Today's Message Index:
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1. 07:04 AM - Direction Indicator Needs (Summary) (Owen Baker)
2. 08:23 AM - Re: 91.205 - NOT! (Owen Baker)
3. 02:49 PM - Re: Direction Indicator Needs (Summary) (Ken)
Message 1
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| Subject: | Direction Indicator Needs (Summary) |
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
dont 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 dont 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 earths 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@dialupatcost.ca>
Subject: Re: Avionics-List: 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
Message 2
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| Subject: | Re: 91.205 - NOT! |
6/13/2014
Hello Andy, Thanks for your response. You wrote: Why do you think that it
(91.205) does?
1) I agree, 91.205 does not normally apply to any aircraft that has a:
Special Airworthiness Certificate, Category/Designation: Experimental.
2) Such an aircraft is limited to VFR day only flight. See here:
"14 CFR 91.319 Aircraft having experimental certificates: Operating
limitations.
(d) (2) Operate under VFR, day only, unless otherwise specifically
authorized by the Administrator;...."
3) However the entire context of the recent postings regarding the subject
Direction Indicator Needs has been for IFR flight by an aircraft that has a:
Special Airworthiness Certificate, Category/Designation: Experimental.
Purpose: To operate Amateur Built Aircraft. Operating Limitations Dated
XX/XX/XXXX Are Part Of This Certificate.
Note: The terminology and entries in 1 and 2 above are taken directly from
an issued FAA Form 8130-7 (10/82).
4) This below extract copied from the attached document states why 91.205
DOES APPLY for IFR or night flight for an aircraft certificated as in 3
above.(commonly referred to as an EAB (Experimental Amateur Built)
aircraft):
"The Special Airworthiness Certificate issued for each amateur built
experimental aircraft includes specific Operating Limitations. Per FAA
Order 8130.2G the Operating Limitations state: After completion of Phase I
flight testing, unless appropriately equipped for night and/or instrument
flight in accordance with 91.205, this aircraft is to be operated under VFR,
day only. The interpretation given this statement is that if the aircraft
is appropriately equipped in accordance with 91.205 then the VFR day
only limitation no longer applies and the aircraft can be flown at night
or under IFR in IMC."
4) If the EAB in question does not contain the above quoted Operating
Limitations extract then one must, as you say, look at the Operating
Limitations for that specific aircraft to see what does apply.
Please let me know if the above information does not clarify this issue.
Thanks,
OC
======================================================================
From: Dr. Andrew Elliott
Sent: Friday, June 13, 2014 8:38 AM
Subject: RE: 91.205 - NOT!
It does not. In your list, 91.205 is the reference for nearly all
requirements. And most clearly, 91.205 does not apply to experimental
category aircraft. Why do you think that it does?
Andy
==================================================================
From: Owen Baker [mailto:bakerocb@cox.net]
Sent: Friday, June 13, 2014 5:15 AM
Subject: 91.205 - NOT!
6/13/2014
Hello Andrew Eliot, Does the attached document help clarify things for you?
Thanks,
OC
'O C' Baker says "The best investment you can make is the effort to gather
and understand information."
========================================================================================
Time: 07:37:30 AM PST US
From: "Dr. Andrew Elliott" <a.s.elliott@cox.net>
Subject: AeroElectric-List: 91.205 - NOT!
Just a reminder to note that, as specifically stated in the heading
section, 14CFR 91.205 applies to, and only to, "Powered civil aircraft
with *standard* category U.S. airworthiness certificates". For the
larger number of us who are building/flying experimental category
aircraft, the applicable rules appear in your operating limits. The
recommendations in 91.205 are good guidelines, but it's your ops limits,
and the general requirement to have appropriate equipment to complete
the planned flight, that rule here.
Andy
------------------------
Andrew S Elliott, CFI
Message 3
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| 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
On 13/06/2014 10:03 AM, Owen Baker wrote:
>
> 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 dont 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 dont 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 earths 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
>
>
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