Turbine Pilot: Coast to coast in a light jet

A light jet owner’s first trip from coast to coast in his or her new airplane usually is both satisfying and edifying. It’s satisfying in that a trip that could take nearly 20 hours of flight, spread across two or even three days in a high-performance, single-engine piston, can be completed in a single day—albeit a long one. Beyond the time savings, the experience is dramatically less taxing in the jet; the lower noise and absence of vibration—that even an active noise-reducing headset cannot mask—makes a long day in a jet much less fatiguing than one a fraction as long in a propeller-driven aircraft. Further, the bulk of cruise time is nearly always spent in visual conditions, above any troubling weather.

The lighter jets in production, flying at their most efficient altitudes, experience real-world cruise speeds of 320 to 340 knots. Flying from the East Coast into a prevailing winter headwind can easily cut groundspeeds to the mid-200-knot range. The 2,200 or so nautical miles to be covered, therefore, often requires eight to nine flight hours. This flight time requirement creates its own problem: Light jets such as the Embraer Phenom 100 and Cessna Citation Mustang are more or less three-hour aircraft if a generous IFR fuel reserve is needed, or when facing a leg into a busy coastal airport where painfully early and fuel-robbing descents are the norm. A nine–hour flight like this demands very careful planning of each leg if the trip is to be completed with only two fuel stops. If headwinds are strong enough, a three-leg continental crossing may not be possible; I’ve flown my share of four-leg westbound trips.

For a late July trip recently completed, however, light summer headwinds aloft meant that a three-leg trip in the Cessna Citation Mustang looked very doable, with one large complication: high forecast temperatures across the country. Hot surface temps meant that being able to depart from our ideally positioned fuel stops with full fuel might be questionable; even with only two pilots on board, we faced weight restrictions that flirted with cuts into our fuel load.

Temperature, then, became our all-consuming obsession during final planning the day before departure. Clearly, starting the trip in the cool early morning hours was a must. We were somewhat aided by our direction of travel; flying west we “gained” an average of an hour per leg, thanks to time zone changes.

Small World Maps

Juxtaposing the runway analysis product for each fuel stop with an hour-by-hour temperature forecast for the respective airports, we could see the evening before our trip at approximately what hour we would no longer be able to take off with full fuel. For example, considering our first fuel stop at Eagle Creek Airport in Indianapolis, and knowing that full fuel would put our takeoff weight at 8,320 pounds (max takeoff weight is 8,645 pounds), we could see that takeoff from the anticipated active Runway 21 at or before 2 p.m. local time should safely allow us to depart with full tanks.

At our second fuel stop in Pueblo, Colorado, elevation 4,729 ft msl, we needed to depart by noon local time—assuming an anticipated surface temperature of 29 degrees Celsius/84 degrees Fahrenheit—to allow for full fuel. Fortunately, the calmest winds aloft of our trip were expected on the last leg, so we determined that for this leg, we would safely be able to depart with 200 pounds less than full tanks, giving us a bit more wiggle room with temperature.

The runway analysis itself proved instructional on this trip. For the first fuel stop we encountered an uncommon situation—our takeoff weight would be limited by our ability to clear an obstacle. While this is not in and of itself uncommon, somewhat unusually, we would be in a better position by selecting a higher takeoff flap setting. Typically, when the ability to clear obstacles with one engine inoperative restricts takeoff weight, using a lower, less draggy flap setting for departure is advantageous. However, in this case the runway was not very long, and the obstacles—trees at the departure end—were so close that the shortened takeoff roll with flaps set at 15 degrees would more than offset the additional drag.

At Pueblo we would run into another relatively rare performance situation. Our weight for takeoff from Runway 26L at temps above 29 degrees Celsius was not restricted by field length or obstacle clearance limits—as is often the case with hot and high departures—but rather by the ability of the aircraft to get to the manufacturer-created acceleration altitude within the 10 minutes the engines are permitted to operate at takeoff thrust.

Manufacturers can select an acceleration altitude, at which the pilot momentarily levels off and lets the airplane pick up sufficient speed to transition to a final flaps-up and continuous-thrust climb configuration. This altitude typically is no lower than 400 feet above field level (afl), and no higher than 1,500 feet afl.

Cessna uses 1,500 feet afl as the default acceleration altitude, and at the high density altitude conditions encountered at Pueblo, our average rate of climb could drop below 150 fpm following an engine failure. So, when the 10-minute takeoff thrust limit expired, we would still not be at our acceleration altitude. This was a condition the runway analysis software would not accept, and so we’d have to lower our allowed takeoff weight until we could reach 1,500 feet afl in exactly 10 minutes.

Fortunately, there’s nothing mandatory about using 1,500 feet for an acceleration altitude. We could opt to use one as low as 400 feet; Cessna’s official performance data calculated that we would easily be able to reach an emergency pattern altitude of 1,000 feet and limp back to land VFR if needed.

After such detailed planning, the execution of the trip itself was both smooth and anticlimactic. The temperature forecasts proved spot-on, as did our flight time estimates, so at both stops we were able to take on the planned fuel load—and on all three landings, we had comfortable reserves remaining. The weather for the trip was blissfully mild, and given the time of year and westbound direction, we had daylight for the entire trip.

Not every plan survives its first encounter with attempted execution, but in this case the time spent in planning paid off with a drama-free trip.

Neil Singer is a Master CFI with more than 8,500 hours over 15 years of flying.

While departing without flaps will allow an aircraft to better clear obstacles away from the airport, at times obstacles very close to the runway can only be cleared by using flaps for takeoff.