ATR Airframe Airbleed FAULT! questions to engineers??
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ATR Airframe Airbleed FAULT! questions to engineers??
Hey guys, have an issue u may be able to answer:
In the event of airframe airbleed fault light on the pb, the cause maybe overheat in the duct before the de-ice valve OR a leak in the common airframe air duct after the isolation valve!
Checklist says to deselect the airframe airbleed pb to close the isolation valves, and as long as the engine de-ice is selected on, the de-ice valves will stay open....theory is if there is an overheat, the de-ice valve would have closed and a fault light will appear on the engine de-ice push button, therefore u can determine the side and the overheat problem.
Thats fine and makes sense! But what would u see on the panel if u did not deselect the airframe airbleed pb??? surely if the fault was due to a leak in the common manifold, NO fault light would appear in the engine de-ice system, just a fault light on airframe airbleed and airframe push buttons!
Just trying to figure out the need to de-select FIRST the airframe airbleed push button?
Any info be great IT IS DOING MY HEAD IN!!!
Just an add on: is the closing of one de-ice valve due to overheat enough to create a drop in pressure in the common air bleed manifold, therefore triggering the fault light on the airframe airbleed pb? therefore impossible to tell if the fault detected is due to low pressure created by a leak or an overheat causing a de-ice valve to close? therefore the need to deselect the airfarme airbleed p/b................
Would a leak in the manifold ALSO set the fault light on the engine de-ice push buttons? Really that is my question, because if u get no fault light there, the fault MUST be a leak in the common airgrame bleed manifold!
In the event of airframe airbleed fault light on the pb, the cause maybe overheat in the duct before the de-ice valve OR a leak in the common airframe air duct after the isolation valve!
Checklist says to deselect the airframe airbleed pb to close the isolation valves, and as long as the engine de-ice is selected on, the de-ice valves will stay open....theory is if there is an overheat, the de-ice valve would have closed and a fault light will appear on the engine de-ice push button, therefore u can determine the side and the overheat problem.
Thats fine and makes sense! But what would u see on the panel if u did not deselect the airframe airbleed pb??? surely if the fault was due to a leak in the common manifold, NO fault light would appear in the engine de-ice system, just a fault light on airframe airbleed and airframe push buttons!
Just trying to figure out the need to de-select FIRST the airframe airbleed push button?
Any info be great IT IS DOING MY HEAD IN!!!
Just an add on: is the closing of one de-ice valve due to overheat enough to create a drop in pressure in the common air bleed manifold, therefore triggering the fault light on the airframe airbleed pb? therefore impossible to tell if the fault detected is due to low pressure created by a leak or an overheat causing a de-ice valve to close? therefore the need to deselect the airfarme airbleed p/b................
Would a leak in the manifold ALSO set the fault light on the engine de-ice push buttons? Really that is my question, because if u get no fault light there, the fault MUST be a leak in the common airgrame bleed manifold!
Last edited by powdermonkey; 1st Oct 2009 at 16:24.
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Some of these valves are "Pressure Actuated" , as well as "Electrically actuated." I think the Check list is formulated to ensure that there's a remedy should one or more of these valves stay open in the event of a duct leak , so the drill calls for deselecting them electrically to ensure the valve is closed. 
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If you have an "overheat" problem which comes from air temp measured upstream of the de-ice valves or "leak" problem which comes from pressure sensors placed downstream of the de-ice valves the CCAS is activated and AFR AIR BLEED FAULT LIGHT illuminates amber.
The other lights on DE-ICE panel will stay extinguished.
In order to determine what causes the problem we need to deselect AFR AIR BLEED pb. Now, if there was an overheat problem associated ENG pb would illuminate FAULT. If no light illuminates while AFR AIR BLEED is selected off, the reason is leak or low pressure.
Thats my understanding.
The other lights on DE-ICE panel will stay extinguished.
In order to determine what causes the problem we need to deselect AFR AIR BLEED pb. Now, if there was an overheat problem associated ENG pb would illuminate FAULT. If no light illuminates while AFR AIR BLEED is selected off, the reason is leak or low pressure.
Thats my understanding.
