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Predicting Freezing Levels

The program FREEZE calculates the freezing elevation heights for two situations:

Dry: Freezing level in clear weather. The Aviation Pac (see source below) uses a drop rate of 2 °C/1000 ft in its calculation.

Wet: Freezing level in clouds on a relatively clear day. Accuracy tends to lessen for cloudy or rainy days. The Aviation Pac (see source below) uses a drop rate of 1.5 °C/1000 ft in its calculation.

In general, the freezing level is calculated as:

FL = ALT + T * drop rate

ALT = altitude of the observer
T = temperature

The program FREEZE allows the user to choose from a set of units: (Fahrenheit vs. Celsius, feet vs. meters).

1. °F, ft
2. °C, ft
3. °F, m
4. °C, m

HP 42S/DM42/Free42 Program FREEZE

Code:
```00 { 204-Byte Prgm } 01▸LBL "FREEZE" 02 "TEMP?" 03 PROMPT 04 CLMENU 05 "°F FT" 06 KEY 1 GTO 01 07 "°C FT" 08 KEY 2 GTO 02 09 "°F M" 10 KEY 3 GTO 03 11 "°C M" 12 KEY 4 GTO 04 13 MENU 14▸LBL 00 15 STOP 16 GTO 00 17▸LBL 01 18 32 19 - 20 1ᴇ3 21 × 22 ENTER 23 ENTER 24 3.6 25 ÷ 26 X<>Y 27 2.7 28 ÷ 29 GTO 05 30▸LBL 02 31 1ᴇ3 32 × 33 ENTER 34 ENTER 35 2 36 ÷ 37 X<>Y 38 1.5 39 ÷ 40 GTO 05 41▸LBL 03 42 32 43 - 44 1ᴇ3 45 × 46 ENTER 47 ENTER 48 1.09728 49 ÷ 50 X<>Y 51 0.82296 52 ÷ 53 GTO 05 54▸LBL 04 55 1ᴇ3 56 × 57 ENTER 58 ENTER 59 0.6096 60 ÷ 61 X<>Y 62 0.4572 63 ÷ 64 GTO 05 65▸LBL 05 66 "ALTITUDE?" 67 PROMPT 68 STO+ ST Z 69 STO+ ST Y 70 R↓ 71 CLMENU 72 EXITALL 73 "Y: DRY X:WET" 74 AVIEW 75 STOP 76 RTN 77 .END. Example: Temperature:  40 °F Altitude:  3970 ft  (choose °F, ft) Results: Dry:  6192.2222 ft Wet:  6932.9630 ft```

Turn Performance

The program TURN calculates four parameters when it comes to performance of an aircraft:

1. The G-force

2. The stall speed when bank angle is considered

3. The diameter of an airplane's 360° turn

4. The time it takes an airplane to turn 360°

The program sets the calculator to Degrees Mode. The units are in feet for distance and knots for speed.

Memory Registers Used:

Input:
R01 = bank angle, in degrees (prompted)
R02 = true airspeed, TAS, in knots (prompted)
R03 = stall speed, in knots (prompted)

Output:
R04 = G-Force
R05 = turn diameter in nautical miles
R06 = time for a 360° to be completed in minutes
R07 = stall speed when bank angle is considered, in knots

HP 42S/DM42/Free42 Program TURN

Code:
```00 { 157-Byte Prgm } 01▸LBL "TURN" 02 DEG 03 "SPEED IN KNOTS" 04 AVIEW 05 PSE 06 PSE 07 "TRUE AIR SPEED?" 08 PROMPT 09 STO 02 10 "NORM STALL?" 11 PROMPT 12 STO 03 13 "BANK? °" 14 PROMPT 15 STO 01 16 COS 17 1/X 18 STO 04 19 "G FORCE:" 20 ARCL ST X 21 AVIEW 22 STOP 23 SQRT 24 RCL× 03 25 STO 07 26 "STALL: " 27 ARCL ST X 28 AVIEW 29 STOP 30 RCL 01 31 TAN 32 1/X 33 RCL× 02 34 ENTER 35 ENTER 36 RCL× 02 37 34028 38 ÷ 39 STO 05 40 "DIA: " 41 ARCL ST X 42 ├" N.M." 43 AVIEW 44 STOP 45 X<>Y 46 55ᴇ-4 47 × 48 STO 06 49 CLA 50 ARCL ST X 51 ├" MIN" 52 AVIEW 53 .END.```
Example:

Input:
True Air Speed (cruising speed): 107 knots
Stall speed: 54 knots
Bank: 30°

Output:
G Force: 1.1547
Stall: 58.0268 knots
Diameter: 0.5828 nautical miles
Time: 1.0193 minutes (about 1 minute, 1.1 seconds)