發信人: yehd (pauken)    看板: Aero
日期: Mon Feb 21 22:43:30 2000
標題: Re: 噴射機和螺旋槳飛機


我在B777的AMM上找到BOEING對FLIGHT DECK WINDOW HEAT的說法,
個人比較懷疑的,是到底WINDOW HEAT可以讓玻璃的"韌性"改變多少?
所以,我就先找了AMM. B777的AMM開宗明義就說明了WINDOW HEAT的目的,
是在"prevent ice and fog on the flight deck windows".
一般來說,Window Heat的加熱溫度大約是100F(38C)左右(這樣的溫度在
台灣的大熱天底下晒一下就可以達到,所以我還是很懷疑加熱玻璃可以
有韌性改變的說法),目的是Anti-Ice,不是De-ice.
所以,必須在有可能結冰之前就要開始做Window Heat.
B777 AMM的內容如下:
........
FLIGHT DECK WINDOW ANTI-ICE SYSTEM - INTRODUCTION
Purpose
The window heat system prevents ice and fog on the flight deck windows.

General Description
Electric heaters in the window laminations heat the flight deck windows.
The window heat switches enable the window heat system. With window heat ON, 
the window heat control units control the power to the windows. 
With window heat OFF, the backup window heat system can operate.
..........

小弟手邊的一本參考書,列出了兩種Window Heat 的方式:
典型的是利用Electric Heater,就是在"玻璃"的內層鍍上一層導體,
當然這層"玻璃"不是單純的玻璃,前後夾有多層的Acrylic,Polycarbonate...
這層導體鍍得好到不會影響飛行員的視線,卻又可以導電.
較老式的飛機,是在玻璃窗的中間通入由客艙加熱系統引進的熱氣,
加熱窗玻璃後直接流入駕駛艙內.

小弟仍然不死心,又再找了B747-400的AMM,
這回讓我找到BOEING對Window Heat增加撞擊強度的說法.
B747-400 AMM摘錄如下:
.....
FLIGHT COMPARTMENT WINDOW ANTI-ICE SYSTEM
DESCRIPTION AND OPERATION
1.General 
A.The flight compartment windows are electrically heated to provide 
anti-icing for the No. 1 front windows and to provide defogging for 
the No. 2 and 3 side windows.  
Heat applied to the windows also increases their impact strength.
.......

當然,BOEING沒有解釋原因,但是相信和版主前面提到的原因不會差異太多.
這可說是"玻璃"材料的特性.

在UKCAA出版的CAAIP(Civil Aircraft Airworthiness Instruction Procedure)中,
提到了這樣一段,可以當做是Window Heat增加撞擊強度的官方說法:

.......
Electrically Heated Windscreen
These windscreen are used on pressurized aircraft to prevent 
the formation of ice and mist on th epanel and to improve 
the impact resistance of the windscreen panel at low temperature
(appendix 2 of D4-2 BCAR)
.......

顯然的,BCAR (British Civil Aviation Requirement)把這項特性列為
飛機的要求適航要求之一了!


--
Aircraft Mechanic, CKS Airport, Taipei, Taiwan, ROC
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* Origin: 中山大學-美麗之島BBS * From: 211.74.22.226 [已通過認證]
.