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[31指示记录] 为什么大翼防冰和发动机防冰打开,抖杆速度会增加?

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发表于 2021-5-7 18:59:09 | 显示全部楼层 |阅读模式 来自: 中国广西

空地交流机组提出了一个疑问,为什么大翼防冰和发动机防冰打开,抖杆速度会增加?由于平时基本没有接触这方面的信息,一下懵了,赶紧查手册。


最小速度是针对一定襟翼和起落架构型的最小安全操纵速度。失速管理计算机使用襟翼位置,马赫数和迎角等数据来计算最小速度。


为什么大翼防冰和发动机防冰打开,抖杆速度会增加?-1.jpg


最小速度指示在速度带底部,黑红相间,最小速度也称抖杆速度。


为什么大翼防冰和发动机防冰打开,抖杆速度会增加?-2.jpg


手册对最大迎角失速警告描述比较详细,其中包含TAI对最大迎角失速的影响。但对最小速度失速警告写的很简单,在AMM手册没有查到TAI跟最小速度的关联。


为什么大翼防冰和发动机防冰打开,抖杆速度会增加?-3.jpg

为什么大翼防冰和发动机防冰打开,抖杆速度会增加?-4.jpg


查阅飞行手册,关于防冰对抖杆速度的影响倒是提了一些,但没有写的很具体。


为什么大翼防冰和发动机防冰打开,抖杆速度会增加?-5.jpg

为什么大翼防冰和发动机防冰打开,抖杆速度会增加?-6.jpg


因为SDS直接描述是AOA偏移量,而机组问的是抖杆速度,现在资料都解答不了机组的疑问。于是发SR问了波音。波音回复大致意思如下。


 对于失速警告功能,SMYD有几个不同的子模式,其中一个子模式与防冰状态的使用有关:


  • 正常失速警告模式

  • 前缘异常失速警告模式

  • 防冰失速警告模式

  • 高推力失速警告模式 


SMYD将使用发动机或机翼防冰状态来改变PFD上的抖杆/失速速度数据。


当飞行员注意到飞行中形成的可见冰时,机翼防冰开关打开。每当机组预计到结冰情况时,发动机罩防冰开关打开。


当发动机或机翼防冰系统打开(其中一个或两个)时,SMYD将增加一个固定的,抖杆/失速速度数据的编程数字偏移,导致PFD上的最小工作速度数据增加。固定的编程数字偏移值取决于当前襟翼设置,AOA和飞机型号。


SMYD保守地提高最低运行速度,以确保飞机在结冰或可能结冰时,防止飞机失速。 


波音公司认为,机组观察结果与上述功能有关,在使用防冰系统时,系统的性能符合预期。


从波音回复的内容看,最小速度失速警告和最大迎角失速警告一样,使用防冰SMYD也会计算出一个偏置,使最小速度增加。简单说就是使用防冰也会影响抖杆速度。另外大翼防冰打开超过5秒,该航段后续剩余的飞行过程中,这个热防冰数据偏移会被锁定,即使关断了大翼防冰也不会恢复,而整流罩防冰关断后,抖杆速度是会恢复的。


波音SR原文。

DESCRIPTION:PILOT experienced the WING ANTI-ICE switch was in the ON position, The minimum operating speed was increased.And turned on the ENG ANTI-ICE switches after turned off the WING ANTI-ICE switch,The minimum operating speed was also increased.PILOT want to know why.REF /A/,/B/,/C/, The bellow is guess: The TAI bias is set when either the WING ANTI-ICE or ENG ANTI-ICE switches are in the ON position. And The SMYD calculates Vmin with data of bias Angle of Attack.so the minimum operating speed is increased. But either the WING ANTI-ICE or ENG ANTI-ICE switches are in the ON position,The thrust of the engine will be reduced due to the use of bleed air, GUN don't know whether it will also have an impact to calculate minimum operating speed.DESIRED ACTION:Q1:Why the minimum operating speed is increased when the ENG ANTI-ICE switches are in the ON position and he WING ANTI-ICE switch is in the OFF position?Q2: Why the minimum operating speed is increased when the WING ANTI-ICE switch is in the ON position?RESPONSE:Boeing thanks China Southern for their questions. Please see our responses below. Q1:Why the minimum operating speed is increased when the ENG ANTI-ICE switches are in the ON position and he WING ANTI-ICE switch is in the OFF position? Q2: Why the minimum operating speed is increased when the WING ANTI-ICE switch is in the ON position?Boeing's response to both Q1/Q2: The SMYD has several different sub modes for the stall warning function with one of these sub modes being related to use of anti-ice status: Normal Stall Warning modeLeading Edge Anomaly Stall Warning modeAnti-Ice Stall Warning mode **High Thrust Stall Warning mode** The SMYD will use either of the engine or wing anti-ice status to change the stick shaker/stall speed data on the PFD. When the pilot notes visible ice formed during flight, the wing anti-ice switch will be turned on. The engine cowl anti-ice switches are turned on whenever icing conditions are anticipated by the flight crew. When the engine or wing anti-ice systems are turned on (either one, or both), the SMYD will add a fixed, programmed numerical offset to the stick shaker/stall speed data, causing the minimum operating speed data to increase on the PFD. The value of the fixed, programmed numerical offset depends on the current flap setting, AOA and the airplane model type.  Increasing the minimum operating speed is conservatively performed by the SMYD to ensure that the airplane is protected when ice has formed or will potentially accumulate. Boeing believes that the China Southern's observation is related to the functionality described above and that the system is performing as intended when anti-ice is used.

为什么大翼防冰和发动机防冰打开,抖杆速度会增加?-7.jpg

故障案例|发动机进气整流罩防冰活门打开灯闪亮



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发表于 2021-5-8 15:21:55 来自手机 | 显示全部楼层 来自: 中国安徽宿州
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