pdp

[icehockey]

Just a few random questions...

1. Can anyone tell me what a pilot descent point is, how it differs from a VDP, and when you would want to calculate one?
2. Why do some non-precision approaches have VDPs and others don't? Wouldn't you always want to leave MDA at a 3 degree glidepath? Someone told me the calculations regarding VDPs have something to do with displaced threshold placement and calculations regarding MAPs have something to do with the landing portion of the runway. Does anyone know how they are calculated and if this is true?
3. Also, I have seen on some IAPs "ILS Y" or "ILS Z." What do the letters mean?
4. Re: circling approaches-- What is the distance requirement (i.e. how far out from the runway are you alllowed to make your pattern)? Within one mile? Is this a suggestion or a limitation, and if it is a limitation, where do I find this rule in the regs?
Why are some approaches A and some B or C?
Circling only mins published when course is not aligned w/in 30 of runway-- I also heard they are published on a second condition that has to do with the location of the VOR. Does anyone know what this second condition is? (If anyone has FL plates, why is
VOR/DME-A a circling only approach? The final app course is 182 and the runway is 17/35.)
5. Why do they have localizer back course approaches? Is there some reason they could not install a front course beam?
6. Re: 91.175. Say you lose glideslope on an ILS (you are not DME equipped), but you remembered to start time at the faf just in case. You are on gs, below loc mins (not yet to dh) and just passed faf (with time running), and then you lose gs. Can you just jump back up to mda and proceed to the map for localizer, or must you immediately execute missed? On a related not, since missed on an ILS is needles centered at DH, if you lose gs (either gs malfunction or crappy pilot technique), do you immediately add full power, start climbing, and go the MAP, or direct to the navaid before initiating missed? And on a non-precision app, if you go full scale deflection before map, what would be the initial steps to take going missed?

Thanks

 

[avbug]

Only some approaches are predicated on a three degree glide path. In reality, terrain and obstacles, as well as the runway itself, often mean that a different glide angle is required.

VDP and glide angle and calculated based on the particular needs of a particular specific approach with regards to obstacle clearance criteria and other factors.

Circling approach area radii are calculated based on approach speed, and vary with the approach category. View AIM Figure 5-4-9for specifics. No, it's not one mile. Even the lowest category, Category A, has a radius of 1.3 miles.

Must you stay within this distance. You mustn't do anything. However, obstacle clearance criteria, most especially considering your circling MDA, is based on this radius, and you'd do well to stay within it.

A very good policy is to use the next highest category any time one is operating near the upper limit of a category.

If you are below localizer-only minimums and you lose glide slope, execute a missed approach. Do not climb back to the MDA and attempt to salvage the approach. You may remember some primary instruction in which your instructor hopefully told you not to try to salvage a landing. Don't do that with an approach, either. Go missed.

If you're still above MDA, you may continue at MDA and finish the approach as a nonprecision approach. However, you shouldn't attempt to do this unless you're fully prepared, briefed, and familiar with both proceedures.

Today, it's generally accepted that if you lose a component, you'll go missed, rebrief, and try it again as a different approach. While loss of the electronic glideslope doesn't change the name of the approach (ie, it's still called an ILS), the reality is that it 's a new and different approach for you. Fly it as such. Climb as prescribed until the MAP, execute the missed proceedure, and come back to try it again.

 

[icehockey]

Thanks for the info-- I appreciate it.