tag:blogger.com,1999:blog-71692133175997794162024-03-08T08:50:48.064-08:00General Aviation MaintenanceGeneral Aviation Maintenance information, General Aviation Maintenance Help and InfoGeneral Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.comBlogger18125tag:blogger.com,1999:blog-7169213317599779416.post-14011668935480323752009-10-28T18:07:00.000-07:002009-10-28T19:24:23.184-07:00The FAA recently mandated that many circuit breaker switches were defective and must be replaced within a certain amount of time. Problem #1-there were no circuit breaker switches available: Problem #2-the manufacturer of the aircraft was not going to pay for the switches replacement: Problem #3-problem #1 could be alleviated by a General Aviation Maintenance technician with an Inspection Authorization by filling out a lot of paperwork and submitting it to two divisions of the FAA: Problem #4-the owner of the aircraft had to pay for the technician's time to apply for the AMOC (Alternate Means of Compliance) compliance paperwork to allow the aircraft to continue to fly until the switches became available.<br /><br />The FAA method of mandating compliance is through Airworthiness Directives (AD's). FAR 39 is the regulation that describes AD's (see http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=674341c1d150e72204d368fdd89db006&tpl=/ecfrbrowse/Title14/14cfr39_main_02.tpl) for the actual rule. The FAR is relatively simple in scope but the data that is associated with it is very extensive.<br /><br />AD's are issued because a problem has been discovered in an aviation product that affects safety or airworthiness of that product. The product may be an aircraft, an engine, a propeller, an appliance or any part of these items. The circuit breaker switches in paragraph 1 of this blog were found to cause smoke in the cockpit of a few aircraft and after an investigation, there were many circuit breakers made the same way that possibly could cause the same problem. In order to prevent this from happening again, the FAA issued an Airworthiness Directive mandating replacement. Another recent example that was prominent in the news was the grounding of many airline aircraft until wiring was inspected and deemed to be airworthy.<br /><br />General Aviation Maintenance technicians find many items affecting safety or airworthiness during their normal duties. If a technician feels that the item is not an isolated discrepancy, but is of a recurring nature, the FAA requests that this item is reported to them through a system know as Service Difficulty Reports (SDR's). The FAA builds a data base of SDR's, analyzes them and if necessary will issue an AD to mandate corrective action. An AD also may be issued from findings from an accident or from a Service Bulletin issued by the manufacturer of a product.<br /><br />When performing certain maintenance on an aircraft, the general aviation maintenance technician will check for applicability or compliance with airworthiness directives. Something as simple as an oil change on an engine may be complicated by the requirements of an AD. One AD requires inspection of an oil filter adapter for looseness or leakage every time the oil filter is removed. Another AD requires inspection of the oil suction screen and servicing the engine with a special anti-scuff additive. Not complying with such simple AD's causes the technician and the aircraft owner/operator to be in violation of Federal Law.<br /><br />Some AD's are as simple as changing an engine induction air filter every 500 hours time in service and some are as complicated as installing major structure to reinforce wing main spars.<br /><br />AD's for aircraft, engines and propellers are usually relatively easy to research. The applicablilty section of the AD will list the model numbers and serial numbers of the affected products and the compliance section will describe what has to be done.<br /><br />Appliance airworthiness directives give the general aviation maintenance technicians many problems. First-the aircraft must be inspected to determine if the affected product is installed; second-the product part number, model number, serial number and more recently the software version must be recorded; third-the aircraft records must be checked to see if the AD has been complied with on this product and if there are recurring compliance items due. General Aviation Aircraft maintenance records are not always kept up to date and this whole process can take quite a bit of time. Appliance items include such things as: circuit breakers, strobe light flashtubes; fire extinguishers; magnetos; ignition switches; combustion heaters; autopilots; tires; hoses; turbochargers; etc.<br /><br />Airworthiness Directives are an efficient method of keeping the fleet safe to fly.General Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.com0tag:blogger.com,1999:blog-7169213317599779416.post-82177535632314893312009-10-19T17:01:00.000-07:002009-10-19T18:35:05.362-07:00The battery in a general aviation aircraft serves three main purposes. First, it is used to crank the engine until it starts; second, it is used as emergency electrical power in case the alternator or generator system fails and third, it is used to filter out noise from the electrical system. The first two purposes are pretty clear, but the third is not. Until recently, most general aviation aircraft were fabricated from aluminum that is riveted together. The electrical system uses this aluminum as a return path for many of the systems in the aircraft. (no sense running an extra wire for the return current when an excellent conductor is already in place-this saves weight and gives the aircraft additional usable payload).There are electrons travelling in many different directions during a normal flight as different electrical systems are used. The electrical engineering reasons are not clear to me, but I know a battery helps filter out much of the "noise" created by the electrical system. If there is an unusual noise in the radios, many times it is an alternator with a diode going bad, a magneto generating RFI (radio frequency interference) or an ignition lead that has broken radio shielding. If nothing is found wrong with the alternator, magnetos or ignition wires, many times changing the aircraft battery will eliminate any noise in the radios. Occasionally, troubleshooting an electrical problem can be very frustrating and time consuming. The general aviation maintenance technician receives training in electrical systems, but sometimes intuition and experience are the only way to determine the problem.<br /><br />Twelve volts? Fourteen volts? Twenty four volts? Twenty eight volts? There are people that call a general aviation aircraft electrical system 12 volts and the same system is called 14 volts by other people. They are both correct because when the alternator is not on line, the battery is operating at 12 volts. As soon as the alternator is on line, the system shifts to 14 volts in order to charge the battery and make sure it is ready in case of an alternator failure. The same relationship occurs when the system uses a 24 volt battery. The 24/28 volt system is used because the higher voltage allows less current to do the same job. If less current is required, wire sizes can be reduced and aircraft total empty weight is also reduced.<br />Don't apply the incorrect voltage on the system-12 for 24 (or) 24 for 12. Motors, light bulbs, electronics, etc. are designed to work properly and for a long time using the correct voltage, but will not work or burn out quickly using the wrong volts.<br /><br />Checking for correct bonding between components is part of the general aviation maintenance technician's responsibilities. Some aircraft designs incorporate a position light on the rudder. The rudder is designed to move on hinges. If a bonding wire is not connected between the airframe and the rudder, the hinge will not provide a good path for electricity and the position light may not operate properly.<br /><br />The engine of a general aviation aircraft is mounted on rubber shock mounts to reduce vibrations. If there is no bonding wire or the bonding wire is defective between the engine and the airframe, the engine will be effectively electrically isolated from the aircraft. Probes for engine gauges may not have a complete return path and may not indicate correctly. The engine starter uses a lot of current to crank over the engine. If the bonding wire is absent or deteriorated the current may try to find another path. There are reports of a small copper tube full of fuel used to prime the engine had carried the full starter current, burst and caught fire.<br /><br />Radio systems often use a seperate ground system to isolate them from the main aircraft electrical system. All this means is that the radio system uses another wire to complete its circuits, rather than using the airframe structure.<br /><br />Newly designed aircraft are becomming more and more an electrical machine. The general aviation aircraft technician requires continual training to "keep up" with the engineers. An update for the radio package including GPS, Autopilot, XM weather, collison and terrain avoidance, traffic alerts, synthetic vision, etc. using a laptop computer may take up to two hours. Better have an external power supply connected to keep from running down the aircraft battery.General Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.com0tag:blogger.com,1999:blog-7169213317599779416.post-32176484578189490042009-10-16T18:37:00.000-07:002009-10-16T20:02:49.807-07:00When a person decides to buy a general aviation aircraft it is a very good idea to get a "prebuy" done before any money changes hands. The "prebuy" is one of the duties of the general aviation maintenance technician, although the technician is putting his or her neck way out on the line whenever accomplishing this task. The seller of the aircraft usually believes that the machine is in perfect condition and the buyer of the aircraft wants any discrepancies found in order to negotiate a better price. The general aviation maintenance technician's customer is the buyer and is charged to find any problems that exist or may exist in the near future.<br /><br />We do not identify this as an inspection, as the FAA has no definition of a "prebuy inspection". There are annual inspections, 100 hour inspections, progressive inspections, 50 hour inspections but no prebuy inspection. There have been litigations against general aviation maintenance technicians for performing a prebuy inspection and missing something that showed up at a later date after the aircraft was purchased that cost the new owner more money than he expected. The prebuy is an abbreviated "lookover" of the aircraft and usually the buyer & seller are anxious to have the results quickly. There is a lot of pressure on the general aviation maintenance technician. The process is identified as a "prepurchase evaluation" since there is no published definition that can be used in a lawsuit. The best way to ensure an aircraft is airworthy is to accomplish an annual inspection and repair any unairworthy items. <br /><br />We start the "prebuy" by walking around the aircraft and noting anything that is unusual: deteriorated paint, foggy windows, wrinkles in flight controls, hail damage, stange patches, torn or worn upholstery, etc. Next step is to run the engine to check the engine, radios and instruments operation. A cylinders compression test will give an indication of how strong the engine is and check for cracks, piston rings condition, exhaust and intake valves condition. The oil filter is removed, cut open and visually inspected for signs of oil contamination. With experience, much can be identified by what is in an oil filter-aluminum, brass, iron, carbon all tell a story of what is happening inside of the motor. Usually by now, one can tell if the "prebuy" should continue. If too many problems have been seen at this point, it is better to stop, tell the buyer that this is going to be a "project" airplane and to find another aircraft to evaluate. We have had to do this many times. The buyer thanks us and the seller condemns us for being too picky.<br /><br />If the aircraft looks promising, the engine is visually checked for leaks, chafes, controls rigging, exhaust leaks, etc. The airframe is checked for fuel leaks, hydraulic leaks, lights are checked along with other systems such as pitot heat, stall warning, etc. Tires and brakes are looked at for wear. If the landing gear is retractable, the aircraft is jacked and the landing gear operation is checked. Flight controls hinges are checked for excessive wear and controls movement is checked. Key inspection panels are removed for evaluation of structure for internal corrosion.<br /><br />Instruments faces and indicators will be looked at and under the instrument panel will be checked for any obvious defects. Is there any corrosion around the aircraft battery and battery box? Do ventilation and avionics cooling fans operate normally? Does the magnetic compass have any air inside and is the deviation card current? Are the Pilot's Operating Handbook, Airworthiness & Registration Certificates present? Do the brake master cylinders have any leaks?<br /><br />The aircraft records are checked to determine if there is any record of major repairs that have been made (damage history), is the total time of the aircraft, engine and propeller correct and are all of the applicable Airworthiness Directives current? If any modifications have been made to the aircraft, were they properly documented with appropriate weight & balance calculations?<br /><br />The annual inspection includes all of the items described above and is much more detailed in scope and detail. Due to time and money constraints, an annual inspection is not normally complied with as a prepurchase evaluation although the buyer often requests the "prebuy" be extended into a full annual inspection if he decides to purchase the aircraft.<br /><br />Once the evaluation is complete, both the buyer and seller are normally informed of the results. The buyer will undoubtly want a dollar amount to repair any "airworthy" discrepancies. The buyer then takes this dollar amount to the seller for price negotiations. <br /><br />The general aviation maintenance technician must stress to the buyer that there are no guarantees as to the results of the prepurchase evaluation as a complete inspection has not been performed. An experienced technician can normally tell if a particular aircraft is a "good one" pretty quickly. Buying a general aviation aircraft is usually an emotional event, especially for a person who just got his pilot's license. There have been people that have disregarded our advice, purchased an inferior aircraft and their wallets have suffered as a consequence.General Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.com0tag:blogger.com,1999:blog-7169213317599779416.post-68911701557880922572009-10-14T17:06:00.000-07:002009-10-14T18:25:38.133-07:00The general aviation maintenance technician gets the chance to see how different aircraft manufacturers solve the same problem in different ways. Every aircraft has to be controlled in flight and the laws of aerodynamics generally dictate the way the aircraft is moved in pitch, roll and yaw. Conventional controls are elevator for pitch, ailerons for roll and rudder for yaw. Some aircraft use a stabilator in place of an elevator for pitch control. <br /><br />The interesting part of the controls is how the input from the pilot is transferred to the control surfaces. The controls must be similar in each type of aircraft to allow a pilot to move freely between each and still be able to make the aircraft move at his will.<br /><br />One solution is to use flexible stranded wires called control cables that are routed from the pilot control yoke or control stick to the proper control using pulleys as necessary to change direction of the cables. The system must be "closed" to allow the control surfaces to move in two directions. To roll the aircraft right, the control wheel is turned to the right or the stick is moved to the right. The wheel or stick movement pulls on the proper cables, the right aileron moves up to spoil some lift, the left aileron moves down to increase lift and the aircraft rolls to the right. The second control cable for each aileron allows the system to a complete circuit and also allows the pilot to feel the control pressures. The control cables normally do not connect directly to the control surface. The cables are attached to a bellcrank which pivots and changes direction of the applied force. The change of direction in force is transferred to the control surface by use of a push-pull rod. It sounds complicated, but in reality is very simple and reliable. Part of the general aviation maintenance techinicians job is to ensure the control cables tension is correct, there is no chafing of the cables, there is no corrosion on the cables, and the rigging of the controls is correct.<br /><br />The elevator or stabilator control system operates the same way as the ailerons. When the control yoke or stick is pulled back, the elevator moves up and the nose of the aircraft pitches up. The ailerons and elevators can be moved at the same time to allow the pilot to control the pitch and roll in any way desired. <br /><br />The rudder is normally controlled by the pilot's feet and the control cables serve the same purpose as the ailerons and elevator. When the right pedal is pushed forward, the rudder moves to the right and the nose of the aircraft yaws right.<br /><br />During maneuvers, especially during landing in a gusty crosswind, all of the controls are in a constant movement dance to bring the aircraft to a smooth completion of the flight. Good thing the general aviation maintenance technician has everything rigged correctly.<br /><br />Another method of transferring the pilot control input to the control surfaces is by push-pull tubes with a swiveling "rod-end" attached to the ends of the tube. There may be several rods throughout the aircraft depending on the size of the aircraft. If there is a change of direction necessary, a bellcrank is used with another rod attached to the other side of the bellcrank. Using a push-pull type of control system has the advantage of not requiring a "return system" as the control rods can either push or pull the control surface. A control cable is not very efficient when you try to push on it. Its almost like trying to push a car with a chain. Push-pull tubes must also be checked for corrosion, chafing and rigging just like control cables. It is important to keep the rod-ends properly lubricated to prevent seizing and possible breakage.<br /><br />Another type control on an aircraft is a trim tab. The trim tab changes the aerodynamics of the primary flight control to compensate for changes that occur during a flight. As fuel is used the weight and balance of the aircraft may change and in order to fly level the force of the elevator must be changed. To reduce pilot fatigue, the trim tab can be moved to allow the aircraft to fly level again without any input from the pilot. Quite often the trim tab actuator is a jackscrew that will move the tab to the proper position determined by the pilot. The jackscrew can be moved by control cables, torque tubes similar to push-pull tubes or electrical servos. <br /><br />All of this sounds so complicated when written down, but the systems are really very simple and elegant in design. The aerodynamics of flight is complicated but the engineers at the different aircraft manufacturers obviously have a good understanding because these aircraft fly so well and can be controlled so easily. The general aviation maintenance technician keeps the systems operating correctly and ensures that the pilot has control of the aircraft.General Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.com0tag:blogger.com,1999:blog-7169213317599779416.post-89257896866889530462009-10-11T19:14:00.000-07:002009-10-11T20:30:28.120-07:00"Wonder whats going on at work today" often is the thought of the general aviation maintenance technician on Monday's drive to work. "Everything is normal so far" as the time card is punched in and filled out. The weekly time sheet for work performed is also filled out-"good mornings" to all are passed around and then the supervisor is found. Assignment is taken to service the engine on Nxxxx for the 100 hour inspection. Time to roll the toolbox into position and get started. First thing to do is check the paperwork to see what has been done already. The checklist shows that all items are still open and need to be done. (don't want to change the oil filter twice). <br /><br />Going down the checklist, the parts that will be used are gathered together all at once to prevent many trips to the parts room. Oil filter, air filter, oil, suction screen gasket, carburetor screen gasket, spark plug gaskets, etc. are all brought to the airplane and the work begins. Removing the filter using the proper drain trough to keep from making an oily mess, cutting it open for visual inspection, lubing the new filter gasket, installing the filter and safeting the filter all take about 0.6 hours. Initial the checklist indicating completion of the item, record the time to do the work, sign out the parts used and on to the next item.<br /><br />The morning goes on normally as the engine servicing is completed: oil suction screen is inspected, cleaned, reinstalled and saftied; engine is serviced with oil (every general aviation maintenance technician has left the drain plug open at least once in his career and wondered why the oil is going on the hangar floor when it is being put in the engine); change or service the induction air filter; drain the carburetor bowl and resafety the plug; check the magnetos timing; inspect and clean the carburetor or fuel controller inlet screen; clean, gap, test, rotate & reinstall all of the spark plugs; dress nicks from the propeller blades & paint the face black; lube exhaust system slip joints; clean the engine and lube all of the engine controls. Before you know it, its time for lunch already. It has been a good morning-nothing unusual was found with the engine and "chatter" about the weekend football games with co-workers who are working on other parts of the airplane has been interesting.<br /><br />A half hour for lunch-leftover meatloaf from Saturday's dinner-also goes by quickly with more talk about everyone's favorite football team. (nobody here won the airport weekly pool)<br /><br />Assignment after lunch is to repair the discrepancy items found by the inspector of this aircraft. (It was not this technician's turn to accomplish this 100 hour inspection). Change a leaking gasket for the intake port, repair a cracked air baffle, change the starter bendix drive, clear a few chafes, replace a cracked rubber grommet for the mixture control cable, etc. are all of the typical items done by the general aviation maintenace technician. This type of servicing and repairs of minor items keeps the engine in "good shape" and minimizes the down time in-between inspections. Another way to maintain the aircraft is "break/fix" but I do not agree with this concept. My philosophy has always been to do preventative maintenance. Pilots expect the aircraft to perform as the Pilots Operating Handbook says it will and a leaking intake port gasket may cause the engine to not perform to "book specs". The worn starter bendix drive may fail at an airport that does not have a mechanic to make a repair and the purpose of flying an airplane is defeated as the pilot is now a driver of a rental car to return home.<br /><br />It is not uncommon to be interrupted during ones work day to accomplish other tasks. Airplanes need to be moved in and out of the hangar, airplanes stopping for gas may have a leaking fuel drain valve that needs to be fixed, another technician may need some help riveting and who knows what else. It is important to use a checklist to keep track of what you have done due to the possibility of interruptions. <br /><br />All during the day, the work that is done is described by writing a brief narrative on the work order, the parts are recorded and the labor is also recorded to allow proper billing. This type of record keeping is important not only for billing the customer but results in a legal document that may be reviewed by the FAA during an audit.<br /><br />It has been another good day and it feels like the airways will be safer because of my work. See http://www.pama.org/content.asp?contentid=160 for the Aircraft Mechanics Creed that I ascribe to.General Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.com0tag:blogger.com,1999:blog-7169213317599779416.post-87969375471173518172009-10-10T03:59:00.000-07:002009-10-10T05:17:50.147-07:00Aluminum, steel, magnesium, copper and lead are the types of metals most commonly found in general aviation aircraft. These metals in their pure form are not strong enough to meet the loads of an aircraft in flight therefore metals are combined into alloys to achieve the strength and flexibility necessary to build a light (not heavy) and strong machine that will last a long time.<br /><br />These aircraft metals chemically want to return to their natural state and when combined with oxygen will start doing just that. One of the tasks of the general aviation maintenance technician is to prevent the metals from returning to their natural state which is called corrosion control. I have not kept track of how much of our job is due to corrosion but I feel it is about 1/3 of the total work we have to do.<br /><br />Corrosion is a complicated subject and cannot be completely described in a short article such as this one. For further information, an excellent source can be found at faa.gov-regulations & guidelines-advisory circulars-AC 43.13-1B Acceptable Methods, Techniques and Practices - Aircraft Inspection and Repair-Chapter 6. This Handbook is considered the general aviation maintenance technicians "bible".<br /><br />If a scratch happens in the protective paint surface on the aircraft, it not only detracts from the appearance of the aircraft, it allows oxygen to gain access to the underlying metal. The oxygen can then begin to combine with the metal in a process called oxidiation and the corrosion begins. Aluminum and magnesium start to show a white powder and steel will have a "rusty" colored powder as the corrosion progresses. "Rust" and "corrosion" sometimes are considered to be all inclusive for all metals but that is not technically correct. Rust is ferrous oxide and comes from steel. I don't intend on getting into the chemical processes of corrosion as I am not a chemist and don't understand all of what is happening. Our training as a general aviation maintenance technician allows us to stop and prevent corrosion.<br /><br />To repair a scratch through the paint, the affected area would be sanded to remove any visible signs of corrosion, be treated with an etch (we use Alumiprep), be treated with a chemical conversion product (Alodine), primed (zinc phosphate) and then painted to match the original paint scheme. The difficult part is to match the paint. Paint colors fade and fresh paint does not come in a "faded" version. Many times corrosion will occur in places that include decoritive different color stripes and that complicates the touch-up.<br /><br />Where two different types of metals make contact is another place where corrosion is often found. Many general aviation aircraft have a step that is attached to the side of the fuselage to assist in entering and exiting the aircraft. This step is often made of steel. The steel step is bolted onto the aluminum fuselage with steel bolts (cadmium plated) and on the inside of the fuselage is a steel doubler which is secured to the main structure to support the weight of the person using the step. These parts are all treated when the aircraft is manufactured but after time and useage the treatment will deteriorate. Part of our job is to make sure there is no dis-similar metal corrosion forming. If caught early, the repair is relatively simple. If caught too late, the step could fail and a person may be injured. I have spoken to a person who was on crutches for several weeks due to a broken leg caused by a step failure. Engines are often supported by a similar steel doubler behind a galvanized steel firewall. Corrosion in this area-although very rare-could have much worse consequences than an entrance step failure.<br /><br />Most general aviation aircraft use lead/acid type of batteries for starting the engine and for emergency power in case the charging system fails. Corrosion around the battery is very common. The battery is contained in a "box" or has its own cover. The box is vented to the outside atmosphere and has a drain for cleaning that protrudes outside of the aircraft. The battery is vented by two tubes that are exposed to air flowing past a flying aircraft where the ends are cut at an angle. One tube forces air through the box and one tube sucks air from the box to remove the hydrogen gas produced by the battery. Most aircraft manufacturers recommend servicing the battery and checking for corrosion every 30 days.<br /><br />Lead weights are used to provide proper balance for flight control surfaces to prevent aerodynamic flutter. These weights are attached to the aluminum using aluminum rivets or steel bolts and the dis-similar metals may cause corrosion. <br /><br />Several products are available to coat metals to slow down the corrosion process but nature wants the metal to return to its original form. This will keep the general aviation maintenance technician busy as long as there are metal airplanes flying. Many aircraft are now constructed of "composites" which are man-made materials such as fiberglass, kevlar and carbon fibers. These materials also have their own special problems which will be addressed here at a later date.General Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.com0tag:blogger.com,1999:blog-7169213317599779416.post-4350542370427156192009-10-08T01:58:00.000-07:002009-10-08T03:19:43.876-07:00Laying on the floor, looking straight up with your head tightly against the rudder pedals is a common position for the general aviation maintenance technician. Some of these small aircraft make this a very uncomfortable way the human body has to be distorted in order to accomplish the task at hand. Some other aircraft make it appear that the technician is stretched out in a bed and is asleep. There are many reasons for having to access this area of the aircraft. Most pilot actions are done at the "instrument panel". All of the flight instruments, engine instrumentation, avionics controls & displays, cabin temperature controls, and flight controls (some aircraft have the elevator and ailerons controls either emenating from the floor or are "coming out" of the side upholstery as "sticks")and engine controls are in this confined area for easy access for either pilot. <br /><br />Every 24 calendar months, if an aircraft is to be used during Instrument Flight Rules(IFR), the altimeter and static system must be tested for leaks and operation per FAR 91.411. The altimeter, airspeed indicator and vertical speed indicator are the instruments that use the static system in all basic IFR aircraft. The newer aircraft have systems that also need to sense static air such as Air Data Computers and Autopilot Altitude Hold Chambers. Static air is air pressure that is sensed outside of the aircraft at "static ports" that is still or not moving air and is measured perpendicular to the surface of the aircraft. As an aircraft changes altitude the air pressure the aircraft is flying through is constantly changing and the instruments sense this change in air pressure to determine how high the aircraft is flying, how fast the aircraft is flying and how fast the aircraft is moving vertically. This is an over simplified explaination of the system and is used here only to explain why some access is necessary "behind the instrument panel" for the general aviation maintenance technician. <br /><br />Every aircraft is different from another aircraft. An owner may choose to install new equipment such as an engine monitor. This instrument is installed in a convient place in the instrument panel and looks very neat from the pilot perspective. To the general aviation maintenance technician "behind the instrument panel", the instrument has taken up more of the limited space, the wire bundle has to be routed around all of the existing components, a fuse or circuit breaker must be installed, etc. Depending how many pieces of extra equipment and how well these pieces of equipment were installed determines how much access room there is to remove an altimeter to do the required 2 year tests. An owner may ask "how come it took so long to do my tests?" and the reason may be because the altimeter may not even be able to be seen without removing several other units.<br /><br />Engine control cables, oil pressure tubes, fuel pressure tubes, manifold pressure tubes, power wires, vacuum system hoses, static system plumbing, pitot system plumbing, wire bundles, avionics cooling air hoses, heater ducts, defroster ducts, flight controls sytems, etc. all have to be secured "behind the instrument panel" to prevent chafing and to allow the flight control mechanisms to move freely.<br /><br />After being frustrated by trying to remove a piece of equipment for service or repair, a general aviation maintenance technician learns how to install new equipment with forsight. By making a hose a little bit longer, the instrument suction gauge can be unscrewed from the panel, lowered to below the panel and the hose clamps can be accessed much easier than trying to reach up past all of the other items and blindly using ones finger tips to remove the clamps. An extra two inches of wire is easily secured out of the way but that extra 2 inches of wire may allow an EGT gauge to be replaced in 10 minutes rather than one hour.<br /><br />Modern aircraft have been designed to reduce the clutter "behind the instrument panel". Aircaft designed with "all electric" systems have eliminated the plumbing required for air driven gyros. Increasing aircraft buss system voltage from 14 volts to 28 volts has reduced the size of wires. Flat screen instruments may be two inches thick compared to some instruments that are 12 inches long. Remotely mounted gyros free up a lot of space. All of this makes it easier physically for service but requires a lot of new training for the general aviation maintenance techinicain to learn the new digital age systems.General Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.com0tag:blogger.com,1999:blog-7169213317599779416.post-6687791428688987442009-10-06T16:10:00.000-07:002009-10-06T17:16:29.282-07:00"Why is your nose bleeding" seemed like a simple question due to the amount of blood on the shop towel. The answer was revealed when the shop towel was taken away from the face and a piece of safety wire could be seen entering the outside of the nose and protruding from the inside of the nose. A trip to the nearest med clinic quickly started the healing process but a tough lesson was learned: don't pull so hard on the safety wire pliers and don't pull them towards your face. This did not happen to me personally but I have had the wire break and the pliers hit me in the face. The pliers are never pulled with my face in the way anymore.<br /><br />Safety wire? It is a thin, usually stainless steel, wire that the general aviation maintenance technician is trained to use to prevent components vibrating loose on an aircraft. The wire is twisted either by hand or by a special pair of pliers, one end is attached to a non-moving part and the other end is connected to the component that possibly could vibrate loose. <br /><br />Take an oil filter for example-the filter is very similar externally to a car filter except for 4 small tabs with holes at the wrenching end. A length of safety wire is passed through a hole in the engine, the wire is pulled back on itself, the wire is twisted together until it reaches a tab on the oil filter and then twisted again past the tab. The safety wire is cut off about one inch past the tab and bent back to form a "pigtail". I have never seen an aircraft oil filter come loose in 35 years of general aviation aircraft maintenance. I have seen blood from body parts from improperly secured sharp pigtails.<br /><br />There are many techniques to prevent unwanted loosening of components on an aircraft. Simple lockwashers used under nuts and bolt heads ("starlock" type lockwashers should never be reused as the locking feature is destroyed as part of its locking design) are often used. A cotter pin passes through a hole in the end of a bolt and through a "castleated" nut to maintain the proper torque. Thin pieces of metal (locktabs) that can be used as a washer can be bent over the bolt head and the other end bent over an unmovable part to prevent rotation. Nuts may have a fiber or reduced diameter metal section that the bolt threads pass through and are squeezed in place stop any movement. There are many more different types of undesired rotation prevention devices, but the important thing to take away from this is the concept of preventing things from coming apart on the general aviation aircraft until a person wants to take it apart intentionally. Race cars use similar techniques to keep everything together during a race.<br /><br />Every part on a general aviation aircraft must be in compliance with FAA standards. Even a simple flat washer must have approval. Normally hardware will meet a Military Specification. Hardware from the local home center should never be used on an aircraft as it does not meet the strength requirements and size tolerances specified by the FAA. FAR Part 21-Certification of Products and Parts specifies the requirements for all parts on an aircraft. (see faa.gov on the web for more detailed information) During general aviation maintenance over the years, we have seen many parts that did not belong on an airplane: garden hose in the engine compartment for an instrument vacuum system-should be MIL-H-6000 hose; welding machine cabling for starter wires-should be Mil Spec type wire; lawnmower choke cable used for engine controls-should be aircraft manufacturer designed cable and many more examples. I hope these parts were not installed by a certified general aviation maintenance technician but by an uninformed, well meaning aircraft owner.<br /><br />To keep the general aviation aircraft safe to fly takes a lot of attention to small details and that is part of our job.General Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.com0tag:blogger.com,1999:blog-7169213317599779416.post-16271339217429591072009-10-04T16:45:00.000-07:002009-10-04T18:31:25.633-07:00Every general aviation, FAR Part 91, aircraft has to have an Annual or Progressive Inspection every 12 calendar months. The Progressive Inspection is used for aircraft that fly more than 200 hours every year and will not be addressed at this time. The Annual Inspection must be accomplished by an FAA certified mechanic holding an Inspection Authorization. The manufacturer of the aircraft and an FAA Certified Repair Station may also perform the Annual Inspection. The inspection must be done in accordance with FAR 43 Appendix D-Scope and Detail of an Annual or 100 hour Inspection. The 100 hour inspection is identical to the Annual Inspection but can be done by an Airframe and Powerplant (A&P) Mechanic. More about the 100 Hour Inspection at a later date. Now that we have all of the requirements listed, lets see what it takes to do an inspection on a typical single engine airplane.<br /><br />After gathering the paperwork together(always the paperwork!) and doing a walk-a-round, the engine is started and warmed up. During the warmup, the aircraft is taxied to a safe place, systems are checked for operation, instruments are checked, radios are checked, windows are checked for minute cracks called crazing and on and on.<br /><br />When the engine is warm enough, sometimes up to 20 minutes in the winter, it is run<br />to maximum power to check the tachometer, oil pressure, oil temperature, instrument air system pressure(vacuum), alternator, fuel pressure and on and on.<br /><br />The aircraft is towed (or pushed) into the hangar where the work begins. First the engine cowling is removed enough to gain access to the cylinders where a compression test is done to assess cylinders leakage. This tests the cylinders for cracks, valves and piston rings for condition. The test involves pressurizing each cylinder with 80 psi of shop air and testing to see how much leaks out. It is a procedure that is a bit dangerous as the pressure in the cylinder can make the propeller spin pretty quickly. If the cylinders check good, it makes the owner of the aircraft much happier. Any cylinder that leaks excessively must be repaired. Cylinders can be removed individually for repair.<br /><br />My next step-each IA has his or her own approach to accomplish the inspection checklist-is to drain the engine oil while it is hot and to remove the oil filter. The oil filter is cut open and the element is exposed to reveal any material that is circulating through the oil system. Normally the filter will have carbon in it and may have tiny pieces of different metals. With experience, the general aviation maintenance technician knows what is acceptable and what is not. If any ferrous metal is suspected, then a magnet is drawn across the filter element to grab that iron for further inspection. Many owners request an oil sample be taken from the drained oil to be sent to a laboratory for spectrometric trend analysis. (more about oil analysis at a later date)<br /><br />My reason for starting the inspection the way described above is: if a cylinder is bad, it can be removed and be shipped to a cylinder repair shop for repair while the remainder of the inspection is being done; if there is any unusual material inside of the oil filter, the engine may be defective and it does not make any sense completing an inspection and servicing on an engine that may have to be replaced.<br /><br />If the engine appears to be OK, an inspection of the engine and all of the components in the engine compartment can now be done. Components may include: exhaust system, starter, alternator, carburetor, ignition leads, vacuum pump, magnetos, fuel pumps, hoses, control cables, cowling and on and on. Servicing includes: cleaning engine, clean, gap & test spark plugs, fuel filter, oil suction screen, etc. In our shop, we have more than one person working on the aircraft at once to reduce the amount of time the aircraft will be unavailable to fly.<br /><br />The next step I take is to research the aircraft records for component times (some have to be replaced after a certain calendar or time in service), Airworthiness Directives compiance (more about AD's at a later date), Pilot's Operating Handbook (POH) currency & completeness, Weight & Balance information current, major repairs forms are present, Supplemental Type Certificates and Flight Manual Supplements are correct, etc.<br /><br />Next comes a visual inspection of the airframe. This portion of the inspection is a look, touch and feel event. Experience with the particular type of aircraft is very beneficial as each aircraft has it's own areas of continuing problems. <br /><br />The airframe requires servicing also and this includes: cleaning the whole airplane, cleaning wheel bearings & repacking with grease, putting air in the tires, servicing the battery and brake reservoir, lubing all control systems bearings & hinges, etc.<br /><br />During the inspection, a list of anything found to be unacceptable (unairworthy) is noted as a "discrepancy". The inspection and servicing checklists are completed by the person accomplishing the work. When this is all done, the owner is contacted with a report and is asked to come to the airplane to review everything that has been found and done. This is always the most difficult part of the Annual Inspection as it is necesssary to tell the owner, his "perfect" airplane is not quite so perfect. We never want anything to be "bad" on the airplane when we do the inspection but if anything is "bad", it is our job to find it. The word "airworthy" is not defined by the FAA, but the word is used to judge if the aircraft is safe to fly. There is not enough space here to express my feelings about "airworthiness" but I plan to address it at a later date.<br /><br />After making repairs to "unairworthy" items and any additional "cosmetic" items requested by the owner, the aircraft is put back together, the engine is run again and all of the systems are checked for operation again. The engine is then checked for any leaks and if everything is OK the aircraft is almost safe for another year's flying. Almost ready, because the required certification in the aircraft records as being "airworthy" needs to be done. The statement "I have inspected this aircraft in accordance with an annual inspection and have found it to be in airworthy condtion" with a proper certificate number and signature make it safe to fly.<br /><br />I have found many unusual things during an annual inspection including giant spiders from a South American based airplane (luckily the spider was dead), mice, nests, birds, bee hives with live bees (when you look inside of the wing, nothing should be moving around and buzzing), tools, bucking bars and notes written on the metal from whomever built the airplane. The general aviation maintenance technician has a very interesting job.General Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.com0tag:blogger.com,1999:blog-7169213317599779416.post-9792946090963662042009-10-02T19:04:00.000-07:002009-10-02T19:58:59.949-07:00Propellers are normally taken for granted on a general aviation airplane. They are almost invisible when they are doing their job to move the airplane through the air. It has been said that a propeller keeps a pilot cool because when a propeller stops in the air, the pilot starts to sweat.<br /><br />As general aviation maintenance technicians we see many propellers. Some props are made of one piece of machined aluminum, some are made of wood with metal leading edges, some blades are made of wood and composites, some blades are all composites, some are constant speed, some are reversable, some are full feathering, some are pushers, and they are made with 2,3,4,5 or 6 blades.<br /><br />During A&P training, our school had a video of propellers being tested to destruction. The slow motion videos showed the metal blades bending and twisting severely as the prop was subjected to loads that could never be achieved by any aircraft flight conditions. Even then, the blades were so tough that they did not fail. Another video showed a propeller that was not a good match to the vibrations caused by the engine it was installed on and the blades were amazingly bent during the harmonic imbalance. This type of testing and subsequent changes in prop design has made the modern propeller extemely reliable.<br /><br />Some twin engine airplanes have one propeller that turns clockwise and one propeller that turns counterclockwise to minimize the difficulty of controlling the airplane if one engine fails in flight. When installing a pair of these propellers on the aircraft, one should be aware of which side each one belongs on. If they are installed on the improper sides, the aircraft will be pushed backwards rather than being pulled forwards. Unfortunately I have seen this done. That young general aviation maintenance technician learned a good lesson that day. When the props were installed correctly they worked perfectly.<br /><br />Two common threats to the propeller are debris on the ground and attempting to land the aircraft when the landing gear is in the retracted position. During the preflight check, the engine is "runup" to about 2000 rpm to check the engine systems. Any debris in the area of the propeller may be drawn to the spinning blades and cause damage by striking the blades. (during a rainy day, a water spout often forms beneath the propeller and is fascinating to watch) These "nicks" can normally be filed out in the field without causing the propeller to be out of balance. During the pre-landing checklist, one of the check items is--landing gear down and locked. The propeller is not designed to be a landing gear and will have to be replaced when the ends of the blades are curled back on themselves.<br /><br />The back of the propeller blades (called the face) is painted black to reduce any reflections. The spinning propeller is essentially an invisibe disk when operating and the black paint works well to keep it invisible. The ends of each blade on the front are normally painted with white stripes to make them visible to anybody in the area. It is a very bad idea to walk into a spinning propeller turned by 200 horsepower. Occasionally the general aviation maintenance technicial must stand directly behind a spinning propeller to make engine adjustments. It is unnerving and very windy (in the winter it almost unbearably cold) This is an exercise of trust in the person who is operating the engine from the cockpit. The cockpit person is constantly vigilant of the outside persons movements and is ready to kill the engine ASAP.<br /><br />The general aviation maintenance technician is not authorized to make many repairs on propellers. The repair work is very specialized and requires special training and tooling. FAA Propeller Repair Stations do a good job of keeping these generally neglected masterpieces of engineering operating properly.General Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.com0tag:blogger.com,1999:blog-7169213317599779416.post-70763101818860721832009-10-01T18:17:00.000-07:002009-10-01T19:06:12.693-07:00"Come-on-lets go check out those motors you just put in!" It was the Chief Pilot of the company this young general aviation mechanic first worked for telling me that I was going to fly in the airplane I had just finished installing two freshly overhauled engines. Since I had every confidence that everything was done properly, the engines checked good during the ground runups and I just did not know better, I said "sure-lets go".<br /><br />I had never flown in this type of aircraft before and it was exciting to fly in the co-pilot seat.<br /><br />The engines started normally and the ground checks were all good. It was when we taxied to the active runway for takeoff that the "wonders" started going through my mind-I wonder if I tightened all of those fuel hoses-I wonder if I got the torque on the engine mount bolts right-I wonder if the throttle control hardware is saftied, etc. I know that I double checked everything but the "wonders" crept in.<br /><br />We rolled down the runway and soon lifted off. The engines were running perfectly. As we were climbing to altitude, the pilot lit a cigarette and started smoking. Never having been a smoker, the smell was annoying. Soon we were climbing through 15000 feet and I was starting to feel light-headed. I looked over at the pilot and he was still smoking away. The airplane reached 17000 feet and I told the pilot that I could not breath and was going to pass out. At the time I did not know that anytime you fly above 12500 feet in an unpressurized airplane you are required to use supplemental oxygen. The pilot looked over at me and must have decided that I did not look so good. Before I lost conscienceness, I saw the ground coming at us straight ahead-we were going vertical.<br /><br />I woke up and did not know what had happened. The pilot had leveled us off at 5000 feet and knew that there was enough oxygen to wake me up. He just looked over at me and smiled. This was his way to initiate a rookie general aviation maintenance mechanic into the business. The landing and taxi in were anti-climatic. I will never forget the experiences-especially the "wonders".<br /><br />Ever since that day, I have had another technician inspect the work I have done. This second set of eyes gives one an additional confidence that the aircraft is safe and the "wonders" do not come around so much anymore.<br /><br />All of our company's freshly minted general aviation maintenance technicians are trained to have their work inspected and will be told "you are going on this flight" soon after finishing one of their jobs. (they will not know when the order to fly will be given) Hopefully they will "wonder" and make sure the job is done correctly every time.General Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.com0tag:blogger.com,1999:blog-7169213317599779416.post-20664260235190220452009-09-30T17:13:00.000-07:002009-09-30T18:29:53.850-07:00One of the responsibilities of a general aviation maintenance technician is to properly notate any maintenance performed on an aircraft. Federal Aviation Regulation 43.9 mandates a maintenance record entry that contains the following information: a description of the work performed; the date the work was performed; the name of the person performing the work; the signature, certificate number and type of certificate of that person.<br /><br />The maintenance entry is normally made in a "LOGBOOK" and is kept with the aircraft, an engine or a propeller for the life of the item.<br /><br />Reading a logbook can be a very boring exercise so I have chosen to read the entries as I would read a novel. <br /><br />An actual entry from the beginning of an aircraft logbook reads: I have inspected this aircraft and issued a standard airworthiness certificate dated Dec 23, 1982 I/A/W FAR 21.183(a) Per 21.273 <signed> FAA DOA SO-1. I choose to interpret this as: A new baby aircraft has been born and is ready to take to the air.<br /><br />As the aircraft is flown, the logbooks reflect its life. Early on, there are few entries except for required inspections. Soon a brake has to be replaced, a gyro is overhauled, the landing gear oleo strut has to be resealed......... The baby airplane is going through growing pains just as a child that learns to walk, falls, gets the scrape treated and keeps on going. <br /><br />I have to wonder what was the circumstance when the gyro went bad. Was the pilot surprised that he was flying off course because he was following a precessing gyro or did it fail while making an IFR approach on the localizer? The pilot at the time let the general aviation maintenance technician know what the problem was, but that reason has been lost over the years. The important thing is, the pilot and aircraft were able to use alternate equipment to complete the mission.<br /><br />Log entries take many forms. (penmanship was not part of our training in general aviation maintenance school) Who wrote in black ink, blue ink, red ink, green ink, pencil? (black is the preferred color in ink, not pencil) Many entries have been made up-side-down in the book. The maxim: "the job is not done until the paperwork is done" is true but there are few general aviation maintenance technicians that like to do paperwork. Our specialty is electrical systems, hydraulics, sheet metal repairs, vacuum pumps, fuel hoses, windows, deicers, exhaust valves, propeller blades, tires, upholstery, air conditioners, landing gear, lift struts, fiberglass, painting, grease, control cables, trim tabs and the such.<br /><br />Aircraft records are very valuable. When an aircraft is sold, one of the primary questions will be "Are all of the logbooks present?" The logbooks can represent up to 1/3 of the value of an aircraft. Another question will be: "is there any damage history?" I feel that damage history is important but is not a reason to reduce the price of the aircraft if the repairs have been made properly. The price calculation of a used aircraft factors in each of these items (and many more) to allow the seller and buyer to negotiate a price that is acceptable to each.<br /><br />Many of the aircraft the general aviation maintenance technician maintains is over thirty years old and the novel of the logbooks is still being written.General Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.com0tag:blogger.com,1999:blog-7169213317599779416.post-30393713604601487402009-09-29T18:42:00.000-07:002009-09-30T15:03:46.448-07:00Preflight check list: Magnetos check-RIGHT;BOTH;LEFT;BOTH-maximum drop 150 rpm(maximum differential 50)<br />This is an item that is accomplished thousands of times a day by pilots and is checking an ignition system that is so reliable that the pilot will not think of it until the next preflight check is performed.<br /><br />The magneto is a self contained generator of electricity that sends the current to the correct spark plug at the proper time to make the controlled explosion of fuel and air in each cylinder.<br /><br />One of my first jobs in general aviation maintenance was to overhaul magnetos. The units are glorious in their simplicity. A fond memory of those early days of my career was of a company employee who was not a technician that kept picking up components from my work station and not returning them to the same place. I finally found out who the person was and set up a trap. One of the components of a magneto is called a condensor (capacitor now-a-days)and its function is to store an electrical charge. I charged up several condensors from our tester and placed them in a convient spot on my bench for curious hands to pick up. The person I suspected wandered into the shop and just happened to pick up a charged condenser. The 500 volts just happened to discharge across his hands. It was worth having the component being destroyed as the involuntary muscle jerk caused the unit to be thrown into the wall across the room. I never had another component wander from its assigned place on the workbench.<br /><br />A magneto uses a spinning magnet to generate the current and is completely independent from the aircraft electrical system. Some aircraft do not even have an electrical system. The engine is started by "hand propping" which is done by manually spinning the propeller. The magneto uses the force of the person turning the propeller to provide the spark to the spark plugs to start the combustion process which keeps turning the magneto.... and on and on.....until the engine runs out of fuel or the magneto is turned off. This same technology is used on most lawn mower engines.<br /><br />Just in case of a problem, there is a second magneto as a backup including a second set of spark plugs. Either magneto or both together will allow the engine to operate properly.<br /><br />The term "magneto timing" is common in the general aviation maintenance field. This term is simply the position where the magneto is installed so the spark is sent to the proper cylinder at the proper time for efficient combustion.<br /><br />Magneto manufacturers require their units to be disasembled every 500 hours of operation, be inspected, components be tested, cleaned and relubricated. During the aircraft required Annual Inspections, the magnetos timing is checked and adjusted as necessary to compensate for slightly worn components.<br /><br />I have seen a magneto that had its internal timing and timing to the engine be off by 15 degrees. The engine was running normally. This is a testimony for the inherent safety of the reciprocating aircraft engine.<br /><br />Jet engines and turboprop engines do not use magnetos. They usually have high current ignition systems to start the engine and once combustion is begun, it is self sustaining. Some of the new Light Sport Aircraft engines have a completely different ignition system that we may address in General Aviation Maintenance at a later date.<br /><br />Modern reciprocating engines are beginning to use a type of "electronic ignition" referred as FADEC (full authority digital engine control). Many modern General Aviation aircraft are beginning to use Diesel technology which does not use an ignition system at all. I am old-fashioned and think a magneto is "sexy". The magneto will be around for a long time.General Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.com0tag:blogger.com,1999:blog-7169213317599779416.post-80894684591692903462009-09-28T18:13:00.000-07:002009-09-30T15:13:32.615-07:00The mission of the FAA "...is to provide the safest, most efficient aerospace system in the world". We, as general aviation maintenance technicians, aspire to the same goal as far as safety is concerned. I feel that "efficiency" is more of a logistical idea of how aircraft are positioned around the country and normally does not affect our day to day job. Through our inspections and maintenenace of general aviation aircraft, we attempt to make sure that every time the airplane flys, it safe to do so.<br /><br />Safety also has a different meaning to the technician in the hangar. The mechanic who went searching for an avgas leak from beneath the wing with a cigarette lighter did not have safety in mind and jeopordized the safety of every other person in the shop. This person luckily did not find the leak and is no longer working with us. I hope he has learned more common sense in his new career. The fuel leak was found and repaired in a safe manner.<br /><br />An aircraft has many ways to injure the human body without the plane ever moving. Battery acid seems to burn the skin without any flame, sharp vent tubes seem to be sticking out everywhere you turn and feel like a super-sized hypodermic needle, and pitot tubes get hot enough to cause blisters.<br /><br />Most injuries can be avoided when working around the aircraft. Being aware of where you are working and a good knowledge of the system that you are investigating are the most important details for safety. I was working on a nose wheel one day when the propeller started hitting me on the head. I knew the engine could not start as I had disconnected the aircraft battery as a precaution. I looked up and another mechanic was attempting to move the prop to dress out some nicks in the leading edge. He couldn't figure out why the prop wouldn't move until I said to him "Are you through yet?" This is a minor example of how easy it would be to get hurt without trying. After working together for a short time, a good crew gets a feel for what everyone else is doing on the job and injuries are far & few between.<br /><br />An aircraft has many different fluids on board-brake fluid, hydraulic fluid, engine oil, anti-ice fluid, fuel, etc. Spilled fluids on the hangar floor not only make a mess but are very slippery. Keeping the work area clean is essential for safety. Don't want to slip and get stabbed by a pitot tube.<br /><br />Metal shavings, electrical systems, high pressure fluids, oxygen systems, cleaning solvents, paint thinners, lead by-products, combustion heaters, etc. (to name a few) make for a very interesting and challenging profession.<br /><br />Safety of flight and safety in the hangar are both important to the general aviation maintenance personnel.General Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.com0tag:blogger.com,1999:blog-7169213317599779416.post-24426380932755006272009-09-27T12:51:00.000-07:002009-10-04T15:20:51.434-07:00Most owners of General Aviation aircraft probably think of maintenance as a necessary evil. To keep an aircraft safe to fly, maintenance is definitely necessary. How many times has a brake failed because the linings were worn out and the aircraft veered off the runway to spoil an otherwise great day? What about a tire that went flat because of being low on pressure and ruining a day at the beach?<br /><br />General aviation maintenance is different from the larger aircraft as owners/operators are allowed to accomplish much of the work themselves as defined in FAR 43 "preventative maintenance". Changing brake linings is a simple process if you have the proper tools (much easier than changing pads on a car). The pilot operating handbook shows the proper pressure required for each tire and putting air in the tires is very easy. Sometime the tire servicing is made more difficult because of wheel fairings, but still is very basic.<br /><br />Flying an aircraft with low tire pressure not only wears out the tread on the outboard edges prematurely, but is dangerous because the only thing that a tire uses to secure it to the wheel is friction at the bead. If the pressure is low, and hard braking is required, then the tire could slip on the wheel which would reduce the amount of braking available. Most of the time these small airplanes don't need much in the way of braking, but when you need it the most, it may not be there.<br /><br />Thirty five years ago I decided to pursue a career in general aviation maintenance and have been doing it ever since. I soon found that I was allergic to JetFuel and started maintaining aircraft with reciprocating engines only. The aircraft that were brand new when I started can now be considered antiques (can I therefore be considered antique?) but many are still operating every day due to the quality of maintenance they have received.<br /><br />This blog is intended for anyone that may be able to benefit from my many years of experience and some of the humerous things that have been seen along the way.<br /><br />One example of "what was he thinking?<br /> Occasionally a main tire will wear unevenly on either the outer or inner edge. To extend the life of the tire, the tire is removed from the wheel, inner and outer sides are reversed and reinstalled. I mistakenly asked a young general aviation maintenance technician to rotate one of these tires for the customer. The technicial jacked the aircraft, rotated the tire around several times and put the aircraft back on the ground. I have since learned to ask to have the tire reversed rather than being rotated.General Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.com0tag:blogger.com,1999:blog-7169213317599779416.post-13476372463460424342009-09-26T17:50:00.000-07:002009-09-27T12:36:48.296-07:00General Aviation MaintenanceGetting Started<br /><br />For the energetic General Aviation Maintenance owner/operator, a good day's work might be all that's required, but be prepared for a physical workout that can range from mildly tiring to overall body fatigue and soreness (not to mention minor cuts from metal contact,etc.). The cost of cleaning materials is of minor consequence and usually less than $30 will cover the direct expenses. Many local detailing businesses may be hired to achieve the desired appearance for summer flying. However, many owners would rather do it themselves--both to save money, but also because taking care of your own personal airplane is one of the reasons men and women first decided to buy instead of rent! If this is you, then take the important obvious appearance items first and the less obvious after that.<br /><br />A Logical Next Step<br /><br />The most noticeable parts of the airplane are those in which a passenger might approach and then enter the main cabin door. That side of the aircraft must look appealing! If the airplane is really coated with dust and the effects of not having been flown regularly during winter, the airplane should either be sprayed off with an available water hose or alternately wiped down with a wet, though soft towel first. Air drying always works but toweling the airplane's upper wing and fuselage sides brings instant results. The windows must be cleaned (inside and out) with a high quality cleaner which will both safely remove light dust or grime and then polish the plastic surface to a shine (however, care should always be taken to clean windows in an up and down motion--never swirling, which can scratch!). This first step may only take an hour to achieve and is a good starting point towards taking off for that famous $100 hamburger at a distant airport restaurant as a reward.<br /><br />The Inside Counts<br /><br />The airplane's interior must eventually be cleaned and vacuumed to be enjoyed on those longer, overnight trips taken by private plane during the summer month's ahead. Commercial household agents can be used as long as no flammable materials are introduced into the carpet or upholstery. Again, the airplane's windows may be cleaned and special attention given to removing fingerprint grime common to areas of the moldings surrounding windows and door frames.<br /><br />The Hard Part<br /><br />The next step is probably the one most owners like the least: cleaning the belly (on single-engine airplanes) or beneath engine cowling and wing to the rear of each of a twin's engines. The right cleaning materials can help take the effort out of removing oil, grease, and exhaust stains, although there's no sugar-coating the physical effort and awkward body positions it usually takes to effectively remove the offending by-products of combustion engines. This step doesn't have to be done the first time out and no casual observer stoops down to look at a plane's belly or landing gear for cleanliness. Wait for another day or weekend if the washing and cleaning of the painted surfaces was more than enough for that effort!<br /><br />For Lasting Protection<br /><br />Finally, protecting the airplane's surface is important for both the plane's appearance and for safeguarding the durability of the paint. A glossy airplane can be the most memorable image a guest takes away from an outing but almost the most physically demanding! Therefore, take the advice given earlier in this article and only polish or wax the side of the airplane that is used to enter the airplane; do the other half the next day or weekend. These steps will ensure the desired appearance and utility of every airplane put into increased usage for the summer months ahead.General Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.com0tag:blogger.com,1999:blog-7169213317599779416.post-23685567037555634792009-09-26T17:49:00.000-07:002009-09-27T12:39:12.472-07:00General Aviation Maintenance Cessna 172 SkyhawkIt appears the most popular playing in general aviation in the history of mankind is the Cessna 172 Skyhawk. Over 35,000 General Aviation Maintenance have been sold and you can find these aircraft in airports around the world. Cessna aircraft Corporation has a proud history in general aviation and has become the largest general aviation aircraft manufacturer in history.<br /><br />Why has the Cessna 172 sold so many? Well, because generally people learn how to fly in a Cessna 150 and then they wish to take their family or friends and the Cessna 172 is a logical progression, as it holds for people and is not very expensive or complex to fly. The Cessna 172 also gets very good fuel economy and although it does not hold very much it is quite a bit cheaper than the next upgraded model the Cessna 182.<br /><br />You can ask any general aviation Private pilot if they have flown a Cessna 172 and there is a 90% chance that the answer will be yes because so many flight schools have them for rent along with many flying clubs. Many private pilots who end up buying their own aircraft say she was a Cessna 172 because of its simplicity and availability. It is doubtful that any other aircraft will ever surpass the Cessna 172 as the most popular aircraft in general aviation of all times.<br /><br />If you are considering buying an aircraft of your own a Cessna 172 will surely be on your list and although it may not end up your first choice the availability of used aircraft for sale makes the Cessna 172 Skyhawk a possible option.General Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.com0tag:blogger.com,1999:blog-7169213317599779416.post-1628240545828704122009-09-26T12:56:00.000-07:002009-09-27T12:47:05.011-07:00General Aviation MaintenanceDeciding what type of planes you want to maintain is the first thing you need to do before becoming an aircraft mechanic. It is necessary for you to have an idea of what you want to do with your mechanic's license, just like a car mechanic has the choice of working on Ferraris or Hyundais.... Are in small personal aircraft? General Aviation is the small, personal aircraft that are flown for small businesses and personal usage. The police and FBI use general aviation maintenance people to fix their surveillance planes, so you should know exactly what your goal is before entering any program of study, so take the time to discover exactly what you would like to do.<br /><br />Secondly, you should decide on a reputable aircraft maintenance school. Schooling prepares you for successfully completing the oral, written, and practical exams necessary for an FAA Mechanic Certificate. You should realize that you must choose a school that is appropriate for the goals you wish to achieve.<br /><br />Before entering any program of study, you will want to investigate it. As with any other field, discover the best program that will enable you to succeed and attain a successful career after graduation. Certified schools must offer students at least 1,900 class hours in general aviation maintenance, as required by FAA standards established by law. School coursework generally continues for 18 to 24 months and utilizes the same type of tools and equipment used on the job for training. You will be supervised by qualified instructors while learning practical on-the-job skills about 80 percent of the time, rather than merely sitting in a classroom, if you choose a quality school. The school you choose should be equipped with modern industry-standard equipment for you to learn with so that you can gain experience and feel comfortable handling these tools. Using out-dates tools will be of no benefit to you in the future.<br /><br />A lecture and a test are not the only things involved in school for aircraft mechanics. Aircraft mechanics have to completely understand the workings and build of the aircraft, so you will have to dismantle and reconstruct entire systems, like the engine. Students in General aviation maintenance school, through lecture and practical courses, will learn about all components of an airplane and become experts in aircraft repair and maintenance.<br /><br />However, you won't have your general aviation maintenance license once school is over. FAA regulations decree you must pass the prescribed tests.General Aviation Maintenancehttp://www.blogger.com/profile/13477853448251777235noreply@blogger.com0