Failsafe actions (RTL, Land, SmartRTL) in Drone Programming - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this failsafe action code?

Consider this drone failsafe code snippet. What will the drone do if the battery level drops below 10%?

Drone Programming

battery_level = 9
failsafe_action = 'RTL' if battery_level < 10 else 'Land'
print(failsafe_action)

A RTL

B Land

C SmartRTL

D No action

💡 Hint

Check the condition for battery level and the assigned action.

The code checks if battery_level is less than 10. Since 9 is less than 10, it sets failsafe_action to 'RTL' and prints it.

🧠 Conceptual

intermediate

Which failsafe action is best when GPS signal is lost but the drone is over a safe landing zone?

Choose the most appropriate failsafe action for a drone that loses GPS signal but is currently flying over a safe landing zone.

A Return to Launch (RTL)

B Hover in place

C SmartRTL

D Land immediately

💡 Hint

Think about safety and location when GPS is lost.

Landing immediately is safest when GPS is lost over a safe zone, as RTL or SmartRTL require GPS to navigate back.

🔧 Debug

advanced

What error does this failsafe code raise?

Analyze the following code snippet and identify the error it will cause when executed.

Drone Programming

def failsafe_action(signal_lost):
    if signal_lost == True:
        return 'SmartRTL'
    else:
        return 'Land'

print(failsafe_action(True))

A SyntaxError

B TypeError

C NameError

D No error, prints 'SmartRTL'

💡 Hint

Look carefully at the if statement syntax.

The code uses '=' instead of '==' in the if condition, causing a SyntaxError.

❓ Predict Output

advanced

What is the output of this SmartRTL decision code?

Given the drone's altitude and GPS status, what will the failsafe function return?

Drone Programming

def decide_failsafe(gps_signal, altitude):
    if not gps_signal and altitude > 20:
        return 'Land'
    elif gps_signal and altitude > 20:
        return 'SmartRTL'
    else:
        return 'RTL'

print(decide_failsafe(True, 25))

A Land

B No output

C SmartRTL

D RTL

💡 Hint

Check the conditions in order and the values passed.

GPS is True and altitude is 25 (>20), so the function returns 'SmartRTL'.

🚀 Application

expert

How many failsafe actions are triggered in this sequence?

Given this sequence of drone events, how many times will the failsafe action be triggered?

events = [
  {'battery': 15, 'gps': True},
  {'battery': 9, 'gps': True},
  {'battery': 8, 'gps': False},
  {'battery': 5, 'gps': False},
  {'battery': 12, 'gps': True}
]

failsafe_count = 0
for event in events:
    if event['battery'] < 10 or not event['gps']:
        failsafe_count += 1
print(failsafe_count)

A 3

B 4

C 2

D 5

💡 Hint

Count events where battery is below 10 or GPS is lost.

Events 2, 3, and 4 trigger failsafe (battery < 10 or gps False), so count is 3.

Practice

1. What does the RTL failsafe action do when triggered on a drone?

easy

A. The drone returns to its takeoff point automatically.

B. The drone immediately lands at its current location.

C. The drone hovers in place until manual control is regained.

D. The drone performs a pre-programmed flight path before landing.

Solution

1. Step 1: Understand RTL meaning

   RTL stands for "Return To Launch," meaning the drone flies back to where it took off.

2. Step 2: Compare with other failsafe actions

   Unlike Land or SmartRTL, RTL specifically returns the drone to the takeoff point automatically.

3. Final Answer:

   The drone returns to its takeoff point automatically. -> Option A

4. Quick Check:

   RTL = Return To Launch [OK]

Hint: RTL always means return to the starting point [OK]

Common Mistakes:

• Confusing RTL with immediate landing
• Thinking RTL means hovering
• Assuming RTL follows a custom path

2. Which of the following is the correct syntax to set the failsafe action to Land in a drone programming script?

easy

A. set_failsafeAction('Land')

B. setFailsafeAction(Land)

C. setFailsafeAction("Land")

D. setFailsafeAction('land')

Solution

1. Step 1: Identify string syntax in code

   Failsafe actions are usually passed as strings, so quotes are needed around the word Land.

2. Step 2: Check correct string format

   Double quotes or single quotes can be used, but the option with double quotes and correct capitalization is standard.

3. Final Answer:

   setFailsafeAction("Land") -> Option C

4. Quick Check:

   String with quotes and correct case = setFailsafeAction("Land") [OK]

Hint: Use quotes and correct capitalization for string parameters [OK]

Common Mistakes:

• Omitting quotes around the string
• Using wrong capitalization
• Passing the action as a variable without quotes

3. Given the following code snippet, what will be the drone's behavior if the failsafe is triggered?

failsafe = 'SmartRTL'
if failsafe == 'RTL':
    action = 'Return to launch point'
elif failsafe == 'Land':
    action = 'Land immediately'
elif failsafe == 'SmartRTL':
    action = 'Return home avoiding obstacles'
else:
    action = 'Hover in place'
print(action)

medium

A. Return home avoiding obstacles

B. Land immediately

C. Return to launch point

D. Hover in place

Solution

1. Step 1: Check the value of failsafe variable

   The variable failsafe is set to 'SmartRTL'.

2. Step 2: Follow the if-elif conditions

   The code matches the 'SmartRTL' condition and sets action to 'Return home avoiding obstacles'.

3. Final Answer:

   Return home avoiding obstacles -> Option A

4. Quick Check:

   SmartRTL triggers obstacle-avoiding return [OK]

Hint: Match variable value to condition branches carefully [OK]

Common Mistakes:

• Choosing the default else action
• Confusing SmartRTL with simple RTL
• Ignoring case sensitivity in strings

4. Identify the error in this failsafe action code snippet:

def set_failsafe(action):
    if action = 'RTL':
        return 'Returning home'
    elif action == 'Land':
        return 'Landing now'
    else:
        return 'Hovering'

medium

A. Missing colon after the else statement

B. Using single equals (=) instead of double equals (==) in the if condition

C. Incorrect indentation of the return statements

D. Using single quotes instead of double quotes for strings

Solution

1. Step 1: Check the if condition syntax

   The if condition uses a single equals sign (=), which is assignment, not comparison.

2. Step 2: Confirm correct comparison operator

   Comparison requires double equals (==) to check equality.

3. Final Answer:

   Using single equals (=) instead of double equals (==) in the if condition -> Option B

4. Quick Check:

   Comparison needs '==' not '=' [OK]

Hint: Use '==' for comparison, '=' is assignment [OK]

Common Mistakes:

• Confusing assignment and comparison operators
• Ignoring syntax errors from missing colons
• Assuming quotes style causes errors

5. Given the following code snippet, what failsafe action will be selected?

battery = 15  # percentage
gps_signal = False

if battery < 20 and gps_signal:
    failsafe = 'SmartRTL'
elif battery < 20 and not gps_signal:
    failsafe = 'Land'
else:
    failsafe = 'RTL'

print(failsafe)

hard

A. The drone will choose 'RTL' because battery is sufficient.

B. The drone will choose 'SmartRTL' because battery is low and GPS signal is present.

C. The drone will choose 'Land' because GPS signal is present.

D. The drone will choose 'Land' because battery is low and GPS signal is missing.

Solution

1. Step 1: Analyze battery and GPS conditions

   Battery is 15% (less than 20) and GPS signal is False (missing).

2. Step 2: Follow the if-elif-else logic

   Since battery < 20 and gps_signal is False, the elif condition matches and sets failsafe to 'Land'.

3. Final Answer:

   The drone will choose 'Land' because battery is low and GPS signal is missing. -> Option D

4. Quick Check:

   Low battery + no GPS = Land [OK]

Hint: Check conditions in order: battery then GPS [OK]

Common Mistakes:

• Assuming SmartRTL without GPS signal
• Ignoring battery level in decision
• Mixing up elif and else conditions