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Old 5th Dec 2017, 20:09   #1 (permalink)
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Minimum Safety Altitude

I was checking a sudents plog today and noticed he had put an Minimum Safe Altitude of 2200 ft , and a planned altitude of 2000ft, i asked how he came to this figure, its MEF plus 1000 ft came the reply, seems he was told this by another instructor, not wishing to rock the boat at this point i let him go on his x/country, BUT , surely the Minimum Safe Altitude should be an altitude you come down to if forced by bad weather, so should be based on things like 500ft above the tallest mast on route, 500 + 300 on top of highest ground or 1000 ft above built up area etc. etc. not some random 1000ft above an MEA on some large box on the map, how do you calculate the Minimum Safe Altitude on a students plog?

Last edited by memories of px; 13th Dec 2017 at 07:17.
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Old 5th Dec 2017, 22:00   #2 (permalink)
 
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Firstly, what do all the TLAs mean?

The Minimum Sector Altitude (MSA) is the lowest altitude which may be used which will provide a minimum clearance of 300 m (1 000 ft) above all objects located in the area contained within a sector of a circle of 46 km (25 NM) radius centred on a radio aid to navigation. These are the segmented circles on the top of Jeppesen plates (an others).

The minimum en-route altitude (MEA) is the altitude for an en-route segment that provides adequate reception of relevant navigation facilities and ATS communications, complies with the airspace structure and provides the required obstacle clearance. I'm guessing that doesn't apply to our PPL student.

The Maximum Elevation Figure, and the Minimum Off-Route Altitude (which is what I think you've got MEA confused with), are the figures in the 1/2degree boxes on the charts. On the CAA VFR charts, they are the MEFs, which are the figures for the highest known object or highest terrain plus 300' in that box. On the Jeppesen IFR charts, they are MORAs, which *include* the safety factor of 1000' for terrain up to 5000', and 2000' for terrain over 5000' (or higher if national regulations require).

In the UK, Minimum Safe Altitude is a hang-over from days of old. Frustratingly, not defined legally anywhere! We all know what we think it ought to mean, right?

In EASAland, we have minimum flight altitudes. The 'operator' should define what these are, and how they shall be calculated. You may have one minima for VFR and another for IFR. In other words, what does it say in *your* school's NCO Ops Manual / training manual / flying order book?

Traditionally, "MSA" is the f**itimscared bolt-hole altitude that one should climb to if VMC is lost. It is NOT the minimum altitude that you can fly at VFR.

To be IFR (and in IMC below 3000'), one must be 1000' above the highest obstacle within 5nm at all times. So, during planning, an additional lateral margin is applied so that if you are reasonably off track, your bolt-hole altitude will still be IFR legal. Most schools/operators will define this margin as 10nm either side of track (and around the turning points). If your navigation aids are limited and position cannot be accurately known, then wider margins may be required - ie, a long leg between any viable fixes may see you drift significantly further than just 5nm off track, in which case you might use a cone of ever widening safety!

Usually, we get Plt Off Prune to scour his chart with a thumb either side of his track (10nm), picking out the tallest objects and highest ground en route. We then add 1300' to all the terrain and 1000' to any obstacles, and the highest figure will be the "Safety Altitude" (or whatever you want to call it).

In the case of your student adding 1000' to the VFR chart MEF, they're not too wrong... It's not a good idea at a planning stage though, as you could be a) pushing yourself in to cloud at one end of the box for a tall mast 30+nm away, and b) ignoring an obstacle 1nm away in the next box along! The MEF/MORA are better applied when thrown off course and a quick and dirty assessment is required.

Last edited by Dusty_B; 5th Dec 2017 at 22:22.
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Old 5th Dec 2017, 22:56   #3 (permalink)
 
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Surely MSA is only an IFR concept - remaining at least 1000ft above anything within 5nm at all times. It has no relevance VFR.

Of course the concept of a minimum safe altitude (note non-use of capital letters) is relevant in VFR ops, but beyond being legal, it should be about a rational judgement about always being able to handle an engine failure, not bump into anything, and being unlikely to inadvertently enter controlled airspace. What is sensible will depend upon multiple factors, of which the numbers marked on a chart for IFR flight planning, and not one of those factors. The use of simple factors and numbers, getting pilots - including student pilots - off the hook of looking hard at the chart and forming a useful judgment, does not seem to me wise.

G
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Old 5th Dec 2017, 23:20   #4 (permalink)
 
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Minimum Height Rule was Rule 33 of the UK Rules of the Air and was one of the Instrument Flight Rules however; that disappeared on the introduction of SERA where the Minimum Height rules for VFR operation can be found in SERA.5005(f)
Quote:
(f) Except when necessary for take-off or landing, or except by permission from the competent authority, a VFR flight shall not be flown:
(1) over the congested areas of cities, towns or settlements or over an open-air assembly of persons at a height less than 300 m (1 000 ft) above the highest obstacle within a radius of 600 m from the aircraft;
(2) elsewhere than as specified in (1), at a height less than 150 m (500 ft) above the ground or water, or 150 m (500 ft) above the highest obstacle within a radius of 150 m (500 ft) from the aircraft.
In practical terms, taking the MEF from the chart and adding 1000 ft gives a reasonable VFR operating altitude. The MEF includes provision for uncharted masts and obstacles in close proximity outside the marked area.
Quote:
surely the MSA should be an altitude you come down to if forced by bad weather,
I think you are confusing this with the SA which is the minimum altitude you descend to when IFR!
For IFR Operation under SERA replacing Rule 33:
Quote:
SERA.5015 Instrument flight rules (IFR) — Rules applicable to all IFR flights
(b) Minimum levels
Except when necessary for take-off or landing, or except when specifically authorised by the competent authority, an IFR flight shall be flown at a level which is not below the minimum flight altitude established by the State whose territory is overflown, or, where no such minimum flight altitude has been established:
(1) over high terrain or in mountainous areas, at a level which is at least 600 m (2 000 ft) above the highest obstacle located within 8 km of the estimated position of the aircraft;
(2) elsewhere than as specified in (1), at a level which is at least 300 m (1 000 ft) above the highest obstacle located within 8 km of the estimated position of the aircraft.
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Old 5th Dec 2017, 23:43   #5 (permalink)
 
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Which is why the UK's "MSA" is a term that needs to be scrapped. (Along with QFE! )

I was taught it as an emergency minimum, RAF style... something to climb to if you loose references/get lost etc. Others use it as a minimum en-route altitude for all parts of VFR flights.

Minimum Safe(ty) Altitude is NOT defined anywhere, and so it means different things to different people. That's just dangerous.

Safety Sense leaflet 5e talks about "minimum altitude" during planning (4d), "Safety Altitude" when lost (7d), and finally "minimum safe VFR altitudes" in the conclusion (11). If the CAA can't decide...

This is why I promote the more EASA like terms: Minimum flight altitude for route segments (may be different for VFR and IFR plans, as defined by your ops manual, which would suit the descending against worsening weather), and a Safety Altitude to shoot to if it all goes white.

Last edited by Dusty_B; 6th Dec 2017 at 00:08. Reason: added all after Safety Sense.
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Old 5th Dec 2017, 23:53   #6 (permalink)
 
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Quote:
I was taught it as an emergency minimum, RAF style... something to climb to if you loose references/get lost etc.
In the RAF if you went IFR you climbed to SA However; MSA was the minimum level you considered you could descend to if for some reason you could not maintain altitude i.e. following some catostrophic en-route event, in the hope that you could get back to VMC.
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Old 6th Dec 2017, 07:28   #7 (permalink)
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Great information guys, although i'm just talking about a 20 hour VFR student, i dont want him to climb to 2200 feet if he gets into cloud, before he gets into cloud,i want him to be aware of his worst case 500/1000 ft rule altitude, probably also setting the regional QNH,then if he cant continue, turn round and go back to his point of departure.
I shall revisit SERA and the safety sense leaflets.

Last edited by memories of px; 6th Dec 2017 at 08:05.
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Old 6th Dec 2017, 09:05   #8 (permalink)
 
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I remember the days when you had to scour a map looking for the highest elevations and then perhaps missing one. There was also the posibility of uncharted masts, so the introduction of MEF figures for each map square really took away all the hard work.

For VFR you only need to look out of the window and have an idea where the high ground or masts are. MEF + 1000 feet provides a practical safety margin however; so long as you don't infringe the minimum height rule you can fly at whatever altitude you like. If the weather becomes an issue, current teaching is to do a 180 degree turn and go back to where you know its better. This is a skill test item.
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Old 6th Dec 2017, 11:04   #9 (permalink)
 
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I agree that the 180 degree term is a skill test item. but the CAA approch was a bit simplistic. As I saw it opon enter bad weather, the student should make a 180 degree descent down to MSA, if above MSA, consider which direction the bad weather is coming from based on form 215, consider the option for diversion, and request QDM's or radar.

The AAIB report on G-BIIJ, says it all.

I would add that on a cross country it is sensible to apply MSA for students or inexperienced PPLs. even in VFR. It also means you are less likely to be in conflict with miltary and rotary wing aircraft.
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Old 6th Dec 2017, 12:18   #10 (permalink)
 
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I would add that on a cross country it is sensible to apply MSA for students or inexperienced PPLs.
Would you like to define MSA and give us a reference?
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Old 8th Dec 2017, 23:03   #11 (permalink)
 
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I make a point of asking the candidate on every test to explain what they understand by MSA, since they have written it down on their plog.
None of the candidates except one has been able to explain any of the figures. I keep feeding this back to the instructors, but they donít understand it either!
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Old 9th Dec 2017, 13:07   #12 (permalink)
 
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Originally Posted by Broadlands View Post
I make a point of asking the candidate on every test to explain what they understand by MSA, since they have written it down on their plog.
None of the candidates except one has been able to explain any of the figures. I keep feeding this back to the instructors, but they donít understand it either!
I am surprised only one candidate has been able to explain the MSA figure in most plogs as I would have thought it would have been taught by their instructors. What has been taught for VFR PPL flying is likely to be some level of safety margin (probably 1000í) above the highest obstacle within a certain distance from track. I am not surprised a PPL candidate canít give you the definition for the Minimum Sector Altitude as they are not taught that.
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Old 9th Dec 2017, 21:57   #13 (permalink)
 
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Exactly the point I make. The misunderstanding originates in training by instructors who quote MSA but donít actually understand minimum altitudes etc etc, thus a candidate quotes a figure but canít explain properly where it came from or how to use it.
Itís always a good debrief item, one which hopefully leads to good decisions being made in their future flying.
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Old 10th Dec 2017, 19:09   #14 (permalink)


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Originally Posted by Genghis the Engineer View Post
Surely MSA is only an IFR concept - remaining at least 1000ft above anything within 5nm at all times. It has no relevance VFR.

Of course the concept of a minimum safe altitude (note non-use of capital letters) is relevant in VFR ops, but beyond being legal, it should be about a rational judgement about always being able to handle an engine failure, not bump into anything, and being unlikely to inadvertently enter controlled airspace. What is sensible will depend upon multiple factors, of which the numbers marked on a chart for IFR flight planning, and not one of those factors. The use of simple factors and numbers, getting pilots - including student pilots - off the hook of looking hard at the chart and forming a useful judgment, does not seem to me wise.

G
As Genghis says - MEA and MSA are IFR concepts. Student (and instructor?) needs to revise VFR regulations.
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Old 11th Dec 2017, 07:11   #15 (permalink)
 
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Student (and instructor?) needs to revise VFR regulations.
And in the absence of any Regulation re MSA and VFR; whats wrong with the statement in the first post?
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its MEA plus 1000 ft came the reply, seems he was told this by another instructor,
Apart from, MEF not MEA!
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Old 29th Dec 2017, 11:49   #16 (permalink)
 
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What is wrong with briefing an MSA for a VFR sortie? In the case of IIMC, that is what you want to climb to.

Yes, in an ideal world, the student will turn round/descend/divert before the IIMC scenario but we all know things often don't go as planned.

If he/she has a number on their map that they have thought about/briefed that will keep them away from obstacles/the ground if it all goes Pete Tong then who cares if they confuse Min Sector Alt with Min Safety Alt?

You can argue that MSA isn't relevant to a PPL VFR student but it will be in their future careers so why not teach it and include it from a early stage?

Reversion to IFR (planned or unplanned) is always a consideration in operational flying so get the concept and the terminology started from grass roots.
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Old 29th Dec 2017, 12:17   #17 (permalink)

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What is wrong with briefing an MSA for a VFR sortie? In the case of IIMC, that is what you want to climb to.
I include MSA in my routine climb/top of climb checklist (which is used VFR and IFR).

Obviously, it needs to planned in advance and kept under review in flight, leg by leg (especially if flying near/under controlled airspace).
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Old 29th Dec 2017, 12:52   #18 (permalink)
 
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You can argue that MSA isn't relevant to a PPL VFR student but it will be in their future careers so why not teach it and include it from a early stage?
Bit of a broad assumption. The average PPL never goes beyond being a PPL and never gains an instrument qualification.

We went through a phase with a UK PPL where 4 hours instrument training was mandatory however; in some cases that encouraged pilots to fly on instruments with a bare minimum of training.

The European licence removed that 4 hours and teaches only enough instrument flying to do a 180 degree level turn untill you become visual again. The LAPL doesn't even include that training. Teaching a VFR pilot to climb to a Safety Altitude for instrument flight is of no use if they can't get back down again.
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Old 29th Dec 2017, 14:11   #19 (permalink)
 
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Bit of a broad assumption. The average PPL never goes beyond being a PPL and never gains an instrument qualification.
but they will go off flying by themselves without being supervised by an instructor and possibly with other pressures on to go flying in less than perfect weather. At least if they understand why they need to have thought about an MSA figure it might save them.

They might get VMC on top or find a big gap to let down through - a whole lot better option than grovelling around too low in poor weather.

Quote:
The European licence removed that 4 hours and teaches only enough instrument flying to do a 180 degree level turn untill you become visual again
I was scrambled to a job from Chivenor where a PPL had set off with chums aboard to fly from Swansea to Shobdon - the weather was marginal and they went IIMC at the top end of the Neath valley. He executed his 180 turn but, due to limited instrument skills, stalled it halfway round as he lost speed and climbed slightly. That saved their lives as they missed the top of the hill by about 30' and stalled the aircraft nose down into a wood.

When we tracked their 121.5 beacon and broke cloud at the very top of the hill, we saw them waving from the corner of the wood and took them (uninjured) home.

You can't ignore the need for some basic IF skills with UK weather unless you never go flying - if a few use those skills unwisely then that is their lookout.
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Old 29th Dec 2017, 14:13   #20 (permalink)
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Absolutely so whoppity, i cant believe anybody would advocate a student climbing into further IMC, just madness, without knowing where the tops were or knowing how to get back down again, where the 0 degree isotherm is, i would never advocate going IMC without positive radar identification beforehand, students, stay VFR!

Last edited by memories of px; 29th Dec 2017 at 14:47.
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