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
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| Subject: | 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
--> <nuckolls.bob@aeroelectric.com>
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
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| Subject: | Engine Quit on Takeoff |
At 04:43 AM 5/12/2012, you wrote:
><john.maccallum@bigpond.com>
>
>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
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| Subject: | Re: Engine Quit on Takeoff |
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
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| Subject: | Re: 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
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| Subject: | 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
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| Subject: | Re: 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
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| Subject: | Re: 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
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| Subject: | 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!
Bob . . .
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