rv-9a 90577 avionics/electrical
DESCRIPTION
RV-9A 90577 Avionics/Electrical. Disclaimer. It’s only perfect until you fly it, Then you’ll want to change it. … or build another airplane! (George McNutt). Degree of Difficulty. Designing and wiring an airframe and panel is difficult, but achievable. Read the references, and get help. - PowerPoint PPT PresentationTRANSCRIPT
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RV-9A 90577Avionics/Electrical
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Disclaimer
It’s only perfect until you fly it,
Then you’ll want to change it.
… or build another airplane!– (George McNutt)
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Degree of Difficulty• Designing and wiring an airframe and panel is
difficult, but achievable.• Read the references, and get help.• Start with a completed design and have a design
review.– Find an experienced builder or avtech to help
– Use the same person to consult with you through the tough parts.
– You will save a lot of money, time and frustration.
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Define the Mission• Basic VFR• Night VFR• VFR OTT• Day IFR• Night IFR• Equipment list is available in the CARS on Transport
Canada web site:– http://www.tc.gc.ca/CivilAviation/RegServ/affairs/cars/menu.htm
• Allow for upgrades (VFR-OTT to IFR?)• I decided on Night/VFR OTT
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Select the EquipmentBASIC VFR VFR OTT NIGHT VFR DAY IFR NIGHT IFR RV-9A
Sensitive Altimeter X X X X X XASI X X X X X XMagnetic Compass X X X X X XTach X X X X X XOil Pressure X X X X X XOil Temperature X X X X X XManifold Pressure (constant speed prop) X X X X X XFuel Levels X X X X X XComm X X X X X XNAV appropriate for dest and others for Class B X X X X XApproach/Missed Approach NAV for IMC X XPitot heat X O X X XDG X X X X XAI X O X X XTC X X X X XVSI O X X XElectrical System X X X XSpare fuses (50%) X X X breakersInstrument Illumination X X XLanding Light X X XAnti-collision Lights X X XOAT O X X XVacuum failure alarm X X all electric
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All-Electric or Electric/Vacuum?
• Many new certified aircraft are going all electric, even for full IFR.
• All-electric is lighter, cheaper and more reliable• But is prone to a single-point failure….
Alternator/Battery• Consider a stand-by alternator or backup battery
strategy.• Or you could use a vacuum system
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Failure Considerations• If it ain’t installed, it has zero weight, requires no
maintenance, is free and will never break.• Consider failure mechanisms:
– primary electric failure– individual instrument failure
• Have redundancy or backups– EFIS is backed up with ASI, TC, Compass, Stall indicator
and GPS virtual instruments.• Internal backup batteries for EFIS and GPS and Engine
Monitor. Handheld Comm.
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Avoid $$God-Boxes
• Glass cockpit displays are great, but….– They are expensive and big– you need two of them– and you need a backup electrical system
• The fewer functions in a box, the easier it is to provide a back-up– e.g. separate fuel level gauges backs up fuel
totalizer in engine monitor.
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Select the Equipment• Budget is always a consideration• Simplicity of installation is very important• For example
– Garmin AT SL-40 COMM has a dual-watch function, allowing you to listen to two frequencies at once and transmit on one
– Saves the weight, panel space and extra antenna of two separate comms.
– Maybe not cheaper because the SL-30 is about twice the price of two cheap comms.
• Consider buying new– New avionics are much more reliable than older, refurbished stuff.
– Lighter, lower power, less panel space as well.
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Design the Panel• Start with the Panel Designer program on line:
www.epanelbuilder.com
• Van’s has a full size Autocad file of the panel blank!– http://www.vansaircraft.com/public/downloads.htm
• This can be read by many CAD programs.
• Do all you design on the computer first.
• Measure for interfering parts on the aircraft structure and mark keep-out areas on the blank.
• Paper dolls work… you can find a lot of problems pretty quickly.
• It can take dozens of attempts to settle on what you want.
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Final Panel
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Design the Electrical System
• Lights, heated pitot, strobe system, alternator/battery system
• Connectors: wing-root disconnect, panel disconnect
• Start with the Aeroelectric Connection on-line! www.aeroelectric.com
• Use AC 43.13 as a reference for wire gauge, breaker/fuse selection and grounding techniques.
• Find a schematic design program: www.expresspcb.com
• Start with someone else’s design
• Get advice
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Getting Started
• Order the main electrical system parts… wire, terminals, lights, strobes, tie-wraps (about 2000 will do)
• www.steinair.com, www.aeroelectric.com, www.digi-key.ca, www.creativair.com, www.wicksaircraft.com, www.aircraftspruce.com,
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Wires & Terminals• Use Mil-spec Tefzel insulated wiring
– never use automotive (PVC) wiring!– Can burn and emit poisonous fumes
• Terminals– crimp terminals.
• fast-ons, ring terminals
• fast-ons not common in certified aircraft, but are used.
• Crimping is reliable and gas-tight
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Fuses or Breakers
• Both work
• Fuses are cheaper
• Breakers are easier to wire and indicate when tripped.
• Polyfuses may be used, but they are not certified.
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Switches
• Toggle or Rocker?
• Toggle are easier to mount, are very tactile and positively indicate their position
• Rockers can be backlit or labeled easily
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Cockpit/Panel Lighting
• Most avionics have built-in backlights
• You can add light rings, post lights or flood lights.
• A map light is a great addition
• Van’s sells a nice little dimmer module for $20.00
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Wire Grooming• String ties
– if you really want to impress the judges
• Tie-wraps– easy to use, easy to change
– you need about 2000 (1800 end up in the garbage)
• Cushion clamps– Used to secure wiring bundles and prevent chafing
• Split tubing– split polyethylene tubing lengthwise and glue onto sharp edges to prevent chafing.
• Coax– do not clamp tightly, it will affect the performance of the cable.
• Wire marking (if you don’t own a $3000 marking machine)– buy fabric label strips from www.steinair.com
– wire marking is a pain, but well worth it later on.
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Wire Routing
• Avoid running antenna coax in long wiring bundles.
• Don’t run transponder cable parallel to any other wire or coax.
• Put some slack in the ELT antenna cable.• Secure with cushion clamps around interfering
structures.
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Grounding• Firewall grounding bus for all power connections.
– Every circuit has a separate ground return.– Prevents electrical interference.
• Do not use the airframe as a power ground. – It is acceptable to use the wing spars as a ground return for
wing wiring• I ran a ground wire from the spars to the firewall.
• Shielded wire grounds can be grounded to the airframe/panel at one end only– Don’t use the shield to carry power.
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Tools• Wire strippers
• Wire cutters
• Crimp tools (d-sub, fast-on, coax, box)
• Crimp pin removal tools
• Dental probes
• Soldering iron
• DVM/Beeper
• Tie-wrap gun
• Heat-shrink tubing and heat gun
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Supplies
• Heat shrink tubing
• Dielectric grease– apply to connectors, terminals (long lasting)
• ACF-50, Corrosion-X– apply to connectors, terminals (24 months)
• Aluminum washers
• Lock washers (split ring and star)