Originally Posted by
punkalouver
I find this quote from the report interesting:
"CL-604 Operating Manual The manufacturer’s Operating Manual (OM) stated in ‘NORMAL PROCEDURES, Approach and Landing’ that VREF+X is calculated by adding a wind correction of ‘half steady state crosswind plus all gust (regardless of direction). Maximum correction is + 20 KIAS’ to the VREF. For the reported wind of from 300° at 13 kt gusting 25 kt, and a VREF of 123 kt, this equates to a VREF +X of 142 kt".
On most airliners, it has traditionally been half(or a third) the steady state headwind plus all of the gust.
Anybody seen this before on other aircraft?
I was surprised when I read that in the report. I expected them to pick up on the fact that it is a typo that was corrected in the AFM years ago, but the OM has not been updated to match. Legally that shouldn't matter as the preamble states that in case of discrepancy the AFM takes priority. But in reality there is a lot of scope for confusion.
But in this case it actually worked in their favour since it went some way to mitigating the incorrect initial calculation of Vref. Again I am surprised the report did not delve deeper into why they got the figure they did, but it is consistent with them not spotting that a database update has cleared the defaults. This sometimes happens, and one of the items cleared is the DOM figure, which reverts to the factory setting. so all the FMS speeds would be based on a mass around 4000lbs too low, or around 15%.