Can you descend below DH or MDA??

[pgcfii2002]

I was reading the requirements for descending lower than the DH and MDA, am I correct to assume you must have:

1) Stabilized approach
2) Runway enviornment in sight
3) Visibility greater than published for the approach

Correct me if I am wrong........

 

[Papps]

I believe published MDAs and DHs are not applicable as long as you "really really don't feel like going missed".

 

[nosehair]

3) Visibility greater than published for the approach

Correct me if I am wrong........

"visibility not less than published..."

 

[neflier]

I was reading the requirements for descending lower than the DH and MDA, am I correct to assume you must have:

1) Stabilized approach
2) Runway enviornment in sight
3) Visibility greater than published for the approach

Correct me if I am wrong........

Actually, you can descend below DH, but not continue below DH. DH is the altitude where a decision is made, continue the approach, or execute a missed. Assuming a 100 kt GS, you have a descent rate of roughly 500 fpm. A decision to go missed at 200’, with a descent rate of 500 fpm will result in the aircraft being below 200’ during the initial part of the missed. Perfectly legal.

No don’t ask what happens if the runway environment comes into sight during the dip below DH. A decision to go missed has already been made and the aircraft is no longer stabilized on the approach. Continue with the missed.

 

[nosehair]

Actually, you can descend below DH, but not continue below DH. A decision to go missed at 200’, with a descent rate of 500 fpm will result in the aircraft being below 200’ during the initial part of the missed. Perfectly legal.

.....(waiting)....3....2....1...

 

[Papps]

.....(waiting)....3....2....1...

Waiting for what, thats correct info. Unless you pull 9 g's at DH you are going below it a few feet. At DH you make the decision to continue based on what you see or go missed.

 

[Amish RakeFight]

Papps is right.

 

[nosehair]

Waiting for what

for what I though might be some flak on that one. I haven't seen that "hashed out" on any of these boards lately...thought there might be some newbies who haven't heard it before, or some oldies (like me) who prefer to read the word "continue" as in "going below DH"...but that's just me. I'm not gonna argue about it, you see it one way, which is plausible, I see it another way, which makes me feel a little safer.

I was waiting on some other viewpoints.

 

[Papps]

yeah this one has confused people forever. If your in jet doing 140 knots on final and 700-800 fpm to hold glide slope. The pilot not flying will call "minimums no runway" right at DH. In the rj you will say hit the TOGA button push the levers up and say "go around go around thrust flaps 8" and pitch up to the Flight director. The plane will be below DH by the time you start uphill again. And no check airman on earth will fail you for that.

 

[A Squared]

for what I though might be some flak on that one. I haven't seen that "hashed out" on any of these boards lately...thought there might be some newbies who haven't heard it before, or some oldies (like me) who prefer to read the word "continue" as in "going below DH"...but that's just me. I'm not gonna argue about it, you see it one way, which is plausible, I see it another way, which makes me feel a little safer.

I was waiting on some other viewpoints.

Well, you're being pretty vague and non-committal here, but reading between the lines, it *appears* that you are advocating beginning a missed approach so as not to go below the Decision Altitude (DA).

If that is not your position, disregard. If that is your position, you are incorrect. By all means, operate how you feel comfortable, heck, add 300 feet to all the MDA's if you like to, but that is certainly *not* how a DA is intended to be used. The name says it all:

DECISION Altitude

It is the altitude at which you make the decision to continue or to go missed. It isn't just some silly meaningless words that were accidentally chosen because they looked cool on the approach plate. Just like "minimum descent altitude means the lowest you are allowed to go, decision altitude means that the altitude at which you decide to execute the missed approach. And of course, when you make the decision to go around at decision altitude, unless you have infinitely quick reflexes and an infinitely powerful airplane, you will go briefly below the DA as the airplane transitions from descent to climb. How much depends on the specifics of the airplane, but it will happen and the system is designed to operate that way.

Like I said, if you like to treat DA as a MDA, knock yourself out, but to say and teach that as the correct method is every bit as factually incorrect as teaching that one should never descend below 300' above the MDA on an non-precision approach.

 

[Mike man]

91.175?

 

[Way2Broke]

§ 91.175 Takeoff and landing under IFR.
(a) Instrument approaches to civil airports.
Unless otherwise authorized by the Administrator, when an instrument letdown to a civil airport is necessary, each person operating an aircraft, except a military aircraft of the United States, shall use a standard instrument approach procedure prescribed for the airport in part 97 of this chapter.
(b) Authorized DH or MDA. For the purpose of this section, when the approach procedure being used provides for and requires the use of a DH or MDA, the authorized DH or MDA is the highest of the following:
(1) The DH or MDA prescribed by the approach procedure.
(2) The DH or MDA prescribed for the pilot in command.
(3) The DH or MDA for which the aircraft is equipped.
(c) Operation below DH or MDA. Except as provided in paragraph (l) of this section, where a DH or MDA is applicable, no pilot may operate an aircraft, except a military aircraft of the United States, at any airport below the authorized MDA or continue an approach below the authorized DH unless--
(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 for operations conducted under part 121 or part 135 unless that descent rate will allow touchdown to occur within the touchdown zone of the runway of intended landing;
(2) The flight visibility is not less than the visibility prescribed in the standard instrument approach being used; and
(3) Except for a Category II or Category III approach where any necessary visual reference requirements are specified by the Administrator, at least one of the following visual references for the intended runway is distinctly visible and identifiable to the pilot:
(i) 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.
(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.
(e) Missed approach procedures. Each pilot operating an aircraft, except a military aircraft of the United States, shall immediately execute an appropriate missed approach procedure when either of the following conditions exist:
(1) Whenever operating an aircraft pursuant to paragraph (c) or (l) of this section and the requirements of that paragraph are not met at either of the following times:
(i) When the aircraft is being operated below MDA; or
(ii) Upon arrival at the missed approach point, including a DH where a DH is specified and its use is required, and at any time after that until touchdown.
(2) Whenever an identifiable part of the airport is not distinctly visible to the pilot during a circling maneuver at or above MDA, unless the inability to see an identifiable part of the airport results only from a normal bank of the aircraft during the circling approach.

 

[Papps]

ok.... alot there. You can't go below MDA and you cant continue the approach below DH. Your not continuing the approach your going missed.

You will go below DH 100% of the time unless you have a JATO bottle. If you want to go missed 50 early to stay above DH than go ahead they will bust you on your type ride because you couldent fly the profile.

 

[A Squared]

ok.... alot there. You can't go below MDA and you cant continue the approach below DH. Your not continuing the approach your going missed.

You will go below DH 100% of the time unless you have a JATO bottle. If you want to go missed 50 early to stay above DH than go ahead they will bust you on your type ride because you couldent fly the profile.

Papps has pretty much nailed it. I wrote a response last night but couldn't post it because of computer problems, so I saved it. Being a cheap-ass pilot I hate throwing things out so I'll post it anyway now:


========================================

91.175?

We need a verb for a complete sentence.





I'm going to take a wild guess and guess that what you mean by 91.175? is really "doesn't 91.175 prohibit descending below the DH?" (If that's *not* what you mean, I have no idea what you mean.)



Well, no it doesn't. Actually the text of the regulation kinda proves the point.



Let's read the relevant part:

".....no pilot may operate an aircraft, except a military aircraft of the United States, at any airport below the authorized MDA or continue an approach below the authorized DH unless...."

Notice that the part addressing DH is worded completely differently than the part addressing the MDA. that should be your first clue that the two are not the same nor are they to be treated the same. It the intent of the regulation was that you not ever descend below DH, the same as MDA, that that is what the regulation would say: " no pilot may operate an aircraft, except a military aircraft of the United States, at any airport below the authorized MDA or DH "



But that's not what it says. Instead they have a completely different phrase that says you may not "continue an approach” below the DH.



So why would they word it differently when they mean the same thing as the MDA??



Trick question!!!! They word it differently because they do *not* mean the same.



If you dip below DH (and certainly, you will if you fly the approach as it is intended) while executing the missed approach you are not "continuing" the approach. You have abandoned the approach at the very moment you decided to go around, and you made that decision at decision height. The part where you dip below the DH is not a continuation of the approach; it is execution of the missed approach.

 

[Amish RakeFight]

How is it that instrument rated pilots don't know this? :laugh:

...talk about a hole in training.

 

[Papps]

Im sure the FAA is very careful how they word that reg. thats where the confusion sets in. They have to word it so that people don't push it and draaaaag that decision out until 50agl without the runway in sight. Thats why the first time you read the reg you think DH is just like MDA

 

[MauleSkinner]

How is it that instrument rated pilots don't know this? :laugh:

...talk about a hole in training.

Because most of us require a semi-traumatic experience before we realize that we need to study things on our own (as opposed to "memorizing" things on our own), rather than just assuming that the instructor will tell us "everything we need to know".

This particular "hole in training" probably goes back through several generations of instructor/student relationships.

Fly safe!

David

btw...in case you're wondering, you ain't been cold until you've sat in a cold airplane for a couple of hours because you didn't know a particular nuance of the heater

 

[Amish RakeFight]

Because most of us require a semi-traumatic experience before we realize that we need to study things on our own (as opposed to "memorizing" things on our own), rather than just assuming that the instructor will tell us "everything we need to know".

This particular "hole in training" probably goes back through several generations of instructor/student relationships.

When I did my instrument training, many of the ILS approaches terminated in a go-around which left me below DH as I executed the missed. How could a student NOT do this during their training.

 

[MauleSkinner]

When I did my instrument training, many of the ILS approaches terminated in a go-around which left me below DH as I executed the missed. How could a student NOT do this during their training.

There's a difference between "doing" something and "knowing" something. We do things and see things all the time that don't necessarily register in our minds. It's entirely possible that a student sees himself at DH, initiates the missed approach, and the next time he looks at the altimeter he's 500 feet above DH and climbing. Never saw the altimeter scoop below DH, never gave it enough thought to realize that it HAD to have happened.

Particularly in a training environment, where we're generally so busy trying to do what we're supposed to that we don't notice what's happening along the way.

Fly safe!

David

 

[pgcfii2002]

My students do the same...arrive at the DH or MDA, go missed and keep descending. I usually have them pad the mins say 50' so they don't bust the ride.