Flight modes (Stabilize, AltHold, Loiter, Auto) in Drone Programming - Step-by-Step Execution

Concept Flow - Flight modes (Stabilize, AltHold, Loiter, Auto)

Start: Pilot selects mode

↓

Check mode type

↓

Stabilize

↓

Manual control

↓

Adjust controls

↓

Feedback loop to pilot or system

↓

End or mode switch

The drone checks which flight mode is selected and runs the corresponding control logic: manual control in Stabilize, altitude hold in AltHold, position hold in Loiter, or autonomous mission in Auto.

Execution Sample

Drone Programming

mode = 'AltHold'
if mode == 'Stabilize':
    control_manual()
elif mode == 'AltHold':
    hold_altitude()
elif mode == 'Loiter':
    hold_position()
else:
    execute_mission()

This code chooses the drone's flight mode and runs the matching control function.

Execution Table

Step	Variable 'mode'	Condition Checked	Branch Taken	Action
1	'AltHold'	mode == 'Stabilize'?	No	Skip control_manual()
2	'AltHold'	mode == 'AltHold'?	Yes	Run hold_altitude()
3	'AltHold'	N/A	N/A	Altitude hold active
4	'AltHold'	End of checks	N/A	Wait for next input or mode change

💡 Mode 'AltHold' matched, hold_altitude() runs, no further checks needed.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 4
mode	None	'AltHold'	'AltHold'	'AltHold'
action	None	None	hold_altitude()	hold_altitude()

Key Moments - 2 Insights

Why does the code skip control_manual() when mode is 'AltHold'?

Because the first condition (mode == 'Stabilize') is false, the code moves to the next condition (mode == 'AltHold') and only runs hold_altitude() as shown in execution_table step 1 and 2.

What happens if the mode is not one of the listed ones?

The else branch runs execute_mission(), meaning the drone follows a predefined mission automatically, as implied in the code and concept flow.

Visual Quiz - 3 Questions

Look at the execution_table at step 2, what action is taken when mode is 'AltHold'?

A Run control_manual()

B Run hold_altitude()

C Run hold_position()

D Run execute_mission()

💡 Hint

Check the 'Action' column at step 2 in execution_table.

At which step does the code confirm the mode is not 'Stabilize'?

A Step 1

B Step 2

C Step 3

D Step 4

💡 Hint

Look at the 'Condition Checked' and 'Branch Taken' columns in execution_table step 1.

If mode was 'Loiter', which function would run according to the code?

A control_manual()

B hold_altitude()

C hold_position()

D execute_mission()

💡 Hint

Refer to the elif conditions in the execution_sample code.

Concept Snapshot

Flight modes control drone behavior:
- Stabilize: pilot manual control
- AltHold: maintain altitude
- Loiter: hold GPS position
- Auto: follow mission waypoints
Use if-elif-else to select mode and run matching control function.

Full Transcript

This visual execution shows how a drone program selects flight modes. The mode variable is checked step-by-step. If mode is 'Stabilize', manual control runs. If 'AltHold', altitude hold runs. If 'Loiter', position hold runs. Otherwise, the drone runs an automatic mission. The execution table traces these checks and actions. Variables mode and action change accordingly. Key moments clarify why some branches are skipped and what happens for unknown modes. The quiz tests understanding of mode selection and actions. This helps beginners see how flight modes control drone behavior in code.

Practice

1. Which flight mode allows the pilot to manually control the drone's attitude and throttle without automatic stabilization?

easy

A. Auto mode

B. Stabilize mode

C. Loiter mode

D. AltHold mode

Solution

1. Step 1: Understand Stabilize mode function

   Stabilize mode lets the pilot control the drone manually, with basic stabilization but no automatic altitude hold.

2. Step 2: Compare with other modes

   AltHold holds altitude automatically, Loiter holds position, and Auto runs pre-programmed missions.

3. Final Answer:

   Stabilize mode -> Option B

4. Quick Check:

   Manual control = Stabilize mode [OK]

Hint: Manual flying without altitude hold is Stabilize mode [OK]

Common Mistakes:

• Confusing AltHold with Stabilize
• Thinking Loiter allows manual control
• Assuming Auto mode is manual

2. Which of the following is the correct way to set the drone to AltHold mode in code?

easy

A. set_mode('Loiter')

B. set_mode('Auto')

C. set_mode('AltHold')

D. set_mode('Stabilize')

Solution

1. Step 1: Identify the function to set mode

   The function set_mode() is used to change the drone's flight mode by passing the mode name as a string.

2. Step 2: Match the mode name for altitude hold

   To hold altitude automatically, the mode name must be 'AltHold'.

3. Final Answer:

   set_mode('AltHold') -> Option C

4. Quick Check:

   Altitude hold mode = 'AltHold' string [OK]

Hint: Use exact mode name string 'AltHold' in set_mode() [OK]

Common Mistakes:

• Using wrong mode string like 'Auto' or 'Loiter'
• Misspelling mode names
• Passing mode as variable instead of string

3. What will be the output of this code snippet?

mode = 'Loiter'
if mode == 'Stabilize':
    print('Manual control active')
elif mode == 'AltHold':
    print('Altitude hold active')
elif mode == 'Loiter':
    print('Position hold active')
else:
    print('Automatic mission active')

medium

A. Position hold active

B. Altitude hold active

C. Manual control active

D. Automatic mission active

Solution

1. Step 1: Check the value of mode variable

   The variable mode is set to 'Loiter'.

2. Step 2: Follow the if-elif conditions

   The code checks if mode equals 'Stabilize' or 'AltHold' first, which it does not. Then it checks if mode equals 'Loiter', which is true, so it prints 'Position hold active'.

3. Final Answer:

   Position hold active -> Option A

4. Quick Check:

   mode == 'Loiter' prints 'Position hold active' [OK]

Hint: Match variable value with if-elif conditions carefully [OK]

Common Mistakes:

• Choosing first if condition without checking value
• Confusing Loiter with Auto mode output
• Ignoring else block

4. Identify the error in this code snippet that tries to switch to Auto mode:

def switch_mode(mode):
    if mode = 'Auto':
        print('Auto mode activated')
    else:
        print('Other mode')

medium

A. SyntaxError: '=' used instead of '==' in if condition

B. RuntimeError: mode variable undefined

C. Logical error: should use '!=' instead of '='

D. No error, code runs fine

Solution

1. Step 1: Check the if condition syntax

   The condition uses a single '=' which is assignment, not comparison. This causes a syntax error in Python.

2. Step 2: Correct the condition to use '==' for comparison

   Changing '=' to '==' fixes the syntax and allows proper comparison.

3. Final Answer:

   SyntaxError: '=' used instead of '==' in if condition -> Option A

4. Quick Check:

   Use '==' for comparisons, '=' is assignment [OK]

Hint: Use '==' in if conditions, '=' is for assignment [OK]

Common Mistakes:

• Using '=' instead of '==' in conditions
• Confusing assignment with comparison
• Ignoring syntax errors

5. You want the drone to automatically fly a mission but keep altitude stable if GPS signal is lost. Which mode combination should your program switch between?

hard

A. Stabilize mode for mission, switch to Auto if GPS lost

B. Loiter mode for mission, switch to Stabilize if GPS lost

C. AltHold mode for mission, switch to Loiter if GPS lost

D. Auto mode for mission, switch to AltHold if GPS lost

Solution

1. Step 1: Understand mission and GPS loss handling

   Auto mode runs the mission automatically. If GPS is lost, the drone cannot continue Auto mode safely.

2. Step 2: Choose AltHold to maintain altitude during GPS loss

   AltHold keeps altitude stable without GPS, preventing sudden drops.

3. Final Answer:

   Auto mode for mission, switch to AltHold if GPS lost -> Option D

4. Quick Check:

   Auto + AltHold for GPS loss safety [OK]

Hint: Auto for mission, AltHold to keep altitude if GPS fails [OK]

Common Mistakes:

• Using Stabilize during GPS loss risking altitude drop
• Confusing Loiter with mission mode
• Not switching modes on GPS loss