Originally Posted by
john_tullamarine
Re deviation .. nil wind is the general rule .. if you want guarantees, let me offer you one .. a min V1 departure with a maximum crosswind .. will just about guarantee you a trip in the weeds before you know where you are .. the case is not considered at certification and the pilot is expected to exercise a bit of discretion in whether he should go in these circumstances ..
Ah now, ya can't really mean that!
In still wind, a engine failure at V1 will require a certain amount of rudder deflection to control.
In a crosswind, the rudder will already be deflected to keep the aircraft tracking the centreline. If an engine then fails at V1 the rudder will need to be deflected further by a similar amount to the still air case. e.g.:
Still air:
Engine failure - 50% deflection required to control.
Crosswind:
Requires 40% deflection to maintain centreline.
Engine failure - 50% deflection to control.
Total 90%
During a crosswind or in still air the rudder needs to be moved the same amount following an engine failure. You can think of it as the initial reference position of the rudder being different in the crosswind case. If you feel that a trip to the weeds is inevitable then you are implying that the rudder will hit the stop and control will be impossible. You can't honestly think that possibility has been overlooked by authorities or manufacturers. At my company on the 321 there are adjustments made to V1 for crosswinds of 20 kts or greater, although this is primarily due to engine consideration which I don't understand. (Incidentally, the change is 1 knot!)
the case is not considered at certification and the pilot is expected to exercise a bit of discretion in whether he should go in these circumstances ..
Ha ha! I don't really think that you will find many manufactureres who would agree that their aircraft probably shouldn't take off at their published crosswind limit, just in case something goes wrong. Nor do I think that pilots will say "The limit is 30 knots, it's at 25 now, why don't we wait a while cos I'm worried about not having enough rudder if an engine fails". Tea and biscuits coming eventually if you keep that up! My question is - What crosswind component would you sugeest we wait for? 30% of the limit? 50%? 75%?
The only thing I would concede in the above discussion is certain operators poilcy of not taking gusts into account. If you're engine goes bye-bye at V1 which is limited by VMCG and at the same instant a gust that is 10 knots above your crosswind limit occurs, you may have trouble. You may however just simply be the most unlucky individual on the planet!