INTERROGATOR- The ground-based surveillance radar beacon transmitter-receiver, which normally scans in synchronism with a primary radar, transmitting discrete radio signals which repetitious- ly request all transponders on the mode being used to reply. The replies received are mixed with the primary radar returns and displayed on the same plan position indicator (radar scope). Also, applied to the airborne element of the TACAN/DME system. 

(See TRANSPONDER.) (Refer to AIM.) 

INTERSECTING RUNWAYS- Two or more runways which cross or meet within their lengths. 

(See INTERSECTION.) 

## INTERSECTION- 

a. A point defined by any combination of courses, radials, or bearings of two or more navigational aids. 

b. Used to describe the point where two runways, a runway and a taxiway, or two taxiways cross or meet. 

INTERSECTION DEPARTURE- A departure from any runway intersection except the end of the runway. 

(See INTERSECTION.) 

INTERSECTION TAKEOFF- (See INTERSECTION DEPARTURE.) 

IR- (See IFR MILITARY TRAINING ROUTES.) 

IRREGULAR SURFACE- A surface that is open for use but not per regulations. 

ISR- (See INCREASED SEPARATION REQUIRED.) 

