 |
Matronics Email Lists
Web Forum Interface to the Matronics Email Lists
|
| View previous topic :: View next topic |
| Author |
Message |
rv7a(at)cox.net
Guest
|
 Posted: Fri May 11, 2012 4:29 pm Post subject: 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
[quote][b]
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
| Back to top |
|
 |
nuckolls.bob(at)aeroelect
Guest
|
| Posted: Fri May 11, 2012 5:08 pm Post subject: 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 . . .
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
| Back to top |
|
|
john.maccallum(at)bigpond
Guest
|
| Posted: Sat May 12, 2012 1:45 am Post 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
--
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
| Back to top |
|
|
nuckolls.bob(at)aeroelect
Guest
|
| Posted: Sat May 12, 2012 6:37 am Post subject: Engine Quit on Takeoff |
|
|
At 04:43 AM 5/12/2012, you wrote:
| Quote: |
<john.maccallum(at)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.
| Quote: | 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.
| Quote: | 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.
| Quote: | 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 . . .
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
| Back to top |
|
|
user9253
Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan
|
| Posted: Sat May 12, 2012 7:09 am Post 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
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
_________________
Joe Gores |
|
| Back to top |
|
|
skywagon
Joined: 11 Feb 2006
Posts: 184
|
| Posted: Sat May 12, 2012 8:13 am Post subject: 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
[quote] ---
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
| Back to top |
|
|
millner(at)me.com
Guest
|
|
| Back to top |
|
|
|
|
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
|
Powered by phpBB © 2001, 2005 phpBB Group
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
