Our club is considering replacing the vacuum driven AIs and possibly the DGs in our fleet (Cessnas) with Garmin G5 or similar. I’ve been asked to look into options. Therefore, tapping into the wisdom of the crowd here – what are the advantages / disadvantages of the G5? Alternatives? Pros and cons? I am only interested in the technical side of things (the installation is in the US).
In an experimental the G5 is easy to install, 4 wires and pitot and static lines. I have heard about rather high costs for installation of the certified unit in the US. On my experimental forum there seems to be difficulty in setting up the optional magnetometer; location and interference with other electrical signals. I am not sure of the advantage of magnetic heading information, after all ATC cannot know your heading only your track. They give heading information as that is most convenient and fits in with established practice. Most of the G5 installation manual deals with the interface to the G3X and their own auto pilot and is extremely detailed. I suggest you download this manual and try and extract the information you need. The internal data logger provides the following information.
#info,log_version=“1.00”,software_part_number=“006-B2304-11”,software_version=“5.20”,serial_number=“4JQ017178”
UTC Date (yyyy-mm-dd),
UTC Time (hh:mm:ss),
GPS Fix Status,
GPS Sats,
Latitude (WGS84 deg),
Longitude (WGS84 deg),
GPS Altitude (WGS84 ft),
GPS HDOP,
GPS VDOP,
GPS Velocity E (m/s),
GPS Velocity N (m/s),
GPS Velocity U (m/s),
GPS Ground Speed (kt),
GPS Ground Track (deg true),
Magnetic Heading (deg),
Magnetic Variation (deg),
Pressure Altitude (ft),
Baro Setting (inch Hg),
Baro Altitude (ft),
Vertical Speed (fpm),
Indicated Airspeed (kt),
True Airspeed (kt),
Pitch (deg),
Roll (deg),
Turn Rate (deg/sec),
Slip/Skid,
Lateral Acceleration (G),
Normal Acceleration (G),
Selected Heading (deg),
Selected Track (deg),
Selected Altitude (ft),
Selected Vertical Speed (fpm),
Selected Airspeed (kt),
Active Nav Source,
Nav Course (deg),
Nav Frequency (MHz),
Horizontal Deviation,
Vertical Deviation,
VNAV Deviation,
AP Roll Command (deg),
AP Pitch Command (deg),
Attitude Status,
Internal Temperature (deg C),
Battery Status,
Battery Charge (%)
Magnetic heading is available in a standalone installation with a magnetometer,
and when the G5 is configured as a backup in a G3X/G3X Touch system and the G5
is receiving magnetic heading data from an ADAHRS unit. If magnetic heading input
data is not available, the G5 will display GPS-derived ground track instead.
The G5 corrects for shifts and variations in the Earth’s magnetic field by applying the
Magnetic Field Variation Database. The Magnetic Field Variation Database is derived
from the International Geomagnetic Reference Field (IGRF). The IGRF is a mathematical
model that describes the Earth’s main magnetic field and its annual rate of change.
The database is updated approximately every 5 years via a software update. Failure to
update this database could lead to erroneous heading information being displayed to
the pilot.
If the G5 senses that the magnetic heading measurement is valid, but possibly
outside of the internal accuracy limits, the numeric heading is displayed in yellow.
I only intend to use it as DG/AI and GPS source to the transponder.
Simon
simon32 wrote:
I am not sure of the advantage of magnetic heading information, after all ATC cannot know your heading only your track.
You need the magnetic heading information to fly the aircraft, don’t you?
Airborne_Again wrote:
You need the magnetic heading information to fly the aircraft, don’t you?
Usually people plan their flight with reference to the ground, not with reference to the air mass. Meaning they aim for a certain track; they then apply wind correction to derive what heading they should fly… because heading is what their main instrument indicates. That’s mostly historical, because heading was easier to measure. Now, with GPS, well… I just fly a track, and I don’t really, really look at my heading. I know pilots that use their heading bug as a track bug. That’s debatable: on the one hand, it is more practical in normal flight; on the other hand, using the heading bug as a heading bug allows you to switch the AP to HDG mode (accidentally or on purpose, or on GPS failure) without immediately having a turn.
The only exception I can think of right now is when following radar vectors from ATC. They are given in terms of heading, that’s a fact right now, so we need a heading indicator. However, that also is historical, it is because planes didn’t have a track indication “back in the days”. Mostly, (in my understanding) ATC applies wind correction for you. When the vectors are for deconfliction, it is important that everyone uses the same reference (be it heading or track), but save for “GPS failure / historical planes without GPS” kind of scenarios, I don’t see why it would not work just as well (maybe a bit better/easier: no error due to wind shear, less work for ATC because no need to do wind correction) if everyone used track.
Airborne_Again wrote:
You need the magnetic heading information to fly the aircraft, don’t you?
I have a magnetic compass, but have never used it as it is rather inaccurate and hard to compensate; too much iron. I fly using GPS with the DG for more accuracy in the pattern. One can visualize turns quicker than with GPS. If the GPS fails then I use visual references compared to chart (dead reckoning); only happened to me once.
Simon
As in here many people have looked at the G5 and it seems most of them find that it is infeasible in most “advanced” aircraft.
I guess Garmin cannot afford to produce something which would prevent people with King autopilots installing their much more pricey PFDs.
Peter wrote:
As in here many people have looked at the G5 and it seems most of them find that it is infeasible in most “advanced” aircraft.I guess Garmin cannot afford to produce something which would prevent people with King autopilots installing their much more pricey PFDs.
OK, so what are the alternatives ? Aspen Evolution? Sandel 4-ATI ? Others?
Ps: @Peter, I started a new thread on purpose, as I’m trying to figure out what options there are, not limited to the G5; would appreciate if you could split this out again
Our family van, a Cessna Skylark (EASA-reg), just got a cockpit upgrade with dual Garmin G5. I am very happy with it (flew about 25 hours since install) and for IFR it’s probably a bit safer than the WWII attitude indicator we had before. I’ll fly enroute IFR soon in it – the plane is capable of LPV down to 200ft but my license is only E-IR as of now. Oh and the vacuum system is gone. The AI on the left is electric and I believe it wouldn’t even be required. Nice to have though.
172driver wrote:
I started a new thread on purpose, as I’m trying to figure out what options there are, not limited to the G5; would appreciate if you could split this out again
These decisions are sometimes difficult… it helps if one can define the requirements, state the required interfacing, etc.
Lionel posted some alternatives here.
It seems that for a simple AI one gets back to the G5. Where the G5 seems to fail is when you want it to drive some other specific stuff…
