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Robert R Pastusek wrote:
This would allow me to receive and display WX Works weather and to display
approach charts and a moving map driven by the laptop.
Have any of you considered/tried this arrangement? Other comments?
Oh we have been through this many times. Here is a partial list of issues to consider:
Will you have enough space for the display and the laptop tray? I would suggest nailing this one definitively with actual numbers before digging any deeper -- spaces appear bigger than they actually are.
Will the display be bright enough for daytime operations?
Will the display be dim enough for nighttime operations?
Will the display have enough viewing angle to be seen from the pilot's side?
How will you control the laptop? Do you need a keyboard or a mouse and where will you put it? How will you access it? If you are planning to go the touch screen route, will you actually be able to reach over and control the program while sitting in the pilot's seat? Will a touch screen alone be enough? What about in turbulence?
Will the approach plate displayed on the screen that you choose be of a good enough resolution that you can reliably read it from you position in the pilot's seat? This includes reading all the "fine print" as well as the big numbers.
Hard drives do not do well at altitude or in high vibration environments. While high altitude is not a problem for you since you are pressurized, what happens in the event of a pressurization failure? Unless you are planning to put in a turbine, you do need to think about vibration, maybe even with a turbine.
This one is a non-issue for you due to pressurization, but I will mention it for completeness' sake: The thin air at high altitudes does not do a good job cooling things. The CPU and the power supplies on a laptop are air cooled. Will they stay cool enough at altitude?
Laptops are designed to run at room temperature or maybe as hot as 45C. How hot will it get in your drawer, since it is for all practical purposes located behind the panel along with all your heaters, err.... I mean avionics.
Are you going to run exclusively on batteries, or use the airplane's power through one of the commercially available car adapters? In the latter case, think about size, cabling, cooling/temperature and load on the electrical system, especially if you happen to plug in a laptop that has partially discharged batteries (you are using the airplane's power to charge the laptop battery as well as run the laptop).
Will you have EMI problems? The DO-160E curves get more stringent in the Nav/COM band, while the FCC part 15 curves get less stringent in that band. Many, maybe most laptops will work without a problem. You are essentially taking the route of "try it on the ground and make sure it works" which is an acceptable approach -- or is it? The DC-DC power supply chips used on modern motherboards are often of the "constant off time" variety rather than the constant frequency variety. This means the the primary frequency of the power supply depends upon the load seen by that power supply. This means that if the load changes, which is likely to happen in the Windows environment, the power supply harmonic that was sitting just outside the Nav/COM band just moved in the band and is now taking out your ILS. Or maybe it just took out your GPS. Since you did not do an EMI scan on the laptop to characterize it, you have no idea that a harmonic is sitting just around the corner ready to nab you. Granted that this is not a very likely scenario, but you need to know of the risk before taking it.
And last but not the least, after you address all of the above issues: If you are planning to consult the approach chart while running on instruments in IMC, you are setting yourself up for spatial disorientation by swinging your head from side to side to look at things that are that widely separated.
Bottom line: It can be done, it has been done, but it is not as simple and straightforward as it first appears. The devil is in the details and there are a lot of them to consider.
My biases due to may affiliations with Chelton as well as EFB (Electronic Flight Bag) designs for Northstar, CMC and others are well known blah blah blah.
Hamid
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