Crfi Question? Need Help Asap

[imfsub12]

yes have a question that i need help with for school.... it goes like so?

1.With a CRFI report of .21 in -35, what is the max. headwind and crosswing compenents?

That is the question if you can answer it please explain how you get the winds with out the winds in the question as i see in the aip in air 1-14 it the chart for this but they give the wind at tower for you... but my question no winds????

 

[gannet]

Well, without winds ref a runway, I would say that the best you can do is to figure out x-wind component. Max headwind depends on wind velocity and bearing ref the runway, so you have insufficient info to determine max headwind. Unless there is a typo with the question, I would answer what you can, and document your logic.

 

[Vortex Ring]

😉 You poor poor plank drivers, learn to fly a helicopter and all of this will go away, you just pedal turn into wind, every time, and fly off. 😛

 

[imfsub12]

thanks i thought the question was bloched......

and votex if you give me another 60 g's i can get my helicopter license and we can fly formation someday, hows that sound... oh you may can get a deal as i have my cpl already....

B)

 

[Swamp Donkey]

Ahhhhh....fling wings. All those parts trying to go different directions at once. Kinda makes me nervous! :blink:

 

[flyguy93]

.21 CRFI !!!! that a runway in real bad shape... Think about it in reverse order. CRFI determines what kind of friction you will have with the runway on touch down.
The friction is detrimental for two reason:
1. to maintain directional control when the all aerodynamic control is null, through steering by using the nose gear and the main gear to maintain that same directional control if there is a existing x-wind.

2. For braking action regardless of the amount of x-wind or headwind conditions existing.

needless to say even if you have a long runway but a strong x-wind you still won't be able to conduct a safe landing unless you have the required crfi due to the fact that you need to maintain that directional control once you slow down. So the determining factor for a CRFI is the x-wind and as you can see from the graph provided in you AIP that it increases proportionally with the amount of X-wind.

Simply determine the amount of max X-wind with a CRFI you quoted (.21) and follow that same line to the intersecting headwind component to find a ridiculous 3-4kts max headwind component to an astounding 1kt X-wind component.
Chances are you won't be landing on this runway unless you got skis especially at -35....

Cheers

 

[gannet]

flyguy93,

Can you explain how you found the max headwind without a relative angle of the winds to the runway? This graph requires a minimum of 2 of 4 variables to determine the intersection point. With only one variable, it is impossible to answer definitively. For instance, if given only the relative angle of the wind, you can find max headwind and crosswind components for CRFI values, but if the question was worded, "The wind is 30degrees off runway heading, what is min safe CRFI?" you can see that another variable is needed to solve. There is no doubt that the runway in the question is very slick and an aircraft would be in an extremely delicate situation. However, a x-wind value extends from the x-axis of the graph to infinity. One knot x-wind translates to a 5-kt wind 10 degrees off runway heading, or 10-kts 8ish degrees of runway heading, and so on. Granted, eventually the number of degrees off runway heading would be so small that it could not be acurately measured and uncertainties involved with taking the actual measurements would make a safe landing/takeoff questionable. For instance, it is probably not possible to measure a forty-five knot wind accurately enough to decide the runway is safe to use. The winds would have only a 4 degree window to stay in (plus or minus 2 degrees of runway heading), and really how likely is this?

 

[flyguy93]

gannet,

You are absolutely correct!!!. So I do apologize for my previous post, I think I didn't interpret the problem correctly.

After rethinking, you can only determine the max x-wind component but not the head-wind component because like you said that will vary depending on the angle relative to the runway. I think the point they were trying to drive home is X-wind component is the limiting factor and that it is directly porportional to the CRFI.

Nevertheless I will talk to some people and see if they might be able to shed some light on the topic.

note.... it was a late last night and I wasn't thinking straight, pardon my instincts. 😉