沙盲

飛行員在飛行時的能見度減損

在航空领域,所谓的“沙盲”(brown-out)是指飞行过程中因扬起的尘埃颗粒造成的能见度障碍。[1] 在沙盲的状况下,飞行员在视觉上难以看到接近地表处所需的外部辅助目标物。[2] 这可能会导致空间定向障碍而无法掌握情况并导致事故发生。[3] 飞行员着陆时遇到沙盲,比拟这种状况就像是闭着眼睛去做路边停车一样困难。[4]

一架HC-130 大力神在一条沙地跑道上陷入沙盲状态。
隶属于845 NAS的海王直升机于2013年约旦沙漠中的演习。
CH-47契努克的下降气流扬起的沙尘云导致的沙盲。

详细说明

沙盲容易导致直升机在干旱沙漠地区着陆和起飞时发生事故。 在近地飞行阶段,直升机旋翼下沉气流会扰动并造成剧烈又能见度差的粉尘云,可能导致飞机和地面障碍物碰撞,或由于倾斜和不平坦的地形导致动态侧翻,进而造成重大飞安风险。[5] 在近几年(自2005年起)的军事行动中,沙盲对直升机造成的危害已经比其他威胁总和还多。[6]

有几个因素会影响到沙盲发生的几率与严重性:[6]

  • 旋翼的翼面负载
  • 旋翼的配置
  • 土壤成分
  • 接近时的速度与角度

避免沙盲导致意外的对策:

  • 着陆点的准备措施
  • 飞行员的技巧
  • 合成视觉系统[7]
  • 具备改良过符号标示的升级型水平状态指示器[8]
  • 空气动力学,例如 AgustaWestland EH101 机型的旋翼末端上的翼型设计(winged-tip)[9]
  • 透过感测器衍生出的姿态与方向资料非视觉型指示器,例如 Tactile Situational Awareness Systems (TSAS) 透过触感的方式提供飞行员相关资讯。

参考资料

  1. ^ Special Investigation Report on Emergency Medical Services Operations (PDF). PB2006-917001. National Transportation Safety Board. June 2001 [2007-06-26]. NTSB/SIR-06/01. (原始内容存档 (PDF)于2021-09-28). Brown-out conditions connote in-flight visibility restrictions due to dust or sand in the air. 
  2. ^ Key, David L. Analysis of Army Helicopter Pilot Error Mishap Data and The Implications For Handling Qualities (PDF). 1999-09-14 [2007-06-23]. (原始内容 (PDF)存档于2006-06-03). 
  3. ^ Stein, Vicki. AFOSR News – National Helicopter Experts Gather to Discuss Aerodynamic Solutions for Brownout. The Air Force Office of Scientific Research, AFRL. 2007-02-12 [2007-06-25]. (原始内容存档于2014-12-03). 
  4. ^ Skiba, Katherine M. U.S. helicopter crash-lands in Iraq, injuring pilots, crew. Milwaukee Journal Sentinel. 2003-04-07. Pilots have compared landing during brownouts to parallel parking a car with your eyes closed. 
  5. ^ STO: Solicitations - Sandblaster Program. Defense Advanced Research Projects Agency. [2007-06-24]. (原始内容存档于2007-05-18). 
  6. ^ 6.0 6.1 Colby, Lt. Col. Steve. Military Spin. Rotor & Wing (Access Intelligence, LLC). 2005-03-01 [2023-06-15]. (原始内容存档于2007-09-03). Brownouts have claimed more helicopters in recent military operations than all other threats combined. 
  7. ^ News in Brief / Kurzmeldungen. Flug Revue (Germany) (Motor-Presse Stuttgart). 2007-03-18. (原始内容存档于2007-07-07). 
  8. ^ Vertiflight Breaking News : Army Prepares Brownout Kit. AHS International. July 2004 [2007-06-28]. (原始内容存档于2007-09-28). The [multi-function display] replaces the standard horizontal situation indicator and shows the crew digital ground velocity, analog vertical velocity, digital and analog radar altimeter, and analog heading symbology. 
  9. ^ Harvey, Gareth. Super Chopper : Life-Saving Features: No More Brown-Outs. Engineering Archives. National Geographic Channel. 2005-11-28 [2009-08-01]. (原始内容存档于2009-07-21). To counteract this, the EH101’s ‘winged-tip’ rotor blades create what its pilots call the “donut effect” – a circular window of clear air inside the dust storm that allows them to see the ground as they come in to land.