achimha wrote:
I’ve never seen a D-reg Aztec myself.
When we decided to start our own flying business in 1992 we were informed that we were required to own at least one aeroplane of the category that was supposed to be operated before we could apply for an AOC. In our case: all weather capable / IFR twin below 5,7tons. We knew from others that the process of getting an AOC could take up to one year (and this is exactly how long it took…) and during that time, the aeroplane would be of no use. So we looked for the cheapest one on the market that we could push into the remotest corner of some remote grass airfield for a year just to satisfy that ownership requiremt. Guess what? Already in 1992 the cheapest IFR capable twin on the German register that happened to be for sale was a Piper Aztec. For 25.000DM (12.500€) IIRC. We even went to see it. But unfortunately it was based at an airport with expensive hangarage and after looking closely, neither my business partner nor me were brave enough to fly it to that “remote grass airfield” where it could further rot for one year 
We went through exactly the same procedure with a couple of Aerostars and Mitsubishi Mu-2s that were just too scary to even open the door and try out the seats… In the end we went ahead and bought a decent C421 in the States which we operated illegally during the year we had to wait for our AOC. (This bit of the story is of course pure fantasy…)
So as far as I am concerned, the best thing they can do with G-LIZZ is to push it over the nearest cliff so it can become an artificial reef where octopuses can raise their babies 
Having landed at St Mary’s in the Jetprop last month, I feel for Timothy’s experience. 32 is a really tricky approach. A fine line indeed.
I salute his candidness in recounting what happened.
E
Everthing else aside, yes I agree, without doubt one of the more interesting approaches in the UK.
The main question for me, as with any accident/incident, is what can we learn from it.
During my IR training, I practiced timed NDB approaches at Luton in the simulator. It was definitely not something that I would feel comfortable with doing reliably in real life with such low ceilings. All other non-precision approaches were always flown as CDFA, which protects you against the danger of spotting the runway late and then trying to put it down on the remaining part. I think it is crazy to have a timed NDB approach as the only possibility on such an airport (or any airport for that matter).
I actually asked my instructor if you could set up the G1000 in a way that it would display you a virtual glidepath to any point in space. He said yes, but I won’t show you, because that is dangerous. I still think it would be safer to use your WAAS GPS in a way that allows to fly any approach as CDFA with advisory glidepath (as long as you respect step-down fixes and MDAs), but then I have very few real IFR experience. What is your take on this, and does anyone know how to do this on a G1000?
I don’t think any sensible aviator would fly this approach with an ADF. NDB approaches are to be flown with GPSes, it’s as simple as that. NDBs are useless and dangerous inland already but in coastal regions they are insult to the 21st century and its technologies. Keep it running as a backup if you like but don’t ever think about following the ADF needle!
Jeppesen has FN32 as the FAF for the 32 NDB approach. From that on maintain a 3° glide slope until 500ft AGL and drive forward to the locator which is 0.2 NM from the threshold.
achimha wrote:
From that on maintain a 3° glide slope until 500ft AGL and drive forward to the locator which is 0.2 NM from the threshold.
So there is a published RNAV overlay for the NDB procedure? Then of course for the lateral navigation I would follow the GPS rather than the NDB, and use FN32 as FAF and start a continual descent there. Where I beg to differ is for the vertical navigation part; I was taught to continually descend to MDA + 50 ft and then not drive, but initiate a go-around if not visual – except if the runway was 3000 m long or so. The “drive” part I think I will leave to more experienced pilots. I think in the US they would have indicated a VDP at the spot where the solid 3° line becomes a dotted line, and that is where the decision should have been made and the go-around already started.
Rwy20 wrote:
So there is a published RNAV overlay for the NDB procedure? Then of course for the lateral navigation I would follow the GPS rather than the NDB, and use FN32 as FAF and start a continual descent there.
No there isn’t but you wouldn’t follow the ADF needle when you have a GPS where you can get a more reliable and precise postionn fix. Published or not doesn’t matter. ADFs are not to be trusted and 100x less so in coastal regions. I wish there were no CFIs telling students to actually fly by the ADF needle…
Rwy20 wrote:
Where I beg to differ is for the vertical navigation part; I was taught to continually descend to MDA + 50 ft and then not drive, but initiate a go-around if not visual – except if the runway was 3000 m long or so.
That’s totally up to you but far from being a generally accepted rule.
What I find completely amazing about the approaches to St Mary’s (never having flown there), is how short the runways are for an IAP. Rw 32 is less than 700m and Rw 27, which also has a published NDB approach is a mere 523m. Isn’t there a minimum length for an instrument runway? I thought it had to be at least 800m, but clearly that’s wrong.
achimha wrote:
No there isn’t but you wouldn’t follow the ADF needle when you have a GPS where you can get a more reliable and precise postion fix. Published or not doesn’t matter. ADFs are not to be trusted and 100x less so in coastal regions. I wish there were no CFIs telling students to actually fly by the ADF needle…
I agree with this. Anyone flying raw data NDB approaches with a perfectly serviceable GPS that has the approach is nuts.
Where I beg to differ is for the vertical navigation part; I was taught to continually descend to MDA + 50 ft and then not drive, but initiate a go-around if not visual – except if the runway was 3000 m long or so. That’s totally up to you but far from being a generally accepted rule.
You can of course do either method. In larger faster aircraft with more inertia a constant descent profile is easier and usually favoured these days ie flying 3 degree glide to the MDA and then going missed if not visual. You do have less time to see the runway however. A dive and drive involves more configuration changes but if done correctly allows you to get down faster and have more time to look. With a short runway and poor weather that Timothy reported I would be more likely to get down faster and have more time to look.
Approaches like this are also where synthetic vision is worth its weight in gold.
You can of course do either method. In larger faster aircraft with more inertia a constant descent profile is easier and usually favoured these days ie flying 3 degree glide to the MDA and then going missed if not visual. You do have less time to see the runway however. A dive and drive involves more configuration changes but if done correctly allows you to get down faster and have more time to look. With a short runway and poor weather that Timothy reported I would be more likely to get down faster and have more time to look.
Ironically, Timothy and I have debated the merits of CDFA vs “dive and drive” at length. This incident is unlikely to settle any arguments.
One of the disadvantages of CDFA is that if your approach is slightly misjudged (because you haven’t got continuous vertical guidance), it can leave you above the glideslope. On a long runway that’s not an issue. On a limiting runway, it’s more of a problem. In the age of GPS and overlays, or even DME, it’s much easier to get close to the slope, but even a small deviation, 100 ft high can make a significant difference to the landing distance. Changing your mind, as Timothy says he did in this case, makes matters worse.
That said, “dive and drive” doesn’t necessarily help. It’s still very possible to misjudge the point at which you leave the MDA and do so too late. Again, GPS or DME helps to set a latest visual descent point.
So neither method cuts the pilot off from the temptation to say “oh yes, there’s the runway, I can just get in from here”. There is always that human factors risk, and few of us are immune from it.
