A nagging question before my GST... [Archive]

AJ1990

7th Jun 2011, 20:24

I had my first attempt at the GST dashed last week by terrible visibility for my navigation. In the route given to me however, there was one section which seemed a tad nasty. I have my test tomorrow but want to clear my head of this nagging question.

My first leg was from Clacton to Sevenoaks, over Sevenoaks my MSA was 2400ft due to a particularly large obstruction on top of a particularly large hill. According to my chart I'm in class A from 2500' in this area. Am I right in believing that I only had a 100ft corridor between my MSA and busting controlled airspace? My examiner told me I wasn't allowed below my MSA even though legally I was allowed to. My intended height was 2450ft amsl but I was very reluctant about having to do so. Was this just a route to seriously test my ability or am I missing something here? I haven't had the opportunity to talk to my instructor about it but I feel like I'm missing something. Thanks

stevelup

7th Jun 2011, 20:41

Why don't you route around the obstruction?

FlyingForFun

7th Jun 2011, 20:46

My examiner told me I wasn't allowed below my MSA even though legally I was allowed toI find that rather bizarre, I have to admit.

As a CPL instructor, I find a fair proportion of my students don't understand MSAs as they relate to VFR flight. For your examiner to be doing anything other than encouraging you to know the rules and exploit them to your benefit seems a bit strange to me, but might help explain why so many of my students believe, incorrectly, that they can't fly below MSA!

However, if that's what he asked you to do, then you either have to fly at 2400' (which is very common under the TMA, even without MSA issues, so keep a very good lookout), or route around the obstacle. I would not recommend flying at 2450' - it is generally accepted that you need to be 100' below airspace, although I don't believe that's written down anywhere. But there is nothing wrong with flying at your MSA.

Good luck!

FFF
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Conventional Gear

7th Jun 2011, 20:46

I was taught when VFR the MSA was calculated for the scenario where one inadvertently flew into cloud.

I certainly was never told I 'had' to fly it as a minimum whilst still VFR and didn't during my PPL GST.

If you are VFR and there is a hill with an obstruction, you are not about to fly into it are you?

Practically every VFR flight I do requires flight under airspace where flight above/at MSA wouldn't be legal (by my calculation method). I can't see you can be held to it in the test.

If I'm totally wrong I'm more than happy to be corrected by an FI, CFI or Examiner.

24Carrot

7th Jun 2011, 20:49

Just answering quickly, as your GST is tomorrow.

That MSA requirement sounds odd. MSA is important if you are flying IMC, and can't see things till you hit them, but a skills test is in VMC, so you can see and avoid.

I seem to recall a mast between Sevenoaks and Brands Hatch, is this what you mean? It is easy enough to see and avoid. I passed near there at around 2200 ft recently without feeling in any danger of hitting the mast. I did pay attention to the Biggin ATZ, the Gatwick CTA and the LTMA 2500 though.

One more tip: if there is a North or South wind over the hills watch your height very carefully.

AJ1990

7th Jun 2011, 21:00

This is what really frustrated me at the time. I knew I could legally make my life a hundred times easier by giving myself a couple of 100' margin but the examiner had explicitly told me I wasn't allowed below my MSA. I would have been happy to fly my MSA if nothing had been said but was worried if one momentary blip took me below it. At least I can't be given the same route tomorrow so it could be worse I guess. Lucky i couldn't go ahead with it looking back. Blessing in disguise and all that.

Genghis the Engineer

7th Jun 2011, 21:08

Surely instructors, and examiners, should encourage students to think for themselves?

Mind you, I've also flown with my share of such who didn't either, and far too many who think that applying substantial extra safety factors beyond regulations is essential and will try to fail you if you don't.

VFR, 500ft rule applies - MSA is an IFR concept - albeit a useful one to simplify flight planning VFR.

My opinion? Make sure you can see it, stay at-least a mile away from the obstacle, and allow yourself a few hundred feet below the airspace. If the examiner has a problem with that, ask him to show you the rule which prohibits flying like that, and if he still fails you, report him to the CAA. Which won't happen - pretty much anybody will see sense if presented with the regulations.

G

AJ1990

7th Jun 2011, 21:15

Seeing as I have the same examiner tomorrow, should I make a point of bringing this up with my instructor before I take the test? Rubbing up my examiner the wrong way isn't what I really intended on doing but I'm in the right here. I don't want to make my life harder than it already is when I don't need to.

I seem to recall a mast between Sevenoaks and Brands Hatch, is this what you mean?

That's the one - it would have made a very handy visual reference if nothing else ;)

FleetFlyer

7th Jun 2011, 21:32

If you're still reading this on the 7th, why aren't you in bed yet!?

Seriously though, just talk it through with your instructor. Routing around (I would go for several miles clearance in oder to mitigate navigation errors) and seeing and avoiding is the way any sensible pilot would do it in real life.
Giving yourself 50' below controlled airspace is a recipe for cock up.

Your instructor should be open to reasoned debate on this so if he instists on you flying the same way then at least you'll know why. With respect, it does seem likely that you may be misinterpreting what he is driving at with his MSA.

Edit: Thinking about it, he is probably not asking you to fly between MSA and controlled airspace, simply to be aware of what the MSA and local class D is so that should you find yourself in IMC, you can remain clear of obstacles and infringements.

Best of luck,
FF

BackPacker

7th Jun 2011, 21:34

VFR flight would not be possible in a lot of places if there was a rule that requires you to stay above the MSA. About a third of the Netherlands lies underneath the Schiphol TMA which is class A from 1500' upwards. The MSA is between 1800' and 2300', depending on the exact location due to a few well known tall masts but apart from those masts there's nothing to bump into at 1000'. So we all fly at roughy that altitude with no problem whatsoever.

What you should NOT do is take the grid MSA (the number that's printed on your chart every 1/2 degree of lat/long) as your flight MSA because that's going to restrict you severely. Instead draw your route, take a reasonable lateral safety margin (5 miles or so, depending on your expected navigational performance) and calculate your MSA based on the large objects or high ground you find within that safety margin.

That usually solves any routing/MSA problem you have. And if there is indeed a large obstacle in your way, you now know it's there and can re-plan accordingly. Or use it as a waypoint: If I know I'm going to encounter a tall mast or something during my flight which is a serious safety hazard which cannot be avoided, I want that to be in my plog so that I'm looking out for it.

(I often use the Hilversum TV tower as a waypoint. It's a very conspicous landmark even in low visibility. It's also 673' tall in an area where my planned altitude is normally 1000' or so.)

Conventional Gear

7th Jun 2011, 21:46

I would just chill a bit before your test and do your best to fly it like any other flight.

I can't really figure it other than it might have been a hint that the planning was flawed or not to the examiner's liking.

I did once have an instructor who questioned why I had calculated MSA and wasn't flying it. I didn't bother to explain and chose never to fly with him again. :ugh:

However you look at it, there is no legal requirement to fly at or above a calculated MSA during a VFR flight in the UK. Take one look at the Eastern Stansted transponder mandatory zone, then figure how far below MSA (by any of the popular calculation methods) you would have to be to fly in it.

It was made more than clear to me that the reason to calculate MSA for VFR flights was insurance against being stuck in cloud. If the 180 degree turn didn't work, climb to MSA whilst talking to whoever controls the airspace you just busted and live to tell the tale. OK more seriously one would look for routes where it wouldn't be an issue and be very aware of where it might be, but you get the concept.

BackPacker

7th Jun 2011, 21:50

Oh, to add (can't edit my post now for technical reasons): The Jeppesen VFR charts print the grid MSA directly on the chart for each 1/2 degree lat/long, while the UK CAA charts print the highest known elevation. To which you need to add 1000' to get the MSA.

Genghis the Engineer

7th Jun 2011, 22:21

Gertrude the Wombat

7th Jun 2011, 22:58

It was made more than clear to me that the reason to calculate MSA for VFR flights was insurance against being stuck in cloud. If the 180 degree turn didn't work, climb to MSA whilst talking to whoever controls the airspace you just busted and live to tell the tale.
I can't help feeling that flying into a cloud whilst on a test might just be a fail.

flybymike

7th Jun 2011, 23:01

I think the CAA charts publish the highest known elevation or obstruction. Since obstructions below 300 feet agl are not necessarily known to the CAA, because they are not required to be lit, one should also take that additional 300 feet into account in one's calculations.

BEagle

8th Jun 2011, 06:55

flybymike, that old chestnut is incorrect. As stated in the 'Reference to Air Information' printed on the chart, CAA MEFs are 'based on information available concerning the highest known feature in each quadrangle, including terrain and obstacles and allowing for unknown features'.

For example, on the old Edition 33 (yes, I know it's out of date!), if you look at the MEF for the quadrangle which includes Chivenor, the highest elevation is 883 ft. Yet the MEF is '1.2', i.e. 1200 ft. But because someone might have sneakily put up a 299.99 ft obstacle on top of the 883 ft hill, the MEF is 883+300 = 1183, rounded up to 1200 ft.

There is no need for the'additional 300 ft' to be added to the MEF.

Redbird72

8th Jun 2011, 06:59

A bit late now, I know, but might the intention of this be for you to adjust your route to avoid the pinch? The route given to me for my test, if drawn direct, took me directly over a glider site. Part of the test was for me to notice this and adjust my route to make room around it. Could it be that your examiner is being heavy about the MSA to encourage you to plan your route so that you have more headroom?

Conventional Gear

8th Jun 2011, 07:44

Quote:
I can't help feeling that flying into a cloud whilst on a test might just be a fail.

Planned altitude - the altitude you intend to fly at to avoid terrain, obstacles and remain clear of controlled airspace

MSA - safety altitude to climb to if one inadvertently flew into IMC

One would rather hope that during a test a candidate would have more sense than risk flying at VFR minima and the possibility of inadvertently flying into cloud. ;)

dublinpilot

8th Jun 2011, 09:55

Why are we talking about the MEF figures printed on a chart?

The safety altitude is 5nm either side of the planned track, which might give this student a lot more room to meet his examiners request than the MEF figure on the chart.

It's probably too late now, but if it was me I'd discuss the examiners requirement with them, explaining that I recognised that his request left a very small window, and increased the potential for an airspace bust. I'd ask if he could allow me to fly below MSA on this leg, bearing in mind where the obstacles are that are causing this high safety altitude, and explain that if that isn't acceptable, then I'm using my judgement to reduce that risk by planning a longer route which had a lower safety altitude.

I can't see how the examiner could be anything but impressed that you had thought about the issue, and recognised the risk, and come up with a plan to mitigate the risk.

dp

AJ1990

8th Jun 2011, 11:06

It's probably too late now, but if it was me I'd discuss the examiners requirement with them, explaining that I recognised that his request left a very small window, and increased the potential for an airspace bust.

Thats how the situation came about - in the brief before the test when discussing my planned route I explained how I wanted to fly below my MSA to keep a safe distance from the controlled airspace. I didn't think it would be an issue until the examiner said they wanted me above my MSA. With a loud gulp and a monumental thought of :mad: in my head I just had to accept it and move on.

Test was cancelled today anyhow :(. With gusts up to 27 knots I couldn't really pursade myself to go up as much as I wanted to get this bloody thing done. Maybe next time...

stevelup

8th Jun 2011, 11:09

I still think you should just route well clear of the obstruction which will inherently give you a lower MSA.

Are you absolutely positive he wasn't trying to gently hint to you that the planned route was unsuitable without actually saying so?

Surely you have to plan your own route anyway? I thought the examiner just told you where you were going, not how to get there. That's certainly what happened on my skills test.

BackPacker

8th Jun 2011, 11:30

Why are we talking about the MEF figures printed on a chart?

Because if there's no airspace or cloud in the way, it's far easier to use the MEF+1000 feet or the printed MSA value (Jeppesen) as your flight MSA.

On a long x-country it's a lot of space to check 5nm either side of your track for any obstacle that might be lurking there.

Also, if you are positionally challenged (aka lost), particularly in bad visibility, you are far safer above the MEF+1000 feet or printed MSA figure, than above the MSA figure you calculated assuming you would be able to stay on track. Airspace issues aside of course.

AJ1990

8th Jun 2011, 11:35

That is completely possible but my issue was why I wasn't allowed below MSA. After spending two hours planning my nav, weight, fuel etc a change of route wasn't really on the cards. Giving it a wide berth would have been a solution looking back on it but at the time I had no reason to do so, it was only in the brief just before the flight that I was told. Thats why I wanted a pprune opinion on the subject because it really confused me at the time - I felt penalised for doing something I had been taught was perfectly acceptable.

Cusco

8th Jun 2011, 11:41

The answer shirley lies in the term MSA : Minimum Safe Altitude>

A stude taking a Flight exam like the PPL should not fly below the minimum safe altitude as by definition (whether you want to be pedantic or not) he will be flying into unsafe airspace.

Thus you either plan to go around the obstruction or you nail the altitude and don't drift up into CAS.

BackPacker

8th Jun 2011, 11:42

After spending two hours planning my nav, weight, fuel etc a change of route wasn't really on the cards.

Not really the best of attitudes in general.

If the plan is no good, throw it away and start again. Don't go flying on a bad plan, thinking (hoping) things will sort itself out once in the air.

But you haven't told us yet what you were using as your MSA. Were you using the grid MSA or did you calculate the MSA based on objects/high ground 5 nm either side of your route?

In the latter case I can well imagine that the examiner doesn't want to see you fly below the MSA. Heck, if you calculate the MSA that way and then fly below it, you actually come reasonably close to busting the low flying rules.

AJ1990

8th Jun 2011, 12:08

I've always used the 5NM off track technique to work out my MSAs. Using the grid MEF always seemed a bit excessive I thought when your MSA could be calculated at being alot higher for an object no where near you.

In retrospect avoiding the obstruction would have made my life an awful lot easier. We learn from our mistakes though so this seems like a good lesson for my next attempt and my future flying. I get the feeling this may have been the suggestion of the examiner. I've always planned my routes above MSA so this was the first time I was faced with the problem. From my point of view though MSAs weren't a legal requirement, the cloud base wasn't forcasted to be an issue so I didn't see the risk in flying just below MSA. I didn't feel like I was jeapodizing the safety of the flight when my intentions were to avoid an infringement. I know there's a difference between what is safe and what is legal but I felt as though the safety of the flight wasn't being compromised.

Thanks for all the advice though it's really appreciated. I'd still like to have a chat about this with my instructor though, it seems like a bit of a hazy area.

dublinpilot

8th Jun 2011, 12:27

Because if there's no airspace or cloud in the way, it's far easier to use the MEF+1000 feet or the printed MSA value (Jeppesen) as your flight MSA.

On a long x-country it's a lot of space to check 5nm either side of your track for any obstacle that might be lurking there.

Also, if you are positionally challenged (aka lost), particularly in bad visibility, you are far safer above the MEF+1000 feet or printed MSA figure, than above the MSA figure you calculated assuming you would be able to stay on track. Airspace issues aside of course.

BP,

I don't disagree that it's easier, but if it produces an answer that boxes this guy into a small corner, then he should look at the more detailed (but cumbersome) way. If that produces a much easier flight, then it's worth the effort!

But you haven't told us yet what you were using as your MSA. Were you using the grid MSA or did you calculate the MSA based on objects/high ground 5 nm either side of your route?

In the latter case I can well imagine that the examiner doesn't want to see you fly below the MSA. Heck, if you calculate the MSA that way and then fly below it, you actually come reasonably close to busting the low flying rules.

Unlikely! 1000ft above the highest obstacle within 5nm of track is going to ensure that you are 1000ft above everything. So long as they comply with the glide clear rule, they'll be ok at that.

Anyway, the examiners requirement is that they fly above that altitude, not at is, so keeping that safety altitude as low as possible, will give them a bigger window to work with.

stevelup

8th Jun 2011, 12:32

That particular obstacle is about 1400 feet AMSL so once you've added 1000ft to that, you're at 2400 - just 100 feet below the Class A.

The issue is not the calculating of the MSA (which has been done correctly), rather that there actually is no requirement to fly above the MSA when VFR.

I would still have gone around it though.... Logic suggests not planning to fly over a 1400ft obstacle when there is airspace at 2500ft. A small detour would save all this trouble.

It's all kind of a moot point anyway because you shouldn't fly the same route you already planned. I would expect the examiner to give you a different destination.

cavortingcheetah

8th Jun 2011, 12:53

You absolutely should have a chat about this with your instructor and he needs to clear this matter up for you. It is his responsibility to do that and if the matter has arisen already in a briefing with an examiner and has caused confusion then your trainer should have broached the matter with you, either then and there or later, and removed the grey areas. He should have enough empathy with you to realise that you're not a happy bunny. Since he has apparently neglected to do this you will have to bring the matter up but do not relent until you are 100% sure both in what he says and that he is correct in saying what he does. Get him to show you the writing in LASORS or wherever it may be concealed. At the next briefing, if the matter is raised again, do not hesitate to quote your instructor, in front of him, to the examiner and make quite sure that there are no ambiguities on the horizon.