Today's Message Index:
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1. 10:00 AM - Re: Re: Simple sequencing using common 5-pin auto relays (Robert L. Nuckolls, III)
2. 10:42 AM - Re: Re: Simple sequencing using common 5-pin auto relays (Matthew S. Whiting)
Message 1
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| Subject: | Re: Simple sequencing using common 5-pin auto |
relays
>
>IIRC, "start power" is for powering the electronic lanes and pumps
>until the engine alternator takes over. In my experience it took
>some time until the engine was "autonomous".
I presume we're discussing a cranking, brown-out event.
If so, the goal is to establish a lower limit for which
brown-out vulnerable appliances are powered while the
starter has a battery loaded down.
Some of you may recall some discussions and experiments
leading to practical brownout mitigation using super
capacitors to deliver energy for the few tens of
milliseconds that starter inrush currents were
loading the battery.
Other designs were proposed not the least of which
utilized boost converters. Others used an array
of LiFePO4 cells capable of grunting a few amps
for the necessary duration.
ALL of these proposals were millisecond fast
using diodes and/or relays to accomplish switching.
No pilot intervention necessary.
Any time a flight system presents shortcomings
that require pilot intervention increases risk
for mis-positioning of controls. This is indicative
of a missed opportunity to keep tomorrow's
systems as simple as yesterday's.
Adverse sensitivity to bus voltage perturbations
are not a new thing . . . appliance qualification
for certified aircraft have required jumping
those hoops for nearly a century.
It up to us as consumers of nifty new gadgets to
hold would be suppliers to equivalent requirements.
Did it for over 40 years . . . it ain't hard!
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 2
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| Subject: | Re: Simple sequencing using common 5-pin auto |
relays
Hi Bob,
No, this isn=99t related to low voltage during cranking. This is a un
ique issue with the Rotax design being an all electric engine. It powers it
s two ECUs, two fuel pumps, fuel injectors, spark plugs, etc. from an intern
al generator called generator A. These systems are completely independent f
rom the airframe electrical system including have a separate ground referenc
e. There is a second, larger, generator B which powers the airframe during n
ormal operation.
There are essentially three phases that occur during engine start and initia
l operation.
Phase 1 where two switches are employed, one which interconnects the indepen
dent ground with the airframe ground and the other which provides battery po
wer to the engine to run the ECUs, fuel pumps, et al, during engine cranking
and initial operation below 1,500 RPM when generator B is not providing suf
ficient power to operate the engine.
Phase 2 begins at 1,500 RPM where generator B takes over operation of the en
gine and now the two switches in phase 1 are opened removing battery power f
rom the engine and isolating the two grounds such that the engine management
system has an isolated ground.
Phase 3 which begins, if I understand the manual correctly, when the engine i
s revved to 2,400 RPM or higher and held for at least 8 seconds. In this ph
ase, generator A now takes over operation of the engine and generator B is s
witched to provide power to the airframe
The =9Cstart power=9D I mentioned in my post is that which is pr
ovided to the engine in Phase 1 and then released once the engine is above 1
,500 RPM.
Many kit planes use separate momentary switches for start power and starter e
ngagement and the pilot has to hold the start power switch for several secon
ds to allow the ECUs to power up and self-test, continue holding start power
while pressing the starter switch, and then releasing both after engine sta
rt, but not release too soon before generator B has taken over powering of t
he engine. This seems overly complicated to me so I am trying to design a s
ystem where the start power can be latched on via a momentary actuation of t
he start power switch with no need to hold it closed and then the starter bu
tton can be pressed normally to crank the engine and then released once the e
ngine fires and also have the start power release automatically also with pr
oper timing with generator B taking over.
Clear as mud?
Matt
Sent from my iPad
> On Aug 10, 2023, at 1:03 PM, Robert L. Nuckolls, III <nuckolls.bob@aeroele
ctric.com> wrote:
>
> =EF=BB
>>
>>
>> IIRC, "start power" is for powering the electronic lanes and pumps until t
he engine alternator takes over. In my experience it took some time until th
e engine was "autonomous".
>
> I presume we're discussing a cranking, brown-out event.
> If so, the goal is to establish a lower limit for which
> brown-out vulnerable appliances are powered while the
> starter has a battery loaded down.
>
> Some of you may recall some discussions and experiments
> leading to practical brownout mitigation using super
> capacitors to deliver energy for the few tens of
> milliseconds that starter inrush currents were
> loading the battery.
>
> Other designs were proposed not the least of which
> utilized boost converters. Others used an array
> of LiFePO4 cells capable of grunting a few amps
> for the necessary duration.
>
> ALL of these proposals were millisecond fast
> using diodes and/or relays to accomplish switching.
> No pilot intervention necessary.
>
> Any time a flight system presents shortcomings
> that require pilot intervention increases risk
> for mis-positioning of controls. This is indicative
> of a missed opportunity to keep tomorrow's
> systems as simple as yesterday's.
>
> Adverse sensitivity to bus voltage perturbations
> are not a new thing . . . appliance qualification
> for certified aircraft have required jumping
> those hoops for nearly a century.
>
> It up to us as consumers of nifty new gadgets to
> hold would be suppliers to equivalent requirements.
> Did it for over 40 years . . . it ain't hard!
>
> Bob . . .
>
> ////
> (o o)
> ===========o00o=(_)=o00o=======
==
> < Go ahead, make my day . . . >
> < show me where I'm wrong. >
> ========================
========
>
> In the interest of creative evolution
> of the-best-we-know-how-to-do based
> on physics and good practice.
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