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  Mercury - Gemini - Apollo
  Apollo 11: '413 is in' type of command

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Author Topic:   Apollo 11: '413 is in' type of command
Ponyhorton
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Posts: 9
From: California
Registered: Sep 2018

posted 12-22-2018 10:39 AM     Click Here to See the Profile for Ponyhorton   Click Here to Email Ponyhorton     Edit/Delete Message   Reply w/Quote
When the Eagle landed on the lunar surface, Buzz Aldrin went through a quick checklist...
ACA out of detent. Mode Control, both Auto. Descent Engine Command Override OFF. Engine arm OFF. 4-13 is IN.
Was 4-13 a circuit breaker, or a DSKY command?

thisismills
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Posts: 150
From: Michigan
Registered: Mar 2012

posted 12-22-2018 11:37 AM     Click Here to See the Profile for thisismills   Click Here to Email thisismills     Edit/Delete Message   Reply w/Quote
In short, “413 is in”, told Eagle’s Abort Guidance System to remember the attitude of the vehicle on the surface.

A more detailed explanation courtesy of the Apollo Lunar Surface Journal.

'413' is an AGS address and has been a topic of considerable interest to Journal Contributors Marv Hein and Frank O'Brien. Frank supplied the following description.

O'Brien - "(The AGS is) a wonderful machine. If you have done any work on a computer that just has a switch register and display (such as an IMSAI, ALTAIR or one of my favorites, the KIM-1), you'd be comfortable with the AGS."

"The way the AGS operated is that you had only an address and data display, 0-9 keypad, a Clear button, plus +/-, Enter and Readout. That's it. The ultimate in simple interfaces! How the AGS was operated was to press Clear, then a memory address. On a 5-octal character display, you got what was stored in that location. To change it, you typed a +/-, followed by 5 characters. Pressing Enter stored the value directly into memory. What you hear is the checklist item noted as: 413+10000. The key sequence is Clear, 413, Enter, +10000, Enter."

"Address 413 contains the variable that indicates that the LM has landed - so any abort will be from the surface - which further tells the AGS to save the attitude information from its gyros. These gyros were 'strap-down' types, which means that they had a fixed orientation with respect to the LM body. They also had a nasty habit of drifting quite a bit. So, as soon as they landed, the AGS was to 'lock in', if you will, the attitude the LM was in. If the PGNS died - and it was the PGNS that oriented and re-aligned the AGS - at least they would have some approximate attitude information to abort with."

Ponyhorton
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Posts: 9
From: California
Registered: Sep 2018

posted 12-22-2018 02:21 PM     Click Here to See the Profile for Ponyhorton   Click Here to Email Ponyhorton     Edit/Delete Message   Reply w/Quote
Thank you so much for this detailed info! I really appreciate it!

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