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bakerocb
Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA
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 Posted: Thu Jun 12, 2014 9:21 am Post subject: Direction Indicator Needs (Summary) |
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6/12/2014
Hello Aeroelectric and Avionics Listers, On this subject back on 6/10/2014 I wrote:
“I know that there are many technically smart people on these lists and I would like to enlist your assistance.
Picture this situation: There are hundreds (maybe thousands) of EAB (Experimental Amateur Built) IFR capable aircraft flying around with vacuum driven mechanical spinning mass gyroscopic attitude and directional indicators. A large percentage of these builders and pilots would like to (or need to) replace those indicators with something electronic (other than expensive electrical motor driven mechanical spinning mass gyroscopic) in nature and remove the entire vacuum system from their EAB.”
and
“How about it experts (and entrepreneurs) are my desires hopeless and unrealistic?”
I want to now post what I have learned / concluded and express my gratitude to the several people who responded:
1) The two best choices for replacing my previous vacuum driven attitude gyro:
a) The Sandia SAI 340 Quattro. See here:
http://www.sandia.aero/?q=node/80
b) The Dynon EFIS-D6. See here:
http://www.dynonavionics.com/docs/D6_intro.html
2) The best choice for replacing my previous vacuum driven directional gyro:
The MGL Avionics Velocity Singles Horizon / Compass. See here:
http://www.mglavionics.com/html/velocity_singles.html
Many thanks again for all that posted help and I would be willing to discuss my choices if desired.
OC
'O C' Baker says "The best investment you can make is the effort to gather and understand information."
[quote][b]
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nuckolls.bob(at)aeroelect
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| Posted: Thu Jun 12, 2014 2:11 pm Post subject: Direction Indicator Needs (Summary) |
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At 12:21 PM 6/12/2014, you wrote:
| Quote: | 6/12/2014
Hello Aeroelectric and Avionics Listers, On this
subject back on 6/10/2014 I wrote:
“I know that there are many technically smart
people on these lists and I would like to enlist your assistance.
Picture this situation: There are hundreds
(maybe thousands) of EAB (Experimental Amateur
Built) IFR capable aircraft flying around with
vacuum driven mechanical spinning mass
gyroscopic attitude and directional indicators.
A large percentage of these builders and pilots
would like to (or need to) replace those
indicators with something electronic (other than
expensive electrical motor driven mechanical
spinning mass gyroscopic) in nature and remove
the entire vacuum system from their EAB
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Exactly . . . which is what the TC world has
been working toward for decades. A discussion
I had with an FAA type some years ago about
iron-gyro instruments hinged on the word "equivalent"
with confidence levels supported by a plan-b.
We kinda got wrapped around the AHRS axle;
he was of the opinion that rate-based sensors
would never replace a suite of spinning iron disks.
But few contemporary offerings use real gyros yet
are demonstrably capable of offering reliable
presentations.
Our venerable iron gyros were 'backed up' with needle-
ball and airspeed . . . and indeed, the prudent driller
of holes in clouds was encouraged to keep those skills
sharp too.
Ever since I wrote the article on hand-held GPS receivers
for S.A. in 1997, I've not turned on an ADF, VOR or even
a panel mounted GPS. There was a time that I gave away
hand-helds suitable for airplanes (GPS310/315) as
seminar door prizes . . . bought them at Walmart for
$100.
http://tinyurl.com/pzuzf7y
I fly with dual GPS . . . two hand-helds stuck between
glare-shield and windshield with little wads of windshield
sealant. Dual displays that get fresh batteries out-bound
and return legs. Totally independent of panel mounted
equipment . . .
I'd be perfectly comfortable poking through a layer
needle, ball, airspeed -AND- GPS. In terms of complying
with spirit and intent of the rules, the hand helds offer
considerable redundancy to stuff already mounted on the
panel.
Bottom line is, what do YOU need to competently and
confidently operate your airplane? If you call for clearance
to poke holes in clouds, nobody gives a toot what's
on your panel . . . except you. The only time individuals
with an aire of authority care is when digging through
the wreckage . . . at which time it will probably be
discovered that no suite of instrumentation, holy-watered
or not, would have made any difference.
While we owned the airport at Benton, I did a lot of playing
with the dual GPS. I devised approach profiles to
our runway using the hand-helds that were quite capable
of getting me on the ground comfortably at 400 and 1/2.
Never needed to use them . . . but they worked.
The nice thing about the hand-helds is, like the whisky
compass, total independence from the panel mounted stuff.
Put one or more of these puppies in your flight bag
http://tinyurl.com/mrlquos
and the pressures for selection of 'just the right
panel mounted equipment' go WAAaayyyy down . . .
Bob . . .
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bakerocb
Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA
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| Posted: Fri Jun 13, 2014 6:04 am Post subject: Direction Indicator Needs (Summary) |
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6/13/2015
Hello Ken, Thanks for your posting. You wrote:
1) “There is also the Trutrak gemini ADI series for a drop in 3" replacement
with gps track (not magnetic heading).”
I do not think that the units that provide only GPS track information, but
not stabilized magnetic heading information, meet the intended requirements
of 14 CFR 91.205 (d) (9) “Gyroscopic direction indicator (directional gyro
or equivalent)" for replacing my vacuum driven directional gyro.
A case in point: Suppose that ATC tells the pilot to “Fly heading XXX”. I
don’t think that flying some very similar track instead will necessarily
result in immediate danger or a flight violation (if the ATC controller is
not happy with the movement of your aircraft he will most likely just issue
you a new heading to fly), but I don’t think that flying a track instead of
a heading is what a conscientious pilot would want to do.
2) “I would not expect the $500. MGL magnetic sensor and display to be a
satisfactory replacement for a directional gyro. I've never flown it but
the description says it won't be accurate during any turn unless you
upgrade to the substantially more expensive AHRS.”
My comments:
a) You write: “.... the description says it won't be accurate during any
turn unless you
upgrade to the substantially more expensive AHRS.”
I can not find that information on the MGL web site. Can you please help me
find it?
http://www.mglavionics.com/html/velocity_singles.html
b) You write: “.... the description says it won't be accurate during any
turn unless you
upgrade to the substantially more expensive AHRS.”
I can not find any information on the MGL web site that states or implies
that there is any improvement or relationship between a lone SP-6 Sensor,
Tilt-compensated magnetic compass and the display of its heading information
and the heading information displayed from a lone SP-7 Sensor
Attitude indication and turn/bank indication.
c) Here is an extract from the MGL web site:
"Heading stability issues: You may find short term fluctuations of the
heading occurring. These tend to be very small and are typically less than
one
degree. This could still cause the heading to fluctuate occasionally by a
single degree. These fluctuations occur naturally
in the earth’s magnetic field and can also be caused by nearby electrical
equipment such as radios, lamps, electronic
instrumentation or computers, even the ignition systems of engines. The AV-2
is specifically designed for fast response
and thus may show residual fluctuations of the magnetic field that are
impossible to filter out without causing delays in the
update of the heading information."
I can understand that there exists different levels of heading stability and
instantaneous accuracy between the magnetic wet compass envisioned by 14 CFR
91.205 (b) (3) for VFR flight and a stabilized magnetic device that would
meet 14 CFR 91.205 (d) (9) for IFR flight to perfection so it may come down
to which device will meet both the intention of 14 CFR 91.205 (d) (9), but
not to perfection, and the individual pilot's needs.
d) You write: "I was surprised to learn that in my location at 45*N
lattitude, the magnetic vector is tilted about 70 degrees below the horizon
which makes attitude info pretty much essential to simulate a gyro compass."
Understand. How does one determine whether or not some stabilized magnetic
heading indication device indeed has attitude information incorporated at
all into providing more accurate and instantaneous magnetic heading
indication and to the level of that incorporation between the zero
stabilization of a wet compass and perfection?
3) "Nothing like the noise from a spinning gyro to remind me that the master
is still on."
Any time my master switch is on and the alternator is not putting out the
minimum acceptable voltage (such as after alternator failure or engine shut
down) the B&C voltage regulator in my system is flashing a light on my
instrument panel. See here:
http://www.bandc.biz/alternatorcontrollerregulator14vhomebuilt.aspx
Different strokes for different folks. Thanks again for your input.
OC
'O C' Baker says "The best investment you can make is the effort to gather
and understand information."
==============================================================
Time: 11:51:37 AM PST US
From: Ken <kleh(at)dialupatcost.ca>
Subject: Re: Direction Indicator Needs (Summary)
There is also the Trutrak gemini ADI series for a drop in 3" replacement
with gps track (not magnetic heading). These are rate sensing gyros so
they are a bit different than spinning gyro's. If you hold a pitch
attitude and there is an altitude change they function well. However
with no corresponding altitude change they gradually return to
displaying nose level. Not really a problem but if I decelerate very
very slowly I can get the nose quite high while the display still reads
a level flight attitude. Accordingly the gemini flashes an airpseed
warning when the speed gets low.
Similarly if you maintain a turn for a long time, the display will
gradually indicate wings level unless it has heading or track
information such as from a gps.
I would not expect the $500. MGL magnetic sensor and display to be a
satisfactory replacement for a directional gyro. I've never flown it but
the description says it won't be accurate during any turn unless you
upgrade to the substantially more expensive AHRS. I was surprised to
learn that in my location at 45*N lattitude, the magnetic vector is
tilted about 70 degrees below the horizon which makes attitude info
pretty much essential to simulate a gyro compass.
While it's as heavy as the removed vacuum pump, I've been running a
$25. junk table 28volt T&B for quite some time powered with a $5. dc-dc
converter on my 12 volt electrical system. Nothing like the noise from a
spinning gyro to remind me that the master is still on.
Ken
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bakerocb
Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA
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| Posted: Sat Jun 14, 2014 4:58 am Post subject: Direction Indicator Needs (Summary) |
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6/14/2014
Hello Ken, Thanks for your response.
1) I had written: “I can not find that information on the MGL web site. Can you please help me find it?”
And that is exactly what you did when you wrote:
2) “If you look in the manual http://www.mglavionics.com/AV2.pdf
on page 10 you will see the definitions of the 2-D, 3D-A, and 3D-G choices or operating modes.”
and
”I discounted purchasing the stand alone $500. magnetic heading system for these reasons.”
3) I agree completely with your analysis and greatly appreciate your input.
If I want the degree of stabilization that I interpret that 14 CFR 91.205 (d) (9) “Gyroscopic direction indicator
(directional gyro or equivalent)" intends then I must purchase:
a) The AV-2 AHRS Display (VELOCITY Series),
b) Both the SP-6 and SP-7 Sensors (Full AHRS),
c) And, if I intend to mount the two sensors in the same location, an SP-2 / SP-4 Connector.
d) For a total cost of USD $1305 plus shipping.
This increased cost over my earlier posted solution of using just the display and the SP-6 sensor causes me to reconsider the potential solutions to my problem, but I can not yet rule out the MGL solution because of the additional expense. (An addict will go to some extreme lengths to feed his addiction.)
Thanks again for your inputs and I continue to welcome any inputs that others may have.
OC
'O C' Baker says "The best investment you can make is the effort to gather
and understand information." ============================
Time: 02:49:26 PM PST US
From: Ken <kleh(at)dialupatcost.ca>
Subject: Re: Direction Indicator Needs (Summary)
Hi Owen
I agree that gps track does not equate to a gyro compass.
If you look in the manual
http://www.mglavionics.com/AV2.pdf
on page 10 you will see the definitions of the 2-D, 3D-A, and 3D-G
choices or operating modes.
The disadvantages column says "Cannot correctly compensate for tilt
during any form of turn due to centrifugal forces acting on the
accelerometers" That is for the 3D-A mode which is what you get with the
SP6 as far as I can tell.
The disadvantage column for the 3D-G (the best mode of operation with a
full AHRS) says "Can show very large errors if the horizon information
is invalid which could have a number of causes such as exceeding
operational limitations of the horizon system." I interpret this to mean
that you are back to the 3D-A mode if the attitude info is not available.
This is the same results I found in my little experiments with a 3D
magnetic sensor. The results were only useable when flying straight and
level. I'd expect much better results near the equator of course. Again
I have no experience with the MGL products but lacking actual
performance reports, I discounted purchasing the stand alone $500.
magnetic heading system for these reasons.
Ken
[quote][b]
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