@ Dozy,
Your Quote:
Let's be pragmatic though, the primary reason HUD is considered essential in fighters (and is therefore cost-effective in all cases) is not because of the fact it can complement the primary instruments so much as the fact that in a fighter you're going to have people shooting at you, and when that happens a split-second glance at the panel can mean the difference between life and death.
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Wrong...
I think you are somehow stuck in a time warp regarding HUDs, as if it were the old movies of dogfights in WWII or the Korean war when HUDs were not available. The purpose of HUDs had nothing to do with being shot at, but everything to do with accurate shooting at a target. Some American & British history regarding HUDs:
In 1955 the US Navy's Office of Naval Research and Development did some research with a mock HUD concept unit along with a sidestick controller in an attempt to ease the pilots burden flying modern jet aircraft and make the instrumentation less complicated during flight.
HUD technology was next advanced in the British Buccaneer, the prototype of which first flew on 30 April 1958. The aircraft's design called for an attack sight that would provide navigation and weapon release information for the low level attack mode. There was fierce competition between supporters of the new HUD design and supporters of the old electro-mechanical gunsight, with the HUD being described as a radical, even foolhardy option. The supporters won. BAE Systems thus has a claim to the world's first Head Up Display in operational service.
In the United Kingdom, it was soon noted that pilots flying with the new gun-sights were becoming better at piloting their aircraft. At this point, the HUD expanded its purpose beyond weapon aiming to general piloting.
Gilbert Klopfstein created the first modern HUD and a standardized system of HUD symbols so that pilots would only have to learn one system and could more easily transition between aircraft. Klopfstein pioneered HUD technology in military fighter jets and helicopters, aiming to centralize critical flight data within the pilot's field of vision. This approach sought to increase the pilot's scan efficiency and reduce "task saturation" and information overload.
Aircraft HUDs generally contain:
- 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, the sum of all forces acting on the aircraft. For example, if the aircraft is pitchedup but is losing energy, 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 Systemor augmented Global Positioning System such as the 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.
Until a few years ago, the Embraer 190 and Boeing 737 New Generation Aircraft (737-600,700,800, and 900 series) were the only commercial passenger aircraft available with HUDs. A HUD is standard equipment on the Boeing 787. Furthermore, the Airbus A320, A330, A340 and A380 families have undergone the certification process for a HUD.
So if you want to be pragmatic regarding HUDs on most commercial aircraft today, I think
Clandestino gave the correct answer, it all has to do with money, ROI and such.