SIFT Aviation Knowledge 2 — Questions and Answers
Question 1: What is the standard altimeter setting in the United States when flying above 18,000 feet MSL?
- 29.92 inches Hg (Correct answer)
- The current local barometric pressure
- The departure airport altimeter setting
- The destination airport altimeter setting
Correct answer: 29.92 inches Hg
Above 18,000 feet MSL (in Class A airspace), all aircraft set their altimeters to 29.92 inches Hg standard pressure, and altitudes are referred to as 'flight levels.'
Below 18,000 feet, pilots set their altimeters to the local altimeter setting (provided by ATC or ATIS) to read accurate altitudes above sea level. Above 18,000 feet in Class A airspace, all aircraft use 29.92 inHg so aircraft at the same 'flight level' are using the same reference, preventing altitude discrepancies.
Question 2: What does 'VFR' stand for and what does it require?
- Variable Flight Rules — used in mountainous terrain
- Visual Flight Rules — flying by outside visual reference in good weather (Correct answer)
- Verified Flight Records — the logging of all flight hours
- Vectored Flight Routing — following ATC assigned headings
Correct answer: Visual Flight Rules — flying by outside visual reference in good weather
VFR stands for Visual Flight Rules, which require pilots to navigate by visual reference to the ground and maintain specific minimum visibility and cloud clearance requirements.
VFR flight requires pilots to maintain visual contact with the surface and keep sufficient distance from clouds. Minimum requirements vary by airspace class but generally require 3 statute miles visibility and specific cloud clearances. VFR pilots are responsible for see-and-avoid collision avoidance.
Question 3: What is a 'NOTAM' in aviation?
- Notice to Airmen — temporary notices about flight hazards, restrictions, or changes (Correct answer)
- Night Operations Technical Aviation Manual
- Navigation Of Traffic And Maneuvering guidance
- Non-standard Operations Training and Airspace Management
Correct answer: Notice to Airmen — temporary notices about flight hazards, restrictions, or changes
A NOTAM (Notice to Airmen) is an official notice containing information about changes to aeronautical facilities, services, procedures, or hazards that pilots must know.
NOTAMs contain time-critical aeronautical information that cannot be included in regular charts or publications. They cover temporary flight restrictions (TFRs), runway closures, unlit obstructions, NAVAID outages, airspace changes, and other items affecting flight safety. Checking NOTAMs is a required pre-flight task.
Question 4: What does 'MSL' mean in aviation altimetry?
- Maximum Speed Limit
- Mean Sea Level — the average ocean surface used as altitude reference (Correct answer)
- Minimum Safe Landing
- Military Standard Level
Correct answer: Mean Sea Level — the average ocean surface used as altitude reference
MSL stands for Mean Sea Level, the average ocean surface level used as the standard zero reference for measuring altitude in aviation.
Altitude in aviation is typically expressed as feet above Mean Sea Level. This provides a common reference that accounts for terrain elevation. AGL (Above Ground Level) is also used, especially for clearance from terrain. A mountain summit might be 14,000 feet MSL but only 1,000 feet AGL if the surrounding plateau is 13,000 feet.
Question 5: What is 'relative wind' in aerodynamics?
- Wind speed measured relative to true north
- The airflow experienced by the airfoil, opposite in direction to the aircraft's movement (Correct answer)
- The wind component directly perpendicular to the flight path
- Natural wind corrected for pressure altitude
Correct answer: The airflow experienced by the airfoil, opposite in direction to the aircraft's movement
Relative wind is the airflow direction and velocity as experienced by the airfoil, which flows in the opposite direction to the aircraft's path through the air.
Relative wind is always opposite and equal in speed to the aircraft's velocity through the air mass. It is the wind that 'acts on' the airfoil to create lift. Angle of attack is measured between the chord line of the airfoil and the relative wind. Understanding relative wind is fundamental to understanding lift, stall, and aerodynamic flight.
Question 6: What does 'the four forces of flight' refer to?
- Lift, weight, thrust, and drag (Correct answer)
- Power, torque, velocity, and altitude
- Roll, pitch, yaw, and surge
- Speed, altitude, heading, and attitude
Correct answer: Lift, weight, thrust, and drag
The four forces acting on an aircraft in flight are lift (upward), weight (downward), thrust (forward), and drag (rearward). Flight is controlled by managing the balance of these forces.
Lift is generated by the wings/rotor opposing weight (gravity). Thrust from the engine/rotor system propels the aircraft forward opposing drag (aerodynamic resistance). In straight-and-level flight at constant speed, all four forces are in equilibrium: lift = weight and thrust = drag.
SIFT Aviation Knowledge 2
What is the standard altimeter setting in the United States when flying above 18,000 feet MSL?