Intro to Av Chemical Science
Intro to Av Chemical Science AVS 1102
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This 8 page Study Guide was uploaded by Keanu Ratke on Monday October 12, 2015. The Study Guide belongs to AVS 1102 at Florida Institute of Technology taught by Tom Utley in Fall. Since its upload, it has received 36 views. For similar materials see /class/221693/avs-1102-florida-institute-of-technology in Science at Florida Institute of Technology.
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Date Created: 10/12/15
1 Corrosion Four Factors causing corrosion anode corrodes readily cathode doesn t corrode readily electrical path electrolyte Factors effecting corrosion size of anode and cathode large cathoderapid corrosion metal to mental contact sets up a galvanic cell temperate warmrapid time electrolytes water acids alkalis Tap water is less corrosive than rainwater and fresh water is less corrosive than salt water Alkalis are less corrosive than acids Other examples battery acids ozone sulfuric acids from lavatory and galley area Types Uniform entire surface quotrustquot on steel Pitting common on aluminum and magnesium alloys small white or grey dots then powder Galvanic 2 diff metals in contact with electrolyte Concentration cell crevice corrosion moisture works its way into crevice of 2 joined metals Intergranular MOST SERIOUS below surface along grain boundary EXfoliation advanced intergranular surface gains lifted by corrosion below Filiform breaks in the paint possibly intergranular worm traces beneath paint surface Stress corrosion cracking stresscorrosion intergranular cracking in specific environments Corrosion fatigue cyclic stresscorrosion Pressurization and depressurization causes fatigue Fretting highly loaded surfaces rub each other wearing coating leaving bare metal Black streaks at the surface face Common metals in aircraft Magnesium most chemically active pitting must have coating Low alloy steel surface oxidation pitting intergranular Stainless steel darkens and becomes rough Common Protective Coatings Cadmium sacrificial corrodes as anode yellow appearance red brown stain appears when worn away rust Chromium good protection subject to pitting Nickel Plating salt water environments NonDestructive Inspections Visual most common liquid dye penetrant magnetic particle cracks etc on iron eddy current multilayer structures xray ultrasonic exfoliation stress cracking and thinning Basic types of corrosion inspections Daily pre ight Routine areas not usually accessible Special AD documented Treatment paint stripping remove for proper assessment don t use acidic paint removers use protective equipment and check MSDS Categories less than 001 inchlight Blisters and scaling 001010 inch moderate Blistering exfoliation scaling more than 010 inch severe Surface prep wash carefully with water and cleaning compound reanodize aluminum before repainting give magnesium a conversion coating before repainting Corrosion prevention well trained mechanics Preventative maintenance Regular inspections once per month and applying preventative lubricants that limit metal to metal contact once each 90 days treatment proper tools inspection of damaged paintdrain holesgaskets and sealants minimize exposure time documentation Corrosion prone areas exhaust trail area battery compartment bilge area lavatories and galleys cargo areas wheel well areas MOST PUNISHMENT external skin engine 3 differences b t avionics and airframe corrosion controlless durable corrosion protective systems active and dissimilar metals left unprotected and in electrical contact small amounts of corrosion can render avionics inoperable 2 Aviation Oil Five Key Areas PBC3 piston rings and cylinder barrels bearings cams and lifters connecting rods crankshaft journals Seven functions lubrication and antiwear PRIMARY Viscosity stickyness cooling insufficient cooling excessive wear on pistons crankshaft bearings and camrod bearings cleaning washes rust dirt etc corrosion protection additives excess fuelcombustion byproductsacids in oilwaterrust and corrosion hydraulic action medium to transmit energy hydraulic lifters constant speed prop thermal stability break down shows up as inscreased deposits in turbochargers and piston undercrown Categories Straight mineral oil best for breakin lapping cleaning from mechanical washing only lapping compounds helps seat rings Ashless Dispersant holds particles in suspension darker under same op conditions Range of oils straight mineral from select high Viscosity index petroleum based stocks used for breakin Single grade premium quality ashless dispersant oils selective additives oxidation stability and antiwear Miluti grade ad oils 1550 SEMIsynthetic best in extreme temps excellent anti wear additives ONLY aviation oil acceptable for use in some Lycoming wo additional additives Automobile Oils never use them because aircraft engine run from 10075 max load and at high temps whereas car engines run at 15 most of the time Automobile additives result in sticking valves excessive bearing wear and pre ignition Oil changes follow manufacturers guidance and change oil before putting into storage Acid buildup accelerates corrosion Full ow filters have larger intervals of oil change don t judge oil by color Cut and examine filter each change Use mineral oils for first 1025 next 25 then change to ad Breakin is complete when consumption stabilizes but don t judge engine by consumption Don t take offbefore reaching proper temp metal to metal contactdamage oil should be able to boil off water in it Moisture enters during storage through induction exhaust and oil breather systems Avoidance Frequent use oil changes and operating at full temp Run at 100 temp for 30 mins to boil wateracids Overpriming fuel dilution oil too thin low Viscosity Take sample mid ow at same intervals cheapest preventative maintenance Check suction and pressure screens BreakIn follow instructions use correct oil type don t baby it monitor consumption and temps watch for changes after stabilization change oil freq winter inactive periods more than 60 days no cold starts preheat ifbelow freezing best mixture idle turbochargers 45 mins to spool down properly don t force cool during descent seek professional advice Check for hard carbon particles metal dirt pay attention to appearance of filter and contents Avoid contact with skin toxic use magnet to find ferrous particles Lapping cylinders and bearings wearing away the highest points Glazing varnish deposits on the cylinder walls left by lapping process to prevent run at maX power ensuring that temps are high enough to seat the rings Have breakin done professionally Oil Analysis gives relative concentrations of silicon iron chromium aluminum copper and lead Parameters viscosity too high temp too high too low temp too low and thin form fuel dilution too much water in oil doesn t evaporate Silican levels dirt content leakin intake system or dusty environment High Iron elevated wear of cam and lifters crankshaft or gear drives always high for breakin Aluminum piston wear Lead from fuel Silver radial engines wear of silver master rod bearings Phosphorus antiwear additives Calcium magnesium and zinc auto oils have been used 3 Aircraft Tires Types Bias Ply MOST POPULAR durability and retread ability Tread has a ribbed design good traction and water dispersant alternate layers of rubber coated fabric plys at OPPOSITE angles Radial Tires more landings less rolling resistance lighter Casing plys run RADIALLY not at opposite angles Belt plys and overlays Originally for military use on fighters Commercial aircraft must be certified for quotradialsquot Info on side of tires tire size Part load rating max loading for rated in ation pressure speed rating ply rating index of strength FAA TSO technical standard order rating type of tire tube or tubeless Types and rims must be matches prior to mounting quot12 hour stretch period once mounted and in ated Ture should hold constant pressure for 12 hours and lose no more than 5 pressure in 24 hours FIVE DEGREE TEMP DROP 1 PRESSURE DROP In comparison with other tires 16 times more load temps from 65 F to 300 F 15 times heavier 3 times the speed 2 times the de ection Results of underin ated or overloaded tires excessive quottraction waves and heating9 ex cracks air loss and even lower pressure Tires ex up to 1500 times per minute exing and heat are tires worst enemies not hard landings Fatigue deterioration quotsidewall blowout Excess exing excess tire heat 50 hotter9 damages rubber compounds and fabric Tread and carcass separation and bead failure can also occur Results in overin ation excessive center tread wear reduced traction increased susceptibility to cutting and FOD Tire inspections check daily when tires are COOL in ate to accommodate max loads and temps quotwhen tires are in ated under load in ate 4 higher Dual tire problems SAME pressures are essential unequal pressures effects both don t check visually quotzero in ated and fully in ated look the same 100105 no correction 95 add nitrogen 9095 insect and rein ate record findings remove tire ifmore than 5 drop in 24 hours 8090 change tire under 80 remove both tires and wheel assemblies Tread wear examination normal wear has been in ated and maintained properly center tread wear overin ated tread shoulder wear underin ated if tread has worn to fabric below specified depth or to the base of any groove replace tire Replace if any of these things are observed FOD and tread cute 0sz width of rib and deeper than 12 remaining tread or any cut that is into the casing ply peeled rib part of rib missing tread chunking from unimproved runways fabric becomes visible tread separation less ofadhesion between tire components due to excessive loads or ex heating from underin ation groove cracking and rib undercutting fabric is visible or crack extends under tread rib chevron cutting from crossgroove runways skid burn locking up brakes at spots tread rubber reversion hydroplaning sidewall cracks agem improper storage weather Tire removal safety approach from front or rear never side de ate tire remotely or let cool for 3 hours before never reduce pressure of a hot tire General info auto tire 2029 and monoply aircraft tire 1356 and 12 or more plys Aircraft tires experience 3 times the defelction of auto tires and withstand loads over 100000 lbs and are in ated to 200 psi Must handle speeds in excess of 245 mph Tire development 1 Computer design 2 Mold made prototype tire constructed 3 Prototype tests taxi takeoff and landing 4 Five phase characteristics test OEM requirements 5 Durability analysis for retreading exceed OEM requirements Made out of natural rubber more heat resistant sulfur carbon black Process blended extruded blended with nylon hand built by craftsman in 2 hours molded and shaped in curing process quality check Retreading some tires retreaded 10 times or more Visual inspection air injection for casing separation and liner leaks standby for 12 16 hours to remove moisture tires buffed casing inspectedrepaired cementing repairs to casing and exposed fabric tread reinforcing band is installed tread rubber applied tire balanced tire cured in electric mold stand final finish stage tread rubber vents removed sand away over ow visyal and NDI using film based holography and serigraphy using video screens 4 Aviation Grease oil with additives Four functions prevents metal to metal contact prevents corrosion acts as a seal against dirt and dust stays where applied and holds particle in suspension Three componentsbase oil 7095 thickener 515 performance additives 0 15 Base oils esters synthetic hydrocarbons mineral oils Function as lubrication carrier for additives affects ow and pump stability affects useful temp affects elastomer compatibility Thickeners control the dropping point the lower the d point the more rapily the grease liquefies affects mechanical stability and the resistance to water Microgel clay increase d point THICK Calcium soap lowers d point low viscosity Lithium compleX used for wide range of temps Performance additives antirust antiwear eXtreme pressure oxidation inhibiters tackiness agents additives that affect mechanical mechanical sliding action Aeroshell 33 meets specifications of Boeing multiuse standards 33 3 developed for use by Boeing on their commercial eet On 350 lubrication sites it can be used on all but 9 Storage and handling FIRST IN FIRST OUT SYSTEM protected clean area discard if over THREE years old no damaged containers atten surface ofproduct before resealing container always miX before use never use wooden spoon or ladle it contaminates don t store in newspaper or butcher paper absorbs grease Lubricating tipsalways refer to manufacturers operation manual SPECIFIC to the airplane Most critical areas landing gear wheels and control systems Frequency oflubrications depends on use and location more frequent for dusty environment wet runway use or frequent deicing Bearing inspections look for pitting discoloration water spotting and dents Repack ifits been stored 3 years Repack any new bearing before installation good idea Steps for cleaning bearings clean in mineral spirits air dry and inspect clean with ultrasound or alcohol Fully lubricate one side Check freedom of movement then wipe off Same on other side then reset bearing seals Bearing should be packed between 4050 capacity NEVER MIX GREASES REGARDLESS OF MIL SPEC
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