“Warning! GPS Navigation Lost!” proclaimed my GPS receiver.
Jean and I were bouncing through clouds on instruments at 12,000 feet, over trackless mountains along the remote Arizona-New Mexico border.
Seconds after that initial warning, my primary flight display announced, “GPS reversion mode: for Emergency Use Only!” (but displayed no position.) My multifunction display restarted itself with a “Maintenance Required!” alert. Next came an “ADS-B (out) inoperative!” warning, meaning our transponder had stopped transmitting our GPS coordinates to air traffic control (ATC).
I was flying Jean from Flagstaff to El Paso for tennis sectionals. Normally we make the 2½-hour journey straight-line VFR. Today, however, layered clouds shrouded the mountainous central portion of the route, so I’d filed under instrument flight rules (IFR). This route spans a huge swath of military airspace that when active cannot be crossed IFR, so I’d filed a circuitous route over Socorro, New Mexico.
My first hint of trouble was when our controller asked, “Are you ADS-B equipped?”
That seemed odd, as he had long been tracking us. He then cleared me to an intersection to bypass nearby White Sands Missile Range restricted airspace, but the GPS died as I entered the fix into my navigator. After I reported the failure, the controller assigned radar vectors around the restricted areas.
Now other pilots began reporting lost GPS, and I noted that the position symbol on my tablet computer had stopped moving…
This new Fourth Edition features many new illustrations and updates, many in full color, and now covers all required ATP-CTP material.
Along with numerous systems and terminology enhancements we’ve updated and expanded coverage of multi-pilot-crew coordination, one of the toughest challenges faced by new turbine pilots, and added an all-new crew briefings section.
Our friends Steve and Molly recently invited us for a hiking weekend in southwest Colorado.
This would be our first summertime visit to 9,070-foot-elevation Telluride Regional Airport (KTEX). Telluride is surrounded on three sides by 12-14,000-foot mountains, but we could approach from the west at 11,000 feet.
Like most Telluride traffic I planned to land on Runway 9 and depart Runway 27 to avoid maneuvering in the dead-end canyon east of the airport. That required good visual flight conditions, and light winds to preclude downwind takeoffs or landings and dangerous downdrafts tumbling over the surrounding mountains.
Given suitable weather, my main concern flying our non-turbocharged Cessna 182 was safely departing such a high-elevation airport in summertime.
Temperatures of 48°F to 75°F sound pleasantly cool, but at 10-12,000 feet density altitude we’d be lucky to get 65% of sea-level power at full throttle, and 300 fpm climb…
We recently landed at Telluride Airport, Colorado (KTEX), elevation 9,100 feet. The above photo was taken at 11,000 feet inbound to land. (Note how low we are over the ridge at right, at that altitude.) The town of Telluride is barely visible deep in the valley beyond the airport. Airport density altitude was almost 12,000 feet when we landed.
Several pilot friends expressed interest in my planning process flying into such an airport, so I thought I’d share the details in a post.
First, check out the map. Telluride Airport is surrounded on three sides by 13-14000’ mountains. However it is relatively open to the west. By navigating to the Cones VOR and then turning east, it is accessible under the right conditions.
Density Altitude and Aircraft Performance
When I say accessible, my underlying concern flying a non-turbocharged airplane was not so much whether I could safely approach and land, but whether I could safely depart the 9085-foot-elevation airport in summertime temperatures. So the crux is “density altitude” (D.A.) and that’s where I’ll start.
Even before checking anything else, I knew I’d be lucky to get 65-70% of sea-level power at full throttle, and 200-300 fpm climb after takeoff from such a high elevation. So my first questions were “In the worst case could I take off in some direction without the need to climb? Better yet, could I safely descend after takeoff if I found myself unable to climb?” If I needed to climb to clear significant terrain after takeoff, I wasn’t going there.
So that crazy dropoff from the Telluride Airport westbound into the San Miguel River Valley is actually a big plus. If I could just get off the ground before the end of the runway, I’d be okay proceeding westbound even with little or no climb. I dared not take off to the east due to high terrain and little room to turn around. But visiting here was within the realm of possibility as long as I departed to the west.
Next I checked forecast temperatures for our visit. Telluride expected highs in the mid-70s and lows in the upper 40s. Those sound nice and cool until you consult density altitude charts. At 73F the density altitude would be 11,500 feet. If I departed early morning when the temperature was around 50F, D.A. would still be 10,200 feet. Wow!
Then I consulted the performance charts in my airplane’s pilot operating handbook (POH)—how much takeoff roll would I need, and did I need to clear any obstacles? I’m no test pilot and my engine is old so I all but doubled the chart values in my calcs. Even with a 1500-foot takeoff roll and some 3,000 feet to clear obstacles, the 7,000-foot runway should provide adequate takeoff margins.
Next I consulted my POH climb-performance charts. At these density altitudes my calculated climb rate was a thought-provoking 12-14 miles to clear a 1000 foot ridge in our normally peppy Skylane. (Before our first visit here several years ago, I actually climbed the airplane to 11,000 feet to confirm my climb rate under appropriate temps.) Clearly I didn’t dare climb eastward toward the mountains after takeoff, but the good news was that departing west I needn’t climb at all to clear terrain, and could in fact safely descend into the San Miguel River Canyon if necessary.
Two things I can do to shorten my takeoff roll and optimize my climb rate are:
Take off when it’s coolest early in the morning, and
Load the airplane as light as possible. For the latter we took minimal luggage and removed unnecessary supplies from the airplane. I also planned fuel for the 2-hour flight before taking off from Flagstaff. Although our Skylane holds 88 gallons, 45-50 would give me adequate reserve. So we took off from Flag with 75 gallons, with the target of having 45-50 departing Telluride. That put us ~475 pounds under max gross weight, not a precisely calculated target but simply based on “the lighter, the better.” If we’d had heavier people or bags I’d have departed Telluride with even less fuel and landed at nearby Cortez (which is much lower) to fuel for the flight home.
Now come weather factors. It goes without saying that I want excellent visual flight conditions before flying up a dead-end canyon. (Initial altitude for an instrument approach here is 13,000 feet, and for an airplane like ours you’d need to miss the approach some 6 miles from the runway where there’s still room to turn around. And yes, consulting approach plates is accordingly part of my planning.)
The remaining factors boil down to wind. I did not want to take off eastward over town into the dead-end canyon, nor battle downdrafts given such limited aircraft performance. Wind flows over mountains like water over rocks in a brook, so I dared not accept significant winds from north, east, or south due to potentially severe turbulence and downdrafts tumbling over the high surrounding mountains. Anything stronger than light westerly winds would also generate turbulence and force me to land downwind. There’s hardly room to circle-to-land nor on climbout, so I decided I wouldn’t accept any wind beyond a few knots from the west.
This is a relatively busy non-towered airport in a narrow canyon with effectively a one-way runway (land east, depart west). Many visitors arrive in jets. If there’s much traffic when we arrive or depart it’s best to to avoid conflicts by lingering outside the canyon or on the ground until things quiet down.
Consult with Local Pilots
Based on this assessment the flight sounded quite doable. I always phone ahead to unfamiliar mountain airports for guidance from a local pilot. So to reinforce my conclusions I phoned Telluride Airport to ask whether many light aircraft come in at this time of year and they said yes. But those answering were not pilots so I phoned area flight schools hoping a local pilot with Telluride experience could give me a summertime operations report. Finally I reached someone at Cortez Airport who said they do see quite a few light aircraft coming or going from Telluride. In a telling example he told of a Comanche pilot who came in the day before and checked extra luggage with him for the weekend to lighten the airplane before flying in and out of Telluride. (That pilot sounds like a wise one!)
Noise Abatement Procedures
Even then I was a little nervous, but logic and homework said we’d be safe. My final planning step was investigating and refamiliarizing myself with Telluride Airport’s noise-abatement procedures. (Check for these on any given airport’s web page, as they’re not always available through normal flight-planning channels.) By following noise abatement procedures we help keep our favorite airports open.
It’s all about Airspeed
Okay, now let’s talk about the actual flying, much of which boils down to speed. As you know, we fly all our pattern work and approaches at “indicated airspeed” read off the airspeed indicator. That remains true whether you’re operating at sea-level Nantucket or Telluride.
ALWAYS FLY THE SAME INDICATED AIRSPEEDS FOR AIRPORT OPERATIONS REGARDLESS OF ELEVATION. If you approach sea-level Nantucket at 60 knots indicated, you should also approach Telluride at 60 knots indicated.
That being said, it’s true airspeed, not indicated airspeed that in no-wind situations defines our speed over the ground. This of course is why when cruising at altitude your airspeed indicator might show 100 knots when your true airspeed and hence groundspeed might be say 130. True airspeed increases by about 2% per thousand feet, so at Telluride you’re truing about 20% faster than at sea level. Why does that matter?
The plane feels like it’s going much faster than you’re used to on final approach at sea level, so pilots sometimes make the dangerous mistake of slowing below normal approach speed because “this doesn’t feel right.” Obviously you’re going to touch down faster, too.
You may have wondered why landing distances increase with altitude like takeoff distances do. The reason is because you’re going faster over the ground at the same indicated airspeed so consult your performance charts for adequate runway length.
Since you’re flying faster, the airplane’s turning radius increases, just as it does when driving faster in a car. You may be familiar with accidents where airplanes flew up a blind canyon and lacked room to turn around. Larger turning radius at the same indicated airspeed is one reason why. This is one reason why pilots generally avoid circling to land or taking off east at Telluride–you need more room to turn around. If you must reverse course in a tight canyon, maneuver the plane to one side, slow down, and drop a notch of flaps to reduce turning radius.
High Density-Altitude Takeoff Procedures
Finally, a few general tips regarding high density-altitude takeoffs.
As mentioned, clearing obstacles or terrain after takeoff is a major consideration as to whether you can safely depart a given high-elevation airport. Along with studying the charts beforehand, when arriving at a new-to-me high-elevation airport, I scout the terrain from the traffic pattern BEFORE LANDING and note what direction I could fly after takeoff toward the lowest terrain with minimum climb. I then record that info and clip it to the yoke. Departing Telluride the only way to go is west down the San Miguel River Canyon. Here at Flagstaff, the terrain descends toward the south over I-17, but departing in any other direction requires climbing. If takeoff performance stinks, I want to know before takeoff which way to steer.
Lean the engine at full power during pre-takeoff run-up to ensure maximum takeoff power. This is done the same way as you would in cruise, with a nudge toward the rich side of peak rpm or EGT.
Following rotation, accelerate in ground effect to best rate of climb speed before beginning your actual climb. Since engine power and propellor efficiency are diminished at high density altitude you will not experience the sort of acceleration, clean rotation, and climb performance you’re used to. This procedure prevents you from pitching up too much/too early into climb and potentially stalling the airplane upon leaving ground effect.
Among the biggest threats of high D.A. takeoffs and landings is perceptual. Prepare yourself mentally to fly by the numbers, regardless of what you see out the windshield. You’re gonna feel too fast approaching to land, and be startled at the long runway roll and poor climb rate on takeoff. (Expect to clear obstacles by dozens of feet, not hundreds as you might be used to.)
We Made It!
Jean and I launched for Telluride Friday morning, and with tailwinds flew a smooth and uneventful 1:45 flight. We spotted the airport shortly after entering the canyon, and with no other traffic, landed uneventfully.
Following a fun weekend of hiking and dining we roused our hosts too-early Sunday morning to take us to the airport, and although our takeoff run was long we cleared the runway in plenty of time. Density altitude at 8am, with outside air temp ~50F, was 10,200 feet. Our climb rate ranged from 3-500 rpm, not impressive but better than I’d expected. That marginal performance actually turned out to be a plus because as we rolled down Runway 27 a jet reported inbound on the Runway 9 instrument approach but we passed way below him still climbing out of the canyon. (Another good reason to have previewed instrument-approach paths and altitudes, so we knew we wouldn’t conflict.)
You’re probably thinking “that’s a crazy amount of work and planning just to land somewhere.” That may be true, but our lives could depend on it. And once you’ve experienced a given airport a time or two the process is much simplified. Now that I have twice personally experienced Telluride’s setting and terrain, and know that the Flying Carpet will take off comfortably from there at a given weight and density altitude, I’ll need to do little more next time than check weather parameters–and be prepared to cancel or stay over if those parameters depart my safety range.
This is not intended to provide comprehensive guidance as there are many more mountain flying principles not described here. But hopefully you’ll find this example useful for basic understanding.
PS: Those flying turbocharged aircraft will experience all the above effects but with better takeoff and climb performance. (You’ll still use more runway on take off and landing.)
“Care to meet up at Sedona, Greg, for Sunday breakfast?”
It was Mike Harrison, a recently certificated 130-hour private pilot flying out of Phoenix’s Falcon Field (KFFZ). This would be Mike’s first warm-weather flight to Arizona’s high country and his wife Tammie’s first cross-country.
Sedona’s 5000-foot elevation diminishes aircraft performance due to “high density-altitude,” meaning air thinned by the combined effects of altitude and elevated temperature.
We partially counter it by flying lightened airplanes at cool times of day. To prepare, Mike had flown there with a more experienced pilot, but on a cooler day, so we reviewed procedures. His preparation was impressive.
Mike had planned his flight with just enough fuel for safe reserve, putting his Piper Warrior a healthy 200 pounds under gross weight departing Sedona Airport (KSEZ).
He intended to land at 7am, and depart by 9am in 70ºF temperatures. He would lean the mixture before takeoff, and accelerate in ground effect to climb speed before ascending. Landing uphill on Sedona’s sloped runway and launching downhill would shorten his landing and takeoff rolls.
Meanwhile, Jean and I debated whether to fly 20 miles from Flagstaff to Sedona. Driving there via mountain roads would take 45 minutes, so we launched grinning into crisp morning air.
“It’s time for a longer flying trip,” she said, as we plummeted moments later between crimson spires to Sedona’s traffic pattern. While 3,500 feet higher than Falcon Field, Sedona is 2,000 feet lower than Flagstaff…
If you ask my wife and me to name our most memorable journey in our decades of flying, we’ll both respond with our “long journey north” from Phoenix to the Canadian border for a relative’s funeral.
I wrote a column about this trip years ago, recently revisited as I work on an upcoming book project. But the bigger rediscovery was a recorded talk I gave at the 2004 AOPA Expo detailing the memorable journey when it was still fresh.
The trip was spontaneous, hardly planned, and involved crossing much of the country in a Cessna 182 through difficult weather. But we all know how it is with family events, right? There was no choice but to go.
Along the way we experienced numerous aviation adventures, our wackiest “airport car” ever, and some of the craziness found in every family.
Pilot listeners will also appreciate the details I reveal along the way, about how we make piloting decisions to get us to faraway destinations by light airplane, safely.
The talk is 50 minutes long, and I believe you’ll be compelled to sit through and enjoy it. So grab a seat, a cold drink, and have a listen!
Years ago when I instructed part-time in Indiana, my instrument student Pete presented a surprise opportunity to fly for his company.
“We’ll start with rental airplanes while you help pick out a suitable twin,” he offered during a lesson. Having only 140 hours of multiengine experience at the time, I questioned why he chose me.
“As an instructor you are thorough, cautious, and safe,” said Pete. “You’ll need a type-specific checkout and we’ll initially pay a higher insurance premium, but those are good investments in my opinion.” I took the job, and ultimately we purchased a cabin-class Piper Navajo.
My first lesson was how much work it takes running even a single-airplane corporate flight department. I spent more time managing maintenance and logistics than piloting.
For one thing, radios were less reliable back then, meaning frequent visits to the avionics shop.
Then one day the landing gear wouldn’t retract after takeoff. Better that than not extending for landing, but flying the normally speedy twin home from the East Coast at 130 knots maximum-gear-extended speed was memorable for the wrong reasons…
A day-long snowstorm had just passed when I flew Jean to Phoenix to see her mom. Lingering flurries receded to the east, while from the west approached the intense cobalt skies seen only after snow.
By the time I dropped Jean and steered for my next appointment at Prescott, a few new snow showers sprinkled northern Arizona’s mountains. No worry–Flagstaff’s San Francisco Peaks beckoned clearly from between them for my subsequent flight home.
Ninety minutes later, I preflighted for my final fifty-mile hop. Prescott’s Love Field Airport lies in an open valley, with Flagstaff 2,000 feet higher at the base of Arizona’s tallest mountains. Therefore you can usually see Flagstaff’s “Peaks” directly from Prescott’s airport tiedowns.
Now, however, the snow showers between here and home were denser than before…
“For once,” said Jean, “a routine flight.” We cruised homeward through cool, calm skies thanks to a high overcast filtering New Mexico’s high-desert summertime sun.
Driving from Flagstaff to Alamogordo takes eight hours each way. Going commercially requires two airline legs plus ninety minutes’ drive from El Paso. So general aviation truly offers the fastest way to get there, circumstances permitting, and this weekend was proving to be such an occasion.
But what is a routine flight, anyway? Piloting light airplanes turns out to be more about anomaly than routine. However often we travel a given route, every flight is different. Most aviators learn to appreciate that variety as adventure, but anyone expecting uneventful aerial “auto trips” is doomed to disappointment…
“Hey Greg! I’ve just experienced my first two engine failures—in one trip!”
Flight instructor Jim Pitman had just ferried a 1946 Ercoupe from Wisconsin to Arizona, and wanted to brainstorm what might have caused the power losses.
“The seller had kept the annual current and run the engine regularly, but hadn’t flown the plane in a few years. Following a thorough preflight inspection and engine runup, I departed Rice Lake Regional Airport (KRPD) for Storm Lake, Iowa (KSLB), where I stayed in a neat lakeside hotel.”
After waiting for fog to lift the next morning, Jim launched toward Phoenix with refueling stops at Smith Center, Kansas (K82), Dalhart, Texas (KDHT), and Belen, New Mexico (E80).
Following a slight diversion for thunderstorms, he crossed the Mazatzal mountain range east of Phoenix in darkness, “which was fine because I am very familiar with the area,” and overnighted at his home field, Phoenix Deer Valley Airport (KDVT). After 15.3 flight hours from Rice Lake, all that remained the next morning was 60 minutes to Salome Arizona. Deer Valley Tower issued Jim an intersection departure from Runway 7R.
“When I lifted off, the engine lost power and the plane settled back on the main gear. As the nose came down, the engine regained power just as I pulled the throttle to abort the takeoff.” Back at the ramp, Jim thoroughly tested the engine. Everything worked fine and having so much time in the airplane, he figured the culprit was a one-time bit of water in the fuel. Still, as a precaution he requested full runway length for his next departure…