Learning Resources
Lesson
Communication inside and outside of the cockpit is an integral part of a safe and successful flight. The cockpit crew have to communicate with each other and the ground crew as well as apron and ATC personnel. They must monitor the instruments of their aircraft, and make split-second decisions based upon this transfer of information. The importance of clear communication should be evident from the steps needed just to get off the ground in the last lesson. This communication has to be concise. The messages and information given by the instruments have to be pertinent and definite. Mixed signals given to the crew, especially in light of the volumes of information that they receive every minute, could create severe problems before and during a flight.
The radio stack plays a major role in communication in any aircraft, in particular the COM radio. It has three primary responsibilities:
- Allow communication between the cockpit crew and anyone responsible for the departure, flight and arrival of the aircraft. ATC, Ground, arrival, and departure control all have a special frequency through which they communicate with the crew.
- Flight Service Stations can be contacted in the event of emergency, for airport advisory services in the event that the airport is not controlled by a tower, and to distribute NOTAM information.
- ATIS provides weather and other information over a frequency defined by the airport location.
The communications radio has a specific set of frequencies that define who the cockpit crew can communicate with at any given time. The frequencies are located in the 118.000 MHz to 135.975 MHz range and are specified in a manual that is provided to pilots by Transport Canada for Canadian airspace and the FAA for American airspace. These are set in increments of 25 KHz on the COM (top) portion of the radio stack. The numbers are dialed on a real communications radio using a button which increments or decrements the frequency value. We will use a mouse or the communication menu located under Aircraft on the menu bar, to dial our radio frequencies.
The chart below is a sample of the Air Pilot Instrument Procedures (A.I.P) for St. John's, This sheet, also known as a "plate" provides all of the information necessary for a crew to find and land a plane in a location. Of interest to us is the information provided at the top of the page. There are five areas, four of which contain radio frequencies. The first is the ATIS frequency that can be dialled into the COM radio. This will give the weather information and current parameters for runway usage at the airport. The second box contains two frequencies which correspond to the arrival and departure frequencies to be used at the airport. The last is the tower frequency which is used to contact ATC for clearance to land or take off. There are other sections which give elevation and other information related to holding patterns, ILS (Instrument Landing Systems), approach and beacon information which is used for navigation.
To an untrained eye, the plate is a jumble of unintelligible jargon but to an experienced flier, a wealth of information is available at a glance.
The radio information is broadcast at frequencies in the VHF or Very High Frequency Range between 1 to 10 m wavelength. Since VHF frequencies do not have characteristics which allow them to bounce off the ionosphere; They do not follow the curvature of the earth, they are considered to be line of sight or los frequencies. The higher the altitude the farther away a signal can be heard. This property lends itself well to use in airline transmission as many planes fly at reasonably high altitudes. These frequencies are also relatively static free since they are not overly susceptible to atmospheric static. The signals also require less power to run.