Just a question that was bugging me, why do some aircraft have eyebrows. I know that they were common on older aircraft, but they aren't on any new aircraft. That must mean they aren't necessary, so why were they on older aircraft? Would it be for navigation? I know that some 717 have them and some not, and that on later aircraft they were removed to save weight. So why were eyebrows so popular on older aircraft?
Quoting KELPkid (Reply 3): IIRC, the CAR's of old (predecessor to the FAR's) required a certain field of view for the captain and first officer, including the ability to be able to get a good visual scan upwards...
It is still considered "ideal" for an aircraft to offer 40 degrees of vision above the horizon when the captain is looking between 85 and 95 degrees left, or the first officer the same right. In some cases eyebrow windows were considered the optimum way of offering that field of view, given that a few larger window assemblies can be heavier than several small window assembloes as flight deck windows must resist birdstrike.
Perhaps one of the certification gurus can comment, but my understanding is that they were put there to meet cross-cockpit visibility requirements at the MDA on a circling approach. They have (obviously) been found to not be needed, so they can be removed on some types now.
I detest them; they do effectively nothing for visibility, but make for much hotter cockpits, and are difficult to shade when the sun is peering through them at just the wrong angle...which leads to a lot of improvised shades normally made from some type of paper easily found in the cockpit.