A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Fergus Kavanagh
Date: 2016 Mar 16, 17:09 -0700
What is equally curious is the lengths to which KH went to with the interlocks to prevent opening the hatch without a sextant in the tube, when Kollsman didn't bother with an interlock at all. I know the tube diamater is greater on the KH, but still.
The KH interlock is built like a brick outhouse. I spent a long weekend attempting to extract the seized locking bolt from the slot (unsuccessfully), before reluctantly breaking the mechanism from the housing. Subsequently fitted the sextant only to find that somewhere in the very distant past, the entire mounting had been removed and re-installed 90deg out of the correct orientation, so the graticule could not be centred correctly. When I removed and re-oriented it, all was well, and at the correct orientation the removal of the locking bolt would have been fairly easy. Ah, hindsight is 20-20.
You will have gathered from the above, David, that the Mk2a sextant can be fitted in the Mk1 mounting, except the azimuth ring is not the correct diameter.
The sextant protrudes a similar amount as the Kollsman in the 707 does, so I assume it is more or less correct. (See attached photos).
A question, if I may. The DC-7 has a transparent panel to the left of the sextant mount, with a relative bearing scale marked at 30deg intervals. What was the purpose of this ?.