菜英文 asked in 汽車與交通航空器 · 1 decade ago

民航機飛行數據的揭示

在製造年份比較新的民航機,都會全程在螢幕上隨時提供重要的飛行數據,例如飛行速度、飛行高度等。我尤其喜歡一面看窗外景致的變化,一面看看飛機降落時高度和速度急遽的變化。

但是我多次發現當飛機已經落地時,高度應該是「零」才對,但螢幕上還是顯示有數十公尺的高度,和感覺上高於滑行速度的飛行速度數據。

請問:這些供乘客在螢幕上觀看的飛行數據,難道不是即時(Real-time)的數據嗎?既然要提供,為何不提供即時數據呢?

Update:

Feedback to Dynastyflier:

I understand how GPS functions. There is a gap between the actual postion and the GPS map position for all GPS divices due to the time lag caused by the belated satellite signal receiving.

Update 2:

As today's computers capability, there should not be any time lag. The in-plane computer could display the realtime flight information both to pilots and passengers as well. Why it is not? That is my question.

Update 3:

But I don't think the GPS case applies to the flight information display in the passenger cabin. The flight information (such as speed and altittude) is processed by in-plane computers which can directly connected to passenger cabin flight information display screens.

Update 4:

I put the second and third paragraphs in wrong sequence. The second should be the last.

Update 5:

我下次搭機時注意高度上的誤差是否來自於海平面高度與機場實際高度。不過飛機乘客不是專家,在飛航資料上的揭示,應該不出於一般人「常識」的範疇。

謝謝康康和Mason的解答,讓我又增長了知識。

3 Answers

Rating
  • 1 decade ago
    Favorite Answer

    PFIDS - Passenger Flight Informance Display System.

    所提供給乘客的資訊:

    1.TIME TO DESTINATION

    2.GROUND SPEED

    3.DISTANCE TO DESTINATION

    4.OUTSIDE AIR TEMPERATURE (actual)

    5.GREENWICH MEAN TIME (actual)

    6.LOCAL TIME AT DESTINATION (same as local time)

    7.ESTIMATED ARRIVAL TIME (local time time to destination)

    資料來自飛機的 Air Data Computer & Flight Management Computer:

    1.Air Data Computer (ADC).

    ADC Interface:

    a.Pitot and static air pressure from the pitot-static system. 速度

    b.Angle of attack from the AOA sensors. 攻角

    c.Total air temperature (TAT) from the TAT probes. 溫度

    d.Barometric pressure correction from the EFIS control panels. 場壓

    2.Filght Management Computer (FMC).

    FMC Interface:

    a.Inertial Reference System (IRS). 位置

    b.Global Positioning System (GPS). 位置及時間

    c.Clock. 時間

    d.ADC. (提供修正因數)

    e.NAV Data 計算距離

    --------------------------------------------------------------

    發現當飛機已經落地時,高度應該是「零」才對,但螢幕上還是顯示有數十公尺的高度,和感覺上高於滑行速度的飛行速度數據。請問:這些供乘客在螢幕上觀看的飛行數據,難道不是即時(Real-time)的數據嗎?既然要提供,為何不提供即時數據呢?

    PFIDS - Passenger Flight Informance Display System

    是即時的資訊數據,這些資訊來自飛機的ADC及FMC,跟駕駛艙內的數據是一樣的.

    但為何飛機落地後高度不是零呢?

    原因是PFIDS的高度資料來自Air Data Computer (ADC),

    ADC高度是機場大氣壓力修正後所以得到的 " 海平面機場高度 " .

    PFIDS的飛行速度也是來自ADC, 但在地面低速滑行時ADC比身並無法真正算出"低速度"(沒有衝壓).所以在您的資訊顯示上會不是那麼正確.

    飛機的滑行速度來自輪胎速度 or IRS, GPS. 機距離地面的實際高度 - Radio Altimeter (RA) System. The RA system provides measurement of absolute altitude (height above terrain) from 2500 feet to touchdown.但PFIDS並未與上面的系統連結,無法顯示給乘客.

    2007-09-22 00:06:00 補充:

    Pitot and static air pressure from the pitot-static system. 速度 & 高度

    Source(s): 一天到晚搞飛機!
  • Mason
    Lv 7
    1 decade ago

    資訊來源康康已經提供不再贅述。

    簡單的講,每個機場的標高(離標準海平面高度)都不一樣,一般機場高度在飛行上以英尺表示,例如桃園機場標高106英呎,落地時飛機的儀表顯示高度是100呎左右。到曼谷當地機場標高20英呎,您看到的就是20英呎左右,有可能會換算成公尺!

    至於速度,有的來源是GPS,有的來源是IRS,有GPS的會準確一些,沒有GPS的因為IRS在開啟一段時間之後會有極大的誤差((飛行時間越久誤差越大),在落地之後滑行,明明感覺只有時速30公里,顯示可能會達到50或者60公里(飛行上使用海里為單位,數據已經換算成公里)。

    另外乘客的資訊顯示系統偶而也會出問題,有的時候資訊不曉得是哪裡抓來的,有一次在飛機上,才剛起飛,空服員來報告,有乘客反映資訊顯示已經離起飛地數千公哩,好像有點秀逗。

  • 1 decade ago

    I am not sure if you own a GPS in your car... That GPS in your car also displays the speed of your car and the direction it travels. But if you are pay attention to the speed in the GPS, it does not exactly matches the one in your vehicle. Many times that your car is already stopped completely, but your GPS is still showing 20~0 km/h. And the direction are moving around and never goes on one direction.

    Maybe the information on the display of the the monitor is the same as the one for like the one for the GPS, so they are just an aid, but not an accurate read out...

    I hope this answers your question... If not, sorry but I have tried.

    Source(s): ~Self~
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