# Maximum Theoretical Range RNAV

This is one of the easier topics on both the Radio Navigation and Communications syllabus. Most questions require using the formula:

$M = 1.23 (\sqrt{h_1} + \sqrt{h_2})$

where $M$ is the MTRMTR —Maximum Theoretical Range in nautical miles, $h_1$ is height of the aircraft in feet, and $h_2$ is the height of the beacon in feet.

Mistakes that be made include:

**Getting the input data incorrect.**The heights are in feet, so watch out for data given in metres.**Getting the formula wrong.**For example, adding the heights together then doing the square root.**Rearranging the formula incorrectly.**The reverse formula is: $h_1 = \Big(\frac{M}{1.23} - \sqrt{h_2}\Big)^2$.**Getting the output units incorrect**. The MTRMTR —Maximum Theoretical Range is in nautical miles, so watch for the examiner giving answers in kilometres.

The range above is exceedable in the case of **super refraction**, where atmospheric conditions benf the signal back towards the earth.

## Get instant access to
815
Radio Navigation
exam questions.

Start your free trial today.

Prefer multiple choice questions

What is the maximum range that an aircraft at FL195 can contact a beacon at 583 ft?

Question
0

Question
1