A pilot flying through the clouds on an instrument approach can break out below the clouds and see the runway, have the required visibility, but still be unable to safely and legally land on the runway. In addition to having the visibility and runway in sight, the pilot also is required to make a ‘normal‘ landing.
WHAT YOU SEE IN THE END
When you fly an ILS approach and are skilled enough to follow the electronic glide slope all the way down, you end up at a position where the runway is laid out in front of you. The airplane’s position should end up aligned with the runway centerline and with the perfect height to fly from the decision altitude to touchdown. Getting in that position was the whole purpose of flying the instrument approach in the first place. But not all instrument approaches lead you to such a perfect position. Many approach and most all non-precision approaches lead you to a position over or near the airport and its up to the pilot to do the rest.
THE VIEW FROM THE VOR…
Take a non-precision VOR approach where the VOR station is located on the airport property. The approach would require that the pilot fly inbound to the station on a particular radial while descending to the Minimum Descent Altitude (MDA). Station passage over the VOR would be the Missed Approach Point.
Let’s say that the pilot descends and levels off at the MDA before reaching the station and is still in the clouds. Then, only moments before reaching the station, the airplane breaks into an opening in the clouds. The pilot looks straight down and sees the airport below. The pilot definitely has the ‘runway environment‘ in sight and can determine that there is the required visibility — but, rather than having the runway out in front of the airplane, it is underneath the airplane. Can the pilot make a legal and safe landing from here?
…AND THE VIEW FROM THE REGS
The regulation that requires the pilot to see the ‘runway environment‘ and the required visibility, also requires that pilot make a ‘normal’ approach and landing. The rule, 91.175(c)(1) says that a pilot cannot fly below an MDA or decision altitude unless the aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal maneuvers. If you pop out of the clouds and the threshold of the intended runway is both behind you and below you, it will be hard — if not impossible — to get to a landing position using anything that would be considered ‘normal.’ Of course the word normal for Part 91 pilots is not further defined, but its probably one of those things that ‘you know it when you see it.’
Danger: It can be very frustrating to actually see the airport just to be forced to make a missed approach anyway. You may have been flying for several hours through rough IFR conditions and are very anxious to get down. You might be very tempted to cut, dive and steep turn back and around to land.
But remember, just because you see a runway does not mean that you can land on it.
The three conditions necessary to land an airplane through IFR conditions are:
- Pilot must see at least item that constitutes ‘runway environment’
- Pilot must determine that the required flight visibility is present
- Pilot must be in a position to make a normal approach and landing
These three stipulations apply to each and every instrument approach.
AND ONE MORE THING
Some approaches have one more rule attached: the Visual Descent Point (VDP). When there is a VDP it is indicated on the profile (side) view of the instrument approach chart with the letter ‘V.’ The VDP is a radio navigation fix along the instrument approach — it can be a GPS or DME position, or could be passage of a VOR or NDB station. When a VDP is present, the pilot must stay at or above the Minimum Descent Altitude (MDA) until passing the VDP even if all the other descent requirements are met.
How It Works: Say you are inbound on an approach that has a VDP. You start your descent and — much to your surprise — you break out of the clouds high above the ground and well above the MDA. The VDP position is still ahead of you but you look ahead and you see the runway even though you are still several miles out. At this moment you can see the ‘runway environment.’ If you can see the runway from this far out you certainly have the required visibility, and you would have no problem positioning for a normal landing — so since all those requirements are met, you can start your descent below MDA… right? Wrong!
The requirement of the VDP says that you must remain at or above the MDA — even though all the other requirements have been met until you have passed the VDP — then you can start down. Why: The VDP is used to keep aircraft as high as possible as long as possible. It is used when the approach must cross over populated areas that are sensitive to aircraft noise, or over areas with ‘hidden’ hazards like towers. The VDP will create a steeper approach that is closer to the airport.
When a VDP is present, the pilot has four — not three — stipulations to meet prior to landing through IFR conditions.