Easy question about the Bournemouth NDB/DME 26
 

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???

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.

Hi:
Can you post the approach plate?

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.

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

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.

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:}

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.

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

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

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?:)

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:

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

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

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!

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 :-

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.

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.PDFpictorial is how it is safe to fly. Indeed it shows descending turn.

FD
(the un-real)

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. 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

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).