Gfc700. I am referring to an LPV approach. Not certain about an ILS as I haven’t tried it (or should I say ATC hasn’t tried it).
Ooooh errrrr, are you talking about the KAP140 or GFC700 flavour G1000?
NCYankee wrote:
Some GA autopilots require capture from below and a minimum amount of time with altitude hold and an all the other criteria being met. Of the autopilots I am familiar with, the worst is the CIII which needs 20 seconds after ALT is engaged.
The G1000 can capture from above but you need to exit the vertical mode you are in eg VS briefly by hitting ALT while APR is armed and it will then engage GS.
There does seem to be a veritable rash of these LPVs in Scotland. The nearest to us is Campbeltown, which is available from June 23.
I’ll ask HIAL about approval for non-commercial flights, and for training, unless someone else has done so.
Timothy wrote:
Some autopilots, including mine, require 3nm on the centreline with ALT hold on before they will capture the GS.
Some GA autopilots require capture from below and a minimum amount of time with altitude hold and an all the other criteria being met. Of the autopilots I am familiar with, the worst is the CIII which needs 20 seconds after ALT is engaged. So if you are flying the approach at 180 kts GS, that is 3 NM/Minute, so 1 NM is all that would be required. For this type of autopilot, I definitely prefer to engage the APR mode (LOC Norm and ALT) and not to complicate matters by stepping down first. I prefer to use the intercept of the GS at the higher altitude. In this case, GS intercept would be expected at nominally 1.6 NM (500/318) before the FAF. With a 3.3 NM intermediate leg, that gives the autopilot 1.7 NM before the intercept and even at 180 Kts GS, that translates to 34 seconds. 180 Kts is way too fast IMHO, so in reality,one should have more time with this autopilot.
NCYankee wrote:
Why? This is certainly not a requirement in the US.
I’ve now checked in PANS-OPS and there is not a requirement for a level segment, but the descent gradient should be “as shallow as possible”. So that could still be the explanation.
I mixed this up with the requirement for the intermediate approach part of an RNAV approach to end with a straight segment at least a 2 NM.
Airborne_Again,
Some autopilots, including mine, require 3nm on the centreline with ALT hold on before they will capture the GS.
I believe that the minimum between IF and FAF is 3.3nm, at least in the UK.
While that is true if using contours, I use the elevation in GoogleEarth. It’s not perfect, but it’s actually very good.
I start by looking at the elevation of the threshold to see how far displaced it is from the published figure. It’s rarely more that 10’. I can then use that as a sort of GBAS. If the threshold elevation is accurate, there is every reason to think that the 2nm leading up to it are equally so.
Generally speaking, depending on the nature of the terrain on the approach (and, to a lesser extent, in the missed approach) and the size and visibility of the runway, I am usually happy with a figure around 400’ and 1200m vis. That is predicated on using the autopilot to hold centreline and RoD so I can focus on check altitudes and looking forward.
Sorry, Anthony, we crossed, I think I didn’t see that there was another page.
Airborne_Again wrote:
There has to be a level segment of some minimum length (2 NM?) between the IF and the FAF. If PU23I was both IAF and IF, you would then only have 1.5 miles to descend 500 feet.
Why? This is certainly not a requirement in the US. There is 3.5 NM to lose 500 feet. That is only 142 feet/NM. In the US, the standard limit is no more than 150 feet/NM for the IF to FAF segment. With an LPV, I find it more convenient to intercept the GP at the IF altitude. This is easier to couple the autopilot and I let it intercept at the higher altitude and make the descent on the GP. The GPS provides the GP immediately on the FAF becoming the active fix (usually on passing the IF). A three degree GP is 318 feet/NM.
AA wrote:
But you don’t need to be “cleared for an approach” in uncontrolled airspace! That requirement is another UK speciality. An approach clearances is a requirement in the US because virtually all approaches are at least partially in controlled airspace. Only two days ago, I flew an IFR approach in Sweden without a clearance, to an uncontrolled (AFIS) airport in class G airspace. Perfectly ICAO compliant.
Same in Australia…except not even an AFIS is required…
