Easy question about the Bournemouth NDB/DME 26

[machlimter99]

Sorry quite an easy question, but ive forgotten! When tracking outbound to 6.5 nm you descend to 2030ft, however when do you start the descent to 1530 at 4.5nm where the FAF is located. Do you start the descent in the turn inbound, or when you are inbound passing 6.5 nm again???

[Flying Farmer]

Start the descent in the turn down to not below 1530 the 6.5 DME is only there to indicate the inital right turn to intercept the 256 inbound.

[albatross]

Hi:
Can you post the approach plate?

[Rainboe]

I'm not familiar with the specific approach, but you should wait to commence the descent until you are within 5 degrees of the correct QDM in which case you may then continue the step descent. There is not always a specific point, but there will be a generous enough allowance to get you down allowing for track adjustment to put you in the funnel.

[Flying Farmer]

Its still early brains not functioning fully yet !! Rainboe I was thinking you had to be within 5 degrees before you commence the descent from the FAF :confused: ie : 4.5 DME to the MAP

[Flying Farmer]

http://i1.tinypic.com/nn7e5s.jpg

[Pilot Pete]

If you look at the approach plate as attached above, the key is in the way it is drawn. You go outbound descending to 2030'. You must not go below 2030' until you reach 6.5d. Then you turn back inbound and if you look at the profile view it shows a DESCENDING TURN to the inbound final approach track, not below 1530' until 4.5d and within your normal 5 degrees of the final approach course.

Compare it to a procedure which shows a level base turn, ie down to a platform altitude, turn base to final and then descent from FAF. The way these are drawn in profile shows the base turn as a horizontal line, not like the one reproduced above.

PP

ps edited to add, if you look at the altitudes (and the heights based on QFE below them), there is another key to how you descend. When it has a line underneath it means 'not below', so the 6.5d point is not there purely to show you when to turn, it also says 'not below Altitude 2030/ Height 2000' at that point before commencing the turn. You can be 'above' 2030' if you want and if you want to fly a profile with as few changes in pitch and power as possible, you may well elect to be. Take a look at other charts which show an altitude with horizontal lines both above and below it, which means be 'AT' this altitude, and ones with just a horizontal line above the figure which means be 'BELOW' (common on SIDs). If you are in doubt take a look at the key which is in the Aerad Suppliment or Jeppessen Text manuals.

[haughtney1]

Gosh this brings back a few memories, bashing about in a Duchess around that bloody holding pattern! During my UK IR conversion.

Hey Pete its a bit easier these days to punch it into the FMS and monitor it in raw data:}

[Rainboe]

I can see the confusion, but the way I read that, maintain 2030 during the turn until you are passing the 251 QDM then continue descent to 1530 for the FAF. The remaining within 5 degrees only after the FAF does not seem right. Consider if you made a horlicks of the tracking outbound, then pressed on after the turn down to 1530- the MSA in that sector may be 2300, and you have legally descended to 1530 and you are way off track.

[Flying Farmer]

I hope I'm right in thinking the tracking outbound shoud be within limits as well !! keeping you within the protected area.

Fully agree with PP the plate shows a descending turn to intercept the inbound, once within the 5 degree limits call base turn complete.

This Alderney plate shows a level base turn, hope this clears matters up.

http://i1.tinypic.com/nn9rfm.jpg

[Pilot Pete]

I hope I'm right in thinking the tracking outbound shoud be within limits as well !!

Indeed you are, that's where Rainboe has it wrong. His argument that if your tracking was crap outbound meaning that you weren't in the correct position for further descent assumes that you aren't tracking within the required 5 degree limit....well, whenever you are tracking an aid you should be doing it within limits!

Like I said before, look at the Jepp Text or Aerad Suppliment or the AIP for the 'map key' which describes these drawings. I guarantee you that that chart depicts a DESCENDING TURN onto the final approach track. By staying high when a chart depicts a descending turn CAN mean that you are too high to complete descent once established on the final approach track, so be warned (not in this particular case though.)

PP

[BOAC]

Yes - I'd do a descending turn (from 2030ft if I had to!) although as 'pilot pete' says, to be at 2030ft at 6.5 DME for a 3 deg approach is not too far off (about 44ft?:eek: ), so I would also be 'high' around that turn, which would keep Rainboe happy.......?

Of course, if Rainboe is NOT within 5 deg of the Cat A/B outbound 062, he would still be at 3000ft, no?:)

[OzExpat]

Is all 25NM MSA data on UK charts referenced to the ARP? That is certainly very useful for GNSS navigation, but not very helpful when using a NDB approach... unless the NDB and ARP are co-sited, of course! :eek:

[Pilot Pete]

Yes - I'd do a descending turn (from 2030ft if I had to!) although as 'pilot pete' says, to be at 2030ft at 6.5 DME for a 3 deg approach is not too far off (about 44ft?:eek: ), so I would also be 'high' around that turn, which would keep Rainboe happy.......?

Of course, if Rainboe is NOT within 5 deg of the Cat A/B outbound 062, he would still be at 3000ft, no?:)


If you look at the bottom right hand corner of the chart it gives alt/dme advisories. If you do a little bit of mental arithmetic you can see that the descent per nm is 320'. You can then extrapolate to get crossing altitudes further away from the field than the 4.5d FAF point. Let's look at what this gives;

9d 2960'
8d 2640'
7.5d 2480'
7d 2320'
6.5d 2160'
6d 2000'
5d 1680'
4.5d 1530'

Now these are based on DME distance, but as you can see 'note 2' says that the DME reads zero at the threshold. So these are also distance to touchdown altitude checks. Very useful in an EFIS equipped aircraft as you can draw the procedure in 'pink string' and then the FMC gives distance to touchdown. You can extrapolate as much as you want and come up with a suitable altitude to cross the beacon going outbound (which will be significantly higher than the procedure minimum IAF) and then fly a constant descent approach with minimal power, thus keeping the local residents (relatively) happy.

Nothing wrong with extrapolating and getting a 'sensible' ball park figure for crossing 6.5d outbound; say you will fly about a mile in the base turn and you can see from above that at 6.5d inbound you want to be at 2160', therefore a mile before that means you want to be at 2480', round that to 2500' and bingo, a sensible altitude to cross 6.5d outbound to give you a constant descent approach. Be warned if you are doing all this as IR training you may just want to keep it simple and fly the chart as this is asking for you to co-ordinate a lot of things all at once! Crack the basics first! Also bear in mind that there is no decelleration phase in the above procedure, so if your aircraft type won't descend on a 3 degree descent path AND decellerate you will have to alter you profile to allow a little 'level decelleration'.

Some may be surprised to hear that when flying big jets we often extrapolate (or even calculate) descent crossing altitudes and write them on a bit of quality hotel note pad paper which we use to get a constant descent! It's all about flight planning and staying ahead of the game. It's easy to spot the guy who has just briefed the procedure but given little thought to how he is actually going to fly it....

Remember, non-precision approaches lead to more accidents and incidents than any other phase of flight. Be safe.

PP

[Pilot Pete]

Is all 25NM MSA data on UK charts referenced to the ARP?

No it is not. Sometimes ARP, sometimes a VOR or NDB, even one off the field. In this particular case you can use the DME and make a 'sensible' airmanship decision that you are not below MSA going outbound on the procedure until descending below 1900'.

That said, you couldn't guarantee it when 'about' 25nm from the field using your DME equipment.

Another interesting point about MSA that I was never taught during IR training is that the MSA is valid for EMERGENCY USE ONLY unless you have checked the chart notams for the aerodrome(s) in question. I don't mean notams, I mean the chart notams from the chart manufacturer which describe any changes between chart publication dates. You would be amazed at how much does change between one plate being published and it's next update. That will impress your IR instructor/ examiner!;)

PP

[fireflybob]

If available always worth looking at the state AIP for the defined procedure when there are (apparent) ambiguities - this is often in "text" form as well as pictorial.

It's also worth mentioning that chart makers such as Aerad/Jepp have "disclaimers" concerning errors!

[OzExpat]

Thanks PP and MJ. I still can't help wondering why, in the two charts posted, the MSA would be predicated on the ARP. This became relevant to me after I saw the following comment by Rainboe :-

Consider if you made a horlicks of the tracking outbound, then pressed on after the turn down to 1530- the MSA in that sector may be 2300, and you have legally descended to 1530 and you are way off track.
My immediate reaction to this was that I'd use the MSA because both the O/B and I/B tracks are in the same quadrant for the Bournemouth approach. But, of course, then I saw that the MSA wasn't referenced to the navaid.

I recognise that the navaid is pretty close to the ARP, but if (as suggested in the scenario described by Rainboe), O/B tracking wasn't very accurate, I wouldn't be inclined to bet my life on the difference in the 2 positions. That said, it doesn't seem to be unsafe to adopt the closely adjacent MSA sector altitude of 2300 feet until established on track - either O/B or I/B - before further descent. There'd be enough distance between 6.5d O/B and 4.5 d I/B to regain profile.

I guess the only problem with this plan is that you're accustomed to the MSA being only available for "emergency use". In my small corner of the planet it is available for normal use and is used that way quite often.

[FlightDetent]

If available always worth looking at the state AIP for the defined procedure when there are (apparent) ambiguities - this is often in "text" form as well as pictorial.


Over here the text description is ALWAYS present in AIP and binding. However it is not present in the AIP UK. So, I gather the AIP http://www.ais.org.uk/aes/pubs/aip/pdf/aerodromes/32HH0808.PDF (pictorial)pictorial is how it is safe to fly. Indeed it shows descending turn.

FD
(the un-real)

[Pilot Pete]

...I'd use the MSA because both the O/B and I/B tracks are in the same quadrant for the Bournemouth approach. But, of course, then I saw that the MSA wasn't referenced to the navaid.
I recognise that the navaid is pretty close to the ARP, but if (as suggested in the scenario described by Rainboe), O/B tracking wasn't very accurate, I wouldn't be inclined to bet my life on the difference in the 2 positions. That said, it doesn't seem to be unsafe to adopt the closely adjacent MSA sector altitude of 2300 feet until established on track - either O/B or I/B - before further descent. There'd be enough distance between 6.5d O/B and 4.5 d I/B to regain profile.

Not sure I get you there? If you are flying the PROCEDURE you should stick to the procedure. You can't go outbound at 2300' because it is BELOW the minimum altitude overhead the beacon for starting the procedure. You need to be at 3000' or above to start this procedure. Consider if you made a horlicks of the tracking outbound, then pressed on after the turn down to 1530- the MSA in that sector may be 2300, and you have legally descended to 1530 and you are way off track. If going outbound your tracking is more than 5 degrees off, then you are not descending LEGALLY. MSA in the sector at the end of the outbound leg is 1900', so you are not going to hit the ground as long as you stay inside that quadrant, but you must not be below 2030' at 6.5d to comply with the procedure. If you get yourself successfully to 6.5d and you are above 2030' you may commence your descending turn back inbound to 1530'. If the tracking was bad outbound there is no LEGAL descending to 1530' and hence you are compromising yourself both in terms of safety and legality.

Greater brains than mine will be able to post a link to the way these procedures are constructed and describe the built in safety margins. One of these will be for the descending turn back inbound as you are not tracking anything at that point, merely dead reckoning on your rate one turn. This will be one factor why you have to be at 2030' feet at the 6.5d point outbound.

Remember that there is a difference between procedure minimum and MSA - procedure minimums will not only keep you terrain safe, but also possibly may prevent interaction with other traffic/ procedures. MSA will only keep you terrain safe. If your tracking is badly off and you are on a procedure (or supposed to be) below MSA then I would suggest some prompt corrective action, not trying to cobble together the turn back inbound.

PP

[Rainboe]

It was hard commenting on this Hurn approach without seeing the chart. I think I was being overcautious wanting to be within 5 degrees of the inbound QDM before leaving 2030', but even doing that should not mess up the descent. I do have issues with those of you insisting on being within 5 degrees of the outbound leg- have you ever tried overflying and establishing on a new outbound radial and staying within 5 degrees? Until you get at least a few miles out, you can't really establish, so 5 degrees is a bit tall. BUT, if the chart shows a descending turn down to 1530' from the 6.5 DME position, who am I to argue? I don't like it, but should I have ever tried to do this in a 747, I would be hanging onto 2030' as long as possible! (But then it would be easy- select 1500' after the final turn, VS down to put the descent line on IBS 4.5 DME and finish the crossword).

[InSoMnIaC]

Rainboe - I do have issues with those of you insisting on being within 5 degrees of the outbound leg- have you ever tried overflying and establishing on a new outbound radial and staying within 5 degrees? Until you get at least a few miles out, you can't really establish, so 5 degrees is a bit tall

I get your point but u need to be +- 5 degrees outbound inorder to descend from 3000' to 2030' outbound

[Pilot Pete]

I do have issues with those of you insisting on being within 5 degrees of the outbound leg- have you ever tried overflying and establishing on a new outbound radial and staying within 5 degrees? Until you get at least a few miles out, you can't really establish, so 5 degrees is a bit tall.

If you are flying on 'raw data' in whatever aircraft type, if you cannot get yourself within 5 degrees on an outbound leg of a procedure then you will NEVER pass an IR skills test. It is a basic requirement of instrument flying and I don't recall it taking 2nm, even in a Seneca for the needle to start pointing at the beacon again once you have passed the overhead.

Safe flying.

PP

[Simoes]

Hello! I´m from Brazil and I fly as a B737 for GOL Airlines. I´m also the tecnical advisor for our Technical Vice-President. I wonder if you could help me with some advice about the laptop tool. If not, maybe you could tell me someone who could help me with that issue. My e-mail is: [email protected]. Thanks!

[OzExpat]

PP... Perhaps I worded my previous post a bit clumsily but the fact of the matter is that, once beyond the beacon in this particular procedure, I can see nothing at all wrong with descending from 3000 feet to 2300 feet, whether I'm on track or not. I'm simly using the worst case MSA to limit my descent on the outbound leg and, after all, this is higher than the 2030 feet minimum stated in the procedure.

I can use that descent while maneouvring to intercept the outbound track by no later than 6.5 DME. There's some pretty simple pictorial maths that will help me to achieve that and so, once there, I can simply establish a 3-degree descent during the turn to the inbound and I'll be at 4.5 DME at the appropriate limiting altitude. Therefore, I'll be able to continue the descent on track.

I've been a procedure designer for 20 years and have been flying approaches for a lot longer than that. I like to look at all the information on that chart, to help me plan a simple, safe approach that keeps me stablilised on a 3-degree approach as much as possible. When I devise an approach, I take all of that into consideration as well.

Incidentally, in this part of the world, there is no requirement to be established on the outbound track until the DME limit, or expiry of the outbound time limit (if there's no DME limit quoted). The only proviso is that the pilot must be on an intercept heading - i.e. no sustained off-track error that might cause the aircraft to leave the protection area. This was done in recognition of the fact that aircraft can enter the outbound leg of an approach from a 30-degree offset and is unlikely to be able to positively identify the outbound track until beyond the NDB - due to the entry track, perhaps exacerbated by thunderstorms, coastal effect, etc...

Somoes... I'm sorry, what sort of laptop tool are you referring to?

[Pilot Pete]

Oz I completely agree! It's all in the power of the written word (or lack of!), I am sure over a beer we would have sorted this one much sooner! I completely agree that above MSA you can be where you want until the defined point at the end of the outbound leg, but, and this is for the inexperienced posing questions here, it must be within reason. For instance, I had a training partner during my IR training who went over the beacon once in a hold and never got over it again after 3 holds!!!:eek: It is worth bearing in mind that in a procedural appraoch ATC will be separating traffic from position reports by the traffic, so if not where you are saying you are there could be poblems! Also, for an IR test you would fail due to inability to track, even if you were above MSA and safe!

PP

[machlimter99]

Thanks for the above replies.

A question about this business of 5 degrees outbound. For instance, I realise you would fail an IR test, however why do some plates then have different outbound legs for different classes of aircraft? For instance, an example. If you were cat C or D in your B757 you may be tracking outbound say at 65 degrees + 5 degrees = 70 degrees -and your STILL safe; HOWEVER if you were flying your Piper (cat A) you may be tracking 60 degrees outbound ( or whatever the plate said -due to the radius of turn) +5 degrees = 65 degrees. However, if you were tracking 66 degrees outbound you would be illegal and UNSAFE??? So whats different??!!! The only thing is the type of aircraft used.

I'm playing devil's advocate now;) but just wondering???!!

[Pilot Pete]

why do some plates then have different outbound legs for different classes of aircraft?
Because different classes of aircraft fly at different speeds, hence their radius of turn will be different, i.e. faster = greater radius of turn, hence a 'greater' angle outbound.

PP

[OzExpat]

Concur PP, I was most assuredly forgetting about the inexperienced folks. As for the bloke who couldn't find the aid after 3 times around the hold... well, at least we know that we won't be sharing the same airspace with him in IFR conditions! :D Doubtless we'd still be able to sort out a few of aviation's ills and furphies over a glass of something alcoholic... I hope to have such an opportunity in London around August, or thereabouts. :ok:

machlimter99, just to clarify the response to your question by PP, you'll notice that, even though initial approach tracks vary, the final approach track is common to all. The splay between the various outbound tracks and the single inbound track is designed to accommodate the radius of turn at the maximum speed for the aircraft category.

It's certainly true to say that, if you are 5-degrees, or more, off track in your Cat. A or B aeroplane, you're still likely to be within the procedure protection area. However, there is a very remote possibility that your slow speed aeroplane might be blown outside the protection area during the base turn, as you are not where you're supposed to be and, therefore, any residual protection is a function of the airspeed used by the higher category aircraft for the same base turn.

This possibility arises because you're in the situation of having to turn through more degrees, which will therefore take longer and, in an adverse wind situation, you will drift further away from the beacon and therefore face the possibility of an excursion beyond the protection area.

The far more likely problem however is one of practicality. The larger turn will take longer to complete and it will therefore take you longer to establish the aircraft within the legal tracking tolerance and, therefore, cannot descend in the final segment so readily. While you're struggling with the intercept, you're getting closer to the beacon (and the missed approach point too, of course).

Each procedure is designed in such a way that it will provide enough time to descend to MDA (indeed to descend to threshold crossing height) in the final segment. You're already using up quite a bit of that time just to join final approach and will therefore be most unlikely to have enough time available to reach MDA in an orderly and safe manner.

All of that having been said, as an examiner, I have failed candidates who can't stay within their tracking tolerances in any segment of an approach. And, yes, I once failed a candidate in the very situation under discussion. My reasoning was that, as he couldn't get the basics right, he didn't deserve the qualification.