HASELL

HASELL is an acronym used in safety-critical software development, particularly within the avionics and railway industries. It stands for:

• Height: Check the aircraft's (or other vehicle's) altitude or height above ground level. Verify it is within safe operating parameters for the planned actions.
• Altitude: Similar to Height, but emphasizing the absolute altitude above sea level. Ensure sufficient clearance from terrain and other obstacles.
• Speed: Confirm the vehicle's airspeed or ground speed is appropriate for the intended maneuver. Avoid exceeding limits that could compromise safety or stability.
• Engine/Environment: Assess the engine performance parameters (e.g., RPM, temperature, pressure) and environmental conditions (e.g., wind, visibility, temperature). Verify they are within acceptable ranges and won't adversely affect the intended operation.
• Location: Verify the vehicle's position is as expected and that it is not approaching any restricted areas or hazards. Ensure correct course and heading are maintained.
• Loos Items: (Sometimes referred to as "Lookout" or "Landing") A final check to ensure there are no loose items that could interfere with the vehicle's operation, or, in the context of landing, that the landing area is clear of obstacles and appropriate for landing. The specific meaning of the final "L" can vary depending on the context and organization employing the HASELL checklist.

The HASELL check is a structured, pre-flight or pre-maneuver checklist designed to ensure that all critical factors are considered before initiating a potentially hazardous activity. It promotes a proactive and methodical approach to risk management, helping to mitigate potential errors and enhance overall safety. The checklist is often verbalized aloud and/or visually confirmed using instrumentation before continuing. The specific parameters checked under each element of HASELL can be customized to the specific vehicle, operating environment, and type of activity being performed.