Help with Optics Question...

[idleup]

I did not know where else to turn so I am hoping someone on this forum can help or put me in touch with someone who can help.

I recently acquired a transparent LCD screen. I want to put this on the dash of my airplane to create a Heads-Up-Display. My only problem is that I need to "Focus it at Infinity". How would I do this? The professional Heads up systems are focused at infinity so the pilot can look through the window and focus on objects outside without loosing focus of the information in their HUD. This is an issue of optics and since I am not projecting the image onto the surface I cannot use traditional collimating techniques. Can anyone help with this???


- Matt

[rbaker]

Optically “focus at infinity” should not be an issue due to the distance between the eye and the windshield (dash ?) being greater than 30 inches. It will, for certain, be an issue with the FAA. As far as I know, there is no such system with an STC. Additionally, I do not think that it would ever find any acceptance by pilots particularly with the new glass cockpits that we are seeing even in general aviation aircraft.

However, don’t let that distract you from what may be an interesting project. To address the focusing issue just use your laser printer and print a graphic representation of the flight data on a sheet of mylar – like you were making an overhead, tape the sucker to the inside of the windshield and note that you do not have to accommodate.

[idleup]

Dick, that is a great idea to print it on mylar and test it to see if it is an issue. The idea is primarily for the Home built market as I am building a Van's RV-7A. As for it ever catching on due to glass cockpits, I dont know. The concept is really to extend the glass cockpit as I would be interfacing into an EFIS to get the data projected to the HUD. I want very basic information that is important on landing like AOA, Airspeed and Alt. Stuff that I dont want to take my eyes off off final approach but is important to know... but for now it is just a hobby project anyway.

P.S. What is Aerovisiontech? Sounds like a business but the website looks like a personal website.

- Matt

[rbaker]

Matt,

First of all, I want to apologize to all the pud knockers out there . . . but were talking aviation here, not optics. My web site was my business site before my company was sold when I retired in 2000.

Good luck with the RV-7. There are quite a few assorted RV’s here on the Connecticut Shore. I spend half the year in Southern Oregon and have a Pietenpol in the works which will hopefully be flying this Fall. I have been putting it aside awaiting the arrival of the Corvair conversion that is being built. We are also in the market for a PA-32 or C-210 although the wife would really prefer twin. Ahhh well . . . you probably know how that goes.

I was a Naval Aviator in the Marine Corps back in the sixties and flew behind some of the earlier HUD’s and I was never overly impressed with them. I actually found them distracting at best and a damned nuisance at times. Varying lighting conditions combined with varying environments can cause a lot of problems. What works OK under bright CAVU conditions can be quite problematic on a night IFR trap on a pitching flight deck. I do understand that improvements have been made and there is quite a bit of difference between a F4 Phantom and an RV-7.

Your biggest problem will be cockpit lighting and environment lighting conditions. Try a variety of mylars in you car as you drive around for a week or so. It should also allow you to modify the size and width of the flight graphics that you will ultimately display.

Since your proposed system will be restricted to VFR flying and you stated that your principal goal was primary panel info on landing I have to make the following observations. You really do not want to be fixating you vision directly straight ahead on landing. You want to be eyeballing the airspace all around you in the pattern and right down to the runway threshold and into the flair. At this point your primary height information is going to be purely visual perspective at 10 – 11 o’clock and 1 – 2 o’clock – not straight ahead.

Also. you do not want to fixate on your airspeed to the extent of blocking out everything else. In addition, you have too many other airspeed inputs to give you better info such as sound and control feel. If you can not sense and recover from an impending stall without reference to the airspeed indicator you had best stay on the ground. In brief, all of the information that your brain needs to process in order to perform consistently good landings comes in through the sight and sound of a 45 degree cone ahead of the aircraft. The only thing that you care about from the flare to stop is keeping the nose of the aircraft pointed at the far end of thee runway with the rudder. All else is peripheral perception and holds true whether we are flying RV-4s or Boeing 747s.