X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Wed, 10 Aug 2011 08:13:27 -0400 Message-ID: X-Original-Return-Path: Received: from qmta09.westchester.pa.mail.comcast.net ([76.96.62.96] verified) by logan.com (CommuniGate Pro SMTP 5.4.1) with ESMTP id 5087746 for lml@lancaironline.net; Wed, 10 Aug 2011 07:40:39 -0400 Received-SPF: pass receiver=logan.com; client-ip=76.96.62.96; envelope-from=waynefmarshall@comcast.net Received: from omta20.westchester.pa.mail.comcast.net ([76.96.62.71]) by qmta09.westchester.pa.mail.comcast.net with comcast id JbY51h0061YDfWL59bg4Sk; Wed, 10 Aug 2011 11:40:04 +0000 Received: from [10.0.1.200] ([75.64.208.21]) by omta20.westchester.pa.mail.comcast.net with comcast id Jbg21h00K0UEJBP3gbg3nB; Wed, 10 Aug 2011 11:40:04 +0000 X-Original-Message-Id: <53373646-A05D-4E6F-810E-DD2EDA55EC38@comcast.net> From: Wayne Marshall X-Original-To: Lancair Mailing List In-Reply-To: Content-Type: multipart/alternative; boundary=Apple-Mail-2--338247456 Mime-Version: 1.0 (Apple Message framework v936) Subject: AC Problem X-Original-Date: Wed, 10 Aug 2011 06:40:01 -0500 References: X-Mailer: Apple Mail (2.936) --Apple-Mail-2--338247456 Content-Type: text/plain; charset=WINDOWS-1252; format=flowed; delsp=yes Content-Transfer-Encoding: quoted-printable Brent: Any chance you have a bad ground? On Aug 10, 2011, at 5:01 AM, Lancair Mailing List wrote: > Lancair Mailing List Digest #3478 > > 1) Re: Kind of frustrated because of my AC.. > by Brent Regan > 2) Re: Fw: Re: Re-doing my panel - carefully thinking through failures > by Colyn Case > 3) Re: Re-doing my panel - carefully thinking through failures > by GT Phantom > 4) Re: Trans-Pacific in a 360 > by rwolf99@aol.com > 5) TSOs and equipment failure > by rwolf99@aol.com > 6) Re: Re-doing my panel - carefully thinking through failures > by GT Phantom > 7) Re: Trans Pacific in a Lancair 360 > by GT Phantom > 8) Re: Fw: Re: Re-doing my panel - carefully thinking through failures > by Hamid Wasti > 9) Re: Fw: Re: Re-doing my panel - carefully thinking through failures > by "Michael Newman" > > This digest is sent to you because you are subscribed to > the mailing list . > For archives and help click = http://mail.lancaironline.net:81/Lists/lml/List.html > LML website: http://www.lancaironline.net/maillist.html > > From: Brent Regan > Date: August 9, 2011 6:55:38 AM CDT > To: lml@lancaironline.net > Subject: Re: Kind of frustrated because of my AC.. > > > Ronald laments:<<< > my AC breaker (50AMPS) trips as soon as I get airborne, taxing is =20 > not a problem, run up is ok too. > >>> > > I suspect that my friend Dr. Katz is correct that there is =20 > insufficient cooling for the condenser causing higher overall system =20= > pressure leading to a higher pressure ratio and higher compressor =20 > current, tripping the breaker. > > Other possibilities include: > > Excessive freon charge, leading to a high system pressure. > > Defective expansion valve. > > Defective breaker. > > Poor voltage regulation from the electrical system. High sustained =20 > RPM causes higher voltage leading to higher compressor current. > > Undersized wiring causing a large voltage drop resulting in =20 > compressor stall. > > Poor connection at the breaker leading to resistance heating and =20 > tripping at lower than rated current. > > Low buss voltage caused by gear hydraulic pump (HPU) and AC =20 > compressor running simultaneously. > > Or it could be something else... > > Regards > Brent Regan > > > > > > > > From: Colyn Case > Date: August 9, 2011 6:55:38 AM CDT > To: lml@lancaironline.net > Subject: Re: [LML] Re: Fw: Re: Re-doing my panel - carefully =20 > thinking through failures > > > Hamid, > > that is very helpful. I can see lots of ways that the e bus would =20 > lose power. > > The particular scenario I was worried about was an event on the A =20 > bus reaching the B bus. This would require probably that both =20 > diodes that feed the e bus fail closed with little or no reverse =20 > current protection remaining on the B leg. > > Colyn > > On Aug 8, 2011, at 9:40 PM, Hamid Wasti wrote: > >> Colyn Case wrote: >>> At the risk of topic drift.....I put in those big fat diodes to my =20= >>> essential bus also. >>> Since them I'm wondering if there's a failure mode on one bus that =20= >>> crosses the diodes and takes out the other bus. >> A diode can fail open, shorted or "out of spec" meaning that one or =20= >> more parameters (voltage drop, reverse current, series resistance =20 >> etc) is very high. According to various documents on Failure Mode =20= >> Distribution, about 50% of the failure modes in power diodes result =20= >> in a shorted diode, about 30% in open diode and about 20% in out of =20= >> spec failure. Different sources use different numbers and they vary =20= >> for different components, but that is a ball park to get a sense of =20= >> things. >> >> A shorted diode is basically a direct connection, tying the two =20 >> busses together and essentially making them one. An open diode =20 >> prevents power from going through the diode to the destination =20 >> buss, leaving it permanently isolated from one of its sources. =20 >> Parameter change is an unsustainable state. It may allow the diode =20= >> to function briefly, but with use under load, it will invariably =20 >> fail either open or shorted. >> >> Diodes can fail for many reasons, among them: Over-heating, Over-=20 >> voltage, Over-current. If you have under-sized the diode or not =20 >> properly heat sunk it, it will die after some time in "normal" use. >> >> Heat is generated in a diode's die and is a function of the current =20= >> and the diode's voltage drop (voltage in volts multiplied by =20 >> current in amps =3D power in watts). That heat needs to be conducted =20= >> to the outside of the case, then through some mechanical interface =20= >> to the heat sink and then to the ambient air. If the case to heat =20 >> sink interface is not properly designed and properly implemented, =20 >> the die can be considerably hotter than the heat sink. If the heat =20= >> sink is not receiving cooling air, it can be considerably hotter =20 >> than the ambient air around it. If the air is circulating in a =20 >> closed environment it may be a lot warmer than the outside. If the =20= >> air happens to be low on air molecules (flying at FL280) it may not =20= >> be taking away as much heat as you had tested at sea level. All of =20= >> this can conspire to over-heat the die and lead to failure. >> >> Surely the easiest thing in the world is to make sure that you use =20= >> a diode with a higher current rating than the highest possible =20 >> current in your system. Right? Actually, no! The important part is =20= >> to use the correct current rating, which is not always obvious. The =20= >> headline current rating is valid at a certain temperature, which is =20= >> often (but not always) 25C die temperature. In real life, the die =20 >> is going to be a lot warmer than that, maybe as much as 100C =20 >> warmer. Buried in the datasheet is a graph indicating the maximum =20 >> current at higher temperatures, or a footnote along the lines of =20 >> "Maximum current decreases by .....A per degree C for higher =20 >> temperatures" To know if the diode is going to work for you, you =20 >> need to figure out the maximum power dissipation, figure out the =20 >> temperature increase due to that much power, add that to the =20 >> maximum heat sink temperature and then make sure that it can handle =20= >> the current at that die temperature. The resulting current limit is =20= >> invariably going to be a lot lower than the headline number and if =20= >> you are exceeding that, your diode is under-sized. >> >> If you have battery disconnection on one buss, the alternator can =20 >> generate a voltage spike of several 10's of volts. DO-160 calls for =20= >> 28V certified systems to be able to survive up to a 100mS wide 80V =20= >> spike, followed by 48V for 1 second. If there is an 80V spike on =20 >> the A Buss, while the B Buss stays at 28V, the diode between the =20 >> essential buss and the B Buss will see a voltage of close to 50V. =20 >> Is it rated for that? If you B Buss happens to be off due to a =20 >> failure, the diode is going to see almost the full 80V. Will it =20 >> survive that? If it fails shorted, you just lost your essential =20 >> buss. Unlike over-current, there is no transient specification for =20= >> over-voltage. Even a momentary over-voltage can damage a diode. >> >> Turning off switches and hot-unplugging a high current load can =20 >> cause a flyback voltage due to the inductance of the power wire. =20 >> Unless this is anticipated and protected against, it can kill an =20 >> isolation diode. An intermittent power connection in a tray is the =20= >> same as repeatedly hot-plugging/hot-unplugging. >> >> Finally, a word about the worst kind of failure: The out-of-spec =20 >> failure. Lets say due to one of the aforementioned events, you have =20= >> an out-of-spec failure where the diode's internal resistance =20 >> increases an order of magnitude or more from the original value of =20= >> a few mili-ohms. Lets say you have a system where the "A Buss" and =20= >> "B Buss" feed an essential buss and the diode on the A Buss side =20 >> has failed with high resistance. If you do a system check at every =20= >> startup where you sequentially shut down both busses and make sure =20= >> that the essential buss can run from the remaining one, you are =20 >> likely to find that the essential buss works. The failed diode will =20= >> be able to operate the load for a little bit while it over-heats. =20 >> During normal operation, the diode on the A Buss will take all the =20= >> load. But if you have a failure of the A Buss and all the current =20 >> starts going through this high resistance diode, it is quickly =20 >> going to fail and as Murphy's Law states, there is 100% likelihood =20= >> that this will be one of the 30% of times where it fails open. >> >> I am sure I can think of a few more scenarios where a failure can =20 >> go undetected by typical checks. The bottom line is that unless you =20= >> are willing and able to get into it a lot deeper, a "simple and =20 >> reliable" system may only be half so. >> >> Regards, >> >> Hamid >> >> -- >> For archives and unsub = http://mail.lancaironline.net:81/lists/lml/List.html > > > > > From: GT Phantom > Date: August 9, 2011 6:55:38 AM CDT > To: lml@lancaironline.net > Subject: Re: Re: Re-doing my panel - carefully thinking through =20 > failures > > > Brent, > > I suppose I should have been more specific - I assume that pilots of =20= > experimental aircraft will exercise sufficient judgment not be =20 > flying into thunderstorms, and thus the likelihood of in-flight =20 > lightning strike is nearly nil. Not absolutely nil, naturally, but =20= > approaching or below the likelihood of vacuum failure, which is =20 > fairly common. Of course, perhaps I should not make such an =20 > assumption given that a very famous pilot died just last year flying =20= > his Bonanza into thunderstorms. > > Absent thunderstorms, we will simply have to agree to disagree. =20 > Vacuum pumps and vacuum-operated artificial horizons are notoriously =20= > fallible, and a poor vacuum can give insidious symptoms causing =20 > catastrophic results. While there have been some experimental EFIS =20= > units (notably one you mention, also the original pioneer Blue =20 > Mountain) which had early individual failure rates much higher than =20= > vacuum equipment, still the likelihood of two or more going down =20 > simultaneously is rather rare. In my personal experience my TSO =20 > Garmins failed just as often as my experimental equipment - =20 > anecdotal evidence, to be sure, but 3 TSO failures in 600 hrs not =20 > counting vacuum pump failure and attitude indicator partial failure =20= > ("lazy" attitude, "sort of" working). > > None of this absolves individuals contemplating use of experimental =20= > equipment from the burden of research to draw their own conclusions =20= > about reliability. > > Your statement that TSO is required for legal flight is simply =20 > untrue. If you wish to dispute this, please feel free to point out =20= > the section of the FARs that you believe says otherwise (it does not =20= > exist, but knock yourself out). I don't expect to convince you of =20 > that; it seems that there are some folks who have made up their =20 > minds and aren't interested in anyone else's opinion. That's fine, =20= > you are entitled to yours. I, like many, have reviewed the =20 > pertinent FARs along with (among others) my mechanic who was a chief =20= > avionics safety inspector for a major airline. For the type of =20 > flying for which Experimental aircraft are authorized there is no =20 > such rule stating that each piece of equipment must be certified to =20= > pass TSO. The altimeter must, or pass the test for equivalent =20 > accuracy (performed during the annual pitot-static check). Doesn't =20= > mean it's a bad thing, only unnecessary for legal flight. Just as =20 > you admonish people who are not engineers (I too was a software =20 > engineer by trade) to form unwarranted opinions about avionics, you =20= > too should not consider yourself an expert on FARs simply because =20 > you build avionics. Glass houses, etc. > > Blocked pitot or static tubes are no longer a killer for correct =20 > attitude indication on any of the three leading experimental EFIS =20 > units (GRT, Dynon, MGL). May also not be on others, haven't kept =20 > up. Of course, you will not get accurate airspeed with either =20 > blocked and will not get accurate barometric altitude with static =20 > blocked, but that would happen irrespective of the type of avionics =20= > you use. However, you will still have accurate horizon, and GPS can =20= > provide altitude and ground speed which, combined with a pilot's =20 > knowledge of their aircraft power settings, etc. should enable you =20 > to fly safely to landing. > > At the end of the day, you are putting your own life on the line. =20 > If you feel more comfortable with spinning gyros, by all means load =20= > up. However, if you feel you have done your research and would =20 > rather replace that vacuum pump for a second alternator to prevent =20 > power-out and ditch the gyro for a small self-contained backup EFIS, =20= > then your odds of total failure will ultimately be about the same - =20= > just different causes. > > > Fly safe! > > Bill > > > On 01/-10/-28163 02:59 PM, Brent Regan wrote: >> >> Bill speculates: >> <> than a single vacuum pump, your argument that people must have =20 >> "TSO'd" equipment is logically ridiculous - especially if they also =20= >> have as part of their panel an independent 2-axis autopilot.>> >> >> The primary assumption here is false. It is not "given" that "two =20 >> EFIS units with battery backup are more reliable than a single =20 >> vacuum pump". Analysis and data show the opposite is true. >> >> Having designed several Certified EFIS systems and sensors (AHRS, =20 >> Air Data, Magnetometer, OAT etc.) over the last 15 years and =20 >> shepherded those systems through DO160 certification testing I can =20= >> say with the confidence of having empirical data (Remember that =20 >> one test is worth a thousand expert opinions) that I would NOT fly =20= >> behind a panel that had ONLY electronic gauges, regardless of their =20= >> certification level or lack thereof. Even the Starship, with a =20 >> million dollar 17 tube Pro Line 21 integrated avionics suite, STILL =20= >> has a mechanical Airspeed, Altimeter and AH. >> >> Regan Designs was the first company to design equipment that passed =20= >> the DO160 Lightning Induced Transient Susceptibility (section 22) =20 >> and Lightning Direct Effects (section 23) requirements introduced =20 >> in 2004. Hamid engineered several test articles that he then =20 >> subjected to simulated lightning strikes in a certified =20 >> laboratory. Based on those tests I can say with a high level of =20 >> confidence that most GA certified EFIS and likely all experimental =20= >> EFIS systems will not survive a proximal lightning strike, let =20 >> alone a direct strike. Same goes for experimental autopilots. And =20 >> that is considering just 2 of 26 sections. There is also Shock, =20 >> Vibration, Temperature, Magnet Effect, Voltage Spike, Operational =20 >> Voltage, RF Susceptibility, ESD, etc. etc. etc. >> >> One transient event can take out most of the digital electronics =20 >> wired into the aircraft. A battery back up won't do any good if =20 >> your EFIS is fried. >> >> Here are some additional reasons for a spinning mass backup to an =20 >> EFIS. >> >> 1) Compelling disaster. If your EFIS starts to roll (e.g. due to a =20= >> long climbing departure turn), you feel compelled to follow it to =20 >> your doom. Having a familiar AH in you scan will help you keep you =20= >> wings level. >> 2) Different physics. Spinning mass and MEMS gyroscopes work on =20 >> different principals and physics. The set of events that will kill =20= >> both is small and most of those involve the pilot not surviving =20 >> either. >> 3) Old faithful. Most of us learned to fly with an AH. The response =20= >> to and AH display is nearly reflexive and may save you life during =20= >> a helmet fire. >> >> Some words on TSOs. TSOs are the Technical Standards that equipment =20= >> must meet to to be considered as equipment on aircraft. Therefore, =20= >> in order to have an "altimeter" in your aircraft you must have an =20 >> instrument that meets the TSOs for an "Altimeter". You can either =20 >> let the instrument manufacturer do the testing or, as an aircraft =20 >> manufacturer, you can do the testing, and document same. Why? =20 >> Imagine you took a rock and printed "8,250 feet" on it. You then =20 >> "install" it in your aircraft and claim it is an altimeter as it =20 >> will tell you your altitude during certain conditions of flight. =20 >> One of those conditions must be that you are actually flying at =20 >> 8,250 feet MSL. To prevent this type of thing the FAA has =20 >> established standards that a device must meet in ordered to be =20 >> qualified to function as a required device. See FAR 21.601.b.1. >> >> So, Bill's statement that "...(the) argument that people must have =20= >> "TSO'd" equipment is logically ridiculous..." is false. You MUST =20 >> have at least one of each of the required instruments and they MUST =20= >> meet the TSO. You can call it ridiculous, but it does not change =20 >> the fact that it is the law. >> >> Bill also postulates that " Experimental EFIS units work acceptably =20= >> with either good pitot-static input or GPS input, removing the =20 >> single point of failure in steam gages.". This statement is non =20 >> sequitur. The most common Pitot Static problems are blocked ports =20 >> (insects or ice), leaks or water in the lines, any of which will =20 >> produce a similarly wrong reading in either the steam or electronic =20= >> display. Redundant sensors are fine ONLY if you have a method for =20 >> differentiating good data from bad data. >> >> FWIW, Being a good pilot, as I am sure Bill is, does not make you a =20= >> good engine mechanic or good at failure analysis. You can take or =20 >> ignore the advice of those with experience. Fred has put a lot of =20 >> thought into his system and has reduced the likelihood of a =20 >> catastrophic electrical failure. Now if you could only do the same =20= >> for rocker arms....... >> >> Regards >> Brent Regan >> >> > > > > From: rwolf99@aol.com > Date: August 9, 2011 6:55:38 AM CDT > To: lml@lancaironline.net > Subject: Re: Trans-Pacific in a 360 > > > Greyhawk - > > When I have some real numbers I'll switch to graph paper. I don't =20 > even know what my empty weight is yet -- I was guessing (perhaps =20 > optimistically) 1100 pounds. I also don't know the actual fuel =20 > requirement as a function of airspeed and gross weight. I also only =20= > had rough measurements of a ferry tank capacity. I was mostly =20 > trying to determine whether it was possible at all and whether it =20 > had been done before. > > =46rom what I have been able to determine, it may be doable but is =20 > definitely marginal. Certainly it may be fun to see if I can do it =20= > -- even if I demonstrate it to myself by flying from California to =20 > Massachusetts. > > I had been toying with the idea several years ago, but gave up the =20 > idea since I didn't want to leave my wife without a husband for =20 > something that was really not that important. The risk/benefit just =20= > wasn't there. Now that this is no longer an issue I have been =20 > thinking of it again. You guys have given me some good ideas to =20 > consider, and some data points to gather in my initial flight test =20 > program. > > - Rob Wolf > > > > From: rwolf99@aol.com > Date: August 9, 2011 6:55:38 AM CDT > To: lml@lancaironline.net > Subject: TSOs and equipment failure > > > Hamid writes -- > > < batteries and isolated/redundant busses, a TSO's system and a non-=20 > TSO's system can equally survive an adverse event like a lightning =20 > induced power surge or an alternator caused voltage surge. I would =20 > strongly disagree with your conclusion.>> > Actually I agree completely with Hamid. Environmental effects such =20= > as the indirect effects of lightning are precisely where the TSO'd =20 > units have an advantage. With my electrical power example I was =20 > trying to say that there are other failure modes (loss of electrical =20= > power for a variety of reasons) where the TSO'd unit goes dark just =20= > like the non-TSOd unit. > > I did envision electrical power surges due to failures in the =20 > electrical system causing the non-TSOd unit to fail which the TSOd =20 > unit might survive. In this case, Hamid is right -- the TSOd unit =20 > has an advantage here as well. The lesson is that problems with the =20= > fairly mundane portion of our avionics systems (electrical power =20 > generation and distribution) can also cause failures of our whiz-=20 > bang EFISs and glass panel displays. It doesn't take a lightning =20 > strike. > > - Rob Wolf > Steam gauges in my airplane! > > > > From: GT Phantom > Date: August 9, 2011 6:55:38 AM CDT > To: lml@lancaironline.net > Subject: Re: Re: Re-doing my panel - carefully thinking through =20 > failures > > > I don't doubt that, taken in aggregate, experimental avionics =20 > experience failure more often than TSO equipment. > > My point was that people who make blanket statements suggesting =20 > people should not use experimental equipment at all are drawing the =20= > wrong conclusion (and thus giving others bad advice). That =20 > conclusion is using the same gross generalization behaviors as a =20 > small child that once burns themselves on the stove and then draws =20 > the (incorrect) generalization that "all stoves are bad." In =20 > reality it's not that stoves are bad; simply that you must be =20 > careful in their use. > > All avionics can be compared to light bulbs. Cheap ones tend to =20 > burn out quicker than expensive ones, but there are always counter-=20 > examples (expensive ones going out sooner, cheap ones lasting =20 > longer). The key is, if you have lots of bulbs you won't be in the =20= > dark when one fails. > > Cheers, > > Bill > > On 01/-10/-28163 02:59 PM, rwolf99@aol.com wrote: >> >> <> batteries and internal automatic isolation circuitry are about as =20 >> fail-proof as a single piece of electronic equipment can get.>> >> >> This is not Brent's statement. Rather, this relates to a =20 >> suggestion that non-TSOd units should be considered equally =20 >> reliable as TSOd units, which is something that Brent disagrees with. >> >> I think Brent is saying that a device that has successfully passes =20= >> environmental qualification testing (a TSOd unit) is way less =20 >> likely to fail than a unit which has not. His first-hand =20 >> experience taking an experimental system through this process =20 >> (Sieera Flight Systems, now Chelton) bears this out. Such units =20 >> are most likely more resilient to power fluctuation, temperature =20 >> extremes, shock and vibration, and even exposure to water. In this =20= >> sense, the TSOd unit is more reliable. >> >> Having said that, no electronic unit will work without power. Now =20= >> you look at internal backup batteries, redundant power sources, =20 >> multiple generators/alternators, duplicate paths for power, no =20 >> single point failures, and perhaps other things which are totally =20 >> separate from the unit itself. In this sense, the non-TSOd unit =20 >> and the TSOd unit are equally reliable. >> >> Just my two cents... >> >> - Rob Wolf >> >> p.s. I'm using a vacuum pump and steam gauges. I don't need no =20 >> stinkin' electricity.... (But then, if the weather is really bad -- =20= >> like it's raining -- I stay on the ground. YMMV) > > > > From: GT Phantom > Date: August 9, 2011 6:55:38 AM CDT > To: lml@lancaironline.net > Subject: Re: Trans Pacific in a Lancair 360 > > > While it is certainly do-able, one has to question why you would =20 > take the risk if you're not trying to break some record? > > Take the wings off, carefully pack the entire airplane (and anything =20= > else you will be wanting in Hawaii) in a shipping container, and =20 > ship it. Probably won't cost much more than flying it, and with no =20= > risk to yourself. > > Blue skies, > > Bill > > > On 01/-10/-28163 02:59 PM, rwolf99@aol.com wrote: >> >> I'm running the numbers for a ferry tank to take my Lancair 360 =20 >> from California (probably Watsonville) to Hawaii. My back-of-the-=20 >> envelope calculations suggest that I can do this with a GTOW of =20 >> 2000 or 2100 pounds and have the range for 2100 nmi with a 30 kt =20 >> headwind (no reserves). >> >> Has anyone made this trip before in a 320 or a 360? I know a few =20 >> IVs have done it. >> >> Needless to say, the shakedown flights will be the other way -- =20 >> California to Boston, or something like that. >> >> - Rob Wolf >> > > > > From: Hamid Wasti > Date: August 9, 2011 6:55:38 AM CDT > To: lml@lancaironline.net > Subject: Re: [LML] Re: Fw: Re: Re-doing my panel - carefully =20 > thinking through failures > > > Correcting a typo in my previous e-mail. The changes in the new =20 > paragraph are highlighted. > > Hamid Wasti wrote: >> Lets say you have a system where the "A Buss" and "B Buss" feed an =20= >> essential buss and the diode on the A Buss side has failed with =20 >> high resistance. If you do a system check at every startup where =20 >> you sequentially shut down both busses and make sure that the =20 >> essential buss can run from the remaining one, you are likely to =20 >> find that the essential buss works. The failed diode will be able =20 >> to operate the load for a little bit while it over-heats. During =20 >> normal operation, the diode on the A Buss will take all the load. =20 >> But if you have a failure of the A Buss and all the current starts =20= >> going through this high resistance diode, it is quickly going to =20 >> fail and as Murphy's Law states, there is 100% likelihood that this =20= >> will be one of the 30% of times where it fails open. > Lets say you have a system where the "A Buss" and "B Buss" feed an =20 > essential buss and the diode on the _*B Buss*_ side has failed with =20= > high resistance. If you do a system check at every startup where you =20= > sequentially shut down both busses and make sure that the essential =20= > buss can run from the remaining one, you are likely to find that the =20= > essential buss works. The failed diode will be able to operate the =20 > load for a little bit while it over-heats. During normal operation, =20= > the _*good*_ diode on the A Buss will take all the load. But if you =20= > have a failure of the A Buss and all the current starts going =20 > through this high resistance diode _*from the B Buss*_, it is =20 > quickly going to fail and as Murphy's Law states, there is 100% =20 > likelihood that this will be one of the 30% of times where it fails =20= > open. > > Regards, > > Hamid > > > > > From: "Michael Newman" > Date: August 9, 2011 6:55:38 AM CDT > To: lml@lancaironline.net > Subject: RE: [LML] Re: Fw: Re: Re-doing my panel - carefully =20 > thinking through failures > > > You have a pretty good setup BUT=85 > > I had an avionics master breaker (switch type) in my Bonanza that =20 > failed. What happened was that the housing cracked behind the panel. =20= > The switch failed open on an IFR flight when the housing was no =20 > longer able to hold the contacts together. Your DPST switch can fail =20= > in the same way and will fail open. Both sides will be open from =20 > this common mechanical cause. > > My solution was to put in two separate breaker switches in parallel. =20= > I turn only one on at a time. If one fails I can simply turn on the =20= > other. > > From: Bill Harrelson [mailto:n5zq@verizon.net] > Sent: Sunday, August 07, 2011 10:57 AM > To: lml@lancaironline.net > Subject: Re: [LML] Re: Fw: Re: Re-doing my panel - carefully =20 > thinking through failures > > > Bill, > > > > My avionics switch is a DPST switch. Basically two switches in one. =20= > Each side controls the power feed from one electrical system. Sure, =20= > both sides of the switch could fail at the same time but that would =20= > be unlikely. On top of that I have a separate, isolated switch that =20= > feeds power only to the GPS/Com so that even if both sides of the =20 > avionics switch should fail or both electrical system 1 and 2 fail, =20= > I can power this unit from system 3. System 3 is an 8 amp B&C =20 > generator and an Odyssey 545 battery. > > > > Bill Harrelson > > N5ZQ 320 1,950 hrs > > N6ZQ IV under construction > > > > > > > > Fred, > > Even with all the extra weight and redundancy, your avionics are all =20= > reliant on a single switch. If that $7 switch goes, your plane is =20 > blind, deaf, and dumb! The aeroelectric list does not recommend an =20= > avionics buss. This is part of the reason for that. > > Bill B > > > --Apple-Mail-2--338247456 Content-Type: text/html; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Brent: Any chance you have a = bad ground?
On Aug 10, 2011, at 5:01 AM, Lancair Mailing = List wrote:

       Lancair Mailing = List Digest #3478

1) Re: Kind of frustrated because of my = AC..
   by Brent Regan <brent@regandesigns.com>
= 2) Re: Fw: Re: Re-doing my panel - carefully thinking through = failures
   by Colyn Case <colyncase@earthlink.net> 3) Re: Re-doing my panel - carefully thinking through failures
=    by GT Phantom <gt_phantom@hotmail.com>
= 4) Re: Trans-Pacific in a 360
   by rwolf99@aol.com
5) TSOs and = equipment failure
   by rwolf99@aol.com
6) Re: Re-doing = my panel - carefully thinking through failures
   by = GT Phantom <gt_phantom@hotmail.com>
= 7) Re: Trans Pacific in a Lancair 360
   by GT = Phantom <gt_phantom@hotmail.com>
= 8) Re: Fw: Re: Re-doing my panel - carefully thinking through = failures
   by Hamid Wasti <hwasti@lm50.com>
9) Re: Fw: = Re: Re-doing my panel - carefully thinking through failures
=    by "Michael Newman" <mnewman@dragonnorth.com>
This digest is sent to you because you are subscribed to
=  the mailing list <lml@lancaironline.net>.
Fo= r archives and help click http://mail.= lancaironline.net:81/Lists/lml/List.html
LML website: http://www.lancaironli= ne.net/maillist.html

From: Brent Regan <brent@regandesigns.com>
<= /span>
Date: August 9, 2011 6:55:38 AM CDT
Subject: = Re: Kind of frustrated because of my = AC..


Ronald laments:<<<
my AC = breaker (50AMPS)  trips as soon as I get airborne, taxing is not a = problem, run up is ok too.
>>>

I suspect that my = friend Dr. Katz is correct that there is insufficient cooling for the = condenser causing higher overall system pressure leading to a higher = pressure ratio and higher compressor current, tripping the = breaker.

Other possibilities include:

Excessive freon = charge, leading to a high system pressure.

Defective expansion = valve.

Defective breaker.

Poor voltage regulation from the = electrical system. High sustained RPM causes higher voltage leading to = higher compressor current.

Undersized wiring causing a large = voltage drop resulting in compressor stall.

Poor connection at = the breaker leading to resistance heating and tripping at lower than = rated current.

Low buss voltage caused by gear hydraulic pump = (HPU) and AC compressor running simultaneously.

Or it could be = something else...

Regards
Brent = Regan







From: Colyn Case <colyncase@earthlink.net>
Date: August 9, 2011 6:55:38 AM CDT
Subject: = Re: [LML] Re: Fw: Re: Re-doing my panel - = carefully thinking through = failures


Hamid,

that is very helpful. =  I can see lots of ways that the e bus would lose power.

The = particular scenario I was worried about was an event on the A bus = reaching the B bus.   This would require probably that both = diodes that feed the e bus fail closed with little or no reverse current = protection remaining on the B leg.

Colyn

On Aug 8, 2011, = at 9:40 PM, Hamid Wasti wrote:

Colyn = Case wrote:
At the risk of topic drift.....I put in those big fat = diodes to my essential bus = also.
Since them I'm wondering if there's a failure mode on one = bus that crosses the diodes and takes out the other = bus.
A diode can = fail open, shorted or "out of spec" meaning that one or more parameters = (voltage drop, reverse current, series resistance etc) is very high. =  According to various documents on Failure Mode Distribution, about = 50% of the failure modes in power diodes result in a shorted diode, = about 30% in open diode and about 20% in out of spec failure. Different = sources use different numbers and they vary for different components, = but that is a ball park to get a sense of = things.

A shorted diode = is basically a direct connection, tying the two busses together and = essentially making them one. An open diode prevents power from going = through the diode to the destination buss, leaving it permanently = isolated from one of its sources. Parameter change is an unsustainable = state. It may allow the diode to function briefly, but with use under = load, it will invariably fail either open or = shorted.

Diodes can fail = for many reasons, among them: Over-heating, Over-voltage, Over-current. = If you have under-sized the diode or not properly heat sunk it, it will = die after some time in "normal" use.

Heat is = generated in a diode's die and is a function of the current and the = diode's voltage drop (voltage in volts multiplied by current in amps =3D = power in watts). That heat needs to be conducted to the outside of the = case, then through some mechanical interface to the heat sink and then = to the ambient air. If the case to heat sink interface is not properly = designed and properly implemented, the die can be considerably hotter = than the heat sink. If the heat sink is not receiving cooling air, it = can be considerably hotter than the ambient air around it. If the air is = circulating in a closed environment it may be a lot warmer than the = outside. If the air happens to be low on air molecules (flying at FL280) = it may not be taking away as much heat as you had tested at sea level. = All of this can conspire to over-heat the die and lead to = failure.

Surely the = easiest thing in the world is to make sure that you use a diode with a = higher current rating than the highest possible current in your system. = Right? Actually, no!  The important part is to use the correct = current rating, which is not always obvious. The headline current rating = is valid at a certain temperature, which is often (but not always) 25C = die temperature. In real life, the die is going to be a lot warmer than = that, maybe as much as 100C warmer. Buried in the datasheet is a graph = indicating the maximum current at higher temperatures, or a footnote = along the lines of "Maximum current decreases by  .....A per degree = C for higher temperatures"  To know if the diode is going to work = for you, you need to figure out the maximum power dissipation, figure = out the temperature increase due to that much power, add that to the = maximum heat sink temperature and then make sure that it can handle the = current at that die temperature. The resulting current limit is = invariably going to be a lot lower than the headline number and if you = are exceeding that, your diode is = under-sized.

If you have = battery disconnection on one buss, the alternator can generate a voltage = spike of several 10's of volts. DO-160 calls for 28V certified systems = to be able to survive up to a 100mS wide 80V spike, followed by 48V for = 1 second. If there is an 80V spike on the A Buss, while the B Buss stays = at 28V, the diode between the essential buss and the B Buss will see a = voltage of close to 50V. Is it rated for that? If you B Buss happens to = be off due to a failure, the diode is going to see almost the full 80V. = Will it survive that? If it fails shorted, you just lost your essential = buss. Unlike over-current, there is no transient specification for = over-voltage. Even a momentary over-voltage can damage a = diode.

Turning off = switches and hot-unplugging a high current load can cause a flyback = voltage due to the inductance of the power wire. Unless this is = anticipated and protected against, it can kill an isolation diode. An = intermittent power connection in a tray is the same as repeatedly = hot-plugging/hot-unplugging.

Finally, a word = about the worst kind of failure: The out-of-spec failure. Lets say due = to one of the aforementioned events, you have an out-of-spec failure = where the diode's internal resistance increases an order of magnitude or = more from the original value of a few mili-ohms. Lets say you have a = system where the "A Buss" and "B Buss" feed an essential buss and the = diode on the A Buss side has failed with high resistance. If you do a = system check at every startup where you sequentially shut down both = busses and make sure that the essential buss can run from the remaining = one, you are likely to find that the essential buss works. The failed = diode will be able to operate the load for a little bit while it = over-heats. During normal operation, the diode on the A Buss will take = all the load. But if you have a failure of the A Buss and all the = current starts going through this high resistance diode, it is quickly = going to fail and as Murphy's Law states, there is 100% likelihood that = this will be one of the 30% of times where it fails = open.

I am sure I can = think of a few more scenarios where a failure can go undetected by = typical checks. The bottom line is that unless you are willing and able = to get into it a lot deeper, a "simple and reliable" system may only be = half so.

Regards,

Hamid

--
For archives = and unsub http://mail.= lancaironline.net:81/lists/lml/List.html



<= br>
From: GT Phantom <gt_phantom@hotmail.com>
<= /span>
Date: August 9, 2011 6:55:38 AM CDT
Subject: = Re: Re: Re-doing my panel - carefully thinking = through failures


=
Brent,

I = suppose I should have been more specific - I assume that pilots of = experimental aircraft will exercise sufficient judgment not be flying = into thunderstorms, and thus the likelihood of in-flight lightning = strike is nearly nil.  Not absolutely nil, naturally, but = approaching or below the likelihood of vacuum failure, which is = fairly common.  Of course, perhaps I should not make such an = assumption given that a very famous pilot died just last year flying = his Bonanza into thunderstorms.

Absent thunderstorms, we = will simply have to agree to disagree.  Vacuum pumps and = vacuum-operated artificial horizons are notoriously fallible, and a = poor vacuum can give insidious symptoms causing catastrophic = results.  While there have been some experimental EFIS = units (notably one you mention, also the original pioneer Blue = Mountain) which had early individual failure rates much higher than = vacuum equipment, still the likelihood of two or more going down = simultaneously is rather rare.  In my personal experience my TSO = Garmins failed just as often as my experimental equipment - anecdotal = evidence, to be sure, but 3 TSO failures in 600 hrs not counting = vacuum pump failure and attitude indicator partial failure ("lazy" = attitude, "sort of" working).

None of this absolves = individuals contemplating use of experimental equipment from the = burden of research to draw their own conclusions about = reliability.

Your statement that TSO is required for = legal flight is simply untrue.  If you wish to dispute this, = please feel free to point out the section of the FARs that you = believe says otherwise (it does not exist, but knock yourself = out).  I don't expect to convince you of that; it seems that = there are some folks who have made up their minds and aren't = interested in anyone else's opinion.  That's fine, you are = entitled to yours.  I, like many, have reviewed the pertinent = FARs along with (among others) my mechanic who was a chief avionics = safety inspector for a major airline.  For the type of flying = for which Experimental aircraft are authorized there is no such rule = stating that each piece of equipment must be certified to pass = TSO.  The altimeter must, or pass the test for equivalent = accuracy (performed during the annual pitot-static check).  Doesn't = mean it's a bad thing, only unnecessary for legal flight.  Just = as you admonish people who are not engineers (I too was a software = engineer by trade) to form unwarranted opinions about avionics, you = too should not consider yourself an expert on FARs simply because you = build avionics.  Glass houses, etc.

Blocked pitot or = static tubes are no longer a killer for correct attitude indication = on any of the three leading experimental EFIS units (GRT, Dynon, = MGL).  May also not be on others, haven't kept up.  Of = course, you will not get accurate airspeed with either blocked and = will not get accurate barometric altitude with static blocked, but = that would happen irrespective of the type of avionics you use.  = However, you will still have accurate horizon, and GPS can provide = altitude and ground speed which, combined with a pilot's knowledge of = their aircraft power settings, etc. should enable you to fly safely = to landing. 

At the end of the day, you are putting = your own life on the line.  If you feel more comfortable with = spinning gyros, by all means load up.  However, if you feel you = have done your research and would rather replace that vacuum pump for = a second alternator to prevent power-out and ditch the gyro for a = small self-contained backup EFIS, then your odds of total failure = will ultimately be about the same - just different causes.
=

Fly safe!

Bill


On = 01/-10/-28163 02:59 PM, Brent Regan wrote:
= Bill speculates:
<<Given that = two EFIS units with battery backup are more reliable than a = single vacuum pump, your argument that people must have = "TSO'd" equipment is logically ridiculous - especially if they = also have as part of their panel an independent 2-axis = autopilot.>>

The primary assumption here is = false. It is not "given" that "two EFIS units with battery = backup are more reliable than a single vacuum pump". Analysis = and data show the opposite is true.

Having designed = several Certified EFIS systems and sensors (AHRS, Air Data, = Magnetometer, OAT etc.) over the last 15 years and shepherded = those systems through DO160 certification testing I can say with = the confidence of having empirical  data (Remember that one = test is worth a thousand expert opinions) that I would NOT fly = behind a panel that had ONLY electronic gauges, regardless of = their certification level or lack thereof. Even the Starship, = with a million dollar 17 tube Pro Line 21 integrated avionics = suite, STILL has a mechanical Airspeed, Altimeter and AH.
=
Regan Designs was the first company to design equipment = that passed the DO160 Lightning Induced Transient = Susceptibility (section 22) and Lightning Direct Effects (section = 23) requirements introduced in 2004.  Hamid engineered = several test articles that he then subjected to simulated lightning = strikes in a certified laboratory.  Based on those tests = I can say with a high level of confidence that most GA certified = EFIS and likely all experimental EFIS systems will not survive a = proximal lightning strike, let alone a direct strike. Same goes for = experimental autopilots. And that is considering just 2 of  26 = sections. There is also Shock, Vibration, Temperature, Magnet = Effect, Voltage Spike, Operational Voltage, RF Susceptibility, = ESD,  etc. etc. etc.

One transient = event can take out most of the digital electronics wired into = the aircraft. A battery back up won't do any good if your EFIS is = fried.

Here are some additional reasons for a = spinning mass backup to an EFIS.

1) Compelling = disaster. If your EFIS starts to roll (e.g. due to a long = climbing departure turn), you feel compelled to follow it to your = doom. Having a familiar AH in you scan will help you keep you wings = level.
2) Different physics. Spinning mass and MEMS = gyroscopes work on different principals and physics. The set of = events that will kill both is small and most of those involve = the pilot not surviving either.
3) Old faithful. Most of us = learned to fly with an AH. The response to and AH display is = nearly reflexive and may save you life during a helmet fire.
=
Some words on TSOs. TSOs are the Technical Standards that = equipment must meet to to be considered as equipment on aircraft. = Therefore, in order to have an "altimeter" in your aircraft = you must have an instrument that meets the TSOs for an "Altimeter". = You can either let the instrument manufacturer do the testing = or, as an aircraft manufacturer, you can do the testing, and = document same. Why? Imagine you took a rock and printed "8,250 = feet" on it. You then "install" it in your aircraft and claim = it is an altimeter as it will tell you your altitude during = certain conditions of flight. One of those conditions must be = that you are actually flying at 8,250 feet MSL. To prevent this = type of thing the FAA has established standards that a device must = meet in ordered to be qualified to function as a required device. = See FAR 21.601.b.1.

So, Bill's statement = that "...(the) argument that people must have "TSO'd" = equipment is logically ridiculous..." is false. You MUST have = at least one of each of the required instruments and they MUST = meet the TSO. You can call it ridiculous, but it does not change = the fact that it is the law.

Bill also = postulates that " Experimental EFIS units work acceptably with = either good pitot-static input or GPS input, removing = the single point of failure in steam gages.". This statement = is non sequitur. The most common Pitot Static problems are blocked = ports (insects or ice), leaks or water in the lines, any of which = will produce a similarly wrong reading in either the steam or = electronic display. Redundant sensors are fine ONLY if you have a = method for differentiating good data from bad data.

= FWIW, Being a good pilot, as I am sure Bill is, does not make you = a good engine mechanic or good at failure analysis. You can take = or ignore the advice of those with experience. Fred has put a lot = of thought into his system and has reduced the likelihood of a = catastrophic electrical failure. Now if you could only do the same = for rocker arms.......

Regards
Brent = Regan





Date: August 9, 2011 = 6:55:38 AM CDT
Subject: = Re: Trans-Pacific in a = 360


Greyhawk -
 
When I have = some real numbers I'll switch to graph paper.  I don't even know = what my empty weight is yet -- I was guessing (perhaps optimistically) = 1100 pounds.  I also don't know the actual fuel requirement as a = function of airspeed and gross weight.  I also only had rough = measurements of a ferry tank capacity.  I was mostly trying to = determine whether it was possible at all and whether it had been done = before.
 
=46rom what I have been able to = determine, it may be doable but is definitely marginal.  Certainly = it may be fun to see if I can do it -- even if I demonstrate it to = myself by flying from California to Massachusetts.  
=
 
I had been toying with the idea several years = ago, but gave up the idea since I didn't want to leave my wife without a = husband for something that was really not that important.  The = risk/benefit just wasn't there.  Now that this is no longer an = issue I have been thinking of it again.  You guys have given me = some good ideas to consider, and some data points to gather in my = initial flight test program.
 
- Rob = Wolf



Date: August 9, 2011 = 6:55:38 AM CDT
Subject: = TSOs and equipment = failure


Hamid writes --
 
<<What you are saying is that in a system = with multiple alternator/batteries and isolated/redundant busses, a = TSO's system and a non-TSO's system can equally survive an adverse event = like a lightning induced power surge or an alternator caused voltage = surge. I would strongly disagree with your = conclusion.>>
Actually I agree completely = with Hamid.  Environmental effects such as the indirect effects of = lightning are precisely where the TSO'd units have an advantage.  = With my electrical power example I was trying to say that there are = other failure modes (loss of electrical power for a variety of reasons) = where the TSO'd unit goes dark just like the non-TSOd unit.
=
 
I did envision electrical power surges due = to failures in the electrical system causing the non-TSOd unit to fail = which the TSOd unit might survive.  In this case, Hamid is right -- = the TSOd unit has an advantage here as well.  The lesson is that = problems with the fairly mundane portion of our avionics systems = (electrical power generation and distribution) can also cause failures = of our whiz-bang EFISs and glass panel displays.  It doesn't take a = lightning strike.
 
- Rob Wolf
=
Steam gauges in my airplane!



From: GT Phantom <gt_phantom@hotmail.com>
<= /span>
Date: August 9, 2011 6:55:38 AM CDT
Subject: = Re: Re: Re-doing my panel - carefully thinking = through failures


=
I don't doubt that, = taken in aggregate, experimental avionics experience failure more = often than TSO equipment. 

My point was that people = who make blanket statements suggesting people should not use = experimental equipment at all are drawing the wrong conclusion (and = thus giving others bad advice).  That conclusion is using the = same gross generalization behaviors as a small child that once burns = themselves on the stove and then draws the (incorrect) generalization = that "all stoves are bad."  In reality it's not that stoves are = bad; simply that you must be careful in their use.

All = avionics can be compared to light bulbs.  Cheap ones tend to = burn out quicker than expensive ones, but there are always = counter-examples (expensive ones going out sooner, cheap ones lasting = longer).  The key is, if you have lots of bulbs you won't be in = the dark when one fails.

Cheers,

Bill
=
On 01/-10/-28163 02:59 PM, rwolf99@aol.com wrote: =
=
<<Modern electronic EFIS systems properly installed = with backup batteries and internal automatic isolation = circuitry are about as fail-proof as a single piece of = electronic equipment can get.>>
 
=
This is not Brent's statement.  Rather, this relates to a = suggestion that non-TSOd units should be considered equally = reliable as TSOd units, which is something that Brent = disagrees with.
 
I think Brent = is saying that a device that has successfully passes = environmental qualification testing (a TSOd unit) is = way less likely to fail than a unit which has not.  His = first-hand experience taking an experimental system through = this process (Sieera Flight Systems, now Chelton) bears this = out.  Such units are most likely more resilient to power = fluctuation, temperature extremes, shock and vibration, and = even exposure to water.  In this sense, the TSOd unit is more = reliable.
 
Having said = that, no electronic unit will work without power.  Now you = look at internal backup batteries, redundant power sources, = multiple generators/alternators, duplicate paths for power, no = single point failures, and perhaps other things which are = totally separate from the unit itself.  In this sense, the = non-TSOd unit and the TSOd unit are equally reliable.
=
 
Just my two cents...
=
 
- Rob Wolf
 
=
p.s. I'm using a vacuum pump and steam gauges.  I don't = need no stinkin' electricity.... (But then, if the weather is = really bad -- like it's raining -- I stay on the = ground.  YMMV)
 =



From: GT Phantom <gt_phantom@hotmail.com>
<= /span>
Date: August 9, 2011 6:55:38 AM CDT
Subject: = Re: Trans Pacific in a Lancair = 360


While it is certainly do-able, = one has to question why you would take the risk if you're not trying = to break some record?

Take the wings off, carefully pack = the entire airplane (and anything else you will be wanting in Hawaii) = in a shipping container, and ship it.  Probably won't cost much = more than flying it, and with no risk to yourself.

= Blue skies,

Bill


On 01/-10/-28163 = 02:59 PM, rwolf99@aol.com wrote: =
=
I'm running the numbers for a ferry tank to take my Lancair = 360 from California (probably Watsonville) to Hawaii.  My = back-of-the-envelope calculations suggest that I can do this = with a GTOW of 2000 or 2100 pounds and have the range for 2100 = nmi with a 30 kt headwind (no reserves).
 
=
Has anyone made this trip before in a 320 or a 360?  I = know a few IVs have done it.
 
=
Needless to say, the shakedown flights will be the other = way -- California to Boston, or something like that.
=
 
- Rob Wolf

=



From: Hamid Wasti <hwasti@lm50.com>
Date: August 9, 2011 = 6:55:38 AM CDT
Subject: = Re: [LML] Re: Fw: Re: Re-doing my panel - = carefully thinking through = failures


Correcting a typo in my previous = e-mail. The changes in the new paragraph are highlighted.

Hamid = Wasti wrote:
Lets say you have a system = where the "A Buss" and "B Buss" feed an essential buss and the diode on = the A Buss side has failed with high resistance. If you do a system = check at every startup where you sequentially shut down both busses and = make sure that the essential buss can run from the remaining one, you = are likely to find that the essential buss works. The failed diode will = be able to operate the load for a little bit while it over-heats. During = normal operation, the diode on the A Buss will take all the load. But if = you have a failure of the A Buss and all the current starts going = through this high resistance diode, it is quickly going to fail and as = Murphy's Law states, there is 100% likelihood that this will be one of = the 30% of times where it fails open.
Lets say you have = a system where the "A Buss" and "B Buss" feed an essential buss and the = diode on the _*B Buss*_ side has failed with high resistance. If you do = a system check at every startup where you sequentially shut down both = busses and make sure that the essential buss can run from the remaining = one, you are likely to find that the essential buss works. The failed = diode will be able to operate the load for a little bit while it = over-heats. During normal operation, the _*good*_ diode on the A Buss = will take all the load. But if you have a failure of the A Buss and all = the current starts going through this high resistance diode _*from the B = Buss*_, it is quickly going to fail and as Murphy's Law states, there is = 100% likelihood that this will be one of the 30% of times where it fails = open.

Regards,

Hamid




From: "Michael Newman" = <mnewman@dragonnorth.com>
Date: August 9, 2011 6:55:38 AM CDT
Subject: = RE: [LML] Re: Fw: Re: Re-doing my panel - = carefully thinking through failures


You have a pretty good setup = BUT=85

I had an avionics master breaker (switch type) in = my Bonanza that failed. What happened was that the housing cracked = behind the panel. The switch failed open on an IFR flight when the = housing was no longer able to hold the contacts together. Your DPST = switch can fail in the same way and will fail open. Both sides will be = open from this common mechanical cause.

My solution was to put in two separate breaker = switches in parallel. I turn only one on at a time. If one fails I can = simply turn on the other.

From: Bill Harrelson [mailto:n5zq@verizon.net] =
Sent: Sunday, August 07, 2011 10:57 AM
To: lml@lancaironline.net
Subj= ect: Re: [LML] Re: Fw: Re: Re-doing my panel - carefully thinking = through failures

 

Bill,

 

My avionics switch is a = DPST switch. Basically two switches in one. Each side controls the power = feed from one electrical system. Sure, both sides of the switch could = fail at the same time but that would be unlikely. On top of that I have = a separate, isolated switch that feeds power only to the GPS/Com so that = even if both sides of the avionics switch should fail or both electrical = system 1 and 2 fail, I can power this unit from system 3. System 3 is an = 8 amp B&C generator and an Odyssey 545 battery.

 

Bill = Harrelson

N5ZQ 320 1,950 = hrs

N6ZQ  IV under = construction

 

 

 <= /p>

Fred,

Even with all the extra weight and redundancy, your = avionics are all reliant on a single switch.  If that $7 switch = goes, your plane is blind, deaf, and dumb!  The aeroelectric list = does not recommend an avionics buss.  This is part of the reason = for that.

Bill B




= --Apple-Mail-2--338247456--