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General Questions

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FAA Regulations, General Aviation, Instrument Rating

Hi, I have a couple of questions that I cant find a exact answer with proof (FAR/AIM). 1. What is the boundary of a DME arc (left and right)? 2. Previous aircraft went missed, can you shoot an approach? Why? 3. The required visibility to shoot an approach is 1/2 the previous aircraft (shooting the approach) reported 1/4 vis can you still shoot/continue the approach? 4. What is an example of viscous hydroplaning? 5. What is the terrain clearance on a circle to land? 6. What is the terrain clearance at the end of the runway? (my understanding is 35ft feet at the fence is required performance) 7. What is the limit to start a turn after departure? (400ft?) 8. What is adequate visual range for TO? Thanks in advance

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3 Answers

  1. Best Answer


    John D Collins on Mar 30, 2014

    Lots of questions.

    1. A DME arc primary protected area is as wide as an airway, +/- 4 NM. Pilots are expected to maintain +/- 1 NM from the arc. References 8260.3 TERPS, Instrument rating PTS.

    2. and 3. Part 91 operator do not have any restrictions on visibility requirements in order to attempt an approach, however, they must have the required minimum flight visibility to descend below the MDA or DA and to land. Reference FAR 91.175.

    4. Viscous hydroplaning occurs on a very flat surface such as the touchdown area on a runway that has accumulated rubber from landings. When this area gets wet, it takes very little water for viscous hydroplaning to occur. A grooved runway eliminates this possibility in most cases. Dynamic hydroplaning can still occur but requires more standing water.

    5. Typical circling obstacle and terrain clearance is 300 feet. Reference 8260.3 TERPS

    6, 7., and 8. Read the AIM section 5-2-8, it will answer these questions. I will leave this as an assignment for you to accomplish.

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  2. aeropilot on Mar 30, 2014

    Hi thanks for the info,

    regarding the 2nd and 3rd questions I forgot to mention its from the 121 side of things. I know they need to follow the min vis published on the plate, but if the previous aircraft reports a lower vis would that be recognized as the new vis and the 121 aircraft would have to execute a missed?

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  3. Fr8dog on Mar 31, 2014

    The answers are both NO; they may continue the approach to MDA/DH (in the US).

    First of all, pilots are NOT accredited weather observers and the observation, while of interest to following airplanes, has no real effect on the approach.

    Second, if you’re inside the final approach fix, you may continue to MDA/DH (again in the US), regardless of reported weather.

    Finally, visibility is a prevailing condition of the Airport area and NOT runway specific and thus local conditions (such as fog) may affect a portion of the reporting area, but not be of sufficient coverage to be included in the reported visibility.

    NOTE: Some foreign countries (UK) require a go-around ANYTIME the reported weather goes below minimums for the approach,

    Hope this helps !

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