NOS & DOD IAP's

[Hugh Jorgan]

What is the purpose of the High Approaches? My guess is that it simulates minimum exposure to ground fire, if that is the case do you fly them more often than normal appchs?

Thanks again

Nikes

Stay higher longer, saves gas...

 

[rainman_02]

Actually, hi- approaches consume more fuel. In an enroute descent situation, you can calculate out the top-of-descent point to make an idle power descent from cruise altitude to the initial approach fix. Because most penetrations require the use of speed brakes and sometimes you configure prior to the IAF and penetrate with gear and flaps, you are burning more fuel than a comparable enroute descent to a low- approach.


As far as why they were created...I will ask around.

 

[Tweetdrvr]

Hugh and YCJ are correct.

Both the civil and mil books have a statement on the front that says they are printed in accordance with inter-agency air cartographic committee specifications and agreements approved by the DOD and the FAA.

Air Traffic Control agencies hate Hi approaches. They usually start in Center's Airspace, transition through approach control's space and end up in tower's space. Before they can approve a high approach, they have to look at the flow and figure out how this guy diving out of the sky is going to fit in behind or in front of someone being vectored around in the low radar pattern. But when you are gas limited such as a fighter might be, it is easier to divert from 10,000 feet or higher than it is to go all the way to a missed approach point or even to a low altitude IAF that may be at 2 or 3,000 feet.

The parenthetical numbers behind the HAT are what the military guys use for ceiling and visibility filing criteria that allow us to carry a little less fuel than if we filed based only on forecast visibility. If I filed using only visibility criteria, I would have to carry enough gas to shoot the entire approach at my destination, go missed and divert to my alternate. If using ceiling and vis weather for filing, then we carry enough fuel to go to the IAF, fly past it and divert to the alternate and carry only enough fuel to shoot one approach. If I use ceiling and vis, I can show up to my IAF at the destination, and if the weather is above approach mins by an acceptable margin, I can roll the dice shoot the approach and know that I won't have to miss. If the weather is pretty close to mins, i.e. sky obscured and RVR less than a mile for an ILS, then maybe I should just suck it up and divert smartly before I commit to an approach that might end up in a miss and then trying to divert with not enough gas.

The High books will go away sometime this summer. It will be interesting to see if the Civilan thin paper books will include any of them. There are some to civil fields that are not that high. The Hi VOR RWY 3 to San Angelo for example has an IAF at only 12,000.

 

[STBY GAIN]

My understanding about why we have HI-IAPs is included in many of the previous replies, but here's my take. In the Viper, the map case is barely big enough to hold a full piddle pack, much less the entire Low-series pub set. We are required to carry the standard HI charts, IFR Sup, and FIH in there. It is also rather inaccessible in flight, or at least it takes some gymnastics to get back there. There is a little pocket on the other side of the 'pit that is much easier to reach, that is big enough for about 1 approach book. Conveniently, this one book holds just about all the approaches I could want to fly in my 1/3 of the country.

As far as the actual TACAN penetration goes, they are rarely flown other than for currency. What the previous poster, TweetDriver said about them, is spot on; it's a lot easier to divert from an IAF at 15,000 feet than from something a lot lower. The IAF's are usually a lot easier to get to from the enroute structure if you are comm-out, which is a big part of why the full procedure exists.

Finally, a large number of the low-book procedures include such funny maneuvers as procedure turns and procedure tracks and holding-in-lieu-of approaches. If I'm really comm-out, I'd rather penetrate off a TACAN from 15,000 feet than try to remember back to Tweets about which way to turn for a procedure turn (the last time most of us did that!)

As alluded to earlier, there is a note inside the front cover of the most recent IFR Sup; they are indeed consolidating HIs and LOs into a 24(?) volume set, with the HI charts having the black slashes on the borders. That's going to be a tight fit in the cockpit, I'll tell you that much. I see that lasting about 6 months.

 

[talondriver]

I think I'll just find a airfield VFR and report initial.

 

[JCJ]

two other things re DOD vs NACO plates

If you look at the NACO low altitude enroute IFR chart, you will notice that airports are listed in either blue, green or brown. the color is related to charted IAP's

blue - airport has at least one IAP published in the DOD plates (includes mil airports with IAP's published only in DOD plates as well as civil airports with approaches published in NACO and DOD plates)

green - airport has IAP published in civil NACO plates only

brown - airport has no published IAP's (may apply to civil or mil)



in small print at the top of the page of the IAP will be an abbreviation for the publishing agency - usually FAA for civil, USAF for USAF, USA for Army, USN for Navy & Marines