I remember LPV from my type rating course.
It’s: Likely Pilot Violation
I remember LPV from my type rating course.
It’s: Likely Pilot Violation
Makes sense to me. If you are flying an aircraft that requires a type rating, there is more than an excellent chance it does not have the capability to fly LPV approaches.
If you are flying an aircraft that requires a type rating, there is more than an excellent chance it does not have the capability to fly LPV approaches.
I think almost no commercial (AOC) ops in Europe have LPV capability.
In fact some of the UK ones I have seen were flying the most unbelievable wreckage (Islanders and Trilanders come to mind). However some of these old wrecks must have eventually got LPV because Alderney – a little island they fly to – is the only UK place with LPV, and the story I heard was that they pushed to get it, because the old NDB approach had a useless MDA.
A year or so ago I flew into some German airport (Stuttgart or Cologne?) and the ILS was INOP. I was offered the VOR or the GPS/LNAV approach, so went for the GPS one. Everybody else on the radio (airliners) took the VOR one!
It’s no wonder things move slowly here. Given that all these AOC people fly the NDB or VOR approaches using the FMS, probably with a baro derived “glideslope”, the driver behind GPS approaches is just GA i.e. no serious money. I wonder if/when there will ever be pressure for GPS procedures from them? I can’t see the point in them spending money. It’s like me… before I got the KLN94 AFMS done authorising GPS approaches (and thus able to fly them overtly no matter who was listening to the radio, after I posted on some pilot forum that I can’t fly them legally 
) I used to fly the NDB/DME etc ones using the GPS. Most GPS/LNAV approaches at these places have the same minima, or the minima is improved by an amount barely discernible on the altimeter and certainly not settable on the autopilot which is in 100ft steps… most people I know flying to an MDA of say 460ft will set 400ft on the autopilot as a backstop, obviously keeping an eye on it on the way down.
LPV would change all that of course, but not for operators who already have a FMS-generated glideslope down to some useful level. Can any airline pilots here say what their FMS glideslope goes down to, if the only IAP is say a VOR one with an MDA of 500ft?
… most people I know flying to an MDA of say 460ft will set 400ft on the autopilot as a backstop, obviously keeping an eye on it on the way down.
Most people I know flying to an MDA of say 460ft will set 500ft on the autopilot as a backstop….
I wondered who would be the first to respond
I believe I am correct, because if you set 500ft the AP will level you off 40ft above the MDA (mine won’t go below it at all) so you waste 40ft’s worth of an opportunity to get visual. There is no point in levelling off above the MDA. You are just wasting an approach because you have failed to fly it as charted. 460ft is by definition SAFE. Only on a JAA IR checkride, hand flown, maximum workload ever, does one go around 50ft (or whatever the FTO manual says) above the MDA. Some even get you to go around 50ft above the ILS DA, which is definitely wrong because the ILS DA is designed to support an undershoot.
So what happens is that the thing levels off, drives the elevator trim back (just to keep you on your toes, AF447-style), pitches you up loads (because the power setting was already low) and if you are still in IMC then you have to disconnect the autopilot, push the yoke back down until you are at 460ft, and then maybe do some fast finger work on the trim wheel – whether you become visual or not. And if you are visual you have thrown away some distance (by the level flight section at 500ft) so you have to re-establish some kind of a stabilised approach, but it will be steeper – especially that close to the runway.
If you let the AP to level you off, at any low power setting, that is really hazardous. The TB20 will stall eventually (if clean) with an MP below 18" – probably similar with approach flap. But you won’t be at 18" when flying an approach. More like 16" or less. In IMC, many pilots won’t catch this situation until rather late (never happend to me of course ).
Whereas if you use the autopilot to fly the entire trajectory down to the MDA and through it, your workload is low until the altimeter shows 460 and then if you are not visual you have just one thing to do: go around. And if you are visual at 460ft, you don’t have to do anything for another 60ft, so you leisurely disconnect the AP, go a bit lower, select landing flap, call visual, etc. In my case, you will be reasonably aware at 460ft because you got the GPWS “five hundred” warning 
If I have an MDA of 460ft I set the A/P to 460ft.
the FMS calculates a glideslope all the way down to the runway threshold. The pilots feed the non precision minimum into the FMS (in your case a MDA of 500ft).
During the approach the synthetic voice calls out “Approaching Minimum” and “Minimum” plus a visual minimum warning on the PFD. The GS indication continues beyond the minimum towards the runway.
If I have an MDA of 460ft I set the A/P to 460ft.
So would I, Jason,
However, deliberately setting any autopilot (even only as “a backdrop”) to level off BELOW the published MDA is not wise.
In the case Peter was describing – I would possibly set his A/P to 500ft, planning to cancel automatic ALT capture before reaching that altitude, then levelling off manually at MDA (if not “visual”). If I did forget to cancel automatic ALT capturing, my “backdrop” set at the safe 500ft rather than unsafe 400ft would take over.
The GA autopilots I am aware of don’t level off at all when reaching the DA/MDA. That is the pilot’s job. If it is an MDA, you are not permitted to descend below it without the runway in sight, there are no sink thru privileges if there is a MDA. Also, the point at which the advisory GS reaches the MDA (say one that is 600 feet HAT), requires at least 2.3 SM visibility to see the threshold from that point. Many of these approaches have a visibility minimum of 1 SM, which at a US airport located in class G conditions is VFR.
Well a G1000 on a NPA is either descending using V/S mode to an altitude capture (MDA) or on an advisory G/P where it won’t descend below the altitude bug. I agree you have to set the MDA. Alternatively I guess you could set it below and rely on the call out at Minimums but I don’t do that.
