A central composite design with 4 factors in 2 blocks. These data
comprise a `coded.data`

object.

`heli`

A data frame with 30 observations on the following 7 variables. Each observation reflects the results of 10 replicated flights under the same experimental conditions.

`block`

a factor with levels

`1`

`2`

. Block 1 consists of 18 observations (a full factorial plus two center points). Block 2 consists of 12 observations -- 8 axis points and 4 center points.`x1`

a numeric vector. Coded wing area,

`x1 ~ (A - 12.4)/.6`

`x2`

a numeric vector. Coded length ratio,

`x2 ~ (R - 2.52)/.26`

`x3`

a numeric vector. Coded body width,

`x3 ~ (W - 1.25)/.25`

`x4`

a numeric vector. Coded body length,

`x4 ~ (L - 2)/.5`

`ave`

a numeric vector. Average flight time, in csec.

`logSD`

a numeric vector. 100*log(SD of times).