The ‘approach ban’ for private flights in the UK only applies if an RVR is reported.
I could count on one finger the number of people I know who knew that…
JasonC wrote:
In the last SEP I flew I added full flap at top of glide on an ILS.
In a C172 Vfe for full flaps is below the reasonable speed for an instrument approach. Also, you would need a lot of power since full flaps add a lot of drag.
Flyer59 wrote:
but any experienced instructor (like me :-)) can tell you
That’s an argument! 
Club instructors do not humble me because too much of their teachings are wrong. I prefer reading the manual and follow it over an instructor any day.
The subject here is not landing in VMC. It is about landing in low visibility which for a precision approach means conditions when RVR is reported. In such conditions changing the configuration or speed close to the ground, in the tip of the ILS cone, at a time you focus on acquiring and maintaining visual references and continue the approach to landing, is not the brightest idea. It adds to your workload, you risk loosing your visual references and worst case loose control.
;-) That was just for the fun of it. I am anything like an “experienced FI”. I am just a poor CRI and sometimes i do checkouts on Pipers, Cessnas, Robins and the Cirrus …
But the easiest way to lose control after landing is to land too fast. That’s the main mistake of many pilots, that they have very lousy speed control and land too fast. And landing with less than full flaps plays a part in that.
If you “lose control” just because you extend the flaps from 50 to 100 percent … well, I wouldn’t want t to fly with such a pilot. I did not advocate doing that while still in IMC. But when you’re under the cloujds and have the rwy in sight you can easily extend the flaps to full and land.
Flyer59 wrote:
well, I wouldn’t want t to fly with such a pilot. I did not advocate doing that while still in IMC. But when you’re under the cloujds and have the rwy in sight you can easily extend the flaps to full and land.
But in very low vis you are essentially never under the clouds in VMC. To the point made by Josh earlier are you really going to add a stage of flaps at 120ft with still marginal vis (and risk a balloon up into the mist again)?
Peter wrote:
You don’t want to go full flap while on the autopilot because it won’t control the baloon (but it does work; it’s just really messy).
This is implementation dependent. I would typically prefer to the the automation handle the retrim rather than do it myself a very low level while trying to keep sight of the runway. But my autopilot doesn’t balloon much.
What I wanted to say is that I would not play with the flaps as long as i’m in the clouds, but will set full flaps once i’m out of the clouds and have the runway in sight. Since I don’t do approaches in which i have very bad visibility below the minimum I’m not qualified to talk about that case.
In the Cirrus if the speed is right and the plane trimmed properly there is no “ballooning” when you set full flaps. In my experience that will happen when you’re too fast.
This is an idea of the kind of visual reference we are talking about. In fact given you can see the PAPIs it is better than some limiting approaches I have seen and the darkness actually makes it slightly easier to see.
It also has the advantage of a full CAT III lighting system which adds a lot of useful depth to the sight picture.
Now try it with CAT I lighting, runway edge lights and no centreline lights.
Yes. In really low vis, you would, upon reaching the DH, see nothing but possibly one diffuse light on the left and one on the right (possibly), with no spatial orientation yet at all.
One would then just continue to fly the glide and loc for a few seconds until you see more lights and maybe some contours on the ground / tarmac. It’s one thing one can practice well in a simulator.
One could make a final configuration change at that time, but I wouldn’t do it, since you will be no more than 50-100 feet above the ground!
So yes I would either arrive at the DH with full flaps or with half flaps and then land this way. If you are conscious about the partial flap situation, it is not a problem; just don’t flare excessively.
Flying ILSs in minimum visibility conditions really has very little to do with “being below the clouds or not”.
The key to an approach in marginal visibility/cloud conditions is that it must be stabilised. No speed or configuration changes below a predefined altitude, and maintain that speed and configuration until the flare.
This is the accepted practice. You are on an ILS runway for low visibility type conditions, so no need for a performance landing in your typical light GA aircraft.
At minimums you typically only see the lead in lights (and in the US the rabbit) and I was accustomed to keep things stable until you established the side bar lighting of the runway environment giving you a ‘visual’ horizon. To descend below 100’ ATDZE the following FAR applies.
FAR 91.175 states that an aircraft may continue an approach below DH without the runway in sight, if the aircraft has the approach lights in sight “…except that the pilot may not descend below 100 feet above the touchdown zone elevation using the approach lights as a reference unless the red terminating bars or the red side row bars are also distinctly visible and identifiable.”
This article is quite helpful on visual cues at minimums.
https://rickstrack.wordpress.com/ricks-blog/
On take off I would use Class B criteria. Most light twins may not have the net take off flight path performance to overcome obstacles in the departure path, so the minima needs to allow for visual manoeuvring around close in obstacles, in effect at one airfield I used for IFR departures requiring at least 600’ ceiling and 2 miles visibility. In a single engine I would want sufficient ceiling and visibility to carry out an EFATO, probably a minimum of 2 miles visibility.
The NTOFP planning exercises using airdrome obstacle charts used to be routine. Climbing one engine inoperative from a low ceiling to 1,500’ in most piston twins is a ten mile plus exercise, which is quite sobering. You are allowed multi engine climb gradient until IMC, when the assumption is made of an engine failure. Hence departing in higher ceilings makes the NTOFP planning easier.
