[flyboy1963]

I just bought one of these slide rule style calculators after seeing a great AOPA forum about density altitude and mountain flying. (Okay, it's not really the season.)
The calculator requires some pretty accurate take-off distance numbers.
Does anyone have a good, simple, safe way to get take-off distance numbers? Angle of climb %?
I'm thinking golf range-finder, good old tape measure etc.
the other problem of course is finding an airport where one can get out near the runway to measure, stake, and then observe the true wheels-off point!
( a runway 'just' dusted with snow comes to mind!)

any tips or tricks?

 

[smiller]

There's a standard for the centerline stripes

In the U.S., most airports appear to follow the standard (it's in an FAA AC somewhere) when it comes to runway markings, lights, etc. It so happens that the standard for the centerline stripes is: stripe = 120', gap = 80'. Thus, from the beginning of one stripe to the beginning of the next stripe is exactly 200'.

How can you verify this without walking out onto the runway with measuring tape? Well, I fired up the free Google Earth program and used its measuring tape tool. I would zoom way in to airports of interest and then use that tool to measure the distance from one stripe to the next. Even the local mom and pop private airport followed this part of the standard for the centerline stripe on their paved runway.

Now, when taking off (or landing), it's easier if you have someone else in the airplane to count the stripes for you, and to estimate about where you lifted off (or touched down). "About 75% down the 5th stripe." From that you can figure out the total distance, or even fire up Google Earth again and use the little measuring tape tool from the end of the runway (or beginning of the first stripe if you like) to 75% down the 5th stripe.

At a towered field with multiple runways, you could possibly call up the tower and get permission to walk out onto the inactive runway if you really wanted to measure it. I routinely get permission from tower to walk across an inactive runway, and even once got permission to set up my camera and tripod on the numbers so I could get a nice shot down the runway! They might have actual measurement specs for their particular runways for you, however.

Not sure if that's accurate enough for your use but hope it helps!

P.S.: It's easier to count stripes if you use a wide runway and take-off/land to the right or left of the centerline stripe.

 

[flyboy1963]

measuring performance parameters

Hey, I'll have to try that idea! thanks!
.....sounds way better than painting a tripe on the side of my tire, and counting how many times it goes around, and around, and.......