Flex? De-rated?

何謂flex temp?點解要Flex?同Derated 有咩分別?

首先, 要分清楚 Flex/Derated TAKEOFF 同Derated CLIMB 係唔同ge~

第一,點解要Flex or Derated?

其實由Turbine Engine 進入Aviation, 帶領Aviation

展開新時代.

由60年代turboJet 發展到依家Geared turbofan, turbine engine 一直改良而thrust output 同Efficiency 不斷提高.

"The GE9X engine for the Boeing 777X has been recognized by the Guinness Book of World Records as the the most powerful commercial aircraft jet engine (test performance) after reaching 134,300 lbs of thrust."

Engine Thrust output 大左, 飛機就可以帶多d loading 去飛. 雖然飛機capabale 帶多d, 但係loading 好depend on Commercial.尤其是依家航空業冰河時期, 有貨飛算好好彩.(除非飛747 d 師兄~)

例如 一個HKG-TPE A330 flight, 無客,貨又唔多, 油量又唔多; 飛機Takeoff weight得140Ton (MTOW 242T); 根本無需要Full Thrust 起飛. 為左慳d 油同maintenance cost, 就會想要個Engine 俾小D thrust.

究竟點樣同Engine 開口 講要小d Takeoff thrust?

其實飛機有時好蠢, 我地可以呃個Engine. 呃Engine 有兩個方法: 1. Flex 2. De-rated

Again, 呢個係講緊Takeoff Thrust; 同Climb Thrust 有唔同.

1. Flex (如右圖)

紅線係Max Available thrust. Temperature 愈高, Max Thrust output 愈小~

由於TOW 比較小,唔需要Full Thrust; 為左減小thrust output, pilot 會base on performance computation, 計個Flex temp出黎呃個FADEC.

Flex Temp 意思係個pilot 呃個engine, 同佢講外面好熱.

FADEC 會base on 嗰個flex temp compute for EGT limitation去provide needed thrust for actual TOW.

好似圖中, Flex TO Temp 49 degree.

通常airbus 都會用FLEX (我未用過De-rated takeoff)

Depends on Engine model, 有d 機可以Flex 75

Reduce 30~40% thrust from full thrust.

2. De-rated Takeoff

De-rated takeoff 就係呃個FADEC,話佢聽Engine變細左. 細engine, output 小d thrust.

難聽d 講, 感覺就似閹割power, 打交讓左手~

Flex 同 De-rated Takeout 有咩分別?

最大分別係Flex Takeoff可以任何時候都可以opt-to 推TOGA; 推TOGA就可以有番full thrust.

當V1 cut, 壞左一個engine ge 時候, 當需要extra thrust就可以推TOGA (但係De-rate 閹割左就唔可以!)

但係有得推TOGA 都有drawback; 因為Flex T/O 可以opt-to TOGA, 如果壞左一邊engine, differential thrust 令yaw moment 好大; 所以個Vmc,V1,VR 都會高d!

因為Derate T/O, thrust differential細D, Vmc都細d~

又因為咁, Contaminated Runway 係唔可以用Flex; 但derated 就ok.

由set power, rotate, 到左Thrust reduction altitude, 就會set thrust lever 去climb detect

正式入Climb Phrase~

Climb Phrase 好簡單~

CLB 只有De-rate, THST CLB 就係full thrust; 另外, 有DCLB1/DCLB2 ;如果我無記錯, DCLB1 就係10% thrust less; DCLB2 就20% thrust less.

有錯請講~~