Council CA 1_5 Final

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Feb 20, 2024

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1 ARMY C-12 FUEL INDICATION FAILURE Army C-12 Fuel Indication Failure Johnathan Council Embry-Riddle Worldwide 14 January 2024

2 ARMY C-12 FUEL INDICATION FAILURE Army C-12 Fuel Indication Failure Fuel Indication System The Army C-12 is a Beechcraft King Air that has been in service in the military since 1974. It is operated by a standard crew of two pilots and can hold up to 8 passengers depending on the internal seating configuration. One of the systems on the aircraft that has had consistent issues throughout its’ operational lifespan is the fueling system. The fuel system is comprised of seven tanks per wing, each wing with two separate fueling receptacles. The fuel quantity indicating system is comprised of 16 (eight per wing) capacitive type probes. Each side independently sends fuel signals via a control module to the fuel quantity indicator located inside the cockpit. The advantage of the capacitor type system is that it has no moving parts and provides accurate readings of fuel in many high performance aircraft, however, in the C-12, it is plagued with a variety of issues and failures that yield either inaccurate fuel readings or no readings at all. Fuel Monitoring and Prediction The other system that is actively involved with measuring and tracking fuel is the integrated avionics processor system (IAPS). The IAPS measures fuel flow via the sensing unit coupled fuel supply line of the engine. This sensing unit sends data via the data control unit (DCU) to the IAPS to provide the pilot with the engine specific fuel flow indications located on the multi-function display (MFD) on the primary dash between the pilots. This information is also passed to the flight management system (FMS) on the center console for active fuel monitoring and fuel prediction calculations. When the pilot inputs total fuel measured by the fuel quantity indicating system into the FMS, the FMS will compare fuel flow values and total fuel quantity, couple it with ground speed, and then provide flight time available, range, and fuel used

3 ARMY C-12 FUEL INDICATION FAILURE values. If either fuel flow or fuel quantity is missing, the FMS will be unable to provide any of those values to the pilot. If the quantity gauge is also malfunctioning, the pilots may not have precise fuel calculations other than being able to view fuel flow against known or predicted fuel quantity. The resulting fuel management is then unprecise or entirely inaccurate altogether. System Overload (Failure) The fuel quantity sensing system and the IAPS work in concert to provide pilots detailed fuel information to facilitate mission success and/or diversionary planning and decision-making variables. As is often the case, one the of the two sensing probe control modules fails or malfunctions, meaning pilots have no fuel quantity indication for one of the wing fuel systems. This is sometimes caused by an aircraft parked outside during inclement weather that in-turn affects the control module, or it is simply a failure of the control module. There is presently at this time no checklist or guidance to address this type of failure in flight. A cognitive decision tree has been presented below to assist pilots in working through this system failure.

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4 ARMY C-12 FUEL INDICATION FAILURE Cognitive Decision-Making Tree Figure 1 A cognitive decision-making tree to assist in reducing pilot workload and human error. Note: At this time, there is no checklist or decision tree that assist pilots in dealing with fuel indication errors and failures. This cognitive decision tree is designed to address this shortcoming. Resolution While this design for a fuel quantity indicating system is typically a reliable and accurate method for monitoring fuel, it has become apparent that this design has some inherent flaws. One flaw in particular is that it has a single point of failure. Each independent wing fuel system has one control module that receives input from eight fuel probes. This single point of failure should be addressed by building in redundancy into the system. Each independent system should receive a second control module or a single control module with two separate channels that allow for a

5 ARMY C-12 FUEL INDICATION FAILURE fully functional quantity measurement in the event of a module failure or single channel failure. Another corrective action may be evaluating why inclement weather conditions have negative effects on the fuel indication system. It may be that the module position should be relocated or that the location of the module needs more effective weather sealant to protect it from the outside environment. Consideration should be given to sourcing the control module from another vendor or upgrading it all together with a more modern part or fuel monitoring system. Improving the fuel quantity parts would aid in increasing aircraft lifespan and alleviate potential pilot errors while simultaneously improving mission effectiveness and operational readiness.

6 ARMY C-12 FUEL INDICATION FAILURE Reference Department of the Army. (2020). Technical Manual: Operator’s Manual for Army C-12V/V1 . Department of the Army Headquarters .

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