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Design Goals

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jpx(at)qenesis.com
Guest

Posted: Wed Mar 10, 2010 8:02 am Post subject: Design Goals

There is a lot of good discussion on this list about improving our  

designs based on our goals.



Some of these goals are based on our personal flight profiles, but  

some speak to best practices. It is the best practices I am discussing  

here.



Some of the best practices have been established for us by the FAA,  

and others we have worked out by "ourselves" - Thanks Bob !



We talk about these best practices as if we all know what all of them  

are, but I suspect that is not true, since they are not collected in a  

single place. I know it is not for me.



I think what might be very helpful, is a checklist of design  

goals/best practices. This is something we could use after completing  

our designs to ensure that we have not overlooked something important  

and that we are aware of everything before we start pulling wires  

through the wings.



I will start it off:



DESIGN GOAL/ BEST PRACTICE CHECKLIST

- Unfused, high current wires - minimize length to 6" or less

- Consider voltage drop as well as current capability when sizing wires

- Fuses or circuit breakers are intended to protect wire, not devices

- Avoid bringing high current wires to the instrument panel using relays

- Use a relay rather than a switch for currents above 7A

- Avoid single points of failure when possible

Use two single-pole switches in place of a single switch for a critical

item, such as ignition

- Consider ground paths to avoid ground loops

- Use higher capability components than needed, when robust packaging is

advantageous

- Make sure you can shut it off if it is misbehaving

- Consider the effect of failure of any single electrical device

- Simpler is more reliable, easier to build, troubleshoot and maintain

- More expensive items still fail - less expensive items may be quite suitable

- Plan alternatives, so devices are not critical to safe flight



Please add to this list !



Jeff Page

Dream Aircraft Tundra #10

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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peter(at)sportingaero.com
Guest

Posted: Wed Mar 10, 2010 2:02 pm Post subject: Design Goals

Jeff,



That's an great idea, and an excellent start. My suggestion would be to 

try to order the goals into logical grouping, for example overall system 

goals (Make sure you can shut it off if it is misbehaving), principles 

(Fuses or circuit breakers are intended to protect wire, not devices), 

and wiring goals (Unfused, high current wires - minimize length to 6" or 

less )



I would re-order your list like this - please feel free to change the 

names, changes words, add or subtract



Peter

System Goals

- Any single failure should not take out any flight critical service 

(was, Avoid single points of failure when possible)

- Make sure you can shut it off if it is misbehaving

- Simpler is more reliable, easier to build, troubleshoot and maintain 

(Sydney Camm <http://www.historylearningsite.co.uk/sidney_camm.htm> - 

"Simplicate and add lightness")

- Plan alternatives, so devices are not critical to safe flight

- Following the failure of any single function or device the pilot 

should be able to safely continue flying with a maximum of ?2? switch 

selections



Principles

- Fuses or circuit breakers are intended to protect wire, not devices

- Avoid bringing high current wires to the instrument panel using relays

- Use a relay rather than a switch for currents above 7A

- Use two single-pole switches in place of a single switch for a 

critical item, such as ignition

- Use higher capability components than needed, when robust packaging is 

advantageous

- Consider the effect of failure of any single electrical device

- More expensive items still fail - less expensive items may be quite 

suitable



Wiring Goals

- Unfused, high current wires - minimize length to 6" or less

- Consider voltage drop as well as current capability when sizing wires

- Consider ground paths to avoid ground loops

Jeff Page wrote:

 	  Quote: 	
		   



 There is a lot of good discussion on this list about improving our 

 designs based on our goals.



 Some of these goals are based on our personal flight profiles, but 

 some speak to best practices. It is the best practices I am discussing 

 here.



 Some of the best practices have been established for us by the FAA, 

 and others we have worked out by "ourselves" - Thanks Bob !



 We talk about these best practices as if we all know what all of them 

 are, but I suspect that is not true, since they are not collected in a 

 single place. I know it is not for me.



 I think what might be very helpful, is a checklist of design 

 goals/best practices. This is something we could use after completing 

 our designs to ensure that we have not overlooked something important 

 and that we are aware of everything before we start pulling wires 

 through the wings.



 I will start it off:



 DESIGN GOAL/ BEST PRACTICE CHECKLIST

 - Unfused, high current wires - minimize length to 6" or less

 - Consider voltage drop as well as current capability when sizing wires

 - Fuses or circuit breakers are intended to protect wire, not devices

 - Avoid bringing high current wires to the instrument panel using relays

 - Use a relay rather than a switch for currents above 7A

 - Avoid single points of failure when possible

 Use two single-pole switches in place of a single switch for a critical

 item, such as ignition

 - Consider ground paths to avoid ground loops

 - Use higher capability components than needed, when robust packaging is

 advantageous

 - Make sure you can shut it off if it is misbehaving

 - Consider the effect of failure of any single electrical device

 - Simpler is more reliable, easier to build, troubleshoot and maintain

 - More expensive items still fail - less expensive items may be quite 

 suitable

 - Plan alternatives, so devices are not critical to safe flight



 Please add to this list !



 Jeff Page

 Dream Aircraft Tundra #10

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?AeroElectric-List

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