hello,just two quick question which are surely quick to answer. ;-) where do i get the decison altitude for an approch to an airport. i looked in the navigraph charts for several airport, but i didn't found it. and the second question just for my understatement. the decision altitude is the altitude on which you must have a visual contact to the runway. if not you heve to go arround. is that right?thanks for answers alreadynicolas reich

I haven't used the navigraph charts, but normally there is a table at the bottom of the approach chart which lists the DH for the different catagories. I believe you are correct, the DH us the lowest minimum height you can fly before been vissual with the runway.I may not be correct on these, I am in no means an expert, but I hope I have satisfactorly answerd your question.

I haven't used the navigraph charts, but normally there is a table at the bottom of the approach chart which lists the DH for the different catagories. I believe you are correct, the DH us the lowest minimum height you can fly before been vissual with the runway.I may not be correct on these, I am in no means an expert, but I hope I have satisfactorly answerd your question.

Yes ur correct dh heights are on the bottom of tha navigrapgh charts listed in different cats and different approaches as well usually they are on the bottom left hand corner of the ils charts

Firstly it is not called "Decision Altitude" Altitude refers to the height above sea level!! The correct phrase is "Decision Height" (above ground).This table below was made up from the information at Eurocontrol (Not N.America) and shows the relationship between Decision height and RVR(Runway Visual Range)So depending on whether your destination airport is CATI, CATII, CATIII that will tell you your RVR and decision height!vololiberista

The above is partially correct. There are decision points based both on altitude and height.DH - or decision height - is the height above the ground, at the current location, at which you must make a command decision to continue the approach to a landing, or go missed. Using this value requires a radio altimeter to judge height above the ground, specifically.MDA - or minimum descent altitude - is the altitude (altimeter reading) by which you must make a command decision to continue the approach to landing, or go missed.The altitudes are published at the bottom of the charts in the United States, with the larger number (in font size) being the MDA, and the smaller number being the DH.

DH is referenced by a radar altimeterDA is referenced by the standard altimeter set to the aerodrome QNHOn many charts I have seen over at the Eurocontrol free repository and use regularly, the DA is often the first value and the DH is in brackets...Andrew

Andrew is correct. All our Jeppesen charts for our operation gives the height in DA referring to BARO altitude. The only time we use DH would be on a CAT II approach.Also you don't have to be visual with the runway to continue past DA (DH), you have to be visual with an approach light segment consisting of 3 or more lights with one lateral reference, that's it.

DH is referenced by a radar altimeterDA is referenced by the standard altimeter set to the aerodrome QNHOn many charts I have seen over at the Eurocontrol free repository and use regularly, the DA is often the first value and the DH is in brackets...Andrew

Radio altimeter(unless you're flying something mil-spec, like a B-1, or Tornado, you're definitely not using radar for terrain or altitude functions)

The terms are interchangeable, interestingly it was invented before radar in 1924 (http://en.wikipedia.org/wiki/Radar_altimeter)

I was taught that DH was for a precision approach and MDA was for non-precision. The idea being that while on an ILS, you'll reach the DH, and if you don't have the proper requirements to continue (usually visual observation of the runway enviornment), you go missed. If you're on the glide slope this decision should be the same point in space every time you do a particular approach, the "Missed Approach Point". (Assumes an ordinary ILS approach, although I suppose they could be in different places theoretically.)For non-precision, you aren't sticking to a G/S so, once you get down to the MDA, you stop there and wait until you reach the MAP. Depending on the rate you go down it could be a bit before you reach the MAP. But same general rule applies: until you have reference to the ground, you shouldn't go down any further. So, the reaching the MDA doesn't mean you've reached the MAP or that it is time to decide yet. Anyway, that's how I approach it (pun sort of intended), other countries may have different regs and airlines may have their own SOP.

The terms are interchangeable, interestingly it was invented before radar in 1924 (http://en.wikipedia.org/wiki/Radar_altimeter)

They are used interchangeably in that article, but keep in mind that the article is wikipedia and not something properly vetted. Don't get me wrong, there is great information on wikipedia, and a lot of it comes from good sources, but that article blurs the line.Radio altimeters work accurately only up to about 2000-3000 feet, which is why you'll only see them with scales to about those altitudes. Radar altimeters do not have the same accuracy issues and can be used at much higher altitudes, for more precise height above ground measurements. While they both tell you the actual height AGL, and they both use waves to take that measurement, to say most planes have a radar altimeter would be incorrect. It's like calling turboprops and turbojets the same thing. They both have compressors, fan blades, and similar internals, while they both propel aircraft forward, but they are fundamentally different in their effective applications.The note that radio altimeters came before the invention of radar should lend a hand to the argument that they are fundamentally different in their rangefinding capacity.

Doppler radar however, is/was used as a means of navigation though not in isolation. It is/was usually used along with INS. It's main purpose was to compute drift and as such was a useful tool for autoland.vooliberista

I was taught that DH was for a precision approach and MDA was for non-precision. The idea being that while on an ILS, you'll reach the DH, and if you don't have the proper requirements to continue (usually visual observation of the runway enviornment), you go missed. If you're on the glide slope this decision should be the same point in space every time you do a particular approach, the "Missed Approach Point". (Assumes an ordinary ILS approach, although I suppose they could be in different places theoretically.)For non-precision, you aren't sticking to a G/S so, once you get down to the MDA, you stop there and wait until you reach the MAP. Depending on the rate you go down it could be a bit before you reach the MAP. But same general rule applies: until you have reference to the ground, you shouldn't go down any further. So, the reaching the MDA doesn't mean you've reached the MAP or that it is time to decide yet. Anyway, that's how I approach it (pun sort of intended), other countries may have different regs and airlines may have their own SOP.

Here is what I found on the FAA site for ILS approaches :http://www.faa.gov/l...media/CH-05.pdf p 5-51 (p 51/68)My understanding is that, in the USA, you can use either DA or DH for CAT I ILS landings but that DH is mandatory for CAT II and III ILS. Am I right on this one?Brunofrom the FAA procedure handbook (see link above):

The lowest authorized ILS minimums, with all required ground and airborne systems components operative, are

• CAT I — Decision Height (DH) 200 feet and Runway Visual Range (RVR) 2,400 feet (with touchdown

zone and centerline lighting, RVR 1800 feet),

• CAT II — DH 100 feet and RVR 1,200 feet,

• CAT IIIa — No DH or DH below 100 feet and RVR not less than 700 feet,

• CAT IIIb — No DH or DH below 50 feet and RVR less than 700 feet but not less than 150 feet, and

• CAT IIIc — No DH and no RVR limitation.

NOTE: Special authorization and equipment are required for CAT II and III.

The problem with Missed Approach points is that alot of the time they are too close in to be of any use. An example would be a MAP of 0.5DME inbound on a LOC/DME approach. Technically you can fly to MDA, let's give an arbitrary figure of 560ft. This could be 400ft agl. So when you get to MDA and you are not visual you can fly to the MAP before initiating a go-around. If you were to get visual before the MAP you can then continue to land. The issue here is a stabilised approach criteria. There is no way you can land at a height of 400ft agl and 0.5DME in a stable condition. This is why most, if not all airline's S.O.Ps would be to go around at a height of MDA + 50ft, and not the MAP. This could be ok in light aircraft of course.

I was taught that DH was for a precision approach and MDA was for non-precision.

Correct, but as Andrew pointed out above you might also reference to MSL rather than AGL so especially for small planes that don't even have an RA it's common to use DA and not DH, while it's still a precision approach. Say you fly a CAT I ILS in some simple single engine prop and let's assume a TDZE of 263', and DH 200', then DA would maybe be 463' to make a quick and simple example. This can be baro referenced by the ordinary altimeter.As it's been said before there is also MDH stated on some charts (Jepp does is IIRC), but I've not encountered a practical use for it other than knowing how high you actually are above the ground, then again I haven't seen anyone reference to RA during an NPA but I might be wrong.