On the other hand, it is very useful precisely for the purpose in respect of which its use is (arguably) forbidden – to break cloud at a safe height on the extended axis of a “proper” AIP runway
That is actually a subtle question.
In the UK, G-reg, it is without doubt not prohibited to fly a DIY IAP, in any airspace where a clearance is not required (basically, in Class G).
It is a really good Q whether you can or cannot do this where an IAP is charted and published. I have never seen this aspect discussed before.
The first thing blocking it would be that the airport itself is likely to have published opening hours, and ATC, with, allegedly, reportedly, 3rd hand info, a £1000+ CAA fine if you land without a landing clearance, which is a mandatory report event to the CAA. This is incidentally why when you are on short final when somebody starts to read out War and Peace and their inside leg measurements, you are forced to go around even though that is a patently less safe procedure. Whether it is licensed or not will also affect it. Shoreham, before its IAPs were de-published recently, would have been a really interesting exception, after it became A/G on certain times!
But subject to the above issue I cannot think why it should be illegal.
If you’re operating a non-EASA aircraft you may fall foul of ANO Part 5, Ch 2, Section 3:
EASA aircraft may be captured by Part NCO.OP.110
Haven’t had time to digest, but the implication seems to be that if there is an IAP you need to use it.
Apart from the very good point about non-certified types being illegal to fly anything, including an IAP, in actual IMC (unless (a) their “permit” does not contain a VFR-only limitation and (b) the airspace owner does not prohibit IFR in non-certs) I don’t read anything above as simply stating that if an IAP is published, you must use it.
IMHO if a competent lawyer wanted to write such a reg, he would write something like FAR 91.175 which in superb clarity says exactly that
Sec. 91.175
Takeoff and landing under IFR.
(a) Instrument approaches to civil airports.
Unless otherwise authorized by the Administrator, when an instrument letdown to a civil airport is necessary, each person operating an aircraft, except a military aircraft of the United States, shall use a standard instrument approach procedure prescribed for the airport in part 97 of this chapter.
Peter wrote:
I don’t read anything above as simply stating that if an IAP is published, you must use it.
Not in that paragraph, but
NCO.OP.115 Departure and approach procedures—aeroplanes and helicopters
(a) The pilot-in-command shall use the departure and approach procedures established by the State of the aerodrome, if such procedures have been published for the runway or FATO to be used
OK; a good one.
Now, what if the IAP is not authorised (e.g. because there is no ATC or whatever form of approach control)?
I mean… if the IAP can be flown, why not just fly it?
Just for the sake of it, if anyone had the idea of flying into Fairoaks two dots below the visual guidance on runway 24, you’ll end up in the trees.
Not if it takes you to the threshold.
I have flown into Fairoaks 24 in the last three hours and I assure you that a 3° slope to the threshold is nowhere near the trees.
The highest notified obstacle (tree) for Fairoaks RW24 is 2094ft from the end of the runway and 93ft above threshold elevation. Or in other words, a slope of 2.5431 degrees. Two dots below a notional 3 deg G/P on most G/A aircraft would give you a 2.76 degree G/P, a vertical displacement of 7.56ft above the obstacle. On the positive side, the tree is displaced 6.636 degrees (231ft) right of centreline.
3deg slope isn’t in the trees, two dots below and you’re close enough to it. There’s a reason the PAPI on 24 is at 4deg.
What I’m getting at is that there is a significant protection margin in an instrument approach and we shouldn’t think the visual guidance feature of the GTN is similarly protected. You might object that this is not what you intended, which I would readily accept. But your comment on flying 2 dots down to aim for the treshold instead of a touch down zone could be mistaken as such, and I’d rather call it out.
The whole thing just demonstrates how the regulators are far, far behind the times.
In times gone by, instrument approaches were based on expensive, ground based navigation aids which required a lot of effort to set up, calibrate and maintain. GPS with WAAS has given everybody the ability to fix their location in 3D space with high accuracy, and in the case of aviation GPS, with integrity monitoring.
So assuming a moderate amount of due diligence, a virtual glidepath to, say, 500ft above the threshold at one’s home airfield or any other airfield the pilot has visited and checked out for the purpose, is perfectly safe to fly. From 500ft, any adjustments to the glide path to take into account a more reasonable touch down point can be made – this is, after all, more than a mile to the threshold.
And anyone who ever broke out from an NDB approach at system minimum of 300ft (!) knows that the runway tends to be not quite in the expected position, requiring higher adjustments – surely this is not beyond the wit of the average IFR pilot.
And ideas of persistently following a vertical glide path indication with the needles indicating “too low” are just dangerous, by the time this becomes relevant you should be purely visual, and see any trees you might fly into.
It is worth remembering that most accidents on DIY approaches into airfields without official approaches happen in weather conditions where CAT II or CAT III landings would be required.
