Hi,

Question 4 page 3.34, the answer says we will require an alternate because the cloud is below the alternate minima. This is because we can not use the special alternate minima due to one of the GP indicator being unserviceable.

However on the Jepp chart for melbourne (20-9A) under the special alternate minima, along with the ILS approaches listed there are LOC DME RWY 27 and VOR RWY 34. As both of these would not require the need of a GP indicator would it be true that you could use 700' and 2.5km vis as the alternate minima?

Thanks
Ryan

Hi Ryan,

Alternate minima apply when you are planning your trip and trying to decide if the weather conditions at the destination are so bad that you need to carry extra fuel to get you to an alternate or not. The Special Alternate Minima are a less restrictive set of conditions available to aircraft with dual ILS capabilities. The argument is, with such poor conditions, the only way to get in under such poor conditions is off a 3-D approach (i.e. one with precise height guidance).

In Australia the ILS is the only approach that qualifies as 3-D (one day we might get WAAS but it's not here yet). So, since that ILS equipment is your only hope of getting in safely on such a grotty day, you had better have a second ILS available in case that first one fails.

If you don't have functioning dual ILS, the rule is you can't use the special alternate minima when deciding if you need an alternate. You are stuck using the more restrictive minima which will make it more likely you are actually carrying alternate fuel in the tanks.

Note , once you are actually flying the procedure then the S-I and circling minima on the chart are what apply to your approach. The alternate minima apply to fuel and flight planning.

Cheers,

Rich