X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Sender: To: lml@lancaironline.net Date: Sun, 14 Aug 2011 09:27:37 -0400 Message-ID: X-Original-Return-Path: Received: from [75.8.203.81] (HELO JSFS01.johnstone.local) by logan.com (CommuniGate Pro SMTP 5.4.1) with ESMTPS id 5091188 for lml@lancaironline.net; Sat, 13 Aug 2011 16:21:01 -0400 Received-SPF: none receiver=logan.com; client-ip=75.8.203.81; envelope-from=Dan.Kalmbach@johnstonesupply.com Received: from JSFS01.johnstone.local ([fe80::a088:e182:b674:83f2]) by JSFS01.johnstone.local ([fe80::a088:e182:b674:83f2%10]) with mapi; Sat, 13 Aug 2011 13:20:25 -0700 From: Dan Kalmbach X-Original-To: Lancair Mailing List X-Original-Date: Sat, 13 Aug 2011 13:20:24 -0700 Subject: RE: [LML] AC Problem Thread-Topic: [LML] AC Problem Thread-Index: AcxXV7FKC4fU6UTORpqhaVDGgih86gCndyVA X-Original-Message-ID: References: In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: acceptlanguage: en-US Content-Type: multipart/alternative; boundary="_000_FC122468DE4AAC4CAEBE2F06CC7B521A1948509539JSFS01johnsto_" MIME-Version: 1.0 --_000_FC122468DE4AAC4CAEBE2F06CC7B521A1948509539JSFS01johnsto_ Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable I was just reading about a circuit breaker problem on the air conditioning = unit on a Lancair aircraft. I am an air conditioning contractor by trade an= d a Lancair builder for fun. I would like to know if the a/c ( air conditio= ning ) problem has been resolved or if someone is still looking for further= feedback. I can be reached by cell phone at 559-313-9114. Sorry, but I do = not live and breathe by computer driven E-Mail. Cell phone works best. Dan = Kalmbach From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Wayn= e Marshall Sent: Wednesday, August 10, 2011 5:13 AM To: lml@lancaironline.net Subject: [LML] AC Problem 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 not a pr= oblem, run up is ok too. >>> I suspect that my friend Dr. Katz is correct that there is insufficient coo= ling 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 caus= es higher voltage leading to higher compressor current. Undersized wiring causing a large voltage drop resulting in compressor stal= l. Poor connection at the breaker leading to resistance heating and tripping a= t lower than rated current. Low buss voltage caused by gear hydraulic pump (HPU) and AC compressor runn= ing 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 thinking throu= gh failures Hamid, that is very helpful. I can see lots of ways that the e bus would lose pow= er. The particular scenario I was worried about was an event on the A bus reach= ing 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 o= n 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 essentia= l 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 pa= rameters (voltage drop, reverse current, series resistance etc) is very hig= h. According to various documents on Failure Mode Distribution, about 50% = of the failure modes in power diodes result in a shorted diode, about 30% i= n open diode and about 20% in out of spec failure. Different sources use di= fferent 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 toge= ther and essentially making them one. An open diode prevents power from goi= ng through the diode to the destination buss, leaving it permanently isolat= ed 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 i= nvariably fail either open or shorted. Diodes can fail for many reasons, among them: Over-heating, Over-voltage, O= ver-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 p= ower 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 am= bient 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 hot= ter than the ambient air around it. If the air is circulating in a closed e= nvironment it may be a lot warmer than the outside. If the air happens to b= e 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 syst= em. Right? Actually, no! The important part is to use the correct current = rating, which is not always obvious. The headline current rating is valid a= t a certain temperature, which is often (but not always) 25C die temperatur= e. In real life, the die is going to be a lot warmer than that, maybe as mu= ch as 100C warmer. Buried in the datasheet is a graph indicating the maximu= m current at higher temperatures, or a footnote along the lines of "Maximum= current decreases by .....A per degree C for higher temperatures" To kno= w 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 po= wer, 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 li= mit is invariably going to be a lot lower than the headline number and if y= ou 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 sy= stems to be able to survive up to a 100mS wide 80V spike, followed by 48V f= or 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 vol= tage 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 s= urvive 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 fly= back voltage due to the inductance of the power wire. Unless this is antici= pated and protected against, it can kill an isolation diode. An intermitten= t power connection in a tray is the same as repeatedly hot-plugging/hot-unp= lugging. Finally, a word about the worst kind of failure: The out-of-spec failure. L= ets say due to one of the aforementioned events, you have an out-of-spec fa= ilure 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 sy= stem where the "A Buss" and "B Buss" feed an essential buss and the diode o= n 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 sur= e 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 opera= te 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 o= f 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 undete= cted 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 b= e 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 failures Brent, I suppose I should have been more specific - I assume that pilots of experi= mental aircraft will exercise sufficient judgment not be flying into thunde= rstorms, and thus the likelihood of in-flight lightning strike is nearly ni= l. 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 pum= ps and vacuum-operated artificial horizons are notoriously fallible, and a = poor vacuum can give insidious symptoms causing catastrophic results. Whil= e there have been some experimental EFIS units (notably one you mention, al= so the original pioneer Blue Mountain) which had early individual failure r= ates much higher than vacuum equipment, still the likelihood of two or more= going down simultaneously is rather rare. In my personal experience my TS= O Garmins failed just as often as my experimental equipment - anecdotal evi= dence, to be sure, but 3 TSO failures in 600 hrs not counting vacuum pump f= ailure and attitude indicator partial failure ("lazy" attitude, "sort of" w= orking). None of this absolves individuals contemplating use of experimental equipme= nt from the burden of research to draw their own conclusions about reliabil= ity. 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 som= e 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 revi= ewed the pertinent FARs along with (among others) my mechanic who was a chi= ef avionics safety inspector for a major airline. For the type of flying f= or 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 annua= l 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 wa= s 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 i= ndication 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 barome= tric altitude with static blocked, but that would happen irrespective of th= e 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 fl= y safely to landing. At the end of the day, you are putting your own life on the line. If you f= eel more comfortable with spinning gyros, by all means load up. However, i= f 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 ult= imately be about the same - just different causes. Fly safe! Bill On 01/-10/-28163 02:59 PM, Brent Regan wrote: Bill speculates: <> The primary assumption here is false. It is not "given" that "two EFIS unit= s with battery backup are more reliable than a single vacuum pump". Analysi= s 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 system= s through DO160 certification testing I can say with the confidence of havi= ng empirical data (Remember that one test is worth a thousand expert opini= ons) that I would NOT fly behind a panel that had ONLY electronic gauges, r= egardless 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 DO1= 60 Lightning Induced Transient Susceptibility (section 22) and Lightning Di= rect Effects (section 23) requirements introduced in 2004. Hamid engineere= d several test articles that he then subjected to simulated lightning strik= es in a certified laboratory. Based on those tests I can say with a high l= evel of confidence that most GA certified EFIS and likely all experimental = EFIS systems will not survive a proximal lightning strike, let alone a dire= ct strike. Same goes for experimental autopilots. And that is considering j= ust 2 of 26 sections. There is also Shock, Vibration, Temperature, Magnet = Effect, Voltage Spike, Operational Voltage, RF Susceptibility, ESD, etc. e= tc. 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 cli= mbing 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 p= rincipals and physics. The set of events that will kill both is small and m= ost 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 me= et to to be considered as equipment on aircraft. Therefore, in order to hav= e an "altimeter" in your aircraft you must have an instrument that meets th= e TSOs for an "Altimeter". You can either let the instrument manufacturer d= o 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 tho= se conditions must be that you are actually flying at 8,250 feet MSL. To pr= event this type of thing the FAA has established standards that a device mu= st meet in ordered to be qualified to function as a required device. See FA= R 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 cal= l it ridiculous, but it does not change the fact that it is the law. Bill also postulates that " Experimental EFIS units work acceptably with ei= ther good pitot-static input or GPS input, removing the single point of fai= lure in steam gages.". This statement is non sequitur. The most common Pito= t 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 s= team or electronic display. Redundant sensors are fine ONLY if you have a m= ethod for differentiating good data from bad data. FWIW, Being a good pilot, as I am sure Bill is, does not make you a good en= gine mechanic or good at failure analysis. You can take or ignore the advic= e of those with experience. Fred has put a lot of thought into his system a= nd has reduced the likelihood of a catastrophic electrical failure. Now if = you could only do the same 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 even kno= w what my empty weight is yet -- I was guessing (perhaps optimistically) 11= 00 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 t= ank capacity. I was mostly trying to determine whether it was possible at = all and whether it had been done before. From 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 demo= nstrate it to myself by flying from California to Massachusetts. I had been toying with the idea several years ago, but gave up the idea sin= ce 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 t= his 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 From: rwolf99@aol.com Date: August 9, 2011 6:55:38 AM CDT To: lml@lancaironline.net Subject: TSOs and equipment failure Hamid writes -- <> Actually I agree completely with Hamid. Environmental effects such as the = indirect effects of lightning are precisely where the TSO'd units have an a= dvantage. 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 sy= stem 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 avion= ics systems (electrical power generation and distribution) can also cause f= ailures 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 > Date: August 9, 2011 6:55:38 AM CDT To: lml@lancaironline.net Subject: Re: Re: Re-doing my panel - carefully thinking through failures I don't doubt that, taken in aggregate, experimental avionics experience fa= ilure more often than TSO equipment. My point was that people who make blanket statements suggesting people shou= ld not use experimental equipment at all are drawing the wrong conclusion (= and thus giving others bad advice). That conclusion is using the same gros= s generalization behaviors as a small child that once burns themselves on t= he 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 ca= reful in their use. All avionics can be compared to light bulbs. Cheap ones tend to burn out q= uicker than expensive ones, but there are always counter-examples (expensiv= e ones going out sooner, cheap ones lasting longer). The key is, if you ha= ve 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: <> This is not Brent's statement. Rather, this relates to a suggestion that n= on-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 environm= ental qualification testing (a TSOd unit) is way less likely to fail than a= unit which has not. His first-hand experience taking an experimental syst= em through this process (Sieera Flight Systems, now Chelton) bears this out= . Such units are most likely more resilient to power fluctuation, temperat= ure extremes, shock and vibration, and even exposure to water. In this sen= se, 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 perh= aps 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' el= ectricity.... (But then, if the weather is really bad -- 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 take the r= isk if you're not trying to break some record? Take the wings off, carefully pack the entire airplane (and anything else y= ou will be wanting in Hawaii) in a shipping container, and ship it. Probab= ly 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 Califo= rnia (probably Watsonville) to Hawaii. My back-of-the-envelope calculation= s suggest that I can do this with a GTOW of 2000 or 2100 pounds and have th= e 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 > Date: August 9, 2011 6:55:38 AM CDT To: lml@lancaironline.net Subject: Re: [LML] Re: Fw: Re: Re-doing my panel - carefully thinking throu= gh failures Correcting a typo in my previous e-mail. The changes in the new paragraph a= re highlighted. Hamid Wasti wrote: Lets say you have a system where the "A Buss" and "B Buss" feed an essentia= l 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 bo= th 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. Dur= ing normal operation, the diode on the A Buss will take all the load. But i= f 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 La= w states, there is 100% likelihood that this will be one of the 30% of time= s where it fails open. Lets say you have a system where the "A Buss" and "B Buss" feed an essentia= l 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 dow= n both busses and make sure that the essential buss can run from the remain= ing one, you are likely to find that the essential buss works. The failed d= iode 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 th= e 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 th= is will be one of the 30% of times where it fails 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 thinking throu= gh failures You have a pretty good setup BUT... I had an avionics master breaker (switch type) in my Bonanza that failed. W= hat happened was that the housing cracked behind the panel. The switch fail= ed open on an IFR flight when the housing was no longer able to hold the co= ntacts together. Your DPST switch can fail in the same way and will fail op= en. 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 Subject: Re: [LML] Re: Fw: Re: Re-doing my panel - carefully thinking throu= gh failures Bill, My avionics switch is a DPST switch. Basically two switches in one. Each si= de 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 o= f 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 e= lectrical 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 Fred, Even with all the extra weight and redundancy, your avionics are all relian= t on a single switch. If that $7 switch goes, your plane is blind, deaf, a= nd dumb! The aeroelectric list does not recommend an avionics buss. This = is part of the reason for that. Bill B --_000_FC122468DE4AAC4CAEBE2F06CC7B521A1948509539JSFS01johnsto_ Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable

I was just reading about a circuit breaker problem on the ai= r conditioning unit on a Lancair aircraft. I am an air conditioning contracto= r by trade and a Lancair builder for fun. I would like to know if the a/c ( air conditioning ) problem has been resolved or if someone is still looking for= further feedback. I can be reached by cell phone at 559-313-9114. Sorry, but I do n= ot live and breathe by computer driven E-Mail. Cell phone works best. Dan Kalm= bach   

 

From: Lancair Maili= ng List [mailto:lml@lancaironline.net] On Behalf Of Wayne Marshall
Sent: Wednesday, August 10, 2011 5:13 AM
To: lml@lancaironline.net
Subject: [LML] AC Problem

 

Brent: Any chance you have a bad ground?

On Aug 10, 2011, at 5:01 AM, Lancair Mailing List wrot= e:



       Lancair Mail= ing 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 <hwa= sti@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@lan= caironline.net>.
For archives and help click http://mail.l= ancaironline.net:81/Lists/lml/List.html
LML website: http://= www.lancaironline.net/maillist.html

From: Brent Regan <brent@regandesigns.com<= /a>>

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 coo= ling for the condenser causing higher overall system pressure leading to a highe= r 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 caus= es higher voltage leading to higher compressor current.

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

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

Low buss voltage caused by gear hydraulic pump (HPU) and AC compressor runn= ing 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 failur= es



Hamid,

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

The particular scenario I was worried about was an event on the A bus reach= ing the B bus.   This would require probably that both diodes that fe= ed the e bus fail closed with little or no reverse current protection remainin= g 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&qu= ot; meaning that one or more parameters (voltage drop, reverse current, series resistance etc) is very high.  According to various documents on Failu= re 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 compone= nts, but that is a ball park to get a sense of things.

 

A shorted diode is basically a direct connection, tyin= g 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 u= se under load, it will invariably fail either open or shorted.

 

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

 

Heat is generated in a diode's die and is a function o= f the current and the diode's voltage drop (voltage in volts multiplied by curren= t 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 t= he ambient air. If the case to heat sink interface is not properly designed an= d 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 t= han the ambient air around it. If the air is circulating in a closed environmen= t 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 h= ad 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 curr= ent 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) 2= 5C die temperature. In real life, the die is going to be a lot warmer than tha= t, 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 temperatur= e increase due to that much power, add that to the maximum heat sink temperat= ure 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 head= line 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 ca= lls for 28V certified systems to be able to survive up to a 100mS wide 80V spik= e, 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 wi= ll 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. Wil= l it survive that? If it fails shorted, you just lost your essential buss. Unlik= e 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 o= rder of magnitude or more from the original value of a few mili-ohms. Lets say y= ou 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 sequentiall= y shut down both busses and make sure that the essential buss can run from th= e remaining one, you are likely to find that the essential buss works. The fa= iled 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. Bu= t if you have a failure of the A Buss and all the current starts going through t= his high resistance diode, it is quickly going to fail and as Murphy's Law stat= es, 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.l= ancaironline.net:81/lists/lml/List.html




From: GT Phantom <gt_phantom@hotmail.co= m>

Date: August 9, 2011 6:55:38 AM CDT

Subject: Re: Re: Re-doing my panel - carefully thinking through failures<= o:p>

 

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 nea= rly nil.  Not absolutely nil, naturally, but approaching or below the likelihood of vacuum failure, which is fairly common.  Of course, perh= aps I should not make such an assumption given that a very famous pilot died ju= st last year flying his Bonanza into thunderstorms.

Absent thunderstorms, we will simply have to agree to disagree.  Vacuu= m 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 individua= l failure rates much higher than vacuum equipment, still the likelihood of tw= o or more going down simultaneously is rather rare.  In my personal experie= nce my TSO Garmins failed just as often as my experimental equipment - anecdota= l evidence, to be sure, but 3 TSO failures in 600 hrs not counting vacuum pum= p failure and attitude indicator partial failure ("lazy" attitude, "sort of" working).

None of this absolves individuals contemplating use of experimental equipme= nt 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 els= e'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.  T= he 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 opin= ions about avionics, you too should not consider yourself an expert on FARs simp= ly 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, yo= u will not get accurate airspeed with either blocked and will not get accurat= e 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.  Howe= ver, if you feel you have done your research and would rather replace that vacuu= m 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 tha= n 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 va= cuum 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 gaug= es, 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 DO1= 60 Lightning Induced Transient Susceptibility (section 22) and Lightning Direc= t Effects (section 23) requirements introduced in 2004.  Hamid engineere= d 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 le= vel 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,  e= tc. 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. Hav= ing 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 me= et to to be considered as equipment on aircraft. Therefore, in order to have a= n "altimeter" in your aircraft you must have an instrument that mee= ts 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 aircr= aft and claim it is an altimeter as it will tell you your altitude during certa= in 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 establi= shed 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 h= ave "TSO'd" equipment is logically ridiculous..." is false. You = MUST have at least one of each of the required instruments and they MUST meet th= e 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 wi= th either good pitot-static input or GPS input, removing the single point of failure in steam gages.". This statement is non sequitur. The most com= mon 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 st= eam 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 en= gine 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 ha= s reduced the likelihood of a catastrophic electrical failure. Now if you cou= ld 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 h= ad rough measurements of a ferry tank capacity.  I was mostly trying to d= etermine whether it was possible at all and whether it had been done before.

 

From 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 t= hat was really not that important.  The risk/benefit just wasn't there.&nb= sp; 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 gat= her 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 indu= ced power surge or an alternator caused voltage surge. I would strongly disagre= e with your conclusion.>>

Actually I agree completely with Hamid.  Environmental effects such as the indirect effects of lightning are precisely where the T= SO'd units have an advantage.  With my electrical power example I was tryin= g to say that there are other failure modes (loss of electrical power for a vari= ety 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 mig= ht survive.  In this case, Hamid is right -- the TSOd unit has an advanta= ge here as well.  The lesson is that problems with the fairly mundane por= tion 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.co= m>

Date: August 9, 2011 6:55:38 AM CDT

Subject: Re: Re: Re-doing my panel - carefully thinking through failures<= o:p>

 

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 shou= ld not use experimental equipment at all are drawing the wrong conclusion (and thus giving others bad advice).  That conclusion is using the same gro= ss generalization behaviors as a small child that once burns themselves on the stove and then draws the (incorrect) generalization that "all stoves a= re bad."  In reality it's not that stoves are bad; simply that you m= ust 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 (expensi= ve 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.c= om 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.>><= /o:p>

 

This is not Brent's statement.  Rather, this relates to a suggestion that non-TSOd units should be considered equally reliable as TSO= d units, which is something that Brent disagrees with.

 

I think Brent is saying that a device that has successfully pa= sses environmental qualification testing (a TSOd unit) is way less lik= ely to fail than a unit which has not.  His first-hand experience taking a= n experimental system through this process (Sieera Flight Systems, now Chelto= n) bears this out.  Such units are most likely more resilient to power fluctuation, temperature extremes, shock and vibration, and even exposure t= o 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 sin= gle point failures, and perhaps other things which are totally separate from th= e unit itself.  In this sense, the non-TSOd unit and the TSOd unit are e= qually reliable.

 

Just my two cents...

 

- Rob Wolf

 

p.s. I'm using a vacuum pump and steam gauges.  I don't n= eed 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.co= m>

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 y= ou will be wanting in Hawaii) in a shipping container, and ship it.  Prob= ably 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.c= om wrote:

I'm running the numbers for a ferry tank to take my Lancair 36= 0 from California (probably Watsonville) to Hawaii.  My back-of-the-enve= lope 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 kn= ow 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 failur= es



Correcting a typo in my previous e-mail. The changes in the new paragraph a= re 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 wher= e you sequentially shut down both busses and make sure that the essential bus= s can run from the remaining one, you are likely to find that the essential b= uss works. The failed diode will be able to operate the load for a little bit w= hile it over-heats. During normal operation, the diode on the A Buss will take a= ll the load. But if you have a failure of the A Buss and all the current start= s going through this high resistance diode, it is quickly going to fail and a= s 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*_ s= ide 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 essenti= al buss can run from the remaining one, you are likely to find that the essent= ial 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 B= uss 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% likeliho= od that this will be one of the 30% of times where it fails open.

Regards,

Hamid



From: "Michael Newman" <mnewman@dragonn= orth.com>

Date: August 9, 2011 6:55:38 AM CDT

Subject: RE: [LML] Re: Fw: Re: Re-doing my panel - carefully thinking through failur= es




You have a pretty good setup BUT…

I had an avionics master breaker (switch type) in my Bonanza that failed. What happened was that the housing cracked behind the panel. T= he 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 f= ail 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 t= he other.

 

Bill,

 

My avionics switch is a DPST switch. Basically two switches in one. Each side controls the power feed from one electrical system. Sure, bo= th 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 bo= th 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

 

 

 

Fred,

Even with all the extra weight and redundancy, your avionics ar= e 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

 

 =

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