Posts: 14
Joined: Fri Jul 19, 2002 5:51 pm

DME/slant Range Errors

Sat Jul 20, 2002 3:33 am

How do commercial airline pilots compensate for the slant range error?Is there a proceedural method?Lets assume that the automated flight systems are not a factor,for aircraft navigation in this case!

RE: DME/slant Range Errors

Sat Jul 20, 2002 4:16 am

The simple answer is that they don't bother to compensate for it. Back in the days when "course line computers" were used to shoot RNAV approaches, slant range compensation was built into some of the boxes, but now days with the common usage of FMS's, GPS's, etc. it's not a consideration.

RE: DME/slant Range Errors

Sat Jul 20, 2002 4:17 am

Slant range errors for DME only appears much on short distances, such as 10 or 20 nautical miles, so in enroute navigation, DME distance is generally not compensated... but see the final note...
For approaches, such as VOR-DME approach, you fly the procedure as published with the number and DME distances published... approaches are designed (and later printed) accounting for such errors...
DME slant range errors were compensated yes, as in example in the 747 I fly, our three INS were updated by DME in the past... we entered the "elevation" of the DME station in our PMS/FMS... example, station such and such is at 2,700 feet AGL... nowadays our INS are updated by GPS, so the DME is no longer used for INS update...
(s) Skipper

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