Ahars
 

I'm flying a glass warrior for my instrument training right now. I have the checkride coming up in the next week or two, and I need to learn a little bit about the AHARS (Airborne Heading-Attitude Reference System) for the oral. I was just curious if any of you guys could help me with this. Do you know anything about it, or can you direct me to a place that might help me? Thanks a lot!

Here's what I remember....

Roughly, it is a system which uses accelerometers (solid state) and/or ring laser gyros to measure changes in the aircraft's attitude (pitch and bank) and heading. Starting from a know position, the system measures, and totals (or sums) all accelerations about any axis to keep track of the current attitude/heading.

Ring laser gyros are devices which send a laser beam around a circular course (with mirrors or maybe fiber optics). When the platform is stable (no motion) the laser will complete the circle and arrive back at a known specific point. When the platform changes attitude, the laser beam in between the mirrors continues in it's original direction while the platform, mirrors and sensors move...this means the beam will arrive at the end of the loop slightly misaligned from where it would have been. The system measures the amount of misalignment and determines the amount of motion which caused it...very precisely.

These systems don't suffer from gyroscopic precession and are far more precise than mechanical gyros. Since it's all solid state with no mechanical parts it's much easier to digitally translate the data to a CRT or LCD display format. They are not perfect however, and will gradually lose their reference due cumulative errors over a long period of time...but this period is probably longer than most GA or even commercial flights.

wow thank you I really appreciate the help!

Take it from this old salt....

If your plans involve flying professionally some day, don't wait until a week before an important checkride to 'ask the guys' about a piece of equipment that you need to know about for it...

That said, good luck!

I respect your input especially considering that you're a professional pilot and that is where I want to end up in a few years. But I personally think that if all I need to study at this point, 7-14 days prior to the important checkride, is the AHARS system out of all of the tough topics on instrument training, that's a pretty good job well done with my studying... literally, all I need to do is learn a few things about AHARS and I'm good to go. We're not expected to be experts on the system (not until the CFII course). In fact some of the examiners here don't even touch the subject with the students. So in that fact, I think I'm going a little above and beyond in trying to learn about it, and I think over a week is more than enough time to learn about this stuff.

Ummmm.....ok.

Like I said....good luck.

you might want to google "mems ahrs"

or read this article in flying magazine

cheers
george

I assume you're using a G1000 equipped Warrior. I don't think they put Avidyne's system in there, but feel free to correct me if need be. Rickair was right on. The G1000 use solid state accelerometers to measure the changes in attitude and has a magnetometer to measure mag heading.

Advice: You are never going above and beyond to learn a system perfectly. Strictly speaking, that's the requirement. In practical application, it is a difficult thing and examiners know students are nervous and inexperienced. This usually means they are willing to teach a little and give advice as long as you know what the heck you're doing. But you don't learn a system to pass a ride. Learn the system so that when something breaks, you are as prepared as humanly possible.

That was the point I was attempting (poorly) to make. Thanks for clarifying!

The Pipers use the Avidyne FliteMax glass cockpit.

Guys, give him a bit of a break too. I went through the same course as him and the school doesn't teach AHARS or ADC to the level that they need to at all. All they tell you is that there's two boxes up front that have accelerometers in them that translate movement into a form similar to the old round dial instruments. They leave you on your own to go out and find more detailed information on the topic.

PiperPower, one thing you'll need to know about the Avidyne glass system is that it can't realign in flight like the Garmin G1000 can.

Good Luck on your stage check.