---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sat 05/12/12: 8 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 02:45 AM - Re: Engine Quit on Takeoff (John MacCallum) 2. 07:37 AM - Re: Engine Quit on Takeoff (Robert L. Nuckolls, III) 3. 08:09 AM - Re: Engine Quit on Takeoff (user9253) 4. 09:13 AM - Re: Engine Quit on Takeoff (David Lloyd) 5. 09:16 AM - Intermittent no radio reception (Bill Bradburry) 6. 11:16 AM - Re: connect 1-5 volt fuel level sender to legacy type fuel gage (Paul Millner) 7. 11:32 AM - Re: Engine Quit on Takeoff (Paul Millner) 8. 05:35 PM - Cessna Alternator OV protection (Robert L. Nuckolls, III) ________________________________ Message 1 _____________________________________ Time: 02:45:50 AM PST US From: "John MacCallum" Subject: RE: AeroElectric-List: Engine Quit on Takeoff Yes it would seem you had an over voltage. My Vans supplied Plane Power Alt has an over Voltage crowbar built in. If there was a crowbar and the crow bar functioned in your case it could have taken the Buss voltage low. I'm unsure if the Nippon Denso You mention has this feature or not. If the Buss voltage did go low after the over volt event then it would have killed the ignition on the E mag. The P mag Should keep functioning in this case since it has it's own power supply. I don't understand why the P mag should have been Damaged by high amperage or high oil temp. If the Oil temp went high enough to damage the Mag then the whole engine Would be suspect. Looking through the circuit diagram for a E Mag P model if the Buss Voltage goes low it will pull Pin 5 below 12 Volts. There should be an internal diode to stop that causing P mag to shut down. Maybe this is why they said the Circuit board Was un reliable. These types of failure modes is why I chose to stay with a standard Magnetos. Cheers John MacCallum VH-DUU RV 10 #41016 -----Original Message----- From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L. Nuckolls, III Sent: Saturday, 12 May 2012 10:59 AM Subject: Re: AeroElectric-List: Engine Quit on Takeoff --> At 07:28 PM 5/11/2012, you wrote: OK I need some help on where to start looking. Sorry for a long post but don't know how to say it without leaving important stuff out. About a month ago I lost power on takeoff. It didn't quit completely so thanks to some throttle blips and altitude I made the "impossible turn" and got the plane back on the ground and taxied normally to the hangar. First we checked the fuel system, doing fuel flows every conceivable way we knew how. Even tied the tail down and ran one in a "climb out attitude". All flows seemed to be normal. The next thing was to download the Dynon data log. In looking that over it became apparent at the time of the incident I was producing 62 Amps and 20+ Volts. This would last for a few seconds and drop to a more normal range then spike again it did it several times. It appeared that the spikes were when the engine wasn't running. The next was checking the P and E mags. Brad after hearing my story suggested I send them in. They found the circuit board in the P-Mag wasn't reliable. Both mags had been subjected to very high temps, according to Brad this could have been from the engine oil temp or the high amperage. I learned that I had the blast tubes aimed incorrectly. They have been rebuilt and are now both P-Mags. The alternator, Van's Nippon Denso, was bench checked twice by two separate shops. Everything was normal. The plane was reassembled and test run. Everything seemed normal until I ran high RPM, 2000+. As soon as the RPMs climbed the Dynon showed the amps climbed right up to 60 and voltage up to 20. The engine kept running on the ground but to say the least I am not enthusiastic trying to fly it with these same conditions. Where do I go from here? Jim Thorne The alternator was in uncontrolled runaway and you apparently don't have over-voltage protection system installed. The last time we were discussing Van's alternators, they were internally regulated machines. At a minimum, have the regulator replaced. If you're going to have the alternator opened up by a competent local shop, you might see if they would modify it for external regulation which is more builder friendly for addition of ov protection and any-time, any-conditions on/off control from the cockpit. What you have experienced is a relatively rare event . . . but the risks are not zero. This is why legacy alternator installations in TC aircraft have been externally regulated and fitted with ov protection almost since day-one. The first alternator installations on Cessnas did not have ov protection . . . but we quickly learned. Bob . . . ________________________________ Message 2 _____________________________________ Time: 07:37:56 AM PST US From: "Robert L. Nuckolls, III" Subject: RE: AeroElectric-List: Engine Quit on Takeoff At 04:43 AM 5/12/2012, you wrote: > > >If there was a crowbar and the crow bar functioned in your case it could >have taken the Buss voltage low. I'm unsure if the Nippon Denso >You mention has this feature or not. If it's a stock ND model, no such ov protections will exist. If it did exist, the operation of ov protection would only bring the alternator under to heal by shutting it off. Bus voltage would then fall to battery voltage . . . on the order of 12.5 volts, whereupon flight could be continued battery- only. >If the Buss voltage did go low after the over volt event then it would have >killed the ignition on the E mag. "Low" in non quantified in the event narrative. There's no indication that low refers to anything less than battery-only bus voltages which are quite sufficient to keep the engine's fires lit. >I don't understand why the P mag should have been >Damaged by high amperage or high oil temp. If the Oil temp went high enough >to damage the Mag then the whole engine would be suspect. High amperage was a manifestation, not a cause. Runaway alternators boost system voltage to levels mitigated only by system loads and ability/willingness of the battery to soak up excess energy. The fact that 'high amperage' was displayed on the instrumentation only serves to confirm the fact that bus voltage is being pushed by the alternator to 20+ volts and is still rising. >Looking through the circuit diagram for a E Mag P model if the Buss Voltage >goes low it will pull Pin 5 below 12 Volts. There should be an internal >diode to stop that causing P mag to shut down. Maybe this is why they said >the Circuit board was un reliable. > >These types of failure modes is why I chose to stay with a standard >Magnetos. These types of failures happen only when the system suffers from lack of attention to demonstrable risk. Without ov protection, it's not just your electronic ignitions that are at risk, every electro-whizzy in the airplane is at risk. Justifying magnetos as a hedge against ignition failure due to alternator runaway is only a part of the story. Ov protection has been a staple feature of alternator systems on TC aircraft for over 40 years and continues to this day. This narrative does raise questions about the engine failure. I'll get in touch with my friends at Emagair and explore the details with them. Bob . . . ________________________________ Message 3 _____________________________________ Time: 08:09:47 AM PST US Subject: AeroElectric-List: Re: Engine Quit on Takeoff From: "user9253" An intermittent problem is a characteristic of a loose or corroded connection. If the alternator has an external voltage sense wire, then corrosion or a loose connection could make the internal voltage regulator think that the the system voltage is low even though it is not. Then the voltage regulator would try to increase the system voltage by increasing the alternator field current, resulting in an over-voltage condition. If it is not desired to convert from an internal to an external voltage regulator, then it would still be worthwhile to add an external over-voltage protection circuit. Although an external O.V. circuit would tell the alternator to shut off, a runaway internal voltage regulator could ignore the command, unlikely but possible depending on the failure mode. There have been discussions on AeroElectric about the probability of an internal voltage regulator failing. Although failure is unlikely, if it happens, it could be expensive or even life threatening in the case of electrically dependent engine or instruments. Joe -------- Joe Gores Read this topic online here: http://forums.matronics.com/viewtopic.php?p=372907#372907 ________________________________ Message 4 _____________________________________ Time: 09:13:11 AM PST US From: "David Lloyd" Subject: Re: AeroElectric-List: Engine Quit on Takeoff Jim, What have you checked in the fuel system..! During a climb out one is usually pitched at a higher angle and if any foreign stuff is in the tank(s) it may have plugged the outlet enough that fuel flow would not have been enough under 100% power, but, still keep the engine blipping with some fuel. Such things as a disintegrating shop rag, sealant coming loose, etc., etc. The oddest we ever saw was micro fibers leaching off the inside of fiberglass gas tanks. The fine fibers were getting thru the filters and plugging up fuel flow downstream. Dave ------------------------------------------------------------------------- ------- ----- Original Message ----- From: Jim Thorne To: aeroelectric-list@matronics.com Sent: Friday, May 11, 2012 5:28 PM Subject: AeroElectric-List: Engine Quit on Takeoff OK I need some help on where to start looking. Sorry for a long post but don't know how to say it without leaving important stuff out. About a month ago I lost power on takeoff. It didn't quit completely so thanks to some throttle blips and altitude I made the "impossible turn" and got the plane back on the ground and taxied normally to the hangar. First we checked the fuel system, doing fuel flows every conceivable way we knew how. Even tied the tail down and ran one in a "climb out attitude". All flows seemed to be normal. The next thing was to download the Dynon data log. In looking that over it became apparent at the time of the incident I was producing 62 Amps and 20+ Volts. This would last for a few seconds and drop to a more normal range then spike again it did it several times. It appeared that the spikes were when the engine wasn't running. The next was checking the P and E mags. Brad after hearing my story suggested I send them in. They found the circuit board in the P-Mag wasn't reliable. Both mags had been subjected to very high temps, according to Brad this could have been from the engine oil temp or the high amperage. I learned that I had the blast tubes aimed incorrectly. They have been rebuilt and are now both P-Mags. The alternator, Van's Nippon Denso, was bench checked twice by two separate shops. Everything was normal. The plane was reassembled and test run. Everything seemed normal until I ran high RPM, 2000+. As soon as the RPMs climbed the Dynon showed the amps climbed right up to 60 and voltage up to 20. The engine kept running on the ground but to say the least I am not enthusiastic trying to fly it with these same conditions. Where do I go from here? Jim Thorne RV7A ________________________________ Message 5 _____________________________________ Time: 09:16:24 AM PST US From: "Bill Bradburry" Subject: AeroElectric-List: Intermittent no radio reception I had a problem with my radio reception today and I am not certain where to look for the cause. I was flying and the radio was working fine. I was listening to Approach while I flew around and I could hear them fine. I decide to land, so I dialed in ATIS. I didn't get anything. I noticed that I didn't have the "RX" showing on the radio. At the time I was about 25 miles away and 2K feet. I thought maybe I was too low and far away, although I had been listening to Approach when I dialed in ATIS. As I got closer, I climbed a little and suddenly I could hear them so I didn't think much more about it. But I am pretty sure that I should have been able to hear them because I could almost see the airport from where I was. After I contacted approach and was handed off to Sanford tower, I didn't hear from the tower for several minutes, then they asked me "how do you hear?". I replied "Fine". I didn't think much more about that incident either, but after I got home, I listened to the tower archives and I found that the tower had asked me 4 times how do you hear and I only heard the last one. This makes me feel that I have some kind of intermittent problem with receive. Everything else was working on the radio that I know of. It seems to be just an intermittent receive problem. Do you have any ideas where I should look for something like that? I have this type of antenna. http://www.aircraftspruce.com/catalog/avpages/antennasystems.php It does not have a ground plane as it is a half wave antenna. The one I have it the 5T which allows the coax to come out and be supported on the side of the fuselage with mounting brackets. The antenna is inside the fuselage just behind the rear bulkhead on the Lancair Legacy. It is mostly vertical, but the ends (top and bottom) curve following the shape of the fuselage and become horizontal for the last 4-5 inches. I think the antenna is something like 41-42 inches long. My plane is all fiberglass. The only carbon fiber is in the horizontal stabilizer, leg fairings, and the wheel pants. None of this carbon is closer than three feet or so to the antenna. But what ever this is, it is intermittent. The receive and transmit seem to work fine until they don't work at all. I have heard others tell me that my transmissions were staticy from time to time, which is why I have been trying to hear myself by listening to the recordings from ATC. If I had not done that I would not even have known that I missed 3 radio calls from ATC. I was probably close to 5-6 miles out and heading directly toward the airport when I was missing the calls. Also, unrelated, I noticed that if I am on autopilot, (TruTrak Digiflight II GPSVG) that the autopilot goes haywire when the radio transmits. I have heard of this problem on the internet but have not looked up what may be causing it. Maybe you know off the top of your head?? Thanks for all you guys help! Bill B ________________________________ Message 6 _____________________________________ Time: 11:16:10 AM PST US From: Paul Millner Subject: Re: AeroElectric-List: connect 1-5 volt fuel level sender to legacy type fuel gage >> What are the characteristics of the instrument? The existing fuel level transmitter/probe is ~200 ohms at empty and less than 10 ohms at full. I'll check current. The tank characteristic is fairly nonlinear, which is reflected in the non-linearity of the gage markings. The JPI gage works via a look-up table, so it should be OK... I guess we could get fancy and linearize the legacy gage, but then the analog gage would require remarking. Note that even though the existing gage in marked non-linearly, it's not accurately so... the 1/4 full mark is about 1/3 of the way up the scale, and actually represents about 1/3 full on the 30 gallon wing tank. But I've become accustomed to that over time. :-) Current full scale? I will ascertain!~ >> It's pretty easy to craft an op-amp signal conditioner that will apply the necessary gain and offset to spread the 1-5 volt signal over the legacy instrument's scale. So... would the old fuel gage continue in service as originally constructed, sending a voltage to the op amp circuit which would be 'resisted' appropriately to fool the gage into thinking it's seeing the resistance fuel level transmitter/probe? Or would we have to modify the conformal coated (!) circuit board on the back of the gage that has power, ground, light and fuel tank inputs? >> These tend to be 'beefy' instruments of perhaps 10 ma full scale. That's a relief... I was wondering how many Joules were being dissipated inside the vapor space of the fuel tank. >>The signal conditioner would have to be vetted for this much sink or source current. Heat sinks are us... >> If you can get full scale current value for me along with the old resistance sender's empty-full span I can sketch a circuit and propose parts. I'm on it! Mom's 89 and in the hospital (fell on her birthday last week), so time's a little limited for visiting the airport. So if I don't have numbers for a couple of weeks, it's NOT from lack of interest, but rather competing priorities. Meeting with the geriatric care RN on Tuesday to explore 'options' for where she lives, etc. Moving will be challenging in many respects after 30 years in the same house, if that comes to be necessary. >> On way to do it in the airplane is hook a rheostat up to emulate the old sender. Adjust the rheostat first for FULL indication, measure voltage across the rheostat before disconnecting it to measure its resistance. Repeat for 1/2 and empty. Got it! >> The only reason you need reading at 1/2 is to verify that the instrument is reasonably linear. It's not linear, but whether unreasonably so or not remains a topic of speculation and debate. Thanks for the action plan and assistance! Paul -- Please note my new email address! millner@me.com ________________________________ Message 7 _____________________________________ Time: 11:32:22 AM PST US From: Paul Millner Subject: Re: AeroElectric-List: Engine Quit on Takeoff On 5/12/2012 7:36 AM, Robert L. Nuckolls, III wrote: > Ov protection has been a staple feature > of alternator systems on TC aircraft for > over 40 years and continues to this day. Pretty close to precisely forty years for Cessna singles... added in the '72 model year. :-) Paul -- Please note my new email address! millner@me.com ________________________________ Message 8 _____________________________________ Time: 05:35:25 PM PST US From: "Robert L. Nuckolls, III" Subject: AeroElectric-List: Cessna Alternator OV protection At 01:31 PM 5/12/2012, you wrote: >On 5/12/2012 7:36 AM, Robert L. Nuckolls, III wrote: >Ov protection has been a staple feature >of alternator systems on TC aircraft for >over 40 years and continues to this day. Pretty close to precisely forty years for Cessna singles... added in the '72 model year. That sounds right. I was in the right seat of Ken Razak's station wagon and he was driving us toward Hornbeak TN for field tests on a truck accident that occurred just west of there. I was sketching various options for the lowest parts-count ov trip circuit to go between the field control switch and the regulator's field relay. I had joined Ken full time several years earlier in '69 but still had a lot of conversation with the guys at the Cessna Pawnee Street Plant (SE models). Somewhere in southern Missouri I settled on the circuit at: http://tinyurl.com/7g7mn6l When we got back to the shop several days later, I brassboarded the circuit and tested it in a cardboard box "environmental chamber" using dry ice and/or a 100W lightbulb to get the temperatures I wanted. Satisfied with the stability, I took the circuit out to Cessna. The head electron- herder (who shall remain nameless) decided that it "wasn't what he was looking for." But a few months later, Hopkins Mfg in Emporia began supplying the "three-fuse firecracker" to the Pawnee Plant aircraft. That was the first . . . and last outside work I did for Cessna S.E. plant. Beech turned out to be a whole lot nicer to work with! That field trip was something of a milestone. This was the first time we built some speed distance measurement equipment synchronized to a pair of DIY motor drive cameras to record truck dynamics driving over the same course as the accident. S/D data was radioed from the truck to a receiver in the back of the station wagon. The radios were salvaged from a 2 meter repeater project. The cameras were 35mm Leicas that had nice cylindrical film wind knobs I could drive with rubber band belts. Data was displayed on nixie tubes and photographed. http://tinyurl.com/7252gx6 http://tinyurl.com/84cxusk Even built my own photo-detectors to count the slots in the S/D wheel. An the head cheese electron-herder probably never did come to understand why I left Cessna! 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