posted 05-13-2020 11:10 AM               

100 feet, three and a half down...

60 feet, two and a half down...

posted 05-13-2020 11:52 AM               

As the descent progresses Aldrin calls out cues and vital information while Armstrong looks out the window, you can trace the altitude and velocity throughout the radio transcript. Also note Aldrin calls out horizontal velocity and references the lunar module (LM) shadow, the dust caused from the LM descent engine plume interaction with the lunar surface.

As the LM approaches the surface the rate of descent reduces to almost zero about the time Aldrin note that they are "drifting to the right a little."

04 06 42 41 CC
Eagle, looking great. You're GO.

04 06 42 58 CC
Roger. 1202. We copy it.

04 06 43 01 LMP (EAGLE)
35 degrees. 35 degrees. 750. Coming down to 23.

04 06 43 07 LMP (EAGLE)
700 feet, 21 down, 33 degrees.

04 06 43 11 LMP (EAGLE)
600 feet, down at 19.

04 06 43 15 LMP (EAGLE)
540 feet, down at - 30. Down at 15.

04 06 43 26 LMP (EAGLE)
At 400 feet, down at 9.

04 06 43 29 LMP (EAGLE)
... forward.

04 06 43 32 LMP (EAGLE)
350 feet, down at 4.

04 06 43 35 LMP (EAGLE)
30, ... one-half down.

04 06 43 42 LMP (EAGLE)
We're pegged on horizontal velocity.

04 06 43 46 LMP (EAGLE)
300 feet, down 3 1/2, 47 forward.

04 06 43 51 LMP (EAGLE)
... up.

04 06 43 52 LMP (EAGLE)
On 1 a minute, 1 1/2 down.

04 06 43 57 CDR (EAGLE)
70.

04 06 44 04 LMP (EAGLE)
Watch your shadow out there.

04 06 44 07 LMP (EAGLE)
50, down at 2 1/2, 19 forward.

04 06 44 13 LMP (EAGLE)
Altitude-velocity light.

04 06 44 16 LMP (EAGLE)
3 1/2 down, 220 feet, 13 forward.

04 06 44 23 LMP (EAGLE)
11 forward. Coming down nicely.

04 06 44 24 LMP (EAGLE)
200 feet, 4 1/2 down.

04 06 44 26 LMP (EAGLE)
5 1/2 down.

04 06 44 31 LMP (EAGLE)
160, 6 - 6 1/2 down.

04 06 44 33 LMP (EAGLE)
5 1/2 down, 9 forward. That's good.

04 06 44 40 LMP (EAGLE)
120 feet.

(GOSS NET 1) Tape 66/11 Page 316

04 06 44 45 LMP (EAGLE)
100 feet, 3 1/2 down, 9 forward. Five percent.

04 06 44 51 LMP (EAGLE)
...

04 06 44 54 LMP (EAGLE)
Okay. 75 feet. There's looking good. Down a half, 6 forward.

04 06 45 02 CC
60 seconds.

04 06 45 04 LMP (EAGLE)
Lights on. ...

04 06 45 08 LMP (EAGLE)
Down 2 1/2. Forward. Forward. Good.

04 06 45 17 LMP (EAGLE)
40 feet, down 2 1/2. Kicking up some dust.

04 06 45 21 LMP (EAGLE)
30 feet, 2 1/2 down. Faint shadow.

04 06 45 25 LMP (EAGLE)
4 forward. 4 forward. Drifting to the right a little. Okay. Down a half.

04 06 45 31 CC
30 seconds.

04 06 45 32 CDR (EAGLE)
Forward drift?

04 06 45 33 LMP (EAGLE)
Yes.

04 06 45 34 LMP (EAGLE)
Okay.

04 06 45 40 LMP (EAGLE)
CONTACT LIGHT.

posted 07-05-2020 03:29 AM               

I imagine it would have been less important in the Apollo context with constituted crews and where the CDRs,LMPs and the MOCR controllers would have had countless simulator sessions to thrash out language preferences.

I'd guess it might will have been an issue that came into play with the Apollo 13 Mattingly/Swigert switch and was probably at least one of the factors requiring the last minute sim work that I understand took place.

posted 07-23-2020 01:32 AM            

I expect you're correct. In aviation, we speak of a "positive rate of climb", but almost no-one says "a negative rate of climb" because it's too easy to hear the word 'climb' and miss the 'negative' with severe consequences.

However, in space, most of the time is spent in an environment where 'climb' has no meaning. Instead, velocities are based on various frames of reference, and (usually) the three axial coordinates.

So in landing, it would be most correct to say "Z minus 4" rather than "descending at 4". But that is likely to increase the mental load of a pilot used to landing aircraft, where the rate of movement in the Z axis is known as the rate of descent.