Freezing Rain
Joined: Dec 2007
Posts: 57
Likes: 0
From: VIENNA
It is interesting to hear, how people are differnet interpreting the hold-over-time and weather conditions:
1. The tables of FAA, Transport Canada and Association of European Airlines (use most in the world) are absolutely identicial for these weather categories. So none of them is stupid or all of them.
2. Please be more precise: Absolutely no hold-over-time exists for moderate or heavy freezing rain. But some tiems exists for light freezing rain and freezing drizzle.
3. the given times for these weather conditions are very short. So only if you make the treatment directly at the runway with runnign engines you have a chance.
4. The whole tables are questionable, as they are based only on a few datapoints and for my opinionm not enough substantiated. But at the moment nothign better available.
5. My experience is, being of of these "idiots" involved in the development of these tables, that the most people are simply not properly trained to understand them. they are not easy to read with all the cautions and notes, but the airlines are not spending enough time.
If you want to get a punch of good information free of charge, go and register as a "Mail Recipient" with the SAE G12 Committee. Or better attend and help to improve it.
Just calling everybody else here, like some of you do, idiots, shows only that you have a problemto understand these tables and weather conditions.
1. The tables of FAA, Transport Canada and Association of European Airlines (use most in the world) are absolutely identicial for these weather categories. So none of them is stupid or all of them.
2. Please be more precise: Absolutely no hold-over-time exists for moderate or heavy freezing rain. But some tiems exists for light freezing rain and freezing drizzle.
3. the given times for these weather conditions are very short. So only if you make the treatment directly at the runway with runnign engines you have a chance.
4. The whole tables are questionable, as they are based only on a few datapoints and for my opinionm not enough substantiated. But at the moment nothign better available.
5. My experience is, being of of these "idiots" involved in the development of these tables, that the most people are simply not properly trained to understand them. they are not easy to read with all the cautions and notes, but the airlines are not spending enough time.
If you want to get a punch of good information free of charge, go and register as a "Mail Recipient" with the SAE G12 Committee. Or better attend and help to improve it.
Just calling everybody else here, like some of you do, idiots, shows only that you have a problemto understand these tables and weather conditions.
Joined: May 2003
Posts: 831
Likes: 0
From: The Roman Empire
I had an argument once about this: it was raining, end the reported temperature was 0°C.
There was absolutely no sign of a layer of ice being formed on anything. Just raining normally.
Would you define that Freezing Rain?
I think the definition implies the actual forming of a (thin) layer of ice on objects exposed to freezing rain.
There was absolutely no sign of a layer of ice being formed on anything. Just raining normally.
Would you define that Freezing Rain?
I think the definition implies the actual forming of a (thin) layer of ice on objects exposed to freezing rain.
Joined: Dec 2007
Posts: 57
Likes: 0
From: VIENNA
Freezing Rain (and Freezing Drizzle) have the "freezing factor" (coldness) in the transported liquid.
If the OAT is at or above 0° C and the rain freezes than we talk about "rain on cold soaked wing", which is a seprate category in the hold-over-time tables and gives the shortest protection at all.
Looking into incident statistics, "Rain on cold soaked wings" is the most critical one, as a lot of ground and flight crews completely ignore the fact of a cold wing. Otherwise, how you can explain that we still have engine FOD's by clear ice after identifying the problem 25 years ago.
Finnair did a few years ago a study on the wing temperature durign the take-off run and take-off. The result had been that in the lift-off face the wing temperature drops dramatically. This fatcor must be taken additonally into consideration.
Looking on the existing test data, the accident and incident statistics as well as from my own experience:
- No hold-over-time for Type I Fluids at all, except in "Active Frost"
- Deletion of the 3° buffer for Type I Fluids in a Two-Step Procedure
- Starting the project to install temperature probes in the wings to get more precise information about the wing temperature
If the OAT is at or above 0° C and the rain freezes than we talk about "rain on cold soaked wing", which is a seprate category in the hold-over-time tables and gives the shortest protection at all.
Looking into incident statistics, "Rain on cold soaked wings" is the most critical one, as a lot of ground and flight crews completely ignore the fact of a cold wing. Otherwise, how you can explain that we still have engine FOD's by clear ice after identifying the problem 25 years ago.
Finnair did a few years ago a study on the wing temperature durign the take-off run and take-off. The result had been that in the lift-off face the wing temperature drops dramatically. This fatcor must be taken additonally into consideration.
Looking on the existing test data, the accident and incident statistics as well as from my own experience:
- No hold-over-time for Type I Fluids at all, except in "Active Frost"
- Deletion of the 3° buffer for Type I Fluids in a Two-Step Procedure
- Starting the project to install temperature probes in the wings to get more precise information about the wing temperature
