I recently purchased an airplane that had been based in Europe. It had a panel-mounted GPS that contained, naturally, a European database.
Living in the Caribbean, I needed – and ordered – a Western Hemisphere database. While awaiting delivery, some friends and I planned a trip of approximately 350 nm across the open ocean from the U.S. Virgin Islands to the island of St. Lucia.
Before departure, I got the lat/long coordinates for our destination airport from my Jeppesen airway manual and programmed the destination into the GPS manually as a user waypoint.
The second half of our flight was a bit hazy and conditions approached marginal VFR as we got closer to our destination. Although I had VOR and ADF on board, I relied virtually exclusively on the GPS. When we reached St. Lucia according to the GPS, the island simply was not there.
I fought hard to keep the confusion, panic and denial from overwhelming me. I called St. Lucia ATC and told them I could not see the island although my GPS reported it was right in front of me at less than 5 miles. (The airport was reporting visibility greater than 6 miles.) The controller told me my GPS was wrong and that I was lost. He advised me to climb to 4,200 and call radar control at the neighboring French island of Martinique.
I did that, and with a little help from some vectors, found St. Lucia about 30 minutes later. At one point I asked Martinique how far I was from St. Lucia, and when they told me 43 miles I thought – and might have said – thats impossible.
For weeks, I couldnt figure out what I had done wrong. Finally, as I went back over the Jeppesen plate for about the third time, I discovered it contained a typo. It reported the longitude for our destination airport at W061 59.6 instead of W060 59.6. The simple typographical error of substituting a 1 for a 0 translated into an error of 60 nautical miles when I programmed it into the GPS.
On the same page as this error, there were other positional indicators that would have made the error obvious if I had been more observant. I should have cross-checked the information before I relied on it for an over-water flight.
I should also have cross-checked my navigational instruments and worked out the discrepancies inflight. The trip to St. Lucia taught me a good lesson: Blind reliance on the GPS or on any other resource – electronic, print or human – without cross-checking is usually not a good idea.
Other lessons to consider: This is a good argument in favor of databases the user can download from the internet and load personally. Frankly, were irritated at units that discourage updates by making them difficult or time-consuming to do.
In addition, we think its a good idea to file IFR for such featureless flights. Radar may have alerted you to the deviation earlier.
The O-320 in our 172N is the sweetest running aircraft engine I have ever known. We maintain it rigorously and proactively and lean aggressively for all ground operations. I have not had to clear a mag once in the 880 hours since it was installed.
I flew the airplane the day before yesterday, 15 hours out of annual with new plugs installed. I remember being impressed again with how smooth it was. Two of our more experienced pilots flew it after me and the last confirmed that it was smooth when shut down.
The next morning, I started it up and taxied to the run up area. When I did the mag check, the left was rough. The right was so rough that the airframe was shaking visibly. There was no question about flying the airplane.
When the plugs were removed, all were found fouled and one was completely bridged. The engine ran acceptably on runup after cleaning the plugs but was not as smooth as before. It gradually returned to normal on a four-hour flight.
Were still trying to figure out what happened.
The lesson here is that fouling isnt always something that gradually gets worse. It can build up quietly and then show itself suddenly when the spark goes through the crud instead of the mixture. This could have happened on a lunchtime stopover, running perfectly at shutdown and then sick after start up and a five-minute taxi.
A rough, weak engine might get you down safely if it goes bad in flight, but it may put you in the trees on a tight takeoff.
Dont skip that runup just because it was running fine 15 minutes ago.
Other lessons to consider: Your mechanic probably checked the usual mechanical suspects, such as the wrong temperature range spark plugs, but were inclined to think a combination of mechanical and human errors occurred.Improper leaning is a prime suspect, particularly if the more experienced pilots leave the red knob pushed all the way in from engine start to 5,000 feet, as some do.
Brains Over Brawn
We live near Durango, Colo., on the west side of the Rocky Mountains. The peaks here range from 11,000 feet to 14,000 feet.
Many of our trips take us east across two of these mountain ranges. We fly a turbo Arrow, so we usually cross them at 16,500 to 17,500 feet. Often, with little surface wind reported, we find ourselves going down 1,000 fpm with the mountains getting bigger in the windscreen while the engine is at climb power.
In those circumstances, the only recourse is the trusty 180-degree turn. Then we fly parallel to the mountains and probe for a soft spot where the downdrafts are manageable. Sometimes we end up as far south as Santa Fe, which is 100 miles.
In light planes, you cant outfight these big winds – even when there arent reports of big winds. You have to outsmart them and make the end run.
Other lessons to consider: Were sure you understand the importance of fuel reserve for just such situations, but well state it clearly just for those who may not make the connection.
If you cant tanker enough fuel to give yourself the option, land and reassess your plan. The record is littered with pilots who hit the ground a hundred feet below the terrain they were trying to fly over.