Dual NDB approach
PPRuNeaholic
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I'm having trouble thinking of an aerodrome in the USA that would have even one NDB. I'm pretty sure that Canada used to have a few aerodromes served by Twin NDB approaches and may still have one or two in operation.
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well, there must be hundreds of single-ndb approaches in the US, either with a on field ndb, off field ndb, or locater.
i think there is/used to be one in/near puerto rico aswell, there is also one at EHGG, but i am trying to find an operational dual-ndb approach in the US, or even trying to find out if there still is one.
i think there is/used to be one in/near puerto rico aswell, there is also one at EHGG, but i am trying to find an operational dual-ndb approach in the US, or even trying to find out if there still is one.
PPRuNeaholic
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The last time I was regularly flying there was the early 80s and there was a surprising number of single NDB approaches. Having cut my teeth on them in Oz, I had no trouble with them but I found that Americans generally didn't like them and, for the most part, didn't have a clue on how to fly them.
I'd have thought that, by now, the FAA would've phased out most if not all their NDBs in favour of VOR and Localiser type NPAs.
It looks like you need more up to date input than I can provide.
I'd have thought that, by now, the FAA would've phased out most if not all their NDBs in favour of VOR and Localiser type NPAs.
It looks like you need more up to date input than I can provide.
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ILBD
I can' think of one in the States but if you go to Russia or any of the ex-Soviet countries, you can find them everywhere. In fact, at may of the large airports not normally serverd by foreign carriers, that is the only approach system which is available.
I can' think of one in the States but if you go to Russia or any of the ex-Soviet countries, you can find them everywhere. In fact, at may of the large airports not normally serverd by foreign carriers, that is the only approach system which is available.
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Just had a quick look at my airways manual and some are
Long Beach, CA
Mesa , Ariz.
Monte Vista, Colo
Portales, New Mexico
Show Low, Ariz
There are quite a few still around....
Julian.
Long Beach, CA
Mesa , Ariz.
Monte Vista, Colo
Portales, New Mexico
Show Low, Ariz
There are quite a few still around....
Julian.
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Long Beach, CA
Mesa , Ariz.
Monte Vista, Colo
Portales, New Mexico
Show Low, Ariz
There are quite a few still around....
Mesa , Ariz.
Monte Vista, Colo
Portales, New Mexico
Show Low, Ariz
There are quite a few still around....
There's still lots of single NDB approaches in the US although many (most?) are supplemented by GPS approaches if nothing else is there. There's nearly always an alternative type of approach. Still, the aerodrome I'm based at only has an NDB available for a ground rather than satellite referenced approach. Interestingly the US doesn't use 'base turn/teardrop' type approach designs at all - they are all course reversal types with a 45/180 reversal turn. You could do an 80/260 reversal but I suspect everyone here stick to 45/180s.
Only last month I had to do an NDB approach to an airstrip in Georgia, complete with holding pattern & a procedure turn down to minimums. Mind you, the the typical US approach usually becomes 'vectors to intercept the final approach course' so that was a bit unusual. Was bloody glad that day that I originally trained in Oz where NDB approaches are the norm - and are a requirement for the issue of the rating.
The US has other approaches though, that don't exist in Oz or the UK: Localiser type Directional Aid, Simplified Directional Facility, Backcourse Localiser, and Localiser/NDB or VOR cross bearing fixes of the top of my head.
Still, it's fun watching the look of astonishment when I try to explain the Oz 'DME Homing & Descent' approach to US pilots.
Only last month I had to do an NDB approach to an airstrip in Georgia, complete with holding pattern & a procedure turn down to minimums. Mind you, the the typical US approach usually becomes 'vectors to intercept the final approach course' so that was a bit unusual. Was bloody glad that day that I originally trained in Oz where NDB approaches are the norm - and are a requirement for the issue of the rating.
The US has other approaches though, that don't exist in Oz or the UK: Localiser type Directional Aid, Simplified Directional Facility, Backcourse Localiser, and Localiser/NDB or VOR cross bearing fixes of the top of my head.
Still, it's fun watching the look of astonishment when I try to explain the Oz 'DME Homing & Descent' approach to US pilots.
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Tinstaafl,
The 45/180 reversal turn is that chosen as the standard for illustration on the approach plates. PANS-OPS indicates that the 80/260 reversal is still an approved alternative.
There are definite limitations upon the 45/180 turn, at higher speeds (I recall about 180 Kts) overshoot of the inbound QDM is guaranteed, something that cannot happen with the 80/260 turn (Of course, a strong crosswind can play havoc with both of them).
Regards,
Old Smokey
The 45/180 reversal turn is that chosen as the standard for illustration on the approach plates. PANS-OPS indicates that the 80/260 reversal is still an approved alternative.
There are definite limitations upon the 45/180 turn, at higher speeds (I recall about 180 Kts) overshoot of the inbound QDM is guaranteed, something that cannot happen with the 80/260 turn (Of course, a strong crosswind can play havoc with both of them).
Regards,
Old Smokey
G'day Smokey
Yeah, I was alluding to the 45/180 being the standard depiction. I suspect that's why 45/180 tends to be the reversal that I think is most commonly used here. Oz's DAPs use the 80/260 as their standard depiction which, I think, is why it's more common there.
Yeah, I was alluding to the 45/180 being the standard depiction. I suspect that's why 45/180 tends to be the reversal that I think is most commonly used here. Oz's DAPs use the 80/260 as their standard depiction which, I think, is why it's more common there.
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Yep they are all single NDB approachs, anwering OzExpat.
Not sure about dual approaches would have to sit down and go through all the plates but cant think of any off the top of my head...
Not sure about dual approaches would have to sit down and go through all the plates but cant think of any off the top of my head...
Try Avalon in Victoria straight in on Runway 18. Used to be called Twin Locator. Now its called NDB. You could always stir up discussions in the cockpit (real aircraft or simulator) when some pilots said you needed two ADF's in the cockpit to legally fly the Twin Locator approach. Not so, of course.
I've always understood the advantage of a Twin Locator/NDB approach vs a single NDB was that the more accurate positioning achieved at the FAF (ie the 1st Locator/NDB) allows the procedure designer to use a different (smaller?) protected airspace buffer & a slightly lower MDA.
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Yes Smokey. In the most usual situation, the first L or NDB marks the FAF and second one marks the MAPt. There can be slight variations on this but the fact remains that, if the first facility marks the FAF, the procedure protection area can be made smaller by virture of the overlapping final segment protection areas. This clearly indicates that the procedure should be flown using 2 ADFs.
Pilots really need to think about that when flying a Twin NDB or Twin Locator approach using just the one ADF. I suspect that the procedure designer got overridden on this, by people further up the food chain who, in turn, were being hassled by elements of the industry. It wouldn't be the first time that this sort of thing has happened.
I suppose that the practicality of the situation is that, as long as the two facilities are within about 5 miles of each other, there's very little risk of an aircraft leaving the protection area. Of course, if either of the facilities is a bit weak in power or earth mat, or there are CBs around, I reckon that all bets are off.
Pilots really need to think about that when flying a Twin NDB or Twin Locator approach using just the one ADF. I suspect that the procedure designer got overridden on this, by people further up the food chain who, in turn, were being hassled by elements of the industry. It wouldn't be the first time that this sort of thing has happened.
I suppose that the practicality of the situation is that, as long as the two facilities are within about 5 miles of each other, there's very little risk of an aircraft leaving the protection area. Of course, if either of the facilities is a bit weak in power or earth mat, or there are CBs around, I reckon that all bets are off.
If you use your two ADF's in the aircraft for the Twin Locator approach (regardless of the Australian AIP which now talks about a NDB rather than Twin Locator approach), then the closer you get to the runway (let us say in the case of Avalon, Victoria), the less accurate will be the bearing of the first locator you pass over, simply because of distance errors. On the other hand as you close in on the second locator, which is situated in the case of Avalon, only 0.57nm from the threshold, logically it is the more accurate.
So what is the point of having one ADF needle on a navaid that is getting progressively less accurate, when in practice it is the tracking on the one closest to the runway which interests you more. The only use of the first locator (8.1 nm from threshold) in the case of Avalon is for top of descent geographical postion. After all - you have to start down somewhere especially where in the case of Avalon the DME is not part of the procedure.
Once you have passed that point and descent is started, it is probably better to bring up both aircraft ADF's to the remaining locator for increasingly accurate track keeping and for redundancy in case one ADF should pack up (very unlikely unless you are having a bad day).
So what is the point of having one ADF needle on a navaid that is getting progressively less accurate, when in practice it is the tracking on the one closest to the runway which interests you more. The only use of the first locator (8.1 nm from threshold) in the case of Avalon is for top of descent geographical postion. After all - you have to start down somewhere especially where in the case of Avalon the DME is not part of the procedure.
Once you have passed that point and descent is started, it is probably better to bring up both aircraft ADF's to the remaining locator for increasingly accurate track keeping and for redundancy in case one ADF should pack up (very unlikely unless you are having a bad day).
