VDP's

[TVB]

Got a question for you guys about VDP's. The question is can you descend below the MDA before the VDP if you have the airport in sight. I have conflicting information on this answer. Everything Explained says a pilot may descend below the MDA prior to the VDP only where a descent to the runway can not be made using normal procedures or rates of descent if the final descent is delayed until reaching that point. The other source is the King Jeppeson chart review. It says that the VDP is not mandatory and you can descend below the MDA as long as you have the airport in sight.

Can anyone clarify this for me, thanks

[tgrayson]

Originally Posted by TVB

Got a question for you guys about VDP's. The question is can you descend below the MDA before the VDP if you have the airport in sight. I have conflicting information on this answer. Everything Explained says a pilot may descend below the MDA prior to the VDP only where a descent to the runway can not be made using normal procedures or rates of descent if the final descent is delayed until reaching that point. The other source is the King Jeppeson chart review. It says that the VDP is not mandatory and you can descend below the MDA as long as you have the airport in sight.

Can anyone clarify this for me, thanks

VDP's are not regulatory for Part 91 operations. However, the AIM says that if you can detect it, then you should use it. It says:

1. VDPs are intended to provide additional guidance where they are implemented. No special technique is required to fly a procedure with a VDP. The pilot should not descend below the MDA prior to reaching the VDP and acquiring the necessary visual reference.

2. Pilots not equipped to receive the VDP should fly the approach procedure as though no VDP had been provided.

Again, this is not regulatory.



For Part 121, it is regulatory:

14 CFR 121.651(c)
...
Upon reaching DH or at MDA, and at any time before the missed approach point, the pilot may continue the approach below DH or MDA if either the requirements of § 91.175(l) of this chapter, or the following requirements are met:

When the aircraft is on a straight-in nonprecision approach procedure which incorporates a visual descent point, the aircraft has reached the visual descent point, except where the aircraft is not equipped for or capable of establishing that point, or a descent to the runway cannot be made using normal procedures or rates of descent if descent is delayed until reaching that point.

[SpiraMirabilis]

Originally Posted by TVB

Got a question for you guys about VDP's. The question is can you descend below the MDA before the VDP if you have the airport in sight. I have conflicting information on this answer. Everything Explained says a pilot may descend below the MDA prior to the VDP only where a descent to the runway can not be made using normal procedures or rates of descent if the final descent is delayed until reaching that point. The other source is the King Jeppeson chart review. It says that the VDP is not mandatory and you can descend below the MDA as long as you have the airport in sight.

Can anyone clarify this for me, thanks

You can descend below the MDA if you have the prerequisites (91.175) met. If you descend after the VDP you're not necessarily guaranteed hitting the touchdown zone, as you could go past it. It's a point where a 3.00 degree descent angle (normal descent) will get you to the touchdown zone.

The VDP is the last point where you can make a "normal", stabilized, descent and if you don't have it in sight you should probably think about going missed. To say that you can't descend below it is not really true. So long as you have the runway environment in sight in line with 91.175 you can descend below MDA. Additionally, saying that would make one try to aim for the VDP before considering descending which might make someone blow past it, when as soon as they get past it they're no longer using a normal descent. I consider the VDP to be the end of my descent envelope, not the beginning of it.

[SpiraMirabilis]

Or I could be totally wrong, apparently.

[TonyC]

Originally Posted by tgrayson

. . . the AIM says . . .


. . . 14 CFR 121.651(c) . . .

Why do you have to take a perfectly good thread and end it with an answer from "The FARs"?



Don't you think these authors and marketers should get a little more respect?








.

[TVB]

I think that was what I was confused with. Difference between part 91 and part 121. Thanks

[SpiraMirabilis]

tgrayson: on the 121 part:

Upon reaching DH or at MDA, and at any time before the missed approach point, the pilot may continue the approach below DH or MDA if either the requirements of § 91.175(l) of this chapter, or the following requirements are met:

Would that mean that you wouldn't necessarily need to detect/use the VDP if they already have the requirements of 91.175(l) met?

[tgrayson]

Originally Posted by SpiraMirabilis

tgrayson: on the 121 part:

Would that mean that you wouldn't necessarily need to detect/use the VDP if they already have the requirements of 91.175(l) met?

That would be my reading of it. But 91.175(l) has to do with enhanced vision systems; apparently those include some sort of pseudo-glideslope type functionality. Perhaps someone here who has flown with those will speak.