Vmc Descent
 

What Are The Conditions For A Vmc Descent?:)

VMC Descent
 

Hi there UK MATS part1 Chapter 3 page 3

VMC Climb and Descent

To avoid excessive delays to traffic when radar is not available, controllers may
authorise an aircraft to climb or descend in VMC provided:
a) essential traffic information is given;
b) the pilot of the aircraft climbing or descending agrees to maintain his own
separation from other aircraft;
c) it is during the hours of daylight;
d) the aircraft is flying in visual meteorological conditions;
e) the manoeuvre is restricted to Class D, E, F and G airspace at or below FL 100; and
f) the aircraft is not in CAS-T.
Hope this helps

Can somebody explain when a pilot needs a VMC Descent (Doc 4444, 12.3.3.2, t)? A few examples will greatly clarify it.

In a procedural environment it is very useful when you've run out of options and you have an aircraft who is ahead of and above another one eg aircraft at 5DME FL80 and another at 35DME FL70. If you have no deemed seperations the only option is to make the higher one wait or offer them a VMC descent to become number one (as long as the other one agrees). It can also save time when using departure seperations enabling an outbound to climb before they are procedurally separated from inbound or holding traffic.

Never experienced it in 12 years in ATC.

My guess would be, when aircraft are procedurally separated and want to change levels, instead of waiting for certain conditions to be met procedurally (i.e. deemers, distance on a radial, established on a procedure etc) they do a VMC climb/descent and expedite things that way.

Think of an aircraft holding overhead an airfield at 4000 feet and for some reason they can't make an approach.
There's another one at 5000 feet and they want to descend through and make an approach.
Something like that. But I've never done procedural approach so I'm only guessing...

It isn't allowed in Class A airspace I believe - that's if any is left in the UK.

We used to use it frequently at Aberdeen in the days before Radar. We were handling 300 plus IFR movements in 20 hrs. & it was often the only way to give any real expedition of traffic. We were faced with slow moving helicopters, DC3s, Herons, Navajos, Aztecs etc., both IFR & VFR, & it was an effective method of getting higher performance aircraft through the levels of the slower traffic, or ahead of it. Mind you, it was not fool proof. You can give as much traffic info as you like to affected aircraft, but it does not mean that the pilots are going to see, & separate themselves, from the conflicting traffic. In any case, I do not think that whoever envisioned it really meant it to be used as a matter of course in congested airspace!

Of course it's not hence why the initial reply quoted MATS 1 where it states that it's only allowed in class D,E,F and G subject to certain conditions.

Emergency descent
 

Did one once when the skipper requested an emergency descent with an aircraft below us..turned 90 degrees and off we went....

Yonks ago flying for Ba Highland Division , we used the VMC procedure regularly . Used the exact phraseology that VATCO quoted . Our Ops manual had recently changed forbidding us to '' Cancel IFR '' . If it was a good day and we wished to see Fingal's Cave , or The Old Man of Hoy . Then we'd used that procedure whilst still on an IFR flight plan in the FIR .
Moreover , in the days when Kirkwall only had a VOR app to the West ; and the Haar was in . We needed to have practiced those skills above because ....
Early am flt from Shetland LSI to Kirkwall KOI , if we went upstairs ..... We'd have to hit the KOI beacon , procedural join , then outbound to the East , procedure turn , inbound on the approach , descend BUT ONLY to Circling minima , NOT the VOR MDA .... then with the strong Easterly wind blowing in Haar conditions , circle to land on easterly Runway . All well and good , but took absolutely ages and Circling minima was above the normal Haar cloudbase . ..... G/A divert to ABZ ... No good .
If we flew visually from LSI to KOI , we'd be underneath the Haar at 500' AGL/AMSL ; saw a lighthouse with vertical black and white stripes on our right . And a lighthouse with horizontal black and white stripes on our left [ or was it the other way around ? ] then we were on track for a left base join on the easterly at KOI . Simples...
Hope that helps ,

rgds condor

As an example, we don't have a backup radar, and noone nearby have, so if it stops working, we work procedurally. Which we already do with traffic outside radar coverage.

Furthermore, our view from the tower is restricted to the north and south by mountains, which means tower separation is hard to achieve until aircraft are relatively close by.

So often asking if the pilot would like to request VMC climb after departure, saves us 5-10 minutes... otherwise we'll have to wait until we can see the traffic from the tower...

We're fortunate enough that 90 percent of the time, it's severe VMC... otherwise things take time..

Used it occasionally at Prestwick in the 90's with BAe College PA34's for climb & descent, as one of the instructors was ex ATC & knew what it was about !
Heard a story from Preston Centre many,many moons ago - probably apochryphal - but to me typifies the great Aer Lingus spirit of days gone by :
On Blue 1 west of Wallasey, Shamrock reports a Bealine in sight & requests climb maintaining VMC, which is approved. Back comes a snooty Bealine : "Shamrock, how do you know that the aircraft you can see is me ?" , Quick as a flash, Shamrock replies " Bealine, how do you know the aircraft going through your level is me ?" :D

Know it was used at LATCC 20+ years ago.Outbound from Humberside 2miles in trail of company a/c both heading to DOGGA requests a higher level 'can you see the company a/c ahead' (both F27s) - 'yes' off you go then.May not have been regular,but certainly safe and expeditious !

When PIK ATC took over from CAA in 1991(?) , RADAR services were somewhat depleted. Annie from KOI only knew approach procedural. Tim Timlett as ATC Manager. By 1992 RYR services commenced and radar was back and CAS removed.
The QFI was probably cygnet 66 (no.54 course)

Preston FIR ended January 1975.....?

@ parkfell
PK atc took over from NATS on 1/4/1993. Stu Mimmack was their first GM - Tim took over in 1994. Re Cygnet 66 , you are correct = JM & yes, Barton Hall closed in 1975. I was on a night shift in 1974 when the high level sector was transferred to West Drayton - I still have the Bluebell designator strip from the D Side, gifted to me by the Watch Manager :-)