What is PDP?

[a&p cfiguy]

Interview question, what is PDP? Some kind of departure procedure? Please help!

 

[jrav8tor]

Interview question, what is PDP? Some kind of departure procedure? Please help!

Without looking it up....

PDP- Precision Descent Point. Calculation used to determine a point from the runway where one can descend on a 3 degree glideslop when on a non-precision approach. You calculate this prior to the approach so you can realize when you are at this distance and still don't see the runway environment, you will realize any descent after this will be steeper than 3 degrees.

You calculate it by dividing the Height Above Touchdown (HAT) by 300. EX:

HAT

200/300 = .666 This is the distance from runway you will need to begin descent to
remain on 3 degree glipepath.

300/300= 1
400/300= 1.3

so on and so on.

Hope this helps.

JR

 

[Lostdog65]

(Smart aleck answer)

Push the button on your Garmin 530...it'll do the math for you!

Sorry...couldn't resist!

Eric

 

[geshields]

PDP = Pre Departure Pee!!

 

[Occam's Razor]

Without looking it up....

PDP- Precision Descent Point. Calculation used to determine a point from the runway where one can descend on a 3 degree glideslop when on a non-precision approach. You calculate this prior to the approach so you can realize when you are at this distance and still don't see the runway environment, you will realize any descent after this will be steeper than 3 degrees.

You calculate it by dividing the Height Above Touchdown (HAT) by 300. EX:

HAT

200/300 = .666 This is the distance from runway you will need to begin descent to
remain on 3 degree glipepath.

300/300= 1
400/300= 1.3

so on and so on.

Hope this helps.

JR

Sounds a lot like the "VDP"... or Visual Descent Point.

I think PDP is ___________ Departure Procedure. Aren't they published at airports that don't have a 10-3 series of SID's, but do have a preferred instrument departure?

 

[tracearabians]

Pdp

Pretty Damn Prepostorous !

 

[a&p cfiguy]

is it precision descent procedure? what is that?

 

[IflyaBoeing737]

Who gives a Crap?

 

[FL420]

Interview question, what is PDP? Some kind of departure procedure? Please help!

The PDP is a Planned Descent Point. It is calculated by the pilot before executing a non-precision IAP so the pilot will know(based on either time or DME) when he must begin descent from the level segment MDA before the MAP in order to fly a stabilized 3.0 degree(approximately 300 feet per NM) approach path to the runway to be able to touchdown in the touchdown zone. It does not take into account obstacles that may or may not penetrate into the approach plane.

If the pilot reaches the PDP and does not have the required visual cues in sight he can fully expect to have to execute a missed approach at the MAP. If he catches sight of the runway environment after passing the PDP he should know that an attempt to descend and land would require an unstabilized approach with a low power setting and an excessive rate of descent or a landing beyond the touchdown zone, or both.

If the MAP is based on time, divide the HAA(or HAT if available) of the MDA by 10. Subtract the result(in seconds) from the time it takes to fly from the FAF to the MAP. The result is the time it takes to fly from the FAF to the PDP.

If the MAP is based on DME, again divide the HAA(or HAT if available) of the MDA by 300. Subtract the result(in NM) from the total distance from the FAF to the MAP. The result is the distance from the FAF to the PDP.

The FAA does not officially recognize the PDP. I will let you read what the AIM says about Visual Descent Points(VDP's.)

f. Visual Descent Points (VDPs) are being incorporated in nonprecision approach procedures. The VDP is a defined point on the final approach course of a nonprecision straight-in approach procedure from which normal descent from the MDA to the runway touchdown point may be commenced, provided visual reference required by 14 CFR Section 91.175(c)(3) is established. The VDP will normally be identified by DME on VOR and LOC procedures and by along-track distance to the next waypoint for RNAV procedures. The VDP is identified on the profile view of the approach chart by the symbol: V.

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.

1. Pilots are cautioned that descent to a straight-in landing from the MDA at the MAP may be inadvisable or impossible, on a nonprecision approach, even if current weather conditions meet the published ceiling and visibility. Aircraft speed, height above the runway, descent rate, amount of turn and runway length are some of the factors which must be considered by the pilot to determine if a landing can be accomplished.
2. Visual descent points (VDPs) provide pilots with a reference for the optimal location to begin descent from the MDA, based on the designed vertical descent angle (VDA) for the approach procedure, assuming required visual references are available. Approaches without VDPs have not been assessed for terrain clearance below the MDA, and may not provide a clear vertical path to the runway at the normally expected descent angle. Therefore, pilots must be especially vigilant when descending below the MDA at locations without VDPs. This does not necessarily prevent flying the normal angle; it only means that obstacle clearance in the visual segment could be less and greater care should be exercised in looking for obstacles in the visual segment. Use of visual glide slope indicator (VGSI) systems can aid the pilot in determining if the aircraft is in a position to make the descent from the MDA. However, when the visibility is close to minimums, the VGSI may not be visible at the start descent point for a "normal" glidepath, due to its location down the runway.
3. Accordingly, pilots are advised to carefully review approach procedures, prior to initiating the approach, to identify the optimum position(s), and any unacceptable positions, from which a descent to landing can be initiated (in accordance with 14 CFR Section 91.175(c)).

b) Visual Descent Point (VDP). A VDP will be published on most RNAV IAPs. VDPs apply only to aircraft utilizing LNAV minima, not LPV or LNAV/VNAV minimums.

 

[FN FAL]

Pretty dang Prepostorous !

I thought it stood for Please Don't Pay4training?