Question regarding fuel dumping

I just saw the NOVA program about how two fully loaded 747 jumbo jets
collided on a fog-blanketed runway on the island of Tenerife, claiming
the lives of 583 people in 1977. The pilot of the KLM plane ordered
his plane to be refueled, so he rolled down the runway with 55 tons of
fuel for a flight to Las Palmas, which would take at most a half hour.
The program said it was enough fuel to get the plane back to Amsterdam,
let alone Las Palmas. It was obvious that the extra fuel fed the blaze
that killed everyone on board and prevented the plane from making a
slightly faster takeoff, which could have averted the disaster.

My question is this: When should the pilot of a commercial jet dump his
fuel in flight? He obviously wasn't going to do that and was going
to land very heavy. Under what conditions is fuel dumping necessary?

Thanks.

AJ

"AJ" wrote in message
ups.com...
My question is this: When should the pilot of a commercial jet dump his
fuel in flight? He obviously wasn't going to do that and was going
to land very heavy. Under what conditions is fuel dumping necessary?

Economics are rather important in fuel management for large aircraft... On
the one hand, carrying around that extra fuel when it is not necessary ends
up burning more fuel... On the other hand, it's quite possible that one
airport will have fuel at a price cheap enough that it is worthwhile to fuel
up there instead the endpoint of the next leg of the flight... Assuming an
aircraft has the capability to dump fuel (vs just fly around and burn it
off), one reason that they might do it is in an emergency that had them
landing at a greater weight than their maximum permissible landing weight...
For large aircraft, it is not uncommon that they will have a max takeoff
weight that is greater than their max landing weight...

AJ wrote:
Under what conditions is fuel dumping necessary?

When the plane needs to land and the takeoff weight is somewhere over
100% of the landing weight.

Grumman-581 wrote:
"AJ" wrote in message
ups.com...
My question is this: When should the pilot of a commercial jet dump his
fuel in flight? He obviously wasn't going to do that and was going
to land very heavy. Under what conditions is fuel dumping necessary?

Economics are rather important in fuel management for large aircraft... On
the one hand, carrying around that extra fuel when it is not necessary ends
up burning more fuel... On the other hand, it's quite possible that one
airport will have fuel at a price cheap enough that it is worthwhile to fuel
up there instead the endpoint of the next leg of the flight


Most airlines have matrix tables to compute the value of the cheaper
fuel vs. the increased fuel burn required to carry extra fuel (its not
free to carry extra fuel to 30,000 feet and then bring it back).
However, in this case, economics had nothing to do with it. The captain
was a training captain and did not fly the line very often. He was
upset that he was going to be late because he had already diverted. His
goal was to have a super fast turn around at his next (originally
planned) destination and then get back home ASAP. Part of his
motivation was probably to show the lowly line pilots how he was such a
super pilot and was able to avoid delays better than them, part of it
was that he didn't spend much time away from home and wanted to get
home. That also explains why he originally started his take off roll
w/o any clearance. Once the 1st officer mentioned it he stopped and got
his route clearance but then started his take off role w/o tower
clearance. He was in a mad hurry. Its also believed that because 99% of
all his take off and landings were in the simulator that the danger of
taking off w/o a clearance wasn't as intuitive to him. Trainingitis
they called it.

-Robert, CFII

Not all aircraft can dump fuel, they don't have the plumbing
installed.
Those that do cannot dump all the fuel.
Dumping done at altitude when possible and the fuel
evaporates before it gets to the ground.

§ 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 §§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 §§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 V SR1; 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.

[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as amended by
Amdt. 25-18, 33 FR 12226, Aug. 30, 1968; Amdt. 25-57, 49 FR
6848, Feb. 23, 1984; Amdt. 25-108, 67 FR 70827, Nov. 26,
2002]

"Robert M. Gary" wrote in message
ups.com...
|
| Grumman-581 wrote:
| "AJ" wrote in message
|
ups.com...
| My question is this: When should the pilot of a
commercial jet dump his
| fuel in flight? He obviously wasn't going to do that
and was going
| to land very heavy. Under what conditions is fuel
dumping necessary?
|
| Economics are rather important in fuel management for
large aircraft... On
| the one hand, carrying around that extra fuel when it is
not necessary ends
| up burning more fuel... On the other hand, it's quite
possible that one
| airport will have fuel at a price cheap enough that it
is worthwhile to fuel
| up there instead the endpoint of the next leg of the
flight
|
|
| Most airlines have matrix tables to compute the value of
the cheaper
| fuel vs. the increased fuel burn required to carry extra
fuel (its not
| free to carry extra fuel to 30,000 feet and then bring it
back).
| However, in this case, economics had nothing to do with
it. The captain
| was a training captain and did not fly the line very
often. He was
| upset that he was going to be late because he had already
diverted. His
| goal was to have a super fast turn around at his next
(originally
| planned) destination and then get back home ASAP. Part of
his
| motivation was probably to show the lowly line pilots how
he was such a
| super pilot and was able to avoid delays better than them,
part of it
| was that he didn't spend much time away from home and
wanted to get
| home. That also explains why he originally started his
take off roll
| w/o any clearance. Once the 1st officer mentioned it he
stopped and got
| his route clearance but then started his take off role w/o
tower
| clearance. He was in a mad hurry. Its also believed that
because 99% of
| all his take off and landings were in the simulator that
the danger of
| taking off w/o a clearance wasn't as intuitive to him.
Trainingitis
| they called it.
|
| -Robert, CFII
|