VOR Arrival plate Question

[Pin Head]

I have a arrival plate for XXX airfield. the approach is a VOR RW34.

It is written with no DME information. The minimum height over the VOR is 2000ft. The platform altitiude is 1600ft. There is a notional DME distance of 18 (no reference to what aid this is from) with regard to when this turn must be made by (prevent hitting a mountain I guess).

I take it I can turn beacon inbound and subsequent decent when I am confident of safely intercepting the path, not lower than 1600ft and not beyond 18 miles. So if 1600/3 is say 5.5, would you consider turning in at say 8 miles from when VOR beacon outbound?

[DB6]

Normally if no DME information is given there will be a timing specified, or possibly a cross-cut with another navaid. You talk about 5.5 and 8 miles inbound - there must be timing information or a DME referred to somewhere or there will be no way of determining those distances. If you just state the airfield there will be people who have flown it that can tell you.

[SNS3Guppy]

There may be no timing information or DME for the procedure turn. Commonly 10 miles is specified as the distance within which one must remain from a fix such as the VOR, when executing the procedure turn. The pilot must determine how to remain within that distance...the chart won't provide timing for the procedure turn, nor is DME required.

At 120 knots, one minute outbound is two miles. Figure another minute outbound in the procedure turn, also two miles, one minute to reverse, one mile, that's keeping it within five miles...easy enough to figure, and the chart won't spell it out for you other than giving you the distance within which you must remain.

It is written with no DME information. The minimum height over the VOR is 2000ft. The platform altitiude is 1600ft. There is a notional DME distance of 18 (no reference to what aid this is from) with regard to when this turn must be made by (prevent hitting a mountain I guess).

I take it I can turn beacon inbound and subsequent decent when I am confident of safely intercepting the path, not lower than 1600ft and not beyond 18 miles. So if 1600/3 is say 5.5, would you consider turning in at say 8 miles from when VOR beacon outbound?

If your minimum height crossing the VOR outbound is 2,000', the cross the VOR at that altitude outbound, complete your procedure turn at whatever distance you find comfortable, intercept your course inbound, then descend to 1,600'. Cross the VOR at 1,600', and descend per the profile to either your next step-down altitude, or the MDA, as appropriate to the procedure.

You're under no obligation to go out to 18 miles, if you don't want to. The procedure puts that distance there as the maximum distance available in which to execute your course reversal.

I see your 1600/3 figure is an attempt to get a 3:1 descent ratio, but it's not necessary or relevant here. descend to your minimum altitude appropriate for a given segment of the approach. That's it.

If you're outbound for the procedure turn, the number you gave is 2,000'. You've only got 400' to lose on the inbound leg from the procedure turn, to met your crossing altitude over the VOR, of 1,600'. No need to worry about descent ratios or anything else. You don't need much room to lose 400'.

After crossing the VOR, you aren't looking for a 3:1 descent to the MDA. You can elect to make a stabilized constant descent if you wish, or simply "dive and drive" down to the MDA and proceed inbound at the MDA. If you calcualte your own VDP (or PDP for Pilot Decision Point...a personally chosen, unofficial VDP), then you can pick up your 3 degree glidepath from there.

[No_Speed_Restriction]

how about telling us the arrival airfield so it can be looked up

[Tinstaafl]

Procedures vary, depending on the jurisdiction. In some regions a time outbound will always be specified** if a DME is not included in the approach. In others, such as the USA's FAA controlled regions, IFR procedures require the pilot to stay within a certain distance (10nm in the USA) when they fly the approach but don't mandate a specific time. In this case it's the pilot's job to determine an appropriate timing outbound.



**Generally the specified time is not fixed. It's expected to be adjusted for known or estimated headwind or tailwind effects.

[salamanderpress]

approach construction

I think ICAO specifies a 50 knot adverse wind assumption for airspace clearance criteria when designing an approach. And there must be a final approach fix, derived by timing for each class of aircraft, or else an approach speed must be specified with timing. Specifying a distance (18 miles....!) without information on how to get to that distance seems an odd procedure, especially as the designer seems to have taken care to omit ANY timing information.

The pilot could calculate that based on his ground speed, but so could the procedure designing agency. Is this a Jeppessen approach plate.?

[Herc708]

The NDB is usually a 3degs glideslope, so 3degs is equal to 300ft/nm (1 in Sixty Rule!). Use an approx distance based on a cut from another VOR / DME / FMS to work out an approx TOD distance back from your NDB