about wake turbulence separation

[mxwbuaa]

Hey, guys, in icao doc 4444 (15ed), item 8.7.3.2 says: The radar separation minimum in 8.7.3.1 may, if so prescribed by the appropriate ATS authority, be reduced, but not below:
b) 4.6 km (2.5 NM) between succeeding aircraft which are established on the same final approach track within 18.5 km (10 NM) of the runway end. A reduced separation minimum of 4.6 km (2.5 NM) may be applied, provided:
…….
v) distance-based wake turbulence separation minima in 8.7.3.4, or as may be prescribed by the appropriate ATS authority (e.g. for specific aircraft types), do not apply;
.....
and 8.7.3.4 specifies the distance based wake separation between some aircraft categories.
What does it mean by “do not apply” ? does it mean the reduced separation only apply to the aircraft categories combinations not include in 8.7.3.4, such as heavy behind light?
By the way, in 8.7.3.4 .1 , the situations in which the wake separations apply are pointed out one of which is :
b) both aircraft are using the same runway, or parallel runways separated by less than 760 m (2 500 ft); what does it mean? Does the separation between an A/C departing and an AC landing on the same runway also fit for this rule?

[Tarq57]

POST 2 (just in case)


v) distance-based wake turbulence separation minima in 8.7.3.4, or as may be prescribed by the appropriate ATS authority (e.g. for specific aircraft types), do not apply;
Not that well written, is it?
It means you have to apply the wake turbulence separation, if required, or where not required and approval is given to use 2.5 miles, you may use 2.5 miles.

As for the parallel runways, I'll leave that for someone who knows. I suspect that if the rwys are less than 760M apart, they are to be treated as one rwy for separation purposes.

[mxwbuaa]

hi， does you mean that the wake turbulence may not be enforced? in my opioion, the wake turbulence separation must always be enforced between the aircraft categories listed in item 8.7.3.4. am i wrong?

[Tarq57]

No, quite the opposite. Any wake turbulence separation must be enforced, unless the pilot reports visually able to follow another aircraft.

(That's why I thought it could be worded better.)

Where there is no requirement for a wake turbulence spacing, (eg medium following light) the space may be reduced to 2.5 miles, where 2.5 miles is approved for your unit and equipment.

So your opinion is the correct one.

[mxwbuaa]

oh，that sentence is an excerpt directly from icao doc 4444. it is certainly correct.

[Crazy Voyager]

Both the senctence and Tarw57 are right (as I read it), they say the same but in different words.

[Tarq57]

Perhaps I should have written "Your interpretation is correct".