Aviation/Airline Prep for the Layman

Okay, this whole Malaysian Airlines thing has driven me to the point of insanity with all of the talking heads and so-called experts pontificating about what they know (and a lot about what they don’t IMHO). Although I don’t claim to be a virtual fount of information about the industry, I am one of the “insiders” who can at the very least give you a primer on what these folks on television are chattering on about.

MH 307. This is airline speak for Malaysian Airlines Flight 307. The MH is a two letter code identifying a particular carrier. UA would be United, DL is Delta, WN is Southwest, AA is American, and FL is AirTran (but not for long since they’re being absorbed into Southwest).

ACARS. This is the Aircraft Communications Addressing and Reporting System. This system, once initialized on the ground by the pilots, is an “always on” system that allows them to keep in communications with their respective carrier’s operations center. It additionally allows the aircraft to obtain performance data for takeoff and landing. Things like aircraft weight and balance, engine power settings, landing flap and autobrake (automatic braking) settings can be obtained through the ACARS. Local weather at departure and destination airports, as well as preflight departure clearances, are also available features that can be transmitted via ACARS. There are other features, including aircraft health monitoring that can be transmitted, but a lot of that depends on what the carrier is willing to pay for through its subscription service.

Departure Clearance. This is how ATC or Air Traffic Control communicates to the flight crew whether their requested flight routing has been approved or if there have been modifications to it. An initial climb altitude is normally specified in the clearance unless the there is a published departure route that has an initial altitude specified on it as well as any other limitations (for example interim altitudes and/or airspeeds). A four digit transponder code is normally assigned at this time which enables ATC to identify the flight while airborne or on the ground since most major airports have the capability to monitor ground movement of aircraft via their transponders (a safety measure).

ATC. We’ve already defined what this means, but this has been morphing over time into a concept called Air Traffic Management. From the time an aircraft begins taxiing from its departure airport until it taxis into the gate at its destination airport, it will normally be under the watchful eye of several controlling entities, this is part of what we call the National Airspace System. Depending on the size of the airport, there may be a ramp controller that controls departures and arrivals at airport terminal gates. There is a “handoff” (or change of control) to and from the ground controllers who are in charge of all taxi routes to and from the active runway(s). The tower controls all of the airborne traffic within the airport traffic area as well as all traffic on or crossing any runway. Departure and approach control facilities are transitional services that bridge the gap between airport and enroute traffic controllers. If enroute traffic schemes are like highways in the sky, then departure and arrival routes are like on and off ramps.

Enroute Air Traffic Management.  When you hear people talk about ATC, this is normally what they’re referring to. The enroute portions of our national airspace system are divided into various centers. Here in the lower 48, they would be: New York, Atlanta, Cleveland, Washington, Los Angeles, Kansas City, Boston, Indianapolis, Fort Worth, Houston, Memphis, Seattle, Oakland, Albuquerque, Salt Lake City, Jacksonville, Miami, Chicago, Minneapolis, and Denver. Each of these centers is composed of various sectors and each sector is manned by an air traffic controller who keeps a watchful eye on those aircraft transiting their area of responsibility. The transponder or “squawk” codes are how the controller identifies and keeps track of those flights. Each time an aircraft flies into or out of a specific sector or center airspace, there is a handoff process that takes place between the respective controllers.

Aircraft Navigation. How aircraft follow these highways in the sky is through the use of navigation equipment. There are two types of navigation systems that can be used: Those that are self-contained aboard the aircraft like the INS or Inertial Navigation System or those that utilize external signals like ground based radio navigation aids or satellite based navigation (i.e. GPS). Most commercial aircraft have a combination of all three systems at their disposal. These are all tied in together via a flight management system or FMS. Depending on the needs of the carrier (foreign or domestic routes, or both), the FMS will have a database of navigational waypoints, airports and their associated arrival and departure routes, as well as any instrument approaches applicable to runways serving those airports.

FMS and Automation. The flight management computer is the heart, soul, and brains of the aircraft. Any and all information that is applicable to the flight is entered via a control unit (also known as the box) with an alphanumeric keypad, multifunction buttons and a display screen. ACARS information is sent, received, and displayed through the box as well. Performance information received via ACARS can be used to control various aspects of the aircraft’s flight envelope. Engine power settings for climb and cruise are tied into the autothrottle system while waypoints for departure, enroute and arrival procedures can be sent to the autopilot through the FMS. There is a flight mode control panel on the glareshield that allows the pilots to control the vertical and horizontal flight modes of the aircraft with the autopilot engaged.  In certain cases the aircraft is capable of flying itself from shortly after takeoff all the way to a safe landing, depending on an airport’s navigation facilities. The level of automation can be tailored to whatever the needs of the flight crew are at any time.

Emergency Equipment. There are rafts, slides and other pieces of emergency equipment too numerous to get into here, so we’ll just focus on the two items that seem to be getting the most attention, the emergency locator transmitter (ELT) and the passenger oxygen masks. There are two types of ELTs that can be onboard an aircraft, both of which transmit a radio signal that can be picked up by aircraft and ships. The fixed version, which is mounted in the tail area may either be armed or activated from the flight deck. In the armed mode, the ELT activates once it experiences a sudden deceleration or G force on it. The portable ELT has similar features, but in the armed mode is activated by salt water. The passenger oxygen system is controlled from the flight deck and is either placed in the armed or on position. In the armed position, the masks will deploy from their storage positions once the cabin altitude reaches a predetermined point. Once activated, passengers are breathing a mixture of cabin air and pure oxygen. Normally this system is operational for approximately 15 to 20 minutes. It is designed to allow for an orderly descent from high altitudes to a safe altitude where the masks are no longer required.

Black Boxes. This term is a misnomer since these items are actually orange in color. The flight data recorder and cockpit voice recorder are systems designed to record information on a continuous loop.  The loop is interrupted once an event occurs of significant magnitude to cause a break in the recording of data. The boxes are located far enough in the aft fuselage of the aircraft that they will survive most “crashes”. In the case of an overwater incident, the boxes have an underwater acoustic locator beacon to aid in their recovery. According to the aircraft manufacturer (in this case Boeing), the beacon is capable of operation for approximately 30 days.

I have my own ideas as to what happened with this aircraft, but rather than add to all of the noise already out there, I figured that giving everyone an expanded view into what’s been going on, should help to clarify things.