Today's Message Index:
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1. 06:27 AM - Estimates of Component Failure Probabilities (wsimpso1)
2. 10:44 AM - Re: Estimates of Component Failure Probabilities (wsimpso1)
3. 01:15 PM - Re: Re: Estimates of Component Failure Probabilities (Charlie England)
4. 04:19 PM - Re: Re: Estimates of Component Failure Probabilities (Bernie)
5. 09:43 PM - Integration of Rotax 912iS (Eric Page)
Message 1
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| Subject: | Estimates of Component Failure Probabilities |
I and another EAA chapter member are working on architecture decisions in our respective
airplanes. In the process, I have assembled Failure Modes and Effects
Analyses for several common options. Unfortunately, we have too small an experience
base for confidence in estimating failure probabilities on the many components.
We are looking for a broader experience set in estimating a number of
things:
Likelihood of Failure
How likely individual items are to fail at engine start as opposed to in-flight?
Will we be able to detect the failures using common post-start and pre-takeoff
checklist processes?
How likely are detection measures in finding impending failures?
If an item is available from B&C, please assume they are the source. My colleague
in this exercise is using a Lycoming with factory supplied Surefly Ignition
and Bendix Fuel Injection. My homebuilt is planned with SDS fuel injection and
ignition. Estimates specific to the hardware are great.
Please help by giving your estimates of in-flight failure probabilities and any
other thoughts you might have on detection and failure modes on the following
components:
Electrical components:
Batteries;
Carling DPDT switches;
Continuous Duty Contactors;
Continuous Duty Relays;
Alternators;
Regulators;
Diode packs and Diodes;
Ignition Equipment;
Conventional Magnetos;
E-Mags;
SDS Ignition and Coils;
Sure Fly Ignition;
Fuel Handling;
Mechanical Fuel Pumps;
Electric Fuel Pumps, Traditional;
Electric Fuel Transfer Pumps, Facet;
Electric Fuel Injection Pumps, Walbro;
SDS Fuel Injection;
Fuel Selector Valves, Traditional;
Fuel Selector Valves, Andair and Newton/SPRL
Sensors supporting electronic fuel and spark;
Avionics;
Avidyne GPS/NAV/COM;
Dynon HDX Display/Processors;
Thanks in advance for any help you can give in these estimations.
Billski
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=503375#503375
Message 2
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| Subject: | Re: Estimates of Component Failure Probabilities |
15 of you have visited this page and not even one of you will share "I have X many
hours in little planes and have had Y of this failure and Z of that failure"?
OK, I shall start. In 2200 hours I have had:
Two plugs on one cylinder foul and cut out the cylinder, with the first cutting
out only a couple minutes before the second. The Archer maintained altitude on
three cylinders;
Two Facet standby electric fuel pumps failed on the ground;
One alternator failure in flight;
One attitude gyro gave up in flight on an instrument training flight in VMC - that
made for an interesting flight;
Two vacuum pumps failed - both in VMC;
One fuel pump sending unit lost its float while IMC, causing a divert to the nearest
ILS in case the tank really was draining. It wasn't. And;
Miscellaneous light bulbs. They do not seem to be out when checked on the ground.
They must burn out during flight.
No inflight battery or contactor or switch issues, near as I can tell from review
of the logs, the switches and contactors all have 6700 hours on them. I will
look back through the logs on the airplane for other failures.
Come on guys, let's hear your totals and all the things that have broken. A perusal
of the log books for repairs won't hurt either.
Billski
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=503378#503378
Message 3
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| Subject: | Re: Estimates of Component Failure Probabilities |
On 10/2/2021 12:44 PM, wsimpso1 wrote:
>
> 15 of you have visited this page and not even one of you will share "I have X
many hours in little planes and have had Y of this failure and Z of that failure"?
>
> OK, I shall start. In 2200 hours I have had:
> Two plugs on one cylinder foul and cut out the cylinder, with the first cutting
out only a couple minutes before the second. The Archer maintained altitude
on three cylinders;
> Two Facet standby electric fuel pumps failed on the ground;
> One alternator failure in flight;
> One attitude gyro gave up in flight on an instrument training flight in VMC -
that made for an interesting flight;
> Two vacuum pumps failed - both in VMC;
> One fuel pump sending unit lost its float while IMC, causing a divert to the
nearest ILS in case the tank really was draining. It wasn't. And;
> Miscellaneous light bulbs. They do not seem to be out when checked on the ground.
They must burn out during flight.
> No inflight battery or contactor or switch issues, near as I can tell from review
of the logs, the switches and contactors all have 6700 hours on them. I will
look back through the logs on the airplane for other failures.
>
> Come on guys, let's hear your totals and all the things that have broken. A perusal
of the log books for repairs won't hurt either.
>
> Billski
>
Hey Billkski,
Maybe no one's responded yet because we don't know which bite of that
elephant to take 1st. ;-)
If you're asking for brand recommendations based on reliability, that's
relatively easy; as you know, B&C would be 1st stop.
If you're asking about what's reliable 'enough', no one component is
reliable enough if finishing the flight safely depends on it (excepting
stuff we simply can't, as a practical matter, duplicate).
My 1st bite: your buddy's Bendix plane will need a different electrical
system backup energy capacity from your SDS-injected plane.
Charlie
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Message 4
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| Subject: | Re: Estimates of Component Failure Probabilities |
Ive been wondering about all the failure preventative measures proposed on this
theme. Im building a Hatz with Verner power hence electronic ignition so have
concerns too. However my history over 55 years and 30,000 hr 10,000 in light
aircraft isnt so dramatic:
9 engine failures, jets, a bleed valve failure, turbine blade disintegration,
seizure from starter failure to disengage after start. Recips, massive valve guide
disintegration which led to spark plug electrode shorting, oil dip stick
failure- parts punched holes through case and let the oil out, fuel vents icing
two times, engine fire - broken fuel line on ground, planitary gear drive on
GSIO engine.
Electrical failures: 2 master contractors on the ground, 1 alternator-broken field
wire, loose generator drive belt on Lycoming, engine pressure ratio gauge
failure, couple dead batteries from neglect.
Landing gear: main gear tire blew out, metal brake line pulled from fitting.
Props: 1 while taxing in soft sand, another when a main gear fell into ice covered
hole on twin.
Im an IA and do my own maintenance, my father started with cars then Lockheed for
35 yrs. which leads me to believe stuff rarely fails but we do. Inspection
and preventative maintenance are never wrong.
Bernie Willis
Sent from my iPhone
> On Oct 2, 2021, at 10:10 AM, wsimpso1 <wsimpso1@comcast.net> wrote:
>
>
> 15 of you have visited this page and not even one of you will share "I have X
many hours in little planes and have had Y of this failure and Z of that failure"?
>
> OK, I shall start. In 2200 hours I have had:
> Two plugs on one cylinder foul and cut out the cylinder, with the first cutting
out only a couple minutes before the second. The Archer maintained altitude
on three cylinders;
> Two Facet standby electric fuel pumps failed on the ground;
> One alternator failure in flight;
> One attitude gyro gave up in flight on an instrument training flight in VMC -
that made for an interesting flight;
> Two vacuum pumps failed - both in VMC;
> One fuel pump sending unit lost its float while IMC, causing a divert to the
nearest ILS in case the tank really was draining. It wasn't. And;
> Miscellaneous light bulbs. They do not seem to be out when checked on the ground.
They must burn out during flight.
> No inflight battery or contactor or switch issues, near as I can tell from review
of the logs, the switches and contactors all have 6700 hours on them. I will
look back through the logs on the airplane for other failures.
>
> Come on guys, let's hear your totals and all the things that have broken. A perusal
of the log books for repairs won't hurt either.
>
> Billski
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=503378#503378
>
>
>
>
>
>
>
>
>
Message 5
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| Subject: | Integration of Rotax 912iS |
I'll be using a Rotax 912iS in my Kitfox build. I'm considering how best to integrate
it into a fault-tolerant electrical system architecture. At first glance,
it appears that Rotax has done much of the heavy lifting, but let me describe
the engine's systems for anyone who is not familiar:
The engine is controlled by a dual channel Rockwell Collins ECU. It has dual electronic
ignition and redundant electronic fuel injection. The fuel rail is
fed by two electric fuel pumps. There are two independent built-in alternators,
"A" (16A) and "B" (30A), feeding two rectifier/regulators. The engine's "Fuse
Box" and ECU manage these components so that the "A" alternator is dedicated
to engine loads and the "B" alternator to battery charging and airframe loads.
The 912iS Installation Manual contains the following relevant notes:
1. If generator A fails, generator B takes over its functions. The airframe electrical
components and the instruments will be supplied by the battery. The battery
will no longer be charged.
2. If generator B fails, the battery will no longer be charged. The engine still
runs on generator A and the instruments will be supplied by the battery.
The operator's manual states: "Failure of both ... power supplies (alternator A/B)
results in engine stoppage. Remedy: Switch ON the Battery Backup switch (in
this case the power supply is provided by the aircraft battery). Restart engine."
The Installation Manual lists engine electrical loads as follows:
- ECU and Fuse Box: ~1.6A
- Warning lamps (2): maximum 240mA [LED: 40mA]
- Fuel pumps (2): maximum 10A each
Some internet searching suggests that the actual combined running load for the
fuel pumps is 7-9A, which seems reasonable, but I couldn't find a definitive answer.
In any case, the Operator's Manual only requires both pumps ON for takeoff
and landing. Let's assume the high end of the Rotax number and say the engine
needs 10A in cruise with one fuel pump operating.
My endurance goal is to continue flight for 45 minutes after loss of both alternators
(time equal to night VFR fuel reserve). I plan to use an EarthX battery.
Their ETX900 discharge curve shows (with a bit of interpolation) that it can
support a 15A load for ~60 min. At 80% capacity (the figure that EarthX cites
as end-of-life), it still meets my design goal, at ~48 min.
Assuming a maintained/tested ETX900 and an engine load of 10A, I would need to
reduce continuous airframe loads to 5A if both alternators fail. I can easily
operate the battery contactor, comm radio, multi-function standby instrument
and intermittent use of the trim motor and cabin lights within that budget, while
saving the landing light for use on short final.
So, I propose the following: Let the Rotax hardware take care of the engine and
alternators, and configure the airframe as shown in the attached simplified diagram.
In normal operation, with the Battery Master switch closed and the Battery
Backup switch open, the Endurance Bus is powered directly from the Battery
Contactor and the Main Bus is powered through a relay with redundant parallel
contacts. If both alternators fail and the Battery Backup switch is closed,
the 40A relay is automatically opened, taking down the Main Bus and reducing
the airframe to minimum endurance loads.
I don't want to carry the weight or maintenance burden of a dedicated EFIS backup
battery just for this extremely unlikely scenario. Engine start brownout protection
will be provided by other means.
I'd love to hear what everyone thinks. Thanks!
Eric
LINKS TO ROTAX & EARTHX MANUALS:
Rotax 912iS Installation Manual (7.24Mb): https://www.rotax-owner.com/pdf/IM_912_iSeries_ED2_R1.pdf
Rotax 912iS Operator's Manual (36.5Mb): https://www.rotax-owner.com/manuals/OM_912iSeries_ED2_R1.pdf
EarthX Battery User's Manual (1.16Mb): https://earthxbatteries.com/wp-content/uploads/2020/11/ETX_Manual_111017_Y-1.pdf
[ETX900 data on pages 12-13]
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=503385#503385
Attachments:
http://forums.matronics.com//files/simplified_electrical_architecture_rev_b_144.pdf
http://forums.matronics.com//files/912is_wiring_diagram_237.pdf
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