June 2005-
Take a good look at the clouds in the picture on the facing page. Notice the sharp edges, and how they look stacked up, almost like pancakes? Trust me, you don’t want to see them any closer than this.
Those are standing-wave lenticulars, and we saw them a few weeks ago, just north of Mojave Calif. There were even bigger stacks to the south.
Lenticular clouds are one sign of severe turbulence. They develop downstream of mountain ridgelines when there’s a strong wind and enough moisture to form a cloud. It’s probably just as well there was enough moisture because it showed us some of the places to avoid.
We ran into them on the way home from a trip to Mexico with Liga International (www.ligainternational.org), a volunteer group that runs clinics in several small towns in Northwest Mexico. I’ve been flying with them since about 1997, and every trip has been an adventure.
This trip started early on a Friday morning, departing about an hour late due to some confusion at the airport. That’s a problem because these trips cover about 1,100 nm each way, and with stops for fuel and paperwork, we frequently find ourselves running out of daylight.
The airport we fly into, El Fuerte, is not lighted and has a large radio tower nearby so late arrivals aren’t really an option. Sure enough, in addition to the late departure, we leveled off to find a 15-knot headwind. That’s happened before, and it usually results in an unscheduled fuel stop and more wasted time.
Before this trip, though, I’d been intrigued by something I’d seen on Austin Meyer’s website (www.x-plane.com). Austin had a demo up for a little program he’s written to determine optimum altitude for flying into headwinds, and among other things, he claims you’re better off to throttle back and reduce fuel burn into winds as high as 70 knots.
The fine print on this is that his example involves an airplane with GAMIjectors that can be operated lean-of-peak (LOP). Well, I have GAMIjectors in N16460, so before making an early fuel stop, I decided to try Austin’s trick and see if it might work.
Unfortunately, I found out that my engine won’t run smoothly LOP. It used to, but last year I replaced two cylinders and I hadn’t been running LOP during the break-in period. Apparently the injectors need to be adjusted.
It would run smoothly at peak, which is how “best economy” is defined in the Lycoming operator’s manual at 65 percent power or less. I set it up for that, and got a nine gph fuel burn. N16460 has 50 gallon fuel tanks, 48 usable, so that combination gave me about five hours endurance—and sure enough, that was not only enough to make Imperial (our planned fuel stop), it did it with over an hour to spare!
From Imperial on into Mexico was pretty routine—the headwinds eased off south of the border. We were the last plane into Ciudad Obregon, our fuel-and-paperwork stop; which meant that we didn’t have to waste time waiting for them to clear other airplanes. And we made it to El Fuerte with about 30 minutes to spare before dusk.
Two days later, it came time to leave. A bunch of us were having breakfast at one of the local hotels when the local police arrived, asking for the pilot of one airplane in our group. This is not good news, and we were all looking at each other and holding our breath when the pilot of the airplane in question identified himself. “Señor, one of your tires is flat,” they said.
I for one stopped holding my breath—I could imagine all kinds of more serious problems—but then I started wondering. What do you do if you come out to the field to find a flat tire at an airport in rural Mexico?
For that matter, what would you do in the same situation at an unattended Unicom field here in the States? I wasn’t in a rush (one of my passengers hadn’t even put in an appearance yet) so I finished breakfast before wandering out to the airport… and a funny thing happened: another pilot joined us for breakfast who turned out to have empty seats.
He had quite a few seats, actually, since he’d flown a Piper Malibu down solo. “Why?” I asked.
“Well, I was a little out of practice…” .
We moved the passengers out of the Bonanza with the flat tire and he flew them back north of the border while the pilot waited for a local mechanic who evidently had experience with this sort of problem.
I’m told that he jacked up the wing, removed the wheel, verified that the tube wouldn’t hold air (the same local cops who came looking for the pilot had already provided a bicycle pump, which was good for a laugh but didn’t really help), patched it, and had him on his way only about 30 minutes behind us.
Another minor hazard of flying in Mexico turned up on the radio when we called in after departure—Obregon had run out of Avgas. That’s happened several times over the last few months.
Fortunately, Guymas had a good supply, and is only about 30 minutes flying time further northwest. It’s also one of the prettiest airports I’ve ever flown into—the approach to Runway 02 involves overflying the town, which is right on the water at the base of several hills, and flying around the largest hill on base to set you up for short final. This gives the passengers some nice sights to see, which keeps them occupied.
We gassed up, did our paperwork, and actually had light tailwinds as we flew north to Calexico, our U.S. airport of entry. After passing U.S. customs, Kate took our passengers next door to Rosie’s Plane Food for hamburgers while I got N16460 fueled, closed our border-crossing flight plan and got a weather briefing for the flight home.
A moderate westerly flow was forecast, and in the vicinity of the mountains we have to cross, that inevitably creates some turbulence. Sure enough, there was an Airmet for occasional moderate turbulence below 12,000 feet from Palm Springs northward.
I filed an IFR flight plan (I didn’t really expect to need it, but at the end of a very long day I appreciate having someone on the ground double-checking to make sure I don’t do anything too dumb) and joined them for lunch. While we were eating, the wind must have increased.
By the time we got to Palm Springs, a Sigmet had been declared for severe turbulence below 12,000 feet. Palm Springs approach instructed me to climb to 11,000 feet on the leg between Thermal and Palm Springs and I could not do it. With full power set and best rate of climb airspeed, we were going down at about 600 fpm.
I finally cancelled IFR (but stayed with Palm Springs for flight following), turned off toward lower terrain, and worked my way into the desert VFR. Then I turned west and started a long, slow, climb into the mountain waves. It took about 20 minutes or so to reach 12,500 feet. At that altitude—above the mountains—we could still feel the wave, but it was pretty gentle—50 or 100 fpm.
Unfortunately, ground speed was now down to 67 knots, and not even Austin’s suggestions would be much help stretching the range. The Air Force, however, did help: I guessed that Edwards AFB probably wouldn’t be too busy on a day like that, and sure enough was cleared through their restricted area on a direct line to Shafter VOR. That shifted the wind from a direct to a quartering headwind, and groundspeed rose to a blistering 82 knots.
An hour or so later, as we crossed the foothills of the Sierra Nevadas (and put those strange-looking Lenticular clouds behind us), I lowered nose down and pointed us toward Visalia, where we stopped for fuel. On the way down, we could see lightning flashes in a big thunderhead north of Mojave, and I was glad to be well away from it—mountain wave and convective turbulence is a little too much adventure for my blood!
We weren’t quite finished with turbulence yet. The whole trip back had been marked by a series of minor electrical problems. I was getting a whine in my headphones, and the engine monitor reset itself whenever I turned the fuel pump on. On the way into Modesto, when I put the landing gear down all the panel lights dimmed and the ammeter went to zero.
On a hunch, I switched the alternator off and back on again. All the lights came back up. I said a few unpleasant words about alternators (we just installed a new one last year) and kept working on my approach.
A front had moved into Northern California and we were just catching the edge of it, so after finally flying out of those awful headwinds I was now facing low ceilings, continuous chop, and finally rain. I called Norcal Approach for an instrument clearance.
Thinking back on it now, we must have flown through the gust front from a storm that arrived at the same time we did. The worst turbulence of the whole trip was on short final into Modesto. I had just made what I thought would be my last throttle adjustment to settle on the glide path when the airplane decided to go up at about 1,500 fpm, and of course shortly after that it went down almost as fast.
I shoved in the throttle to compensate and the right wing dipped. I got that lifted and had to work the rudder pedals all the way down to the ground. The landing wasn’t a greaser, but it was okay and I got the airplane stopped in time for the first turnoff.
I got pats on the back from Kate and both passengers. We were all glad to be back on the ground!
PS: I had my mechanic check out the electrical system after we got back. He found a loose ground strap on the battery. Tightening it eliminated all the electrical problems.
John D. Ruley is an instrument-rated private pilot, and a freelance writer specializing in aviation and technology. He’s also a volunteer pilot for Liga International. You can write to John at jruley@ainet.com.
