Instrument regulations

9 Answers

1. 
   

   
   

   Wes Beard on Aug 07, 2012

   Hi Oren… good questions.

   The regulations require 15 hours with a CFII, the other 25 hours are not defined so you can fly with a safety pilot if you wish. I wouldn’t advise it as it takes some practice getting comfortable flying solely by instruments. There are things the CFII knows the safety pilot (or CFI) may not know.

   If the reported visibility is below minimums, as a Part 91 operator, you can continue passed the final approach fix and take a look to see if you see one of the 10 required items to continue below DA/MDA. If you are a Part 121 / 135 operator, you must execute a missed approach at the FAF if you receive a weather report below minimums before crossing the FAF. If the weather deteriorates, and is received after crossing the FAF the Part 121/135 operator may continue the approach.

   +1 Votes 2 Votes  1 Votes

2. 
   

   
   

   Lucas on Aug 08, 2012

   Yes Wes is correct in both cases.
   For question #2 the key is “flight visibility”: RVR is a “ground visibility” taken from a Transmissometer, which uses a laser beam to determine such visibility, and again this is a “ground visibility” not a flight visibility, which can only be determined by the pilot.
   So can you continue passed the FAF? Yes.

   Can you continue below MDA/DA? Yes, If you have one of the following in sight: the approach light system, except that the pilot may not descend below 100 feet above the touchdown zone elevation using the approach lights as a reference unless the red terminating bars or the red side row bars are also distinctly visible and identifiable.
   (ii) The threshold.
   (iii) The threshold markings.
   (iv) The threshold lights.
   (v) The runway end identifier lights.
   (vi) The visual approach slope indicator.
   (vii) The touchdown zone or touchdown zone markings.
   (viii) The touchdown zone lights.
   (ix) The runway or runway markings.
   (x) The runway lights.

   Can you land? Yes if the FLIGHT VISIBILITY is still at least the one prescribed for the approach. Let’s say the minimum RVR for the approach is 2400 and the runway you are landing on is 6000 feet. If you can see half of the runway, than you can land.

   Lucas
   http://passfaaexams.com/

   +3 Votes 3 Votes  0 Votes

3. 
   

   
   

   John D. Collins on Aug 08, 2012

   Lucas,

   If you are flying an a three degree descent path, and see half of the runway, at the location where you are still at 200 feet above the runway, the visibility would have to be over 7000 feet to see half of the runway. In fact, if the flight and reported visibility is equivalent to RVR 2400, on an ILS or LPV with a 200 foot DH, you won’t be able to see the threshold at the DA because it will be over 3000 feet away. This is why the approach lights are required and the exception that allows you to continue to 100 feet above the threshold is in 91.175. At 100 feet above the threshold, you will be 1500 feet from the threshold and should be able to make it out with RVR 2400. The red terminating bars or the red side row bars are only used with ALS-1 or ALS-2 approach lighting systems that are predominately used at the major airports used by the airlines. Most GA airports use MALSR or MALSF approach lighting systems and don’t have the red bars.

   +2 Votes 4 Votes  2 Votes

4. 
   

   
   

   Bob Watson on Aug 08, 2012

   While it’s important to know (and follow) the regulations, I would point out that venturing down for a “look-see” (descend to the DH/MDA when the weather is reported to be below minimums) is an accident-prone maneuver that requires considerable proficiency and judgment to survive.

   On an ILS, for example, the DH is typically 200′ AGL. So, think for a second… If you decide to go down for a look-see, you’ll be making that decision in the soup with only 200′ between you and the terrain (that is hopefully near the runway). To be legal (and remotely safe) you need to determine the flight visibility and make the decision to continue or go-around quickly. While it might sound reasonable in theory, in practice, when you’re just 200′ away from the airport after a long trip, it can be very tempting to cheat (just a tiny bit, after all, you’re almost there…)

   Also, consider what you’ll do even if you are able to land in such low visibility. 1/2-mile visibility means you won’t see much of the runway and could get lost just exiting the runway (which you’ll do on a taxiway, hopefully). Some airports are set up better than others for taxiing around in low visibility.

   Whether or not it’s a good idea to start an approach when the airport is reported to be below minimums depends on many factors such as local knowledge of the airport, terrain, weather patterns, your skill and proficiency, your fatigue, your other options (e.g. fuel, weather), etc. Just remember there’s not much margin for error at 100 or 200′ AGL.

   0 Votes 0 Votes  0 Votes

5. 
   

   
   

   Lucas on Aug 08, 2012

   John
   When I said land I meant touch down. Operation below MDA/DA was described on point 2 Can I operate below MDA/DA so once you are on the runway to legally touch down you need to see just about half the runway if the RVR required was 2400 and the runway was 6000 feet. So I repeat to legally touch down you need to see half the runway. If at the DA you can see the runway environment but all of a sudden it disappears because of, lets say a bank of fog, than you need to discontinue because of the loss of Flight Visibility.

   And Bob I agree 100% with what you are saying is it legal? Yes. Is it sane? NO.
   But the question concerned legality of the issue. Had the question asked: “should I” well than the answer is no.

   Cheers Lucas

   +3 Votes 3 Votes  0 Votes

6. 
   

   
   

   Bob Watson on Aug 09, 2012

   I like the “%-runway” estimate of flight visibility. (It makes perfect sense, I just had never heard it stated like that).

   Around here in the Pacific N.W., we are lucky to have actual IMC that illustrate much of what has been discussed here. If you can get a lesson on such a [miserable] day, it’s quite a eye-opener!

   For example:

   Flying an approach to 200′ ceiling and 1/2 mile visibility and seeing just how low to the ground that is and how little of the runway you can see!

   Entering the above approach in severe clear (i.e. above the tops).

   Flying in and out of scud on your way to the airport and not letting that distract you or your instrument scan.

   These experiences (and others) are way different than flying around under the hood. At least our weather is good for something 🙂

   +1 Votes 1 Votes  0 Votes

7. 
   

   
   

   John D. Collins on Aug 09, 2012

   Lucas,

   Continuing our discussion, I agree that you will see approximately half of a 6000 foot runway if the visibility on the ground is at the minimums. However, it is legal to be below the DA/MDA if the flight visibility is at or above the approach minimums. For a pat 91 operator, unlike a 135 or 121 operator, the approach is permitted if the reported visibility is below the minimums as flight visibility, as determined by the pilot, is controlling. That doesn’t make it a wise thing to do.

   Assuming an approach at 90 KTS and a DH of 200 feet, you have approximately 25 seconds to the threshold. Having determined at the DA that the flight visibility meets the approach requirements as evidenced by having one or more of the required cues, and having maintained the cues as being distinctly visible and identifiable to the pilot, there is no additional requirement for touching down on the runway.

   Of course if you lose the flight visibility before touching down, you have to execute a missed approach. Estimating the visibility by the percent of the runway visible can be problematic when airborne. You don’t have the benefit of seeing the full runway as a comparison, so you have to use something else, for example a known taxiway or the runway markings. The latter are not likely to be visible at night. This is easier to do when you are stopped and on the ground, but more difficult to do moving at approach speed.

   In my own flying, if I made the decision to continue the approach below the DA and kept the required cues in sight, I would not conduct an additional estimate of the flight visibility based on how much of the runway I saw, as I would be concentrating on landing the airplane, and it would be totally legal.

   0 Votes 2 Votes  2 Votes

8. 
   

   
   

   Lucas on Aug 09, 2012

   John

   “there is no additional requirement for touching down on the runway. ”

   91.175 sub part (d) says: Landing

   touch down phrasal verb

   Definition

   When an aircraft touches down, it lands.

   Landing is the last part of a flight, where a flying animal, aircraft, or spacecraft returns to the ground.

   (d) Landing. No pilot operating an aircraft, except a military aircraft of the United States, may land that aircraft when—

   (1) For operations conducted under paragraph (l) of this section, the requirements of (l)(4) of this section are not met; or

   (2) For all other part 91 operations and parts 121, 125, 129, and 135 operations, the flight visibility is less than the visibility prescribed in the standard instrument approach procedure being used.

   Now when I am landing my eyes are only focusing on the runway and not on the approach light system which is probably behind me already . Plus focusing on the runway might allow me to actually land on it rather than on the grass.

   Again I say “this is the legal side of the question. The sane thing to do would be to go and land somewhere else. There is no reason to do something stupid like this”. As a matter of fact I always tell my students that after they get the license and fly alone always add 3-400 feet to any MDA. If they want to practice to minimums or below go rent an hour or 2 of simulator time.

   Cheers again
   Lucas

   +2 Votes 2 Votes  0 Votes

9. 
   

   
   

   John D. Collins on Aug 09, 2012

   Lucas,

   We have a different interpretation of the regulations. 91.175(d)(1) doesn’t apply to the discussion unless you have an enhanced flight vision system. 91.175(d)(2) restates that you may not land if the “flight visibility” is less than the visibility prescribed in the standard instrument approach procedure being used. Flight visibility is determined solely by the pilot and is not ground visibility.

   I don’t have a problem with you recommending that a student be cautious and increase their personal minimums, but if they are proficient they should be able to conduct an approach to minimums. At minimums of 200 and 1/2 on an ILS, at the DA, it is unlikely that you will be able to see the threshold and will have to depend on a working and visible approach light system to guide you close enough to see the runway. That is why when the approach lights are out, the visibility requirement usually increases to 3/4 of a mile, or there would be no way to complete the approach legally or safely.

   A standard instrument approach is designed to be safe by the FAA standards, but it does require the pilot to maintain proficiency. Landing at minimums is more challenging than popping out at 1000 feet and spotting the runway with 3 miles to go, but both are safe. Continuing below the DA or MDA when you don’t have the required flight visibility is not safe and is likely to result in an accident.

   +3 Votes 5 Votes  2 Votes