ESTABLISHED on a DME ARC ?

[The FNG]

Lots of good points. And I'm willing to admit "I'm" wrong if that's the case. (and there's that "you're" wrong, not "what's" wrong thing again - I still don't get it) So, if someone more well read has a definative answer please post the reference. Not sure what "over your head" means but if you're willing to elaborate I'm all ears (eyes?). I will add that a certain training department office is amused by this discussion.

Further, I didn't say flying an approach 1/2 dot off center is not established, but rather having centered and thereafter remaining within limits; vice never centered and thereafter waffeling around trying to get "established" while descending. Case in point: the crash of Secretary Ron Brown in Bosnia shooting the dual NDB into Dubrovnik. (Been there, done that, got the t-shirt) That's what can happen.

Semantics? Absolutely. Should everything be defined to a gnats ass? Not necessarily. But some things are worth talking about.

So lets talk about "course alive". Course alive occurs well before flight director capture. Shouldn't that mean something? I don't know what the tolerance is and I know it's not needles centered. But I'm ok with FD captured because it's been certified. I'm not ok with plain ol' course alive. I still think "striving" for centered is the safest approach. Who can argue about that (someone I'm sure)?

 

[100LL... Again!]

A squared gets an A+ Bravo!
--------------------------------------------------

FNG-

There are some autopilots that capture the loc before the live needle.

I guess I don't care if a training department thinks that this is amusing, since there is SOME importance to this issue. A while back in an issue of the ALPA magazine, an article was written about a MAJOR airline where the flight department wrote a letter to the FAA saying that the approach into JAC was improperly designed. The FAA wrote back and said "You're flying it wrong."

The article is called something like "No Shortcut Here"

This means that enough pilots flew it wrong and brought it up to their flight department that they felt they needed to write a letter. Probably written by a CP or Dir. Trng.

Just goes to show that you need to see it in print before you can believe it. Even then...

If the needle is not pegged, you are in safe airspace.


Quiz #2:

How much obstacle protection on the final approach course of a VOR approach?

a. 250'
b. 300'
c. depends on temperature
d. all of the above are possible answers

 

[80/20]

Quote:
_______________________________
Singlecoil said:
Course alive on a procedure turn on a VOR or ILS/LOC means you can let down.
_________________________________

This started a good discussion, which is what makes this forum good! I knew I had read about this somewhere and started looking for the source. First, AIM, TERPS, FAA Orders and US Gov Specs for IAPs but no result. It really bugged me because I knew it was hidden in some obscure source document. Finally I found it: ICAO Doc 8168-OPS/611, Procedures for Air Navigation Services - Volume 1, which simply says:

"Established" is considered as being within half full scale deflection for the ILS and VOR or within +/- 5 degrees of the required bearing for the NDB.

Note: This is given specifically for the inbound course/final approach.

Not just a theoretical issue, if you are heavy with tailwind at altitude and on a steep approach it can be difficult to get down unless you start as soon the chart maker's intened.

FNG points out the risk with side lobes (false localizer beams). Any approach that has problems with this within 10 degrees of final must have a non-standard warning. Example: "LLZ only to be used inside +/- 10 degrees of front beam"

 

[A Squared]

OK, if you insist:

D all of the above.

a) A VOR approach with a FAF gives 250' of obstacle clearance,

b) A VOR approach with no FAF gives 300' of obstacle clearance,

c) those clearances are predicated on the correct *true* altitudes, for a given indicated altitude, the true altitude will be lower with lower than standard temperatures. For example, assume an MDA of 600 feet HAA, 300 foot obstacle, and 300 feet of clearence on a VOR with no FAF. If the temp is -40, and your altimiter is correctly set to the altimeter setting for that airport, and you are at 600' indicated, your actual altitude will be 455', still enough to clear the obstacle, but not by much.

regards

 

[canadflyau]

I'll keep this short.. Being established is as pointed out earlier, 11DME is 11DME, 13,000 is 13,000, etc etc. but correct me if I am wrong, but for each one of these are acceptable tolerences establised in the FAR/AIM, ie +or-1 mile is within tolerence for the DME arc procedure.. if you are outside of this, you are not "estblished." They even let us know how wide a Victor is and how to figure out if we are in those established tolerances..

I fly a DME arc at several airports in fairly dense airspace, and if you don't call "established on the 15DME arc" within seconds of being within +or- 1 mile (depending on which direction they vector you from) ATC will call you asking "are you established?"

my .02

 

[100LL... Again!]

Tip 'o the hat to A squared.

 

[80/20]

Singlecoil talkes about when you can start your descent on the inbound track. He suggested that you may initiate this while you are trying to get 100% aligned with the track. I do not think that he intends to say that it is ok to fly the approach down to minima with intentional deviations.

The width of the obstacle clearance area at the part where the final approach course/inbound track is anticipated to be intercepted is wide enough to allow Singlecoils technique (It should be half of full scale deflection for ILS/VOR and +/- 5 degrees for NDB). That does not mean that you always should squeeze yourself down to the lowest limit. A Squared points out metreological factors that the TERPS expects the pilot to consider. There have been many incidents with very close to the ground flights caused by minima not corrected for cold weather. Some airlines that routinely operate in cold weather will use a table with values to be added to published minima.

 

[Singlecoil]

80/20 is right on on this one. I did a search on the Practical Test Standards for Instrument and ATP thinking they would be the same on this issue. They are not. They hold you to different tolerances regarding tracking the radial or course inside the FAF, but don't say when you can descend.

I agree that the most neglected point here is temperature. The PTS don't even mention it, yet you can find yourself 700 feet low on a very cold day in Alaska or Montana and still think everything is fine. What is worse, some Minimum Vectoring Altitudes in mountainous areas are only 1000 feet AGL. On a cold day, you might be only 300 feet over the mountains, but ATC thinks you are 1000 feet AGL because your mode C transponder is lying just like your altimeter. In Canada they correct for this with MVA's but in the US they don't. I've filed NASA reports on this but haven't heard a thing in reply. This is not a problem unless you fly near mountains, then you better give yourself some extra altitude if the temperature is colder than standard.

 

[80/20]

Cold weather altitude corrections enroute.
A rule used by several operators: Add 4% per 10C below standard.
Note that you must request a higher altitude if you don't want to maintain an assigned altitude that you think could be too low. ATC does not correct their minimum vectoring altitudes for low temperature.

Use a computer or table to adjust approach minima. A table is quick and easy to use. Non-precision approach minimum altitudes could require adjustments from 40 to more than 100 feet on a cold winter day.

 

[100LL... Again!]

The amount of cold-weather variation depends primarily on two things:

#1 HAT or HAA for the approach. The higher the altitude AGL. the larger the error can be.

#2 Temperature. The colder the temp, the larger the error.

Therefore, there is more potential to be significantly low on an approach with a HAT of 900' than on one with a HAT of 350'.

The real danger can occur on PTs that are extra-high due to rising terrain, since the HAT on the PT could be a few thousand feet on the outbound.

Th higher the aircraft is above the weather reporting point, the worse the error.



Additionally, wind over mountainous terrain can noticeably affect the pressure in the vicinity of the aircraft and change the pressure lapse rate from the surface to the PT altitude, for example. Some consideration is given for this type of terrain when determining minimum altitudes.