Two questions,
1) Anyone can describe “w/o DME procedure”?
ROU VOR sists outside final track but serves as marker for the glide path and range check
2) Can I fly ILS with direct ROUBO? with missed loaded from GPS?
It’s not an IAF and sits 1.7nm before FAF, on raw data it’s not an issue but doing that on GPS overlay I get “approche not active”
With DME: Maintain 2500 ft from ROUBO to D6.3 RN, then follow the GS and crosscheck alt at D4 and then the minimum.
Without DME: Maintain 2500 ft to ROUBO, then descend to 2420 ft and fly to ROU, then follow the GP to MDA.
ROUBO’s position would have to be verified by GPS or other means without DME.
I would say the LOC approach can’t be flown without DME. Also the altitude check at D4 can’t be done on the ILS, which rises the question if it’s legal or if so advisable to fly it without DME or another means of checking that position.
I try to shy away from discussing legalities 
Let’s assume it’s all legit:
Mooney_Driver wrote: Mooney_Driver wrote:
Also the altitude check at D4 can’t be done on the ILS
In that case, Outer Marker is ok for ‘4nm check’ of the glide path, the OM is listed on the plates, so I suppose VOR+OM are legally required if DME is not available?
Without DME: Maintain 2500 ft to ROUBO, then descend to 2420 ft and fly to ROU, then follow the GP to MDA
The VOR is clearly not on LOC final, so you fly outside LOC to VOR? or you stay on LOC and nip VOR cone?
That would be an interesting experience on AP coupled to ILS
Mooney_Driver wrote:
I would say the LOC approach can’t be flown without DME
My gut feeling YES, strictly speaking I can’t see what prohibits flying LOC down to 1730ft MDA without DME if you have an OM, you can go missed at OM?
Ibra wrote:
The VOR is clearly not on LOC final, so you fly outside LOC to VOR? or you stay on LOC and nip VOR cone?
Stay on the loc and nip the VOR cone, either with the RMI or when the flag changes (Track like the LOC). Form the chart, I don’t see that the VOR is not on the loc, but this should not make a problem, as you need a position abeam or at which you need that altitude.
They actually have an OM? I only see that D4 fix. If it’s not there, that check can’t be done.
On the LOC, they define this to be a CDFA, so you would have to descend to the MDA on a 3° glide. However, the ground clearance changes at 4 DME. so I’d be very vary to descend to that MDA without having a clear idea how to check that point.
Of course, in reality, you could use the GPS distance to (if available) RN or to the ARP, you’d end up a tad high but safe. (4 NM from the ARP is closer to the runway than D4 RN)
Mooney_Driver wrote:
I would say the LOC approach can’t be flown without DME.
I would say that it can, given that the plate includes information to determine the MAPt by timing.
There is an Outer-Marker OM ground station, see AIP plates, we hiked nearby once but usually it does not ring in my cockpit GMA
Let’s get the obvious out of the way: the ILS can be flown without DME, the integrity of glide path can be validated by VOR and OM
Now for LOC/VOR, without DME, I sure less sure about the following:
Do you have to overfly VOR or stay on LOC? and which one you set as primary guidance?
Any change in minima? 2D NPA approach without DME is probably named ‘timed VOR/LOC’
Ibra wrote:
There is an Outer-Marker OM ground station, see AIP plates
It’s odd that it is not charted on the Jepp plate.
Those IM, MM, OM are usually missing in the plates or not working…I even wonder if they are really required for approach? and how they are treated for substitution?
Ibra wrote:
There is an Outer-Marker OM ground station, see AIP plates, we hiked nearby once but usually it does not ring in my cockpit GMA
Ah, ok, then it’s easy. Simply why don’t they put it in the chart…
Ibra wrote:
Do you have to overfly VOR or stay on LOC? and which one you set as primary guidance?
I would say stay on the loc, like on the ILS.
Actually, how far off is it? Would you see a deflection?
In reality – you use the GPS to fly at 2,500 towards ROUBO, intercept the localiser, then descend with the glidepath. If you have a DME, you cross check at intercept / D6.3 and D4.0; if you don’t have a DME you cross check at the VOR; it won’t be precisely at 2,420ft because you will be in/close to the dead cone above the VOR.
This is safe – the purpose of the FAF is to provide an error check to catch gross altimeter setting errors, false glideslopes or misdialed nav-aids, so as long as you have that position check before you go below 2,420ft after ROUBO you don’t bust anything. In theory, you should descend imediately to 2,420 from ROUBO, so if an persnickety wannabe-examiner points that out, you just respond that you arranged your descent to arrive at/abeam the VOR at 2,420 and were never below the profile, so there…
The non-DME LOC is a timed approach. The localiser should be intercetpted at ROUBO; but the missed approach point has to be determined by timing. So you start your descent above / abeam the VOR and start the stopwwatch, then descend with a ROD appropriate for the GS and go missed at the appropriate time – both the ROD and time are helpfully on the plate.
If you start at 2,420 and fly the rightt ROD, you should be exactly at the minimum when you hit the time. If you arrive at the minimum before the time is out, you can level off or go around; but you must go around when the time is out.
Presonally – with no DME, this is an approach that will work better if you don’t mind a bit of “dive and drive”: You choose a slightly higher descent rate, which leads to a level off at the minimum ahead of the time running out; unless that ROD is silly you will not bust the interim step-down minimum of 920’. But that is a matter of taste.
