感谢周焕然机长的问题。
我们知道，当性能页面输入的温度低于 ISA 时，FLS 能够对下滑剖面做低温修正。解惑之前，VD 上的FLS 下滑到和 FMS 计划的下滑道会分离显示，以提示机组。截获后则重合，以避免干扰。
那么如果输入温度高于 ISA, 那么会不会做高温修正呢？
空客回复说不会修正，VD 上的下滑航径也不会分离。因为低于剖面可能会存在地形风险，而高于剖面虽然会造成剖面稍陡，但风险不算很大，可以接受，并不需要专门设计功能来规避。
原文
Q:
When the temperature inputed in ACTIVE/PERF APPR page above ISA, will FLS do the hot correction? Will the FLS beam and FMS trajectory be apart?
A:
Further to your recent request regarding the temperature correction for FLS for your A350 aircraft, Airbus would like to provide the following comments for your information:
To clarify, we would like to indicate to CSC that, as indicated in FCOM DSC-22-FMS-10-30-40 - FLS Beam Computation - COLD WEATHER CORRECTION OF THE FLS BEAM, the computation of the FLS beam and the F-G/S deviation are corrected only if the temperature at destination (i.e. entered in the APPR panel of the PERF page) is below the ISA temperature.
For more information about the FMS Trajectory and FLS beam displays in the VD in the case of cold weather, please also refer to FCOM DSC-31-CDS-40-50 VD - COLD WEATHER DISPLAY.
It means that, when the temperature entered is above ISA temperature (i.e hot temperature), there is no correction. As a result, the FLS beam is not offset, and the aircraft will fly a slightly steeper final path than in standard atmosphere conditions.
The reason of this specific design is to prevent flying too low if erroneous temperature entry is performed on PERF page page (e.g. for example 30°C instead of -30°C).
Indeed, for safety aspect, the temperature correction is more useful for temperature below ISA conditions.
In fact, in these conditions, the real aircraft altitude is lower than the measured aircraft altitude. So, the safety altitudes might not be respected without temperature correction.
Above ISA conditions, the aircraft will follow a FLS beam with a more important slope than the indicated one (i.e. aircraft slightly above the database FLS beam) but this drawback is acceptable from a safety point of view.
