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Dark and stormy night during CAVU

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echristley(at)att.net
Guest

Posted: Tue Nov 24, 2020 6:04 am Post subject: Dark and stormy night during CAVU

My plane has been stranded all summer at KTTA, which is a 25 minute flight from my home airport, KJNX.  That's a good hour drive.  I broke a pushrod while on approach there back in the early summer.  Finally got the engine back on and flew her home this past Saturday.  I wasn't at all comfortable with this flight, even though I had spent hours flying touch and goes around KTTA, so my buddy, Dwight, agreed to fly chase.   



Halfway home, the RPM indicator  started dropping.  I reported the problem to Dwight, and he guided me to Triple-W, but on the way down I  was noticing that the speed wasn't dropping.  In fact, I checked and was able to  climb AND speed up!!  I also wasn't hearing the RPM drop off like the tachometer was indicating it should.

I  soon identified the suspect to be where I was picking up the RPM signal from.  I was using  the signal produced by the permanent magnet generator, and I had replaced my old generator with a new, stronger one.  The permanent  magnets produce an AC signal that is exactly 3 pulses per revolution.   Until the regulator hits its set point, that is.  Once the battery is  fully charged, the regulator switches the signal off, it goes high, and  stays there.  The engine monitor no longer sees a pulse, just a high value and interprets  that as a lower RPM.  I checked the theory by turning on every electrical  load I had, and sure enough the RPM started rising without touching the  throttle.  The RPM didn't go all the way back up, 



I have to find another method of picking up the rpm.  I already have a reluctor.  Just have to install it.  But, a word to the wise. . . don't use the generator as a tachometer source.  This is experimental aviation, and I consider this experiment to be a success.  I learned something, and no metal was bent in the process.

bob.verwey(at)gmail.com
Guest

Posted: Tue Nov 24, 2020 6:38 am Post subject: Dark and stormy night during CAVU

Interesting stuff!

Best Regards,Bob Verwey



082 331 2727

[img]https://docs.google.com/uc?export=download&id=0B5d7rgAInTuTUUZsUjY4QmJsdVU&revid=0B5d7rgAInTuTdDJDaXRFZVh3b3lMa3FWL0s3MFdzc01YRlNvPQ[/img]Â  Â  Â Â 



On Tue, 24 Nov 2020 at 16:13, Ernest Christley <echristley(at)att.net (echristley(at)att.net)> wrote:



 	  Quote: 	
		  My plane has been stranded all summer at KTTA, which is a 25 minute flight from my home airport, KJNX.Â  That's a good hour drive.Â  I broke a pushrod while on approach there back in the early summer.Â  Finally got the engine back on and flew her home this past Saturday.Â  I wasn't at all comfortable with this flight, even though I had spent hours flying touch and goes around KTTA, so my buddy, Dwight, agreed to fly chase. Â  



Halfway home, the RPM indicator  started dropping.Â  I reported the problem to Dwight, and he guided me to Triple-W, but on the way down I  was noticing that the speed wasn't dropping.Â  In fact, I checked and was able to  climb AND speed up!!Â  I also wasn't hearing the RPM drop off like the tachometer was indicating it should.

I  soon identified the suspect to be where I was picking up the RPM signal from.Â  I was using  the signal produced by the permanent magnet generator, and I had replaced my old generator with a new, stronger one.Â  The permanent  magnets produce an AC signal that is exactly 3 pulses per revolution.Â   Until the regulator hits its set point, that is.Â  Once the battery is  fully charged, the regulator switches the signal off, it goes high, and  stays there.Â  The engine monitor no longer sees a pulse, just a high value and interprets  that as a lower RPM.Â  I checked the theory by turning on every electrical  load I had, and sure enough the RPM started rising without touching the  throttle.Â  The RPM didn't go all the way back up, 



I have to find another method of picking up the rpm.Â  I already have a reluctor.Â  Just have to install it.Â  But, a word to the wise. . . don't use the generator as a tachometer source.Â  This is experimental aviation, and I consider this experiment to be a success.Â  I learned something, and no metal was bent in the process.

Ceengland

Joined: 11 Oct 2020
Posts: 380
Location: MS

Posted: Tue Nov 24, 2020 7:00 am Post subject: Dark and stormy night during CAVU

On Tue, Nov 24, 2020 at 8:13 AM Ernest Christley <echristley(at)att.net (echristley(at)att.net)> wrote:



 	  Quote: 	
		  My plane has been stranded all summer at KTTA, which is a 25 minute flight from my home airport, KJNX.Â  That's a good hour drive.Â  I broke a pushrod while on approach there back in the early summer.Â  Finally got the engine back on and flew her home this past Saturday.Â  I wasn't at all comfortable with this flight, even though I had spent hours flying touch and goes around KTTA, so my buddy, Dwight, agreed to fly chase. Â  



Halfway home, the RPM indicator  started dropping.Â  I reported the problem to Dwight, and he guided me to Triple-W, but on the way down I  was noticing that the speed wasn't dropping.Â  In fact, I checked and was able to  climb AND speed up!!Â  I also wasn't hearing the RPM drop off like the tachometer was indicating it should.

I  soon identified the suspect to be where I was picking up the RPM signal from.Â  I was using  the signal produced by the permanent magnet generator, and I had replaced my old generator with a new, stronger one.Â  The permanent  magnets produce an AC signal that is exactly 3 pulses per revolution.Â   Until the regulator hits its set point, that is.Â  Once the battery is  fully charged, the regulator switches the signal off, it goes high, and  stays there.Â  The engine monitor no longer sees a pulse, just a high value and interprets  that as a lower RPM.Â  I checked the theory by turning on every electrical  load I had, and sure enough the RPM started rising without touching the  throttle.Â  The RPM didn't go all the way back up, 



I have to find another method of picking up the rpm.Â  I already have a reluctor.Â  Just have to install it.Â  But, a word to the wise. . . don't use the generator as a tachometer source.Â  This is experimental aviation, and I consider this experiment to be a success.Â  I learned something, and no metal was bent in the process.



	




Yeah, there are times when I'm too smart for my own good, as well....Congrats on remembering to 'fly the plane'; you're obviously a better pilot than the highly trained airline crew that flew an airliner into the ground while playing with a circuit breaker. And congrats on a safe outcome,Â as well.Â 

Charlie



  	          		Virus-free. www.avast.com 		 	 [url=#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2][/url]

_________________
Charlie

alec(at)alecmyers.com
Guest

Posted: Tue Nov 24, 2020 7:11 am Post subject: Dark and stormy night during CAVU

 	  Quote: 	
		  > don't use the generator as a tachometer source. 


	


I have a type certified aircraft that doesâ€¦ it uses a commercial (BOSCH) 28v truck alternator, and an automotive tach. All flight instruments are (should be) single point redundant. You just have to know that if the alternator belt fails or the alternator has to be taken offline for some reason, you have to manage without the tach. Not a big deal.

echristley(at)att.net
Guest

Posted: Tue Nov 24, 2020 8:00 am Post subject: Dark and stormy night during CAVU

Ahh!  You have an alternator.  An alternator controls the output power by decreasing the power going to the electromagnet.  If the system needs a tenth of the name plate rating of the alternator, the circuit drops the input to one tenth.  The output pulses from the stator continue...albeit, at one tenth the power.

With a generator, there is no way to manage the strength of the magnets.  So  to control output, the regulator just switches off the circuit coming from the stator.  At least with this regulator.  If I were using a shunt regulator, it would let the stator keep on pushing electrons, and then dump the unneeded ones to ground through a resistor.  The pulses would continue in that case.

I would be happy to live with a bum RPM signal in the case where the alternator broke.  But, this is a bum RPM signal when the thing is working as (poorly) designed.  



                                                                    On Tuesday, November 24, 2020, 10:12:11 AM EST, Alec Myers <alec(at)alecmyers.com> wrote:                 

                 



                 



                 --> AeroElectric-List message posted by: Alec Myers <alec(at)alecmyers.com (alec(at)alecmyers.com)>



 	  Quote: 	
		  > don't use the generator as a tachometer source. 


	


I have a type certified aircraft that doesâ€¦ it uses a commercial (BOSCH) 28v truck alternator, and an automotive tach. All flight instruments are (should be) single point redundant. You just have to know that if the alternator belt fails or the alternator has to be taken offline for some reason, you have to manage without the tach. Not a big deal.



http://www.matronics.com================



-=   --> http://wiki.matronics.com

===================



http://www.=====

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Nov 24, 2020 9:04 am Post subject: Dark and stormy night during CAVU

At 09:06 AM 11/24/2020, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: Alec Myers <alec(at)alecmyers.com>



 

 >> don't use the generator as a tachometer source. 



 I have a type certified aircraft that does… it uses a commercial (BOSCH) 28v truck alternator, and an automotive tach. All flight instruments are (should be) single point redundant. You just have to know that if the alternator belt fails or the alternator has to be taken offline for some reason, you have to manage without the tach. Not a big deal. 	


   Exactly. It's useful to 'become one' with your airplane

   as opposed to being an 'operator'. I recall a fairly

   'experienced' pilot showing up a K1K1 wanting to exploit

   our rental fleet. I invited him to join me in a 150 and

   to show me his stuff.



   We went around the patch a couple of times and it

   was pretty obvious that he was a gage-watcher. I

   suggested to him that our little grass-patch was

   both home to and a favorite nice-day-for-flying way

   point for no radio airplanes.



   I suggested that it was quite possible to safely

   operate the airplane with only the occasional 

   glance at the gages . . . if at all. I got

   the partial-panel covers out and covered up

   ALL of the instruments in front of him and

   suggested, "let's go flying".



   We went around the patch a few more times while

   I queried him about what he could hear and feel

   from the airplane. I pointed out that the 150

   could not be stalled if you can see the horizon

   over the nose. The engine was impossible to

   over-speed except in a dive. Suggested that

   he put the nose on the horizon for climb-out.

   We peeked under the IAS cover and yeah, not exactly

   Vx but entirely satisfactory.



   I demonstrated turning to final at pattern

   altitude from 1/2 mile out. Throttle down,

   hold level speed bleeds off then nose down

   while milking the flaps down to full. Trim

   down until you see that famous Cessna barn-door-

   flaps picture out the windshield. Then

   power up only as necessary to target

   the numbers. 



   We did that a couple of times before we parked

   and went into the office to get him on the

   approved renters list. I suggested that he

   practice those kinds of maneuvers himself

   with the gages visible but glance at them

   not so much with a notion of nailing the

   numbers as maintaining a comfortable flight

   condition . . . and paying attention to

   what ELSE is going on outside.



   The day I got my licence, the chief flight

   instructor at United Beech was doing my

   checkride. It was early Sunday morning with

   very little traffic at KICT. We went to the

   practice area to demonstrate the time-honored

   basics and then headed for home. Half way

   along the downwind he pulled the throttle

   back and asked, "okay, now what?"



   I asked the tower for and was granted

   a short approach. The arrival with the runway

   wasn't particularly graceful and hardly

   a stabilized approach but the energy

   budget for controlled flight was not

   over drawn. He said, "I've seen better

   but all-in-all, not bad". He signed off my

   ticket on the taxi back to the ramp.



   I didn't realize until years later what

   an exceptional crew of instructors taught

   out of United Beech on KICT. Yeah, there

   are times when finely tuned numbers are

   important . . . like when boring holes

   in the crud. But those numbers are icing

   on the cake for competent operation of

   the airplane especially when dealing

   with the unexpected . . . like when

   that pretty glass screen goes dark . . .

   okay, now what?



   What you see, hear and feel are the ultimate

   back-up system for avoiding bad days in the

   cockpit.



 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Nov 24, 2020 1:22 pm Post subject: Dark and stormy night during CAVU

 	  Quote: 	
		  I have to find another method of picking up the rpm.  I already have a reluctor.  Just have to install it.  But, a word to the wise. . . don't use the generator as a tachometer source.  This is experimental aviation, and I consider this experiment to be a success.  I learned something, and no metal was bent in the process.

 	


   Actually, gear driven pm alternators are FINE

   rpm signal sources provided that the interface

   between AC 'signal' from the alternator

   has the right characteristics to drive the

   tachometer.



   The tachometer's installation instructions should

   speak to voltages, waveforms and dc offsets

   tolerated by the tachometer electronics. Of course,

   there's the matter of scale factor . . . tach

   signal events per engine revolution for the purposed

   of calibrating the tach.



   My FIRST choice for an electronic tachometer

   signal source would be the PM alternator if

   available. Three reasons:



   (1) The AC frequency is dead nuts proportional

   to engine rpm and . . .



   (2) the 'signal' is sufficiently robust to

   also be a POWER source for the tach and . . .



   (3) that power source is ALWAYS there if the

   engine is running.



   Having said that, not every tach can exploit

   any PM alternator as a signal/power source.

   Do the homework.  If the electron gods are

   not insulted, you just might have an opportunity

   for a reliable and robust tachometer.



 

 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

dj_theis

Joined: 28 Aug 2017
Posts: 56
Location: Minnesota

Posted: Tue Nov 24, 2020 7:22 pm Post subject: Re: Dark and stormy night during CAVU

 	  Quote: 	
		  I have to find another method of picking up the rpm. I already have a reluctor. Just have to install it. But, a word to the wise. . . don't use the generator as a tachometer source. This is experimental aviation, and I consider this experiment to be a success. I learned something, and no metal >was bent in the process. 	




I have a couple of thoughts and some questions related to this post.



first the thoughts.  



Is it possible the tachometer is wired on the wrong side of the regulator / rectifier?



I have as exhibits, three attached documents.  

1) a similar tachometer circuit as shown in the Remaster electrical manual (i.e. PM alternator with Westach, tachometer)

2) the Revmaster alternator connections as shown in their illustrious manual.

3) the alternator connections as I've redrawn them (after much noodling and consideration).  



Recognizing that not all RR for PMA are created under the same zodiac.  And, I'm in the process of verifying the operation of the Revmaster as I've interpreted and redrawn it.



I can imagine at least one RR design that would shunt the AC coils out when reaching the setpoint, which would nullify the tach signal.  The design of the Revmaster (series regulator, in my personal venacular) does not shunt the PMA coils but instead,  opens the PM circuit when the battery voltage reaches a set value (with an SCR that completes the PMA circuit to battery common).  If the tach is wired on the AC side of the RR, (as Revmaster shows it) the voltage signal will still drive the tachometer when the RR reaches setpoint and opens the circuit to the battery (as described by Bob, with plenty of extra power to spare).



Alternatively, if the tach is on the DC side of the RR, the signal is likely to die out, as the RR intermitantly disconnects the PMA from the battery, as it reaches the target voltage.  Also, ( in the case of the Revmaster's dual alternar) tif the "other" PMA is selected as the "chosen one" to supply power to the battery and ships devices, the original (now disconnected) alternator will still be available to run the tach, with the voltage pulses it is happily generating at basically an "open circuit" voltage condition.  



In the version (that I've not seen, but only heard of) where the PMA is short circuited when reaching voltage setpoint, I can imagine that the tach connected to the AC side would fail to sense any voltage as the RR reached setpoint.  It would seem that this design (a shunted PMA RR) would be very hard on the RR as it has to reject the heat of full current and it's nominal voltage drop and b) damn unnecessary added heat to the PMA as it generates near full short circuit current across its coils.



Does the original post member have a circuit diagram and alternator we can evaluate?

Dan Theis

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_________________
Dan Theis
Scratch building Sonex #1362
Still working on the Revmaster Alternator improvement

echristley(at)att.net
Guest

Posted: Wed Nov 25, 2020 6:35 am Post subject: Dark and stormy night during CAVU

I don't have a circuit diagram.  



I used one of the regulators like this:  https://www.amazon.com/Oumurs-Regulator-Rectifier-1989-1999-74519-88A/dp/B079CJ4DN9/ref=sr_1_18?crid=3R1Q0AO9RIBJQ&dchild=1&keywords=harley+davidson+regulator&qid=1606313589&sprefix=harley+davidson+regu%2Caps%2C164&sr=8-18

This is truly a black box device.  There are dozens of sources selling what looks like the identical item, and I could find exactly zero information about what is inside any of them.  All the reviews I could find said basically, "It works", and being a Harley part, it seems to be targetted at people that do not need or care to know more about what is inside. They all have two wire inputs, and all have one wire output.  I found one that has a 14.5V set point, which is good for my LiFePO battery that doesn't have a BMS other than charge equalization.



I spliced my tach signal wire into one of the leads from the PMA to the regulator.  I had not considered that the regulator might be dumping all the energy from the PMA to ground.  I assumed it would just switch the input off completely.  That would leave the generator with some hysteresis current, but that shouldn't amount to much.  At this point, I'm of a mind to tear this brand new regulator apart, just to find out what is in there.  Dang, education is expensive.



                  

                                                                    On Tuesday, November 24, 2020, 10:30:30 PM EST, dj_theis <djtheis58(at)gmail.com> wrote:                 

                 



                 



                 --> AeroElectric-List message posted by: "dj_theis" <djtheis58(at)gmail.com (djtheis58(at)gmail.com)>



 	  Quote: 	
		   I have to find another method of picking up the rpm. I already have a reluctor. Just have to install it. But, a word to the wise. . . don't use the generator as a tachometer source. This is experimental aviation, and I consider this experiment to be a success. I learned something, and no metal >was bent in the process. 


	






I have a couple of thoughts and some questions related to this post.



first the thoughts.  



Is it possible the tachometer is wired on the wrong side of the regulator / rectifier?



I have as exhibits, three attached documents.  



1) a similar tachometer circuit as shown in the Remaster electrical manual (i.e. PM alternator with Westach, tachometer)



2) the Revmaster alternator connections as shown in their illustrious manual.



3) the alternator connections as I've redrawn them (after much noodling and consideration).  



Recognizing that not all RR for PMA are created under the same zodiac.  And, I'm in the process of verifying the operation of the Revmaster as I've interpreted and redrawn it.



I can imagine at least one RR design that would shunt the AC coils out when reaching the setpoint, which would nullify the tach signal.  The design of the Revmaster (series regulator, in my personal venacular) does not shunt the PMA coils but instead,  opens the PM circuit when the battery voltage reaches a set value (with an SCR that completes the PMA circuit to battery common).  If the tach is wired on the AC side of the RR, (as Revmaster shows it) the voltage signal will still drive the tachometer when the RR reaches setpoint and opens the circuit to the battery (as described by Bob, with plenty of extra power to spare).



Alternatively, if the tach is on the DC side of the RR, the signal is likely to die out, as the RR intermitantly disconnects the PMA from the battery, as it reaches the target voltage.  Also, ( in the case of the Revmaster's dual alternar) tif the "other" PMA is selected as the "chosen one" to supply power to the battery and ships devices, the original (now disconnected) alternator will still be available to run the tach, with the voltage pulses it is happily generating at basically an "open circuit" voltage condition.  



In the version (that I've not seen, but only heard of) where the PMA is short circuited when reaching voltage setpoint, I can imagine that the tach connected to the AC side would fail to sense any voltage as the RR reached setpoint.  It would seem that this design (a shunted PMA RR) would be very hard on the RR as it has to reject the heat of full current and it's nominal voltage drop and b) damn unnecessary added heat to the PMA as it generates near full short circuit current across its coils.



Does the original post member have a circuit diagram and alternator we can evaluate?



Dan Theis



--------



Scratch building Sonex #1362



Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=499506#499506



Attachments: 



http://forums.matronics.com//files/revmaster_2300_rev13_alternator_ckt_190.pdf



http://forums.matronics.com//files/revmaster_manual_alternator_connection_492.pdf



http://forums.matronics.com//files/remaster_manual_tach_connection_377.pdf

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nuckolls.bob(at)aeroelect
Guest

Posted: Fri Nov 27, 2020 8:21 am Post subject: Dark and stormy night during CAVU

 	  Quote: 	
		  

 I can imagine at least one RR design that would shunt the AC coils out when reaching the setpoint, which would nullify the tach signal. 	


   For that situation, I suspect the PM alternator

   output currents never go to zero. One could get

   a righteous representation of AC current frequency

   by passing one lead of the alternator coil through

   a hall sensor. AMPLOC has a line of candidates

   for this task.



  https://tinyurl.com/yxfeta3h



 

  	  Quote: 	
		   The design of the Revmaster (series regulator, in my personal venacular) does not shunt the PMA coils but instead,  opens the PM circuit when the battery voltage reaches a set value (with an SCR that completes the PMA circuit to battery common).  If the tach is wired on the AC side of the RR, (as Revmaster shows it) the voltage signal will still drive the tachometer when the RR reaches setpoint and opens the circuit to the battery (as described by Bob, with plenty of extra power to spare). 	


   agreed



 

  	  Quote: 	
		  Alternatively, if the tach is on the DC side of the RR, the signal is likely to die out, as the RR intermitantly disconnects the PMA from the battery, 	


   Validity of the alternator's AC information

   is not preserved across the RR. Valid tach data

   will be available only at the AC output leads

   from the alternator.



 

 

   Bob . . .



   Un impeachable logic: George Carlin asked, "If black boxes

   survive crashes, why don't they make the whole airplane

   out of that stuff?"

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