DME dropping out flying to Stornoway

[Jon Budworth 0]

Hi,

I'm flying the excellent Jetstream 41 sim. I've got a slight glitch though which I'm not sure is the Jetstream or an FSX issue. When I'm flying to Stornoway the DME, STW 110.90, drops out at 28 miles. Can anyone help?

Cheers,

Jon.

[JRBarrett 3,050]

I assume that 110.9 is an ILS approach at Stornoway airport (EGPO)? If so, 28 miles is the typical limit in the sim. The real ILS/DME might go a bit farther, but not much. These facilities use low power to avoid interfering with other airports that may share the same ILS frequency.

If you are trying to navigate to EGPO from a distant location, you would want to use Stornoway VOR (STN) on 115.1, which has a much greater range.

 

Edit: I see the approach is for the ILS/DME 18 at EGPO. If you are flying the procedure as published, you should not go much more than 10 nm from the airport before turning back inbound in a procedure turn. 28 miles is definitely too far.

[Jon Budworth 0]

Hi Jim,

Thanks for the reply.

110.90 is needed for the LOC/DME approaches for both runways. Both approaches begin with a DME arc based on 110.90. When approaching Stornoway from the East 110.90 works up until 28 miles and then as I get closer it drops out. Therefore I'm not able to continue with the published approach.

Does that help?

Thanks,

Jon.

 

[downscc 1,327]

34 minutes ago, Jon Budworth said:

When approaching Stornoway from the East 110.90 works up until 28 miles and then as I get closer it drops out.

That's a puzzle,  if 110.90 is the LOC/DME then I don't understand how you receive it more than 28 nm out...as Jim said FSX/P3D has limited localizer range which is unrealistic in many cases but it's a hard limit. So, first question is what are you receiving on 110.90 before the DME drops out? Did you check the IDENT to see if it is what you think it is?

[Jon Budworth 0]

Hi Dan,

It's definately the right Nav aid. Until range is displayed it shows STW. It begins to show DME range at 37.5 miles at FL100. At 28 miles, ie as I get closer, it drops out at approx 28 miles.

Jon.

 

[downscc 1,327]

16 minutes ago, Jon Budworth said:

Until range is displayed it shows STW.

Is STW the VOR or the LOC/DME?  Wait a minute... I'll grab the charts and have a look.  Yup STW is the LOC/DME. However, you shouldn't be on the LOC/DME STW until you begin the procedure. The IAF is SAY NB from which you fly the outbound then procedure turn then intercept STW LOC/DME.  Unless you are on one of the STARS use SAY 431 kHz inbound.

 

[Jon Budworth 0]

Hi Dan,

I totally understand what you're saying but to fly an arrival, lets say for runway 18, and then a LOC/DME approach you need the STW to display range so as to initially get onto the 11 DME arc, which is based on the STW. The final approach fix is D6.1 from STW. What's happening is the DME starts to work at 37.5 miles, which I agree is quite far out from the field, but then stops working at 28 miles and doesn't start working again, even when really close to the field. I think it may be a glitch in either FSX or the Jetstream sim.

This is a procedure I want to practice as it is the procedure my airline uses when flying into Stornoway.

Jon.

[Jon Budworth 0]

Further to my last post. I've just had an email from my Dad who tried the same route on his PC using a different aircraft. He had exactly the same problem, The DME appeared at 38 miles and then stopped working at 28 miles. I think this points to the fact that it's probably a glitch in FSX itself.

Jon.

[Chock 17,769]

Looks to me like it is busted in FSX, couldn't get 110.9 to pick up at all. The VOR on 115.1 is working okay, but I get nothing from 110.9.

[Jon Budworth 0]

Try flying from Inverness to Stornoway. You should pick up STW at approx 38 miles but then it'll drop out at approx 28 miles. And yes I agree, the VOR STN is working fine.

[borgfan 1]

I believe the issue is that the default EGPO airport does not have DME on 110.9. Often FSX does not reflect reality as per current charts and airports need to be updated as required.  EGPO can be easily corrected by modifying the stock airport to create a new AFCAD using ADEX.

[Jon Budworth 0]

Thanks for the reply Gerald,

The real airport has 110.9 as the DME and the flight sim airport also has 110.9 as the DME. (Checked in maps and airport). As I said earlier it does work but for only in a band or 38-28 miles heading to the airport.

Jon.

[downscc 1,327]

I just opened stock FSX EGPO in ADEX and I think I know the problem.  Both localizers, STW and SOY are on 110.9 and both have a DME and this is how the stock airport is configured. The problem is it is not realistic, because there can only be one DME paired with the VHF frequency of 110.9 on the air at a time.  It appears to me that there are two separate DME transceivers because both approach charts indicate DME reads zero at threshold or displaced threshold so my guess is ATC activates whichever DME is in use and the other is turned off.

Here in the US, we have many runways with opposite direction ILS with both LOC on same frequency but there is only on DME and each direction will have a different DME reading at the threshold.  The DME is typically collocated with one of the localizer transmitter sheds.

One solution here is to modify the stock airport as suggested by Gerard but create two AFCADs... one for each direction where the opposite direction DME is missing.  This way you still have the correct DME values at threshold.  Alternatively, create one AFCAD so you don't have to hassel with turning one or the other on or off, but then one approach will have the wrong DME value at threshold.

Interesting problem. With the limitations of FSX there's no elegant solution.

[borgfan 1]

Yes, something is wrong about how this navaids are defined in FSX for this airport. You loose the DME reading as soon as the localiser is picked up, but if your aircraft happens to have something like a Bendix 62A fitted ( as per some A2A models) you can get DME by setting the frequency on the DME receiver itself.  I settled for the compromise of creating a new AFCAD with DME just defined with the localiser. 

[Jon Budworth 0]

Thanks for the help guys, it's very much appreciated. I'll look into it and let you know how I get on.

Jon.