B777 QRH Smoke Or Fumes Removal
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B777 QRH Smoke Or Fumes Removal
In the 777 QRH Smoke Or Fumes Removal checklist there is the following note:
After 30 minutes of operation at low altitude and low
cabin differential pressure, electronic equipment and
displays may fail.
Is there an official Boeing definition of low altitude and low cabin diff? I've heard a figure anecdotally but never seen anything official.
rgds.
After 30 minutes of operation at low altitude and low
cabin differential pressure, electronic equipment and
displays may fail.
Is there an official Boeing definition of low altitude and low cabin diff? I've heard a figure anecdotally but never seen anything official.
rgds.
Would depend on the outside air temperature....a big difference depending on your geographic region and time of year, compare Summer Saudi Arabia to Winter Siberia, so very difficult to define an altitude.
Place your hand on the centre console FMC area and see what the normal temp feels like. With no equip cooling it gets a lot hotter.
If you had smoke or fumes one could assume you'd be heading to the nearest suitable airport anyway. If it does happen to you then your hand will feel if it's getting hot.
If you had smoke or fumes one could assume you'd be heading to the nearest suitable airport anyway. If it does happen to you then your hand will feel if it's getting hot.
Last edited by nitpicker330; 6th Aug 2012 at 09:51.
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What I have on this subject :
QUESTION 1: The Note: “After 30 minutes of operation at low altitude and low cabin differential pressure, electronic equipment and displays may fail" in the Smoke or Fumes Removal checklist raise some questions.
a. What is understood to be low altitude?
b. When Equipment Cooling is in the override mode, smoke evacuation is Dependant on Differential Pressure, since the Cabin Differential Pressure will be reducing during the descent, ultimately to zero at landing, how would smoke be effectively cleared/evacuated from the cockpit?
BOEING RESPONSE:
RESPONSE 1a: 'Low Altitude' is not defined as any specific altitude. Rather, it pertains in general to altitudes that are lower than the normal en-route altitude. i.e., to altitudes where cabin differential pressure may be low.
RESPONSE 1b: You are correct in that without differential pressure, the smoke evacuation will not be as effective. This reduction in smoke clearing effectiveness is similar to the equipment cooling not being as effective, and therefore the note about the electronic equipment and displays may fail after 30 minutes of operation at low cabin differential pressure.
The OUTSIDE temperature does not have any effect - the temperature of the air INSIDE the aircraft is relatively constant at about 23°C. The problem is the differential pressure is low, which means that the airflow over the components is reduced. That causes the overheat condition.
a. What is understood to be low altitude?
b. When Equipment Cooling is in the override mode, smoke evacuation is Dependant on Differential Pressure, since the Cabin Differential Pressure will be reducing during the descent, ultimately to zero at landing, how would smoke be effectively cleared/evacuated from the cockpit?
BOEING RESPONSE:
RESPONSE 1a: 'Low Altitude' is not defined as any specific altitude. Rather, it pertains in general to altitudes that are lower than the normal en-route altitude. i.e., to altitudes where cabin differential pressure may be low.
RESPONSE 1b: You are correct in that without differential pressure, the smoke evacuation will not be as effective. This reduction in smoke clearing effectiveness is similar to the equipment cooling not being as effective, and therefore the note about the electronic equipment and displays may fail after 30 minutes of operation at low cabin differential pressure.
The OUTSIDE temperature does not have any effect - the temperature of the air INSIDE the aircraft is relatively constant at about 23°C. The problem is the differential pressure is low, which means that the airflow over the components is reduced. That causes the overheat condition.
