---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sat 09/02/06: 7 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:22 AM - Re: Re: Turn on ALT before engine start? (Logic and experience) (Ed Holyoke) 2. 05:11 AM - Re: downside of manual battery disconnects? (FLYaDIVE@aol.com) 3. 10:43 AM - OV Module additional requirement (Bob Lee) 4. 11:38 AM - Re: Static port on Dynon AoA probe (John W Livingston) 5. 01:55 PM - WAY OT (Off-Topic: Terrorist-Proof Airlines) (rd2@evenlink.com) 6. 07:12 PM - Re: Re: Is EFIS vulnerable at engine start? (Greg Campbell) 7. 08:07 PM - Re: Wiring diagram software (Vern Little) ________________________________ Message 1 _____________________________________ Time: 12:22:23 AM PST US From: "Ed Holyoke" Subject: RE: AeroElectric-List: Re: Turn on ALT before engine start? (Logic and experience) George, Yours is one of those dark and stormy night stories. I've got one like it where I blew the alternator breaker on our C-150 when the engine surged a few times and then quit. I didn't realize that the breaker was blown. I was busy trying to find a place to land. I also neglected to shed lighting loads. The airport within gliding range was obscured by a cloud bank and while I was consulting the GPS for a heading and distance, it rebooted for lack of voltage. I did not need this extra pucker factor at this time. Once on the ground, I figured out what had happened to the electrics and also figured out what I could have done better. The thing is - Cessnas are designed to blow the circuit breaker. It's obviously not sized right. It should be able to handle what the alternator can throw at it. It should not require exceptional airmanship to keep the electrical system running. It's badly designed. Your student was suckered by more bad Cessna design. The split rocker switch is a bad idea. It begs to be mishandled. The POH calls for the alternator switch to be cycled during the run-up and the ammeter to be observed to verify that the alternator is charging. This is unnecessary. All that you need to do to check the alternator is to look at the voltmeter. If it's low, shed some load and look again. You don't need to turn it off and on to see if it is working. What we have the option to do in our "experimental" aircraft is to use a better design that doesn't nuisance trip and that does inform us when the voltage is low so that we can figure out what's going on and what to do about it before the battery is drained. The point Bob made was that, from the charging system's viewpoint, it doesn't matter much in what order you turn them on or if the engine is started first. A guy asked the question. Bob answered it. He never said that turning the alternator on after engine start was the superior technique. He just said that the charging system wouldn't care. By the way, while you are arguing the fine point of when to turn on the alternator, please note that many of Bob's Z figures call for a double pole master switch which turns on the master and alternator field simultaneously. That's the way I wired our RV. It works fine. One can't very well forget to turn on the alternator. Simple is good. Pax, Ed Holyoke -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of gmcjetpilot@yahoo.com Sent: Friday, September 01, 2006 11:37 AM Subject: AeroElectric-List: Re: Turn on ALT before engine start? (Logic and experience) **Let me tell you all a little story first** One of my students many years ago was going on one of her solo cross country flights. Well she made one mistake and turned the battery on and accidentally left the ALT off (Cessna split switch). She took off enroute and did not note the discharge, mistake two. Never the less I can see it happening to anyone. She realized her error and proceed to turn the ALT on. Because the battery was now discharged it demanded a large current, it popped the CB with the combined load of lights, radios and battery charging. She did not think to "load shed" first, before resetting the CB. Well from then on she was perfect. She noted the CB pop, let cool, reset once and left it out when it popped the 2nd time. She did a 180 and than did an electrical load shed to save the remaining battery. Nearing the airport she powered the Comm up and landed without further incidence. Yes she should have turned the ALT on first; Yes she should have checked for charge right after start; Yes she probably would have been successful resetting the CB if she would have turned the strobes and avionics off first, before turning the ALT on; however I never taught her this. To be sure from than on I went over this in detail with all students using Machado's water flow analogy. (End of STORY) ________________________________ Message 2 _____________________________________ Time: 05:11:20 AM PST US From: FLYaDIVE@aol.com Subject: Re: AeroElectric-List: downside of manual battery disconnects? --> AeroElectric-List message posted by: FLYaDIVE@aol.com In a message dated 8/31/06 5:31:02 PM Eastern Daylight Time, hdwysong@gmail.com writes: > Does anyone have any experience with the manual battery > disconnects that the hot rod folks use? > > Has anyone heard any issues with corrosion or failures or > horror stories floating around about these things? > > Are certain brands better than others? > > Are any (for whatever reason) more suitable for aircraft use > than others? > > Thanks for the insight! > > D ================================ D: I am not familiar with the Hot Rod system but I am very familiar with the Boat system. I have designed a dual battery system around a very robust and easy to use A - B Battery switch. Corrosion should not be an issue since it is enclosed and designed to work around salt water. Go to your local chandlery and see what they offer. Barry "Chop'd Liver" "Show them the first time, correct them the second time, kick them the third time." Yamashiada ________________________________ Message 3 _____________________________________ Time: 10:43:49 AM PST US From: "Bob Lee" Subject: AeroElectric-List: OV Module additional requirement --> AeroElectric-List message posted by: "Bob Lee" Bob, I have upgraded my engine from mag to electronic ignition and carb to fuel injection. This has increased the electrical demand far in excess of the 20 amp alternator that is supplied with my engine. I am using Z13-20 with a 40 amp alternator installed in the mag drive of the engine. My load analysis shows 59 amps with everything on (including pitot heat). Therefore I would like to be able to run both alternators together as my standard operation. Now lets make the assumption that one of the alternators has an OV event. Using the existing Crowbar OVM revE as a base line I would like to know if it is possible to remove the wire between pinA of the Gate S6025L, and add an additional output from the OVM to be the trip for the alternator field. The existing positive connection of the OVM would be connected to the alternator B+ as a sense lead. I have a schematic of this idea at http://flyboybob.com/images/kr2/n52bl/electric%20and%20instrument/ov001-rev2 -4.jpg to illistrate my question. The power distribution has the two alternators each with a separate OVM comming together at the battery contactor on opposite sides which puts the battery between B+ power feeds of the two alternators. That's the background, now the question: Would an OVMs be able to sence the offending high voltage alternator and only trip that one alternator off line? Or would the battery not be able to clamp the OV event long enough to prevent the OVM on the good alternator from tripping too? Regards, Bob Lee N52BL KR2 Suwanee, GA 91% done only 65% to go! ________________________________ Message 4 _____________________________________ Time: 11:38:29 AM PST US From: "John W Livingston" Subject: RE: AeroElectric-List: Static port on Dynon AoA probe --> AeroElectric-List message posted by: "John W Livingston" The pressure differential, and hence needle position, will be proportional to angle of attack but the amount of needle movement for a given change in AoA will change with speed (i.e. dynamic pressure). You need to divide the differential signal by the dynamic pressure to obtain a signal that does not vary with speed. Then you can correlate the signal to AoA independent of speed. For an aircraft with a limited upper speed range the instrument as described might be useful, but it isn't quite an AoA indicator. John -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Ernest Christley Sent: Friday, September 01, 2006 12:56 PM Subject: Re: AeroElectric-List: Static port on Dynon AoA probe --> AeroElectric-List message posted by: Ernest Christley --> rparigor@suffolk.lib.ny.us wrote: >Hello Ernest > >"The Dynon probe does nothing more than implement what this gentleman >describes. As I understand it, the exact dimensions aren't critical, >as it has to be calibrated for each airplane anyway. Look on the Dynon >site. They give the calibration procedures, and it is exactly what >Mark and David describe. As for exact dimensions: 3/4" aluminum tube >that tapers down to 3/8" for the pitot, which is pushed up to the top. >The bottom of the head has a triangular slice cut off at a 30 degree angle >from the bottom. The AoA sense hole is 5/8" from the tip. A little less >than 8" long." > >I am not certain that the Zodiac home made probe is doing the exact >same thing as the Dynon. http://www.ch601.org/resources/aoa/aoa.htm > >What size is the size of the port hole of the Dynon AOA hole? >What angle is the port hole drilled in relation to the sliced face? >Is the sliced face flat or has a slight radius? > >Thx. >Sincerely >Ron Parigoris > > > It's about a 1/16th hole drilled tangentially to a flat face. The hole size and location aren't critical. The critical part is that you need two 'pitot' ports pointing forward at different angles. As you change angle of attack, the relative pressures on these two ports will change. It's a relative pressure between just those two ports, so static pressure or absolute dynamic pressure (from airspeed) are unimportant and ignored. As you slow down to where the wing can't maintain altitude, the wind is not coming straight at you, even if the nose is still on the horizon. Riding the edge of stall with a power out, you could be headed down at a 45degree angle even though the plane is in a level attitude. As you're sinking, it is coming from below. The lower pitot will 'feel' more of the rising air than the forward pointing one. How much more it 'feels' will rely completely on AoA. Now all that's necessary is a sensitive differential gauge to measure both pressures, the calibration procedure will set a couple of points that correspond to "doin' fine" and "lift all gone". Just throw in a semi-arbitrary red, yellow and green ranges, and you're good to go. It really is a simple yet profound concept. -- ,|"|"|, Ernest Christley | ----===<{{(oQo)}}>===---- Dyke Delta Builder | o| d |o http://ernest.isa-geek.org | ________________________________ Message 5 _____________________________________ Time: 01:55:42 PM PST US From: rd2@evenlink.com Subject: AeroElectric-List: WAY OT (Off-Topic: Terrorist-Proof Airlines) Sorry, coudn't resist - just received down the pipe: >>> WELCOME TO TPA >>> >>> (Terrorist-Proof Airlines) >>> >>>We at TPA, Terrorist-Proof Airlines, are in the flying business! >>>We can absolutely guarantee no WALK-ON GUNS, KNIVES, BOX CUTTERS, >>>SHOE-BOMBS or other weapons will ever be carried onto OUR FLIGHTS! >>> >>> Book your next flight with TPA, the safest airline in the industry! Rumen do not archive ________________________________ Message 6 _____________________________________ Time: 07:12:59 PM PST US From: "Greg Campbell" Subject: Re: AeroElectric-List: Re: Is EFIS vulnerable at engine start? I considered a "Make before Break" switch on the "ON-OFF-Alternate ON" switch, as well as a momentary switch in parallel with the other switch. This could work well, but only as long as BOTH the "ON" and "Alternate ON" sources were *ON THE SAME BUS*. The hazard would be if either "source" were on a different bus, then if you use a small SPST switch to keep the EFIS alive while you switch from "ON" to "Alternate ON", you face a very likely risk of running MANY amps through a switch (& fuses) designed for FEW amps. At a minimum, you'd probably smoke either or both fuses protecting the EFIS, and then the EFIS would be dead. A workable alternative would be a momentary OFF-(ON) DPST switch, where each source is protected by a diode so it could ONLY feed the EFIS, and would not attempt to serve as a cross-connect between the busses. By putting the diodes on the momentary switch, you avoid having the diodes permanently dropping the voltage going to the EFIS. When you're load shedding, you're probably least likely to want to have "extra" diodes in series with your EFIS. This starts to get a bit complex. The "pain" of having an EFIS screen reboot is fairly low. It might take 30 seconds or so. In the meantime, you could leave the other EFIS screen on and barely miss the first one. Much more important is keeping the AHRS system up & running. The new Pinpoint Inertial AHRS supports two power inputs. But the point is... you can't just casually switch to a "make-before-break" switch without considering what the sources are. You don't want to try running your landing light, pitot heat, nav lights, etc.. thru a switch & fuse rated at 5 amps. Greg ________________________________ Message 7 _____________________________________ Time: 08:07:04 PM PST US From: Vern Little Subject: Re: AeroElectric-List: Wiring diagram software --> AeroElectric-List message posted by: Vern Little How about free, with a complete design already done that you can edit as you want? See http://vx-aviation.com/page_3.html All of the details are available there to download what you want. Vern Little Eric Parlow wrote: > --> AeroElectric-List message posted by: "Eric Parlow" > > > What software is available to make wiring diagrams at a reasonable cost? > > Eric Parlow > RV-10 Avionics > >