### FILE="Main.annotation"
## Copyright:	Public domain.
## Filename:	GIMBAL_LOCK_AVOIDANCE.agc
## Purpose:	A section of Luminary 1C, revision 131.
##		It is part of the source code for the Lunar Module's (LM)
##		Apollo Guidance Computer (AGC) for Apollo 13.
##		This file is intended to be a faithful transcription, except
##		that the code format has been changed to conform to the
##		requirements of the yaYUL assembler rather than the 
##		original YUL assembler.
## Reference:	p. 366
## Contact:	Ron Burkey <info@sandroid.org>.
## Website:	www.ibiblio.org/apollo/index.html
## Mod history:	05/11/03 RSB.	Began transcribing.
##		05/14/05 RSB	Corrected website reference above.
##		2017-01-06 RSB	Page numbers now agree with those on the
##				original harcopy, as opposed to the PDF page
##				numbers in 1701.pdf.
##		2017-02-23 RSB	Proofed comment text using octopus/ProoferComments.
##		2017-08-22 RSB	Fixed comment-text typo identified in ZERLINA 56.

## Page 366
		BANK	15
		
		SETLOC	KALCMON1
		BANK
		
# DETECTING GIMBAL LOCK
LOCSKIRT	EQUALS	NOGIMLOC

NOGIMLOC	SET
			CALCMAN3
WCALC		LXC,1	DLOAD*
			RATEINDX	# CHOOSE THE DESIRED MANEUVER RATE
			ARATE,1		# FROM A LIST OF FOUR
		SR4	CALL		# COMPUTE THE INCREMENTAL ROTATION MATRIX
			DELCOMP		# DEL CORRESPONDING TO A 1 SEC ROTATION
					# ABOUT COF
		DLOAD*	VXSC
			ARATE,1
			COF
		STODL	BRATE		# COMPONENT MANEUVER RATES 45 DEG/SEC
			AM
		DMP	DDV*
			ANGLTIME
			ARATE,1
		SR
			5
		STORE	TM		# MANEUVER EXECUTION TIME SCALED AS T2
		SETGO	
			CALCMAN2	# 0(OFF) = CONTINUE MANEUVER
			NEWANGL +1	# 1(ON) = START MANEUVER
			
# THE FOUR SELECTABLE FREE FALL MANEUVER RATES SELECTED BY
# LOADING RATEINDX WITH 0, 2, 4, 6, RESPECTIVELY

ARATE		2DEC	.0088888888	# = 0.2 DEG/SEC			$ 22.5 DEG/SEC
		2DEC	.0222222222	# = 0.5 DEG/SEC			$ 22.5 DEG/SEC
		2DEC	.0888888888	# = 2.0 DEG/SEC			$ 22.5 DEG/SEC
		2DEC	.4444444444	# = 10.0 DEG/SEC		$ 22.5 DEG/SEC
		
ANGLTIME	2DEC	.0001907349	# = 100B-19 FUDGE FACTOR TO CONVERT
					# MANEUVER ANGLE TO MANEUVER TIME