased life is much uglier for engines than for aircraft.

Tom.


User currently offlineMir From United States of America, joined Jan 2004, 21516 posts, RR: 55
Reply 3, posted (3 years 6 months 3 days 14 hours ago) and read 4601 times:

Quoting c5load (Thread starter):
With airliners getting heavier and longer range these days, do airlines really max perform their airplanes?

I can't think of any reason not to push their aircraft to the limit. Obviously, which limit that is is going to vary from day to day and route to route. Sometimes it will be MTOW, sometimes MZFW, sometimes landing weight plus fuel burn, sometimes climb restricted weight, etc. But there's always going to be some limit, and if you can fill up to that, why wouldn't you?

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlineFlyASAGuy2005 From United States of America, joined Sep 2007, 7004 posts, RR: 11
Reply 4, posted (3 years 6 months 3 days 13 hours ago) and read 4568 times:

The CR2 does is daily, albeit horribly . Just the other day, had a flight to MLI I believe. The Max was 48 pax and 48 bags. Only issue was they were booked to 50 and ended up with 46 bags, of which 7 were heavies...


What gets measured gets done.
User currently offlineANITIX87 From United States of America, joined Mar 2005, 3299 posts, RR: 13
Reply 5, posted (3 years 6 months 3 days 1 hour ago) and read 4399 times:
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Quoting tdscanuck (Reply 2):
If it can fit *and* if they're haven't hit MZFW yet. If you're at MZFW, it doesn't matter if it's a 100 mile flight and the tanks are 10% full, you still can't stuff more payload on.

Does this have to do with max landing weight? Will MZFW always be below max landing weight? If you need 10% of the fuel, why wouldn't you be able to increase payload, other than max landing weight restrictions? Is there a fundamental concept I'm missing here?

TIS



www.stellaryear.com: Canon EOS 50D, Canon EOS 5DMkII, Sigma 50mm 1.4, Canon 24-70 2.8L II, Canon 100mm 2.8L, Canon 100-4
User currently offlineA342 From Germany, joined Jul 2005, 4680 posts, RR: 3
Reply 6, posted (3 years 6 months 3 days 1 hour ago) and read 4376 times:

Quoting ANITIX87 (Reply 5):
Will MZFW always be below max landing weight?

Yes, otherwise that would be a crappy aircraft, having to throw out passengers or cargo before landing!   

In the real world, MLW is MZFW plus at least the required fuel reserve upon landing, mostly more than that.

Quoting ANITIX87 (Reply 5):
If you need 10% of the fuel, why wouldn't you be able to increase payload, other than max landing weight restrictions?

In a nutshell, wing bending moment, which puts loads on the wing-fuselage joint. But others will abe able to explain that one far better than I can.



Exceptions confirm the rule.
User currently offlineMir From United States of America, joined Jan 2004, 21516 posts, RR: 55
Reply 7, posted (3 years 6 months 3 days ago) and read 4355 times:

Quoting ANITIX87 (Reply 5):
If you need 10% of the fuel, why wouldn't you be able to increase payload, other than max landing weight restrictions?

A342 is correct with the wing/fuselage joint loading issue. Basically, if the fuselage is too heavy, the wings will start to bend and will eventually overstress. To visualize this, put a pen or pencil in the middle of a piece of paper and then pick up the paper from the edges. You can do this without the paper bending too much. Now put something much heavier (like a cellphone) on the paper and try again. You'll notice that the paper bends a whole lot more. Same thing happens with a light fuselage vs. a heavy fuselage, and the MZFW is there to prevent too much bending moment on the wings, which would show up (since wings are more rigid than paper) as stress on the joint connecting them to the fuselage, above and beyond what the engineers designed it to handle.

This is also why, even if the airplane has fuel tanks in the fuselage, the wing tanks are always filled first - it spreads the weight out more evenly.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlineANITIX87 From United States of America, joined Mar 2005, 3299 posts, RR: 13
Reply 8, posted (3 years 6 months 2 days 23 hours ago) and read 4301 times:
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Thanks, A342 and Mir. Didn't even think about wing bending being an issue, but it's pretty obvious.

TIS



www.stellaryear.com: Canon EOS 50D, Canon EOS 5DMkII, Sigma 50mm 1.4, Canon 24-70 2.8L II, Canon 100mm 2.8L, Canon 100-4
User currently offlineYYZatcboy From Canada, joined Apr 2005, 1061 posts, RR: 0
Reply 9, posted (3 years 6 months 2 hours ago) and read 3964 times:
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Landing weight is also an issue. If I load up one of our planes with a full load of people I'll more often than not be landing weight limited before I hit MTOW unless it's a long route. (if I forget about landing weight the Chief Dispatcher will not be very impressed)


DHC1/3/4 MD11/88 L1011 A319/20/21/30 B727 735/6/7/8/9 762/3 E175/90 CRJ/700/705 CC150. J/S DH8D 736/7/8
User currently offlineGonzalo From Chile, joined Aug 2005, 1985 posts, RR: 2
Reply 10, posted (3 years 6 months 2 hours ago) and read 3958 times:

Quoting tdscanuck (Reply 2):
You make money with full payload, and just enough fuel to get you to the destination.

I think that can confuse some people... you also need fuel in case you have to divert or hold in pattern while weather improves, Go Around.... Oh... and taxiing to the gate too !!!  



80 Knots...V1...Rotate...Gear Up...DC-3 / EMB-110 / Fairchild-227 / Ab318-19-20 / B732 / B763
User currently offlineFlighty From United States of America, joined Apr 2007, 8403 posts, RR: 3
Reply 11, posted (3 years 6 months 1 hour ago) and read 3924 times:

Quoting Gonzalo (Reply 10):
you also need fuel in case you have to divert or hold in pattern while weather improves, Go Around.... Oh... and taxiing to the gate too !!!

I recently learned that going to Hawaii, an aircraft need enough fuel to make all its diversions (and go arounds etc) assuming 1 engine has failed. At the lower cruising altitude, etc. Not sure if that is more fuel than normal, but it's an interesting thought.


User currently offlineYYZatcboy From Canada, joined Apr 2005, 1061 posts, RR: 0
Reply 12, posted (3 years 6 months ago) and read 3918 times:
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we plan for 1 engine out at 10 000 ft.


DHC1/3/4 MD11/88 L1011 A319/20/21/30 B727 735/6/7/8/9 762/3 E175/90 CRJ/700/705 CC150. J/S DH8D 736/7/8
User currently offlineMir From United States of America, joined Jan 2004, 21516 posts, RR: 55
Reply 13, posted (3 years 5 months 4 weeks 1 day 22 hours ago) and read 3832 times:

Quoting Flighty (Reply 11):
I recently learned that going to Hawaii, an aircraft need enough fuel to make all its diversions (and go arounds etc) assuming 1 engine has failed. At the lower cruising altitude, etc.

Not just the driftdown altitude, but also the altitude you'd descend to in case of a pressurization failure (i.e. much lower), as YYZatcboy mentioned. And yes, it is a lot more fuel.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offline9V-SPJ From United States of America, joined Dec 2000, 749 posts, RR: 0
Reply 14, posted (3 years 5 months 3 weeks 2 hours ago) and read 3124 times:

These aircraft are optimized to operate at or close to MTOW. If they weren't they would have designed them to operate at a lower weight. To operate at or close to MTOW, the wings and fuselage need to be of appropriate strength, and this may include strengthening aspects added to the design. If you weren't going to operate at these limits, why would you add this additional strengthening (if required)?
Same with the engines, why put an insanely powerful engine on the aircraft if you aren't going to utilize the full thrust capability - mainly at takeoff and during engine out situations.
As everyone has said, payload is the key here, but sometimes, you may want to carry fuel in place of pax to reach your MTOW. In that case, economically, the fares or cargo carriage prices would be adjusted such that you are still making money on the route.

My two cents  

9V-SPJ


User currently offlineYYZatcboy From Canada, joined Apr 2005, 1061 posts, RR: 0
Reply 15, posted (3 years 5 months 2 weeks 1 day 18 hours ago) and read 2703 times:
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If you mean maximum structural takeoff weight limits that is simply not true. MTOW is affected by alot of factors not the least of which is Landing weight. I can have a 737 structurally capable of taking off at 79015kg with a MTOW for a given flight of 72000kg or lower because to take off with more weight than that would put the plane over the maximum landing weight on arrival. I guarantee that over 90% of the flights I dispatch are landing weight limited not structural takeoff weight limited.

Quoting 9V-SPJ (Reply 14):
As everyone has said, payload is the key here, but sometimes, you may want to carry fuel in place of pax to reach your MTOW.

That makes no sense to me. Why would I carry a kilo more than I have to? That's just wasting fuel and putting me closer to my landing weight limit on arrival.



DHC1/3/4 MD11/88 L1011 A319/20/21/30 B727 735/6/7/8/9 762/3 E175/90 CRJ/700/705 CC150. J/S DH8D 736/7/8
User currently offlineFlighty From United States of America, joined Apr 2007, 8403 posts, RR: 3
Reply 16, posted (3 years 5 months 2 weeks 1 day 16 hours ago) and read 2665 times:

Quoting YYZatcboy (Reply 15):
Why would I carry a kilo more than I have to? That's just wasting fuel and putting me closer to my landing weight limit on arrival.

Probably was referring to displacing cargo and leaving it behind, when it puts you over MTOW. Obviously, you won't just offload fuel to keep under the limit. Unless you were tanking extra fuel or something. But you are right, it was kind of said backwards.

That's another thing... presumably airlines do tank fuel around, and the MTOW must often figure into how much fuel they can carry.


User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 17, posted (3 years 5 months 2 weeks 1 day 14 hours ago) and read 2650 times:

Quoting YYZatcboy (Reply 15):
That makes no sense to me. Why would I carry a kilo more than I have to?

Several airlines ferry fuel on shorter segments because the cost of carrying the extra fuel is less than the extra cost of getting fuel at the outstation.

Tom.


User currently offlineYYZatcboy From Canada, joined Apr 2005, 1061 posts, RR: 0
Reply 18, posted (3 years 5 months 2 weeks 1 day 4 hours ago) and read 2597 times:
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Tom,

Yes Tankering fuel does happen, but that I would consider as a required fuel load, not putting on extra fuel for the sake of raising my TOW.



DHC1/3/4 MD11/88 L1011 A319/20/21/30 B727 735/6/7/8/9 762/3 E175/90 CRJ/700/705 CC150. J/S DH8D 736/7/8
User currently offline9V-SPJ From United States of America, joined Dec 2000, 749 posts, RR: 0
Reply 19, posted (3 years 5 months 2 weeks 3 hours ago) and read 2490 times:

Sorry for my ambiguous statement! I think I meant to say cargo, but yes, tankering fuel is also a possibility to raise TOW. SIA used to do it on the now defunct SIN-TPE-LAX leg.

9V-SPJ


User currently offlineYYZatcboy From Canada, joined Apr 2005, 1061 posts, RR: 0
Reply 20, posted (3 years 5 months 1 week 6 days 21 hours ago) and read 2440 times:
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My point still stands.

If I'm going YYZ-POP with a full load of Pax I am likely to have lots of room to reach the max takeoff (structural) weight of 79015kg, but I can only take about 1500 more kg before i hit my landing weight limit. I can take all the cargo or extra gas I want to out of YYZ because the plane can take off with it no problem, but at that point I would not be able to land in POP because I would be over the max structural landing weight limit when you factor in my reserve fuel and my alternate fuel. It is the same reason I can never carry YUL as an alternate for YYZ if i have a full load of pax, even if I tech stop in BUF because the plane cant land with that payload and still have enough gas to make it to YUL without breaking my Landing weight limit.

I'm not going to raise TOW for the sake of it because eventually it will eat into my fuel load or put me over my landing weight limit.



DHC1/3/4 MD11/88 L1011 A319/20/21/30 B727 735/6/7/8/9 762/3 E175/90 CRJ/700/705 CC150. J/S DH8D 736/7/8
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