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UK NDB only timed approaches

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UK NDB only timed approaches

Old 17th Nov 2020, 13:24
  #41 (permalink)  
 
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There is (was) a benefit to the NDB being located remotely from the field (typically approx 4 nm and coincident with the OM): timing from the beacon inbound gave a reasonably precise indication of range from touchdown. The disadvantage was interpretation of the back bearing on the ADF - it was easy to turn 'the wrong way' when the bearing wasn't correct. When I was doing IR checking in the sim I would brief:

Under the mental workload it'll be easy to turn the wrong way if the back bearing isn't spot on. Here's a dodge to help you - once you've passed the beacon, set up a heading which gives you the required track inbound. In other words you can ignore the beacon for a while. By the laws of physics, if you departed the beacon on the correct track then your back bearing will be very close to what's required. Later on when you've got a moment or two you can sneak a look at the ADF indications to check all is well.

In the sim there was the bonus of HSI readout of track made good but even without FMC the concept still applies - fly a heading which you estimate will give you the correct track.

Arguably another benefit of NDB approaches is (was) sharpening basic handling skills (and boosting confidence), more so when manually flown. We used to call this 'airmanship'.

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Old 17th Nov 2020, 13:31
  #42 (permalink)  
 
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I think your being optimistic. I am hearing stories of upwards of 200K being spent on getting GNSS approach approval and it’s still not approved after some 6 years.
Well i can't understand how it should come to £200,000. There is no physical infrastructure to provide. All costs are in the fees: aerodrome survey, stakeholder consultation, approach design fees and of course the CAA approval charges. The CAA are being very difficult and obstructive which itself adds to the cost. They are demanding, for instance, that ATC are in place for all procedures, and do not accept trained A/G, although the regulations do not require it. This will inflate the cost a lot where ATC do not already exist and may have been included in the hearsay. My estimate may well be out of date but it was an estimated cost a few years ago when I had some direct involvement in the process.

EASA are very keen that small aerodromes have a GNSS procedures at low cost and the regulations do not require ATC. It is a poor reflection on the UK that there are so few GNSS procedures in place at small aerodromes. PPL/IR have done a lot of work in supporting and promoting them but continue to hit a brick wall. Meanwhile individuals are designing their own procedures which soon become widespread amongst locals at a particular aerodrome and flown regularly.
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Old 17th Nov 2020, 14:17
  #43 (permalink)  
 
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Meanwhile individuals are designing their own procedures which soon become widespread amongst locals at a particular aerodrome and flown regularly.
Here's one I prepared for Turweston. The FF waypoints are labelled with the magnetic track to make good (ignoring noise abatement). The check alts are on QNH and equate to a 400ft/nm gradient. I can't guarantee its efficacy as I haven't flown it in IMC, so I'd only use it in extremis.




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Old 17th Nov 2020, 14:38
  #44 (permalink)  
 
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Discorde - does seem to be missing IAF, DA, and missed approach procedure. I'm not inherently against ad-hoc IAPs, but all of the formality that's there in the official ones is there for good reasons. Turweston is actually an excellent case, as it would readily lend itself to a day-only NPA, certainly GPS, and you might even get away with a VOR/DME approach onto 27 off BKY, and if you mandate ATC - well located where it is that could be provided by either Luton or Cranfield. But there is a lot more to a well designed IAP than simply flying GPS to the runway then landing.

(Also if you were in the vicinity desperate to land from above 8/8 you of course have multiple approaches at Cranfield, and if you're out of hours, can just apologise later after a safe landing!)

Fl1ingFrog - if you look up the dreadful mess made of the implementation of the IAP at Sywell, including correspondence from the airport accusing the CAA of trying to actively prevent it having any utility whatsoever (which they largely succeeded in achieving): the whole lot is online at the link below - you'll easily see where all the time and money went. The position isn't faintly defensible, but it's what it is has been to date.

https://www.caa.co.uk/Commercial-ind...al-procedures/

G
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Old 17th Nov 2020, 16:12
  #45 (permalink)  
 
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Originally Posted by TheOddOne View Post
Try the dreaded EX at Exeter. No idea why it hasn't been moved on to the airfield. Character building stuff, doing an NDB approach with the beacon behind you...

TOO
Push the head, pull the tail.
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Old 17th Nov 2020, 17:33
  #46 (permalink)  
 
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Push the head, pull the tail.
Follow the pink string...?


Iíll show myself out.
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Old 17th Nov 2020, 19:31
  #47 (permalink)  
 
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if you look up the dreadful mess made of the implementation of the IAP at Sywell, including correspondence from the airport accusing the CAA of trying to actively prevent it having any utility whatsoever (which they largely succeeded in achieving)
Why an environmental impact is necessary for an aerodrome that already exists is beyond me. Unless they believe that an aircraft in cloud impacts the environment more that an aircraft that is clear of cloud. Outside controlled airspace and subject to the low flying regulations a pilot can fly where and whenever they wish and do. This simple fact seems to fly over these bureaucratic heads. The LNAV approach they have approved is non precision and can be flown with a simple single channel GPS (i.e. without WAAS enablement) and this is exactly the kind of approaches pilots are already making up for themselves.

Those at the CAA who are responsible are stark raving bonkers and just don't get it. Small aerodromes are completely out of their scope of understanding but we should be grateful for small gains I suppose. They will be quite pleased with themselves.

Of course a plus can be that the LNAV will be published and therefore will be found in a downloadable nav. pack. It must be flown as a non precision procedure and whilst the flight is depicted contemporaneously on the screen it will still only give lateral guidance. The descent however must be managed in an imprecise way without guidance. How is that safer than a LPV precision approach with the guided descent that was applied for? .

Last edited by Fl1ingfrog; 17th Nov 2020 at 23:14.
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Old 17th Nov 2020, 22:54
  #48 (permalink)  
 
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I find it simultaneously uplifting and depressing when in contact with various parts of the CAA, as they manage to both look forward and backward at the same time. I think they are just beginning to realise that if they procrastinate for long enough, the rest of aviation goes off in whatever direction seems best at the time....
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Old 18th Nov 2020, 06:03
  #49 (permalink)  
 
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I just read the sywell documents. Wow.

I canít help but feel CAA have completely lost the plot. Itís seemingly obsessive about safety but in the face of making it less safe by being so restrictive, causing people presumably to simply not use their procedures.

unless in a mountainous region, or severely complex, why on earth does a GNS approach need all this nonsense?

its like making bicycle helmets so complex to buy and fit that nobody wears them.
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Old 18th Nov 2020, 09:53
  #50 (permalink)  
 
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Originally Posted by Genghis the Engineer View Post
[the procedure] does seem to be missing IAF, DA, and missed approach procedure.
Feel free to invent your own!
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Old 18th Nov 2020, 11:09
  #51 (permalink)  
 
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I must admit I have not had good experience of using NDB approaches in real IMC. Fortunately I have only used them when training (I have an IR(r) and FAA IR).
One on occasion coming into Filton rwy09 (shows how long ago it was) I was in real IMC; an instructor with me as it was a re-val test. I was flying it well - as the instructor agreed; needle just where it should be.
However, on shortish final ATC told us to abort and go around - we were 30degrees off track [still in solid IMC].
The weather was not that bad - only stratus cloud; no embedded CBs (maybe some CBs a distance away) - and the conclusion was coastal refraction plus the distant CBs had an effect (had seen coastal refraction effect at other times under the hood). Had to do an SRA in the end, which was not a problem, but it showed me how poor NDB guidance could be.

Second time was at Cardiff, went round the hold 10 times (!) in solid IMC, waiting for Easyjets to land etc. Another re-val test. Again the instructor agreed the ADF needle was spot on. Still on solid IMC we began the approach - all good - yet ATC told us to abort and go back to the hold as we were too far off track. (Ignored the ADF, just used the DI and timed the turn to do an ILS approach in the end.)

In both cases I would have had real problems if I had tried to land using the NDB alone.

I find it extraordinary that GNSS cannot be simply approved as an overlay on the same approach path as an existing NDB approach; surely all the issues of terrain clearance etc. have already been dealt with on the NDB approach? And GNSS is more accurate and reliable and not prone to NDB effects from a local CB or coastal refraction, and easier to interpret.
If there had been no NDBs and someone suggested NDBs now as an approach aid I would imagine that there would be many comments about its unreliability, safety issues etc. (certainly compared to GNSS) - not least from the CAA themselves.



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Old 18th Nov 2020, 12:03
  #52 (permalink)  
 
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Originally Posted by Discorde View Post
Feel free to invent your own!
If I was creating my own ad-hoc IAP I absolutely would, but it troubles me that some people doing so, haven't. Missed approach procedure seems to be most often missing, followed by Decision Altitude.

Of course, for as long as CAA make it virtually impossible to get affordable approved IAPs, people will be just sticking a few waypoints in their GPS and hoping for the best.

G

Last edited by Genghis the Engineer; 18th Nov 2020 at 12:26.
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Old 18th Nov 2020, 15:52
  #53 (permalink)  
 
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Come to Greenland.

BGJN, BGSF, BGKK, BGBW, BGCO, BGQQ, BGUQ all have them, though better options are available.

The one in BGSF is used when the localiser or DME falls out of service, which rarely happens.

But as everywhere else, things are slowly replaces by GNSS or RNP approaches.

Some locations can handle LNAV/VNAV minima, others only LNAV. There's no SBAS or GBAS coverage yet, so for the LNAV/VNAV RAIM is required.
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Old 18th Nov 2020, 21:58
  #54 (permalink)  
 
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Originally Posted by tdbristol View Post
I must admit I have not had good experience of using NDB approaches in real IMC. Fortunately I have only used them when training (I have an IR(r) and FAA IR).
One on occasion coming into Filton rwy09 (shows how long ago it was) I was in real IMC; an instructor with me as it was a re-val test. I was flying it well - as the instructor agreed; needle just where it should be.
However, on shortish final ATC told us to abort and go around - we were 30degrees off track [still in solid IMC].
The weather was not that bad - only stratus cloud; no embedded CBs (maybe some CBs a distance away) - and the conclusion was coastal refraction plus the distant CBs had an effect (had seen coastal refraction effect at other times under the hood). Had to do an SRA in the end, which was not a problem, but it showed me how poor NDB guidance could be.

Second time was at Cardiff, went round the hold 10 times (!) in solid IMC, waiting for Easyjets to land etc. Another re-val test. Again the instructor agreed the ADF needle was spot on. Still on solid IMC we began the approach - all good - yet ATC told us to abort and go back to the hold as we were too far off track. (Ignored the ADF, just used the DI and timed the turn to do an ILS approach in the end.)

In both cases I would have had real problems if I had tried to land using the NDB alone.

I find it extraordinary that GNSS cannot be simply approved as an overlay on the same approach path as an existing NDB approach; surely all the issues of terrain clearance etc. have already been dealt with on the NDB approach? And GNSS is more accurate and reliable and not prone to NDB effects from a local CB or coastal refraction, and easier to interpret.
If there had been no NDBs and someone suggested NDBs now as an approach aid I would imagine that there would be many comments about its unreliability, safety issues etc. (certainly compared to GNSS) - not least from the CAA themselves.
I am not an instrument-rated pilot (I gave up in the middle of my IMC training almost 30 years ago) but I think this account tells it's own story.

As CJ1234 said, "Quite agree. the NDB (approach) should have gone the way of the dodo decades ago."
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Old 19th Nov 2020, 01:30
  #55 (permalink)  
 
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Originally Posted by Forfoxake View Post
I am not an instrument-rated pilot (I gave up in the middle of my IMC training almost 30 years ago) but I think this account tells it's own story.

As CJ1234 said, "Quite agree. the NDB (approach) should have gone the way of the dodo decades ago."
Not until something else replaced them. More than once snow banks or snow ploughs somehow dissabled the ILS at DTW. Yes, dive and drive, push the head, pull the tail got us in. But it is good that nobody has to dive and drive anymore. That was a recipe for a mishap whether you were flying an NDB, VOR or LOC only.
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Old 19th Nov 2020, 10:21
  #56 (permalink)  
 
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Plenty of companies could make new, cheap NDBs, and it wouldn't be hard to make a more accurate better, modern ADF incorporated into other systems.

I'm entirely with jimtx on this. They are cheap and robust, need a fraction of the infrastructure of an ILS or VOR. We cannot just rely upon GPS as our sole mechanism for approaches - if that backup isn't NDB/ADF, what should it be?

G
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Old 19th Nov 2020, 11:38
  #57 (permalink)  
 
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A second GNSS receiver capable of using GLONASS and Galileo?
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Old 19th Nov 2020, 12:19
  #58 (permalink)  
 
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Originally Posted by eckhard View Post
A second GNSS receiver capable of using GLONASS and Galileo?
Does make you all rather reliant upon a single technology, although if it's demonstrably in different frequency ranges and using different satellites - perhaps.

As INS isn't accurate enough (by a LONG way) whilst I can absolutely see value in a second GNSS receiver, I'm inclined to think that we need a beacon based backup system. (Or more widespread availability of GCA I suppose - I'm pretty certain that none of us want to start making a habit of VDF !).

G
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Old 19th Nov 2020, 15:23
  #59 (permalink)  
 
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NDBs need to produce power dependent on the range required due to attenuation. As an enroute aid a lot of power was important but as a locator the power can be reduced and therefore causing less interference elsewhere. As the demand for radio frequencies increased the CAA required the power of locators to be turned down to quite a low power. The VDF indicator is a motorised unit and so signal strength is important to drive it. All the things that can cause interference also became increasingly difficult to manage: electrical storms, coastal effect, night effect, airframe static and last but not least the interference from one beacon to another. All these things always existed but were more manageable with the higher power. Dead reckoning was once the norm of course and enroute aids were just that, aids. The locator NDB was simply a cloud break aid that put you somewhere close to the place you wanted to be, the runway threshold. Plus or minus a few hundred metres being common and acceptable which is difficult to understand nowadays when a WAAS GPS will place you within 3 metres in two dimensions.

Perhaps a digital format for such a very simple pointing radio. A digital NDB enabling the receiver to discriminate between the wanted, the unwanted and noise. The ADF wouldn't need to be motorised either but rather a digital display with much improved sensitivity. I await to hear from those with radio engineering expertise. I'm very aware that I could be spouting nonsense regarding such an idea.
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Old 19th Nov 2020, 17:13
  #60 (permalink)  
 
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It's not nonsense you are spouting, at the contrary. It is so much common sense that even "the powers that be" thought along the same lines. They even managed to make something workable out of it, it is called "satellite navigation". (also known as "GPS" to those unaware of other satellite constellations, Glonass, Galileo, &c)

if that backup isn't NDB/ADF, what should it be
For en-route navigation, I always understood EASA intended a network of DME stations, whose data could/would/should be triangulated into location/heading/speed information just like one gets from GNSS. But I seem to remember this idea has been shelved, and am not aware of any alternative plan. Still less information about any plan B against GNSS failing on instrument approaches. But was there any plan B on any NDB approach if/when the NDB should fail?

Last edited by Jan Olieslagers; 19th Nov 2020 at 17:23.
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