Thursday, February 12, 2009

Helicopter GPS approaches to hospitals

When a company, hospital, etc. wants to create an approach using GPS technology, they hire a contractor (STI comes to mind). The contractor "terps" the procedure by evaluating the terrain and obstacles and coming up with a slight variation on a cookie-cutter approach. The FAA does not flight-check these approaches as they do the ones at your local airport, with their aircraft and folks. I am referring to approaches to hospital helipads, often "point-in-space" approaches with a short VFR transition to the landing area. They terminate the approach at a PIS vice the helipad to get a lower MDA and a higher probability of breaking out.

Since towers spring up almost overnight, and buildings get built too, there is a need to periodically verify that the altitudes published in the procedure continue to offer safe obstacle clearance. For this to occur, the owner of the approach (or some other interested party) must provide an aircraft to fly an FAA rep. over each of the approach paths/segments. I got tasked to do this in Ohio a few years ago with Mr. Tom Bruchs (I hope I spelled that correctly as he is a heck of a guy). It was a good experience - if you get the chance, do it.

Per Mr. Bruchs, you don't need an IFR capable aircraft, or even an IFR certified GPS - but you do need a GPS that works. Having all the waypoints in a database does make things go faster.
You don't actually fly the approach as published - instead you fly slow at lower altitudes along the legs and note all obstacles (they are easier to spot from low altitude).

So, as you are motoring along, you spot a tower. You hover right up next to it, you listen to the nearest available ASOS or AWOS for a current altimeter setting, you verify the location from your GPS, you note the altitude with your aircraft hovering immediately next to top of the obstruction, and the FAA rep writes all this down on his data sheets.

They take the derived altitude of the obstacle, add (I think) 50 feet for altimeter error, add the appropriate altitude "cushion" for whatever leg of the approach you are on (the cushion gets thinner the closer you are to the FAF) and come up with the appropriate altitudes to publish for the approach. If nothing has changed, the approach as published is approved for use for another time period (1 year?). If there is a new obstacle, then a new text/graphic procedure must be printed.

If the approach you want to use has not been checked within the required time period, you are not authorized to fly the approach.

Now, if you are still with me, you will remember that I mentioned that obstacles spring up almost overnight, and flight checks occur but once a year. A prudent person with these approaches in his or her operating area might want to do a "self-check" in VFR conditions on a more frequent basis - say quarterly or semi-annually. After all, as I am sure you know, just because something is legal doesn't mean it's safe or smart.

safe flights,