Quantcast Non-Precision Approach (VOR, TACAN, NDB, VOR/DME, LDA, SDF, GPS/RNAV, LOC, and LOC BC)


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Page Title: Non-Precision Approach (VOR, TACAN, NDB, VOR/DME, LDA, SDF, GPS/RNAV, LOC, and LOC BC)
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Steering Commands. Most approaches in the training syllabus are flown without the use of the
flight director. However, if using pitch and bank steering commands supplied by the flight
director system, monitor flight path (CDI and GSI) and aircraft performance instruments to ensure
the desired flight path is being flown and aircraft performance is within acceptable limits. A
common and dangerous error when flying an ILS on the flight director is to concentrate on the
steering bars and ignore flight path and aircraft performance instruments.
Crosscheck. Maintain a complete instrument crosscheck throughout the approach, with increased
emphasis on the altimeter during the latter part (DH is determined by the barometric altimeter).
Establish a systematic scan for the runway environment prior to reaching DH.
Decision Height. Do not descend below localizer minimums if the aircraft is more than one dot
(half scale) below or two dots (full scale) above the glide slope. If the glide slope is recaptured to
within the above tolerance, descent may be continued to DH. At DH, the decision must be made
to either continue the approach or to execute a missed approach. If executing a missed approach,
the aircraft will dip slightly below DH while transitioning to a climb. If continuing for a landing,
review the landing checklist complete prior to touchdown.
Non-Precision Approach (VOR, TACAN, NDB, VOR/DME, LDA, SDF, GPS/RNAV, LOC, and
All non-precision approaches are flown using similar procedures, although NAVAID
characteristics differ. After radar approaches, non-precision VOR, TACAN, and NDB approaches
are introduced next in the training curriculum; in part this is because they require an "easier"
crosscheck (they have no precision glideslope and have "less precise" course guidance than the
localizer). However, one thing should be abundantly clear: once on any approach, minimum
terrain clearance has to diminish (you are descending to land); as it does, the importance of precise
altitude management becomes increasingly crucial. On non-precision approaches inside the FAF,
minimum obstruction clearance at the MDA can vary from 200' on LOC, VOR, and TACAN
approaches to 300' on NDB approaches. Couple this with a possible altimeter error of up to 75'
and it should be easy to see the need for precise altitude control.
CAUTION: The rate of CFIT (controlled flight into terrain) accidents during non-precision approaches is five
times that of precision approaches. Another interesting note is most major airlines do not even allow their pilots to
fly non-precision approaches without approval. In the military, however, we routinely fly into many locations where
a non-precision approach is the only option.
Transition to the Final Approach Course. Again, perform by using either radar vectors or a
published approach procedure.
Final Approach. The final approach starts at the FAF and ends at the MAP. The optimum length
of the final approach is five miles; the maximum length is ten miles.
Navigation receiver. Once the aircraft is inside the FAF, at least one navigation receiver must
remain tuned to and display the facility providing final approach course guidance. For example, if
only one VOR receiver is operable, that receiver cannot be re-tuned inside the FAF to another
VOR station identifying subsequent stepdown fixes and/or the MAP.
Localizer signal. The localizer signal typically has a usable range of at least 18 miles within 10 of
the course centerline unless otherwise stated on the IAP. ATC may clear you to intercept the
localizer course beyond 18 miles or the published limit, however, this practice is only acceptable
when your aircraft is in radar contact and ATC is sharing responsibility for course guidance.
Identifying the FAF. The FAF is indicated on the IAP with a Maltese cross. Looking for multiple
ways to identify the FAF provides for backup in case the primary method fails. The FAF may be
defined by an outer marker [or other NAVAID such as a compass locator (LOM), VOR, or NDB]
or by a DME fix. Radar may be substituted for an outer or middle marker if it is published on the
IAP. Crossing radials may also be used if published on the IAP; this method should be used with
discretion unless it is the only method available, because it precludes the copilot from backing up
primary course guidance until reaching the fix.

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