Avionics-List Digest Archive

Sun 01/03/10


Total Messages Posted: 1



Today's Message Index:
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     1. 08:32 AM - Questions about circuit protection ()
 
 
 


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    Time: 08:32:18 AM PST US
    From: <bakerocb@cox.net>
    Subject: Questions about circuit protection
    1/3/2009 Hello Again Matthew Schumacher, You wrote: 1) "Are you saying that if I put the fuses under the panel where they aren't accessible then my airplane will still meet 14 CFR 91.205 (c) and that I won't need to carry spares?" Yes. That is exactly what the regulation is saying. If the pilot does not have access, while in flight, to the location of fuses installed in the aircraft's electrical system then there is no 91.205 regulatory requirment to carry any spare fuses. 2) "I would read "that are accessible to the pilot in flight" to mean that the fuse panel is accessible to the pilot,......." That is correct. 3) "..........not the fusees since who cares if you can get to the fuses if you can't get to the panel." Again correct. Your reasoning, and the reasoning of the regulation, is that if you cannot get access to the location of the fuses installed in the electrical system while in flight then there is no reason for the pilot to carry, and have access to, spare fuses while in flight. Now the wise pilot would carry some spare fuses, as well as some other spare items or tools (which can be discussed at length), so that he may perform some limited trouble shooting / repair work if needed on the ground at some away from home location in order to get back to home base or some other location where he might be able to effect a more permanent repair. 'OC' Says: "The best investment we can make is the effort to gather and understand knowledge." PS: If one is designing and manufacturing a 14 CFR Part 23 type certificated aircraft the regulations / requirements for fuse location in the aircraft's electrical system are found in Part 23.1357 (d) which says: "If the ability to reset a circuit breaker or replace a fuse is essential to safety in flight, that circuit breaker or fuse must be so located and identified that it can be readily reset or replaced in flight." But experimental amateur built aircraft are not required, per se, to comply with 14 CFR Part 23. If we build our experimental amateur built aircraft's electrical system in accordance with the philosophy that things can fail and that we have a plan B back up that will allow graceful degradation and continued safe flight to an acceptable landing site then no fuse in our electrical system would be "essential to safety in flight". =================================================== Time: 11:09:21 AM PST US From: Matthew Schumacher <schu@schu.net> Subject: Re: AeroElectric-List: Questions about circuit protection bakerocb@cox.net wrote: > If you are thinking of replacing fuses in the air to trouble shoot and > solve an electrical problem please think again. There are several > disadvantages. Some are: > > 1) Your airplane's Operating Limitations (part of its airworthiness > certificate) will require you to equip the aircraft in accordance with > 14 CFR 91.205 if you fly at night or IFR. > > Paragraph 91.205 (c) (6) says: "One spare set of fuses, or three spare > fuses of each kind required, that are accessible to the pilot in flight." > > This means that, by regulation, if you design your airplane so that you > have access to those fuse blocks in flight then you must also have > available to you all those spare fuses while in flight. Do you want to > create that burden / nuisance / danger? Hold on, back the truck up. Are you saying that if I put the fuses under the panel where they aren't accessible then my airplane will still meet 14 CFR 91.205 (c) and that I won't need to carry spares? I would read "that are accessible to the pilot in flight" to mean that the fuse panel is accessible to the pilot, not the fusees since who cares if you can get to the fuses if you can't get to the panel. schu




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