7.4 Commander’s decision
7.4.1 The Commander can supersede the ground crew member’s judgement not to de-ice the aircraft. But if either maintenance or the captain decides the aircraft needs to be deiced then it must be deiced. The aircraft must be clean for departure.
7.4.2 As the Commander is responsible for the anti-icing condition of the aircraft during ground maneuvering prior to takeoff, he can request another anti-icing application with a different mixture ratio to have the aircraft protected for a longer period against accumulation of precipitation. Equally, he can simply request a repeat application.
7.4.3 Therefore, the Commander should take into account forecast or expected weather conditions, taxi conditions, taxi times, holdover time and other relevant factors. The Commander must, when in doubt about the aerodynamic cleanliness of the aircraft, perform (or have performed) an inspection or simply request a further de/anti-icing.
7.4.4 Even when responsibilities are clearly defined and understood, sufficient communication between flight and ground crews is necessary. Any observation considered valuable should be mentioned to the other party to have redundancy in the process of decision making.
Issue II 02.07.2009 Rev. 0
CHAPTER 8 PERFORMANCE ON CONTAMINATED RUNWAYS PAGE 8-1
PERFORMANCE ON CONTAMINATED RUNWAYS
8.1 BRAKING PERFORMANCE
. The presence of contaminants on the runway affects performance due to :
-A reduction of the friction force (μ) between the tire and the runway surface,
- An additional drag caused by contaminant spray impingement and contaminant displacement drag,
- Aquaplaning (hydroplaning) phenomenon.
. There is a clear distinction between the effect of fluid contaminants and hard contaminants:
-Hard contaminants (compacted snow and ice) reduce the friction forces.
- Fluid contaminants (water, slush, and loose snow) reduce the friction forces, create an additional drag and may lead to aquaplaning.
.
To develop a model of the reduced μ according to the type of contaminant is a difficult issue. Until recently regulations stated that μ-wet and μ-cont can be derived from the μ observed on a dry runway (μdry/2 for wet runway, μdry/4 for water and slush).
.
Nevertheless, recent studies and tests have improved the model of μ for wet and contaminated runways, which are no longer derived from μdry. The certification of the most recent aircraft already incorporates these improvements.
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：Cold Weather Deicing/Anti-icing Manual 寒冷天气除防冰手册 Operations Manual Training 运行手册培训(8)
