There have been incidents where less than standard separation between aircraft occurred as a result of an aircraft’s non-standard climb/descent rate, non-activation of transponder equipment or incorrect beacon code selected on departure, and unexpected airspeed adjustments.  Particularly within New York Approach Control airspace, where there exists a continuous high volume of traffic in complex airspace, it is essential that information concerning aircraft performance is clearly communicated and those procedures for the operation of transponder equipment be closely followed.  In an effort to eliminate similar events, this Letter To Airmen (LTA), serves as a reminder to the aviation community of Aeronautical Information Manual (AIM) related paragraphs, which are used as a basis to separate aircraft by air traffic control personnel. 

When operating in New York Approach Control airspace: 

1.  Ensure that the correct assigned beacon code is selected and that the transponder is "ON/ALT" and operating normally. Pilots are cautioned not to depart on code "0000" as this code is assigned by ATC radar to invalid beacon replies (see Attachment #1).

2.  Advise the controller if you plan to climb or descend at other than the expected rate (see Attachment #2).

3.  Advise the controller when making speed adjustments in excess of + /-20 kts.

                                                                  ATTACHMENT #1 

 The Aeronautical Information Manual (AIM) states: 

 4-1-20. Transponder Operation

 a. General

 1.  Pilots should be aware that proper application of transponder operating procedures will provide both VFR and IFR aircraft with a higher degree of safety in the environment where high-speed closure rates are possible. Transponders substantially increase the capability of radar to see an aircraft and the Mode C feature enables the controller to quickly determine where potential traffic conflicts may exist. Even VFR pilots who are not in contact with ATC will be afforded greater protection from IFR aircraft and VFR aircraft that are receiving traffic advisories. Nevertheless, pilots should never relax their visual scanning vigilance for other aircraft. 

3.  Civil and military transponders  should be adjusted to the "on" or normal operating position as soon as practical and remain on during all operations unless requested to change to "standby'' from ATC ....

                                                                    ATTACHMENT #2

 4-4-10. Adherence to Clearance

 a. When ATC issues a clearance or instruction , pilots are expected to execute its provisions upon receipt.

 d. When ATC has not used the term "AT PILOTS DISCRETION" nor imposed any climb or descent restrictions, pilots should initiate climb or descent promptly on acknowledgement of the clearance. Descend or climb at an optimum rate consistent with the operating characteristics of the aircraft to 1,000 feet above or below the assigned altitude, and then attempt to descend or climb at a rate of between 500 and 1,500 fpm until the assigned altitude is reached. If at any time the pilot is unable to climb or descend at a rate of at least 500 feet a minute, advise ATC. If it is necessary to level off at an intermediate altitude during climb or descent, advise ATC, except when leveling off at 10,000 feet MSL on descent, or 2,500 feet above airport elevation (prior to entering a Class C, or Class D surface area). when required for speed reduction.

 REFERENCE-14 CFR Section 91.117.

 NOTE- Leveling off at 10,000 feet MSL on descent or 2,500 feet above airport elevation (prior to entering a  Class C, or Class D surface area) to comply with 14 CFR Section 91.117 airspeed restrictions is commonplace. Controllers anticipate this action and plan accordingly. Leveling off at any other time on climb or descent may seriously affect air traffic handling by ATC. Consequently, it is imperative that pilots make every effort to fulfill the above expected actions to aid A TC in safely handling and expediting traffic.

 EXAMPLE- "United Four Seventeen, descend and maintain six thousand." 

NOTE- The pilot is expected to commence descent upon receipt of the clearance and to descend at the suggested rates until reaching the assigned altitude of 6,000 feet.