DISCUSSION ASSIGNMENT INSTRUCTIONS
The student will reply to the threads and the replies must be at least 250 words each. Each reply must incorporate at least one scholarly citation(s) in APA format. Any sources cited must have been published within the last five years. Acceptable sources include the most current sources you can find which likely means the Internet. Make sure to cite all facts in text.
This week we learned about different approaches to resolving a discrepancy when the general 7-step process just isn’t working out. Regardless of which technique one uses for troubleshooting they must first remember defining the problem, gathering information, and performing analysis still take place when using these other methods (Mostia, 2006, p.74). Now lets take a look at the discrepancy.
One afternoon, U.S. Coast Guard (USCG) 6003 came back from an afternoon training flight with a dreaded automatic flight control system (AFCS) discrepancy. In a certain flight regime on this particular helicopter (approach to hover) there would be an intermittent AFCS degraded caution on the Multifunction display (MFD).
The 6003 is an MH-60T helicopter, manufactured by Sikorsky and the AFCS is a very complex system, designed to assist the pilot in maneuvering and handling the helicopter, as well as many other functions. The system is composed of three major subsystem: stability augmentation system (SAS), the stabilator system, and the digital automatic flight control system (DAFCS) (U.S. G.P.O., 2012, p.121). Each subsystem operates independently of the other two subsystems but as a total system, each subsystem complements the others. The MH-60T flight manual states, “The SAS subsystem provides rate damping and short-term dynamic stability in the pitch, roll, yaw, and vertical control axes” (2012, p.131) The stabilator subsystem optimizes trim attitudes for cruise, climb, and autorotation and provides pitch stability augmentation to complement the SAS system for additional redundancy (U.S. G.P.O., 2012, p.129). The DAFCS provides short term dampening (dynamic stability) and maintains desired altitude, speed, and heading (static stability) (U.S. G.P.O., 2012, p.121).The AFCS is made up of multiple control panels, automatic flight control computer (AFCC), trim servos, boost servos, primary servos, stabilator actuators, amplifiers, sensors, potentiometers, and the list goes on and on. To help with narrowing down component issues, the AFCC generates ground bite and flight bite codes to assist in the troubleshooting. While I would love to go into every specific components purpose, we do not have enough time to completely digest the information. I will attach all associated schematics and information to help assist in this particular discrepancy.
As my team and I dove into the discrepancy, we wrote down the associated flight bite codes, and performed a ground bite to get those codes. From there we went into the maintenance manual to which led us to the computer saying we had a bad collective trim servo. So we replaced that and sent the helicopter on its test flight, in which it came back failing the approach to hover check with an intermittent AFCS degraded. This is were I need you, my fellow classmates to help me solve this repeat offender. Thank you in advance for the help.
In this week’s course reading we learned a few new methods to approach troubleshooting. For every trouble shooting situation there can be multiple methos used, it all depends on the mechanic and the type of situation found. I personally like the complex to simple method because it is easy to use and most of the time will help you quickly fine the problem. The textbook describes this system as “Involves finding the simple parts that function to make the whole. Once you find the simplest non-functioning “part,” you can evaluate the non-functioning part or, if necessary, you can start at a simple known good part and “rebuild” the system until you can find the problem”. (Mostia, 2006) As a mechanic when approaching a write up we must think what is the simplest component that may be causing this issue. In most cases the simple fix is relatively cheaper that other parts of the system. We as mechanics must complete our work in a timely manner but with respect to completing the task with safety as the number one priority. The book Aviation Maintenance Management define the word reliability as “The probability that an item will perform a required function, under specified conditions without failure, for a specified amount of time according to its intended design”.(Harry, 2013) When we work on specific components we must make sure that they are reliable to the customer.
For my write up I am going to be using a Mooney M20 with an engine issue as an example. The pilot stated that “The engine was running rough”. To the mechanic this could mean a numerous number of things could be wrong. The pilot could have bad fuel, a dead sparkplug, magnetos of time, and the list goes on. To narrow it down the mechanic take the aircraft out or an operational run. Upon the operational check being completed by the repair station they find the engine to be running completely normal. The lead mechanic gives the pilot a call to receive more information. The pilot then adds “I was coming in on my finial approach when I lost oil pressure, then my engine stuttered for a little bit. Once I was laned the engine stopped running rough”. However, when the mechanic was running the engine the oil pressure was normal. Now the mechanic can see that there is something wrong with the oil system.
The way this oil system works is quite simple. There is an oil pan that holds the excess oil in the bottom of the engine. When the aircraft starts it turns a sump which picks up oil and distributes it throughout the engine for cooling and lubricating purposes. However, this aircraft is equipped with a propeller governor. The oil is also pumped into the accessory case to lubricate the gears that are turning the magnetos, alternator, and more. These types of aircraft use the oil from the sump to control the propeller angle of attack. All the oil once used seeps back to the oil pan to be used again.