MSA over the sea

[tmmorris]

Simple, really... what's the MSA over the sea?

If you wanted to let down to an airfield on the coast without an IAP, and could let down over the sea, how low could you legally go? (Ignore for the moment the question of the legality of home-made IAPs, which might or might not be safer but where descent below MSA is involved - that's a separate argument.)

Do the charts as usual show all obstacles above 300ft?

Tim

[Aussie Andy]

I'd say 1000' AMSL if no rigs etc. marked on the chart...

Andy

[S-Works]

As long as the waves dont lap over the windscreen. ...... Seawater is havoc on the aluminium!

[boomerangben]

1500 feet (at least that is what is used by the North Sea Helicopter companies). And to descend below that requires a CAA approved self interpreted radar approach.

It is not so much the fixed obstacles (although wind turbines are sprouting up daily) but the moving ones that are of concern. Most (but not all) vessels that you can expect in British waters will be below 500 feet high. But it is not uncommon for Mobile Offshore Drilling Units to be towed around the coasts of NW Europe and they will be around 500' high. There are also a couple of crane barges that visit the North Sea from time to time with 200m long booms. It is an amazing sight to see them sticking out of the top of sea fog.

[skydriller]

1500 feet (at least that is what is used by the North Sea Helicopter companies). And to descend below that requires a CAA approved self interpreted radar approach.

Boomerangben,

1500ft? Are you sure? Its just that my experience as pax in the North Sea would definitely say more like 500ft, or even less.....can you expand on the 'self interpreted radar approach' bit, as I am constantly amazed at the crappy weather that does not seem to stop the choppers flying.

If you are a chopper pilot in the North Sea, I have a question: Have "recently" been working in the dutch sector...How come the Schreiner guys "always" seem to be grounded due wx, when you can hear the Bristows boys happily flying around over the Radio? Is it Type/Equipment? Company Regs? Registration issues re.G/PH?

Regards, SD..

PS : Always amazed at the weird nature of sea fog, it is spooky and beautiful at the same time to see dense fog surround the rig yet see the top of the legs and derrick bathed in sunshine and see just the derricks/cranes/legs of other rigs jutting up from the milky layer once above it.....and hopefully on the way home.....

[slim_slag]

FAR 97.3

(i) MSA means minimum safe altitude, an emergency altitude expressed in feet above mean sea level, which provides 1,000 feet clearance over all obstructions in that sector within 25 miles of the facility on which the procedure is based (LOM in ILS procedures).

So at least 1000ft.

[IO540]

Surely, for VFR, there is no lower limit. You can legally fly down to the surface. You have to keep 500ft away from man made objects - the usual thing.

For IFR, it's 1000ft as usual - unless taking off or landing and then no limit applies.

[tmmorris]

Thanks all - yes, Boomerangben, that's rather what I'd suspected, i.e. the moving obstacles would be the problem. As I was definitely talking about IFR-VFR transition then that would be an issue.

So in practice an IFR letdown at a nearby suitably equipped airfield followed by low-level VFR to destination is the way forwards, as this would allow me down to <1000ft.

Tim

[FormationFlyer]

The remark about VFR vs IFR is interesting - an important part of IFR which is often not used....below 3000' clear of cloud you are exempt from 1000' above the highest object - therefore if flying in VMC under IFR or VFR the height you can legally fly at is the same.

(as an aside - it is also often misunderstood that once above 3000' it is very easy for the average pilot to become IMC even though they are actually flying *visually*.)

The only difference therefore is IMC on an instrument approach. Minima are defined by the procedure and personnel licensing (IMC/IR). Additionally you have the approach ban as well.

However, I havent ever really investigated the legality of descending below MSA on an unpublished approach...I personnally would have thought that it wasnt allowable - but I cant remember if there is an exemption for an approach - I will certainly check the wording in UK AIM tonight!!!

Just a thought but as we are talking MSA the fact its over the sea is not entirely relevent - as the landfall would be within the catchment area for MSA calculation.

Additionally NOTHING below 300' makes it onto our charts - that is not just 300' agl but 300' asl!!! Thus making it at least 1300' agl - even over the sea, as you would have to allow for an object up to 299' on the beach, or 1mile out...

[IO540]

This is going to start another long thread, so I am getting out of here after posting this, but...

However, I havent ever really investigated the legality of descending below MSA on an unpublished approach...I personnally would have thought that it wasnt allowable

is incorrect. In the UK there is no rule against a DIY instrument approach.

Whether it is wise in a given location, etc, is a separate issue.

[Flyin'Dutch']

MEF from charts + 1000ft if you must.

Flying to a place with a proper IAP and then either a VFR transit to your intended destination if possible or land at the place with the IAP if VFR transit not possible.

You can then ring UV to see if he can organise a free landing fee for you.

[High Wing Drifter]

I concur with IO540. Good job, because I have seen a/c appearing out of the murk at often enough at Blackbushe (successfully and without drama too).

[fireflybob]

I0540 states...>In the UK there is no rule against a DIY instrument approach. <

Well thats a matter of opinion - this was debated in another thread - take a look at:-


DIY Instrument Approaches

[niknak]

Why not have a word with someone who does it on a regular basis.
The best example I can think of is Loganair, who do the Glasgow - Barra schedule service in the DHC6 (twin otter).
I flew on the service about once a month for two years, and we often had to an instrument let down over the sea to land on the beach.
Minima's were quite strict and adhered to like glue, the pilots often stated that the biggest problem was spatial orientation when you broke out of cloud and still had a lot of sea in front of you.
That, in my opinion is the biggest single factor to bear in mind when doing a cloud break over sea as opposed to over land.

I'm sorry, I've lost touch with all the people I used to know in Loganair, but I'm pretty sure that their Ops are still based in Glasgow, and an internet search will get you a number.
They always were a very friendly and highly professional bunch, and I'm sure they'll do their best to help.

[High Wing Drifter]

NikNak,

Generally, commercial operators are allowed to operate outside of the normal rules of the ANO if their CAA issued operators certificate permits the exemption or provides additional flexibility.

[englishal]

In the UK where IFR and VFR merge into some strange condition when in Class G, the rule you have to watch is the 500' rule, so assuming over the sea, then 500' would be a safe minimum. You could in theory go lower, so long as you don't end up within 500' of anyone.....Even this may not be applicable if you're landing, I can't remember.

[Halfbaked_Boy]

Well I've been acting pax in a Yak at 50 feet above the North Sea so...

Cheers, Jack.

[RPMcMurphy]

Whilst Loganair can be acknowledged as experts in making approaches in poor weather, it should be remembered that they have lost a couple of aircraft and crews over the last 10 years; once descending over the sea to get visual on one of their discrete approach procedures, and once over land attempting to get visual on a base leg join in poor weather.

Even if it is legal, it doesn't mean it is safe if even the experts get it wrong.

[tmmorris]

Not so, I'm afraid, Englishal - not in my copy of the ANO, anyway...

28 (1) In relation to flights within controlled airspace rules 29, 31 and 32 shall be the Instrument Flight Rules.
(2) In relation to flights outside controlled airspace rules 29 and 30 shall be the Instrument Flight Rules.

Minimum height
29 Without prejudice to the provisions of rule 5, in order to comply with the Instrument Flight Rules an aircraft shall not fly at a height of less than 1000 feet above the highest obstacle within a distance of 5 nautical miles of the aircraft unless:
(a) it is necessary for the aircraft to do so in order to take of or land;
(b) the aircraft is flying on a route notified for the purposes of this rule;
(c) the aircraft has been otherwise authorised by the competent authority; or
(d) the aircraft is flying at an altitude not exceeding 3000 feet above mean sea level and
remains clear of cloud and in sight of the surface.

29(a) is the authority for unapproved instrument approaches (unless you want to quibble about 'necessary'); but otherwise 28 makes it clear 29 does apply outside CAS assuming you are IMC. If you are VMC below 3000ft then you can go lower - but that wasn't the point of the original question.

Tim

[englishal]

it is necessary for the aircraft to do so in order to take of or land;

The way I'd view it is that if you're landing IFR, 29(a) applies, so you can come down to whatever. As soon as you become VMC and you're not really on a published IAP, you can't really be IFR, therefore the VFR rules apply, notably the 500' rule. This is stated in

Without prejudice to the provisions of rule 5