IFR

Precision vs non-precision

• precision approaches:
  • using DA: ILS, PAR
• non-precision approaches:
  • using MDA: NDB, VOR, LOC, LNAV, ASR
  • using DA: APV (approach with vertical guidance), including LNAV/VNAV, LPV, LDA+glidepath

Note: APV approaches provide vertical guidance but don't meet the ICAO and FAA precision approach definitions, which apply mostly to localizer and glideslope transmitters.

Frequently used approaches

• ILS/LOC
• LPV:
  • Localizer Performance With Vertical Guidance.
  • NOT considered precision approaches.
  • Requires WAAS, which provides 7.6 meters or better accuracy.
  • usually get you down to 200 ft above touchdown.
  • if you're using an airport with LPV only as your alternate airport, you need weather minimums that meet the LNAV or circling MDA
• LP
  • similar to LPV but without vertical guidance, the GPS equivalent of a LOC approach
  • WAAS equipment is mandatory for LP.
• LNAV:
  • no vertical guidance, complete with step-down altitudes.

Not so frequently used approaches

• LNAV/VNAV: Lateral Navigation/Vertical Navigation
  • the final approach course is linear the entire way to the runway (like LNAV), decreasing to 0.3 NM sensitivity when you're within 2 miles of the final approach fix, all the way to the missed approach point.
• PAR: Precision approach radars (precision) are used by air traffic controllers to issue guidance to pilots during final approach using radio. These are precision approaches similar to the ILS approach. PAR uses primary radar. It does not require any onboard equipment. (ILS is part of the standard aircraft equipment) The use of PAR in civil aviation has been constantly diminishing.
• ASR: Surveillance Approach (non-precision): ATC provides lateral guidance to you using radar to monitor your position. ATC gives you a series of headings and corrections to align your final approach with the runway's extended centerline.
  • ASR approaches use Terminal Radar, which means you can only get coordination for these approaches from an Approach Controller, not a Center or Tower Controller. (You won't talk to the tower, but will talk to an approach controller all the way to the ground.)
• LDA: Localizer Directional Aid.
  • like a localizer, except it's not aligned with the runway. Used in places where terrain or other factors prevent the localizer antenna from being aligned with the runway that it serves.
  • uses the same equipment as a standard localizer.
  • e.g. Honolulu (PHNL) LDA RWY 26L
• NDB

RNP vs RNAV

RNP (Required Navigation Performance) is a type of RNAV, but with requirements:

• RNP must include onboard performance monitoring and alerting capability (i.e. RAIM); it will alert the pilot when the accuracy degrades.
• RNP must meet a specified accuray at least 95% of the flight time.

LPV vs LNAV/VNAV vs LNAV

	LPV	LP	LNAV/VNAV	LNAV
GPS + WAAS	Yes	Yes	Yes	Yes
GPS + Baro-aiding			Yes	Yes
GPS				Yes

Baro-aiding: Barometric aiding is an integrity augmentation that allows a GPS system to use a non-satellite input source (e.g. the aircraft pitot-static system) to provide vertical reference and reduces the number of required satellites from five to four.

Baro-aiding satisfies the Receiver Autonomous Integrity Monitoring (RAIM) requirement in lieu of a fifth satellite.

V vs +V

The V in LPV, LNAV/VNAV is the "approved vertical guidance".

The +V in LNAV**+V** is the "advisory vertical guidance". Provided by GPS manufacture. "+V" is never shown on a chart. With +V, pilot can fly a constant descent to the MDA (otherwise need to step down).

Load vs Activate an approach

• Loading an approach: Adds the approach procedure to the end of the flight plan, but the GPS will still navigate to the destination airport.
• Activating an approach: Changes the next navigational fix to a fix in the approach procedure.

Request practiced approach

ME: request practiced approach Stockton ILS 29R with published missed, vector to final

ATC: heading 270, maintain 2,000 until established, cleared ILS 29R approach

Visual approach vs Contact approach vs Instrument approach

• Visual approach: ceiling >= 1000 ft; visibility >= 3 sm.
• Contact approach: the pilot may deviate from the published instrument approach procedure (IAP) and proceed to the destination airport by visual reference to the surface.
  • Similar to a visual approach, but do not need the airport in sight; 1 sm visibility; the airport must have a published instrument approach.
  • ATC can't initiate a contact approach, you have to ask for it.
  • there's no missed approach procedure
• Instrument approach: fly the published instrument approach.

What is "VFR on top"?

"VFR on top" is a flight status that allows a pilot to fly above a cloud layer while maintaining an Instrument Flight Rules (IFR) flight plan. It allows the pilot to select a VFR altitude instead of the assigned one, which can be helpful when flying above or between cloud layers.