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Some other questions about HUDs and how they work got me thinking. Military aircraft have had reflector sights since before WWII, and full HUDs since the mid-70s. The very same display layout, sans targeting recticles, is fairly familiar to pilots of glass-cockpit aircraft, the primary difference being the representation of the artificial horizon (which, because the display is not a HUD and so not transparent, uses the blue/brown background from the analog instrument).

True HUD systems are starting to make their way into commercial airliners, and the technology is even seen in various cars (primarily luxury brands) as a situational awareness tool. So the question is, what types of reflector-sight flight display systems are available for light singles? I would assume a glass cockpit is a prerequisite to generate the digital display, but given that concession, it seems fairly straightforward to have a monochrome version of the PFD projected onto a glass plate instead of or in addition to the display on the LCD monitor. Has anyone marketed this? Are there disadvantages of having a HUD in a GA aircraft that I'm not thinking about? This sounds like a natural next step now that even entry-level LSAs are foregoing the traditional analog 6-pack for glass displays.

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  • $\begingroup$ I'm sure the main disadvantage is cost. Other than that, I haven't heard anything about GA HUDs $\endgroup$ – SSumner Aug 22 '15 at 14:01
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    $\begingroup$ Yeah, that's just what I need, a HUD, so I can cut off other guys in the pattern much more sharply while maintaining situational awareness. $\endgroup$ – Tyler Durden Aug 23 '15 at 22:55
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It looks like there have been several attempts at coming up with viable HUDs for light singles but none have, well, taken off (business jets are a different story):

  • The VirtualHUD company mentioned in this article doesn't exist any more
  • The G-HULP exists and you can buy it but I couldn't find any useful information about it or even the manufacturer's website

Since there's really nothing much out there, it suggests that HUDs for light singles are too expensive for typical pilots and/or just not useful.

Cost is always relative, but the standalone G-HULP costs USD 6,000 and that has to be compared to other, potentially more useful things like avgas (i.e. flying time!), avionics upgrades, ADS-B or just general maintenance.

But even if a GA pilot has nothing better to spend his money on, it isn't clear that HUDs are actually as useful as you might think. This article looks at a new Honeywell system for business jets that overlays a HUD view on the PFD, and they compared the landing precision of 'heads-up' (traditional HUD) vs. 'heads-down' (HUD on the PFD) pilots:

A chart that showed landing points at the end of approaches flown by pilots using the two systems showed scattershot points with no apparent bias toward either system. Both systems allowed their pilots to fly very accurate approaches.

This result, Ververs says, surprised the pilots in the study who had a lot of HUD time going into the testing. They had all assumed, she says, that the HUD would be the better technology. As far as the testing experience could show, it wasn’t better [...]

Of course that's only one specific testing scenario, but it's a very critical one because landings are when you really need to see and react quickly. Personally, I'm not convinced that focusing my eyes on the HUD for airspeed and then through the HUD to the runway would be any quicker or easier than just flicking my eyes between the airspeed indicator and the runway centerline. (Jan Hudec made the comment that focusing shouldn't be an issue with a "good" HUD, so this may not be an issue at all, at least in theory.)

And there are probably other issues with a HUD too, like making an instrument scan more complex; making the pilot focus his vision on the HUD rather than into the distance; or just being a general distraction.

There is an interesting alternative concept to a fixed HUD, by the way: wearable tech. Whether it's any more successful remains to be seen.

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    $\begingroup$ In a good HUD the image is formed at infinity, so you don't refocus your eyes between the HUD and outside. $\endgroup$ – Jan Hudec Sep 2 '15 at 7:44
  • $\begingroup$ @JanHudec Thanks for that, I have zero experience with HUDs so it's good to know. I've updated my answer. $\endgroup$ – Pondlife Sep 2 '15 at 12:59
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    $\begingroup$ I don't have experience either, but I did try to understand how they work. $\endgroup$ – Jan Hudec Sep 2 '15 at 15:19

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