G1000 AHRS alignment

Deephack wrote:

I still wonder if maybe there is something wrong with the AHRS in this aircraft though if it is supposed to compensate for wonky ramps?

Does the ramp lead to ground position of the aircraft that is more than than 20 degrees of roll or more than 5 degrees of pitch away from the horizontal? 5 degrees is a slope of 8.7% and 20 degrees is 36.4%.

lionel wrote:

And the alignment takes far less that “a few minutes”. I’d say something like 10s to 30s?

On our aircraft it always takes longer than 30 seconds, but not several minutes either.

I have first-hand knowledge that a G500 will realign in flight, in cloud/IMC (somewhat turbulent, but not horribly so) when its power is cycled. However, time certainly feels longer during that time

The G1000 can also realign in flight. It happened to me after a temporary failure and restart of the AHRS.

This is what the manual has to say on the matter:

On the PFD, the AHRS begins to initialize and displays “AHRS ALIGN: Keep Wings Level”. The AHRS should display valid attitude and heading fields typically within the first minute of power-up. The AHRS can align itself both while taxiing and during level flight.

NOTE: In-flight initialization of AHRS, when operating without any valid source of GPS data and at true air speed values greater than approximately 200 knots, is not guaranteed. Under these rare conditions, it is possible for in-flight AHRS initialization to take an indefinite amount of time which would result in an extended period of time where valid AHRS outputs are unavailable.

Peter wrote:

I don’t know the G1000 but don’t you have to wait with the aircraft totally stationary for a few minutes?

The pilot training material for the G1000 says:

No, the AHRS/ADC can align while the aircraft is moving and even in flight at bank angles of up to 20°

And the alignment takes far less that “a few minutes”. I’d say something like 10s to 30s?

I have first-hand knowledge that a G500 will realign in flight, in cloud/IMC (somewhat turbulent, but not horribly so) when its power is cycled. However, time certainly feels longer during that time.

FWIIW, the G500 Pilot Guide (the G1000 is not online on the Garmin website…) says:

Fastest AHRS alignment is achieved with the aircraft stationary and with all AHRS inputs valid (3-D GPS position, magnetometer, and air data). During initial power up on the ground, no GPS position and/or magnetic anomalies are common. If the aircraft is taxied prior to AHRS alignment, alignment may be delayed until after a valid 3-D GPS position is available.

During in-flight alignment of the AHRS, minimize aircraft maneuvering. The AHRS will align with shallow banking and pitch angles (less than 20 degrees of roll or 5 degrees of pitch). AHRS alignment may not be possible during more aggressive maneuvers.

I believe the G1000 and G500 both use the same AHRS, the GRS 77.

Peter wrote:

I don’t know the G1000 but don’t you have to wait with the aircraft totally stationary for a few minutes?

You do. We’ve seen cases of G1000 AHRS alignment failures when the aircraft has started taxying before alignment was completed.

I don’t know the G1000 but don’t you have to wait with the aircraft totally stationary for a few minutes? That’s what I have with the Sandel SG102 AHRS.

Apart from sitting on a flat ramp, you may also help intial calibration on the ground by leaving pitot/static covers on and checking that you have enough satellites for an accurate 3D fix with zero GPS velocity and avoid magnetic interference

Anything else will need an engineer look to level the aircraft and set offsets on pitch/roll

It realigns itself but to reset the AHRS breaker would make it align. Are you sure it is correctly calibrated? That is a maintenance action.