California Flying

Escape Passes From the L.A. Basin

May 1, 2000

Los Angeles is surrounded by high mountains. The northern end of a mountain range that geologists refer to as the Peninsular Range runs essentially north and south, paralleling the coastline from the Banning Pass area to the tip of Baja California. The Transverse Range runs east to west and forms the northern wall of the L.A. Basin. These geological walls can wreak havoc with VFR pilots when travel out of the basin is planned, especially when flying north.

The Peninsular Range, an eastern wall

The crest of the Peninsular range forms the eastern wall of the L.A. Basin. Mountain ranges in the Peninsular Range include the San Jacinto Mountains in the north, which start just west of Palm Springs; and moving south, the Santa Rosa Mountains, the Agua Tibia Mountains, the Vallecito Mountains, and the Laguna Mountains. The Peninsular Range is highest in the north, with San Jacinto Peak topping out at 10,804 feet, tapering down to various 4,000-foot peaks near the Mexican border.

The Transverse Range, a northern wall

The Transverse Range, a geological anomaly due to its east/west orientation, forms the northern wall of the L.A.-Long Beach-San Diego basin. This range is formed by the San Bernardino and San Gabriel mountains in the east, and the Santa Monica, Piru, Topatopa, and Santa Ynez mountains to the west. Mt. San Gorgonio in the San Bernardino range is 11,502 feet high while "Old Baldy" (Mt. San Antonio) in the San Gabriel range climbs up to 10,064 feet. Two ranges on the northern side of the Transverse Range, the San Emiglio and Tehachapi ranges, play a part in controlled flight into terrain (CFIT) statistics, since a low spot between these two ranges forms the crest of the Tejon Pass.

The high mountain walls contribute to the summer inversions that trap airborne smoke and fog (smog) in the L.A. Basin. The summertime 2,000- to 3,000- foot marine cloud layer that overlays the basin is also caused by these mountainous walls. Tejon Pass and Cajon Pass, the two main VFR routes out of the basin to the north, are both more than 4,000 feet high.

Tejon Pass

Tejon Pass is at the northern end of the Interstate 5 route between the mountain ranges that form the Transverse Range. The Tejon Pass is also called Gorman Pass; motorists know it as The Grapevine. This pass, cresting at 4,144 feet, is at the northern end of a 43-mile-long pass that gradually climbs from the town of Sylmar, where the highway leaves the basin. A search through the NTSB’s fatal accident database shows that pilots have failed to negotiate this pass from one end to the other. In the past 16 years nearly 50 fliers have ended their flying careers while attempting to transit this pass. The primary cause has almost always been VFR flight up into this pass during periods of low ceilings or mountain obscuration. This practice used to be called scud running—the new name is controlled flight into terrain, or CFIT. Statistics show that nearly 50 percent of lightplane fatalities result from CFIT. As the pass nears its northern end, pilots may be lulled into a sense of complacency by the fact that they’re almost over the top. Nothing is further from the truth, since there’s one more hazard just beyond the summit. As soon as the summit is passed, the highway makes a 90-degree right turn and then two miles later makes a sharp left turn. A longtime Southern California NTSB accident investigator has a nickname for the ridge that awaits anyone who fails to make the first sharp right turn. He calls it Wichita Flak Ridge because of all the lightplanes that have crashed into the ridge. It’s not an easy pass to successfully scud run.

Cajon Pass

Cajon Pass climbs over the Transverse Range between the San Bernardino and San Gabriel mountain ranges approximately 65 miles east of the Tejon Pass route. Interstates 15 and 215 meet at the town of Devore on the southern end of the pass and climb to the summit. This pass, unlike the Tejon Pass, climbs fast. Devore, at 2,022 feet, and the summit, at 4,190 feet, are only 13 miles apart. While this pass isn’t statistically as dangerous as Tejon Pass, it has the distinction of at least one fatal crash over the past three years.

Banning Pass

The official name of this pass is San Gorgonio Pass. It gets its popular name from the town of Banning, which has an airport. This pass forms a narrow passage between the eastern end of the Transverse Range and the northern end of the Peninsular Range. Since both ranges are at their highest points in this vicinity, this low (2,600 feet) pass is where the cool moisture-laden air that has blown into the L.A. Basin off the Pacific Ocean exits the basin on its way to the eastern California deserts. The result? High winds and turbulence around the mountains. Occasional dust storms can reduce visibility. Flying westbound through the pass often results in low groundspeeds, which play havoc with flight planning and add to get-home-itis. The winds and geography of this pass cause conditions that can force basin-bound pilots into making a flight-planning decision: Should the pass be transited at 6,000 to 8,000 feet in an attempt to avoid the turbulence associated with the venturi-like pass conditions, or should the pass be transited low, knowing a rough ride will result? This seems like an easy decision until the semipermanent broken-to-overcast cloud layer that overlays the basin is taken into account. Go low, and avoid being caught on top, or go high for a smoother ride, hoping there will be a hole in the cloud layer. Again, this pass is not statistically as greedy as Tejon Pass but does present VFR pilots with some difficult decisions.

How to avoid becoming an NTSB statistic

The best move any VFR pilot can make to improve his chances against the passes is to get an instrument rating. This will eliminate go/no-go decisions related to the semipermanent broken and overcast layer and will open up a multitude of safe options for escaping the basin to the north.

Instrument rating or not, always obtain a current weather briefing before departure. Be particularly wary when the winds aloft are forecast to be more than 20 knots and when the briefer mentions "mountain or mountaintop obscuration." This phrase is briefer-speak for saying that atmospheric conditions are conducive for the formation of clouds in the passes. Ask the briefer for any pilot reports of pass conditions or turbulence over the mountains. Pilot reports will help pilots make an informed decision based upon reported rather than forecast conditions. The key to pilot reports is that they have to be recent, say within the past hour, to have real decision-making value. Get as much information as you can from experienced local pilots regarding their flights into the passes.

Call the Los Angeles Area Safety Program managers at 310/215-2150 for a schedule of local safety seminars. The schedule for these seminars is also listed on the World Wide Web ( www.awp.faa.gov/flightstandards/). There’s a seminar every week somewhere in the basin. You’re sure to run into active local pilots who have experience with flying the passes.

Sandberg ASOS

The Sandberg Automated Weather Observation System (AWOS) is eight miles southeast of the Gorman VOR (GMN), which is located near the summit of Tejon Pass. The continuous AWOS report can be monitored in flight on 120.65 MHz or on the ground by phone at 661/248-2329. The Gorman-area geography, with cool, moist ocean air on the south side and hot, dry Central Valley air on the north side, makes it a breeding ground for thunderstorms, especially during late summer afternoons. While these thunderstorms don’t usually pack the punch of a typical Midwestern thunderstorm, they still pack enough of a punch that giving them a wide berth is the best strategy.

After you’ve gathered all the information you can and if the winds aloft are below your personal minimums, it’s prudent to go take a look and see if the pass is open. If you can’t climb to an altitude of at least 1,000 feet above the pass elevation and maintain VFR cloud separation minima, or you can’t see through the pass to good weather on the other side, it’s folly to think the clouds are going to magically lift as you fly up the pass. Wait for another day.

Plan your flights through passes early in the day or in the late afternoon. Unless the winds aloft are scooting along, there will be less wind through the passes during the cooler times of the day. If you safely transit the pass, make a pilot report (pirep), reporting the conditions you observed to flight watch on 122.0 MHz so other fliers can take your experience into account during their decision making.

Careful planning, learning as much as you can about the geography and weather patterns in the L.A. Basin and the surrounding mountains, and sharing ideas with more experienced pilots will go a long way toward ensuring safety while flying the Southern California mountain passes.


E-mail the author at steve.ells@aopa.org.