Welcome Guest. Sign in or Signup

3 Answers

LPV Minima

Asked by: 8587 views ,
FAA Regulations

Hi,

I have a question on LPV minima. Why is it at 250 feet. Why not something else like 300 ft or 200 ft? Basically i want to know the rationale behind 250 ft.

Regards,

Jayant Singh

3 Answers



  1. Kent Shook on Jun 22, 2011

    Only the people who wrote that section of the TERPS will know definitively, but the easy answer is that 250 feet is the lowest they could get while maintaining required obstacle clearances given the resolution of the data given to the pilot (the needles) and the potential errors in that data.
     
    In other words – They decided they couldn’t do 200 feet safely, but they could do 250 feet safely – So why would they round up to 300 feet absent a necessity to do so?

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes



  2. Wes Beard on Jun 22, 2011

    Not all WAAS GPS approaches have a 250 ft lowest minimum.  There are some that can come all the way down to 200 feet.  This approach in Nevada, Missoura has 200ft ceiling and 1sm visibility.
    http://aeronav.faa.gov/d-tpp/1106/05831R2.PDF (If the link no longer works change 1106 to the current yymm)
    I agree with Kent that for whatever reason: obstacle clearance, maximum permissable error on the GPS receiver, missed approach climb gradient and others affects how low the minimums are for that specific approach.

    +1 Votes Thumb up 1 Votes Thumb down 0 Votes



  3. John D. Collins on Jun 22, 2011

    When the first LPV approaches were released, they were limited to a minimum DH of 250 feet.  By the end of 2008, sufficient improvements were made to the WAAS system to allow for lower DH down to 200 feet.  LPV approaches that have a DH 250 feet or higher, have a vertical integrity requirement of +/- 50 meters and those that go lower than 250 feet must meet a tighter vertical integrity of +/- 35 meters.  In order to obtain the lowest minimums currently available for a LPV approach (200 DH and 1/2 mile visibility), several other criteria must be met by the runway.  It must be at least 4200 feet long if I recall.  It must have a parallel taxiway.  The runway needs to have precision markings.  There must be an approved approach light system.  If these conditions are not met, then either the visibility or the DH or both are required to be higher. As of the beginning of this month, there were 470 LPV approaches published that have a DH of 200 feet.   A complete list of the LPV approaches and the DH can be found at http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/approaches/media/LPVs_060211.xls

    +7 Votes Thumb up 7 Votes Thumb down 0 Votes


Answer Question

Our sincere thanks to all who contribute constructively to this forum in answering flight training questions. If you are a flight instructor or represent a flight school / FBO offering flight instruction, you are welcome to include links to your site and related contact information as it pertains to offering local flight instruction in a specific geographic area. Additionally, direct links to FAA and related official government sources of information are welcome. However we thank you for your understanding that links to other sites or text that may be construed as explicit or implicit advertising of other business, sites, or goods/services are not permitted even if such links nominally are relevant to the question asked.