Originally Posted by
FlightDetent
What are those speeds, then?
The competitor is clearly designed for Vat = Vref = 140 kts at MLW, to stay inside ICAO category C.
The increased weight A321 went over, but this was culled back with the NEO...
Resulting Vapp is 145 at MLW due the A/THR / handling / wind additive.
I can guess Vf=30 will bring some extra speed over Vref, but is f40 not the standard for the -800?
Actually, having a quick look at the manuals,
I stand corrected on the Vref that is used for the B737NGs at least. A bit more digging brings up an anecdotal reason for the change unrelated to the tail geometry. The info is related to the stick shaker margin, which is set to trigger before the stall, so there is an offset of the margin per
§ 25.207 - Stall warning. VSW is normally +5KIAS or +5% of VSR.
I would suspect that there was an increase in VSW for the 600 above the =5KIAS/+5% level for handling, which gives a lower delta from VSW to Vref than the VSR to Vref. Not sure if the B737 was ever amended to 1.23 for refs instead of 1.3, but anyway, at all times, it meets the 1.23 level anyway, and if still certified to 1.3 then the stall warning margin was increased above the §25.207 requirements.
For VSW:
B737-600:
Vref40= ~1.46g
Vref30= ~1.44g
B737-700:
Vref40= ~1.42g
Vref30= ~1.43g
B737-800:
Vref40= ~1.53g
Vref30= ~1.61g
B737-900:
Vref40= ~ 1.54Vs1g
Vref30= ~ 1.66 Vs1g
Adjusting to Vrefxx/Vs1g:
B737-600:
Vref40= ~1.27 Vs1g
Vref30= ~1.26 Vs1g
B737-700:
Vref40= ~1.25 Vs1g
Vref30= ~1.26 Vs1g
B737-800:
Vref40= ~1.30 Vs1g
Vref30= ~1.33 Vs1g
B737-900:
Vref40= ~ 1.30 Vs1g
Vref30= ~ 1.35 Vs1g