Well, my old Sperry Artificial Horizon has a ground pointer. Exactly like the sky pointers on the various electronic instruments shown, except it points at the ground.
Personally I’ve never really used the sky or roll pointer to know which way is “up” – the brown bit being on the bottom and blue bit on the top tells me that, which is I think the most critical information, and every device made in recent history puts the blue on the top and brown at the bottom (old Soviet instruments used to really actually be upside down – depicting the ground on the top and sky on the bottom – I guess it was easier to make a gyro that would work in aerobatics since you didn’t have to reverse the motion of the physical gyro to present it on the face of the instrument, which generally means you’re going to hit some limits of motion sooner rather than later). I only use the pointer, whether sky or ground or whatever, to determine degrees of bank not which way is up. The brown bit and blue bit is far more intuitive for telling me which way “up” actually is.
It may have been critical information in the distant past, for example, my old Sperry Artificial Horizon, which depicts the horizon as a simple white line on a black background, so the only way of telling which bit is the “sky” and which bit of the “ground” is that the pointer is pointing at the right bit of the instrument (in this case, the bottom half).
JasonC wrote:
Adam, if you read the thread it is about roll pointer vs sky pointer. Nothing to do with the horizon line.
I can understand the confusion. I had to read the thread and look at the pictures several times before I understood what everyone was talking about.
I share my flying time about equally between G1000-equipped aircraft and aircraft with a mechanical AI and I had not even noticed that the pointers were different!
In the old Russian AI design the plane rolls (relative to the instrument panel), not the horizon. Very different if you’re accustomed to the Western types, but I actually think it’s more intuitive.
Gets even more confusing when the Russians put ground and sky the opposite way!
On a side note and from an ergonomics point of view interesting how the Space Shuttle has the speed scale upside down on the HUD – eg. the pointer “moving up” (or the scale scrolling down) indicates slower speed.
You wanna get really confused?
Could not find a “real” pic (need to do make a video next time I fly one) but heavens if that horizon did not confuse the heck out of me when i first flew it.
Seems like everyone uses the sky pointer now (it was alluded to in a document in this thread that the military used ground pointers, IIRC). Spotted this pic on another forum:
what_next wrote:
Never the traditional mechanical one in your top picture (the mechanical ones from Russia – I am told – work the opposite way, just like our electronic ones).
Not really. The difference is that the “Russian type” has fixed horizon and it’s the plane symbol that moves. It’s really an attitude indicator, not artificial horizon. AFAIK this type of indication was repeatedly shown as superior to the prevalent western type with fixed aircraft symbol and movable horizon. They could, however, have the pitch axis reversed.
Peter wrote:
The illustrations are not great. In this one, I think the leftmost one is the KI256 but I can’t tell which of the other four is the Sandel [picture] I think it is one of the last two.
Neither is the KI256. The middle one is the standard artificial horizon and the arrangement (movable pointer or sky pointer) corresponds to the commercial AI’s. You’ve probably never seen either kind of the other four (the left two are fixed horizon types and the right two are stabilized sphere types, although the rightmost is similar in indication to the standard AH).
Peter wrote:
This table is telling: [picture] The traditional AI is the best of them for roll control but the last ones are better for pitch. However all of them are OK for pitch and this is exactly what I find: the KI256 is best for roll control but the Sandel (with its sizeable and very clear horizon) is great for pitch control.
What? First and foremost it shows that the pilots performed best with the indicator they were used to as they all were quite experienced. Second best was the rightmost which is very similar. When they tested people without piloting experience, the results were very different. The good performance in pitch is not really surprising given that four out of five follow the same logic and the one that doesn’t is the one with the worst result.
That’s the Yak18 right?
