View Full Version : Go/NoGO decisions
I recently had to face some difficult go/no-go decisions and was left wondering what criteria other pilots use. As for myself I'm settling on the following:
vis > 7km,
cloud > 1500' (agl or highest obstacle)
xwind < a/c demonstrated limit
no severe weather warnings (worse than -RA, thunderstoms, icing below 1500agl)
This applies to departure, enroute, destination (and for the return trip if applicable).
While some I've chosen because I've experience worse and am not keen on going through the same again (in particular vis and xwind), for the rest I'm simply following others advice. As you probably guessed this is strictly VFR but it would also be interesting to see how it changes once you have a IMC or IR rating.
Mak
Bluebeard2
8th Jul 2003, 03:24
I tend to have 2 'thresholds' for go/no-go. If the met fails to exceed the higher threshold, then I'll keep the flight local or stick to circuits.
My higher threshold is:
Vis: 7km
Cloud : 2000ft agl for the whole route
Wx : No CB or TS for the whole route, moderate rain only
X-wind : max. aircraft demonstrated x-wind limit (including gusts!)
My lower threshold is:
Vis: 6km
Cloud : 1500ft agl for the local area, with little likelihood of the base dropping
Wx : depends on how local I want to stay; unless CBs/TSs are guaranteed I'll normally take a trip to the airfield to take a look for myself.
X-wind : max. aircraft demonstrated x-wind limit (including gusts!)
I'm happier to play things by ear for the lower threshold as the official stats for the above are, for my home field, taken at Stansted a few miles away. The acid test is to go up and take a look, assuming its not absolutely awful - if its looking a bit dicey then I'll stick to the circuit and come back down sharpish.
Mak,
After a good many years military and civilian flying I stick to the old adage "if in doubt; then no doubt - don't go". Very easy to say, only trouble is each and every decision is equally difficult. I don't think it ever gets easier, although I think the numbers only tell half the story. Often you might be just legal to go with the vis/wx as given - but does that pressure you to actually go? it certainly shouldn't, and I tend to add a margin for the comfort of my pax.
deneb :ok:
bluskis
8th Jul 2003, 04:05
Not sure I would like icing level at 1500ft, and if viz is only 7km, how would you see and avoid the CBs.
Demo X wind is a bit marginal unless you are very familiar on type.
Do you actually mean any one of these would be a no go, because you could have some pretty nasty moments if all were present.
Why not 'work down' to your limits?
Fly when it's 9km and 1800' - see how you feel and make a note in the REMARKS section of your logbook. Then you'll start to build some structure to your previously gained experience.
Your logbook will then become meaningful reading pre-departure.
Also, consider stressors within the cockpit -
Wife / Kids on board
Friends first flight
Perceived difficult routing or new territory
Planned flight close to fuel endurance limit
...the list is endless but worth considering when adjusting your personal limits. In a quiet moment on an unflyable day have a think about problems created by and solutions for the above.
Notice - Understand - Think Ahead
m
FlyingForFun
8th Jul 2003, 16:33
Was deciding what to write in my reply, but found that others had beaten me to all the important points! But, to re-emphasise:
Deneb's advice - if it doubt, don't go - is the overriding single most important piece of advice.
Other than that, I don't think it's possible to give a definite answer. It will depend on all kinds of factors. How far are you flying? Is it a route you know well? Is there any high ground on your route? Are you flying towards the weather (which is good - you can always turn around and fly away from it if necessary) or away from it (bad - it could block of your return path)? Do you have pax? Are they likely to be demanding? How are you feeling? Are you current? Are you tired?
One other specific thing to pick up on from the details you describe: icing conditions aren't usually a concern for VFR pilots, but if light rain is forecast, they could be. I certainly wouldn't be flying in light rain in anything approaching 0 degrees, except in the circuit.
I'm not entirely convinced on M14P's idea of working down to your limits, because there are just too many variables to have once single limit to work down to. But it sounds like a good way of finding out roughly what you're capable of under certain specific circumstances.
It's probably also worth pointing out that there's nothing wrong with "going up to have a look", as long as the conditions are good enough to do a circuit. If you're not happy to leave the circuit, then don't - land straight away. If you're happy out of the circuit, then head off to the local area to see if the vis really is what the forecast says it is. Don't be afraid to turn back at any time, and don't get cut off from your home airfield until you're sure you're happy to continue.
FFF
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I know the feeling when you cancel and then you spend the rest of the day wondering whether or not it would have been alright afterall! I tend to take the weather forecast with apinch of salt for shortish (60nm) familiar flights. Instead, I call the destination and make sure they can see their hand outstretched, and then I take off, BUT, I plan and prepare for (before departure) a diversion, usually straight back home. I don;t set myself predetermined cloud limits etc, its more a case of if I don't like it, I wont hesitate to turn around.
Took off under cloud at 1500ft the other day, and as we progressed the cloud gradually lowered to 800ft.When I was sure that it wasn't just a couple of low lyingfluffy things, I did a VMC 180 and climbed back up and went home. No drama.
Deciding does get hard on a sunday evening when you are in France with friends and everyone has workl the next day!
FlyingForFun
8th Jul 2003, 16:54
Deciding does get hard on a sunday evening when you are in France with friends and everyone has workl the next day!That's when having enough spare cash to get home by other means comes in handy! Oh yes - and an understanding boss.....
FFF
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If you don't work down to your limits you will either cancel more trips than you 'need' to or blast off straight 'in at the deep end'
Why have a limit if you will actually be limiting yourself to a higher value?
Mak,
I am only a 250 hour IMCR pilot but I do fly about 200hrs/year presently, and I think (while your limits are perfectly wise) if you cancel a trip every time you aren't sure, you will never learn much, and also you will probably join the 95% or so of PPL holders who never make it even to their first license renewal.
You've got to have firm limits on certain things, e.g. cloudbase, CBs and xwind limits but much of the rest can be played by ear and you may just have to divert - NOT good if you have passengers who have arranged babysitters!!
To answer your other question, an IMC Rating will TRANSFORM your ability to do a flight but only subject to you having a) currency and b) a good enough plane. I fly at least once a week, right through the winter, and with just a PPL I would be routinely grounded for weeks or even months at a time. Most of the winter flights I have done (IFR) I would probably not have done - on the TAFs alone - with a PPL.
There will always be things which will stop you flying; the more money you spend on a plane the more removed they will be but there will always be something.
I won't go if there is forecast (or likely) icing below the MSA, and I would not do a visual approach of any sort in poor vis (e.g. heavy rain) if there is high terrain nearby. There are a few other things, and obviously runway length is one of them! I never fly with less than 2-3hrs fuel (no use planning an alternate just 20 miles away as a "weather" diversion!). As I've said, much depends on your currency and how well equipped your plane is; these become really important (and not easy to take care of unless you join a group or buy your own) when you look at post-IMCR flying.
Go for the IMCR, you will not regret it. But look at your flying budget first; no point in doing it if you can afford to fly only say 10 hours a year.
FlyingForFun
8th Jul 2003, 20:15
M14P,Why have a limit if you will actually be limiting yourself to a higher value?Exactly. That's why I don't want to create a limit for myself when I'm flying across high ground in an area I don't know, and then force myself to stick to that limit over the completely flat local area with good visual line features which I know like the back of my hand. (Does anyone actually know the back of their hand that well???) I prefer to have a rough idea of what I'm capable of, and then on any particular day I can make a decision, including a "go and have a look" decision if appropriate.
Nothing wrong with either method, it's just what works for each of us. Working down to a limit clearly works for you - and that's fine. :)
FFF
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Ah - but there you are smack in the middle of the experience gap. Without the knowledge of what is and what isn't flyable for you one is left making judgment decisions without anything to measure up against
m
FlyingForFun
8th Jul 2003, 20:49
Yes, possibly.
But maybe I should turn my statement from my previous post around the other way, and say that I don't want to create a limit for myself when I'm flying over the completely flat local area with good visual line features which I know like the back of my hand, and then force myself to stick to that limit across high ground in an area I don't know.
In addition to not setting over-restrictive limits on myself, my approach also doesn't allow me to have a false sense of security by using limits which are too low for the flight in question.
As for being in the middle of the experience gap, I'm well aware that I'm in that region where many accidents occur due to pilots having enough experience to be confident but not enough experience to justify that confidence. I always try to be cautious because of this - I've either stayed on the ground or turned back at least a half a dozen times in the last few months, when I maybe could have carried on but decided not to. If I had a couple of thousand hours more than I do, I may have been able to carry on knowing it was safe, or I may have turned back knowing that it wasn't safe to continue - but I don't have those hours, so I stay cautious. I can't see how my method of determining my minima is any different to yours in this respect - the individual pilot has to decide on the minima according to his experience in each case, and needs the maturity to be able to do so safely.
And why are the two of us the only ones involved in this debate? What do others do? Do you have a definite limit, that you reached either by working down to it gradually or by any other method? Or do you have a more general idea of what's flyable, and make a decision on the day? :)
FFF
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FFF - I didn't mean YOU are in the experience gap specifically (sorry for any misunderstanding) I meant a bit more generally. In fact, about 80% of the GA population are in the statistcally dodgy ground about which you speak (i.e. immediately post PPL, then 300-400 hours then 1000-1200 hours) so I am very keen on promoting specific methods to enhance the 'survivability' of that period (see other post about 'Close Shave').
It's a little pet hobby of mine - Single VFR Pilot CRM. I hope it can help others.
Good point - why ARE we the only ones discussing this? Maybe we're just too mouthy!!?
m
Are we talking about flying below the MSA (1000ft + the highest point 5nm either side of track on the current leg) if the visibility is good?
down&out
8th Jul 2003, 22:29
I agree with the sentiment generally posted here- set some general rules, but they will be based on destination, passengers, need to get back etc etc. If you want to lower your rules, try it out when you don't have to get somewhere so turning back is a not a concern.
However I must disagree with you IO540 on one thing:
Go for the IMCR, you will not regret it. But look at your flying budget first; no point in doing it if you can afford to fly only say 10 hours a year.
I do a little more than 10hrs - probably 20hrs pa, and got my IMC 5 years ago. True, I have only used it real IMC conditions occasionally since due to availability of appropriate a/c & often going abroad where it won’t work anyway. However, I learnt a great deal from doing it, it has improved my navigation by using the radio beacons and I am much happier that if the weather turns in on me on the way back I can get back. Now, if I had a nice fully kitted out a/c, with de-ice and the cash to run it lots, life would be different - but I am very pleased to have done my IMC and keep it current.
(Also a great benefit on long cross-channel runs when the horizon mushes into the sea & the only way to fly is on instruments despite 20k.)
MSA (or SSA or MEA for that matter) only applies if you are operating to instrument rules. In terms of legal compliance (although not necessarily airmanship) one only needs to satisfy Rule 5 and its sub parts when operating VFR
m
bluskis
9th Jul 2003, 00:02
Lots of posts talk about limits, which I tried to hint at in my previous should take into account the build up of problems as different aspects of weather and navigation combine.
Others have mentioned the legal limits of ratings. Others having alternative options.
Most importantly you should also take into account your recency, and as such your day to day or month to month 'limits' will change, both up and down.
It is sensible to know what is safe for you and what will result in near panic and the old feeling of better down wishing.....
But in my opinion this knowledge of your own ability depends on many variables, and assessing these is what you learned in learning to fly.
down&out
I agree with you to the extent that the skills learnt are very useful, and being able to do IFR en-route legally (usually VMC on top) is definitely worth having. However I don't think a very low hour pilot is going to have enough currency to do instrument approaches, and if the plane has the usual wrecked avionics?
And the basic instrument skills, plus VOR tracking, is something one can learn anyway in a few hours. After that, it's just a case of doing it from time to time.
But I won't knock this; I think anyone who wants to fly x/country in the UK should do the IMC-R, to avoid the constant disappointment which every PPL is familiar with.
M14P
Is an MSA really just an IFR concept? I see what you are getting at, but a PPL can legally fly down to 3000m horizontal vis, and would you want to push the limits down there? 3k-5k is IMC in all but name, very hard to navigate visually, no horizon, and there are plenty of tall towers around... and if your positional certainty is less than perfect, which with the constant discouragement of GPS usage it most certainly will be...?
I think every flight, VFR, should always be planned around the MSA. If the TAF cloudbase is below the MSA, and the TAF turns out correct, then you've got about 1000ft between the terrain and the cloudbase to squeeze yourself into - hasn't this been done quite a few times, UNsuccessfully?
Gertrude the Wombat
9th Jul 2003, 05:24
In East Anglia where I learnt to fly a plausible clouldbase rule is 2000', being 499' for the ground higher than the map plus 299' for the masts not shown on the map, that rounds up to 1000' then fly 1000' above that (yes I know you don't have to VFR).
The reason that turns out to be reasonable, such that I don't actually want to go flying with a lower cloudbase than that anyway, is that if the cloudbase is lower than that then round here is is usually no fun flying that day: save your money for a prettier trip.
However in BC next month I expect to be taught different rules - when you're taking off next to a mountain you can't fly higher than the terrain within 5nm; and if you're taking off from a little lake where you have to circle over the water a couple of times before you can clear the trees ...:D :D :D
FlyingForFun
9th Jul 2003, 16:05
I agree - MSA is very relevant to VFR flying, even though there's legally no such concept.
Personally, I'll quite happily to fly below the MSA in good viz. But if the viz starts getting bad, it's a different story, especially if the ground in front of me is rising, or there are masts or tall buildings ahead.
FFF
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540, FFF et al
Well, MSA is a great idea under IFR but if you are applying the rule properly then operating below the LTMA will be nearly impossible. If you are navigating visually then there should be nothing wrong with 'stepping up' your cruising level in order to remain 'safe' can be done over relatively smaller distances than a conventional MSA might be measured over. For instance, your route takes you over a tall TV mast but you have identified some features (a town or lake etc) either side of the obstacle which can be ID'd with great certainty - at that point, climb to your new safe cruising level and at the next one pop back down.
This way you will have a far greater appreciation of where your obstacles lie rather than simply correcting MEFs for that sector. By having this greater appreciation you will then be better placed to make your go/no-go decision by using these features and the weather conditions as 'gates'.
540 - I know what the legal VFR limits are but those limits will not absolve you (in a court of law or amongst your peers) if you cannot navigate VISUALLY under VFR conditions.
The (JAR-modified!) law says that I can do a circling approach in my Airbus in 3700m but I'm not convinced that it's actually possible on every 3.7k day!
One must be very careful to actually make go/no-go decisions rather than go/it'll-be-ok/no-go decisions which tend to lead to continuing flight into unsuitable conditions. That's why I advocate 'working down' to your limits. Start safe, then edge a little closer to the next stage. Always have your escape plan in mind. Personal limits are superior to the 'wet finger in the air' trick since they are tangible and preset. The gates, markers and the basis for decisions is already set.
Trust me - I've scared myself witless before!!!!
m
IO540
10th Jul 2003, 17:23
M14P
540 - I know what the legal VFR limits are but those limits will not absolve you (in a court of law or amongst your peers) if you cannot navigate VISUALLY under VFR conditions.
I've often wondered how the 3km min PPL vis is supposed to be reconciled with the nav skills that are actually taught in the PPL and which aren't at all suitable for that sort of vis...
I've never got a good answer to that, apart from something along the lines of "well you need the IMC Rating to actually fly anywhere, and then you have other nav methods available to you, so it doesn't really matter does it" :O
Well, what you are taught (or should be) is DR Nav - i.e. Holding a corrected heading for a time and ending up where you ought to be. That is somewhat different to Pilotage - navigating between 'known points by visual means'.
DR is great and is the very fabric of how we should navigate (whether flying on instruments or otherwise) since it teaches us to keep to a baseline (a heading) and from that resolve in a scientific manner what our actual drift is. Much along the same lines as decision making is gives us something to 'hang our hat on' - a foundation for all navigation be it on instruments or visually.
The only issue I have with DR - and moreover the vis limit for VFR - is that it is a HIGHLY theoretical exercise assuming no pesky airspace that might get you rerouted, good wind predicitons, perfect DIs and Compasses. The vis limit will be perfectly acceptable so long as you stay exactly on course, then, at the calculated time a quick peek over the side reveals your perfectly identifiable feature (because the 1/2 mil is SO good at depicting ground features, isn't it?). Should you be more than 1 and a little bit NM off course you will be unable to see your feature. Ah!
Take for example navigating around the London area to fly from say Fairoaks to Stapleford your route would be made up of very many little tiny DR legs (incorporating a signifcant percentage of climb and descent) on which you will be totally unable to assess drift and therefore be unable to correct susequent legs. The Proud And Traditionally VFR pilot will probably be reduced to making a series of 'Piloted' legs with a DR navlog used as a baseline heading and timing tool. When making your go/no-go decision would you be assessing the ramifications of navigating in this way? Also, is it any wonder that the vast majority of pilots end up knob twiddling with VORs etc?
At the risk of merging us with another thread, what safer way of navigating within the REAL WORLD of the UK VFR environment than planning a DR log, programming it all into a GPS (system powered and externally 'aerialed') and getting airborne with the route helpfully ticking away whilst we spend 2 seconds of heads down time alternately checking that the DTK (better than BRG) and TRK are the same or checking that the DI is aligned properly?
The above certainly finds its way into my decision process.
Also, whilst I think of it, any aircraft owner who has a 'wet' E2 type compass should seriously consider spending a couple of hundred quid on a deadbeat Vertical Card compass. That way a gyro failure (or badly adjusted latitude compensation nut) will not cause you the massive workload increase that it does with a dicky old backwards reading E2.
m