Slpshot
Maybe this will help.
Each gunsight display has a center point, sometimes called the "pipper". This center point has different meaning, depending on whether the sight is being used for forward firing projectiles (bullets and rockets) or free-falling ordnance (unguided bombs).
In the first case, the center point is meant to indicate projectile impact point. The assumption is that the aircraft is wings level and at a particular speed and altitude. For WW2 planes, that point is also the convergence point for guns mounted off the aircraft centerline.
In the second case, the center point is used as a reference that indicates when the bomb fall line intersects the ground. This concept is far more complicated than the one above. For more detail, see the A2G series at SimHQ.
Back to A2A. The attacking pilot has to solve three variables: range, target plane of motion, and lead angle. If the center point is designed to indicate bullet position at some point in front of the attacker's plane, then all other markings are intended to help the pilot solve range, plane of motion, and lead estimation.
The gunsight designer begins by establishing the scale of the display. This means he sets the dimensions of the display to represent a given range to the target. The simplest reference is the gunsight reticle. The designer intends that the diameter of the reticle is sized such that an enemy aircraft wingspan will equal the reticle diameter at that given range. Other types of display markings (lines, X's, tick marks, etc) all do exactly the same thing. The pilot simply compares target size to his display to estimate range...he knows what range he wants, so he closes on the target until it is the desired size relative to the sight markings.
Next is target plane of motion. The attacker wants to get his gun line into the target plane of motion. Gunsight designers help the pilot estimate this by adding angular lines (radii) that intersect the pipper. The idea is that the pilot lines up one of these lines with the target's flight path...by maintaining the target flight path along this line, the pilot is flying in or close to the target's plane of motion.
Lastly is the estimation of the lead angle. The reticle can be used for this purpose as well, as is explained in that RAF article. Sometimes additional reticles are included ( a circle within a circle), or other markings set at some distance from the pipper are also used. Regardless of how these look, they are used to estimate angles...the observed angle of the target from the pipper. This angle is the amount of lead needed for target motion. Of the three parameters, it is the most significant and the one most often miscalculated.
Here is a typical A2A sight. It has a center pipper for bullet impact point (corrected for convergence), a circular reticle segment used to estimate range and lead angle, and radii used to help track the target's plane of motion.
If you read the A2G articles, you are now familiar with the term "aim off distance". The A2G sight has to allow the pilot to accurately point his flight path at that aim off distance. Then the pilot must accurately fly along the planned dive angle and airspeed while keeping his flight path on the aim off point. At some point in the dive, he will be at an altitude that is the release point. The gunsight designer has to add markings to tell the pilot when he is at that point. It is critical to note that this marking is only valid for one type of weapon, one release altitude, one dive angle, and one release airspeed.
To deliver the bomb, the pilot aims his sight at the aim off point. Sometimes the pipper is used for this...the assumption is that the pipper is on or close to the attacker's flight path. In the dive, the pilot holds the pipper on his aim off point and flys down the planned dive angle. The target will appear to move "up" the gunsight towards the center. At some point the target will be at a point below the pipper that represents the release point. The next figure shows one way to display this. Note the short "peg" at the bottom of the sight display. The pilot aims his pipper at the aim off point and then waits for the target to move up until it touches the top of the "peg". Then the weapon is released.
Whew!! Now...all of this doesn't do much good unless the sim developer tells us how these sights are designed and what the markings actually mean. I can't help you there...I'm as clueless as everyone else on that score.
Andy
