Editing Head-up display (section)

=== Displayed data ===
[[File:Heads up display symbology.png|thumb|right|Displayed data symbology of a head-up display]]
Typical aircraft HUDs display [[airspeed]], [[altitude]], a [[horizon]] line, [[Aircraft heading|heading]], turn/bank and [[Slip indicator#Turn coordinator|slip/skid]] indicators. These instruments are the minimum required by 14 CFR Part 91.<ref>{{cite web|url=http://www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgFAR.nsf/MainFrame?OpenFrameSet |title=14 CFR Part 91 |publisher=Airweb.faa.gov |access-date=2009-10-02}}</ref>

Other [[symbology (avionics)|symbols]] and data are also available in some HUDs:
* ''boresight'' or ''waterline'' symbol — is fixed on the display and shows where the nose of the aircraft is actually pointing.
* ''flight path vector (FPV)'' or ''velocity vector'' symbol — shows where the aircraft is actually going, as opposed to merely where it is pointed as with the boresight. For example, if the aircraft is [[Flight dynamics|pitched]] up but descending as may occur in high [[angle of attack]] flight or in flight through descending air, then the FPV symbol will be below the horizon even though the boresight symbol is above the horizon. During approach and landing, a pilot can fly the approach by keeping the FPV symbol at the desired descent angle and touchdown point on the runway.
* ''acceleration indicator'' or ''energy cue'' — typically to the left of the FPV symbol, it is above it if the aircraft is accelerating, and below the FPV symbol if decelerating.
* ''[[angle of attack]] indicator'' — shows the wing's angle relative to the airflow, often displayed as ''"α"''.
* navigation data and symbols — for approaches and landings, the flight guidance systems can provide visual cues based on navigation aids such as an [[Instrument Landing System]] or augmented [[Global Positioning System]] such as the [[WAAS|Wide Area Augmentation System]]. Typically this is a circle which fits inside the flight path vector symbol. Pilots can fly along the correct flight path by "flying to" the guidance cue.

Since being introduced on HUDs, both the FPV and acceleration symbols are becoming standard on head-down displays (HDD.) The actual form of the FPV symbol on an HDD is not standardized but is usually a simple aircraft drawing, such as a circle with two short angled lines, (180 ± 30 degrees) and "wings" on the ends of the descending line. Keeping the FPV on the horizon allows the pilot to fly level turns in various angles of bank.