Descent below Decision Height/Altitude

[Captain_Bob]

Hi there,

Can anyone help supbstantiate the following?

[ QUOTE ]
On a precision approach, upon reaching the DA (altitude above MSL, the term "DA" is replacing the obsolete term DH) or DH (height AGL) a missed approach must be initiated if the visual reference to continue the approach to land has not been established. Your momentum will naturally carry you slightly below the DA as you start the miss. This is ok. But a DA is usually 200 feet AGL, so you don't have much room. Important to start the miss immediately. The missed approach point (MAP) is by definition where you reach DA.

[/ QUOTE ] This info did not come from an official FAA document, although I thought I had heard this at some point during my CFI training. Does anyone have any specific FAA reference for the above? Specifically, regarding a small decent below DA as you transition to the Missed? My research on the internet thus far indicates it is only for VNAV... Any other situations?

Thanks,

Bob

 

[pscraig]

From the ATP PTS Area V Task F (Missed Approach) : "...However, satisfactory performance may be concluded if the missed approach is properly initiated at DA/DH and the airplane descends below DA/DH only because of the momentum of the airplane transitioning from a stabilized approach to a missed approach."

That is the only reference I could find while searching the ASA Flight Library Pro CD.

 

[MikeD]

[ QUOTE ]
From the ATP PTS Area V Task F (Missed Approach) : "...However, satisfactory performance may be concluded if the missed approach is properly initiated at DA/DH and the airplane descends below DA/DH only because of the momentum of the airplane transitioning from a stabilized approach to a missed approach."

That is the only reference I could find while searching the ASA Flight Library Pro CD.

[/ QUOTE ]

Correct. This still satisfies the intent of 14 CFR 91.175(c). Logically speaking, there's no way you can reach a DH and not go below it some if executing a missed. Of course, you're not going to descend 150' through it, but I can easily see 20-50' depending. There's no obstructions to worry about (assuming you're descending on glideslope still) since those are TERPSd out already. With an MDA on a non-precision, I can see NOT descending below on the missed, since you'd normally be established at that altitude prior to the missed.

Of course, if you're a "military aircraft of the United States", you're not concerned with 14 CFR 91.175(a)(c)(d)(e)(f) anyway since you're exempt.

I, therefore, don't really concern myself with that reg.

 

[jdflight]

AIM 5-4-19(b) states that "Protected obstacle clearance areas for missed approach are predicated on the assumption that the missed approach is initiated at the decision height (DH)...."

14CFR 91.175(c) states, "No pilot may operate an aircraft...at any airport below the authorized MDA or continue an approach below the authorized DH...."

The clear distinction between descent below an MDA and below a DH indicates that a pilot may indeed drop below DH if weather is below minimums if that pilot does so as a result of executing the missed approach procedure.