IMC - letting down

[LeeP-PA28]

Hi all

I've recently passed my IMC skills test but have not yet used it.

This question relates to flying VMC on top or flying in IMC near your aerodrome, where sufficient cloud base is available for a visual approach but where flying higher gets you into smoother air (let's say, you are flying at FL55 with few clouds at 1500ft, broken at 2000ft).

One thing I remember reading in my book about travelling to an aerodrome without an approach was you can either descend over the sea (if possible) til clear of cloud, track to a beacon if one is nearby and checked the MSA there or use an approach at a nearby airport (ie ILS or NDB) til visual then breakaway.

My instructor wouldn't commit to answer as to which was right or wrong, but mentioned that an approach only has 2 realistic outcomes: that being a landing or a go-around, by which you have a missed approach procedure and would usually climb back into IMC or on top again.

So - would an option be to request an instrument let down, or request an IFR approach with a touch and go and then proceed VFR to your enroute aerodrome?

What do you do?

Many thanks :)

Lee

[Cusco]

Why do you need a touch and go with your IFR approach?

What's wrong with descending to DA/DH or above if higher cloudbase then going around and proceeding VFR to your airfield?

I've asked a local base (RAF Lakenheath) for a RAS (as it was called then) to cloudbreak a couple of times over a particularly flat part of East Anglia but each time they were initially pretty unkeen and needed some persuading.

On one occasion I was all ready to go to Cambridge for an ILS letdown before LKH agreed.

[LeeP-PA28]

Thanks Cusco- that was my query.

Why do you need a T&G on an approach - surely an ILS or other IAP to DH and visual is sufficient - but how would one request that?

[Pace]

Normally the military will give you a descent but not below the MSA or the base of their radar cover. They will normally add that you are responsible for your own terrain clearance.
With any cloud break OCAS the most important thing is to know where you are and about other aircraft that may be just below the cloud you aredescending through.
Military radar are good at confirming both.
With any approach don't trust one indication but cross check what you believe is correct.
Even on an ILS I know of some pilots who have flown dead needles so again check the ident and various distance points against glideslope altitudes and the app chart.
It depends if it's a high cloudbase way above the SSA then let down.
If it's tricky ask for an approach for a cloud break with a breakoff to fly visual to your destination.
That has the benefit that if you break out lower than you hoped you can ask to Land.
As with anything new to you don't take on more than you can handle

Pace

[trex600]

Not sure if this is off topic but say if you enterd class D airspace VFR not above 1500ft and halfway to the aerodrome you become IMC due to cloud that you didnt forcast, Then you have Radar asking you to report field in sight.. What is the best thing to do?
I know they wouldnt vector you normally at the low altitude that you was cleared the VFR clearence.. 'at Liverpool below 1900ft'

[gg190]

Not sure if this is off topic but say if you enterd class D airspace VFR not above 1500ft and halfway to the aerodrome you become IMC due to cloud that you didnt forcast, Then you have Radar asking you to report field in sight.. What is the best thing to do?
I know they wouldnt vector you normally at the low altitude that you was cleared the VFR clearence.. 'at Liverpool below 1900ft'

Such a clearance will normally have the words 'maintain VFR' in it, which means you do exactly that, maintain VFR. If there is cloud in your way you either descend, go round it or do a 180, informing ATC of your intentions of course.

Alternatively you just request an IFR clearance to start with, if your licence allows of course.

[bingofuel]

My instructor wouldn't commit to answer as to which was right or wrong, but mentioned that an approach only has 2 realistic outcomes: that being a landing or a go-around, by which you have a missed approach procedure and would usually climb back into IMC or on top again.


I wonder if your instructor has any real world IFR/IMC experience.
Nothing wrong with coming down an ILS then once in visual conditions break off the procedure and continue VFR, just ensure ATC are aware of your requirements. I wonder what your instructor would do if he had to do a visual circle to land after an ILS when the airfield did not have an ILS on each end?

Be aware though that using an ILS generally incurs a fee payable to the provider.

Fly safe

[LeeP-PA28]

Thanks bingofuel.

I'm sure he has, being ex commercial airliner, however I think that the breaking away once visual and either getting a VFR or SVFR clearance after the approach is at the discretion of ATC.

I've just telephoned by local airport and they cannot see a reason why they wouldn't allow it - just as much notice as possible is required.

My airfield has an NDB to which I can practise approaches on in the overhead on a clear day, which unofficially one could build an approach on to a safe height maintaining rule 5 and rule 29 of course based on VFR/IFR. I just wondered what other people did in reality if their destination has suitable weather for a VFR approach with no IAP present, but where the enroute sector was totally overcast and no holes to descend through :)

[Cusco]

Why do you need a T&G on an approach - surely an ILS or other IAP to DH and visual is sufficient - but how would one request that?


'XXXX Approach, request low approach and go-around ILS RWY xx'

Then, when you land back at base phone up the ILS provider with your credit card details. ;)

[ShyTorque]

IFR means you must maintain 1,000 feet above the nearest obstacle within 5nm of your track. There is absolutely nothing to prevent you from descending to the altitude you mentioned to clear cloud whilst still complying with IFR. Best to get a radar service although bear in mind that the controller will usually inform you that you remain responsible for your own terrain clearance at all times.

Obviously, you need to know your position at all times and plan in advance.

[IO540]

FWIW it is not illegal (therefore it is 100% legal) to descend below the MSA, in a G-reg, in UK airspace, for the purposes of a landing, on a DIY "instrument approach".

You are always open to the "reckless" clause in the ANO but AFAIK this has never been used in these cases.

For an N-reg it is illegal worldwide; FAR 91.175 refers.

In practice, people routinely descend over the sea, to get intoa coastal airport. Just be extra careful watching the altimeter :) And be really extra careful watching it at night :) :) If you have an autopilot with VS/ALT modes, use it to the full while monitoring things.

[JOE-FBS]

I've only done my IMCR this year and my instructor was absolutely clear that the way to use it to get back to our VFR airfield if required (i.e. cloud base below MSA, otherwise, just get a traffic or deconfliction service for the descent through cloud) was to do an instrument approach into one of the local major airfields then break-off once clear of cloud and come home VFR. If you are worried about the 20 quid or whatever for the approach then I would suggest that you should probably not be airborne in such conditions!

Just to add a plug for the IMCR, I would encourage any UK pilot with a JAR PPL to get one in the last few months before it might disapear. I have had it only six months and have used some aspect of the skills or privileges nearly every time I have flown since getting it.

[Whopity]

IFR means you must maintain 1,000 feet above the nearest obstacle within 5nm of your track.A common Misconception. What Rule 33 actually says is:Subject to paragraphs (2) and (3), an aircraft shall not fly at a height of less than 1,000
feet above the highest obstacle within a distance of 5 nautical miles of the aircraft
unless:

[welliewanger]

Can't be arsed reading the whole thread, I'll just add an experience I had...

On a trip from London to York, it looked like it would be a much easier job to go on top of the clouds. However the destination airfield was just that - a field. A quick phone call to the nearby RAF base (Church Fenten IIRC) and they said something like "Normally we'd offer you an ILS and then you could divert once VMC, but it's U/S. How about SRA?" Since my knowledge of SRA is purely academic, I had to decline the offer, but it was good that the flexibility was there.

I think that most places are happy to help, it's just a question of communication.

[FlyingStone]

Just to add to Whopity's post, the 5NM (or 8km) is the distance from aircraft's estimated position (at least according ICAO Annex 2), so actual navigation performance is taken into account.

[Gertrude the Wombat]

Since my knowledge of SRA is purely academic
I did one on my IMC course - there didn't seem to be much to it (in the sort of conditions you're talking about, where the cloud base is reasonable for VFR, it just not above MSA). It shares with other instrument approaches that you can always decide you don't like it and go around.

[JOE-FBS]

I'll second Gertrude's post. In my IMCR course, as well as NDB and ILS, I did one each SRA and PAR, (being based near a friendly RAF station helps get the PAR) and they were fine. It's a bit like in your early stage training when the instructor talks you around the circuit and down the approach, except that the person talking is looking at radar screen(s) instead of sitting next to you.

[tmmorris]

Indeed. If you think of an SRA as a talking non-precision approach (so once inside the FAF you descend not below the MDA, if you like you can do it all in one go and then fly level at the MDA), and the PAR as a talking ILS, it's a piece of cake.

For the PAR you will need to be able to maintain a 3deg descent, just like an ILS, monitoring airspeed - rate of descent - airspeed -rate of descent all the way down, and adjusting following what you hear instead of what you see on the ILS receiver.

Not only that, but your friendly local RAF station will monitor your decision height (usually by saying 'Procedure minimum for this approach is 200ft' and waiting for you to say 'Decision height for this approach will be 500ft, this approach will be to low approach and go-around' or whatever) and then tell you when you are 'Approaching decision height' and 'Passing decision height'. They'll do that for an ILS, too, as they will use the PAR equipment to monitor your approach. It's like a virtual co-pilot, and very handy.

The only downside is they will expect you to conduct approaches on QFE - which is a whole separate argument I don't want to kick off again! (Hence references to Height in the foregoing.)

Tim

[JOE-FBS]

...and those nice RAF ATCOs will ask you whether you have done your downwind checks and to confirm, every time around, that you have fixed gear. Very helpful but distracting when you're trying to learn to fly instrument approaches on a turbulent day with Chinooks and Pumas hurtling around underneath you.

Seriously, I am very grateful to RAF Benson's ATCOs.

[Pull what]

Why are so many people talking about ILS and PAR minima? Your MDA is the transit altitude to the base aerodrome or the circling minima for the cloud break approach (if your transit starts in the same direction as the circling approach). Why even do an approach?- a cloud break can be from any known position that either you or ATC can define accurately?

[CJ Driver]

Like "Pull What" I am also wondering why people are talking about minima when the task is to get through a layer in order to continue VFR to your destination - there must be more than a thousand feet of VMC under the layer or you would already have switched to plan B.

It's a few years since I did my IMC, but do they really teach such different stuff nowadays? All you do is go to the last VOR on your trip, draw a line that heads towards low ground, and as you cross through the overhead of the beacon start a descent in that direction. If you're still IMC at 1000 feet AGL, it isn't going to work so you climb back up and divert to a "proper" airfield with an approach.

[Pull what]

CJ the answer is that most have never done it so have never been faced with working out a practical solution

[Contacttower]

If you have a clearly defined route that you know that you can maintain compliance with the IFR on down to a certain altitude and know that you are on it; for example starting from a VOR and saying..."at so many miles from the airfield I can descend until atitude x, at which point I must accept that visual recovery will not be possible if still in IMC and divert" then I don't see any reason to do an IAP provided you maintain the IFR during descent.

However one might not have always worked a route out or due to ATC or whatever you may have ended up away from the waypoint you were going to use. Rather than scour the VFR chart for obstancles to work one out it might just be easier and safer to do an IAP to another airport and then if possible fly visually if you are unprepared or unsure.

[tmmorris]

Rather than scour the VFR chart for obstancles to work one out it might just be easier and safer to do an IAP to another airport and then if possible fly visually if you are unprepared or unsure.

which also has the advantage that if you misread the chart or miss a NOTAM about a new obstacle that's not on it yet, you won't be endangering yourself unnecessarily.

Tim

[Pace]

There are cloudbreaks and cloudbreaks? The big danger are CFIT accidents or OCAS running into other aircraft that you are not aware of how do you securely cover both aspects flying OCAS?
If you are on your own ie no reliable radar coverage you have to have a plan to minimise the risks as much as possible.
To blindly follow any navaid information whether it be ILS, VOR, NDB GPS etc is asking for trouble unless you confirm those navaids are telling you what you think they are?
Always confirm the navaid info by some backup.
Descent OCAS and you want to make sure you dont fly into cumulus Granitus clouds!!!
The only way to do that is to respect the sector safety altitudes using the regional QNH.
descending below the sector safety altitude and everything becomes more precise.
Spot altitudes? Mast heights etc? How far do you descend above those points before calling it a day?
That depends on how much risk you are taking!
Are you really where you think you are? If not you could be in for a disaster.
I know of one pilot who flew dead ILS needles down the wrong valley in the Alps lucky for him ATC alerted him as he broke out in the wrong valley!!! It does happen!
Hitting other aircraft? most (not all) have transponders so should show up if your lucky enough to have TICAS!
Radar can help if you have radar coverage!!!
If not listening out on local frequences? Otherwise its relying on the big sky theory!
If you have to take an approach into a nearby airport to break off for a visual landing at your own field/ landing strip seriously consider landing off that approach as the cloudbase is likely to be be so low as to make flying VFR questionable?

Pace

[Contacttower]

Spot altitudes? Mast heights etc? How far do you descend above those points before calling it a day?

Well I would say, as long as you maintain compliance with the IFR...ie 1000ft clearance within 5nm the estimated position of the aircraft.

If you have to take an approach into a nearby airport to break off for a visual landing at your own field/ landing strip seriously consider landing off that approach as the cloudbase is likely to be be so low as to make flying VFR questionable?

Quite possibly that would be a good decision. But if you know the area really well and the distance is not far to get to your field then a low level transit would probably be OK at say 800ft.

[Pace]

ContactTower

Totally agree 1000 feet is a good margin to use.
Being a realist pilot will use smaller margins sometimes much smaller and there lies the danger.
Normally if you fly an approved approach for a cloudbreak to a VFR field then that usually means a normal cloudbreak is not possible!
Transitioning from IFR IMC to VFR minimal VMC is always confusinng meaning getting your mindset into a VFR gear.
If when you break out the pilot is not secure I would recommend a landing request or a predeclared intention to land if VFR not acceptable to the pilot!
Obviously familiarity with the area plays a large part in that decision ;)

Pace

[CJ Driver]

I'm sorry guys, but once again I am going to drag the thread back to practical reality. The original question was a simple one - for a freshly rated, but not yet really used it, IMC pilot, on a perfectly fine VFR day BELOW the clouds, when the said pilot is at (say) FL055 and is ABOVE the clouds, how do you get home?

And the answer is nothing to do with instrument approaches, and dangerous ducking-under manouevres, or SRA let-downs, or any of that stuff that implies doom and gloom and that this would be an unusually scary thing that you are about to do.

The answer is - fly to an easily identified waypoint, such as a nearby VOR. (Which you will have identified using the morse code ident, and checked the flags on the indicator, and all that good stuff, because you are a well trained and recently qualified pilot). Starting from that unimpeachable position fix, point the aircraft in the direction of low ground (which includes looking at obstacles, hills, and so on - see previous comment about well-trained pilot). And then simply descend through the clouds whilst maintaining the chosen outbound track.

The only thing you need to make a mental (or perhaps written) note of before you start down is the obstacle height - to which you will have added 1,000 feet.

If the weather is as expected, you will pop out into VMC, and fly home. If the weather is worse than expected, you will still be in the clouds when you reach the previously noted altitude. DO NOT DESCEND BELOW THIS ALTITUDE. Instead, climb back up to MSA, and revert to plan B (which probably involves diverting to an airport with an instrument approach).

But in the scenario originally described, where you are flying "on top" and there is good VMC underneath, this is the time-honoured and well proven way of getting from "up there" to "down there", and is pretty much foolproof. It must be, because I've managed it hundreds of times. :)

[LeeP-PA28]

Thanks for the replies and in particular CJ and Pace.

Yes, I had planned on using a radial from Otringham with DME and also using the fields NDB to descent into an "area" of know altitude / obstructions on a heading inbound and if not visual by 1400ft on the QNH then diverting at my local base and this model can be used anywhere with prior planning. And should I be transiting Doncaster for example on my route back, it made only too much sense to me to ask the question - can I shoot the ILS til visual as it's almost en-route and then fly the rest of the way VFR should the cloudbase permit. This gave the added bonus of being under a radar service and descending into a safe and known area with the added bonus of, if reaching the MSA and not visual, shooting and landing at the airport and this can be applied on any trip.

At least I have in my mind my options - just need to get myself a subscription now to Jeppesen and keep practicing approaches to keep current.

Thanks all :)