Category: Aviation

Maximum Glide Range?

Ans : two manoeuvre factors – 1. optimal angle of attack 2. minimum drag speed 當上面兩樣野做到又吾計wind , 理論上隻機就會飛 @ max L/D ratio 記著: 重量同max glide range 無關! 取決上面說的兩個操作factors – 大機同細機glide range 一樣 ! Read More

Pilot math

計數係惡夢 但方法還是有 🤭 Ref skybrary: https://skybrary.aero/articles/rules-thumb   時間 Time 6 mins 0.1 hour 3 mins 0.05 hour   方位 Reciprocal Heading = HDG +200 – 20 or = HDG – 200 + 20 大過200就- 先 ; 細過200就+ 先 e.g 090 : 90 + 200 – 20 = 270 270 : 270 – 200 + 20 Read More

NITS Briefing

Ref: https://simpleflying.com/how-pilots-handle-aircraft-failures/ 有d知識或技巧不常用就會忘記 所以要溫書📚 🫣🤗 When executing the decision, all relevant parties must be informed in the proper order. Firstly, the appropriate ATC must be contacted and briefed about your decision to return or divert to another field. Then the lead cabin crew or the purser must be called to the cockpit to be informed Read More

Ground effect 對不同flight status 的影響? (就Ground Effect 有咩係機師要知, 有咩要做?)

Ref Ch5 Ans: 機師要記著  – T/O phase not attempt to force the acft T/O with not sufficient takeoff speed (due IAS 假象!) never retract the landing gear or flaps prior to establish +ve rate of climb never retract the landing gear or flaps prior reaching MSA (minimum safe altitude)   Landing phase  reduce power to Read More

Ground effect 有咩影響? Significance of ground effect?

Ref Ch5 Ans:  Upwash↓ , downwash ↓  –> Wingtip vortices ↓  –> induced drag ↓  –> AOA need to be reduced for same CL  Local pressure on static source [position (installation) error] –> airborne IAS reduce 假象   Induced Drag 成因? What’s ground effect? Read More

What’s ground effect?

Ref Ch5 Ans: air cushion phenomenon The reason of ground effect is that the air that is trapped between the wing and the landing surface, as if there were an air cushion. When the plane is very close to the surface (say just before touchdown),  it would suddenly feel like the plane did not want Read More

Strategy to avoid wake turbulence?

Ref Ch5 Ans:  飛緊 : avoid similar flight path with 1000 ft vertical separation T/O : rotate before the point at which preceding acft rotated  LAND : approach above preceding acft’s flight path  LAND : touch down after the point where other’s wheel contact If doubt, 用 3 mins margin time (rule of thumb) For Read More

When the wingtip vortices are greatest?

Ref Ch5 Ans: heavy, clean, slow   Vortices 正比 Weight Vortices 反比 Wingspan Vortices 反比 Speed   所以大機, 無落FLAPS, TAKE OFF/APPROACH 果陣最勁~ 因為大機重, 無FLAPS 要產生升力, AOA 自然大, INDUCED DRAG as well as Wingtip vortices 就當然大   Read More

點解vortices 係 wingtip ? The formation of wingtip vortices~

Ref Ch5   Ans: pressure differential (between upper and lower surfaces of wing) air always moves from high pressure toward low pressure bottom : span-wise movement of air  (outward from fuselage to and around tips) upper surface : span-wise movement  (flow in toward fuselage and off the trailing edge) fuselage limits the inward flow – Read More

Induced Drag 成因?

Ref Chapter 5 Ans: air tends to flow from the high pressure area to low pressure area higher pressure at the bottom of airfoil vortices is created (at wing tip) – wingtip vortices vortices roll off, and create a downwash downwash points the relative wind downward lift is tilted  the more the tilted lift, the Read More

What’s Induced Drag?

Ref Chapter 5 Ans: inherent drag due to lift production.   Induced drag is inherent whenever an airfoil is producing lift and, in fact, this type of drag is inseparable from the production of lift. Consequently, it is always present if lift is produced. AOA increases, induced drag increases proportionally When view from the tail Read More

What’s boundary layer?

Ref Chapter 5 Ans: the layer of air between the wing and free-stream velocity level   The area between the wing and the free-stream velocity level is about as wide as a playing card and is called the boundary layer. Read More

Free-stream velocity?

Ref Chapter 5 Ans: the speed at which molecules are moving at the velocity that same as the air moving around the aircraft.   Each layer of molecules above the surface moves slightly faster until the molecules are moving at the velocity of the air moving around the aircraft. This speed is called the free-stream Read More

Skin friction Drag?

Ref Chapter 5 成因: contact of moving air with the surface of an aircraft 解決/緩解方法: flush mount rivets remove any irregularities that may protrude above the wing surface smooth and glossy finish remove dust and dirt   no matter how apparently smooth, has a rough, ragged surface when viewed under a microscope Read More

Interference Drag?

Ref Chapter 5   成因: intersection of airstreams (that creates eddy currents, turbulence, or restricts smooth airflow) 解決/緩解方法: Fairings    most interference drag is observed when two surfaces meet at perpendicular angles (e.g wing and wing root)       Read More

Form Drag?

Ref Chapter 5 成因:   shape and airflow around the airfoil (aircraft) 解決/緩解方法: streamline                                   (as many of the parts as possible)   When the air has to separate to move around a moving aircraft and its components, it eventually rejoins Read More

Parasite Drag?

Ref Chapter 5 Three sub-type of parasite drag Form Drag Interference Drag Skin Friction Drag not associated with the production of lift Types of Drag? Read More

Types of Drag?

Ref Chapter 5 Ans: Parasite Drag, Induced Drag Read More

Air Density , 3H?

Ref Chapter 5   Ans: Air Density drop (air becomes less dense) when  High altitude  (高度)  High temperature   (溫度)  High humidity  (濕度) Read More

What’s stalling AoA? What’s CL-max Critical AoA?

Ref Chapter 5   Ans: the AoA at which after that the acft will stall! Remember: aircraft (airfoil) always stalls at the same AOA! When the aircraft reaches the maximum AOA, lift begins to diminish rapidly. This is the stalling AOA, known as CL‑MAX critical AOA.   Notes: generally, 20° AOA is the critical angle Read More

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