VDP and going missed before MAP on Non precision approach.

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John777

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Are we allowed to continue beyond VDP, holding my MDA on altimeter until I see the runway environment ?

Also, most of the non precision approach MAP starts at runway threshold, I will be looking up for more information in FAA order(TERPS) but anyone has idea why FAA established MAP at runway threshold?

Lastly, If I do not see the one of the visual reference for the runway, can I start climbing even before reaching MAP?

John.
 
As far as I know, a published VDP is just that. You cannot descend below that even if you have a visual on the field. It will still put you on a glide path but stop you from descending early possibly due to obstructions.

Someone correct me if I'm wrong.
 
Yes

There are lots of Missed Approach Points that are not at the threshold. I think most of the ones that show it right there are ones that don't have a fix to define it but use time to define it. The solid black line changing to the dashed line, indicating the beginning of the Missed Approach segement, is pretty much just an illustration.

Yes. Unless there is a restriction that requires you to keep descending. This wouldn't be the case of course if you were at MDA, but there are some Approaches that require you to keep descending if you decide to miss "early."
 
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Yes you can continue the approach beyond the VDP and still land. The VDP is a just a reference point and doesn't change how you actually fly the approach. All it's telling you is the point on the MDA that when reached AND the necessary visual reference has been established a "normal" descent will result in a landing. The issue of going beyond the VDP when visual reference has not been established is the farther you go past the VDP and closer to the MAP the less likely a safe approach (ie one without excessive descent rate and/or bank angle) to landing can be executed.

As to executing the missed before reaching the MAP, yes you can although in practice you'd drive all the way to the MAP at MDA if the only issue with the approach was the lack of acquisition of the runway environment. Typically there would be other issues with the approach and/or aircraft that would drive a decision to go missed earlier than the MAP.
 
Kritchlow said:
As far as I know, a published VDP is just that. You cannot descend below that even if you have a visual on the field. It will still put you on a glide path but stop you from descending early possibly due to obstructions.

Someone correct me if I'm wrong.
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I'm not necessarily disagreeing (although the question deals with descending after the VDP and not before) but I will point out that aside from obstruction issues, the goal of a VDP is to provide a point from which one can make a "normal" 3 degree +or- stabilized final approach to the runway as opposed to a dive or helicopter drop at the MAP.

From that perspective I can't see anything inherently wrong with breaking out of the clouds at 900 AGL shortly after the FAF with unlimited visibility below and starting down even if it's before the VDP.

Anyone got an FAA reference on this one?
 
midlifeflyer said:
I'm not necessarily disagreeing (although the question deals with descending after the VDP and not before) but I will point out that aside from obstruction issues, the goal of a VDP is to provide a point from which one can make a "normal" 3 degree +or- stabilized final approach to the runway as opposed to a dive or helicopter drop at the MAP.

From that perspective I can't see anything inherently wrong with breaking out of the clouds at 900 AGL shortly after the FAF with unlimited visibility below and starting down even if it's before the VDP.

Anyone got an FAA reference on this one?
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AIM 5-4-5 h. It says "should" and gives lots of good ideas why it's inherently maybe not a good idea, if not illegal.
 
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midlifeflyer said:
From that perspective I can't see anything inherently wrong with breaking out of the clouds at 900 AGL shortly after the FAF with unlimited visibility below and starting down even if it's before the VDP.
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I've never seen anything that makes a VDP binding in any way. It is simply a reference. So I agree that it may not be a good idea, but also agree that it isn't wrong. Having said that, I usually feel low enough at the MDA that I don't think I'd be comfortable going lower until I was at least in the vicinity of the VDP.
 
luvflyin said:
AIM 5-4-5 h. It says "should" and gives lots of good ideas why it's inherently maybe not a good idea, if not wrong.
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Yeah I know the reasons, and they absolutely make sense at night or with low visibility, but, given equivalent conditions, it's a bit difficult for me to picture a common VFR day procedure done by pilots with no idea what a VDP is as "wrong."
 
midlifeflyer said:
Yeah I know the reasons, and they absolutely make sense at night or with low visibility, but, given equivalent conditions, it's a bit difficult for me to picture a common VFR day procedure done by pilots with no idea what a VDP is as "wrong."
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I hear ya. My grammar and punctuation misled my point. I wasn't implying doing it was wrong. I was noting that AIM 5-4-5 h. didn't make it wrong.
 
luvflyin said:
I hear ya. My grammar and punctuation misled my point. I wasn't implying doing it was wrong. I was noting that AIM 5-4-5 h. didn't make it wrong.
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I think the point you made was correct as is, the AIM blurb and other FAA pubs like the info @Velocity173 linked "suggest" there is something wrong with it. I
 
BTW, the Part 121 rule, 121.651 has reaching the VDP as one of the alternative requirements for descent from the MDA, and even then, it's subject to "but"s and "if"s. So even in that very heavily regulated environment it's not a pure "must."


(c) If a pilot has begun the final approach segment of an instrument approach procedure in accordance with paragraph (b) of this section, and after that receives a later weather report indicating below-minimum conditions, the pilot may continue the approach to DA/DH or MDA. Upon reaching DA/DH or at MDA, and at any time before the missed approach point, the pilot may continue the approach below DA/DH or MDA if either the requirements of §91.175(l) of this chapter, or the following requirements are met:

***

(4) 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.​
 
midlifeflyer said:
From that perspective I can't see anything inherently wrong with breaking out of the clouds at 900 AGL shortly after the FAF with unlimited visibility below and starting down even if it's before the VDP.
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Well, you can always cancel IFR.

The last question has a much more straightforward answer. Do not start the missed approach before the MAP. You'll turn earlier, and there may be terrain or obstructions. On some VOR approaches, you can tootle along at the MDA for miles.
 
midlifeflyer said:
BTW, the Part 121 rule, 121.651 has reaching the VDP as one of the alternative requirements for descent from the MDA, and even then, it's subject to "but"s and "if"s. So even in that very heavily regulated environment it's not a pure "must."
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It's pretty much a must. VDPs aren't published unless either a DME fix or RNAV WP is available. Air carrier aircraft are always equipped for the VDP. It's difficult for a 121 pilot to argue that the VDP didn't place him in the "slot" so to speak.

Nonetheless, charted VDPs are purely advisory for Part 91 operators.
 
aterpster said:
It's pretty much a must. VDPs aren't published unless either a DME fix or RNAV WP is available. Air carrier aircraft are always equipped for the VDP. It's difficult for a 121 pilot to argue that the VDP didn't place him in the "slot" so to speak.

Nonetheless, charted VDPs are purely advisory for Part 91 operators.
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Does 135 have a rule about it?
 
MAKG1 said:
Well, you can always cancel IFR.

The last question has a much more straightforward answer. Do not start the missed approach before the MAP. You'll turn earlier, and there may be terrain or obstructions. On some VOR approaches, you can tootle along at the MDA for miles.
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You will not turn earlier if you do it correctly. If the missed approach has turns you must continue to the MAP prior to beginning those turns. You can start the missed approach anytime before that.
 
"If the missed approach is initiated prior to reaching the MAP, unless otherwise cleared by ATC, continue to fly the IAP as specified on the approach chart. Fly to the MAP at or above the MDA or DA/DH before beginning a turn."
--Instrument Flying Handbook.

MAKG1 said:
Well, you can always cancel IFR.

The last question has a much more straightforward answer. Do not start the missed approach before the MAP.
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False. You must be trying to win an award for most disinformation ever posted by one person.
 
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Nearly any field with an instrument approach is way more than long enough for the Navion even if I started the descent from the MDA over the threshold. VDPs are handy when flying less agile aircraft.
 
dmspilot said:
"If the missed approach is initiated prior to reaching the MAP, unless otherwise cleared by ATC, continue to fly the IAP as specified on the approach chart. Fly to the MAP at or above the MDA or DA/DH before beginning a turn."
--Instrument Flying Handbook.



False. You must be trying to win an award for most disinformation ever posted by one person.
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So, just which part are you disagreeing with? Flying to the MAP at or above MDA is exactly equivalent to not starting the missed approach before the MAP. It's unusual to climb during a final approach segment, but it's perfectly legal unless there is a maximum altitude you might bust. Turning early, on the other hand, is not acceptable.

There are many places where an early climb will put you in conflict with other traffic. It's not always clear above.
 
flyingron said:
Nearly any field with an instrument approach is way more than long enough for the Navion even if I started the descent from the MDA over the threshold. VDPs are handy when flying less agile aircraft.
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Or faster aircraft. I've noticed more benefit from the vdp when in something with high approach speeds.
 
MAKG1 said:
So, just which part are you disagreeing with?
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Your response to OP is neither "straightforward", and according to your definition of a missed approach, does not answer his question.

John777 said:
Lastly, If I do not see the one of the visual reference for the runway, can I start climbing even before reaching MAP?
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MAKG1 said:
The last question has a much more straightforward answer. Do not start the missed approach before the MAP.
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MAKG1 said:
Flying to the MAP at or above MDA is exactly equivalent to not starting the missed approach before the MAP.
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:rolleyes1:

I suppose you wouldn't tell ATC you're going missed, since it's not a missed until you get to the MAP, it's just a climbing final approach segment. :rolleyes1:
 
aterpster said:
It's pretty much a must. VDPs aren't published unless either a DME fix or RNAV WP is available. Air carrier aircraft are always equipped for the VDP.
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Really? Show me where the VDP was displayed in the 121 operated DC-9 I flew...
 
aterpster said:
Air carrier aircraft are always equipped for the VDP.
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Vdp's were around a long time before anything in the cockpit displayed them to the crew. My first 121 job was in 727-200's. Our whole fleet was /A. We did use vdp's. You should find a book called "mental math for pilots" and learn.
 
In all my career we always calculate a VDP as good practice. We also always "understood" that if one is published it was mandatory.

I'm not saying that's Gospel truth, but rather it's the way it's been interpreted by the companies I have flown for.
 
KSCessnaDriver said:
Really? Show me where the VDP was displayed in the 121 operated DC-9 I flew...
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Ya, I agree.. I have never flown anything that calculates a "true" VDP. We could always build one, and some airplanes have a chinsey glide slope indicator for visual conditions, but I've never seen an actual VDP on my MFD.
 
KSCessnaDriver said:
How do you use DME to calculate a VDP on an approach that doesn't have DME....
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You don't. I think we are speaking of charted VDPs. On conventional IAPs charted VDPs have to be a DME fix. On RNAV IAPs charted VDPs have to be a charted waypoint or an ATD fix. If they aren't charted, they aren't required.

See attached for examples of both at Thermal, California.
 

Attachments

  • KTRM Charted VDPs..pdf
    188.7 KB · Views: 9
That's ad hoc and not required for Part 121, unlike a charted VDP.
 
Tarheelpilot said:
True , however, I think it's a good idea to have a idea of where the vdp is for non precision approaches regardless of any requirement to do so or one being published on the plate.
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This is exactly my point. We always calculated them if they were not on the plate, but we always played it as mandatory if they were published.
 
Kritchlow said:
This is exactly my point. We always calculated them if they were not on the plate, but we always played it as mandatory if they were published.
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Same at every 121 & 135 job I've had. I just assumed that was best industry practice. I was questioning the validity of some posts in this thread. Trying to keep an open mind though.....
 
Tarheelpilot said:
True , however, I think it's a good idea to have a idea of where the vdp is for non precision approaches regardless of any requirement to do so or one being published on the plate.
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Absolutely! Obstacle clearance, no but definitely for a more stabilized approach.
 
Interesting thread. My GA flying is limited to simple airplanes these days, so I'm curious - are the more advanced GA planes still diving and driving VOR and LOC approaches?

At work, the VDP has become largely irrelevant since we don't dive to the MDA anymore. We treat the MDA as a DA, so you either see it or you don't once you get there. And yes MAKG1, that means we'll be going missed before the MAP, just no turns before then, I promise! :)
 
Tarheelpilot said:
True , however, I think it's a good idea to have a idea of where the vdp is for non precision approaches regardless of any requirement to do so or one being published on the plate.
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I agree. That's why much of the industry adopted the constant descent angle approach for NPAs a long time ago. Dive and drive for large airplanes has a bad safety record.
 
kayoh190 said:
Interesting thread. My GA flying is limited to simple airplanes these days, so I'm curious - are the more advanced GA planes still diving and driving VOR and LOC approaches?

At work, the VDP has become largely irrelevant since we don't dive to the MDA anymore. We treat the MDA as a DA, so you either see it or you don't once you get there. And yes MAKG1, that means we'll be going missed before the MAP, just no turns before then, I promise! :)
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We're still diving and driving in CRJ's where I work. You don't have to, but most people do it that way. But I can count on one hand the number of times in the last year that I've flown a non-precision approach to anywhere within 500 feet of minimums.
 
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