Minimum safe altitude on PPL navigation

[slr737]

Quick question to PPL instructor here :

What do you teach to your student regarding the minimum safe altitude when on navigation.

For my part, I take the Maximum elevation figure along the route and ask them to add 500' to it. This should prove to be sufficient.

But what do you brief them if the wx deteriorate and they have to fly low level below a cloud base. We know that the max elevation figure is the highest obstacle in the area, but if you fly far from those obstacle, you could easily fly lower and still be 500' above the highest obstacle along your route (let's say 5 Nm each side of the route).

thanks for your comment

[RTN11]

I wouldn't refer to it as an MSA, it simply leads to confusing them if they go beyond VFR flying.

I would explain the MSA properly, with reference to flying in cloud and why an MSA would be relevant.

I would then explain how this does not apply to VFR navigation, and how to calculate a "sensible" altitude to fly. (If you love the TLAs you could always call this a "SAF" :})

This would be the 500' above MEF you have quoted, taking high terrain and obstacles in to account. This way, the PPL has a proper understanding of altitude to fly, and doesn't always stick to some stupidly high figure even if it puts you pretty much in cloud when they can perfectly safely fly lower.

[Big_Buddha36]

Hi,

In my book, 500 above max elevation doesn't determine a "MSA"

My reasoning is that max elevation on a chart is just that, an elevation. BUT
(there's always a 'but'!) the charts don't show structures (typically masts) that are below a height of 300'

As such, you need to add at least 800' (500 for rule 5 and 300 for the unmarked mast

I was flying around the Devon moors. There is a sector that has a max elevation of approx 1970' but there is a mast there unmarked

In my experience, we taught "add 1000' onto max elevation 5nm either side of track (ifr rules) unless the max
Elevation is a spot-height in which case add a further 300

It's quite safe to fly below this point if remaining vmc but if flying into difficulty, get yourself to this MSA. This
Could mean climb, but usually descend but if you are
Forced to
Go below that, turn back/divert

Bb

[BEagle]

There is NO requirement to 'add 300 ft for unknown obstacles' to MEF figures on the CAA 1:500 thou chart. Due allowance has already been included. If the highest elevation in a lat/long area is a spot height, then the MEF will already be 300 ft greater.

Read the information in the lower left hand corner of the chart if you don't believe me.

[Whopity]

What do you teach to your student regarding the minimum safe altitude when on navigation.MSA is one of the Instrument Flight Rules. Rule 33 in the UK.

For VFR flight look out of the window and fly at an altitude so as to avoid obstacles.

But what do you brief them if the wx deteriorate and they have to fly low level below a cloud base.Your Operations Manual should detail a minimum altitude for VFR flight and if the weather is likely to deteriorate below this you do not authorise solo flight.

[Genghis the Engineer]

Personally I tend to think of:

MSA/IFR
MSA/VFR
500MSD

Each of which is reasonably straightforward to understand as a concept, and for most VFR nav, MSA/VFR = MSA/IFR-500ft, generally is a sensible minimum. It has no legal force of course, but that doesn't stop it being workable and sensible.

If dodging to stay VFR below cloud, or having fun low level, then it's 500MSD, but done at one's peril!

G

[slr737]

thanks for all the information you provided.

Yes, the MEF already include a factor to the either highest obstacles or the highest terrain elevation in the grid.

I use MSA, as it is easy to remember. other instructors go with MORA. Which is also an IFR altitude. But we explained to the student the difference between VFR min et IFR minimum. those guys have just about 30hours and we just want to teach them minimum safe altitude for what they do? visual flight.

my issue is, you let the guy go. you check is nav planning and he has written that is minimum altitude is the MEF + 500'.
Great I'm happy. However during the day, the weather goes down and the ceiling is getting crap.
What would we briefing him. For us it is easy : common sense, we know what we have to do. However those student pilots with 30 hours have not yet " a common sense".

let's take an example, wx is enough but goes down. Ceiling decrease to the minimum altitude he has specified. vis is still good. So either he fly at the minimum altitude but just below the clouds (with the risk of it). or we tell him you can go down lower as long as you can see and avoid and return to the departure or diversion field. But to what altitude. the AIP will specify 500' within 150m of the highest obstacle but that is often well below the MEF in a grid.
yes it is safe to go below the MEF as the MEF is within a grid and your flight could me miles away from the highest obstacle.

so my question to the FI is what do you brief to your student when they go on their solo navigation. to which altitude could they go down if the weather was going down and they need to divert.

thx

[Whopity]

so my question to the FI is what do you brief to your student when they go on their solo navigation. to which altitude could they go down if the weather was going down and they need to divert.
The school should have established a minimum altitude for training; you do not authorise solo flight if the conditions are such that they would need to go any lower. This is what solo authorisation is all about, so you brief them that they do not go below the authorised minimum. It will mean that there are some days when its not suitable for solo even when the weather looks quite reasonable but, the instructor has a duty of care to ensure that the student is not placed in the situation you describe. In the very worst case, they will have been taught how to conduct a precautionary landing.

[Big_Buddha36]

BEagle,

i think i've mis-lead you a bit.

when planning, it was advised that you look 5nm either side of track, not the MEF as per vfr chart. - I agree that this does take the unmarked into account, but can be very limiting if you are to fly miles from the cause of the problem.

take 5nm either side of track, identify highest point. if its a mast, great, if not add the 300, that all I'm saying.