U.S. Department

of Transportation


Federal Aviation



Air Traffic


A Communication from the  

Vice President,
  System Operations Services


Issue # 2004-3

April 2004                                                                                             

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In this Issue:
Operational Priority for Air Carrier/Air Taxi Lifeguard Flights
Minimum Altitude Emergencies
Aircraft Call Sign Changes
Readback/Hearback, Again

Visual Separation Mistakes
Air Traffic Controller
Time to Climb
Aircraft Performance Characteristics
Back to the "C" in Controller
What is Awareness?

Operational Priority for Air Carrier/Air Taxi Lifeguard Flights

/*TER/ Civilian air ambulance flights responding to medical emergencies (carrying patients, organ donors, organs, etc.), including air carrier/air taxi aircraft using the "LIFEGUARD" call sign, will receive operational priority. Unlike civilian air ambulances, air carrier/air taxi aircraft are restricted from filing a flight plan using the letter "L" (indicator for Lifeguard) in conjunction with the aircraft's call sign.

This restriction is due to the limit of a combination of seven alpha/numeric characters allotted for the aircraft identity.

To indicate to air traffic control (ATC) that an air carrier/air taxi aircraft is actually a lifeguard flight and to facilitate priority handling, the word "Lifeguard" is included in the remarks section of the flight plan. This information should be reflected in the remarks section of the flight data/flight progress strip. It is important for the controller to be aware of all flight data and to ensure that this information is accurate and passed to the adjacent position/facility in a timely manner. It is important that this information is coordinated so that each controller may provide the necessary service and assistance.

When an air carrier/air taxi uses the term "Lifeguard" in conjunction with its call sign ("Lifeguard American Twenty Eight"), this is considered a request for operational priority, which should be granted. As indicated in FAAO 7110.65, Air Traffic Control, paragraph 2-1-4b, Note, "It is recognized that heavy traffic flow may affect the controller's ability to provide priority handling. However, without compromising safety, good judgement shall be used in each situation to facilitate the most expeditious movement of a lifeguard aircraft."  

Minimum Altitude Emergencies

/*TER/ Controlled flight into terrain (CFIT) accidents, departure accidents, and approach accidents sometimes occur even though the crew was always in complete control of the aircraft. These accidents and minimum altitude emergencies often stimulate heated discussions of who really was responsible for terrain and obstruction separation when the accident occurred.

Pilots always share responsibility for terrain and obstacle avoidance. A flightcrew should be generally aware of terrain and obstruction elevations and should never accept instructions that do not ensure adequate terrain clearance. A controller is required to issue a safety alert to an aircraft if the controller is aware the aircraft is in a position/attitude that, in his/her judgment, places the aircraft in unsafe proximity to terrain or obstructions. Air traffic controllers issuing specific altitude instructions and clearances accept responsibility for terrain avoidance.

Pilot charts depict minimum en route altitudes, minimum obstruction clearance altitudes, off route obstruction clearance altitudes, and other altitudes. Minimum vectoring altitudes, available only to ATC, can sometimes be the best and lowest altitudes available for instrument flight. Pilots receiving altitude assignments below charted altitudes typically assume they are being assigned the minimum vectoring altitude.

There should be no confusion as to whether ATC is assuming responsibility for terrain clearance. An aircraft needing emergency assistance or requesting an immediate instrument flight rules clearance may be in a position where ATC cannot immediately assume responsibility for terrain and obstruction clearance. In these cases, a controller can advise a pilot to provide his/her own terrain and obstruction clearance between the present altitude and the assigned altitude. This type of statement can be used when confusion might exist. 

Aircraft Call Sign Changes

/*TER/ It has been brought to our attention that aircraft call signs are being changed and may generate confusion and could impact safety. For instance, when an arriving aircraft is running late to its destination airport, using a specific flight number (AAL1882), and there is a proposed departure with the same call sign (continuation of AAL1882), the air carrier dispatch will change the call sign of the departure aircraft. In this example, the call sign of the departure aircraft will be changed to AAL882Q. This action is taken to eliminate the possibility of having two aircraft in the National Airspace System (NAS) with the same call sign.

In some instances, either the pilot or controller has initiated a request to revert to the original call sign. Initiating a change to a call sign by a controller or by a pilot who has not checked with his/her dispatcher may result in two aircraft in the NAS with the same call sign, and prevents the company from tracking the aircraft and handling it efficiently.

Due to an unauthorized call sign change, two aircraft with the same call sign did occur on the same local control frequency. A controller recognized what had occurred and corrected the situation, thereby avoiding compounding the error. The airline will brief its pilots on the proper procedure for requesting call sign changes. Controllers should not initiate call sign changes, but rather should do so when requested by the pilot. 

Readback/Hearback, Again

/*TERF/ It must be one of the most recurrent themes of the Air Traffic Bulletin system:  how to prevent readback/hearback errors. Over the years, this one issue has prompted numerous commentaries, observations, and suggestions, all attempting to reduce what may be the most preventable error of all, the missed readback. Why is it the most preventable? Because you possess an ability to prevent errors that few other people have. You have an ability to see the future. You have a one-time shot to look into your ATC crystal ball and see how things will turn out, and that crystal ball is called a readback. By using those readbacks effectively, you know what the pilot of that aircraft is going to do before he or she does it. How many other professionals get that chance?

We all know that errors occur for a variety of reasons and the last thing a controller wants is to have an error or serious incident. Twenty-eight percent of all errors occur when the controller is responsible for 5 or fewer aircraft, and 18 percent occur within the first 10 minutes after position relief. Therefore, we can have a tremendous impact on reducing operational errors by concentrating on these two areas. 

Here are a few examples of situations that led to operational errors:

·         An Aerostar was taxied to runway 35R via taxiway G and instructed to hold short of runway 35R at G. The pilot replied with "roger," and no readback of runway hold short instructions was requested.

·         A C550 was instructed to hold short of runway 13R at the departure end. The pilot acknowledged with the call sign only. Again, no request for the readback of runway hold short instructions.

·         A B752 landed on runway 4R and was instructed to hold short of runway 4L at taxiway F. Local control (LC) then asked the B752 what gate entry point he needed. The pilot replied, and the LC again instructed the aircraft to "hold short of runway 4L and remain this frequency." The pilot read back, "Crossing 4L, remain this frequency," and the LC missed it.

·         A DC9 was southeast bound climbing to FL290 while a CARJ was northwest bound at FL330 on a converging course. The controller intended to ask another aircraft on frequency to expedite its climb to FL350, however, used the call sign of the DC9.
The DC9 read back the clearance and began a climb into the CARJ.

·         A B735 was southwest bound and on a crossing course with a B733 at FL330.
The controller issued the B735 a clearance to FL330, realized it was a mistake, and amended the clearance to FL310. The B735 read back FL330, and the controller did not catch it.

·         A B757 was reported on frequency at FL350 and was told to expect a descent clearance in three minutes. The controller issued a descent clearance to another aircraft, however, the B757 read back the clearance, and the controller did not catch it.

How do we prevent these types of errors? By training and by practice. We must consciously work to improve our listening skills: improve them to the point where we hear every readback, every time. Tough task? Definitely. But we possess the skills and the training as professionals to make it work. FAAO 7110.65, Air Traffic Control, says that our primary purpose as controllers is to prevent a collision between aircraft, and our entire system is in place to help make that happen, but the final responsibility rests with each one of us in executing the simplest of tasks.

Always strive to listen to readbacks in their entirety. When you are busy, force yourself to hear the readback. We all cherish the ability to think two or three moves ahead, but the clearance is not complete until we hear the readback, and that is the reality. Also, we sometimes (very occasionally, of course) make mistakes, and the readback can be used to verify that a correct clearance was issued. Use standard phraseology too. Creative phraseology only boomerangs on us when we have to listen for key phrases and words mixed in with jargon or other nonstandard phraseology. The result may be that we do not take the time to listen.

The only way to break the back of these errors is through a conscious effort. Use that readback as your tool to see the future. Hear not what you want the pilot to do, but what the pilot is going to do.


Visual Separation Mistakes

For visual separation to work, the pilot has to see the correct aircraft and know beyond a doubt that he/she is to maintain visual separation from that same aircraft. Probably the most common mistake that is made with the visual separation technique is the controller failing to turn the separation responsibility over to the pilot correctly. The controller must unequivocally instruct the pilot to maintain visual separation after the pilot has affirmed that the traffic is in sight. However, if the pilot has already clearly stated that the traffic is in sight and that he/she will maintain separation, the agreement must be sealed by the controller stating, "Approved."

BE CAREFUL! Don't mistake a readback of your traffic instructions as an affirmation that the pilot sees the traffic! That's another silly mistake. (Reference FAAO 7110.65, Air Traffic Control, paragraph 7-2-1, Visual Separation.)

Air Traffic Controller 

Okay, that's the title. Some mistakes occur because the controller doesn't control the situation. For example, the controller will ask the pilot whether or not a particular action can be executed. "N1234 can you hold 300 knots in the climb?" If the pilot responds, "Affirmative," the controller ceases to be a controller IF he/she ASSUMES that the pilot will now decrease/increase the aircraft's airspeed to hold 300 knots, without being told to do it. Sometimes, the pilot will "control" the situation by assuming that the controller wants the 300 knots. Thus, in some cases, the pilot can assume correctly, but in all such cases, no positive control has been implemented and both pilot and controller are
at risk.

A pilot's certificate is on the line from the time he/she boards the aircraft until the flight is completed at the destination and the aircraft shut down. If the pilot assumes that the controller desires a certain action and acts upon that assumption without checking with the controller, or receiving a direct instruction to do so, the ability to keep that certificate can come into question. Aviation, like the sea, can be very unforgiving. Tell the pilot what you want done. If the pilot cannot comply with your request, it's the pilot's responsibility to tell you. Then you will have the correct information to enable you to continue controlling the situation. Don't give up control so easily!

Time to Climb

We still see controllers caught in separation losses where an aircraft that had been climbing/descending at a steady state reduced that rate to far less to level at its assigned altitude. Aircraft will generally maintain fairly steady state rates of climb or descent during altitude changes but, in all cases, that rate has to be altered roughly within 1,000 feet of the assigned altitude for the aircraft to level off and not overshoot the target altitude. Remember this small fact as you scan your traffic. Base your separation judgments on the expectation that the rate of climb/descent will change/slow as the aircraft approaches its assigned altitude.

Here we might offer another caution. If you always assume that the aircraft will slow, you might get unpleasantly surprised if the pilot keeps the climb going a bit longer before slowing up the aircraft.  So, be aware, and look and check what aircraft are doing. Don't let assumptions put you into a box!

The wise controller will check for variations in the aircraft's rate of climb during the climb, especially above FL290. Temperature inversions and differences can markedly affect an aircraft's rate of climb, sometimes reducing it to less than 100 feet per minute! The pilot has no control over the aircraft's performance in these situations. If you are not paying attention, this seemingly sudden reduction in aircraft performance can cause you a lot of grief.

Know Your Aircraft Performance Characteristics

Which aircraft has the better climb performance? A Falcon 50 or a Boeing 767? Okay, which aircraft has the widest range of performance, a PA-28 or a Learjet or a Beech 18?

You should know the answers to those questions. If you don't, then you are vulnerable to a mistake that catches some controllers. If you don't know what the performance ability or characteristics of an aircraft are and a choice must be made on continuing or initiating a climb or descent clearance between aircraft, and you choose the wrong one, you may have set yourself up for a loss of separation. In several errors, the controller expected the Falcon to outperform the Boeing, or the Learjet to perform in the lower range of its capabilities.

The appendix of FAAO 7110.65, Air Traffic Control, provides aircraft information that can help you make educated decisions. Know what the range of performance is. Consider vertical speed and how that relates to rate of distance made across the ground.

The Learjet is capable of climbing 6,000+ feet per minute. High climb rates generally translate into huge vertical distance covered but much less lateral distance traveled than when the aircraft is climbing at a more average or sedate vertical rate. Here is something to consider: aircraft can be climbed at best rate or best angle of climb, but not both simultaneously. Best angle of climb will result in the greatest gain in altitude for a given distance over the ground, and best rate of climb will result in the greatest gain in altitude per unit of time. By following the guidelines of FAAO 7110.65, Air Traffic Control, paragraph 4-5-7b, you will automatically receive the best rate of climb from the pilot. We have to wonder when we hear someone ask a pilot, "Give me your best rate" what really is that controller expecting or trying to ask?

Back to the "C" in Controller ...

We still see mistakes made where the controller abandons the title, "ATCS " and becomes an "ATHS" (Air Traffic Control Specialist to Air Traffic Hopeitworks Specialist). This is a syndrome where the controller ceases using positive control techniques and procedures. Instead, the controller begins asking hopeful, hinting questions, but doesn't control the situation. The most common example is where the aircraft has been issued a climb clearance. The controller asks the pilot, "Are you level yet?" and then, "Say altitude," and then, "I need you level in 30 seconds" and then, well, you get the picture.

Positive control actions would be to stop or turn the other aircraft that may be a conflict, or stop or turn the climbing aircraft. Obviously, these actions must be done before the situation gets into an impossible posture.

Part of positive control is this:  issue control instructions (not questions, hints, comments), assess their effect, adjust as necessary. Once a pilot has been given a job to do, your obligation is to check back to see that things are proceeding as you intended. You must do this as frequently and or rapidly as the situation requires for you to maintain control.

Maintaining control means that you adjust the situation as needed to keep the system moving safely and efficiently. If you allow yourself to get distracted unnecessarily, or to spend too much time in one area without checking on the other, you will be setting yourself up to lose control of the situation. You must be able to shift your attention rapidly, yet maintain an awareness of what is going on around you. You cannot focus exclusively on any one situation. When this is allowed to occur, you lose the big picture because you have shut out information for the time you were singularly focused on the one thing.

Huh?  What is Awareness?

In a situation where a pilot calls, the voice/phone line calls/rings, and a fellow controller is in your ear asking for coordination while you are entering an amendment into the computer, true awareness is that you know that a pilot called, the center/TRACON/AFSS called, and another controller needs your attention. You alone must decide in what order to respond to each of these demands, but the point is that you are aware of each of them. Some people focus to such an extent that they are "deaf" to certain calls. When this occurs, the person is said to have "lost awareness."

Keep them flying…. keep them safe!

Questions/comments about content should be addressed to ATP-100