On the crosswind runway with flying speed, good thing or bad?

[Ed Cesnalis]

Runway 27 at Mammoth Yosemite endures a turbulent crosswind sufficient to overcome control authority of a light sport on the runway with flying speed frequently throughout the year.

It's important to me to understand when it's a positive and when it's a negative to be on the runway in crosswind/shear with flying speed.

Positive and Negative times to have flying speed when on the runway in a plane with light wing loading

• Benefit -  Takeoff roll prior to rotation. A higher than calm wind rotation speed along with a non-elevated nose wheel can provide directional control throughout the critical speed.
• Problem - Landing roll. When slowing through the critical speed with nose wheel or both mains or all three on the runway directional control can be lost if not avoided by a successful go around.

Notice that I'm saying that in 1 case risk is elevated and in the other case safety margin is increased yet the condition is the virtually the same in both cases. There are in fact 3 distinctions:

1. Mindset - On landing your intent is to slow which brings you into the vulnerable speed range. On take off your intent is to escape the vulnerable condition prior to testing it to loss of control.
2. Energy State - On landing your throttle is partial or closed and your energy state at the vulnerable speed is lower and lowering making a go around escape more time consuming by the time it takes to react, advance the throttle and spool up the Rotax.
3. Prior testing - On landing you are assuming that conditions will permit you to slow and stop or turn off the runway without loss of control. The velocity and frequency of the gusts determine this and in a landing sequence you encounter 1st the vulnerable transition speed and 2nd the slower rollout / taxi speed without testing if you will have control authority to overcome gusts.  Prior to takeoff you have already taxied and turned in the current conditions and have a basis to decide that you can accelerate enough to take off or abort without loss of control.

Above is my experience and thinking when picking a rotation speed on takeoff. It's also my thinking on why I land with my stick full aft and hold it off as long as I can. If that part sucks I land elsewhere rather than landing at a higher speed and possible having my rollout suck.

 

[FlyingMonkey]

What if you have to abort the takeoff close to rotation speed?  Doesn't your "benefit" instantly transform into a "problem"?

[Ed Cesnalis]

1 hour ago, FlyingMonkey said:

What if you have to abort the takeoff close to rotation speed?  Doesn't your "benefit" instantly transform into a "problem"?

Sure it does. Close to a higher rotation speed is where you are flying while you have wheels on the runway and are most vulnerable.  Crosswind / shear takeoffs have elevated risk as well just not as a high speed landing.