AeroElectric-List Digest Archive

Wed 06/11/14


Total Messages Posted: 3



Today's Message Index:
----------------------
 
     1. 01:25 AM - Re: Direction Indicator Needs (GLEN MATEJCEK)
     2. 02:18 AM - Re: Direction Indicator Needs (Stuart Hutchison)
     3. 11:12 AM - Re Direction Indicator Needs (D L Josephson)
 
 
 


Message 1


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    Time: 01:25:55 AM PST US
    Subject: Re: Direction Indicator Needs
    From: GLEN MATEJCEK <fly4grins@gmail.com>
    > > Hi O.C.- RE: > > http://www.grtavionics.com/mini.html#Features > > is simply the indication of a remotely located magnetometer (which is > available for the Mini-X and Mini-AP, but not the Mini-B) then I don't > think > that will meet the intended requirement of 14 CFR 91.205 (d) (9) criteria > for a Gyroscopic directional indicator (directional gyro or equivalent). > > > I'm curious as to why you are concerned this hardware would be inadequate. It seems to me that it fits the bill and then some. To reference what Ryan cited: > > The dynon d6 pilot guide says "Like a conventional gyro-stabilized magnetic > compass, magnetic heading reacts immediately to turn rate so that heading > changes are reflected immediately. It then uses magnetometer data over the > long term to ensure that it remains correct. Additionally, heading is > corrected for attitude so that it is accurate as you pitch and roll. " > Sounds equivalent to a dg to me. > > This would be quite a bit better than a DG- It won't precess, doesn't need to be manually synced to a compass, and there are no bearings to wear out. If your concern relates to the display, there are many certified drum-type DG's still flying today. That's not my first choice for a display, but it does work. Thoughts?


    Message 2


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    Time: 02:18:00 AM PST US
    From: Stuart Hutchison <stuart@stuarthutchison.com.au>
    Subject: Direction Indicator Needs
    G=99day OC, We have the same issue in Australia, with policy anchored to antiquated analogue designs. CASA, our FAA, was slammed by most sectors of the Aviation community in submissions to the Federal Government review (still underway) over recent months. In my mind the installation should be =98no less safe=99 than existing IFR instruments. There is a LOT left to be desired in many S/E Type Certified IFR aircraft that depend on a notoriously unreliable single vacuum pump to drive the two most important flight instruments on the panel, the attitude indicator and the DG, neither of which are required to have a built-in failure flag. These two instruments usually also drive the autopilot! The compass is fast becoming totally obsolete alongside a certified GPS, perhaps several, that measure point-to-point track. Among other things, magnetic heading from the magnetometer helps calculate wind, but if you know the track and groundspeed, who needs a wet compass?! Flying limited panel on the =98backup=99 electric turn and bank indicator (which actually indicates rate of change of heading, not roll and is gimbal limited to about rate 1 or 2) is extremely difficult in rough weather, which has resulted in numerous fatalities. CASA has yet to agree that system safety can be achieved a variety of ways, not the least by full redundancy. The Garmin 1000 is not fully redundant, which is why there is a backup three-pack to complement the PFD/MFD. A second AHRS, ADC and magnetometer would be required to make the system fully redundant, but software is also vulnerable to latent bugs and multiple systems can be expected to behave the same way under the same preconditions, so alternative hardware or staggered software versions seems like a good idea to me. CASA is wedded to outdated TSO=99s, arguing that if a piece of equipment is required by the Regs, then it must be approved in one of the recognised ways. In the absence of a specific approval, in most cases, that means a TSO. CASA don=99t seem to care that the most recent TSO for attitude indicators was published via typewriter in 1959. We do not want Dynon, AFS, GRT etc etc to required TSO=99s, nor is it necessary in order to achieve the equivalent form, fit, function and quality intended by the TSO. Like the US, Australia will slowly adopt =98performance-based=99 testing for equivalent functionality of non-TSO flight instruments, but the authorities are moving at a glacial pace. I think it is statistically significant that there are thousands of Dynon, AFS, GRT etc etc systems being operated VFR in the AB(E) community without systemic issues that would preclude them being used for IFR. Heated pitots becoming overcome with trapped moisture/ice are unhelpful for the IFR cause, but these are known issues that can and will be overcome in due course. All this is in relation to flight instruments of course. Communication/Navigation/Surveillance (CNS) systems are a different matter and should be TSO=99d if we expect to fly IFR in/around airspace with airliners and paying passengers. Cheers, Stu From: owner-aeroelectric-list-server@matronics.com [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Owen Baker Sent: 11 June 2014 04:24 Subject: AeroElectric-List: Direction Indicator Needs 6/10/2014 Hello Aeroelectric and Avionics Listers, I know that there are many technically smart people on these lists and I would like to enlist your assistance. Picture this situation: There are hundreds (maybe thousands) of EAB (Experimental Amateur Built) IFR capable aircraft flying around with vacuum driven mechanical spinning mass gyroscopic attitude and directional indicators. A large percentage of these builders and pilots would like to (or need to) replace those indicators with something electronic (other than expensive electrical motor driven mechanical spinning mass gyroscopic) in nature and remove the entire vacuum system from their EAB. Replacing the attitude indicator does not appear to be a big problem in meeting the requirement of 14 CFR 91.205 (d) (8) =9CGyroscopic pitch and bank indicator (artificial horizon)=9D since there are several offerings available. Here are some: http://www.dynonavionics.com/docs/D6_intro.html <http://trutrakap.com/product/gemini-pfd/> http://trutrakap.com/product/gemini-pfd/ <http://www.grtavionics.com/mini.html> http://www.grtavionics.com/mini.html <http://www.sandia.aero/?q=node/80> http://www.sandia.aero/?q=node/80 But there does not appear to be available an electronic directional indicator that would meet the 14 CFR 91.205 (d) (9) criteria for a =9CGyroscopic directional indicator (directional gyro or equivalent)=9D if one believes that the Regulatory intended direction to be indicated must indeed be the current aircraft magnetic heading and not the current aircraft magnetic course (provided by GPS) over the surface. I feel that somewhere in the electronic magic that MEMS << https://www.memsnet.org/mems/what_is.html >> and AHARS << http://www.microstrain.com/inertial/3DM-GX3-25?gclid=CjgKEAjw2dqcBRC2q- LXjpfxjnQSJAAeYF5LUC4gvWycBVg6DDW_mzzSdTyyF3q0yoQHrT6ij9VbvvD_BwE >> represents there must be a practical, relatively inexpensive means of creating a direction indicator that will meet the intended requirements of 14 CFR 91.205 (d) (9). If so, I (and probably many others) would like to buy one for my EAB airplane. How about it experts (and entrepreneurs) are my desires hopeless and unrealistic? OC 'O C' Baker says "The best investment you can make is the effort to gather and understand information."


    Message 3


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    Time: 11:12:11 AM PST US
    From: D L Josephson <dlj04@josephson.com>
    Subject: Re Direction Indicator Needs
    MGL also makes 2-1/4" and a 3-1/8" round-hole-mount displays for their AHRS and compass modules. It's about $1300 for attitude, TC and DG, or $500 for direction only, including the sensors. It would be up to you to be certain that these are equivalent to gyroscopic instruments. The sensors don't contain spinning masses but sense acceleration and attitude with multiple single-axis vibrating structures instead. The basic sensors are quite cheap; you can get a "10 degree of freedom" sensor module on a pc board for under $12 which includes 3 axes each of attitude, acceleration and magnetic field plus a barometric pressure sensor. Computations that used to take 30 pounds of synchros can now be done with a Kalman filter running on a fifty cent microcontroller chip.




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