On 10/24/2010 5:30 AM, VOR-DME wrote:
One airport I frequently use in the northeast has adopted an improvement plan
which includes, along with a slight runway extension, the installation of a
Transponder Landing System. The airport is currently served by a VOR approach
and a GPS approach, but terrain considerations would almost certainly
preclude commissioning of an ILS there.

I am instrument rated, and I had never heard of a TLS approach. It is not
even mentioned in any of my textbooks, going back over the past 20 years. It
is not mentioned in the FAA Instrument Flying Handbook. In my instrument
training we had to be at least basically familiar with types of approaches we
never expect to encounter, like MLS, and describe principles of GCA’s,
ILS-PRM and SDF’s, and of course we had to fly every type of real-world
approach, from NDB up to LPV’s but never have I heard of a TLS.

I do find internet references to the TLS, developed by ANPC Corporation, of
Hood River, OR. Most of these references date from the early 2000’s, but some
are more recent. A Wikipedia article from 2005 treats it as a standard type
of approach, just as if they were talking about an ILS. The same article
however states that WAAS and LAAS have failed to garner widespread
acceptance.

So my question - does this type of approach really exist, other than on
Wikipedia? Can someone point me to an approach plate that says "TLS" on the
top? What would lead a purportedly expert consultant to recommend this type
of approach for installation in a New England airport today?


Interesting approach. Another DARPA program that may be hitting paydirt.
On the downside: it drives ILS indicators or if you will, an ADI.
So it pushes VHF and UHF loc and glideslope signals - but not in a
straightline, necessarily, and in mountainous regions where you couldn't
produce a straight ILS beam if you tried - but TLS can.

I can see why MLS development ground to an instant halt after about 12
installations - GPS and now TLS can do the job better and cheaper.
Though I haven't personally got a glideslope indicator - even I can see
the Sporty ads for a handheld LOC/GS display - and that's not out of reach.

I like the idea of an array listening to your transponder responses and
computing 3-D locations of one aircraft at a time, on the fly, to drive
your LOC/GS display appropriately.

The most fundamental argument against, is that its ground-based - and
that's something the licensing authorities are backing away from, any
more. The maintenance cost must be a factor there.

Still, this device is comparatively cheap compared with ILS and MLS
certainly, so it's worth a shot. I bet there are very, very few
airfields with this device available - UPS and/or FedEx are prime
candidates for pioneering it into backcountry strips no doubt.

Thanks for sharing

Brian W