Originally Posted by V1... Ooops
Looking at pictures of 737-500 flight compartments, I cannot see any evidence of an 'occluded sphere' type reference device installed on the windshield center post. Did Boeing use a different type of 'fixed marker or other guide' on these early 737s to comply with this FAR, and if so, what methodology did they use? Or, were these aircraft built to a certification basis that preceded publication of FAR 25.773 (d)?
Many thanks in advance for any light that an expert could shed on this question.
Well, there are probably several reasons for this … first, the B-737-300 was the first design to follow-on behind the B-737-200 Advanced model and the B-737-400 was the “larger version” of the -300, and the B-737-500 was the “smaller version” of the -300. Initially, there well may have been some sort of alignment indicators installed in the -300 that occluded one another with the pilot’s eye position properly placed. However, when follow-on models of essentially the same aircraft were developed and placed into service, a quick review of this proper eye position could be verified by, 1) being able to sight directly down the top of the glare shield; 2) able to clearly see the top annunciator lights above the flight instruments; and 3) able to see the bottom of the Electronic Horizontal Situation Indicator (EHSI). If this turned out to be accurate, there just may be little need to install (and maintain) the occuluding sphere references. If you check the flight crew operating manuals for the B-737-500, I think you’ll find this “3-line-of-sight-references” included as the method accepted for determining proper pilot seating position in the -500 series aircraft.