Waypoints

High fliers

June 1, 2004

Editor in Chief Thomas B. Haines first logged time in a pressurized airplane on August 9, 1988.

Thirty degrees of bank, nose pitched down 20 degrees, the windscreen filled with green pastures, and the Earth rushing up at something greater than 6,000 feet per minute. The Mach meter heads for 0.75. At this rate, we'll make a very deep, but compact, crater. It'll be over quick, though.

The creaky old Cessna Citation seems to groan as I begin the pullout, attempting to be gentle on the old airplane and mindful of the eight passengers in back, some of them looking a little green by now. Still, the positive Gs scrunch us all down in the seats as the vertical speed indicator (VSI) comes off the peg and moves back up toward zero. Thrust levers up, speed brakes off; we're climbing again. Well, that was fun. Let's try it again, and again. Switch seats, and try it a few more times.

In a matter of just over two hours, all eight students will have experienced flying the Citation in level flight above Flight Level 250 and practiced at least one emergency descent after a simulated rapid depressurization. The day's quest? Technically it's to receive a high-altitude endorsement, necessary to log time in pressurized airplanes. But for most of the pilots, it's simply a way to log a few minutes — about 12 actually — of jet time. Boys' toys, and all. How else are most run-of-the-mill general aviation pilots going to get their hands on a jet?

The training, administered by Wisconsin Aviation in Watertown, Wisconsin, is fun, safe, and thorough.

The consensus about the jet? The pilots in the course, who typically fly light singles or light twins, all deemed the Citation as easier to fly and lighter on the controls than they expected.

For the price of $450 and a Saturday of their time, the enthusiastic pilots got the jet time and a logbook endorsement. Many pilots don't realize that in order to fly a pressurized airplane you must have a special logbook endorsement, unless you have logged time in a pressurized airplane prior to April 15, 1991. In that case, you're grandfathered and don't need the endorsement.

The FAA implemented the requirement at the request of the NTSB. During the 1980s, the NTSB noted a number of accidents and incidents where a common characteristic was the pilot's inexperience in dealing with pressurization systems and high-altitude flight. The board issued a safety recommendation to the FAA, asking that pilots be required to have formal training in pressurization systems and high-altitude flight. As a result, FAR 61.31 was changed to outline the specifics of the training required and the requirement for the endorsement.

Filling a vacuum

FlightSafety International, SimCom, SimuFlite, and other companies offering training in sophisticated simulators can grant the endorsements after a session in the simulator. I've practiced emergency descents after a simulated explosive depressurization in a FlightSafety Learjet 31 simulator in Tucson, Arizona. It's almost as eye-opening as doing it in the real airplane.

Recognizing that some pilots might prefer to earn the endorsement without going through a complete airplane checkout course at a simulation company, Michael Sullivan, a charter pilot at Wisconsin Aviation and an FAA Gold Seal instructor, began checking out options. He worked with Jeffrey Baum, president of Wisconsin Aviation, an innovative and successful FBO and charter company with three locations in the Badger State, to develop the business plan. The trick was to keep the costs low enough to make it attractive to pilots. The key to making it work economically is to use an older Citation with a high-density interior that allows seating for 10, including the two pilots up front. Wisconsin Aviation has such an airplane in its charter fleet. Sullivan developed the curriculum, using the FARs as a guideline, and the course was born. It was first offered in 1999 and is now held several times annually whenever Sullivan can get a group of eight together on a Saturday in Watertown.

The group spends the morning working through a 28-page course outline, with Sullivan leading the class. As required by the regulations, the course touches on a variety of subjects relating to both high-altitude flight and pressurization systems. For pilots used to flying light airplanes, Sullivan stresses the need to understand at least the basics of high-altitude aerodynamics and the need to carefully plan descents. He offers several methods for computing descent points and describes the capabilities of turbine engines, but also notes how similar they are to piston engines from a performance standpoint. As with piston engines, the performance of turbine engines is affected by temperature and altitude.

Another section of the curriculum addresses pilot physiology, which relates to the requirement for practicing emergency descents. If a pressurization system fails or in the case of a rapid depressurization (defined as occurring within three seconds), the pilot must be prepared to instantly don an oxygen mask and descend the airplane to an altitude where those on board can survive. Time of useful consciousness at FL350, for example, is between 30 and 60 seconds, depending on the individual. Above FL430, it decreases to only 9 to 12 seconds. Given that a rapid depressurization will create a great deal of noise and water vapor instantly in the cockpit — and confusion — the pilots may well be unconscious before they have time to react. Because of the dangers of flight at those altitudes, when operating above FL350 at least one pilot on charter flights must wear an oxygen mask at all times. If one pilot leaves the flight deck above FL250, the other must wear an oxygen mask.

Between FL250 and through FL350, at least one pilot must wear an oxygen mask unless both are equipped with quick-donning masks, which most aircraft now have. Part of the Wisconsin Aviation curriculum requires the pilots to practice putting on two different types of oxygen masks. It's tricky enough sitting in a conference room. It must be truly challenging when a window has just blown out at FL350.

Rapid depressurizations are in fact very rare. The most famous recent pressurization accident involved golfer Payne Stewart. The pressurization system in the Learjet he was riding in failed — apparently subtly enough that the crew was unconscious before any of the warning systems kicked in. The autopilot flew the airplane to altitudes as high as 45,000 feet until it ran out of fuel and crashed into a South Dakota field. The NTSB was not able to determine why the pressurization system failed.

With ground school out of the way, each class member is given a thorough briefing in the cockpit. With the student in the pilot seat, Sullivan goes over the flow pattern necessary in the event of a pressurization problem. Oxygen mask on, oxygen flow switch on, passenger oxygen switch on, igniters on, passenger advisory light on, thrust levers to flight idle, speed brakes out, roll into a 30-degree bank to aerodynamically load up the wings (preventing a negative-G situation that can unport fuel), and pitch down to at least a 15-degree attitude. Roll wings level, and manage the rate of descent so as to not exceed V MO/M MO. Descent rates will peg the VSI at 6,000 fpm.

Once reaching a safe altitude of about 15,000 feet, the pilot would level the airplane and begin troubleshooting.

The drill in our case was to level at FL270 and hand-fly the airplane for a few minutes. From the right seat, pilot Tim Holbach would then clap his hands to simulate a rapid depressurization. Pavlovlike, the pilot flying would quickly run through the flow pattern while the rest of us in the back would prepare for the roller coaster ride that occurred when the pilot rolled in the bank and began the rapid descent.

ATC assigned us a block altitude from FL230 to FL270. Passing through FL240, Holbach would signal the all clear and the pilot would recover the airplane and climb back up to FL270. Most pilots practiced two emergency descents, but when a few started feeling a bit nauseated, we cut it back to one each. A short time later, Holbach and his partner Bill Paul safely landed the packed Citation in a stiff crosswind back at Watertown.

With logbooks endorsed, the pilots climbed aboard more pedestrian steeds for their trips home, hoping against hope that a little of that kerosene smell would still be there when they got home for some hangar flying.


E-mail the author at thomas.haines@aopa.org.


Links to additional information about high-altitude flying may be found on AOPA Online ( www.aopa.org/pilot/links.shtml). For more information about the course, contact Wisconsin Aviation at 800/657-0761.