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IFR Departure Minimums.

Old 28th Jun 2017, 13:15
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IFR Departure Minimums.

Not being rated doesn't help.....

I've seen closed airports still launching guys into the murk, but arrivals are being sent in circles or elsewhere.

Is the IFR departure minima that low?
I ask as I have an ME-NVFR, and we launch on instruments anyway.

Is it that different?

Cheers
Jas
jas24zzk is offline  
Old 28th Jun 2017, 14:07
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Take off minima are usually no lower than 300 ft ceiling and 2000 m visibility but these can be reduced for qualifying aeroplanes.

If in a multi, the engine failure case must be considered such that the weather must permit a return for landing or the aeroplane must have fuel and performance to fly somewhere else and land.

In the first case, the take off minima is the approach minima (IAL or visual) at the DEP AD, which would usually be greater than 300 ft ceiling and 2000 m visibility. In the second case, the take off minima at the DEP AD is 300 ft and 2000 m (or lower for the qualifying aeroplanes).

If you've seen aeroplanes departing into weather that does not permit a landing, then either:

It's a single and the weather is at least 300 ft ceiling and 2000 m visibility or
It's a multi and the plan is to land at a different AD should an engine fail.

The reason 300 ft ceiling and 2000 m visibility is required even if proceeding elsewhere after engine failure is so the take off can be conducted safely. Room below the cloud and some sort of forward visibility is required to manoeuvre for a landing following an engine failure. The larger aeroplanes must meet performance, depending on jet/prop - number of crew, RWY lighting and equipment requirements to reduce the take off minima below 300 ft and 2000 m.
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Old 28th Jun 2017, 16:42
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JG3
 
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My IFR instructor taught me if you can't land in it, don't takeoff in it (referring to the minimas).

Using the example above if the takeoff minima is 200ft and 2km vis, but the only instrument approach is the RNAV which has a minima of 500ft and cloud is OVC003, I wouldn't takeoff until the cloud will allow an instrument approach at the departure aerodrome, or another local aerodrome.

I understand that this method most likely would not be appropriate for charters, freight, RPT etc.
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Old 28th Jun 2017, 17:42
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For 'qualifying aircraft' .. (eg, jet, multicrew, trubo-prop with autofeather etc), IFR take-off minima is 550 meters vis and 0 ceiling but in the event of an engine failure and you can't return to the departure aerodrome to land because it's below approach and landing minima, then you need to assure that your aircraft has the performance to meet terrain clearances and the fuel to proceed to a suitable airfield. You need high intensity runway lights and runway centerline lights for this, otherwise it's 800 meters vis and 0 ceiling.

In the US, we can take off with an RVR of 600 feet (182 meters), but need RVR reports at threshold, midfield, and end of the runway, and the runway centerline and edge lighting as well.
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Old 28th Jun 2017, 21:46
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We can take off with a zero foot cloud base (fog) and 350m visibility. Provided we have information for RVR from the three transmissometers.

We also have the capability of an autoland to return in a critical situation and the runway is suitable, or the required equipment for a takeoff alternate within 60 mins as per route distance limitations.

I'd think very carefully before launching in your average piston twin with a 300ft base and 2000m visibility.
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Old 29th Jun 2017, 02:36
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Airport/Aircraft dependant. Published on the back of the Jepp Airport Info chart. Low-vis ops....

Melbourne will let you go down to RVR 125m all zones. Best Sydney can do is RVR 350m

Clear as mud?
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Old 29th Jun 2017, 09:25
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Thanx for that guys.
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Old 3rd Jul 2017, 08:03
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Using the example above if the takeoff minima is 200ft and 2km vis, but the only instrument approach is the RNAV which has a minima of 500ft and cloud is OVC003, I wouldn't takeoff until the cloud will allow an instrument approach at the departure aerodrome, or another local aerodrome.
Sounds great in theory. But let's look at say YPDN, a common place for a piston twin to operate. And let's take a pretty descent SEROC of 250fpm. The lowest minima is the ILS (290ft), great we only have to wait for the ceiling to raise 90ft. But the approach starts at 3000ft, so that would take you 12 mins to climb, which 12 mins ~100kts means you need 20nm to climb in. Not too bad as the approach starts 8.5nm away and if you took off rwy 29 as well you can add some track miles pretty easily on the way out there but it will take you 7 minutes to get to the MSA. Although that doesnt take into account loss of performance during turns. Now obviously you can use the MVA and while you are there get ATC to vector you onto the ILS at a closer location, but it's still pretty fu ed.

I'd prefer the DGA, stay within 3nm (the closest step) and only need to climb to 700ft, that will take you 3 mins, which is 5nm of tracking. Probably add 50ft on to that to provide you a bit of buffer and 2.4km vis so you can do the approach. So now we are looking at 750ft/2.4km vis.

BUT to do that, you need to think about how you will manoeuvre to stay within the 3nm boundary and the sector. So it's a bit more complicated than "whats the approach MDA"? And well worth a serious think about in the flight planning stage.
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