Instrument Approach Question

Beechlover

Beechlover

Well-Known Member
Been studying and haven't gotten a definate answer on this situation Mainly aimed at 121/135 operators

Lets say your in IMC conditions established on the final approach course of an CAT I ILS at the published glide slope intercept altitude approaching glide slope intercept (FAF) when tower advises you that RVR/Visibility just went below published mins. What do you do?

My answer: Because I haven't reached Glide slope intercept, I can't descend on the GS so I stay at my present altitude or climb to my missed approach altitude while continuing on the approach heading until I reach my MAP then execute the missed approach to a hold or an alternate.

Side question: How does one Id the MAP on a precision approach when one has not descended on the GSbased on the above situation? DME indicates when your over runway threshold? What if you have no DME? Time? or Middle marker?

Now the "flip" side to this situation is if I was already established on the GS when the vis dropped below mins I would simply continue the approach to the DH, and if/when I didn't have the required visual references I would simply fly the missed.

Same two situations can be applied to a non-precision approach except replace GS intercept with FAF and DH for MDA

Just would like to do the sanity check on that to make sure I understand.

Thanks everybody.., Ok enough studying, gettin a beer outa fridge.., so long 2007! It's been the best year of my life and I wanna thank everybody here cause I darn sure wouldn't be here if wasn't for ya'll! LOL!

HAPPY NEW YEAR!!! CHEERS! :nana2:
 
First question, you answered yourself correct (at least in Part 135). If the vis is not at or above mins, you may not continue the approach. However, you would not just start climbing (since you are obviously talking to approach) but just inform approach you cannot shoot the approach and advise them of your intentions.

If you were beyond the FAF, then yes you may continue the approach but must have the applicable mins to be able to land.

Side question, most precision approaches (ie ILS) also have published LOC MAP. Should you somehow become lost comm, after approach just told you the airport was below mins, use that fix, be it time or DME, as your MAP. That is when you would go ahead and climb to missed altitude.
 
*transmission*

*OM - - - - - - -*

"Blocked...was that for ___?" :D

Seriously now...part 91, I'll go take a look. 135 I'm out of options...I'd prefer to hold at the marker/FAF if I can that way I'm 1st in line when the wx goes back up.

-mini
 
Thanks guys, I really appreciate it. Trying to gear up for interview process, hopefully will be firing off the resumes tomorrow! Happy New Year!
 
Remember that the approach is predicated on FLIGHT VISIBILITY.

So let's say you're inside the marker and tower calls visibility of 1200/1000/1000. You legally continue to descend and as you reach DA you see the rabbit.

Exercising 91.175/121.651 you elect to continue your descent to 100 feet above TDZE at which point you see the terminating bars and you continue to landing.

Can you be violated?

The answer is no. Even though you technically landed "below minimums" the simple answer to the industrious Fed would be, "We had adequate flight visibility".

How do you know? Tell him you were able to see the threshhold at minimums. (Approach lighting systems used in conjunction with precision approaches are normally 2400 feet long.)

I'm not advocating cheating or going below minimums or pushing a bad situation. I'm simply suggesting that we use the FARs to the extent possible to complete the approach safely and legally IF the flight visibility is indeed adequate.
 
I had intended to put the Part 121 reference for you in my post above. Here ya go.

FAR 121.651

(c) If a pilot has begun the final approach segment of an instrument approach procedure in accordance with paragraph (b) of this section and after that receives a later weather report indicating below-minimum conditions, the pilot may continue the approach to DH or MDA. Upon reaching DH or at MDA, and at any time before the missed approach point, the pilot may continue the approach below DH or MDA and touch down if --
(1) The aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal maneuvers, and where that descent rate will allow touchdown to occur within the touchdown zone of the runway of intended landing;
(2) The flight visibilityis not less than the visibility prescribed in the standard instrument approach procedure being used;
 
ZapBrannigan said:
I had intended to put the Part 121 reference for you in my post above. Here ya go.

FAR 121.651

(c) If a pilot has begun the final approach segment of an instrument approach procedure in accordance with paragraph (b) of this section and after that receives a later weather report indicating below-minimum conditions, the pilot may continue the approach to DH or MDA. Upon reaching DH or at MDA, and at any time before the missed approach point, the pilot may continue the approach below DH or MDA and touch down if --
(1) The aircraft is continuously in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal maneuvers, and where that descent rate will allow touchdown to occur within the touchdown zone of the runway of intended landing;
(2) The flight visibilityis not less than the visibility prescribed in the standard instrument approach procedure being used;
Click to expand...


This is EXACTLY what I was looking for Thanks ZAP! Happy New Year!
 
ZapBrannigan said:
Remember that the approach is predicated on FLIGHT VISIBILITY.

So let's say you're inside the marker and tower calls visibility of 1200/1000/1000. You legally continue to descend and as you reach DA you see the rabbit.

Exercising 91.175/121.651 you elect to continue your descent to 100 feet above TDZE at which point you see the terminating bars and you continue to landing.
Click to expand...

Continuing to land is predicated on flight visibility. To begin the approach for 121/135 the vis or RVR must be above mins prior to begining the approach. And then as ZAP said you can land depending on the flight vis.

Now I doubt a controller will call out an RVR reading below mins just before you reach the FAF on the approach. Unless you ask for it a half mile from the FAF (which would be a dumb move).
 
Yes, I certainly didn't mean to imply that if you are 135/121 you can even START an approach unless they're reporting better than minimum visibility (ceiling doesn't matter).
 
dbrault17 said:
Now I doubt a controller will call out an RVR reading below mins just before you reach the FAF on the approach. Unless you ask for it a half mile from the FAF (which would be a dumb move).
Click to expand...

The good ones won't....but there was one lady in the tower at BGM when I was based there that would always report it as you were approaching the FAF..grrrrr.... But in her defense, she was just trying to be helpful.
 
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