Problem with P63 and checklist

Sverige

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I'm completely stuck and need help. I am doing staff in LM (Apollo 11). I have done my DOI and am preparing PDI. Here are a lot of things I do not understand but I try to follow the checklist as best I can. P63 start as it should but then strange things happen when the warning light for PROG, sometimes also ALT is lit late. P63 does not start P64 but I crash slowly against the surface. Am I doing something wrong with the landing radar? Grateful for detailed help. Sends with quick saves that I start from.
 

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Not quite sure how to add a file
 

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  • Apollo 11 MCC - LM_AOT_32 0001 0001.scn.txt
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indy91

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That scenario is a bit early, that's right after DOI. It's not like I don't want to fly this scenario the hour to PDI, but it's also possible that a procedural error after this scenario is the cause of the issue. So do you maybe have a different scenario where the same issue appears, maybe a few minutes before PDI?
 

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Thanks! I was wondering if there was anything wrong even before P63 so I sent it. I will continue my experiments tonight and if the problem arises, I will save immediately. I can take a few quick saves one after the other just before the crash. Another question I have is 231 RLS with yellow text in the checklist. It should be keyed into DEDA but I do not know what RLS means and where do I get those numbers from? Thanks for all the help Indy.
 

indy91

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I will do a few checks in that scenario then, state vector etc.

RLS is radius of the landing site. The AGS uses the value stored in address 231 as the reference for altitude calculations.

The procedure you are doing there is to prepare a manual state vector update on the lunar surface. The thought process apparently was, the state vector that the AGS has using accelerometers etc. after landing is very imprecise. And you could give it a more accurate state vector by updating the AGS with one landed at the desired landing site. And that is what you are preparing there. In address 262 you load the inertial velocity while on the surface, due to Moon rotating. That is the -00150 (15 ft/s). And you also give it a state vector time tag of the planned landing time. That is the "254+0767.2 (TLAND)" in the timeline book.

And the checklist line you are asking about is "240+ (231 RLS)". Address 240 is part of that landed, manual state vector update you are preparing. And you want to have it exactly at the landing site. So what you want to do there is load whatever you have stored in address 231 into 240. So you readout address 231, quickly memorize it and then load that value into address 240.

EDIT: State vector in the scenario seems fine. When exactly did you get the program alarm? Was it maybe when Average G starts in P63? And does the DSKY blank sometimes so that you have a hard time checking the program alarm with V05 N09? Then it could maybe be an issue with the resetting of a LR related flag. There is a bug in the Apollo 11 software that requires you to reset a flag every time you do the LR self test procedure. The resetting of the flag is done with: V25 N07E, 110E, 40E, E. Maybe you forgot the last enter or so?
 
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Sverige

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Thank you for a detailed and interesting answer. I finally managed to land and the problem turned out to be Des Eng CMD Ovrd on ON before PDI initialized. What function does this button have? Now and then drop RR I got No track light ON the Alt lamp was also turned on. I tried manual slew to get RR signal with varied result. Anyway, it went well to land. However, I could not find any redesignator function, Is this function available and which keys in that case?
 
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indy91

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The Descent Engine Command Override switch is only used during powered descent and it is a redundant signal to keep the DPS engine running. What you definitely don't want to happen is that some short power interruption causes the DPS engine to switch off when you are hovering above the surface, even for a short moment that is of course dangerous. So to have some more redundancy you force the engine to run with that switch. And only pressing the engine stop button will shut down the DPS then. But I am not quite sure how it could have caused your issue, was the DPS suddenly running when you armed the engine or so? I guess if it runs to early the guidance will of course be in trouble.

Loosing lock on the CSM will happen during the descent, early or later. That's no problem.

The altitude light will be on once P63 starts looking for LR data but no "altitude data good" signal is provided yet. In the attitude at igntion it can't possibly lock onto the surface yet, the LR is pointing into space. After the 180° yaw maneuver the light should extinguish and you can allow LR data to be processed. The velocity light might also come on at some point. On Apollo 11 you might not get the velocity light at all because the software starts looking for velocity data later than the altitude data. On the later missions they let the software look for it earlier, then you will get both ALT and VEL lights at Average G start in P63.

You redesignate with the attitude controller, in the pitch and roll axes. (4+6 and 2+8 on Numpad). Once you are in P64 you press PRO on the DSKY and then it will accept LPD commands.
 

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Yes exactly! DPS was activated when I armed the DPS and this about 2 minutes before normal PDI activation with PRO (99, 5 sec). I had set the Descent Engine Command Override switch to ON to save time during the stressful checklist. I may have done something wrong but I think it was strange that the engine was active on low throttle before normal activation with PRO. However, your answers are very important for my understanding of the checklist.
 
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