Swept Wing

THE SWEPT WING

A STANDARD FOR TRANSPORT CATEGORY AIRCRAFT

MOST OF THE training aircraft you will fly use the rectangular or semi-tapered wing design. They provide stable and safe platforms for flying slow or even gliding when needed. One of the most prolific and utilized designs in Transport category aircraft, however, is the swept wing.

Since the birth of aviation, the goal has always been to go faster, farther, and higher. The swept-wing design helped push those goals beyond what was thought to be the limit. The entire design of a swept wing is a trick. The goal is to trick the airplane into believing it is flying slower than it actually is. It accomplishes this by allowing relative wind to strike the airfoil at an angle. This “tricks” the wing into believing it is flying at a speed slower than the actual true airspeed. Thus, the overall drag created is lower, allowing higher and faster flight.

The premise of the whole trick has everything to do with compressibility. The upper, curved portion of the wing acts like half of a venturi; the still-undisturbed air above the wing is the other half. This accelerates the relative wind over the wing. As an airfoil travels through the air at subsonic speeds, the air flowing over the wing might actually exceed the speed of sound, or Mach 1.0. This creates a shock wave over the wing that is drastically detrimental to performance, destroying lift and dramatically increasing drag. The speed at which these shock waves become apparent and critical is known as critical Mach. By tricking the wing into believing it is flying more slowly, the wing operates farther away from this critical point at higher speeds.

Using a thin, low-cambered wing increases the critical Mach number, allowing higher-speed flight. The downside here is low-airspeed flight. A swept, thin, low-cambered wing might be great for high-speed flight, but how about during takeoff and landing? To counteract these pitfalls, the leading and trailing edges are equipped with high-lift devices. Leading- and trailing-edge flaps increase the aircraft’s overall ability to produce lift by increasing wing area and reenergizing the local airflow. Combine the high-speed benefits of the swept wing with the low-speed generosity of Fowler flaps and leading-edge slats, and you have the efficient and proven design installed on almost every Transport category aircraft.

Runway Incursion Prevention

RUNWAY INCURSION PREVENTION

COMING TO AN AIRPORT NEAR YOU

THE INTERNATIONAL CIVIL Aviation Organization defines a runway incursion as “any occurrence at an aerodrome involving the incorrect presence of an aircraft, vehicle, or person on the protected area of a surface designated for the landing and takeoff of aircraft.” The FAA has worked hard to implement new procedures and technologies to help reduce and prevent runway incursions.

One such procedure was the implementation of a change of phraseology from “position and hold” to “line up and wait.” Some new technology that may still be unfamiliar is becoming more prominent around the United States.

Airport surface detection equipment, Model X, or ASDE-X, is ground-based traffic monitoring that provides ATC with location information for taxiing aircraft. ASDE-X is a fusion of information from surface movement radar, multilateration sensors, ADS-B sensors, and aircraft and vehicle transponders. This provides the controller with position and identification information of each aircraft on the ground. It can be invaluable in low-visibility situations or at night. The system can also produce aural and visual warnings of possible collisions.

What does this mean for the pilot? Airports that incorporate the ASDE-X system will request you to operate your Mode C transponder while on all runways and taxiways. Look in the Airport/Facility Directory to find if your destination utilizes ASDE-X.

Runway status lights, or RWSL, is a system comprised of sensors and lights that can show the pilot if a runway is occupied or otherwise unsafe.

Combined with ASDE-X technology, it can detect when aircraft or vehicles are occupying, crossing, departing, or landing on a runway. It provides status of the runway by use of runway entrance lights, takeoff hold lights, and runway intersection lights. These lights are in the pavement and show a line of red lights either across the entrance to the runway or alongside the centerline for takeoff hold lights. When the lights are illuminated pilots are advised not to enter or cross the runway or take off when given a “line up and wait” clearance.

Both technologies will increase safety as well as efficiency and capacity at U.S. airports. We pilots must ensure constant vigilance and situational awareness to help prevent runway incursions.

TCAS

TRAFFIC COLLISION AND AVOIDANCE SYSTEM

ANOTHER SET OF EYES IN THE SKY

ONE OF MANY systems you will find concurrently on turbojet aircraft is the Traffic Collision and Avoidance System, or TCAS. Following years of improvements and technological advances, TCAS provides basic and advanced aircraft avoidance through monitoring and interpreting of Mode C and Mode S transponders.

TCAS systems today can provide not only traffic information to supplement visual avoidance, but it can also provide escape guidance from the intruder aircraft. Early TCAS systems merely provided the azimuth of the intruder as well as its relative altitude. Now with the TA/RA mode equipped and enabled, you will receive a resolution advisory for the most expeditious way of escaping a collision.

Using escape path and trend information from each aircraft, the TCAS system determines whether a climb or descent is more appropriate for each respective aircraft. It then displays and aurally warns the crew by verbal and visual resolution advisories.

The TCAS systems of two equipped aircraft will even communicate to coordinate the escape. If one aircraft issues a descent advisory to the crew, the opposite crew will receive a climb advisory. The systems will continue to calculate the paths of the two aircraft to determine whether the current resolution is sufficient, or requires a higher rate of climb or descent. It will then issue a second advisory to either increase or decrease, or even maintain, a recommended vertical speed.

The FARs provide language involving a deviation of an ATC clearance in the event of a resolution advisory. The crew is to advise ATC as soon as practicable after such an incident. It is important to remember that nothing relieves the crew from being vigilant to see and avoid traffic; however, TCAS helps to identify and maintain visual contact with aircraft in high-traffic environments.

Flight In Known Icing

FIKI

Basics of the aircraft deice and anti-ice systems

Icing is one of the mostly daily occurrences of line flying. Since it’s often unavoidable, aircraft are equipped for flight into known icing conditions. That is to say, the aircraft has been tested and certified for flight into areas where icing conditions are known to exist. Since the day that mail began flying instead of riding the rails, the business goal has been to have a consistent and reliable schedule. The ability to fly into known icing is a critical component of scheduled service.

With most turbine aircraft, hot compressed air is drawn from the engine into an elaborate ducting system that leads the hot air to wing leading edges as well as engine nacelle lips and the horizontal stabilizer. This air is dubbed “bleed” air as it is “bled” from the engine core. Turbine aircraft often have many uses for this bleed air: pressurization, air conditioning, engine starting, and anti-icing.

When required, this extremely hot air can be tapped from the engine core and led to critical flight surfaces for anti-icing and deicing requirements. This can generally be done either manually or via automatic activation. Ice detector probes are designed in such a way that icing will form first on the probe. This probe is designed to vibrate at a specific frequency and when ice has accreted on its surface, that frequency of vibration changes. The system recognizes the ice buildup and, depending on the configuration of the system, it activates the anti-icing system. You can manually activate the system without the use of the detector probes.

During winter operations it’s often required that aircraft be deiced before takeoff. Remember you should never attempt to take off with snow, frost, or ice crystals adhering to the aircraft. The entire aircraft should be clean of contamination prior to takeoff—not just the control surfaces, or the wings and tail. This protects the aircraft during takeoff and initial climb. It can often be a two-part process: deicing the aircraft to remove contaminants, then a coating of anti-icing fluid. The latter is almost always required when freezing conditions are present and there is precipitation.

Combining the ice protection systems and the deicing and anti-icing technologies, we are able to provide safe and comfortable transport through the most inhospitable conditions.

initial operating experience

Transitioning from simulator to real world

The first time I flew a Transport-category aircraft, there were 50 people sitting comfortably in the back. I tried hard to not really think about it, but it’s hard to ignore. It was my first day of initial operating experience, or IOE. I had spent nearly two months training in a classroom and simulator, but this was the beginning of my actual aircraft training.

Much like almost any training program, there was a ground school, a written test, an oral exam, and a practical test in a simulator. Ground school covered all the aircraft systems, basic regulations, and company operations specifications. Simulator training consisted of basic instrument flying skills, emergency drills, and normal line flying. The checkride itself included items straight from the Airline Transport Pilot Practical Test Standards.

After completing the training program, I was scheduled for IOE with a company line instructor for two four-day trip sequences. It was his job to help consolidate my training and ensure that after all that training in the simulator, I could actually fly the aircraft. He would mentor and instruct me on the procedures.

At first the workload seems immense, and you wonder how you will ever get everything done on time—then it slowly eases. Everything you learned in ground school and in the simulator still applies, but now the time crunch is on. After day two or three I was starting to get my preflight preparations completed with time to spare.

It was during these first few days that the differences between flying the simulator and flying in the real world became dramatically apparent. Nuances of the airplane that couldn’t be duplicated, delays inherent to the system that required quick surmounting, dealing with passenger issues, baggage-handling delays—and most of all, weather.

Once I had completed a second four-day trip, my instructor signed me off for line flying. Unlike most certificates or ratings that only require the written, oral, and practical test, becoming a line-qualified FAR Part 121 pilot also requires this signoff. It’s like the final endorsement and seal of approval. It was like being given that first signoff for solo flight. I felt as though I was taking that first step alone. It’s an experience that I keep reliving in my flying career.