Decision light

[kieranja]

I been looking but cant see anything

On my quality wings 757 on the efis panel theres a decision hight setting. What is this for. Adi do ref. Its at 200 at the moment as thats default.

[lnuss]

Decision Height is the altitude on a precision instrument approach at which a decision MUST be made to either land or go around. If the pilot can see the "runway environment" (the "rabbit" or approach lighting system), then he is allowed to land, otherwise he must go around.

 

Most, but not all, precision approaches have a DH of 200 feet, but for some it's higher, due to the surrounding environment (usually higher obstacles). Note that the FAA's manuals (faa.gov) give more complete information.

[plainsman]

I am not an airline pilot, so this is my understanding. As you approach the runway, if for some reason you want to abort the landing and go around, you can safely do so as long as you are above the decision height. Once you are below that, you are committed to the landing. The engines would not be able to spool up in time to give thrust needed to go around.

I didn't try to post on top of Larry. His post arrived while i was typing.

Edited October 1, 2020 by plainsman

[kieranja]

Ar right that makes sense and now seems quite obvious. cheers guys

[lnuss]

if for some reason you want to abort the landing and go around, you can safely do so as long as you are above the decision height. Once you are below that, you are committed to the landing.

 

No, it's as I mention in my post above, and is a term specific to precision instrument approaches, and is not specific to jet aircraft -- it applies to ALL aircraft on a precision approach, whether it's a Cessna 150 or the Concorde. It's the point at which you make the go-around decision based on whether you can see the runway environment.

 

Here is a better way to state it, from Wikipedia:

 

In a precision approach, the decision height (DH) or decision altitude (DA) is a specified lowest height or altitude in the approach descent at which, if the required visual reference to continue the approach (such as the runway markings or runway environment) is not visible to the pilot, the pilot must initiate a missed approach. (A decision height is measured AGL (above ground level) while a decision altitude is measured above MSL (mean sea level).) The specific values for DH and/or DA at a given airport are established with intention to allow a pilot sufficient time to safely re-configure an aircraft to climb and execute the missed approach procedures while avoiding terrain and obstacles. A DH/DA denotes the altitude in which a missed approach procedure must be started, it does not preclude the aircraft from descending below the prescribed DH/DA.

 

It's not something you have to guess at, when an internet search can turn up the answer straight from faa.gov or Wikipedia or several other sources online.

Edited October 2, 2020 by lnuss

[plainsman]

I apologize Larry! I should have just erased my post. If I had known you were responding, I would not have posted! Again, I am sorry! I am an FDE guy, and out of my element!!

B Boudoin

[lnuss]

That's OK, but I just wanted to be sure we have the right info out there.

 

Be careful out there...