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## DME arrival question

• pauldeegan
• Topic Author

### pauldeegan created the topic: DME arrival question

Hi everyone,

Just want to clear up a question in the book

Q - You are carrying out a DME arrival procedure into PARKES, NSW from overhead Bathurst NDB. Select the statement wich is correct regarding descent on this track-

a) You must reach a altitude of 3000ft by 9 DME PARKES
b) You must not descend below 3500 ft before 7 DME PARKES
c) You cannot descend below route LSALT of 6100 ft until within 25nm of PARKES
d) You must not be above 4000ft at 9 DME PARKES

My question is shouldn't c) also be a correct answer?

Also another question about the 25nm disc of MSA. If all you have is a ADF and are coming into an aerodrome to do a NDB instrument approach... How do you know exactly when you are within 25nm to make a descent below LSALT to MSA? Is it ok to use DR navigation to calculate your distance from the aid? or do you have to fly overhead the aid at LSALT and loose height in the holding pattern.

cheers,

Paul

• Posts: 2468

### bobtait replied the topic: Re: DME arrival question

Providing you are established on the 272 inbound track from Bathurst, You can descend to 3900 feet at 27 nm. so (c) is not correct.

The AIP says that once you are 'established' within 25 nm you can descend to MSA. It does leave it a bit open to interpretation as to what established means. Most IFR pilots would agree that on a shortish leg, say 50 or 60 nm, a DR for 25 nm would be quite safe - expecially if you built a margin into it. Remember also that an IFR flight is not always in IMC, so it's quite possible that, on occasions, you could get a visual fix that establishes you within 25 nm.

Also remember that if you have GPS there is nothing to stop you using GPS to determine the 25 nm MSA area. Even if you are not endorsed on RNAV/GPS or DME/GPS Arrivals you can still use GPS at or above LSALT providing you have a log book certificate of competency for en-route.

• pauldeegan
• Topic Author

Thanks Bob,