Melbourne 16 NDB - ADF selection policy, if any

[A37575]

Melbourne Runway 16 NDB approach chart. Two questions:
It seems that DME is required for this approach. If that is the case should not the title of the approach chart be NDB DME RWY 16?

A chart note states both NDB are required for this approach. I can understand that in that you obviously need BOL for top of descent and ROC for the last check point prior to continuing descent below 1250.

Some argue that the note is meant to convey that after leaving BOL on final the crew must leave one ADF on BOL throughout the final approach and the second ADF (if installed) tuned to ROC. On the other hand if the aircraft is equipped with only one ADF, then clearly after leaving BOL, the single ADF must be re-tuned from BOL to the NDB ahead that is ROC.

Having made that point, why do some maintain that, where two ADF's are installed in an aircraft, then after leaving BOL on descent one ADF should remain on BOL for the approach - rather than tune ROC on both ADF's?

If it is a safe procedure to tune ROC after leaving BOL for an aircraft with single ADF installation (no choice of course) is there a legal or procedural why both ADF's should not be on ROC (after leaving BOL) After all, it could be considered good airmanship to have both on ROC since if one ADF fails the other ADF is already in place as good back-up.

[ZappBrannigan]

If that is the case should not the title of the approach chart be NDB DME RWY 16?They've removed the DME component from the chart titles - all the VOR/DME plates are now just titled "VOR Rwy 34" etc.

Having made that point, why do some maintain that, where two ADF's are installed in an aircraft, then after leaving BOL on descent one ADF should remain on BOL for the approach - rather than tune ROC on both ADF's?

If it is a safe procedure to tune ROC after leaving BOL for an aircraft with single ADF installation (no choice of course) is there a legal or procedural why both ADF's should not be on ROC (after leaving BOL) After all, it could be considered good airmanship to have both on ROC since if one ADF fails the other ADF is already in place as good back-up.Haven't flown this approach (or anything involving multiple NDBs) but I'll have a crack at it.

Off the top of my head, I'd say that this is the exact reason why you wouldn't want both ADFs tuned to the same NDB - at least in the aircraft I fly, if one ADF went bang, I'd still have the ident going in my headset (from the good ADF), and there'd be no handy OFF flag to tell me the other one had failed. So I'd be looking at 2 needles, potentially pointing in different directions, and be unaware which was the correct one. With one ADF tuned, if it goes bang, you are immediately aware, carry out your missed approach and have another go with the 2nd ADF - nice and procedural.

[Kelly Slater]

Ask Thai Airways, they should be the experts on this approach now.

[By George]

It really depends on your aircraft set-up. It is technically no longer a 'Twin NDB' bur you still need both compasses and the ML DME. On a EFIS Boeing,for example the 744, on the NAV RAD page both Left and Right are manually tunned to the ML VOR to get the DME. The Left NDB is preselected to BOL and the Right to ROC. On the EFIS control panel on the glareshield 'ADF L' is selected and the left VOR/ADF switch is selected to 'ADF'. The 'PF' stays on 'MAP' and the 'PM' goes to 'Centre Map' to monitor the needles 'raw data'. The approach is flown in LNAV and at the descent point of 11.5 miles V/S of 800ft/min, if not much wind you might need 900ft/min. Once established you then reverse the EFIS selection, ie. VOR/ADF switch Left goes to VOR and the right to ADF. Still have the DME and now tracking on ROC to min. PM calls out heights. On our fleet the approach is not in the data base. On the 'LEGS' page we only have BOL, ROC and the RW. Thats all you need despite some of the 'FMC Geeks' saying otherwise. You can 'build' the approach with every crossing height, but it's not SOP where I work and I agree with them, it's too easy to make a mistake. 'cos the 747 is a dinosaur we also have on the Capt's side an old round dial with RMI pionters VOR/ADF so I can cross-check Raw Data aswell. The 777,for example does not have this. (its called progress).

[Capn Bloggs]

Depends where the NDBs are actually loctated but, if you have two ADFs, set the No 2 on the first NDB and the No 1 on the second NDB and leave them. Tracking when between the NDBs is then is too easy: simply turn in the direction of the pointer pointing forward until both needles overlay and you're perfectly on track. Missed Approach or continuing? Use the No 1 needle.

It seems that DME is required for this approach. If that is the case should not the title of the approach chart be NDB DME RWY 16?
As pointed out by Zapp, this was changed a while back to facilitate the FMS naming convention. It was not possible to add "DME" or some other code to the end of the FMS name, as there weren't enough spaces.