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Old 27th Dec 2012, 14:49   #1 (permalink)
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Join Date: Dec 2012
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Flyable weather in each month

So I've recently starting my ppl training and I'm finding it quite frustrating when my lesson gets cancelled due to bad weather. So far I had 4 lessons cancelled and only managed to log 2 hours! It's been asked before, but It's hard to find out what percentage of my lessons will be cancelled. So here's what I did:

Got all EGLL metars (I train in Denham) for the last 5 years. Filtered out those that are before 08:00 and after 17:00, then found the percentage each month of 'flyable' metars. What I consider flyable for training in a 152 (I might be completely off on this, so pls correct me...) is
  • Wind less or equal to 15 kts
  • No reported gusts
  • Cloud base of 2500ft or more (FEW clouds ignored)
  • No weather conditions, i.e. rain, snow etc... (unless reported as light)
And the average results of how many 'flyable' metar from EGLL in any given month from 2008 till 2012 are:
Jan 47.56%
Feb 45.14%
Mar 54.86%
Apr 68.69%
May 69.87%
Jun 74.62%
Jul 74.10%
Aug 67.80%
Sep 67.93%
Oct 64.11%
Nov 47.05%
Dec 53.89%

What you guys think? Do the above figures seem realistic?
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Old 27th Dec 2012, 17:03   #2 (permalink)
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I've been flying for 30 years, and your figures tally with my observations over that time. Which is:

Flying weather is better in summer..

Use the time wisely when you can't fly and enjoy it.
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Old 27th Dec 2012, 17:07   #3 (permalink)
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Well done, geeky flier, I'm passing it on to my gliding club, and the British Gliding Association! Quite true November usually horrid, but are the Feb figures possibly skewed by fewer days?

And interesting too how often October turns out well, sure did better this year than the summer washout! a number of nine day gliding competitions this past summer ended up with only ONE cross country day out of nine possible!

But as you will be flying cross country with a fan, no need to relish thermals; far safer to fly above the cumulus, less bumpy and fewer gliders on a very good day.

Let us all know how you get on, and thanks for your excellent summary.
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Old 27th Dec 2012, 17:33   #4 (permalink)
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It's definitely better in the summer. But I could have told you that without you doing all the research..... In fact being serious for once, I find the best flying days are March through to the end of May in general.
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Old 27th Dec 2012, 17:34   #5 (permalink)
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Hi Geekflyer,

Very interesting stats :-)

Do you do requests ;-)

If so, could you pick a random month and see whether there is any truth in my myth that the weather is worse at the weekends, compared to weekdays.

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Old 27th Dec 2012, 18:12   #6 (permalink)
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And thats exactly the reason people go to the states and come back with a shiny new licence in 4 weeks.
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Old 27th Dec 2012, 18:41   #7 (permalink)

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Geek, can you run those stats for sat and sun when most people train, and it will show the problems of flight training in the uk.
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Old 27th Dec 2012, 18:42   #8 (permalink)
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Hi Geekyflyer,

why the restriction to 17:00? From (say) March to October you could theoretically have lessons which will end after that time, allowing you a wider time frame to have your lessons in. But don't get dispirited, weather is part of your learning, just persevere, you'll get there in the end......
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Old 27th Dec 2012, 18:43   #9 (permalink)
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Geekyflyer - what an interesting bit of research you've done there.

Couple of qualifiers one might add:
- Plenty of flying goes on after 1700 local in summertime, although admittedly less training.
- Instructors may be happy to fly in worse conditions than those formal criteria you mention, depending on the exercise they are working with you on.

If it helps, from a personal point of view, up until this year, I always worked on the basis that I would get a dispatch rate for a given booked day's flying of about 75% in summer and 50% in winter.

This was based on C152/172-type flying in VFR as a PPL with a couple hundred hours. With experience, I would fly to slightly different criteria to those you mention, now I have the experience (e.g. 2000' en route cloudbase and stronger winds).

This year however it has worked out about 40-50% during the summer and 25% or less during the autumn/winter. I now mainly fly tailwheels, which restricts my criteria back more towards those you mention, but it doesn't get away from the fact that 2012 has been a truly diabolical year for VFR flying.

Until it returns to a more agreeable pattern, it may be worth scanning the long-range weather forecast and simply taking a day off when you see a potentially good day appearing on the horizon.
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Old 27th Dec 2012, 18:46   #10 (permalink)
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PS. FWIW TPC at Denham do seem to have a slightly more cautious approach to weather conditions during training than other establishments around London.

Just a personal impression and not in a position to say whether they get it right or not.

Either way, providing you steer away from the odd instructor, definitely one of the better places you could possibly train, so you made a good choice.
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Old 27th Dec 2012, 23:00   #11 (permalink)
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Do the above figures seem realistic?
Sounds about right. I tell passengers that there's about a 1 in 2 chance of cancellation in summer, and 2 in 3 chance of cancellation in winter.

I've been trying to be deliberately a little pessimistic. Your figures suggest nearer 1 in 3 in summer, 1 in 2 in winter.

Your weather filter seems reasonable (adding a requirement for 8km visibility would knock out a few more days). However some days the weather can be good enough for some purposes but not others, so you can still have a lesson on something, but maybe not on the exercises that were next on your list. For example you can do a dual navigation exercise when it may be too windy for you to do the landing (I've certainly done IMCr lessons on days when I couldn't land the aircraft); and you can do circuits on days when the cloud base is too low for cross-country flying.

When you've got a licence and are making your own decisions it gets more difficult. For example gusts are rarely as bad as forecast (although they are sometimes!), so in particular when there are forecast gusts straight down the runway it's quite often actually flyable ... sometimes I can't tell without going to the airport and chatting to people who have already been flying that day.
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Old 28th Dec 2012, 00:38   #12 (permalink)
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Shiny new licence in 4 weeks !!!

Yes,but then the reality of operating in the UK weather without the facilities they would have been used to as the NORM in the USA.
Take the 'Instrument Rating' for example.
Hardly any PPL's ever manage to get one because there is little encouragement to do so from anyone.
In the USA it is considered a normal progression that helps all types of flying to intergrate and benefit from a vibrant industry.
You certainly do not have to have one,but it is certainly available (and affordable) for those who wish to make the effort.
It always strikes me that 'Europe' are very good at making regulations for light aircraft that cover operating American equipment:- Aircraft,Engines,avionics,and systems,yet has such a poor record of producing the eqivilent themselves.
The USA has a 'can do' attitude as opposed to our 'not here old boy'.
Private flying in the UK is the poor relation to commercial ops,rather than being part of an intergrated SERVICE that would benefit all aviation users.

Last edited by POBJOY; 28th Dec 2012 at 22:13.
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Old 28th Dec 2012, 09:07   #13 (permalink)
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Well said POBJOY
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Old 28th Dec 2012, 09:13   #14 (permalink)
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Flyable weather in each month

Oh dear..... I love the american attitude (can do) and hate the british (whats the point) but our government try to destroy our want to succeed as they rape us every which way they can even at the bottom.

I do however think that those of us who have succeeded in achieving a ppl must have the "can do" attitude but not every one of us can afford to continue training imcr or anything else due to the tight living we have here.

Back to original poster......

While training early stages you should only need a cloud base of anything over circuit height.... The problem is manoeuvres & nav/solo nav.

I personally prefer to fly in winter time.... Nice cold crisp stable air...... But we didn't get that this year well, not when i was off work!

Im finding it hard to get my hours in for renewal! I got 6 months and 7 hours to fly and i cant seem to get the money/work/weather balance right!

Good old uk weather! Id be off to oz if given the chance

Last edited by Pilot.Lyons; 28th Dec 2012 at 09:25.
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Old 28th Dec 2012, 09:40   #15 (permalink)
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My personal limits as an instructor taking students up was shall we say alot more robust.

15knts is a bit low for straight down the strip.

As for the gusts then again no problem depending on what your doing that day.

1500ft is fine again depending what you are doing. If there is a horizon you can see.

As for rain and other such local wx you just fly to somewhere that you can see the horizon.

When I was full time I only had about 10 days grounded due wx but we were quite lucky with the local micro climate.
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Old 28th Dec 2012, 10:50   #16 (permalink)
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Some of the posts here surely demonstrate that internet forums are the natural home of whiny little girls with barely enough initiative to get out of the front door.

There are flying schools up & down the country begging pilots to come & take an IMC course - all anyone has to do is walk in through the door, or pick up a phone & ask.

Anyone who says "I would take an IMC course but no-one's ever encouraged me to do so" needs a kick up the backside.
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Old 28th Dec 2012, 11:37   #17 (permalink)
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First of all I must say great posts geekypilot and pobjoy

Frequency of training has a lot to do with the SOPs of the school and the experience of the instructor. My instructor took Mad Jocks view that if there was any way to do an exercise of any kind we got airborne. We had only four cancellations in the 43 hours and 7 months it took me for my PPL. We did of course have the advantage of Scottish weather

Other factors are the type of aircraft used, and for the less experienced instructors, where they were trained. (Stand by for flak)

An IMC rating gives me an 80% dispatch rate at an airfield with minimal navaids. Unfortunately the cost of maintenence of IFR aircraft and the drift towards LAA/Light Sport/microlight type aircraft has meant that many more flights now are victims of the weather.

The majority of the sub group A flyers at my field are retired so they can usually just pop out on nice days. Those of us who have to work for a living and fit flying in to the odd day off need the better dispatch reliability of an IMC or IR otherwise we would hardly ever fly.


Last edited by dont overfil; 28th Dec 2012 at 11:42.
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Old 28th Dec 2012, 12:32   #18 (permalink)
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as requested, i did the weekend stats. Figures seem slightly better in some months and slightly worse in others. I think 5 years is too short to pick up any significant 'weekend' trend.

Mth AllDays WkEnd
Jan 47.56% 57.67%
Feb 45.14% 46.15%
Mar 54.86% 55.15%
Apr 68.69% 70.41%
May 69.87% 73.57%
Jun 74.62% 70.52%
Jul 74.10% 75.78%
Aug 67.80% 74.29%
Sep 67.93% 72.38%
Oct 64.11% 63.29%
Nov 47.05% 44.62%
Dec 53.89% 60.55%

What is interesting though is I ran the numbers again for 08:00 till 10:00 and for 14:00 till 16:00, and there is a 10-15% increased chance of better weather between 14-16. Now if i can figure out how to attach a chart in PPRuNe I can show this better...
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Old 28th Dec 2012, 13:30   #19 (permalink)
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I tried a similar exercise a few years but adopted a different approach. My definition of "flyable" was simply "did anything fly on that day?". This was based on statistics from my local gliding club (Booker, so not that far from Denham). The thinking behind this is there's generally glider pilots lurking on the airfield who will try to make the most of the day and so if presented with an opportunity to fly they usually will. Admittedly gliding training parameters are slightly different to that in the power world, which perhaps provides greater flexibility - a 1,000' cloud base isn't a problem if you're doing circut practice and snow showers often have very exciting updrafts that you can soar along and stay aloft without the need for more traditional thermals.

I don't have the statistics to hand but I do recall a few important points:
- You will always fly more if you look at using the conditions presented to you on the day rather than having fixed definitions of what's considered "good enough"
- You will always fly more if you look at the weather after you've arrived at the airfield rather than looking at the forecast to decide whether to travel to the airfield in the first place
- marginal conditions, when accompanied by an instructor, provide a greater range of learning opportunities than "nice" days
- Like fishing, you should have been here yesterday. Or tomorrow.
- There's seven days in the week. Two are weekends, therefore if you can only fly at weekends you've instantly limited yourself to 2/7 of the flyable days

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Old 28th Dec 2012, 13:37   #20 (permalink)
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Geekyflyer - the better afternoon weather is almost certainly due to mist/low cloudbase you see in the cooler months.

Worth noting this will be an issue for training from Denham, since they have to cross the Chiltern ridge to get to their training area to the NW. It's only a small topographic feature, but at this time of year is a real mist trap, especially to the NW side (in my experience....).

It can be very flyable to the SW of London, but very nasty indeed round the corner to the NW. This has happened several times in the past few weeks.

There is a theory this is not helped by the Didcot Power Station belching out huge amounts of water vapour.....it is interesting how Benson's and even Brize's TAF/METAR appear more pessimistic than Heathrow's and Farnborough's.

Is that due to the Chiltern ridge effect, Didcot, or the fact they have human forecasters on site who are able to take account of local knowledge??

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denham, metar, ppl, vfr, weather

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