Skylark Drones GNC Engineer Interview: Rounds, Questions and Preparation

What the job involves

A GNC (Guidance, Navigation and Control) engineer develops algorithms that let drones and aerospace vehicles estimate their state, plan safe paths, and follow them accurately. Day to day work includes sensor fusion (IMU, GPS, barometer, magnetometer), control loop tuning, simulation in MATLAB/Simulink or Python, and flight-test data analysis. In fast-growing space and defence tech teams, you often support integration, field trials, and quick fixes for autonomous or semi-autonomous platforms.

Role and technical knowledge

1. 1

   Explain the difference between guidance, navigation, and control in a drone autopilot.

   Define navigation as state estimation, guidance as path or trajectory generation, and control as actuator commands to track it. Give a simple example like waypoint following.

2. 2

   How does a Kalman filter work, and why is it used in drone state estimation?

   Cover predict and update steps, handling noisy sensors, and fusing IMU with GPS or barometer. Mention process and measurement noise covariance in simple terms.

3. 3

   What are Euler angles and quaternions, and why do we often prefer quaternions for attitude control?

   Explain gimbal lock in Euler angles and quaternions avoiding singularities. Mention normalization and interpolation benefits.

4. 4

   Describe a basic PID controller. How would you tune it for a drone altitude hold?

   Explain P, I, D roles, then describe starting with P, adding D for damping, and I for steady-state error. Mention step response and avoiding oscillations.

Practical scenarios and problem solving

1. 5

   During a flight test, the drone oscillates in roll. How would you diagnose and fix it?

   Check control gains, sensor noise, mechanical play, and filter delays. Suggest reducing gain, adding a notch filter, or checking IMU mounting.

2. 6

   Your GPS drops out in a defence mission area. What does the GNC system do to stay safe?

   Discuss switching to inertial or visual odometry, failsafe modes like loiter or return-to-launch, and health monitoring. Mention graceful degradation.

3. 7

   How would you validate a new guidance law before flying it on a real drone?

   Cover model-in-the-loop and software-in-the-loop simulation, hardware-in-the-loop with autopilot, then tethered or restricted test flights. Mention Monte Carlo runs.

4. 8

   You need to log and analyse flight data to find why a waypoint was missed. What steps do you take?

   List relevant logs (attitude, position, actuator commands), time-sync them, plot tracking error, and check for saturation or delays. Suggest a root cause and fix.

Behavioural and teamwork

1. 9

   Tell me about a project where you had to learn a new tool or concept quickly.

   Use STAR format. Focus on how you learned, applied it, and what result you achieved. Show initiative and self-learning.

2. 10

   Describe a time you worked in a team under a tight deadline.

   Highlight your specific contribution, communication, and how you handled pressure. Mention any trade-offs made.

3. 11

   Have you ever had a test or experiment fail? What did you do?

   Show ownership, systematic debugging, and what you changed afterward. Emphasise learning over blame.

4. 12

   Why do you want to work in space and defence tech, and how do you handle strict safety or secrecy requirements?

   Connect personal interest to mission impact. Show awareness of compliance, documentation, and responsible engineering.

HR and fresher-specific

1. 13

   Walk us through your final year project or internship and its relevance to GNC.

   Summarise the problem, your approach, tools used, and results. Link it to estimation, control, or simulation if possible.

2. 14

   What do you know about our company and the kind of drone or defence solutions we build?

   Show you researched their products, customers, and technology stack. Relate your skills to their mission.

3. 15

   Are you comfortable with field trials, travel, and working on hardware, not just code?

   Be honest and positive. Mention any hands-on experience with drones, robotics, or lab hardware.

4. 16

   Where do you see yourself in three years in a GNC role?

   Show a growth path from implementing and testing to owning subsystems or leading small projects. Align with company needs.