Holdover Times on FAA tables (snow, snow grains or snow pellets)
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Holdover Times on FAA tables (snow, snow grains or snow pellets)
In preparation of the upcoming winter season, I have read FAA official guidance holdover tables and allowance times for use during WINTER 2013-2014.
In our company we publish the brand specific (as published by the FAA) holdover tables for use out of our home base because we are 100% aware of what fluid brands are used.
In outstations we use the generic tables (as published by AEA) which, if I understand it correctly, are publishing the shortest holdover times of all brands available on the market (safe side) for a specific type (II, III or IV) of fluid. For Type I fluids both the FAA and AEA do not publish brand specific holdover times. The FAA does make a distinction between aircraft surfaces composed predominantly of composites and surfaces composed predominantly of aluminium.
I have noticed that on the FAA tables for Snow, Snow Grains and Snow Pellets that a distinction has been made between very light, light and moderate snow, but still a time-span is provided (different values depending on OAT and fluid concentration)
.
The AEA document stipulates that the lower limit of the published time span is used to indicate the estimated time of protection during moderate precipitation and that the upper limit indicates the estimated time of protection during light precipitation. Does this information also apply to the FAA tables?
Could anyone provide guidance on how this time span on the FAA tables (for snow, snow grains or snow pellets) are to be interpreted? Is this to be understood that in ideal situations the larger value (longer HOT) can be used whereas in less favourable conditions (such as high wind speeds, jet blast, and wing temperature well below OAT) the smaller value (shorter HOT) would be more appropriate?
Thanks!
In our company we publish the brand specific (as published by the FAA) holdover tables for use out of our home base because we are 100% aware of what fluid brands are used.
In outstations we use the generic tables (as published by AEA) which, if I understand it correctly, are publishing the shortest holdover times of all brands available on the market (safe side) for a specific type (II, III or IV) of fluid. For Type I fluids both the FAA and AEA do not publish brand specific holdover times. The FAA does make a distinction between aircraft surfaces composed predominantly of composites and surfaces composed predominantly of aluminium.
I have noticed that on the FAA tables for Snow, Snow Grains and Snow Pellets that a distinction has been made between very light, light and moderate snow, but still a time-span is provided (different values depending on OAT and fluid concentration)
.The AEA document stipulates that the lower limit of the published time span is used to indicate the estimated time of protection during moderate precipitation and that the upper limit indicates the estimated time of protection during light precipitation. Does this information also apply to the FAA tables?
Could anyone provide guidance on how this time span on the FAA tables (for snow, snow grains or snow pellets) are to be interpreted? Is this to be understood that in ideal situations the larger value (longer HOT) can be used whereas in less favourable conditions (such as high wind speeds, jet blast, and wing temperature well below OAT) the smaller value (shorter HOT) would be more appropriate?
Thanks!
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Does this information also apply to the FAA tables?
Could anyone provide guidance on how this time span on the FAA tables (for snow, snow grains or snow pellets) are to be interpreted? Is this to be understood that in ideal situations the larger value (longer HOT) can be used whereas in less favourable conditions (such as high wind speeds, jet blast, and wing temperature well below OAT) the smaller value (shorter HOT) would be more appropriate?
Could anyone provide guidance on how this time span on the FAA tables (for snow, snow grains or snow pellets) are to be interpreted? Is this to be understood that in ideal situations the larger value (longer HOT) can be used whereas in less favourable conditions (such as high wind speeds, jet blast, and wing temperature well below OAT) the smaller value (shorter HOT) would be more appropriate?
Yes.
And yes.
It applies to the FAA's interpretation as well. Upper limits of HOT for lighter precip, and lower limits for heavier.
Bottom line, common sense always applies. If you exceed your HOT you may still depart after a visual inspection (done in an approved manner, e.g. surface inspected from approved location--specific door/window, etc.).
Hope that helps.
