What are the most common uses of radio communication in aviation? I know that many aviators communicate with the people in towers with radio, but what do pilots say to the people in the towers and vice versa? What do pilots and ATCers communicate about.
It will be hard to list everything that is said, but I can try to start with some of the basic examples:
Pilot is ready to taxi to the Runway
P: Tower, N12345, has information Tango, at South Parking, ready to taxi.
T: N12345, taxi to runway 13 via Alpha, Delta.
Pilot is ready to take off
P: Tower, N12345, is ready to go at runway 13. Request SouthEast Departure
T: N12345, cleared for takeoff, SouthEast Departure approved.
Pilot wants to cross another airspace
P: Tower, N12345, is 10 miles to the East, 1,500, request transition east-to-west
T: N12345, transition approved as requested.
Pilot wants to approach an airport to land
P: Tower, N12345, is 10 miles to the South, 1,500. To Land
T: N12345, make Left-traffic for runway 17; report a 2 mile final
Radio communication is used to pass information aircraft to ground, ground to aircraft, aircraft to aircraft or whatever other direction you can imagine. This information could be anything relevant to the flight. For instance, when flying VFR at an uncontrolled airport it is expected that you announce your intentions while taking off or landing so that other pilots can anticipate what you will do and where you will be. Crossing areas with no radar coverage you use an HF radio to announce your position periodically because ground controllers cannot see you. This serves as a method to know you're still alive and allows for at least some level of separation from other aircraft. Other pilots can also hear these position reports so they know where you are.
When talking to controllers you could be discussing weather, vectors to a destination or geographic point or a number of other things. Sometimes it may not be relevant to the flight, such as asking the score during the World Series. Not exactly the purpose of aviation communication, but this sort of thing happens more than you would think. I've even done late night flights were I would be talking to another pilot heading in the same direction for hours just shooting the breeze. A couple of times controllers would participate.
These are just examples. The list could go on and on.
The most important use of aircraft radio is communication with air traffic control. You already know there is something called tower, but air traffic control is much more than that. With the exception of small private airfields and low level flights in remote areas, pilots are in contact with air traffic control from the moment they leave the gate/parking position, until the moment they park at their destination. Air traffic control decides which way the pilot must fly, how high and how fast. Of course, it is up to the pilot to let ATC know what they want to do, but the pilot is not allowed to simply do it.
Ever been in an airliner approaching an airport? During approach, the aircraft will make a series of turns, eventually ending up on the runway. Every time the aircraft makes a turn, that's ATC telling the pilots to do so. Every little turn, every change in altitude, every speed change - air traffic control instructions, submitted to the pilots by radio.
There are books written on air traffic control, and I think it is beyond the scope of this question to go into detail. I do encourage you to do some research on your own - including on this site. So to summarize the answer to your question: aircraft radios are used by pilots to communicate with air traffic control.
As a General Aviation (GA) practitioner and advocate (AOPA, Hooah!!), I must ensure that Unicom and Multicom communications are thoroughly explained.
Unlike air carrier crew members, GA pilots are required to take sole responsibility for maintaining safe separation distances and attitudes from other aircraft, making dynamic air traffic management command decisions in an array of high paced environments regarding flight procedures and operations, and the utilization of technologically advanced radio communicate and navigation systems to ensure safe and efficient operations through the air space they are utilizing.
Air carrier crew members are forbidden from engaging in these and many more operational procedures which require decision making capabilities which are independent from the strict, pre-planned, and thoroughly rehearsed guidance provided by air traffic controllers (ATC). These seemingly higher risk operations are only authorized to those pilots who have demonstrated a high level of skill and single pilot crew resource management skills. The vast majority of flights in the US operating in the uncontrolled realm do so under Visual Flight Rules (VFR). Here are the basics of communications in uncontrolled airfields and airspace:
Unicom frequencies are used at airfields or designated volumes of airspace (practice areas, scenic corridors, published transition corridors, etc.) which have no ATC services available. In the absence of a published Unicom frequency, piloted will use what's called the Multicom frequency, which in the US is 122.9 MHz, to make radio calls.
In either case, pilots decide unilaterally how and where they will maneuver their aircraft to accomplish what they are intending to do (practice maneuvers, land, take-off, etc.) In order to ensure all other pilots in the vicinity understand the position and intentions of their aircraft, a pilot will provide "self-announce" radio calls over the designated Unicom frequency (found on charts) when and where appropriate (as determined through training and experience).
When operating in airfield traffic patterns, this is generally done just prior to turning onto the subsequent traffic pattern leg (upwind, crosswind, downwind, base, and final). Pilots however may elect to modify this model based on Unicom frequency congestion and/or local area special procedures.
Pilots structure each individual radio transmission using the following protocol:
Intended Recipients -> Aircraft Type and Registration Number (shortened in most cases) -> Aircraft Position and/or Intent -> Runway (if applicable) -> Location of Intended Recipients
Probably doesn't make much sense, so here are some examples.
- In this scenario, we are in a Cirrus SR-20 with registration number N566GL (Totally made up, didn't check the FAA registry, so...yeah might be a 777 for all I know!), and we're parked at an airport in Northampton, MA (7B2). We're going to take one trip around the traffic pattern and land. Let's say we're doing a maintenance test flight, just for funnsies.
I'm not going to spell out what the aircraft is doing with each radio call, just what would be transmitted as some context notes in parentheses if applicable. If the call is answered, I'll put it in there for continuity. Take note of the slight structure variations in the first transmission, when the communication is directed at a specific recipient as opposed to transmissions meant for any aircraft in the vicinity. Also, the phonetic alphabet is used in all radio calls, which I spell out in the initial transmission. I shorten them to single letters for the rest of the transmissions for the sake of brevity. Here we go:
Northampton Unicom, Cirrus 6 GULF LIMA, Radio Check please.
-Cirrus 6GL, Northampton Unicom, radio check loud and clear (or 5 by 5, or something like 'Aircraft calling Northampton Unicom, you're broken and unreadable')
Northampton Unicom, Cirrus 6GL, I have you the same, thank you.
Northampton Traffic, Cirrus 6GL, Currently parked on the west apron, taxiing to Runway 14, Northampton. (Level of detail provided in ground movement Unicom radio calls will depend on local procedures)
Northampton Traffic, Cirrus 6GL, Taxiing onto runway 14 for departure, Northampton.
Northampton Traffic, Cirrus 6GL, Departing 14, Remaining closed traffic (staying in the traffic pattern) Northampton.
Northampton Traffic, Cirrus 6GL, turning cross-wind, 14 Northampton.
Northampton Traffic, Cirrus 6GL, turning downwind, 14 Northampton.
Northampton Traffic, Cirrus 6GL, midfield downwind, 14 Northampton (this is an additional call that may or may not be required based on conditions)
Northampton Traffic, Cirrus 6GL, turning base, 14 Northampton, Full Stop (as opposed to touch and go. Again, not something that is considered a requirement, but is often included by the pilot to assist other aircraft in the vicinity with situational awareness)
Northampton Traffic, Cirrus 6GL, turning final, 14 Northampton. Full Stop.
If needed, pilots can provide estimated distance to runway, especially if that distance would be considered non-standard for that particular airfield or runway. It would sound like this:
Northampton Traffic, Cirrus 6GL, turning half mile short final, 14 Northampton. Full Stop.
Northampton Traffic, Cirrus 6GL, back taxiing 14, Northampton.
Northampton Traffic, Cirrus 6GL, clear of 14, Northampton.
Northampton Traffic, Cirrus 6GL, taxiing from BRAVO taxi-way to west apron for parking, Northampton.
So there it is. Another situation would be announcing to ensure other pilots understand where in a designated practice area you'll be operating and what maneuvers you'll be conducting. These transmissions are often far less structured than traffic pattern radio calls.
- BRAVO Practice Area Traffic, Cirrus 6GL will be operating in quadrant 4 between 3,000 and 1,500 feet and will be conducting power on and power off stalls for approximately three zero minutes. Any traffic in the vicinity, please advise. GULF Practice Area.
Generally in these cases, an update call is made every 5-10 minutes while the pilot monitors the frequency for other aircraft position reports that may be a factor.
The last scenario I'll cover is when an aircraft is operating in a designated or published VFR corridor or area. There are a few of these in the US, however the 2 that I have flown in are the Hudson River Corridor in NYC and the "Mini Route" in the Los Angeles, CA area.
The Hudson River Corridor is, in my opinion one of the most unique and spectacular GA treasures found in the US today. I find the fact that it is even still open and used everyday by hundreds of fixed and rotary-wing GA aircraft, none of which are being controlled by ATC, absolutely amazing. Even after the tragic events of 9/11 and then the Cory Lidle accident, the Federal Aviation Administration (FAA), with full support of AOPA and EAA, did not bow to the alarmists who wanted to shut the corridor down to GA aircraft. Before I end my Kool-Aid driven motivational rant, I will say this: If you ever have the opportunity to fly this corridor, don't hesitate to take advantage of it. It is safe, it is structured, it is what GA flying is all about, and the experience is unbelievably surreal. If able, fly it at night as well. It is a completely unique experience in and of itself, and worth every second.
Ok, the other corridor, the LAX Mini Route, is another tool provided specifically for GA aircraft by the FAA. This route, one of a few in that region, allows GA traffic to safely and efficiently cross directly over the top of the Los Angeles International Airport (LAX), essentially bridging two large portions of the LA Basin. At one time, LAX and it's related operations were nothing less than an insurmountable brick wall for GA aircraft trying to get from one side you the other. To do so, GA aircraft were required to conduct an expensive, time consuming, and marginally safe circumnavigation of LAX airspace.
If it sounds like I am influenced by a favorable bias regarding the FAA, it's because I am. Yes, they can be a tremendous pain sometimes, but by-in-large, the rank and file employees which make up the FAA are dedicated civil servants whose goals are rooted in an effort focused on fostering the most safe, efficient, and advantageous use of the National Airspace System (NAS) by all users. Some are even bigger civil aviation dorks than we are...but I digress.
The radio calls in these VFR corridors are usually depicted on a chart or procedure plate, and often include position reports at certain predesignated positions. The Mini Route is slightly more complex, in that pilots are required to make position reports to various ATC facilities as well as Unicom radio calls as they progress through the route. The Hudson River Corridor is only Unicom calls, and I'm going totally from memory here (check your charts!), but they go something like this:
- Hudson River Traffic, Cirrus 6GL is southbound, abeam the Intrepid (aircraft carrier museum) at 900', will report Statue of Liberty next.
So that's my explanation of communications in uncontrolled airspace. Airline pilots, I love you guys, I was just busting your stones way up at the top of this. To be clear, airline pilots are a group of very skilled aviators which represent the true professional segment of the US pilot cadre. I was just being a PIA in the beginning!
Hope this helps!