Why is LPV not considered precision approach

In discussing this with the FAA, it has to do with LPV not meeting technical requirements in ICAO Annex 10. This is as clear as mud. One difference between ILS and LPV, is the way they fail with GS and therefore the accuracy and minimums of the no GS available fail down. With ILS, when the GS fails, the localizer with its precise lateral guidance generally has a lower MDA for the localizer only option and 600-2 in the vast number of approaches is at or above the localizer only minimums. With LPV, the fail down is to LNAV and the LNAV lateral guidance is not as precise as the LPV lateral guidance, so the LNAV procedure (a non precision approach) is used for the purposes of determining the weather criteria (800-2). Of course in some cases, even the 600-2 or 800-2 is not at or above the localizer or LNAV minimums, in which case, special alternate minimums will either be assigned for the procedure or the procedure will not be authorized to be used for an alternate.
 
MauleSkinner said:
John, where is this documented?
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FAAO 8260.19H, paragraph 2-4-5 discusses the various monitoring categories and how they apply to establishing alternate minimums.

That's a behind-the-scenes determination, though, what a pilot cares about is what is in the Alternate Minimums section of the approach charts, if they are not standard.

For example, if an ILS is monitored in the tower, and the tower is not a 24-hour facility, the Alternate Minimums will read "NA when control tower closed".

Most VORs are monitored at the regional level at a centralized control center, so you usually won't see this kind of note on a VOR procedure. You will sometimes see it on an NDB procedure, but most often it will be on an ILS (or Loc-only)
 
RussR said:
FAAO 8260.19H, paragraph 2-4-5 discusses the various monitoring categories and how they apply to establishing alternate minimums.

That's a behind-the-scenes determination, though, what a pilot cares about is what is in the Alternate Minimums section of the approach charts, if they are not standard.

For example, if an ILS is monitored in the tower, and the tower is not a 24-hour facility, the Alternate Minimums will read "NA when control tower closed".

Most VORs are monitored at the regional level at a centralized control center, so you usually won't see this kind of note on a VOR procedure. You will sometimes see it on an NDB procedure, but most often it will be on an ILS (or Loc-only)
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Ok...that makes sense...I’ve seen the “operational” side of it in the “Alternate Minimums, but never seen the general documentation. I thought maybe I fell asleep before I got to it in the AIM or something. ;)
 
From 8260.19H CHG 1 04/26/2018 SUBJ: Flight Procedures and Airspace

2-4-5. Monitoring of navigation facilities.
a.Monitors. It is FAA policy to provide a monitoring system for all electronic navigationfacilities used in support of instrument flight procedures. Internal monitoring is provided at the facility through the use of executive monitoring equipment that causes a facility shutdown when performance deteriorates below established tolerances. A remote status indicator may also be provided through the use of a signal-sampling receiver, microwave link, or telephone circuit. VOR, VORTAC, and ILS facilities as well as new NDBs and marker beacons installed by the FAA, are provided with an internal monitoring feature. Older FAA NDBs and some non-Federal NDBs do not have the internal feature and monitoring is accomplished by other means.
b.Monitoring categories. Navigational facilities are classified in accordance with themanner in which they are monitored.
(1)Category 1. Internal monitoring plus a status indicator installed at control point.Reverts to a temporary category 3 status when the control point is unmanned/monitoring not available.
(2)Category 2. Internal monitoring with status indicator at control point inoperative, butpilot reports indicate the facility is operating normally. This is a temporary situation that requires no procedural action.
(3)Category 3. Internal monitoring only.
(4)Category 4. Internal monitor not installed. Remote status indicator provided at controlpoint. This category is applicable only to nondirectional beacons.

2-4-6. Utilization of monitoring categories.

a.Category 1 facilities may be used for instrument flight procedures without limitation.
b.Category 2 is a temporary condition not considered in instrument procedure development.The ATO is responsible for issuing NOTAMs on these out-of-service facilities when pilot reports indicate facility malfunction.
c.Category 3 facilities may be used in accordance with the following limitations:
(1)Alternate minimums must not be authorized if facility provides final approach course(FAC) guidance; is required for procedure entry; is used to define the final approach fix (FAF); or is used to provide missed approach guidance [see also paragraph 8-6-11.b].
(2)Consider denying or adjusting terminal routes that require reception of succeedingcategory 3 facilities to avoid obstacles.
(3)Dogleg airways or routes must not be predicated on these facilities.
(4)Navigational fixes developed from crossing radials of category 3 facilities must notbe used to break a MEA to higher MEA (can be used as a break to a lower MEA).
d.Category 4 facilities may be used in accordance with the following limitations:
(1)Alternate minimums may be authorized when the remote status indicator is located inan FAA ATC facility, and then only during periods the control point is attended.
(2)If the control point is other than an FAA facility, a written agreement must existwhereby an ATC facility is notified of indicated changes in facility status.
Note: Failure of this category 4 status indicator or closure of the control point will render the facility and the approach procedure unusable during the outage.
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MauleSkinner said:
John, where is this documented?
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It's explained in the Instrument Procedures Handbook, but that's sort of a statement of fact.

Officially, the guidance is in FAA order Flight Procedures and Airspace 8260.19H (which is referred to in the TERPS as well).
 
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RussR said:
Hah! Just don't rely on it as a current source of information - there have been a ton of changes in both documents in the last 10 years.
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I would be interested who can read 8260.58A except for TERPs-type computer programmers.
 
RussR said:
Hah! Just don't rely on it as a current source of information - there have been a ton of changes in both documents in the last 10 years.
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No doubt. I deal daily with the 8900.1, which I swear I've seen content change over my lunch break.
 
tspear said:
I am curious how much is transmission lag vs computing lag; especially with how much computing capacity has continued to push forward. I wonder how much the time delta is legacy thought process vs modern reality.
Considering the impact speed with the runway on a cat 2/3 landing; and the plane is in a stable approach, what is an "acceptable" error time and how does that affect the landing height?

Tim
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Not sure. I'm sure it's a pretty technical answer. Nevertheless, the "Wide Area" nature of WAAS suggests that certain technical compromises were made to provide the maximum functionality with a limited amount of cost. Eventually WAAS will be replaced by an upgraded GPS satellite constellation that provides WAAS-like accuracy and integrity without augmentation.
 
MauleSkinner said:
Do the trolls come into your house at night and hide things on you, too? ;)
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If by trolls you mean my wife constantly throwing stuff out or putting stuff away while I'm in the middle of using it? Then yes.

The other morning my wife and I were in the kitchen making our own breakfasts. I went to the cupboard to retrieve a bowl, and then to the pantry to retrieve my box of cereal. After swinging by the silverware drawer for a spoon and the fridge for the milk, I returned to my spot to find an empty table. Turns out my wife thought I was done and put the cereal back in the pantry and my bowl in the sink. Sigh.
 
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Brad Z said:
If by trolls you mean my wife constantly throwing stuff out or putting stuff away while I'm in the middle of using it? Then yes.

The other morning my wife and I were in the kitchen making our own breakfasts. I went to the cupboard to retrieve a bowl, and then to the pantry to retrieve my box of cereal. After swinging by the silverware drawer for a spoon and the fridge for the milk, I returned to my spot to find an empty table. Turns out my wife thought I was done and put the cereal back in the pantry and my bowl in the sink. Sigh.
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If you get up to go in the middle of the night does she make your side of the bed? :D
 
Larry in TN said:
I've flown the GLS approaches at both EWR and IAH. Works just like an ILS. I've never had the opportunity to fly an LPV.
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If you aren't flying a GA plane, you won't fly an LPV. I think only like 2% of the air carrier fleet is LPV capable, and even those don't use it.
 
Brad Z said:
If by trolls you mean my wife constantly throwing stuff out or putting stuff away while I'm in the middle of using it? Then yes.

The other morning my wife and I were in the kitchen making our own breakfasts. I went to the cupboard to retrieve a bowl, and then to the pantry to retrieve my box of cereal. After swinging by the silverware drawer for a spoon and the fridge for the milk, I returned to my spot to find an empty table. Turns out my wife thought I was done and put the cereal back in the pantry and my bowl in the sink. Sigh.
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My wife would go further and put the bowl in the dishwasher.

Tim
 
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