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Mtow & Hot Weather  
User currently offline3holeflyer From United States of America, joined May 2008, 30 posts, RR: 0
Posted (6 years 3 months 16 hours ago) and read 2609 times:

The other day, I flew out of OAK when the temperatures were pushing 100 F, definitely warm for the Bay Area. Was on a 737, but my bag wasn't. Upon arrival in SEA, friendly staff said it would be in later (no problem for me), and that several bags were running late as they were held for later flights that were less full because of weight issues.

In adjusting the weight for a hot day, will a few bags make a difference? Is this a ramp or pilot call? Maybe the bags really got bumped for some hot cargo?

15 replies: All unread, jump to last
 
User currently offlineLeezyjet From United Kingdom, joined Oct 2001, 4041 posts, RR: 53
Reply 1, posted (6 years 3 months 16 hours ago) and read 2596 times:



Quoting 3holeflyer (Thread starter):
In adjusting the weight for a hot day, will a few bags make a difference? Is this a ramp or pilot call? Maybe the bags really got bumped for some hot cargo?

Yes it sure will. The pilot's will make the decision on a flight by flight basis based on the current weather conditions, fuel load, runway length, runway in use, wind direction etc for that particular flight.

In 99% of airlines, they have an offload priority for situations like this, and after stand-by passangers bags, then standby passengers, cargo ususally comes next, so the cargo would be offloaded way before the bags. Passenger bags are 2nd to last on the list with passengers being last.

I've been on standby before out of JNB, and been left behind even though there were 30 spare seats on the a/c because of weight restrictions due to the heat/high altitude of JNB. That's why a majority of l/hauls out of hot and high airports are at night as it is a little cooler and they can carry more weight.

 Smile



"She Rolls, 45 knots, 90, 135, nose comes up to 20 degrees, she's airborne - She flies, Concorde Flies"
User currently offlineMcdu From United States of America, joined Apr 2005, 1459 posts, RR: 17
Reply 2, posted (6 years 3 months 16 hours ago) and read 2579 times:



Quoting 3holeflyer (Thread starter):
In adjusting the weight for a hot day, will a few bags make a difference? Is this a ramp or pilot call? Maybe the bags really got bumped for some hot cargo?

Yes a few bags do make a difference. In the case of a large airline that I suspect you were riding on the decision to leave bags and or pax behind is up to the Load Planner for that flight, not the pilots. I work for a major carrier and we have a centralized load planner in ORD that makes the determination on how to accommodate the pax and bags. Normally they will not send a pax without their bag or they will attempt to. The pilots will only know that the flight is at it's max T/O wt but have little say in what is boarded. On our planned manifest it will indicate the flight might be "load restricted" due to weight but that would be our only clue. At some point after loading and before takeoff our company sends our final weight manifest to us via our ACARS printer. This is the data we use to enter into our FMC's and make sure we are under our max T/O wt. Sometimes a fluctuation can occur and we might have to burn more taxi fuel to lower our gross wt to allow for t/o but that is fairly rare.

At UAL we have the most problem with our TED configuration. With the 156 seats the airplanes it added enough extra pax weight from the original 320's to incur wt issues for both t/o and believe it or not landing.


User currently offlineMayor From United States of America, joined Mar 2008, 10370 posts, RR: 14
Reply 3, posted (6 years 3 months 16 hours ago) and read 2562 times:

They probably should have used "child weights" before they removed anything, then they can start removing standby pax & their bags, then cargo, etc. If they use a computerized weight and balance system like DL, it won't spit out a weight and data record for the pilots until the weights are under the mtow. If it was just a few bags difference, they could probably fudge on it as the figures used for a/c weights are on the conservative side.


"A committee is a group of the unprepared, appointed by the unwilling, to do the unnecessary"----Fred Allen
User currently offlineRFields5421 From United States of America, joined Jul 2007, 7607 posts, RR: 32
Reply 4, posted (6 years 3 months 16 hours ago) and read 2555 times:

Every airplane for every takeoff has a legal maximum takeoff weight.

In general, the higher the tempature - the lower the weight.

Airlines like to fly aircraft full, so the more people on the plane, the closer to MTOW the weight. At some point that extra bag crosses the line.

Yes, it's probably safe and your bag probably wouldn't cause a problem.

But there has to be a firm line somewhere - this much and NO more.


User currently offlineMcdu From United States of America, joined Apr 2005, 1459 posts, RR: 17
Reply 5, posted (6 years 3 months 16 hours ago) and read 2550 times:



Quoting Mayor (Reply 3):
They probably should have used "child weights" before they removed anything, then they can start removing standby pax & their bags, then cargo, etc.

At UAL we stopped the kid count to decrease the weight. Supposedly the Cray super computer that solves all of our problems is able to determine children on board based on the booking information. At least that is what we are being told...........


User currently offlineMayor From United States of America, joined Mar 2008, 10370 posts, RR: 14
Reply 6, posted (6 years 3 months 16 hours ago) and read 2533 times:



Quoting RFields5421 (Reply 4):
But there has to be a firm line somewhere - this much and NO more.

True, but in DL's case, you could theoretically have more weight if you were doing the figures manually, rather than let the computer do it. I believe that when DL was trying to sell the idea of the computerized weight and balance to the FAA, they had to go conservative to get them to sign off on it.



"A committee is a group of the unprepared, appointed by the unwilling, to do the unnecessary"----Fred Allen
User currently offlineOHLHD From Finland, joined Dec 2004, 3962 posts, RR: 25
Reply 7, posted (6 years 3 months 15 hours ago) and read 2524 times:

This happens sometimes in places like DOH or DXB with narrowbody aircrafts heading for Europe or so. Because of the intense heat they get heavily restricted on the MTOW although they have looonnngggg runways.  Smile

Quoting Leezyjet (Reply 1):
In 99% of airlines, they have an offload priority for situations like this, and after stand-by passengers bags, then standby passengers, cargo usually comes next, so the cargo would be offloaded way before the bags.

Correct! Baggage is actually very high on the list however I have seen airlines leaving baggage behind to get cargo to the destination. The only time cargo has higher priority is when it is express or a must-go Cargo. In these cases it is extra paid for being on board.


User currently offlinePanAm747 From United States of America, joined Feb 2004, 4242 posts, RR: 8
Reply 8, posted (6 years 3 months 15 hours ago) and read 2513 times:

As a side note, if I recall correctly, at PHX and LAS 757's were almost never weight restricted during the summer (except Hawai'i flights). A320's/A319's/737's and so on were always very carefully calculated, but I remember an America West person telling me the 757 never had any problems.

I don't know about "never", but knowing the performance characteristics of the 757, I'm likely to believe "mostly". Can someone verify this?



Pan Am:The World's Most Experienced Airline - P(oor) S(ailor's) A(irline): San Diego's Hometown Airline-Catch Our Smile!
User currently offlineMayor From United States of America, joined Mar 2008, 10370 posts, RR: 14
Reply 9, posted (6 years 3 months 15 hours ago) and read 2504 times:



Quoting OHLHD (Reply 7):
Correct! Baggage is actually very high on the list however I have seen airlines leaving baggage behind to get cargo to the destination. The only time cargo has higher priority is when it is express or a must-go Cargo. In these cases it is extra paid for being on board.

Even in DL's case, bags still have priority. When you run into a problem is when cargo is loaded first (so it's offloaded last) and then bags are loaded in front of it. If you have to pull cargo, then you've got a problem, especially if you're running up against the departure time. In some cases, I think, ramp agents just leave cargo off, if it looks like there will be a problem.
Then, quite often, the flight will leave with much weight to spare and the cargo could have gone on board.



"A committee is a group of the unprepared, appointed by the unwilling, to do the unnecessary"----Fred Allen
User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9580 posts, RR: 52
Reply 10, posted (6 years 3 months 11 hours ago) and read 2397 times:



Quoting 3holeflyer (Thread starter):
The other day, I flew out of OAK when the temperatures were pushing 100 F, definitely warm for the Bay Area. Was on a 737, but my bag wasn't. Upon arrival in SEA, friendly staff said it would be in later (no problem for me), and that several bags were running late as they were held for later flights that were less full because of weight issues.

I'm kind of surprised that a 737 had problems with MTOW while flying OAK-SEA. It isn't a very long flight and OAK has a 10,000ft runway. If for some reason they were restricted one of the 6,000ft runways then it does make sense, but I would think that a 737 would be able to make it to SEA without trouble even in 100F conditions. Was it a 737-400?



If you have never designed an airplane part before, let the real designers do the work!
User currently offlinePilotpip From United States of America, joined Sep 2003, 3150 posts, RR: 11
Reply 11, posted (6 years 3 months 3 hours ago) and read 2325 times:

OAK-SEA isn't the longest segment. It might not have been an issue of MTOW, it could have also been an issue with max landing weight.

The high/hot issue will affect aircraft in different degrees. At my old airline, the 145EPs were often weight restricted while the LRs didn't have quite as many issues due to having a higher MZFW and MTOW. I'm flying the 170 now and it rarely has issues.



DMI
User currently offlineMaverick623 From United States of America, joined Nov 2006, 5592 posts, RR: 6
Reply 12, posted (6 years 3 months 1 hour ago) and read 2310 times:



Quoting RoseFlyer (Reply 10):
OAK has a 10,000ft runway.

Not familiar with OAK, but if there are buildings near the end of the runway, you need to achieve a certain climb gradient that in the event of an engine failure after V1, you can clear said buildings with a good margin. It's why a lot of US 733s in PHX (with 11,000ft runways) are often weight restricted during the summer, even to ONT. There are elevated freeways and lots of tall buildings, and the climb performance on a 110 degree day is not that great.



"PHX is Phoenix, PDX is the other city" -777Way
User currently offlineRoseFlyer From United States of America, joined Feb 2004, 9580 posts, RR: 52
Reply 13, posted (6 years 2 months 4 weeks 1 day 18 hours ago) and read 2270 times:



Quoting Maverick623 (Reply 12):
Not familiar with OAK, but if there are buildings near the end of the runway, you need to achieve a certain climb gradient that in the event of an engine failure after V1, you can clear said buildings with a good margin.

OAK's long runway is out in the bay. It's got water on both ends, so there's no obstacles. Again, if they were having to use a short runway, then it makes sense to see weight restrictions.

Quoting Pilotpip (Reply 11):
OAK-SEA isn't the longest segment. It might not have been an issue of MTOW, it could have also been an issue with max landing weight.

High temperatures in OAK won't affect Max Landing Weight will it?



If you have never designed an airplane part before, let the real designers do the work!
User currently offlineWILCO737 From Greenland, joined Jun 2004, 8985 posts, RR: 76
Reply 14, posted (6 years 2 months 4 weeks 1 day 17 hours ago) and read 2267 times:
AIRLINERS.NET CREW
HEAD MODERATOR

On the 737 I was just once or twice TOW limited. We only did short hops and here in germany it never gets that hot.

BUT on the MD11F there were already several flights were we were restricted. MTOW is 286 tons for the MD11F and in EMA on normal days it goes down to 270 tons already or in SHJ during hot days down to 265 or so... But it is amazing how much the MD11F can carry out of an airport. EMA only 2700m runway, but 270 tons isn't bad for that pretty short runway. It's enough for an 8,5 hours flight time and still a little over 70 tons of cargo. Not too shabby eh? Big grin
I always get the laptop out and do a precalculation how much weight we can get out of this airport at these certain weather condition. So we have an idea if we can carry all the load or if we have to file a reclearance flight plane (now called decision point procedure) or if we have to land somewhere to refuel or if we leave cargo behind (which should be avoided of course).

WILCO737 (MD11F)
 airplane 



It it's not Boeing, I am not going.
User currently offlineSlamClick From United States of America, joined Nov 2003, 10062 posts, RR: 68
Reply 15, posted (6 years 2 months 4 weeks 1 day 15 hours ago) and read 2250 times:



Quoting Maverick623 (Reply 12):
if there are buildings near the end of the runway, you need to achieve a certain climb gradient that in the event of an engine failure after V1

Actually you need to be able to make the climb gradients whether there are controlling obstacles or not. In fact, it is fairly rare for a major airport to have obstacles in a departure area of one of its runways that is limiting or controlling. As has been mentioned, OAK is on fill, out over San Francisco bay, at sea level so I'm a little surprised at its being weigh restricted as described.

Quoting Maverick623 (Reply 12):
a lot of US 733s in PHX (with 11,000ft runways) are often weight restricted during the summer, even to ONT.

Again, I doubt that it is the obstacles themselves that pose the limits. Here's why.

Phoenix at a temperature of 110°F has a density altitude of around 4750 feet. Higher than Reno - standard day. It is likely that the climb gradients themselves and not the obstacles will be limiting. Gradient is 'rise over run' so to summarize, what a 737 must be able to do, as loaded is lose an engine on the ground at.above V1 and:
[I'm going to try these numbers from memory. If someone looks them up in current regs they might be slightly different but they serve to make my point]


Reach 35' by the end of the runway.
Maintain a 'positive' climb gradient during gear retraction.
Maintain a 2.4% gradient until flap retraction (that is climb 2.4 feet for every hundred feet of horizontal travel)
Maintain a 1.2 climb gradient after flap retraction.
There are a few more considerations but that'll do.

Now, as for ONT, well if PHX is 110°F then ONT is surely going to be hot as well. So, considering fuel burnoff enroute PHX-ONT you cannot take off from Phoenix at a weight greater than that which would have you arrive at ONT at a weight greater than the lesser of the following:

> Maximum structural landing gross weight or
> That weight that would permit an engine out "landing climb" (missed approach or rejected landing) with one engine inoperative at a gradient of 3.2%.

There are also enroute engine-out performance considerations that must be satisfied before takeoff too, but they are not as likely to be controlling on this flight.

So, to sum up, PHX-ONT is almost certainly 'landing weight' restricted on takeoff from PHX.
Longer flights are probably climb gradient restricted due to heavier fuel loads.



Happiness is not seeing another trite Ste. Maarten photo all week long.
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