Fuel Dumping - why none on some planes?

I think that's "fake news" lol. IMO that track does not represent 4 hours of flight time in 757. It looks like a few zig-zags to problem solve and run some checklists, then a few turns in a hold to get below max landing weight. If it were serious enough, you'd just land over weight and have to have an inspection for it. My guess is the reporter looked at the block out time and block in time. They probably had to wait a while for a gate as an unexpected arrival.
To answer the question: the 757's maximum take-off weight is not that much more than its maximum landing weight. Aircraft that can jettison fuel have a large difference in those numbers. Mainly wide-body aircraft...

 

I think Rick has it. If you can land just after taking off with no problems, no need to dump fuel. Different for fighters and big heavies, especially with flap/slat problems.

 

I don't have ready access to a W&B manual for a 757 but for an A320-232 MTOW=77000kg and MLW=64500kg. Assuming a burn rate of 2200kg/hr/eng in a holding pattern would require almost 3 hrs to reduce fuel. This neglects higher burn rates during TO and climb, but shows that 3hr or more on a 757 is plausible.

 

Note, too, that take-offs at MGTOW would be unusual. Usually much less.

 

Maybe on domestic short haul, although when fuel costs were quite high a few yrs ago 'tankering' was common, which probably increased the % of actual TOW weight to MTOW.

 

Part 25 AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES
Subpart E--Powerplant
Fuel System Components

Sec. 25.1001

Fuel jettisoning system.

(a) A fuel jettisoning system must be installed on each airplane unless it is shown that the airplane meets the climb requirements of Secs. 25.119 and 25.121(d) at maximum takeoff weight, less the actual or computed weight of fuel necessary for a 15-minute flight comprised of a takeoff, go-around, and landing at the airport of departure with the airplane configuration, speed, power, and thrust the same as that used in meeting the applicable takeoff, approach, and landing climb performance requirements of this Part.
(b) If a fuel jettisoning system is required it must be capable of jettisoning enough fuel within 15 minutes, starting with the weight given in paragraph (a) of this section, to enable the airplane to meet the climb requirements of Secs. 25.119 and 25.121(d), assuming that the fuel is jettisoned under the conditions, except weight, found least favorable during the flight tests prescribed in paragraph (c) of this section.
(c) Fuel jettisoning must be demonstrated beginning at maximum takeoff weight with flaps and landing gear up and in--
[(1) A power-off glide at 1.3 VSR1;]
(2) A climb at the one-engine inoperative best rate-of-climb speed, with the critical engine inoperative and the remaining engines at maximum continuous power; and
[(3) Level flight at 1.3 VSR1, if the results of the tests in the conditions specified in paragraphs (c)(1) and (2) of this section show that this condition could be critical.]
(d) During the flight tests prescribed in paragraph (c) of this section, it must be shown that--
(1) The fuel jettisoning system and its operation are free from fire hazard;
(2) The fuel discharges clear of any part of the airplane;
(3) Fuel or fumes do not enter any parts of the airplane; and
(4) The jettisoning operation does not adversely affect the controllability of the airplane.
(e) For reciprocating engine powered airplanes, means must be provided to prevent jettisoning the fuel in the tanks used for takeoff and landing below the level allowing 45 minutes flight at 75 percent maximum continuous power. However, if there is an auxiliary control independent of the main jettisoning control, the system may be designed to jettison the remaining fuel by means of the auxiliary jettisoning control.
(f) For turbine engine powered airplanes, means must be provided to prevent jettisoning the fuel in the tanks used for takeoff and landing below the level allowing climb from sea level to 10,000 feet and thereafter allowing 45 minutes cruise at a speed for maximum range. However, if there is an auxiliary control independent of the main jettisoning control, the system may be designed to jettison the remaining fuel by means of the auxiliary jettisoning control.
(g) The fuel jettisoning valve must be designed to allow flight personnel to close the valve during any part of the jettisoning operation.
(h) Unless it is shown that using any means (including flaps, slots, and slats) for changing the airflow across or around the wings does not adversely affect fuel jettisoning, there must be a placard, adjacent to the jettisoning control, to warn flight crewmembers against jettisoning fuel while the means that change the airflow are being used.
(i) The fuel jettisoning system must be designed so that any reasonably probable single malfunction in the system will not result in a hazardous condition due to unsymmetrical jettisoning of, or inability to jettison fuel.

Amdt. 25-108, Eff. 12/26/2002

 

back to the original question i cant provide answers like some here. But i would think no emrgency and therefore burn fuel instead of dump for environmental issues.

 

The overweight landing inspections would take the plane out of service for a greater length of time than it does to burn the fuel off to keep from having to do one. The 757 doesn't need a jettison system for safety reasons.

 

I remember years ago doing recurrent simulator training in a Learjet 35, which has fuel dump (called "Fuel Jettison" in Learjet-speak). The instructor commented that his last students were from Sweden, and they literally wouldn't jettison fuel in any circumstance, even in the simulator!

(At least, not for an engine failure-- maybe for a failed tiptank jetpump.)