Questions Instruments
Posted by Then_Part8210@reddit | flying | View on Reddit | 9 comments
I had a question about instrument discrepancies in a GA aircraft I’m in the process of buying.
The airplane has dual Garmin G5 units along with the original analog altimeter. During flight, the G5s and the steam gauge altimeter consistently show about a 50–70 ft difference. It’s not huge, but it definitely bothers me seeing this
For those familiar with G5 installations:
- In this setup, what would generally be considered the primary altitude instrument?
- Would you normally trust the G5s more than the original analog altimeter?
- Is this usually just a calibration or static system issue, or could it indicate something more serious?
- Roughly how expensive is it to correct?
CaptMcMooney@reddit
the analog instruments are primary, you can change the altitude on the g5 to match if it makes you feel better.
No-Foundation-8034@reddit
STC for G5 states that the unit can ONLY be used as a certified attitude indicator OR rate of turn indicator (with the other being retained) for IFR operations.
Analog is the king here. I always teach to set the G5 to the analog altimeter
CluelessPilot1971@reddit
As mentioned already, "G5 Electronic Flight Instrument may not be used as a primary indication of airspeed, altitude, or vertical speed". What many pilots do is set the barometric setting on their primary altimeter as required, and on the G5, set barometric setting such that it will match their primary altimeter. You note the different setting between the two and preserve that difference during your flight.
Ok-Money2811@reddit
Set your altimeter to the metar baro on the ground and see which is right by field elevation, then go from there.
phxcobraz@reddit
Agreed. Set the baro to field elevation on both. Then confirm against the setting provided on weather.
I have G5s and the factory alt on my Mooney. The factory is almost always off by 20-40ft where the G5 is spot on.
If either is off by too much you need to get them calibrated or overhauled.
kev6261337@reddit
The G5 is not certified for primary pitot/static information and should never be used as primary regardless of which is closer to field elevation.
I-r0ck@reddit
Check the maintenance log for its most recent pitot/static check. Find which one is most accurate and then set the other one to match it
FlapsupGearup@reddit
Analog will be your primary. During IFR ops DO NOT use the G5 to determine your altitude to go missed. Dig into the supplement for the G5 for more details.
rFlyingTower@reddit
This is a copy of the original post body for posterity:
I had a question about instrument discrepancies in a GA aircraft I’m in the process of buying.
The airplane has dual Garmin G5 units along with the original analog altimeter. During flight, the G5s and the steam gauge altimeter consistently show about a 50–70 ft difference. It’s not huge, but it definitely bothers me seeing this
For those familiar with G5 installations:
- In this setup, what would generally be considered the primary altitude instrument?
- Would you normally trust the G5s more than the original analog altimeter?
- Is this usually just a calibration or static system issue, or could it indicate something more serious?
- Roughly how expensive is it to correct?
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