Why can't the French dump fuel?

Bob Moore wrote:

25.121(d) at maximum takeoff weight

This is how it was explained to me; an ex-member of our club that flies for
"a major" simplified it to "one-engine-out missed approach": if the plane
can do that at t/o weight, no dump system required.

This is distinct from the maximum landing weight, which involves other
factors. In an emergency, therefore, a pilot might need to make an
"overweight landing".

- Andrew

I'm sure the airlines, EPA, and everyone else would rather the fuel be
burnt as normal rather than dumped into the air and sea.


I heard that the environmental impact of dumping fuel is not as bad as
it might seem. As the volatile fuel is sprayed into the air it tends to
oxidize and the result is similar to burning it in the engine. I am not
too sure of this when considering the complex chemistry of turbofan
combustion in flight. From the combustion chamber, out the nozzle and
through the downwash behind the plane the combustion reaction
continues. Dumping fuel sprays it into turbulent air without the
initial combustion and expansion so it is likely much different. I was
a payload integration engineer in support of the NASA DC-8 (which had
the ability to dump of course) on the SUCCESS mission to fly planes
behind and around each other to sample the exhaust products and
characterize the chemistry. The pilots had to be careful not to get
caught in the tip vortex.

http://cloud1.arc.nasa.gov/success/d...60418.hil.html

In the above photo our engineering group installed the canoe sized
instrument fairing on the side of the plane just forward of the aft
service door. We also installed the pod under the forward fuselage. As
the elevator is tab powered and the fairing is in front of it, we were
crossing our fingers during the taxi test and flight test.

http://uap-www.nrl.navy.mil/dynamics...s2May1996.html

http://raf.atd.ucar.edu/~dcrogers/GRL/grl.html

http://cloud1.arc.nasa.gov/success/

James

"jbaloun" wrote:

I'm sure the airlines, EPA, and everyone else would rather the fuel be
burnt as normal rather than dumped into the air and sea.

I heard that the environmental impact of dumping fuel is not as bad as
it might seem. As the volatile fuel is sprayed into the air it tends
to oxidize and the result is similar to burning it in the engine.

Then why are gas pumps in many places fitted with systems to capture the
vapors from fueling? Why is barbeque lighter fluid banned in many
jurisdictions? Why is there a push to ban oil-based paint and thinners?

The reality is that unburned hydrocarbons are a major source of air
pollution. The occasional fuel dump will not have a huge effect on the
environment, but it is still better if the fuel is burned in a well-
maintained engine.

Robert M. Gary wrote:

Joe,
You sound like an EXCELLENT advocate for having the ability to dump
fuel too!!!

-Robert

Robert,

Why are you in such a hurry to dump fuel? Doing that starts to limit
your time / options available for trouble shooting the problem and
diverting to another airport.

The first two memory items on any emergency checklist a

1. FLY THE AIRPLANE
2. DON'T HURRY

Dumping fuel violates #2. Besides, IF you really need to land in a
hurry, the A320 can do that at any weight. These guys took off for NY
with a full load of passengers. That means that they had a lot of fuel
onboard and a heavy takeoff weight. To land at that weight would have
required a much higher landing speed. Since they had the hydraulics
(green system) turned off to the nosewheel steering system, (per
emergency checklist) this also reduced their braking ability because
this same hydraulic system also controls the #1 engine reverse, and
normal braking, i.e. antiskid assisted braking.

BJ
A320 Capt.

B. Jensen wrote:
You sound like an EXCELLENT advocate for having the ability to dump
fuel too!!!

Why are you in such a hurry to dump fuel? Doing that starts to limit
your time / options available for trouble shooting the problem and
diverting to another airport.

The first two memory items on any emergency checklist a

1. FLY THE AIRPLANE
2. DON'T HURRY

Dumping fuel violates #2. Besides, IF you really need to land in a
hurry, the A320 can do that at any weight. These guys took off for NY
with a full load of passengers. That means that they had a lot of fuel
onboard and a heavy takeoff weight. To land at that weight would have
required a much higher landing speed. Since they had the hydraulics
(green system) turned off to the nosewheel steering system, (per
emergency checklist) this also reduced their braking ability because
this same hydraulic system also controls the #1 engine reverse, and
normal braking, i.e. antiskid assisted braking.

To me it's perfectly clear, that there was no need for the JetBlue A320
to dump fuel. Burning it was a much better option. But I can still
imagine emergencies, where one cannot afford to fly around for several
hours, yet still a reduced landing weight, lower than the allowable
maximum, and less fuel onboard (the fireball thing ..) would be
desireable. Say some sort of fire or smoke developing onboard, for
example, like the swissair accident, maybe in combination with some
structural damage. I would expect that dumping fuel just before the
landing would greatly reduce the risk of a big fireball.

However, the question is of course again, how likely is an event like
this, where fuel dumping even below max landing weight would be an
advantage and what is the cost and weight for the device.

regards,
Friedrich

--
for personal email please remove 'entfernen' from my adress

"Robert M. Gary" wrote in message
oups.com...
In the case of the A320, or the 737, they can both land with a full load
of fuel.

Then why did Jet Blue fly around for 3 hours burning fuel before
landing back in LAX? It seems like if there is a real reason to want to
burn off fuel there would be a real way to get rid of the fuel. I can
dump fuel even in my Mooney.

The crew is paid by the hour?

"Robert M. Gary" wrote

Then why did Jet Blue fly around for 3 hours burning fuel before
landing back in LAX? It seems like if there is a real reason to want to
burn off fuel there would be a real way to get rid of the fuel. I can
dump fuel even in my Mooney.

The plane would be able to land at the weight that it was at, but that would
have been two negative things. One, it would have meant extra weight on the
already overstressed nose gear. Two, it would have meant a faster landing
speed, and faster speed that the nose would have been let down.
--
Jim in NC

Robert M. Gary wrote:
In the case of the A320, or the 737, they can both land with a full
load of fuel.

Then why did Jet Blue fly around for 3 hours burning fuel before
landing back in LAX? It seems like if there is a real reason to want
to burn off fuel there would be a real way to get rid of the fuel. I
can dump fuel even in my Mooney.

-Robert

They burned off the fuel to reduce weight. Less weight means a lower
approach and touchdown speed. Less weight means less mass to slow down
once they're on the ground. I would imagine they turned their autobrakes
off since, without nosewheel steering, they would need to use differential
braking for steering purposes. Minimum weight would allow them to not have
to land right at the beginning of the runway and not have to use excessive
braking to stop the aircraft within the runway length. This way they could
concentrate on a smooth touchdown and slow lowering of the nose gear.

I made an emergency landing on 25R at LAX in a 737-200 which had lost all
hydraulic power and the electrical emergency flap extension failed also. So
we had to make a manual reversion no-flap landing with emergency gear
extension. We had no nose wheel steering and used differential braking for
steering. We had to be careful with it since we only had accumulator power
for brakes and thrust reversers. We got it stopped about half way down the
runway and then were towed to our gate.

--

Darrell R. Schmidt
B-58 Hustler History: http://members.cox.net/dschmidt1/
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