Cockpit Preparation and Aircraft Systems: Airplane and Airline FAQ

The cockpit, also referred to as the flight deck, is the central nervous system of the entire operation. There are more than 500 switches, dials, knobs, gauges, buttons, lights, and circuit breakers. The flight crew is required to know the function of every single one. The newer airplanes have up to 140 on-board computers, some accessed by the flight crew through two central flight-management computers, and some fully automatic.

In front of both the captain and co-pilot are a complete set of flight controls and flight instruments, so that either pilot can fly the airplane. Between the pilots is the radio equipment used to talk with Air Traffic Control, other aircraft, and the company. There is also new data-link communications equipment called Automatic Crew Ad dressing and Reporting System (ACARS), which is capable of faxing information between the ground and the aircraft and vice versa. Just forward of the radio console is the throttle quadrant, the location of the thrust levers, slats and flap controls, and speed brake handle. On the forward instrument panel, clearly visible to both pilots, are all the engine instruments and the weather radar display. The only prominent handle on the forward panel is the gear lever, used to raise and lower the landing gear, which is conspicuously away from all the other flight controls. On most aircraft, above that is the autopilot mode control panel— within easy reach of either pilot. Overhead on a two-pilot airplane are the controls for the basic systems, including fuel, electrical hydraulic, ice and rain protection, and pressurization. On a three-pilot airplane these controls are, on a side facing the flight engineer’s panel.

COCKPIT PREPARATION

After stowing their luggage, the first task the crew members do upon entering the cockpit is check the maintenance log book. The log chronicles the aircraft’s most recent mechanical history. If the mechanic found the plane in satisfactory condition, he will sign the aircraft off as airworthy. If there was a problem and he has already fixed it, the log will indicate the problem, the repair, and his signoff. If the mechanic is still working on the plane, a red out-of-service tag is prominently displayed in the cockpit, indicating to the flight crew not to activate any switches.

REPAIRS

What if there is something wrong with the airplane that can’t be fixed during the scheduled ground time between flights? In other words, if the plane is not completely 100 percent, can it still be airworthy? The answer is found in the MEL-CDL, an acronym for Minimum Equipment List m Configuration Deviation List. This on-board FAA-approved Aircraft Restrictions Manual clearly defines the acceptable parameters for less than a 100 percent perfect airplane.

Do not confuse the word safe for the word perfect. Take your car as an example. If the headlights on your car were faulty, your automobile would still be safe to drive during the daytime, even though your car is not perfect. Similar parameters work for an airplane also.

There are two types of mechanical problems covered by the MEL-CDL. First there are those things described as “no-go items,” which are obviously required to be in perfect working order for every flight. For example, the wings, flight controls, engines, hydraulic system, landing gear, and tires. If they are not in perfect condition before departure, the airplane doesn’t go until they are.

In order to minimize any chance of misinterpretation, the MEL is written as a “discrepancies you can fly safely with” manual. This means any maintenance item not specifically covered by the MEL, for whatever reason, automatically becomes a no-go item.

Then there are the systems not required on every flight. The MEL very specifically breaks down these problems into three distinct categories: (1) the flight is permitted back to a maintenance station where mechanics and parts are avail able to fix the problem; (2) maintenance can be deferred up to 72 hours; and (3) maintenance can be deferred up to ten days. In all three cases the applicable flight limitations must be observed. For example, if the wing anti-ice system is inoperative, you cannot fly into known icing conditions. If the oxygen masks are faulty in a row of seats, that row must be blocked off from passenger use.

There is a reason repairs are not always made immediately—the prohibitive cost of stocking every spare part for every single airplane at every airport in the country. All airlines stock essentials like tires, brakes, radios, and the other obvious no-go items, despite the huge cost. But not every station can store equipment such as air data computers, engine generators, and autopilots, especially equipment that rarely breaks down.

If an airplane has an item that cannot be immediately fixed, it is entered into the aircraft log book as a “maintenance carryover item,” or MCO. The on-board Aircraft Restrictions Manual will state the specific limitations for the flight, and as a secondary reminder to the flight crew, a placard fixed to the instrument panel acts as an advisory.

The CDL covers those items not necessary for flight. Cabin curtains, coffee makers, entertainment systems, access doors, and other cosmetic features. Repairs on these pieces of equipment are made in a timely manner and do not restrict the airworthiness of the plane.

Just like the exterior walkaround before each flight, the new crew must do an acceptance check of the cockpit to verify all the systems are normal.

THE ELECTRICAL SYSTEM

With more than 15,000 electronic devices on board an airplane, this system is obviously intricate and complex. There are three basic ways that planes receive electrical power.

The first is external power. When looking at the nose of an aircraft parked at the gate, you may have noticed a long extension-type cord connected to it. This usually runs from the jetway and is plugged into the nose area of the plane. Like a household appliance, external electrical power connects the plane with the local power company, which is more cost effective than having the airplane generate its own power.

Most aircraft use 120 volts A.C., just like your home, except the frequency at 400 Hertz (cycles per second) is far greater than your 60 cycles at home. Unlike your toaster oven, or refrigerator, aircraft systems are very sensitive to voltage and frequency fluctuations. If you have ever been sitting inside a plane at the gate and noticed the main lights go out and the emergency lights come on, it may have been caused by the external power temporarily surging out of tolerance, causing the airplane’s electrical system—loaded with microchips and computers—to drop off line as protection. Resetting the system, just like resetting a circuit breaker at home, will correct a transient fault.

The second source of ground power comes from the APU—Auxiliary Power Unit. The APU is a small jet engine, about the size of an engine on a commuter-type aircraft (minus the propeller). It’s housed internally near the tail of the plane. APU’s are quite noisy, and more expensive than external power because of the added fuel usage. But they have the advantage of generating electrical power to very exact tolerances, while also generating the compressed air necessary to run the air-conditioning sys tem on the ground.

The third form of electricity is the ship’s generators, which are mounted to the plane’s engines. A twin-engine airplane, like the 757 and 767, for example, has two engine-driven generators. As the engine rotates, it turns the generator, which creates electricity. Since engine speed is varied from takeoff to cruise to landing, the genera tor is connected to the engine through a CSD, a constant speed drive, which is a transmission-type device that keeps the generator speed constant through various flight regimes.

Each generator is capable of producing 90,000 watts, the equivalent of 750 amps. By comparison, your average household uses a maximum of 150 to 200 amps. As a backup to a double failure on a two-engine airplane, triple or quadruple failure on a three- or four-engine craft, the APU is started and can generate enough electrical power to operate the entire essential electrical system without interruption.

What if all the generators failed? And the APU? Then there is still a battery backup. The battery, which is constantly being charged by an on-board battery charger, stores enough power to run the essential electrical system for up to 30 to 45 minutes—more than ample time to fly to a suitable airport and land. On long overseas flights where you are more than 30 to 45 minutes from the closest airport, an additional electrical system is available. The Hydraulic Motor Generator (HMG) uses circulating hydraulic fluid to turn an additional electric generator to provide power.

AIR-CONDITIONING AND PRESSURIZATION

These two systems are related, since the same air used to pressurize the airplane is also used to regulate temperature.

The pressurization system keeps the pressure of the air in the cabin as close to sea-level pressure as possible. Keep in mind: the percent of oxygen in the upper atmosphere is identical to the percent near the earth’s surface, only the pressure of the air decreases. As an aircraft climbs, a mechanism to compress the air is needed. Interestingly, just as we need the relatively dense air of the lower atmosphere to breathe, those big engines need lots of dense air to mix with fuel to create the combustion that generates thrust. Thus the two requirements for sea level—type air can be met with one solution.

The first two sections of a modern turbofan engine, well in front of the parts of the engine associated with combustion, are simply air compressors. As air enters the big, wide intake of the front of the engine, it passes through thirteen stages of rotors, each compressing the outside air one step closer to sea-level density. At the end of the thirteenth stage we still have clean, healthy, breathable air, except the by-product of compression is heat. Even before the air reaches the multiple combustion chambers, the temperature of the air can reach up to 350 degrees.

This hot compressed air can be used in a number of ways. Primarily it flows into the second section of the engine to provide the air needed for combustion. But by opening up a series of bleed air valves, called such because they bleed air away from the engine, hot air can be routed to the parts of the aircraft that need anti-ice protection. Also, compressed air can be routed to the cabin to provide air at a breathable pressure.

Obviously, though, before this hot air is routed to the cabin it needs to be sufficiently cooled to a more livable temperature. For just this reason the system is called the air-conditioning and pressurization system and not air- conditioning, heating, and pressurization.

The hot air then goes to two or three air-conditioning units called Air Cycle Machines. The capacity and number of units is dependent on the size of the airplane. The Air Cycle Machine serves the same function as your home air conditioner, converting hot air into cold air, but is different because it doesn’t use freon or any other gases to cool the air.

Inside the ACM the hot bleed air is ducted—like the ducting in your house, except with protective thermal insulation—to the heat exchanger. Taking advantage of the cold outside temperature at cruising altitudes—down to

—56 degrees—this cold air is scooped up through an intake near the front underbelly of the plane, allowed to pass around the airtight plumbing carrying the air, which dissipates the heat as the cold air is exhausted overboard. Multiple trips through the heat exchangers will cool this breathable air quickly. At lower altitudes and on the ground fans can be utilized to enhance the system.

Before exiting the Air Cycle Machine, the air is re expanded for one additional stage of cooling. Simple physics says that compressed air will heat up and expanded air will cool down. In order to obtain the desired cabin temperature, air from three different sections of the ACM, hot, cool, and cold are mixed.

If an ACM temperature controller were ever to become erratic, causing fluctuating temperatures in the aircraft, a secondary manual backup can be used to move the temperature mixing valves. If the valves were to fail in the hot position, there are multiple automatic shutoff systems to force the system to put out colder air, or if necessary, turn that one ACM off completely. Since the flight attendants and pilots feel the same temperature of air as the passengers, the system rarely reaches a temperature causing an automatic trip-off.

Planes are divided into different independent temperature zones. Because humans give off heat, a section of the aircraft that is full requires more cooling than a section that is empty. The cockpit has its own zone because the heat generated by all the avionics and other instruments makes the demand for colder air greater than the rest of the plane. Since we all like slightly different temperatures, there is a tiny air-conditioning outlet above each and every seat, an individual valve that gets air from the cold side of the ACM. It is circulated by the aircraft gasper fan.

One additional point: Sometimes during the hot summer months, airplanes are too hot on the ground, and just after departure they become too cold. On the ground the Air Cycle Machines cannot work to capacity because the volume of air provided by the APU is significantly less than the engine compressors. After takeoff, they sometimes work too well, until they can be adjusted by the flight crew. Occasionally, then, on a hot day, condensation drips from the panels in the ceiling. Passengers naturally assume the plane is leaking, but what is really happening is the cold air plumbing is sweating, and the moisture droplets are drip ping from the exterior part of the pipes. It’s the same thing that occurs when a can of soda is taken from the refrigerator and placed on a counter; it sweats even if the can has never been opened. Under some temperature differences, fog can form and be mistaken for smoke. If there are extreme temperature differences between the cabin and the colder air-conditioning ducting, condensation can actually freeze and a little snow can fall.

PRESSURIZATION

The pressurization system on board an aircraft is one of the simpler systems to understand. The amount of air entering the cabin, after being cooled to the desired temperature, is nearly constant. By regulating the amount of air exiting the cabin, you can regulate the pressure inside.

Air enters continually at nearly 6000 cubic feet a minute. It takes only 180 seconds for the cabin to have a completely new supply of air. The amount exiting is determined by the position of an outflow valve. All aircraft have one or more large (one to two feet across) holes, usually near the tail of the plane, that can be regulated from fully opened to fully closed by moving an outflow valve. Fully open, all 6000 cubic feet of air will pass through the cabin and exit through the open outflow valve, keeping the plane completely unpressurized. Fully closed, the pressure will build to a point of maximum pressurization, and the automatic pressurization valves will open, returning the pressure to nor mal. Most of the time the multiple valves are regulated somewhere between fully open and fully closed, in extremely small increments to keep the internal pressure as desired. In the very unlikely case a small pressure leak were to develop around a door seal, for instance, the pressurization would be unaffected because the outflow valve would close farther, keeping the exiting air a constant.

Sometimes pressure changes can be felt in your ears. The pressurization rates of change are kept below 500 feet per minute while climbing and 300 feet per minute while descending. These are lesser rates than many of today’s high-rise elevators. Surges are sometimes felt because the pressure-regulating valves that keep the inflow a constant volume do not adjust rapidly enough to the changing power settings of the engine.

The pressurization system has multiple redundant back ups. All aircraft have a minimum of one fully automatic system, a standby automatic system, and a manual system where the pilots can control the outflow valve directly.

HYDRAULIC SYSTEM

An airplane hydraulic system is similar to the power steering or brakes in an automobile. It reduces the force necessary to operate the flight controls.

Multiple hydraulic pumps pressurize the system to 3000 psi (pounds per square inch). When the controls are moved in the cockpit, signals are sent via cables and/or wires to the hydraulic valves. As the valves are moved, the hydraulic fluid, a basically incompressible liquid, is forced from one part of the system to the actuators, the mechanisms that actually move the massive flight controls. Other components tied to the hydraulic system are: the landing gear and brakes; slats and flaps; speed brake/spoiler; and the nose- wheel steering used on the ground.

Aircraft have at least three independent hydraulic systems, with a minimum of two pumps in each system. One system alone is capable of running all the essential hydraulic equipment. The pumps all have independent power sources, some engine-driven, some electric, and others driven by engine bleed air.

In the event all three independent systems were to fail simultaneously, there is a Ram Air Turbine (RAT) backup. On newer aircraft this turbine automatically drops from the lower fuselage, exposing a large propeller blade to the stream of air passing the plane. The propeller spins, turning a motor that pressurizes a standby hydraulic system. If the RAT fails to deploy automatically, the pilots have a manual override.

FUEL SYSTEM

As mentioned in a previous section, aircraft have what are called wet wings, meaning fuel is, housed in the wings themselves. If additional fuel is required, it is stored in a center tank in the lower fuselage. However, it is more desirable to use the wing tanks first, because fuel in the wings adds to their structure and strength.

Refueling of all the tanks is accomplished from one location, usually at the leading edge of either wing. Fuel is pumped under pressure at a rate of 750 gallons per minute. Additional fueling hoses can be connected to increase the rate, a necessity when 25,000 to 50,000 gallons of fuel must be boarded for many of the long overseas flights.

A carryover from the propeller days, jets still have the over-wing fueling caps, whereby a fueler can climb on the top of the wing and manually refill the plane.

There are multiple ways to determine exactly how much fuel is left in the tanks at any given time. Before the plane ever leaves the gate, the aircraft fueler must deliver to the pilots a copy of the fuel slip indicating exactly how much fuel was boarded at this station and the total quantity reading of his remote gauges. This information is compared with both the fuel totalizer and the individual tank quantity gauges. If there is any discrepancy, the error must be located before the appropriate repair can be made.

Using what is called the drip-stick method, the actual quantity of fuel in each tank can be exactly determined. Multiple narrow tubes with a hole in the center are pulled down from various locations in the tanks. If the tank is full, moving the stick down ever so slightly will cause fuel to flow over the top of the stick and out the tube. If the tank is completely empty, no fuel will drip even when the stick is drawn fully out. The calibrated drip stick will indicate directly the quantity of fuel in that tank.

Once the engines are started, the fuel used indicators become active. There are gauges that measure precisely the amount of fuel used by each individual engine. At pushback the crew knows exactly how much fuel they have on board. In the unlikely happenstance the entire fuel quantity system was to fail at once, they could still subtract the fuel used from the beginning total and ascertain the fuel remaining.

Each fuel tank has a minimum of two independent fuel pumps, each capable of pumping fuel under pressure to the engines. If both failed in the same tank, the engines still have the capability of suction feeding fuel from the tank to the engines. Additionally, they can also cross-feed fuel, or route fuel from the right tank to the left engine and vice versa.

CARGO HEATING SYSTEM

The cargo compartment is normally kept at a temperature around 45 degrees. If there are any live animals, a vent is opened to divert part of the pressurization and air-conditioning air, heating this section of the cargo compartment to a more comfortable 65 degrees. This vent switch is occasionally referred to as the dead dog switch, because an error in its operation can cause an animal to freeze, particularly on a long flight. However, it is becoming routine to wire this switch permanently in the on position. But not every airplane has been modified.

The reason for the cargo vent switch is that by reducing the air pressure and heat in the cargo compartment, you reduce the chance of something flammable that’s been illegally carried in a passengers’ luggage from catching on fire. Today’s aircraft have heat and fire detectors, and fire extinguishers for the cargo compartment that can be remotely operated from the cockpit.

FLIGHT INSTRUMENTS

The basic flight instruments are grouped in the same position on every aircraft, which makes the transition from one aircraft to another easier. There are two types of flight instruments: the old-style electromechanical, which uses electricity to work a mechanical device. This system is excellent, but with many moving parts, regular maintenance is required. The new systems use CRT’s—or Cathode Ray Tubes—like computer monitors. They have no moving parts and are virtually maintenance free. When the picture tube wears out, you can simply replace it. Current airplanes have no less than six screens. If one monitor should fail in flight, its information can be displayed on another screen. These new displays are commonly referred to as glass cockpits.

FLYING IN THE CLOUDS

In front of both the captain and co-pilot are attitude indicators. This instrument is a gyroscope that spins extremely fast, 20,000 RPM’s, which keep the instrument perpendicular to the earth regardless of whether the plane is climbing or descending, turning left or right. As an air plane banks, for example, the case of the instrument has to move the same degree as the plane itself, because they are physically attached. However, the interior gyro scope, supported by free-swinging gimbals, stays level with the horizon at all times. The difference between the two is displayed to the pilots as the plane’s attitude. On older planes the attitude indicator is electromechanical. On newer aircraft they are laser (light) gyroscopes. No less than three gyroscopes are required, with one being powered directly by the battery in case of a total electrical failure. On the new aircraft with laser gyros, an additional old-style electromechanical backup is still carried.

DETERMINING DIRECTION

Airplanes have compasses, but their use is limited. If you have ever used a compass, either the kind with the rotating needles that point to magnetic north or the models with a free-swinging compass card, you know how movement caused the compass to swing. Reliable readings were difficult in anything but a steady state. Include the radio and magnetic interference of an airplane, and you see a more precise form of directional information is needed.

On planes, heading information is received from com passes remotely located in the wing tips. This location reduces the interference. Their information is transmitted to the heading indicators in the cockpit, which, like the attitude indicator, has a built-in gyroscope that spins at a very high velocity, making the compass display immune to the motion of the plane.

Each pilot has a minimum of two heading indicators at his position. The captain’s primary indicator serves as the co-pilot’s secondary and vice versa, so a constant comparison can be made easily. If any inconsistencies exist between the independent systems, an instrument comparator warning will serve as a backup alert to the crew.

As is the case with attitude indicators, newer aircraft have replaced the electromechanical heading indicators with laser gyros. Since laser gyros operate at the speed of light, (186,000 miles per second), and are unaffected by Interference, their accuracy is unsurpassed. In fact the same laser gyros used today were used on the Apollo Space Missions to the moon.

DETERMINING ALTITUDE

Altitude is determined by an altimeter, and two distinct types are installed on commercial aircraft. The first, the barometric altimeter, senses barometric pressure and converts that into a reading of height above sea level. As the plane ascends, the barometric pressures decrease, so the indicator senses less pressure. Barometric altimeters display altitude to the nearest 20 feet.

Because baro-altimeters sense altitude above sea level, they will not read zero when you are on the ground. The lowest commercial airport in the United States is New Orleans at 4 feet above sea level. If you were on the ground at Denver, your barometric altimeter would read 5333 feet, the height above sea level at Stapleton Airport.

All cruising altitudes are assigned on the basis of feet above mean sea level or MSL. Mean sea-level altimetry is the most reliable over the entire flight regime, from takeoff to cruising altitude upward of 40,000 feet. Furthermore, all obstructions, including mountains, tall buildings, high antennas are displayed on aeronautical charts as height above sea level.

Every plane has two independent barometric altimeter systems, with an auxiliary backup for the captain and co-pilot.

The second altimeter system is the radio altimeter. By sending signals from the plane to the ground and measuring the time necessary for the signal to return, the exact height in feet above ground level (AGL) can be determined. Radio altimeters are used from the ground up to 2500 feet AGL. Above that their use would be limited. Radio altimeters on older aircraft are accurate to 10 feet; the latest equipment reads in 2-foot increments.

These two systems complement each other, especially on the approach to land. Airplanes approved for approaches and landings in foggy conditions where the runway visibility is poor must have a minimum of two independent radio altimeter systems to precisely measure the height above the runway during the last few moments prior to touchdown.

VERTICAL SPEED

Both barometric and radio altimeters give an accurate picture of current altitude, but do not directly measure the rate of change. When climbing or descending, it is important to be able to predict, with accuracy, your future altitude after a period of time. The vertical speed indicator, or VSI, is a barometric altimeter that measures the air plane’s rate of change up or down in units of feet per minute. The VSI scale has a range from zero to plus or minus 6000 feet per minute, and is accurate to the nearest 100 feet.

How do you use it? Let us say you are cruising at 35,000 feet and wish to descend to 10,000 feet in exactly 25 minutes. By lowering the nose of the aircraft until the vertical speed indicator reads minus 1000 feet per minute rate of change, you would be level at 10,000 feet in the allotted time.

AIRSPEED

In front of both the pilot and co-pilot is an airspeed indicator similar to a car’s speedometer. Its operation is much different, though. Basically, speed is determined by comparing two different readings.

In the front of the plane there are several pitot tubes protruding from the nose. During the walkaround they are checked to be free and clear. As the plane flies, air is forced into these tubes. As the forward velocity is increased, the air pressure, the ram air into these tubes, also increases.

Also, on the side of the fuselage are static ports, little holes strategically located where the air is relatively still even in flight. By comparing the ram air to the still air, airspeed is determined.

As a carryover possibly from the seafaring days, all airspeed is displayed in nautical miles per hour, commonly called knots. Since a nautical mile is 15 percent greater than a conventional road map statute mile, a knot of airspeed is 15 percent greater than miles per hour.

Unlike a car speedometer, the basic airspeed indicator doesn’t indicate true speed throughout the entire flight regime. The system, which begins registering at 60 knots (69 mph), depends on air being rammed into the pitot tubes. As an airplane climbs, the air density decreases, so less molecules are available to the airspeed system.

The difference between the plane’s true airspeed and the indicated airspeed read on the cockpit gauge become more apparent the higher you climb. For example, at 10,000 feet if your airspeed indicator reads 300 knots (345 mph), that would be very close to your true airspeed. However, at 35,000 feet your airspeed gauge may only indicate 260 knots (299 mph), even though you are really cruising at 460 knots (529 mph), because the pressure of the molecules available to be rammed into the pitot tube is significantly reduced.

The next question might very well be, with all those fancy computers on board, why can’t the airspeed gauge be recalibrated? The answer is, you don’t want it to be. Indicated airspeed, by its very definition of indicating the molecules available to the pitot tubes—and thus molecules available to support the wings, which support the rest of the plane in flight—is the truest measure of aircraft performance.

However, Air Traffic Control, whose primary responsibility is traffic separation, is not interested in performance airspeed, but the actual true airspeed. At the higher altitudes airspeed is measured in Mach numbers because they are more accurate. You may have heard the term Mach as it relates to supersonic air travel. Planes that are capable of flying faster than the speed of sound (760 miles per hour at sea level) are traveling faster than Mach 1. Commercial airliners are built to cruise at the more economical Mach .78 - Mach .86, or 78 - 86 percent of the speed of sound.

GROUND SPEED

Ground speed is how fast the plane is traveling over the ground. If we are cruising at 500 knots with a 100-knot tailwind, our ground speed will be 600 knots. Make a 180 degree U-turn into the wind and your ground speed will drop to 400 knots, even though your true airspeed of 500 knots never changes.

The prevailing upper air winds in the United States go from west to east. You can see why a Los Angeles—to— New York flight takes less time than New York to L.A.

TAXI SPEED

The cockpits of tall, widebody aircraft like the 767, L-101 1, DC-b, 747, A-300, are so high off the ground that taxi speed indicators are needed to accurately judge speed — especially when turning a corner on a taxiway. Since the normal airspeed indicator does not register until 60 knots, a separate taxi speed indicator that senses tire rotation just like in your automobile is provided for speeds from zero to 25 knots.

LOCAL WEATHER

After the cockpit crew is satisfied that all the systems are in perfect working order, the local weather is checked on an ATIS frequency. ATIS stands for Automatic Terminal In formation Service, and is a continuous loop tape recording of the most current local weather, field conditions, and status of general gate-holds. It is a time-saving device for the Air Traffic Controllers, who instead of having to read the weather, simply verify it has been received. Each new ATIS tape has the time of recording and a letter code to indicate it is current.

AIR TRAFFIC CONTROL CLEARANCE

Within thirty minutes of departure, and not before, the pilots radio the ATC pre-taxi clearance frequency, commonly called clearance delivery, to receive the specific route clearance filed by dispatch. If ATC cannot grant you your requested routing, an amended clearance will be issued. If there are any ATC delays in effect, an EDC— Expect Departure Clearance time—will be given, assuming the length of the delay is known.

When issuing a clearance, ATC will verify the destination airport, assign a departure SID if appropriate, give an initial climb to altitude—a hold down altitude until routed away from the inbound flights—an expected cruising altitude, the departure radio frequency (the first ATC controller to call after takeoff), and a distinct transponder code (more on this later).

Airlines routinely transport donor organs used in trans plant operations. There are times, especially when ATC delays are in effect, that a crew may wish to designate their flight as a Lifeguard Flight. By doing so, expedited handling and routing can be obtained, helping to ensure that the human organ shipments reach their destinations in the allotted time.

ACCEPTANCE CHECKLIST

Though at this point all preflight items have been checked and double-checked, verification of this fact is accomplished by using a written pre-departure checklist, featuring more than 60 items. One crew member reads while the other pilot verifies that each and every switch, button, and control is in its correct position.

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