Checking Localizer
A localizer can be checked for accuracy by departing a runway served by that localizer. Tune to LOC frequency while taxiing and note CDI movement as you move on to runway. CDI should center as you line up on runway centerline. This will not work at CCR 19R except at the very end of the runway due to offset. VOR frequencies end with an even decimal: .2, .4, .6, etc. Localizer frequencies end with an odd digit: .1, .3, .5 etc.

VOR Approaches
Item: VORs with HIWAS do not have two-way communications.
Accuracy
--91.25 Requires 30 day check of VOR accuracy before IFR use.
--Use of VOT give zero From or 180 degrees To with allowable error + 4 degrees.
--Ground checkpoints in AF/D +4 degrees
--Airborne checkpoints in AF/D +6 degrees
--Dual VOR check within 4 degrees
--VOR idents in a series of four followed by DME ident.
--VOR deflection is 10-degrees from center to side
--Any time dual VORs have a common problem it is probably the shared antenna

On a VOR approach, the VOR can be located at:
--Airport
--Missed approach point
--Initial approach fix
--Final approach fix or
--Miles from the airport.

VOR Minimums
Fewer options for the VOR and NDB than for the ILS. Some non-precision approaches lower the minimums when light systems exist. The MDA boxes do not include DA(H). Circle to land minimums are based on HAA elevation as shown on the right side of the chart. Numbers in parentheses are Heights Above airport (HAA). Radius of the circle for category A aircraft is 1.3 nm. The speed you fly determines the aircraft category. If there is no speed/time chart then timing is not authorized.

Straight-in-minimums require three things:
1. Runway alignment within 30-degrees
2. Approach must cross threshold
3. Descent to be less than 3.77 degrees or 400' pnm.

Off Airport Facility
The course is aimed at the airport reference point.

On Airport Navaid
The final course is aimed at the navaid but will intercept the runway centerline optimally at 3000' from threshold for circling. Straight-in is aimed at the threshold.

VOR is four times laterally less accurate than an ILS localizer. This means that every 1 degree of a VOR has a built in it an error. The error is easily computed by taking the distance from the VOR in nautical miles and adding two zeros.

Consider that a VOR is allowed up to six degrees of error (airborne) to either side of a course line. Take a VOR distance such as CCR at 3.1 miles from the airport. This is about 300' error per degree. A full 6 degree error would amount to missing the end of the runway by 1800'. This does not include possible pilot error such as a 1-2 degree error in setting the OBS.

Pilots should never fly anything other than the course radial on the OBS. You should look to left and right of your course for the airport. How far to each side you look would depend on the distance between the airport and the VOR. You never track an incorrect radial in anticipation of possible equipment error. Use Airman's A/F Directory to determine useable directions and altitudes of all navaids. CCR VOR can fly you into Mt. Diablo from the southeast.

Suggestion: Use ADF "0" position to set altitudes assigned by ATC.

Intercepting a Radial
--Along an airway a 45 degree intercept
--On approach use 30 degrees
--10 degrees maximum on the ILS and use rudder for 5 degree corrections

In some instances a greater than 30-degree arrival may not require a hold. The FAA may design an approach where the hold is so removed from the final approach fix (5 nm) that sufficient time for course alignment exists.

VOR Checks
There are 6 ways a VOR can be pilot checked for errors:
--VOT
--Ground check point
--Dual VOR check
--Radio shop check
--Designated airborne check
--Homemade" check

Every VOR has a dedicated monitoring system where other navaids may or may not be monitored. Monitors check the signal and any required accuracy on a status panel with alarms and lights. Unmonitored navaids cannot be used to meet alternate requirements of IFR flight and are noted in the A/FD either with and N/A on an approach plate or with a ‘tower closed' note. The pilot who is using an unmonitored navaid for an actual approach had better maintain a constant listening watch on the frequency and flags.

ADF Features
The NDB approach is designed to have protected minimum obstacle clearance is 300 feet vertical and 1.25 miles wide at the facility. A formula is used to determine the protected space as the missed approach point which amounts to 6000' wide per mile. You have 30 degrees angular space, 15 degrees to each side, to miss the runway and still have protected airspace. The PTS standards allow only 10 degrees bearing error to the approach course.

Low frequency radio 200-1600 KHz with both loop and sense antennas. Not limited to line-of-sight but by power. HH power good for 200 miles down to compass locator or locator outer marker (LOM) at 15 miles.

The ADF course is the intended magnetic flight direction. When ATC directs you to fly with reference to an NDB they will always give a bearing from or to the station. The to or from may be either way by ATC while meaning the same thing. If you are in doubt as to ATC intentions reverse the term and direction used by ATC and ask for confirmation.

I usually teach the NDB/ADF procedure with the azimuth card fixed at "0". Using this method the magnetic bearing can be read by mentally superimposing the ADF needle on to the heading indicator. The FAA written test uses problems that require use of the formula MB=RB+MHs. This means that to find the magnetic direction to the NDB to add the relative bearing to your magnetic heading. The math involved in this procedure when flying can be avoided by rotating the azimuth card. ADF needles always move into the wind. When holding an approach heading the needle will point toward the course line.

Rotating the azimuth card makes the ADF into a pseudo Radio Magnetic Indicator (RMI) without the remote compass. In the RMI the azimuth card rotates automatically. With the ADF you must set the card to the desired magnetic heading. The heading selected in the course line + the predicted wind angle. You are trying to get the tail of the needle to indicate the approach course line. When the tail of the needle indicates to the right of the course line you will turn to the right for about 30 seconds before returning to the WCA heading. Works the same if the tail moves to the left. Once you have turned the card it is best to leave it alone unless you have grossly misjudged the WCA.

Items:
---When NDB is used to form airway the magnetic bearing from the NDB is used to form the radial.
--An unused ADF is likely to get needle problems
--Not all ADFs use two antennae.
--Check an ADF malfunction by going to ANT mode (Some needles will 'stow' at 90 degrees.)

Non Directional Beacon Approach
The secret to flying the off airport NDB approaches is: after station passage turn to the final approach course and maintain that course for at least 30 seconds, despite what the needle is telling you. Keeping this lesson in mind should make flying NDB approaches much simpler in the future. The NDB approach is generally considered one of the tougher items on the flight test for the instrument rating. If you asked a bunch of instrument-rated pilots to list their favorite approach equipment, you'd probably get a list something like this: #1 ILS. #2 LOC only (no glideslope), #3 VOR, and #4 NDB

Continue To Next Page