Today's Message Index:
----------------------
1. 05:13 AM - Re: Re: B&C Regulators and water-falls ()
2. 06:51 AM - Re: fuel pressure sender ground (al38kit)
3. 08:24 AM - Re: fuel pressure sender ground (messydeer)
4. 01:39 PM - Re: fuel pressure sender ground (al38kit)
5. 01:54 PM - Re: Failure modes with Z14 (Jeff Page)
6. 02:55 PM - Re: fuel pressure sender ground (messydeer)
7. 07:09 PM - Re: fuel pressure sender ground (al38kit)
8. 07:50 PM - Re: Failure modes with Z14 (Ken)
9. 08:59 PM - Re: fuel pressure sender ground (messydeer)
10. 09:47 PM - Re: Failure modes with Z14 (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: B&C Regulators and water-falls |
My firewall mounted tray supplied for my electric dependent engine contains two
Oddessey 680 batts., but I drilled lightening holes in it which should also preclude
water/glycol retension.
Ron Burnett RV-6A forever finishing
Subaru H4--
---- "Robert L. Nuckolls wrote:
============
Received at AeroElectric Connection today . . .
Bill Harrelson and I had a chance to review the
investigation and preliminary causes of an
in-flight fire in a Lancair IV-P that occurred
last spring (2009). The findings and conclusions
are not yet established, but the investigator
felt that some of the information discovered was
not in question, and would be useful to the
experimental community. We agreed to help spread the wordas follows:
The accident aircraft experienced an in-flight
battery fire of the secondary electrical system
shortly after takeoff. The pilot was able to
return to the airport and extinguish the fire in
the tail section of the aircraft after landing.
The battery, case, and nearby components were
consumed/destroyed, and the aircraft fuselage
sustained significant heat damage from the aft
pressure bulkhead to the elevators/rudder. The
cause of the fire has not been absolutely
determined, but the lead/acid battery vents had
apparently been obstructed, resulting in a case
rupture and venting of hydrogen gas into the tail
section of the airplane. The exact cause of this
apparent over pressurization and rupture awaits
additional information and analysis. This finding
and the final NTSB report are expected within a
month and we will disseminate this report through the LML and LOBO newsletter.
One initial result of the investigation was that
the B&C regulator for the secondary electrical
system was inoperative upon post-flight analysis.
The NTSB investigator conducted a detailed
examination and analysis of the defective unit
and determined that the electrical design was
robust and appropriate to the task. The unit was
mounted to the engine side of the firewall with
the spade terminal connectors projecting to the
side of the aircraft. This unit is not sealed,
and at some point liquid (probably water) entered
the metal box, most likely through the opening around the spade terminals,
Hmmm . . . They speak of "spade" terminals . . . I presume they're
referring to the screw-terminal strip.
and filled it to a depth of 1/4 to 1/2 inch. The
liquid allowed arcing among internal components
and to the case ground, leaving carbon tracks on
the circuit board and case, and destroying the electrical functionality.
It is certain that water and electronics don't
mix well. I'm not certain that mounting on the firewall
is an automatic no-no . . . we've been tying stuff
to firewalls since day-one but it IS a unique environment.
Message 2
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| Subject: | Re: fuel pressure sender ground |
I think the sender is fine.
Regarding the failure I read about, yes it was on a rigid tube, and I believe the
tubing failed...the mode of failure would be similar to what you could expect
with a few fittings stacked together and the sender mounted to them.
>From what I can see in your photos, using a large Adel clamp around the sender
body and a second smaller clamp to the engine mount, mating the two together
would be a good way to support the sender...
Then use a steel braided hose to connect the sender to the pressure port.
If there is a two conductor sender available (one with a ground), I'd look into
getting one.
The good thing is that as this is a fuel pressure sender, if it fails and the engine
is still running, it's just a system abnormal....
If it's an oil pressure sender and it indicates zero, you have a more complex situation.
Hope this helps.
Al
messydeer wrote:
> Thanks A. :-)
>
> I understand your comments about the electrical ground.
>
> As far as the chance of this type of unit mounted in this manner failing, I'd
like some clarification. I take it you're saying this type of pressure sender
is okay, but not the way it is installed/supported, right?
>
> And the Questair had one 'on some tubing'. Was this rigid tubing or hose? Seems
an installation that would fix the 1-lb sender to the engine mount would work,
as long as flexible hose goes in and out of it.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=287340#287340
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| Subject: | Re: fuel pressure sender ground |
Thanks, Al :-)
I searched the EAA archives and found a few articles by Tony B. about mounting
fuel and oil pressure senders. He also recommends mounting the pressure sender
to the firewall instead of the engine mount. That would be just as easy for me,
if it's better.
In these articles (Feb and Mar 1992, I think) he also mentioned putting in custom
made pressure reducers in both the oil and fuel lines.
Your critique of the fuel pressure sender support makes me wonder about the support
of the fuel regulator itself, the ~3" diameter yellow disc shaped object
that the T goes into. The pic in my second post shows the Rotec TBI. It's supposedly
nearly identical to the Ellison, but has the fuel regulator housed separately
from the main unit. The main unit of the TBI has a male AN6 fitting and
both ends of the fuel regulator have 1/8" FNPT ports. I have connected the two
together with one aluminum AN-NPT adapter fitting. I was planning on supporting
this regulator with the Adel clamps as shown in the pic, between the T fitting
and engine mount. Maybe this is also a bad idea.
If so, I could fasten it instead to the engine with a bracket. You can see two
cap screws that hold a plate to the engine mount flange, which is about 4-6" away.
I could use the lower cap screw hole to secure a bracket made of 1/8" aluminum.
It would go straight to the fuel regulator and fasten through on of its
own cap screw holes.
The last structural question I have is regarding aluminum vs brass or steel fittings.
I'm using aluminum wherever possible. The pics show some brass fittings,
but I had planned to replace them with aluminum ones. Would it be better to
not use the weaker aluminum for fittings going to the engine?
--------
Dan
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=287355#287355
Attachments:
http://forums.matronics.com//files/restrictor_fittings_by_tony_b_599.jpg
http://forums.matronics.com//files/parts_mounted_on_engine_mount_by_tony_b_192.jpg
http://forums.matronics.com//files/mounting_fuel_and_oil_pressure_senders_by_tony_b_206.jpg
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| Subject: | Re: fuel pressure sender ground |
I think you're on the right track.
Is the thing that looks like a linkage on the regulator just mounted there to control
the TBI, or is there a control on the regulator itself...?
If the regulator can be mounted elsewhere, consider doing that, perhaps on the
firewall or the engine mount and then run the fuel line to the TBI via a flexible
line. You could mount the transducer to the regulator, maybe directly and
forget about any other fittings....You could then run a dedicated ground wire
to the screws on the regulator and solve the transducer grounding thing.
Good luck.
Al
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=287390#287390
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| Subject: | Re: Failure modes with Z14 |
I received lots of response to this, so rather than copy the text of
four messages, I will continue with the pertinent pieces. I
appreciate the responses !
To start, I confused everyone, sorry. It is Z14, not Z12 that I am
considering (along with Z13/8), so that messed up the discussion a
lot, since my actual question was not directly addressed.
Also, I didn't mention which electronic ignitions I plan to use. I
intend to install E-Mag ignitions, not the Light Speed, but this
choice does not really affect the design.
I currently fly a 40 year old Cessna. longg@Pjm picked an excellent
example, since each spring my wife and I fly it from Toronto to
Bahamas to Sun n Fun and back, and other long trips as well. No
matter what design I select, it will be a far better system. However,
since I can do it better, I want to ;-)
Joe described what I like about Z13/8 - pretty much any single
electrical failure permits continuation of flight to intended
destination. Power from the second alternator can be applied to any
chosen load in the airplane as needed, within the limits of the
current produced. I have spent quite a lot of times considering the
effects of various failures.
The only single failure I can think of that would cause a significant
problem is an over voltage event that the OV module didn't address in
a timely fashion, and the electronics in both ignitions fried. Bob,
your experience indicates this is a very unlikely occurance. Medical
statistics are the same way. I don't care how rare a disease is if I
am the one that has it. Then, in another post, you describe the
in-flight fire in a Lancair IV-P due to the abused regulator/OV unit
that I am planning on using ;-)
An over voltage event is something I have no plan B for. A battery
operated radio is great, but there is no equivalent for the ignition.
Unlike a regulator and alternator, that I can easily see are working
throughout the flight, I have no way of knowing if the OV unit will
function as intended in the rare case I need it to. I do not have the
resources to analyze and test the design to be convinced it is
failure-proof. Of course, like any component, it is not, so I need a
plan B.
One way of addressing it, is two isolated systems running the
ignitions. So although I really like Z13/8, Z14 has possibilities.
Unlike Z13/8, Z14 has what seems to me to be a weakness. There is no
essential bus diode, so a single contactor failure leaves the battery
bus unpowered, in spite of having two working alternators. So if I
have one electric fuel pump, and it happens to be on that battery bus,
then my flight endurance is limited by battery capacity.
Perhaps what I am looking for, is a modification to Z14, that will
provide an alternative path to a battery contactor that fails, without
providing additional failure modes that take away the advantages of
the isolated system. Any ideas how to do this ?
Jeff Page
Dream Aircraft Tundra #10
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| Subject: | Re: fuel pressure sender ground |
The linkage on the regulator is the primer lever. Pull the cable and it presses
down on an a diaphragm override valve allowing fuel to spill into the TBI. So
it goes wherever the regulator goes.
In case you or anybody has questions or comments about anything in the setup, the
fuel line exits the slanted firewall a few inches above the gascolator, which
is ~3" in front of the firewall. Then a hose connects into the back of the
gascolator. The gascolator, Facet pump, and flow sensor are mounted to the 3 closest
engine mount tubes. Two clips supporting the front of the gasco and the
fuel flow sensor are not shown. Two brass 1/8-1/4 NPT reducer nipples connect
these 3 components. Hose will exit the fuel flow sensor, then up to the mechanical
pump (not connected in the pic).
> if the regulator can be mounted elsewhere, consider doing that, perhaps on the
firewall or the engine mount and then run the fuel line to the TBI via a flexible
line. You could mount the transducer to the regulator, maybe directly and
forget about any other fittings....
Funny, I just posted a question about using a hose between the regulator and TBI
on the Yahoo Jabiru Group. The regulator can be mounted pretty much anywhere
else. Rotec says to keep it within a few inches up or down of the TBI. The further
backwards it would go, the more of a head change there'd be in a climb or
dive, which I guess would mean having to tweak the mixture. Same thing would
happen if it were mounted much higher or lower than the intake. The firewall
is ~8" behind the intake.
I don't know if mounting the regulator on the firewall would be the best. I'll
get some more info about that. If it can be done, I'd rather mount both the regulator
and the pressure sender on the firewall, cuz that would allow me to use
a simple hard fitting between the two components. Then there'd be a single hose
to the TBI, but it would mean ~16" of extra hose round trip.
>From what TB wrote, it sounds he'd not want the pressure sender anywhere but the
firewall. But you'd be okay with it on the engine mount, as long as hose connects
it and not hard fittings?
--------
Dan
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=287399#287399
Attachments:
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| Subject: | Re: fuel pressure sender ground |
I think you'd be fine mounting the regulator and transducer on the engine mount...consider
the lower one and maybe you could get by with about a 9" sweeping
line to the TB...that way putting a push-pull cable on it would be easy.
Good luck...
Al
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=287432#287432
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| Subject: | Re: Failure modes with Z14 |
Jeff
I have 320 hours on my Z-14 which is really two electrical systems. Each
system powers an ignition and efi system directly from the battery and
either system will run the engine. Both alternators have an OVP system
that will disconnect the respective alternator.
So to damage one ignition or efi computer there must be two failures.
The regulator and then the OVP system. I don't worry about two failures
but even then the second system will run the engine. As per Bob's
directions for the OVP, it is easy to test the OVP module occasionally
if I choose. The procedure is simply to bump the voltage a couple of
volts with a couple of D cell flashlight batteries as I recall.
I guess my main point is that I do not route engine critical current
through a contactor. Why put more things to fail in those current paths.
I do run other systems, including starter current through a contactor.
The only time the crossfeed contactor closes is during engine cranking
or if I decide to manually close it after an alternator fails. I also
feed one cigarette lighter receptacle from a battery bus in case I ever
need to power a handheld device from it. Also comes in handy when camping.
Ken
Jeff Page wrote:
>
> I received lots of response to this, so rather than copy the text of
> four messages, I will continue with the pertinent pieces. I appreciate
> the responses !
>
> To start, I confused everyone, sorry. It is Z14, not Z12 that I am
> considering (along with Z13/8), so that messed up the discussion a lot,
> since my actual question was not directly addressed.
>
> Also, I didn't mention which electronic ignitions I plan to use. I
> intend to install E-Mag ignitions, not the Light Speed, but this choice
> does not really affect the design.
>
> I currently fly a 40 year old Cessna. longg@Pjm picked an excellent
> example, since each spring my wife and I fly it from Toronto to Bahamas
> to Sun n Fun and back, and other long trips as well. No matter what
> design I select, it will be a far better system. However, since I can
> do it better, I want to ;-)
>
> Joe described what I like about Z13/8 - pretty much any single
> electrical failure permits continuation of flight to intended
> destination. Power from the second alternator can be applied to any
> chosen load in the airplane as needed, within the limits of the current
> produced. I have spent quite a lot of times considering the effects of
> various failures.
>
> The only single failure I can think of that would cause a significant
> problem is an over voltage event that the OV module didn't address in a
> timely fashion, and the electronics in both ignitions fried. Bob, your
> experience indicates this is a very unlikely occurance. Medical
> statistics are the same way. I don't care how rare a disease is if I am
> the one that has it. Then, in another post, you describe the in-flight
> fire in a Lancair IV-P due to the abused regulator/OV unit that I am
> planning on using ;-)
>
> An over voltage event is something I have no plan B for. A battery
> operated radio is great, but there is no equivalent for the ignition.
> Unlike a regulator and alternator, that I can easily see are working
> throughout the flight, I have no way of knowing if the OV unit will
> function as intended in the rare case I need it to. I do not have the
> resources to analyze and test the design to be convinced it is
> failure-proof. Of course, like any component, it is not, so I need a
> plan B.
>
> One way of addressing it, is two isolated systems running the
> ignitions. So although I really like Z13/8, Z14 has possibilities.
>
> Unlike Z13/8, Z14 has what seems to me to be a weakness. There is no
> essential bus diode, so a single contactor failure leaves the battery
> bus unpowered, in spite of having two working alternators. So if I have
> one electric fuel pump, and it happens to be on that battery bus, then
> my flight endurance is limited by battery capacity.
>
> Perhaps what I am looking for, is a modification to Z14, that will
> provide an alternative path to a battery contactor that fails, without
> providing additional failure modes that take away the advantages of the
> isolated system. Any ideas how to do this ?
>
> Jeff Page
> Dream Aircraft Tundra #10
>
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| Subject: | Re: fuel pressure sender ground |
Good to know. I reread the Rotec advice and they said mounting it level or 2" above
would be fine, but don't mount it below the intake, if possible. So I think
I've got a good spot on the upper tube. The hose between them is about 4-5"
and with maybe 10-15 degrees curve.
Now I'll order some more fittings and work on the brackets.
Thanks for all your help, Al :-)
--------
Dan
Read this topic online here:
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Attachments:
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Message 10
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| Subject: | Re: Failure modes with Z14 |
At 03:52 PM 2/20/2010, you wrote:
>
<snip>
>The only single failure I can think of that would cause a significant
>problem is an over voltage event that the OV module didn't address in
>a timely fashion, and the electronics in both ignitions fried.
But that's a DUAL failure. An OV protection scheme fails
followed by a regulator running amok . . .
>Bob, your experience indicates this is a very unlikely occurance. Medical
>statistics are the same way. I don't care how rare a disease is if I
>am the one that has it.
How many dual failures do you intend to hypothesize and
address as part of your FMEA?
>Then, in another post, you describe the in-flight fire in a Lancair
>IV-P due to the abused regulator/OV unit that I am planning on using ;-)
That wasn't an electronics failure but an INSTALLATION failure.
Similarly, you can't have a plan-b for loose prop bolts, thrown
jugs, ailerons lost to high speed flutter, etc. These things
are even more rare but offer exceedingly dire challenges to
your survival skills.
>An over voltage event is something I have no plan B for.
A optimally managed OV event becomes an LV even in tens
of milliseconds after onset of the failure. This is why
we generally don't bother to install OV annunciators
on the panel . . . but bulbs don't stay lit long enough
for you to make much use of what they have to tell you.
After the alternator is shut down, plan-b is the same
as if you'd thrown a belt, broken a wire, etc.
>A battery operated radio is great, but there is no equivalent for
>the ignition.
>Unlike a regulator and alternator, that I can easily see are working
>throughout the flight, I have no way of knowing if the OV unit will
>function as intended in the rare case I need it to. I do not have the
>resources to analyze and test the design to be convinced it is
>failure-proof. Of course, like any component, it is not, so I need a
>plan B.
This is why instructions for installing our OV modules
call for testing every annual along with instructions on
how to do it. However, these devices have been installed
on TC aircraft for over 40 years. I don't recall seeing
any maintenance manual call for annual testing.
>One way of addressing it, is two isolated systems running the
>ignitions. So although I really like Z13/8, Z14 has possibilities.
>Unlike Z13/8, Z14 has what seems to me to be a weakness. There is no
>essential bus diode, so a single contactor failure leaves the battery
>bus unpowered, in spite of having two working alternators. So if I
>have one electric fuel pump, and it happens to be on that battery bus,
>then my flight endurance is limited by battery capacity.
If a fuel pump is critical to sustained flight, then why
don't you have two pumps? Z14 has no ENDURANCE bus because
one bus becomes the endurance bus should the other one be
taken down due to alternator failure. If the small alternator
quits, then most likely both busses can be kept up using
the larger alternator. If the big guy quits, then shut
the main bus down, reduce loads to get airport in sight using
small alternator . . . then close the cross-feed contactor
and use both batteries plus small alternator to terminate
the flight.
>Perhaps what I am looking for, is a modification to Z14, that will
>provide an alternative path to a battery contactor that fails, without
>providing additional failure modes that take away the advantages of
>the isolated system. Any ideas how to do this ?
Your stacking failure on top of failure to the degree that
you'll have plans B, C, D, etc. Worse yet, you risk becoming
and electrical systems failure analyst when you should be
concentrating on piloting instead of deducing the appropriate
"plan".
Make one of the Emags a self-powered version and wire
as shown in Figure Z-13/8 . . . you've got redundancy
to burn. If your engine is electrically dependent on
fuel delivery, then you need two pumps. Run one from
the main bus, the other from the battery bus.
Run a 9011 multi-channel OV.LV monitor to annunciate
contactor failure.
Bob . . .
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