Setting of missed APP ALT.

[airbond]

Question for Boeing pilots.

On straight in non-precision approaches when do you set the missed approach altitude?
Upon leaving final approach fix? or when reaching ALT HOLD at MDA?

For example approach starts at 3000 ft. Missed approach ALT is 4000ft.
Upen leaving 3000 in V/S descent, do you then set 4000?
OR
Set MDA 500ft, leaving 3000 in V/S, and when capturing 500 in ALT HOLD then set missed approach alt of 4000.

[flyerjohn]

Airbond, in reply to your post,
The missed approach alt is set on the MCP after passing the FAF.
The Non Precision Approach is flown as a continuous descent to replicate as closely as possible an ILS. The idea being that the MDA effectively becomes a DA. i.e at MDA if nothing is seen then a G/A is flown from this point.
This is the way my last two companies have taught it and, if you think about it, it makes sense.
Unlike a light twin, if in, say a 737 or bigger a/c you actually flew level at the MDA, it's highly unlikely that you would be in a safe position from which to land if you did become visual. Not to mention the possibility of level flight just a few hundred feet above the surrounding terrain (think Zurich etc...)
Flying the continuous approach means that if you sight the runway by MDA you can continue a stabilised approach to land in as normal a manner as possible.
Hope that answers your query.

[Pilot Pete]

Just to add, using the constant descent approach method of flying the non-precision approach you must not descend below MDA, therefore you need to initiate a go-around before reaching MDA. Our SOP is to add 50' to the published MDA, bug that and make it a 'non-precision decision altitude' (if that makes sense, it's not an official name for it!)

As for the 737, when you level at the platform altitude we wind the altitude window 1000' above platform. You can then start a descent away from your present altitude in vertical speed. If the missed approach altitude is below the platform we wait until we are 1000' below the missed approach altitude and then set it. This prevents the a/c going into Alt Acq and climbing back to the MCP altitude window.

PP

[Rivet gun]

Depends on company SOPs. The alternative is to set the MCP alt to MDA just before the final fix. The autopilot will then capture the MDA and as soon as it goes ALT HOLD you can set the MCP to missed app altitude then press TOGA. With this procedure there is no need for an increment to MDA since the ALT ACQ flare will begin above the MDA set in the MCP. However once it goes ALT ACQ if you are not already visual you are committed to going around.

A couple of gothcas.

If you alter the MCP altitude before ALT HOLD you may bust minima.
If there is a published missed approach point, you should not fly level beyond it.

[alexban]

There are different sop's I've know of.
Now.most require you to do a continuous descent from the FAF.
On the NG you may select missed app alt when going 300' bellow the FAF altitude, while on the classic is set while approaching the MDA.
One other thing,the point where you reach MDA may not be the point where you initiate the GA,or where you decide to land. There are many procedures where you canmaintain level flight at MDA till the MAP,or where a VP is specified.
We have one particular airport where VP is much ahead the MAP ,and we had some interesting landings,due to pilots going beyond VP to the MAP (which is at the THR) and deciding to land when they saw the rwy,a bit late,you guess...
If you've select missed app alt after leaving FAF is very important to check when arriving at MDA,and pushing alt hold or GA....otherwise...:}
Brgds...

[RYR-738-JOCKEY]

The procedure where the missed approach alt is set after reaching MDA has a couple of disadvantages. 1: You have to round up your MDA to the nearest hundred because that's the increments in the MCP alt window. 2: You will get alt acquire before reaching MDA, and therefore the decision whether or not to continue is taken earlier and therefore higher.
The difference in go around initiation altitude between the two procedures
(1: Setting your MDA at FAF, 2: Setting Mis App alt at FAF) can be more than 200 feet, depending on your ROD.
I know some will argue that if you have a high ROD at MDA you will certainly go below, and I agree. :8 However, that will apply to an ILS approach as well. The Jar-Ops state that you may continue down to DA/H or MDA/H, but you will have to go around if you don't acquire the required visual reference at that point. So you are actually allowed to "bust" your minimums :confused: , as long as you initiate the go-around before reaching either DA/H or MDA/H. That's what the different minimums (according to category) are for. The Jar-Ops state the system minimums, and then there's a wide range of factors listed, among them: The OCH/OCL for the category of aeroplane, which takes into account the height loss for the category and that is added to your system minimum. That's why some operators can get down, while others are diverting when the WX is crappy.
Allright, over to you now...:E

[haughtney1]

Both concepts have merit....Ive flown with both and cant honestly say either is better than the other, perhaps setting MDA+50/100 helps with reminding yourself...but then again bugging MDA+50 and using it like a DA works bloody well! My biggest problem is remembering to remember setting the Missed ALT !!! :uhoh:

[whatdoesthisbuttondo]

My lot set the alt at FAF (making sure that you don't capture it again when you begin the descent).

Then fly continuous descent to MDA(+50).

[RYR-738-JOCKEY]

I just checked the Icao Doc 8168, vol 2..and I believe I have to correct myself. For precision approaches there is an allowance for altitude loss during go around, but NONE for non-precision approaches. So, that makes my point about that you can initiate go around at MDA (on your way down)...well...slightly..uh..inaccurate.
Anyone care to comment?

[whatdoesthisbuttondo]

We add 50ft to all non precision minima e.g. MDA, LOC only minima or circling approaches.

[JonaLX]

I just checked the Icao Doc 8168, vol 2..and I believe I have to correct myself. For precision approaches there is an allowance for altitude loss during go around, but NONE for non-precision approaches. So, that makes my point about that you can initiate go around at MDA (on your way down)...well...slightly..uh..inaccurate.
Anyone care to comment?

Indeed

the DA/H is the altitude/height at which you should start the go-around procedure. And allowances are made for altitude loss due to inertia.

MDA is a strict minimum, so you'll better be descending at a low ROD if approaching it not being visual with the runway or lights.

Not flying boeing, but haven't you tought about having to perform a go-around before reaching MDA? (and Missed approach point?)
If you haven't set your MCP to acquire final go-around altitude, could be quite problematic... (quite high ROC - maybe not a big altitude change - quite busy)

[airbond]

Thanks for the feedback.

So as I can see, most are setting the missed app alt, once they have left the initial alt,and then descending away form this.

Guess its a good idea because if you set the MDA, once the aircraft goes into ALT HLD and you become visual, then its more difficult to configure the aircraft again, and more work to remember to set the missed app alt.