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trigo(at)mail.telepac.pt
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 Posted: Tue Jan 05, 2010 5:05 pm Post subject: [AeroElectric-List] Questions about circuit protection |
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Bob
I really don’t want to resuscitate this discussion but, even being aware of the technical advantages of fuses versus circuit breakers, it is indeed almost impossible to convince a pilot that a fuse is better than a circuit breaker.
In flight, when a fuse blows, the pilot will hardly notice it, and even if some device (whose circuit was protected by that fuse) becomes blank, he will not know if it was the fuse or anything else that caused that device to die.
If a circuit breaker pops out, there is a big probability the pilot will immediately notice it, or at least after seeing any device die, he will immediately look to the circuit breakers heads to look for the one that popped out.
Being a pilot trained for so many things, he must also know that he shall not push that particular breaker in, unless he wants to light up the fire which will burn his own ass…
It is probably easy to convince an aircraft builder to prefer fuses, but since in the OBAM world we are builders AND pilots, circuit breakers are certainly much more user friendly for the pilot, even knowing that the PILOT is the most dangerous single-point-of-failure in a flying aircraft
Carlos
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L. Nuckolls, III
Sent: terça-feira, 5 de Janeiro de 2010 15:03
To: aeroelectric-list(at)matronics.com
Subject: RE: AeroElectric-List: Re: Questions about circuit protection
At 06:52 PM 1/4/2010, you wrote:
Whenever this “fuses versus circuit breakers” discussion comes afloat, I always wonder why TC aircraft always used circuit breakers…
Carlos
They didn't. The first airplanes to get electrical
systems at Cessna used fuses. They were cartridge
fuse holders with caps that could easily be dropped
on the floor and be difficult to find. When miniature,
low cost breakers came along, they offered a means
by which operational and environmental concerns
for the use of glass cartridge fuses could be
addressed.
It wasn't until the blade fuse came along that
environmental issues were resolved for re-considering
fuses in airplanes. It wasn't until we address the
ideas of failure tolerant system design that the
operational issues were resolved.
If the TC aircraft guys were so disposed, they
could do exactly what we're doing right now. But
regulatory inertia makes this unlikely to happen.
Bob . . . | Quote: | | http://www.matronics.com/Navigator?AeroElectric-List |
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Bob McC
Joined: 09 Jan 2006
Posts: 258
Location: Toronto, ON
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| Posted: Tue Jan 05, 2010 8:14 pm Post subject: [AeroElectric-List] Questions about circuit protection |
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Carlos;
Different “Bob” here, but I must disagree with your viewpoint. Please see embedded comments.
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Carlos Trigo
Sent: Tuesday, January 05, 2010 8:00 PM
To: aeroelectric-list(at)matronics.com
Subject: RE: [AeroElectric-List] Questions about circuit protection
Bob
I really don’t want to resuscitate this discussion but, even being aware of the technical advantages of fuses versus circuit breakers, it is indeed almost impossible to convince a pilot that a fuse is better than a circuit breaker.
Why?? Fuse is simpler, less expensive, probably neater, and serves its intended purpose admirably. I’ve been a pilot for 35 years, a builder for only 5 and I much prefer the simplicity and economy of fuses. I consider myself a pilot first and I don’t need convincing, I know fuses are better. (At least in my own mind they are)
In flight, when a fuse blows, the pilot will hardly notice it, and even if some device (whose circuit was protected by that fuse) becomes blank, he will not know if it was the fuse or anything else that caused that device to die.
And how is that any different than the symptoms presented by a tripped breaker? The supplied device ceases to function in either case. To the pilot operating the aircraft there is no difference, he looses the benefit of whatever widget was supplied power by that circuit.
If a circuit breaker pops out, there is a big probability the pilot will immediately notice it, How or why will he notice it?? and why does it matter?? or at least after seeing any device die, he will immediately look to the circuit breakers heads to look for the one that popped out.
Are you making the assumption that the breakers are somehow readily available, visible and accessible in flight?? What if the breakers are neatly hidden away up under the panel, are on a fold down bracket, or in some other manner not readily apparent to the pilots position or his line of sight? What if the breaker that faults is one on the battery buss, hidden away in the tail cone next the battery? How does that present some different scenario to the pilot than would a fuse??
Being a pilot trained for so many things, he must also know that he shall not push that particular breaker in, unless he wants to light up the fire which will burn his own ass…
All the more reason for, and another demonstration of, the superiority of hidden fuses. (Or hidden breakers for that matter) Removes the temptation and doesn’t require the discipline and willpower “not to reset”.
It is probably easy to convince an aircraft builder to prefer fuses, but since in the OBAM world we are builders AND pilots, circuit breakers are certainly much more user friendly for the pilot, even knowing that the PILOT is the most dangerous single-point-of-failure in a flying aircraft
I really fail to see the “user friendly” analogy. The fuses in all the cars I’ve owned have been about as “user friendly” as I can imagine, and in some of my cars I never had occasion to even learn where they were. Can’t remember the last time one ever blew. In the dozen or so types of aircraft I’m checked out in, I can’t remember the last time a fuse blew, or a breaker tripped either. In a properly designed and functioning car or aircraft, I wouldn’t “expect” the circuit protection devices to be called upon to do their job for the life of the vehicle, be it airborne or ground based. I fully agree with the “insurance” provided by their presence, but wouldn’t expect them to be called upon. (If breakers are somehow superior, why do the millions of cars on the road use fuses?) As Bob explained the main reason aircraft migrated to expensive breakers was to mitigate the drawbacks of “old” technology glass cartridge fuses such as loose retaining caps and low pressure contacts prone to corrosion. We now have modern “blade” fuses without these shortcomings.
Don’t get me wrong, I fully understand and respect your opinion and viewpoint, I just can’t get a grasp on the logic behind it. As one who makes a living as an engineer, I view simple as better and fuses are simpler and less expensive than breakers and have much less chance of having something go wrong with them which makes the pilot side of me much more relaxed and comfortable with fuses than breakers.
Carlos
Respectfully,
Bob McC
[quote][b]
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Bob McC
Falco #908
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junk(at)jaredyates.com
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| Posted: Tue Jan 05, 2010 10:22 pm Post subject: [AeroElectric-List] Questions about circuit protection |
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In some of the larger factory-made airplanes, the breakers are situated behind the pilot’s head. In this location popped breakers are only obvious if you get up out of your seat to look. It’s pretty embarrassing to call the maintenance guys, go through some diagnostics on a non-functioning gadget, then have them instruct you to pull the breaker and doh! It was popped all along. One time I tried to extend the flaps for landing, but they didn’t extend because all 5 of the flap motor circuit breakers have been pulled since before takeoff. In that case the mechanics were working on the flaps, pulled the breakers as a normal safety measure, but then forgot to put them in when they were done. Then two pilots didn’t notice that they were out, at least not until configuring for the landing. In that airplane the normal flap setting for takeoff was zero. I can think of several other similar stories that illustrate that popped breakers aren’t necessarily all that obvious. Once you realize that something isn’t working and start looking for a breaker, they might be more obvious than a fuse, unless you spend the extra cents on the bling-bling LED fuses.
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Bob McCallum
Sent: Tuesday, January 05, 2010 11:11 PM
To: aeroelectric-list(at)matronics.com
Subject: RE: AeroElectric-List: RE: [AeroElectric-List] Questions about circuit protection
Carlos;
Different “Bob” here, but I must disagree with your viewpoint. Please see embedded comments.
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Carlos Trigo
Sent: Tuesday, January 05, 2010 8:00 PM
To: aeroelectric-list(at)matronics.com
Subject: RE: [AeroElectric-List] Questions about circuit protection
Bob
I really don’t want to resuscitate this discussion but, even being aware of the technical advantages of fuses versus circuit breakers, it is indeed almost impossible to convince a pilot that a fuse is better than a circuit breaker.
Why?? Fuse is simpler, less expensive, probably neater, and serves its intended purpose admirably. I’ve been a pilot for 35 years, a builder for only 5 and I much prefer the simplicity and economy of fuses. I consider myself a pilot first and I don’t need convincing, I know fuses are better. (At least in my own mind they are)
In flight, when a fuse blows, the pilot will hardly notice it, and even if some device (whose circuit was protected by that fuse) becomes blank, he will not know if it was the fuse or anything else that caused that device to die.
And how is that any different than the symptoms presented by a tripped breaker? The supplied device ceases to function in either case. To the pilot operating the aircraft there is no difference, he looses the benefit of whatever widget was supplied power by that circuit.
If a circuit breaker pops out, there is a big probability the pilot will immediately notice it, How or why will he notice it?? and why does it matter?? or at least after seeing any device die, he will immediately look to the circuit breakers heads to look for the one that popped out.
Are you making the assumption that the breakers are somehow readily available, visible and accessible in flight?? What if the breakers are neatly hidden away up under the panel, are on a fold down bracket, or in some other manner not readily apparent to the pilots position or his line of sight? What if the breaker that faults is one on the battery buss, hidden away in the tail cone next the battery? How does that present some different scenario to the pilot than would a fuse??
Being a pilot trained for so many things, he must also know that he shall not push that particular breaker in, unless he wants to light up the fire which will burn his own ass…
All the more reason for, and another demonstration of, the superiority of hidden fuses. (Or hidden breakers for that matter) Removes the temptation and doesn’t require the discipline and willpower “not to reset”.
It is probably easy to convince an aircraft builder to prefer fuses, but since in the OBAM world we are builders AND pilots, circuit breakers are certainly much more user friendly for the pilot, even knowing that the PILOT is the most dangerous single-point-of-failure in a flying aircraft
I really fail to see the “user friendly” analogy. The fuses in all the cars I’ve owned have been about as “user friendly” as I can imagine, and in some of my cars I never had occasion to even learn where they were. Can’t remember the last time one ever blew. In the dozen or so types of aircraft I’m checked out in, I can’t remember the last time a fuse blew, or a breaker tripped either. In a properly designed and functioning car or aircraft, I wouldn’t “expect” the circuit protection devices to be called upon to do their job for the life of the vehicle, be it airborne or ground based. I fully agree with the “insurance” provided by their presence, but wouldn’t expect them to be called upon. (If breakers are somehow superior, why do the millions of cars on the road use fuses?) As Bob explained the main reason aircraft migrated to expensive breakers was to mitigate the drawbacks of “old” technology glass cartridge fuses such as loose retaining caps and low pressure contacts prone to corrosion. We now have modern “blade” fuses without these shortcomings.
Don’t get me wrong, I fully understand and respect your opinion and viewpoint, I just can’t get a grasp on the logic behind it. As one who makes a living as an engineer, I view simple as better and fuses are simpler and less expensive than breakers and have much less chance of having something go wrong with them which makes the pilot side of me much more relaxed and comfortable with fuses than breakers.
Carlos
Respectfully,
Bob McC
| Quote: | | http://www.matronics.com/Navigator?AeroElectric-List |
0123456789
[quote][b]
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jay(at)horriblehyde.com
Guest
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| Posted: Wed Jan 06, 2010 3:03 am Post subject: [AeroElectric-List] Questions about circuit protection |
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I use fuses for my designs as well and add what I call a FAP (Fuse Annunciator Panel) which is an array of LED’s that are connected to the ‘downsteam’ side of the fuse. By pressing a common pushbutton that connects all of the LED’s to ground I can immediately see whether all of the fuses are OK. For the pilot this is great- press the button on the pre-flight and the status of all the fuses is shown; and in flight they can check the fuses the same way if there is some suspicion that a fuse has blown. It requires some extra PT with the wiring but I am working on a fuse holder that will make this much easier. My first version was a bit clumsy, but they’re getting better. I even have a light test button… J
Jay
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Jared Yates
Sent: 06 January 2010 08:16 AM
To: aeroelectric-list(at)matronics.com
Subject: RE: AeroElectric-List: RE: [AeroElectric-List] Questions about circuit protection
In some of the larger factory-made airplanes, the breakers are situated behind the pilot’s head. In this location popped breakers are only obvious if you get up out of your seat to look. It’s pretty embarrassing to call the maintenance guys, go through some diagnostics on a non-functioning gadget, then have them instruct you to pull the breaker and doh! It was popped all along. One time I tried to extend the flaps for landing, but they didn’t extend because all 5 of the flap motor circuit breakers have been pulled since before takeoff. In that case the mechanics were working on the flaps, pulled the breakers as a normal safety measure, but then forgot to put them in when they were done. Then two pilots didn’t notice that they were out, at least not until configuring for the landing. In that airplane the normal flap setting for takeoff was zero. I can think of several other similar stories that illustrate that popped breakers aren’t necessarily all that obvious. Once you realize that something isn’t working and start looking for a breaker, they might be more obvious than a fuse, unless you spend the extra cents on the bling-bling LED fuses.
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Bob McCallum
Sent: Tuesday, January 05, 2010 11:11 PM
To: aeroelectric-list(at)matronics.com
Subject: RE: AeroElectric-List: RE: [AeroElectric-List] Questions about circuit protection
Carlos;
Different “Bob” here, but I must disagree with your viewpoint. Please see embedded comments.
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Carlos Trigo
Sent: Tuesday, January 05, 2010 8:00 PM
To: aeroelectric-list(at)matronics.com
Subject: RE: [AeroElectric-List] Questions about circuit protection
Bob
I really don’t want to resuscitate this discussion but, even being aware of the technical advantages of fuses versus circuit breakers, it is indeed almost impossible to convince a pilot that a fuse is better than a circuit breaker.
Why?? Fuse is simpler, less expensive, probably neater, and serves its intended purpose admirably. I’ve been a pilot for 35 years, a builder for only 5 and I much prefer the simplicity and economy of fuses. I consider myself a pilot first and I don’t need convincing, I know fuses are better. (At least in my own mind they are)
In flight, when a fuse blows, the pilot will hardly notice it, and even if some device (whose circuit was protected by that fuse) becomes blank, he will not know if it was the fuse or anything else that caused that device to die.
And how is that any different than the symptoms presented by a tripped breaker? The supplied device ceases to function in either case. To the pilot operating the aircraft there is no difference, he looses the benefit of whatever widget was supplied power by that circuit.
If a circuit breaker pops out, there is a big probability the pilot will immediately notice it, How or why will he notice it?? and why does it matter?? or at least after seeing any device die, he will immediately look to the circuit breakers heads to look for the one that popped out.
Are you making the assumption that the breakers are somehow readily available, visible and accessible in flight?? What if the breakers are neatly hidden away up under the panel, are on a fold down bracket, or in some other manner not readily apparent to the pilots position or his line of sight? What if the breaker that faults is one on the battery buss, hidden away in the tail cone next the battery? How does that present some different scenario to the pilot than would a fuse??
Being a pilot trained for so many things, he must also know that he shall not push that particular breaker in, unless he wants to light up the fire which will burn his own ass…
All the more reason for, and another demonstration of, the superiority of hidden fuses. (Or hidden breakers for that matter) Removes the temptation and doesn’t require the discipline and willpower “not to reset”.
It is probably easy to convince an aircraft builder to prefer fuses, but since in the OBAM world we are builders AND pilots, circuit breakers are certainly much more user friendly for the pilot, even knowing that the PILOT is the most dangerous single-point-of-failure in a flying aircraft
I really fail to see the “user friendly” analogy. The fuses in all the cars I’ve owned have been about as “user friendly” as I can imagine, and in some of my cars I never had occasion to even learn where they were. Can’t remember the last time one ever blew. In the dozen or so types of aircraft I’m checked out in, I can’t remember the last time a fuse blew, or a breaker tripped either. In a properly designed and functioning car or aircraft, I wouldn’t “expect” the circuit protection devices to be called upon to do their job for the life of the vehicle, be it airborne or ground based. I fully agree with the “insurance” provided by their presence, but wouldn’t expect them to be called upon. (If breakers are somehow superior, why do the millions of cars on the road use fuses?) As Bob explained the main reason aircraft migrated to expensive breakers was to mitigate the drawbacks of “old” technology glass cartridge fuses such as loose retaining caps and low pressure contacts prone to corrosion. We now have modern “blade” fuses without these shortcomings.
Don’t get me wrong, I fully understand and respect your opinion and viewpoint, I just can’t get a grasp on the logic behind it. As one who makes a living as an engineer, I view simple as better and fuses are simpler and less expensive than breakers and have much less chance of having something go wrong with them which makes the pilot side of me much more relaxed and comfortable with fuses than breakers.
Carlos
Respectfully,
Bob McC
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trigo(at)mail.telepac.pt
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| Posted: Wed Jan 06, 2010 10:48 am Post subject: [AeroElectric-List] Questions about circuit protection |
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‘Lectric Bob
I do agree with you. Fuses have many technical advantages, weight, price, simplicity of wiring and others.
I also agree with you that it is a matter of choice or preference.
That’s why, in my perspective as a pilot, I do prefer circuit breakers.
From me, end of discussion.
Thanks
Carlos
From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L. Nuckolls, III
Sent: quarta-feira, 6 de Janeiro de 2010 16:55
To: aeroelectric-list(at)matronics.com
Subject: Re: AeroElectric-List: RE: [AeroElectric-List] Questions about circuit protection
At 07:00 PM 1/5/2010, you wrote:
Bob
I really don’t want to resuscitate this discussion but, even being aware of the technical advantages of fuses versus circuit breakers, it is indeed almost impossible to convince a pilot that a fuse is better than a circuit breaker.
It has never been offered as 'better' . . . only
adequate to the task of meeting design goals in
a failure tolerant system.
In flight, when a fuse blows, the pilot will hardly notice it, and even if some device (whose circuit was protected by that fuse) becomes blank, he will not know if it was the fuse or anything else that caused that device to die.
Have you read . . .
http://www.aeroelectric.com/articles/fusvbkr2.html
If a circuit breaker pops out, there is a big probability the pilot will immediately notice it, or at least after seeing any device die, he will immediately look to the circuit breakers heads to look for the one that popped out.
Being a pilot trained for so many things, he must also know that he shall not push that particular breaker in, unless he wants to light up the fire which will burn his own ass…
It's not clear that you embrace/understand the
rationale presented for unreachable fuse-blocks.
Certainly everyone has a choice to make and
in the final analysis it's personal. I did a
power distribution diagram for the BD-10 jet
about 15 years ago. I bounced the idea of fuse-blocks
off the electrical systems wienie. He agreed that
they were adequate to the task but opined that
anyone building a BD-10 wanted that "busy fighter
cockpit look. The more knobs, buttons and switches
the better." But even after the drawing was completed
using breakers throughout, he about had a cow when
I put about a dozen breakers back in the engine
compartment. The architecture called for protection
in these feeders and the sources for those feeders
were in the tail. Further, there was no failure
mode effects analysis that supported any need for
pilot access to these breakers whatsoever. Nonetheless,
he insisted on having all breakers in the cockpit.
I submitted my bill for work accomplished to date
and bowed out of the project. Got a nastygram from
Mr. Bede hisself honking about the fee and stating
that his electro-wienie wasn't authorized to make
contracts. I settled for 50 cents on the dollar
and chalked it up to the fates.
Have you identified errors in the logic offered in many
published pieces on the website and here on the
List that speak to suitability of fuses? If not,
then like the BD-10 episode, it's a matter of preference.
Breakers and their panels are not unsafe. They're
only heavier, more expensive, take up panel space,
require hours of fabrication time, restrict
wire bundle routing options, offer no enhanced level
of safety and MAY be distracting to a pilot who should
be doing more important things.
But if one chooses breakers, they're in good company.
The vast majority of the GA fleet is carrying tons
of them around the sky with a vanishingly small
probability that any single breaker will ever be
called upon to do its job.
Bob . . .
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tomcostanza
Joined: 19 Oct 2008
Posts: 49
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| Posted: Thu Jan 07, 2010 6:44 am Post subject: Re: [AeroElectric-List] Questions about circuit protection |
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| Quote: | | I even have a light test button |
Jay, what if the light test button fails?
-Tom
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jay(at)horriblehyde.com
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