(42S) Rate of Climb and Descent, Head and Cross Winds
01-11-2020, 03:35 PM
Post: #1
 Eddie W. Shore Senior Member Posts: 1,237 Joined: Dec 2013
(42S) Rate of Climb and Descent, Head and Cross Winds
Rate of Climb and Descent

The solver CLIMB creates a solver of the equation:

ROC = TAS * ALT / √(DIST^2 + ALT^2)

ROC: rate of climb, usually in ft/min
TAS: true airspeed of the airplane, usually in knots
ALT: (vertical distance) the change in elevation, take into the account the height of your airplane, the height of the mountain or obstacle to be cleared plus desired clearance height, usually in feet
DIST: (horizontal distance) distance to the mountain or obstacle to be cleared

For the solver to accurate, you must keep the units consistent (feet or nautical miles for distance, ft/min or knots for speed and rate of climb)

Conversion factors:

1 knot = 101.269 ft/min

1 nautical mile = 6076.12 ft

HP 42S/DM42/Free42 Solver program CLIMB
﻿
Code:
 00 { 61-Byte Prgm } 01▸LBL "CLIMB" 02 MVAR "TAS" 03 MVAR "ALT" 04 MVAR "DIST" 05 MVAR "ROC" 06 RCL "TAS" 07 RCL× "ALT" 08 RCL "DIST" 09 X↑2 10 RCL "ALT" 11 X↑2 12 + 13 SQRT 14 ÷ 15 RCL- "ROC" 16 .END.

Example:
TAS = 90 knots = 9114.21 ft/min
ALT = 5000 ft
DIST = 16 nautical miles = 97217.92 ft

Solve for ROC: 468.1328 ft/min

The program WINDS calculates the head wind and cross wind (right is positive, left is negative) given the following inputs:

D: reported wind direction
V: compass magnetic variation, if any

The directions are entered in degrees, measured from true north, clockwise

K: reported wind velocity

HW = K cos(D - HDG - V)

Cross wind:
CW = K sin(D - HDG - V)

We can use the polar to rectangular conversion function with the following convention:

θ = D - HDG - V
r = K

HP 42S/DM42/Free42 Program WINDS
Code:
 00 { 79-Byte Prgm } 01▸LBL "WINDS" 02 DEG 03 "WIND DIR?" 04 PROMPT 05 "HEADING?" 06 PROMPT 07 - 08 "COMP VAR?" 09 PROMPT 10 - 11 "WIND VELOCITY?" 12 PROMPT 13 →REC 14 "Y:CROSS X:HEAD" 15 AVIEW 16 STOP 17 RTN 18 .END.

Example:
Wind Direction: 30°
Wind Velocity: 20 knots

Results:
Y: cross winds: 12.8558 knots (from the right)