ASRS Directline

 Issue Number 7 : September 1995

See the sidebar article: "Come Out With Your Hands Up!"

Say What?! Non-Standard Phraseology Incidents

by Robert Matchette

Aviation has enjoyed numerous advances in aerodynamics, power plant efficiency and reliability, flightdeck automation, and navigation systems. However, ATC/aircraft communications have changed little over the years, and still exhibit the age-old limitations of natural and human-made interference that can distort messages, difficulties with language barriers, and the problems of pronunciation and phraseology. At the same time, the volume of ground-to-air (ATC/aircraft) communication has increased dramatically because of the remarkable increase in air traffic. Satellite links and discrete communication technology promise communications solutions for the future--until then, aviation is forced to deal with the communications status quo. One of the greatest problems inherent in voice communications today is the use of non-standard phraseology.

The ASRS database was searched for records which made reference to phraseology in their narratives, and 260 reports were reviewed. Many reported incidents resulted in little more than momentary confusion or annoyance for pilots and controllers. However, nearly half the reports involved near mid-air collisions, loss of standard ATC separation, runway transgressions, or other conflicts with potentially serious safety consequences.

Phraseology 101

Examples of non-standard phraseology occur during all flight phases. What follows are examples of common non-standard phraseology used in each phase of flight (which may or may not have had potentially serious consequences), and suggested alternate wording which may have prevented the incident.


Watch out, you may get what you ask for!

Conventional wisdom (and the AIM) dictate the use of a less provocative phrase: "ABC Clearance, company ident, I-F-R St. Louis." Although the AIM does not suggest advising Clearance Delivery that you have the current ATIS, individual locations may request that information, as well as the gate number when applicable.


You have to push prior to taxi...right?

After a pilot receives an IFR clearance, the next interaction with ATC is often a pushback request. What may be construed as authorization by some may not be by others.

At many large airports, some gates may be controlled by ATC, while others, out of direct sight of controllers, may be under the control of the air carrier--aircraft movements in this case will be governed by the letter of agreement between the carrier and ATC. It is not clear, in this instance, who had jurisdiction for this gate area. If this gate was ATC-controlled, the controller should have said "Hold" or "Pushback approved." If the gate was the carrier's responsibility, the flight crew erred in entering the taxiway during pushback. In any event, the message here is clear--controllers need to provide clear instructions and messages, and pilots need to ask for clarification if there is any confusion or opportunity for misinterpretation.

Taxi Out

To get there, I have to cross...

Although the reporter certainly did not a have a specific clearance to cross the runway, the Controller contributed to the incident. A less ambiguous clearance would have been, "Aircraft ident, plan to conduct runup on east side of Runway 23, hold short of Runway 23." After an aircraft gets to a runway (assuming that it was the one intended), the pilot's awareness is often heightened, and the probability of a misunderstanding should be reduced...right?

Into Position

No, your other right

The reporter could have prevented any misunderstanding by informing the controller prior to reaching the runway that full length would be required for takeoff. In many situations, pilots and controllers giving each other as much advance information as possible will reduce the likelihood of miscommunication. In this case, the phraseology in question occurred at a busy time for the flight crew. Unfortunately, last-minute changes often occur at the highest workload phases of flight. In these situations, a sense of urgency can often cause pilots and controllers to neglect to clarify misconceptions as they might have done if there were no apparent time constraints. Schedule pressure plus a complex clearance can equal instructions in non-standard phraseology, as the next reporter discovered.

Takeoff/Initial Climb

When do we turn?

A query directed to the Tower could have alleviated any misunderstanding, which in this case resulted in less than standard separation from another departing aircraft. The possibility for confusion abounds when specific numerical values are assigned as headings, airspeeds or altitudes. At times, the importance of standard phraseology can become critical, as the following report illustrates:


230 what?

According to the AIM, when controllers issue a speed restriction, they are to use the word "speed" or "knots" in the clearance. However, once again, the flight crew could have asked for clarification before this altitude deviation took place.


Cruise flight is often the time when flight crews can relax, since there is usually little cockpit activity compared to other phases of flight. This lack of activity can inspire flight crews to let down their guard and disregard things they might notice if they were more focused on specific tasks. Non-standard phraseology contributed to this incident in which a Controller attempted to verify a flight's altitude after a hand-off.

Roger what?

AIM defines the term "Roger" as, "I have received all of your last transmission," and states that it "should not be used to answer a question requiring a yes or no answer." However, the term is constantly misused in communications, often resulting in misunderstanding, annoyance, or more serious consequences for both pilots and controllers.


Roger this...
Roger that...

When pilots realize that an ATC clearance cannot be complied with, they are required to advise ATC as soon as possible. Timely notification is critical to prevent problems which could compromise separation from other traffic. Once pilots have advised ATC that a restriction cannot be made, they are often very anxious for a Controller's response either to relieve them of responsibility or to assign a new restriction. Roger is not the only response that offers little in the way of an answer, as the next report illustrates.

Approach and Landing

In an effort to keep each other well-informed, controllers and pilots might supply information that is out of the ordinary in order avoid potential problems or to help clear up any questions that might arise. Sometimes, these out-of-the-ordinary advisories can create more confusion or consternation than they were intended to alleviate. Consider this next report:

What are all those fire trucks doing?

After the Avianca Airlines accident on Long Island, NY, ATC sensitivity about fuel exhaustion was justifiably heightened. (See "Great Expectations" by Jeanne McElhatton, an excellent article in Issue # 3 of ASRS Directline about minimum fuel situations.) The flight crew might have alleviated this Controller's concerns by accurately conveying their situation. They could have said, for instance, "...we would like to be on the ground in about 10 minutes--just so we don't get too far into our fuel reserves."

Landing and Rollout

Once a successful approach and landing are accomplished, pilots tend to relax a little bit. The challenge, danger, and possibility of error are dramatically reduced, right?

When arrivals to an airport are tightly spaced and aircraft are in position for departure, communications can get especially hectic. Controllers often try to assist a pilot by giving what they think are simple, direct instructions. Although the intentions are good, identifying the specific taxiway designation in the instruction would help minimize misunderstanding. Pilots can assist the controller by advising ATC as soon as possible of any known restrictions on where they can turn off the runway.

Taxi In

If you're not sure, ask...

As in many cases, without reviewing the ATC tapes, no one will ever know whose account of this incident is correct. However, unless it is absolutely clear that a taxi clearance includes a crossing clearance, a confirmation of the clearance as well as a visual check of the runway must occur to prevent this kind of incident.

The Human Factor

So where is the problem?

Problems with communications technique are evident on both sides of the radio link. Although controllers are mandated to adhere to standard phraseology, there are certainly examples of controllers using non-standard phrases. Pilots are required by regulation to read back certain phases of a clearance, but are given, and often exercise, more latitude in phraseology than their controller counterparts. In the final analysis, human factors issues, such as loss of situational awareness, readback/hearback, anticipatory problems, response to schedule pressure, etc., affect controllers and pilots alike. Following are some typical examples of flawed communications technique with which most pilots can identify.

Too Casual

In the following report, the pilot's phraseology is too casual for the task at hand:

Sentence Construction

Even when the proper words are uttered over the frequency, the inflection or cadence used can significantly change the meaning.

Fatigue and CRM

A high-workload phase of flight, frequency congestion, heavy traffic, and fatigue sometimes combine with less than optimum cockpit resource management to push pilots and controllers to their limits. When non-standard phraseology enters the picture, things can quickly fall apart as they did in this airborne conflict near Denver.

Say it Again, Sam

Say What?!It should be evident to anyone listening to an ATC frequency that non-standard phraseology is common. Whether it is a significant factor in aviation incidents is open to discussion. The reports reviewed here are but a fraction of those in the ASRS database. Regardless of the magnitude of the problem, there certainly are ways to help avoid these problems in the first place, or to minimize their effect on day-to-day operations.

  1. If a clearance or instruction seems the least bit out of the ordinary or ambiguous, flight crews should not hesitate to clarify the clearance or instruction until no doubt remains.

  2. Pilots and controllers should make a conscious effort to use standard phraseology in all ATC communications. In addition, inflection and the placement of pauses in a transmission may be significant.

  3. A recurrent training session is the perfect venue for pilots to review the AIM and other pertinent resources discussing standard phraseology.

  4. Before the first trip as a flight crew, the Captain should take the initiative to discuss phraseology issues as they pertain to inter-crew as well as ATC communications. This may help to prevent misunderstandings among the crew, and to heighten alertness for non-standard phraseology used by ATC. It is equally important for flight instructors to discuss these issues with their students, since frequent intra-cockpit communications take place during instructional sessions.

Come Out With Your Hands Up!

The Pilot-Controller Glossary defines squawk as "activate specific mode/code/function on the aircraft transponder." Therefore, "squawk your altitude" is a controller's instruction to activate the altitude function of a Mode 3/A transponder.

Squawking 7500 is the international code to indicate a hijacking. The AIM instructs pilots of hijacked aircraft to set 7500 into the aircraft transponder, which triggers a flashing "HIJK" in the aircraft's data block on the Controller's radar screen. The Controller will then ask the pilot to "verify squawking 7500." If the pilot verifies the code or makes no response at all, the Controller will not ask further questions, but will continue to flight-follow, respond to pilot requests, and notify appropriate authorities. These procedures are exactly the ones that occurred, as this reporter can testify:

This poor pilot forgot to review his AIM, which would have informed him that:

"Code 7500 will never be assigned by ATC without prior notification from the pilot that his aircraft is being subjected to unlawful interference [hijacking]. The pilot should refuse the assignment of Code 7500 in any other situation and inform the controller accordingly."

In fact, ATC will not assign any transponder codes beginning with 75, 76, or 77 for anything other than what they are meant for. Code 7512, or 7622, or 7752, for example, will not be assigned because the first two numbers trigger the computer--the last two digits make no difference.

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