Originally Posted by
BlueSkies
Well it's in the May 737 Fleet Newsletter for one, not sure where else to find it if you're not lucky enough to be on the 737.
Specifically they say "the amount of tw is now capped to preserve RATOW margin above RMWT/TOWT. The max tw displayed will be set to TW00 when the rwy hdwind component is 5 kts or greater."
The article continues with more information, but that seems the most relevant to our discussion. At first I was happy about going to the PLW because it seemed simpler, but flying today and checking our WDRs and seeing they all had TW00 on every line I'm concerned.
So I guess the idea is to have a larger weight buffer at the expense of having ANY tw protection? Aren't we just trading one problem for another? And a problem that requires you to:
1. Hear ATC say the winds when all you're listening for is "cleared for T/O" and
2. Do quick mental math and realize you now have as little as 1 kt of TW making the T/O numbers invalid
And as others have already mentioned the ATIS could be saying 5 kt hdwind all day long but all the matters is tower gave you a wind read-out with a tailwind.
The problem is the system only looks at the HW/TW
component. For a hypothetical RWY36, winds 08015 are a 3kt headwind, so the WDR spits out TW02 (current wind component minus 5). We all know how easily that can swing to 10015 from tower, and now you have a 3kt tailwind and a canceled takeoff.
I like the new procedure because it's intuitive. I personally haven't run into the tailwind issue, but I'm sure the program will be tweaked if enough people have to cancel takeoff. I'm thinking if the current or forecast winds are close to 90°, than give us an automatic TW05.