Hello GA ppl,
A while ago I posted on another popular forum a list of percentages of 'flyable' metars reported by EGLL per month. This being a more techy forum I thought I would post in more details and nerdy charts. Please keep in mind I'm still a very low hour ppl student (7hrs), learning at denham, so I'm quite restricted to the type of weather I can fly in!
During this exercise a 'flyable metar' is considered to be:
And here are the results:
Chart 1, the total percentage of flyable metars over 5 years (2008-2012) in each month
Chart 2, Same exercise applied to 2012 only and compared to the longer term 5 year one
Chart 3, Same 5 year exercise applied to a different airport (Luqa, Malta) and compared to EGLL
Chart 4, Same exercise applied to Jan and Feb 2013 and compared to Jan and Feb long 5 year term
For all the other geeks, these reports where produced by downloading metars from http://www.ogimet.com/metars.phtml.en then using a java libary called jWeather to parse the metar strings. This library was riddled with bugs... took me a while to sort some of them out. Some small number of the downloaded metars were also invalid ( such as having SCT with no alt. etc...) these were removed when the parser found the error. Each report was then hacked together using a custom script in Scala.
Let me know what you think. Now back to study navigation... :)
Interesting analysis but of course completely driven by being a low hour VFR pilot. IFR, it would be more like 99%.
IFR, it would be more like 99%.
Only if you fly one of these
or in general something with
I think the VFR analysis is good, for people who fly legit VFR, not "UK-style VFR when nobody can see you".
It does also depend on the leg distance. Obviously, on a given day, the chance of flying a 50nm leg during a lull in the wx is much better than the chance of flying a 700nm leg across Europe and a number of weather systems, any of which can throw in a spanner.
Very interesting! I do wonder what the comparison would be for Biggin Hill between your VFR conditions, and a 400ft cloudbase, 1800m vis and crosswinds less than 20knots (what I fly to with my IMCr in a TB10).
It would be good to play around with this - would you be able to send me the code, or post it on github or similar?
Only if you fly one of these
On the basis of the METAR, I don't think 99% is far off. I'd be interested to see the stats for sub-Cat-1 wx.
Interesting results. Given the limits I'm surprised the winter percentage is as high as it is. If you add a min freezing level of MSA + 1000' to the IMCr limits then the percentage is going to get usefully high. Some flights might be uncomfortable, but you would probably get there. With an IR it could get to 95%+ depending on aircraft equipment (assuming GA aircraft).
The fact is that southern UK and nearby continent has relatively benign instrument weather.
Peter I disagree. I have found a very high despatch rate (legal I should add) with a deiced aircraft that can go to FL250.
Of course I may just have been lucky.
Interesting.
I've been trying for a while to ascertain exactly what my personal minima are (on my IMCr). I never got round to establishing it while I was VFR-only (which didn't last long). I always seem to be a 'see on the day' kind of bloke with no real hard and fast rules.
If I had to try and pin it down, I guess it would be (for launch at EGLM, assuming I'm going somewhere towered with an ILS):
No cloud below 800ft, nothing BKN or OVC below 1000ft (EGLM and destination).
Surface wind not too fussy, as EGLM has 3 runways. Anything more than 25-30kts would get me thinking.
Vis - not fussed on the numbers but no FG or BR.
Precipitation - fine as long as not heavy.
No frontal weather on the route.
Then finally, the combination of freezing level and cloud tops would have to allow either a quick-ish climb to VMC on top or a cruise in IMC with no risk of ice. Ceiling on the TB10 is (apparently, not tried) 13,000ft.
I'd be interested to set this as 'flyable' and see what a data analysis like yours kicked out.
I fly to the minima on the approach assuming I have fuel to go elsewhere if I need to. Deiced aircraft helps of course. I don't understand setting personal minima well above the approach minima. You have either been trained to get to 200ft or not. If not, you shouldn't be flying to 400ft or even 800ft.
Taking the minima to 200ft makes what difference exactly?
If it is about not wanting to be diverted I understand. If it is about safety, I don't.
Sorry Jason, that wasn't what I meant. I was talking more about launch minima at the home airfield.
My minima for instrument approaches are my legal minima.
I don't have a de-iced aircraft, nor do I have an IR. I fly only for pleasure.
