Lower Mins with Synthetic Vision?

You can find all sort of interesting things on approach plates.  Take the ILS 17L into Colorado Springs (KCOS).  The approach is a standard Category I ILS, yet the minimums block contains some non-standard minimums:

What’s that “RA 169” all about?

RA in this case stands for radar altimeter; the decision to go-around or land is made referenced to height above ground, not a baro-altimeter setting.  Most modern light jets equipped with radar altimeters have a means of selecting “Baro” or “Radar” minimums to be entered into the PFD, triggering the “minimums” alert.  Looking at notes 1 and 2, though, it’s apparent that not everyone can use a radar altitiude of 169’ as DH.  The big limit is the note that use of a heads-up display, or HUD, is required.  Even aircraft equipped with a HUD aren’t automatically able to drop an extra 50’; the flight crew and aircraft must have been granted authority via an LOA, as well.

The requirements to be granted the LOA are spelled out by the FAA in order 8400.13D, which specifies the crew and aircraft must be certified for Category II operations.  Additionally, single pilot operations are specifically prohibited from using the lower minimums.

So while it’s apparent the average owner –flown light jet won’t be able to fly Cat I ILSs to 150’ minimums anytime soon, what is of interest is the trend approaches like this represent.  “Special Authorization (SA)” procedures are becoming more common, with required navigation performance (RNP) approaches, being the main example.  Rather than a one-size fits all mentality to airspace management, the FAA is shifting to a “best equipped, best served” philosophy.  Operators with the requisite toys will be authorized to fly approaches others can’t, or to fly a standard approach to lower minimums.

And while it will likely be some time before light jets are delivered with HUD units, the next SA ILS authorization being studied will utilize a technology already available- synthetic vision (SV).  As envisioned, aircraft with a radar altimeter, WAAS, and SV will also be able to take advantage of 150’ DHs.  Pilot and aircraft certification will still be required, and it’s not certain if single pilot operations will be permitted.

Nice to be SOL

WAAS is unquestionably a revolutionary technology for the IFR pilot.  With no ground infrastructure at all, we can now be guided as low as an ILS to any piece of pavement at any airport.  Even airports without a WAAS approach benefit as the vertical accuracy of WAAS allows for an advisory glidepath to MDA on plain-vanilla GPS approaches.

Well, to airports in North America, anyhow.  The biggest limit of WAAS is that as it depends on geo-stationary satellites, the coverage area is limited to the parts of the planet over which those satellites “hover”.  Travel outside these areas and GPS technology steps back to the pre-WAAS era.

That’s why the recent declaration of the EGNOS systems as safety of life (SOL) capable is great news.  EGNOS, or European Geostationary Navigation Overlay Service, is the European version of WAAS, both of which are generically called Space Based Augmentation Systems (SBAS).

EGNOS covers most of Europe

EGNOS has been operational for several years, and in March was declared ready for critical SOL operations, such as aviation.  Within a week a Falcon 900 flew the first LPV approach in Europe, to Pau Pyrénées in the south of France.

Garmin has already upgraded the G1000 to be capable of using EGNOS guidance.  When the navigation database cycle 1101 was installed in G1000 systems in early January, it also unlocked EGNOS capability.  Pressing the SBAS soft key on the GPS status page now shows EGNOS in addition to WAAS and MSAS (the Japanese version).

G1000 is now EGNOS ready

Unfortunately it will be some time before full benefit of EGNOS is realized.  To start, not very many airports in Europe have approaches with LNAV/ VNAV or LPV minimums, with only France and Germany having any in large numbers.   Further, even those that do may prohibit use of EGNOS until flight checking is complete.  A recent trip into Hamburg, Germany (EDDH) turned up the following NOTAM:

“Use of SBAS- (EGNOS-) signals for APV- Baro VNAV operations prohibited until further notice.  Use of LNAV/ VNAV minima with a certified Baro VNAV system…still permitted.”

So while LNAV/ VNAV minimums are published to EDDH, they can’t be flown yet via EGNOS.  This will change with time, and European operators will enjoy the benefits of SBAS approach aiding we’ve enjoyed in the US for several years.