Stalling — Page 195, Lesson 239

Let’s pick this up right where the material gets practical. This is the "Key Facts 2" self-study block for stalling, and it’s a checklist of the exact factors that shape stall behaviour. I’ll walk you through each blank so you know precisely what belongs there and why. First statement: "The swept-back wing is the major contributory factor to _ stall." The missing word is tip. A swept-back wing tends to stall at the tip first, because the airflow over the outboard section behaves differently — that’s the major contributory factor to a tip stall. That matters because a tip stall can affect aileron effectiveness, so it’s a handling concern. Next: "An aircraft design with super stall tendencies must be fitted with a stick ." The word is pusher. A stick pusher is a device that physically pushes the control column forward to reduce the angle of attack automatically, preventing the aircraft from entering a super stall — that’s the deep, unrecoverable stall condition. Now the list of factors that can affect VSR — that’s the reference stall speed, the speed at which the aircraft stalls in a specified configuration. The first factor is "Changes in _." That’s weight. The second: "Manoeuvring the aircraft (increasing the _ )." That’s load factor — when you pull g in a manoeuvre, the load factor increases. Third: "Configuration changes (changes in _ and _ moment)." That’s power and pitching moment — so changes in power setting and changes in the pitching moment, which is the nose-up or nose-down tendency. Fourth: "Engine _ and propeller ." That’s power and slipstream — engine power and the slipstream from the propeller. Fifth: "_ number." That’s Mach number — the ratio of true airspeed to the speed of sound. Sixth: "Wing _." That’s contamination — things like ice, frost, or dirt on the wing surface. Seventh: "Heavy ." That’s rain — heavy rain on the wing. Then: "In straight and level flight the load factor is _." The answer is one — in straight and level, unaccelerated flight, the load factor is 1g. "At a higher weight, the stall speed of an aircraft will be _." That’s higher — more weight means you need more lift, so you stall at a higher speed. "If the weight is decreased by 50%, the stall speed will _ by approximately %." The stall speed will decrease by approximately 29%. That comes from the square-root relationship — stall speed is proportional to the square root of weight, so halving weight reduces stall speed by the square root of 0.5, which is about 0.707, meaning a 29% reduction. "Load factor varies with ." That’s bank angle — in a turn, the load factor increases with the bank angle. "The increase in stall speed in a turn is proportional to the square root of the _." That’s load factor — so in a 60-degree bank, load factor is 2, and stall speed increases by the square root of 2, about 41%. "High lift devices will the stall speed because CLMAX is ." High lift devices will decrease the stall speed because CLMAX — the maximum lift coefficient — is increased. Flaps and slats raise the maximum lift the wing can produce, so you can fly slower before stalling. "Forward CG movement will stall speed due to the increased tail load." Forward CG movement will increase stall speed due to the increased tail down load. Moving the centre of gravity forward means the tail has to produce more download to balance, which adds to the total lift required, so the stall speed goes up. "Lowering the landing gear will increase stall speed due to the increased tail load." That’s down load again — lowering the gear changes the pitching moment, requiring more tail download, which increases stall speed. "Increased engine power will decrease stall speed due to propeller _ and/or the inclination of thrust." That’s propeller slipstream and the upward inclination of thrust. The slipstream energises the airflow over the wing, and an upward thrust component reduces the lift the wing must produce, so stall speed decreases. "The effect of increasing Mach number on stall speed begin at M ." That’s 0.3 — the compressibility effects on stall speed begin at about Mach 0.3. "The effects of compressibility increases stall speed by decreasing _." That’s CLMAX — compressibility reduces the maximum lift coefficient, so the stall speed increases. Now the next block, about accidental stall and recovery in a single-engine propeller aircraft. "An added complication during an accidental stall and recovery of a single engine-propeller aircraft is due to the _ and forces generated by the _. It is essential to maintain balanced, co-ordinated flight, particularly at airspeed, high angles of _." The missing words are asymmetric and yawing forces generated by the propeller. So the propeller produces asymmetric and yawing forces — that’s the tendency to yaw, especially at high power. It’s essential to maintain balanced, co-ordinated flight, particularly at low airspeed and high angles of attack. That’s exactly when the asymmetric forces are strongest and the aircraft is most vulnerable to a spin. Then the recovery action: "In whatever configuration, attitude, or power setting a stall warning occurs, the correct pilot action is to the angle of attack below the _ angle to un-stall the , apply maximum allowable to minimize altitude loss and prevent any from developing to minimize the possibility of . 'Keep the _ in the middle'." The correct action is to reduce the angle of attack below the critical angle to un-stall the wing. Then apply maximum allowable power to minimise altitude loss. Prevent any yaw from developing to minimise the possibility of a spin. And the phrase "Keep the ball in the middle" — that’s the slip indicator ball, keeping it centred means you’re in balanced, co-ordinated flight. Finally, the shock wave case: "If a large shock wave forms on the wing, due to an inadvertent overspeed, the locally increased _ pressure gradient will cause the _ to separate immediately the shock wave. This is called ' stall'." The locally increased adverse pressure gradient will cause the boundary layer to separate immediately behind the shock wave. This is called shock stall. So when you overspeed and a shock wave forms, the pressure recovery behind it is so severe that the boundary layer separates, and you get a sudden loss of lift — that’s shock stall. And the note at the end: the full Key Facts 2 with the word inserts filled in is on page 204, so you can check your answers there. That’s the complete set of stall factors and recovery actions.