Just one thing to add. I was taught the same method as Dublinpilot (but using 10 nm either side of track, not 5). I saw mention a few years ago that when calculating MSA in mountainous areas, you should use the highest elevation within 10 nm of your track plus at least 2,000 feet.

I appreciate that this is entirely irrelevant over the Suffolk alps, but for those venturing into Wales, Cumbria or the Highlands it may be very relevant.

P

People appear to be mixing MEA (Minimum Enroute Altitude) up with MSA (meaning Minimum Safe Altitude, not Minimum Sector Altitude).

Minimum Safe Altitude, relating to VFR, is something like

Except when necessary for takeoff or landing, no person may operate an aircraft below the following altitudes:

(a) Anywhere. An altitude allowing, if a power unit fails, an emergency landing without undue hazard to persons or property on the surface.

(b) Over congested areas. Over any congested area of a city, town, or settlement, or over any open air assembly of persons, an altitude of 1,000 feet above the highest obstacle within a horizontal radius of 2,000 feet of the aircraft.

(c) Over other than congested areas. An altitude of 500 feet above the surface, except over open water or sparsely populated areas. In those cases, the aircraft may not be operated closer than 500 feet to any person, vessel, vehicle, or structure.

Minimum Enroute Altitude, which is includes the concept of a 'designated mountainous area' is an IFR thing, but one should certainly have this calculation in mind when flying VFR X-country, maybe flying at or above this altitude would mean you were obeying (a) above, and you would impress an examiner with your airmanship. I also thought mountainous areas were a bit higher than found in the UK, if talking about flying over them.

I think that's because the US has a rather more rigorous set of definitions for minimum altitudes, with MEAs, MRAs, MOCAs, MORAs etc. The "1000 ft above the highest obstacle within 5 nm" that comes from the UK's Rule 29 doesn't really have an equivalent label.

bookworm, Student~C150~Ipswich is a student pilot, we are talking VFR here.

and he also seems to be based in the UK, so is likely to need to know the UK situation, not the US rule that you quote.

The point is that there's a difference in the labelling: 91.119, which you quote (and incidentally applies to both VFR and IFR), has an equivalent in the UK, Rule 5. But the altitudes described in Rule 5 are not termed Minimum Safe Altitudes in the legislation, and are not usually referred to as such by UK pilots.

Thus in the UK, Minimum Safe Altitude is open to interpretation -- it's not something that can be "mixed up".

Well spotted bookworm! I did indeed quote from a FAR. As you correctly point out, "Minimum Safe Altitude" is not defined in the UK for VFR flight, and is open to interpretation. In these cases I find it useful to see how others do it, and hopefully the interpretation I posted is something like what Student~C150~Ipswich is looking for to answer his question - which was what is 'Minimum Safe Altitude'

Rule 29 which you cited is not really open to intepretation, it clearly doesn't apply to VFR flight. In my opinion it is there purely there to guarantee some degree of obstacle clearence when you are in the clouds. When VFR cross country your obstacle clearance is assured by visual means. Sometimes I have been VFR 100ft AGL in designated mountainous areas (real ones) and felt very 'safe'. Other times I've been 5000ft AGL and having to constantly search for places to land, and these have been few and far between.

Talking of learning from others. The UK has a 'glide clear' regulation which doesn't exist in the FAA rulebook. It would be churlish of me to say 'this UK rule doesn't apply to me' when I am flying above US cities. Knowing the 'UK situation' makes me a safer pilot, I believe.

I agree, though it is Rule 29 minimum altitudes that UK pilots regularly refer to as "MSA". You also make a good point regarding the difference between legal minima and the practical interpretation of safe.

The attached paragraph comes from the CAA Chief Flight Examiner and was promulgated to the Industry in Training Com 1/2004
http://www.caa.co.uk/docs/33/1_2004.PDF

1. VFR OPERATION AT MINIMUM LEVEL
When teaching Navigation, it is reasonable to teach students to plan a minimum altitude for each VFR leg that ensures compliance with Rule 5 (Rules of the Air Regulations 1996) and NOTAMS; if the cloud base lowers forcing the pilot to descend from his cruising level towards this planned minimum altitude in order to remain in VMC, he now has a yardstick to help him decide when to turn back. If the weather appears to be deteriorating further he should turn away (early) because on his plan, further descent on this track is unlikely to be an option. The problem is that FIs are calling this minimum altitude “MSA” or “Safety Altitude”. This is not acceptable; MSA and Safety Altitude are IFR safety minima. It is essential that FIs teach the correct meaning of these terms, how they are calculated, and avoid confusion with any VFR minimum altitude.

Whopity,
Cast your eye up to my post referencing Safety Sense 5 and have a read. This just goes to show that the CAA is populated by a bunch of people with much opinions and little correlation of terminology.

FWIW and personally, I don't think it pays to be overly retentive about the use of the wording MSA. It is clear, it says what it is and people know what it means. Getting caught up in purely symantec difficulties is just confusing everybody.

Perhaps Caa should create a new term " Minimum cruise altitude".

I always taught 10nm either side of track, highest hill plus 300 feet, plus 500 feet or highest structure above that, plus 500 feet to determine a minimum exceptable cruise altitude should the cloud base drop. Also use this as a go/no go on cloud base forecast.

Draw three parallel lines onto a sheet of acetate, each 10nm apart and use as a overlay when flight planning.

Using the MEF can also be a bit restrictive should there be a high obstruction in the "corner of the box".