Bascuela

Now we all know to go below the MDA we need to be in a continuous position to make a normal landing. I’ve always taught that we you go visual (or the hood comes off) that you should level off and maintain that altitude until you can make a continuous descent to landing. This has always worked for me because students tend to go below MDA still at midfield downwind. Also, this works because you’re usually only at 500 – 700 feet HAA. Now for the question. What is your opinion of a MDA that over 1000’ HAA or even 1500’ HAA. From a LEGAL standpoint should you maintain that MDA until you can make a continuous descent (in other words no level off) to the runway. That can be tricky sometime because you might break out and still be 2 miles from the airport and really just want to set yourself up for a VFR pattern. I told my student this idea and I’m not sure if it is legally correct. I told my student that if he goes visual above TPA for the airport to descend to TPA and then level off until you begin a normal descent to land. Sounds good to me – but can one LEVEL off once going below the MDA for landing. Again legally speaking – not real world. – Thanks

mistarose

My interpretation has always been that if you descend below MDA and level off at TPA, that is perfectly fine - as long as while in level flight at TPA, you still fulfill all of the requirements needed to descend below MDA in the first place. Good question, I am interested to hear what others say.

undflyboy06

If the question pertains to descending from a high MDA to TPA, which is below the MDA, before you are in a normal descent to land, then I'll have to disagree with that technique.

The main reason for a MDA is to guarantee you obstacle clearance during a non precision approach. I've been trying to remember for the life of me on how much obstacle clearance a NDB or VOR approach guarantees you, but I can't remember. Maybe one of you two will know.

Anyway, let's say that you are doing a non-precision approach to an airport that you are not familiar with. The weather is a little higher then the minimums, but visibility isn't the best. For this instance, the MDA is 2000 ft msl (1200 ft AGL), and the traffic pattern is 1600 ft msl (800 ft AGL). For this situation the MDA for the approach is higher then the TPA. Now, you start the approach and start descending down to your MDA. You are around 3 miles from the airport when you break out at your MDA. You see the airport and determine that you meet all the criteria in 91.175, so you decided to descend down to TPA to set up for a normal landing. You are 2 miles from the airport at TPA when all of a sudden your right wing makes contact with a construction tower.

By descending below the MDA, you were not guaranteed your obstacle clearance. I always thought that the TPA would assure you obstacle clearance when you are within 1/2 from the airport. That's why whenever you do a NPA, you always calculate a VDP even if the approach doesn't have one, so you're able to determine if you're able to make a normal descent to land or not.

As for circling approaches, I've never like those. They only guarantee you 300 ft obstacle clearance WHEN you are within the prescribed range for your aircraft category. Remember, the FAA does not take into account density altitude, and increase in true airspeed during circling approaches for their distances like ICAO does. There have been plenty of accidents when aircraft have struck obstacles on circling approaches because the aircraft had traveled outside the protected zones due to their turn radius increasing from higher density altitudes.

sigep_nm

If you are visual you should be able to SEE the construction tower. The MDA is designed to protect you from obstacles that you would not be able to see because you are in the clouds, vis, etc. As to you point of density altitude, your true airspeed only increases slightly. The FAA also doesnt take into account wind, which is going to affect your groundspeed much more than density altitude. You are reaching out a little bit too much. Also assuming that you are coming from UND, you probably have very little experience in dealing with increased density altitude, other than what you heard from you ground school teaching or instructor, who is sitting in about the same boat as you are.

undflyboy06

It is true about the lack of higher density altitude flying, since I've only taken off and landed with around 4000 ft density altitude. I just thought that leaving a MDA was not safe due to obstructions, but you are right. If you are visual you should be able to see and avoid obstructions, hopefully.

POPA

If you're going to be entering the traffic pattern from the IAP, there's nothing wrong with descending to TPA. 91.175 allows for a "normal rate of descent using normal manuevers." I don't know about you guys, but I'm normally at traffic pattern altitude before I get to the traffic pattern. Flying at a higeher MDA until at the MAP and then leveling off qualifies as an ABnormal maneuver, in my book.

sigep_nm

Flyboy,
I read my post later and maybe I may have come across too harsh. Did not intend to come off that way. You are atleast considering the effects of density altitude which is good, but it is not that noticeable in this phase of flight as far as TAS and GS. Im not sure what POPA is getting at with his post as it makes little sense with his last statement as he has probably never done a circle to land approach.

FlyJSH

Take a look at this approach:
http://204.108.4.16/d-tpp/0611/05402LD.PDF

It is a LOC that is alligned with runway 27R, but is NOT considered straight in due to a high MDA. If the GRIGG FM is available, MDH is roughly 1150; without the FM, MDH is roughly 2300! One MUST decend below MDA somewhere prior to turning final to land on 27R (runway most often favored due to wind).

Consider a catagory 2 aircraft flying at 120 kts, max bank angle 30 degreees, and max VSI 1000 fps. To descend from 2300 agl takes at least 2.3 minutes and nearly 5 nm. Counting back from touchdown zone 5 mn and staying within 1.5 miles of the runway (circling protected area Cat 2) one must leve MDA somewhere around crosswind. Even at MDH of 1150, one must start down roughly on downwind abeam touchdown zone.

POPA

The original question was, "What is your opinion of a MDA that over 1000’ HAA or even 1500’ HAA. From a LEGAL standpoint should you maintain that MDA until you can make a continuous descent (in other words no level off) to the runway."
My answer is no, because the FAR in question allows for "normal manuevers," which would include going below MDA to enter the pattern at TPA. The way I read the question, he was asking about entering a VFR pattern from an IAP. Of course, I'm not an FAA guy, so I could be wrong.
As far as questioning my experience, I'm not sure how you can do that given that you don't know what my experience is.

Texandrvr

It sounds like some are mixing IFR and VFR procedures. FAR 91.175 are IFR procedures and a circling approach is an IFR approach. Do not think that once visual you are then cleared to do what you would under VFR. You are required to maintain MDA until "...in a position from which a DESCENT to a landing...at a NORMAL RATE of descent using normal maneuvers..." In the abnormal situation that a circling MDA is above the TPA then you should not descend to TPA unless you cancel IFR and the tower clears you to continue VFR. They are only going to do that if they have you visually.

Someone mentioned Required Obstruction Clearances for various approaches.

ROC circling = 300'
ROC VOR/DME = 250'
ROC NDB = 300'
ROC ILS = variable