CPC Aircraft Performance & Systems Knowledge for Controllers 1 — Questions and Answers
Question 1: What is wake turbulence, and from which part of the aircraft does it originate?
- Engine exhaust turbulence from the rear of jet engines
- Wingtip vortices generated by lift production that trail behind and below an aircraft (Correct answer)
- Turbulent airflow from landing gear during approach
- Prop wash from propeller-driven aircraft only
Correct answer: Wingtip vortices generated by lift production that trail behind and below an aircraft
Wake turbulence consists of counter-rotating wingtip vortices that form whenever an aircraft generates lift; they sink and trail behind and below the generating aircraft.
Question 2: According to FAA wake turbulence categories, which aircraft type generates the most severe wake?
- Heavy jets above 255,000 lbs
- Super category aircraft like the A380 and AN-124 (Correct answer)
- Any aircraft with wing-mounted engines
- Aircraft with high wing loading regardless of size
Correct answer: Super category aircraft like the A380 and AN-124
The 'Super' category (A380, AN-124) generates the most severe wake turbulence, requiring the greatest separation from following aircraft.
Question 3: What is the standard IFR departure separation behind a Heavy jet for a Small aircraft departing the same runway?
- 2 minutes or 3 nautical miles radar (Correct answer)
- 3 minutes or 5 nautical miles radar
- 2 minutes only, no radar option
- 1 minute with radar monitoring
Correct answer: 2 minutes or 3 nautical miles radar
A small aircraft departing behind a Heavy must wait 2 minutes (or maintain 3 NM if radar is used) to avoid wake turbulence encounter.
Question 4: What does 'MACH tuck' or 'Mach tuck' refer to, and why is it relevant to high-altitude ATC?
- A pitch-down tendency as an aircraft approaches critical Mach number due to shifting center of lift (Correct answer)
- A fuel-saving technique used at cruise altitude
- An engine compressor stall at high Mach speeds
- A navigation correction maneuver near the Mach limit
Correct answer: A pitch-down tendency as an aircraft approaches critical Mach number due to shifting center of lift
Mach tuck occurs when an aircraft nears its critical Mach number and the center of pressure shifts aft, creating a nose-down pitching tendency that can be difficult to recover from.
Question 5: What is 'coffin corner' and which aircraft type is most susceptible?
- A narrow speed range at high altitude between stall speed and MMO where there is little margin; affects high-altitude jets (Correct answer)
- An area of airspace near mountains with no escape route
- The low-speed, high-drag regime during approach; affects all aircraft
- A difficult visual approach segment; affects large aircraft
Correct answer: A narrow speed range at high altitude between stall speed and MMO where there is little margin; affects high-altitude jets
Coffin corner is the narrow altitude band where an aircraft's stall speed and MMO (maximum operating Mach) converge, leaving almost no safe airspeed range; it primarily affects high-flying jets.
Question 6: When a jet aircraft experiences a 'compressor stall,' what should the controller expect?
- Immediate and rapid altitude loss requiring emergency descent clearance
- Loud banging, possible loss of thrust, and the crew may request priority handling (Correct answer)
- Silent failure with no impact on aircraft performance
- Automatic restart within 30 seconds with no crew action required
Correct answer: Loud banging, possible loss of thrust, and the crew may request priority handling
A compressor stall causes an audible bang and possible thrust loss; flight crews may declare an emergency or request priority, requiring ATC to provide immediate assistance.
CPC Aircraft Performance & Systems Knowledge for Controllers 1
What is wake turbulence, and from which part of the aircraft does it originate?