12/2/21 

Pilot/Controller Glossary 

SIMULTANEOUS (CONVERGING) INDEPEND-
ENT APPROACHES- An approach operation 
permitting ILS/RNAV/GLS approaches to non-par-
allel runways where approach procedure design 
maintains the required aircraft spacing throughout 
the approach and missed approach and hence the 
operations may be conducted independently. 

SIMULTANEOUS ILS APPROACHES

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 An 

approach system permitting simultaneous ILS 
approaches to airports having parallel runways 
separated by at least 4,300 feet between centerlines. 
Integral parts of a total system are ILS, radar, 
communications, ATC procedures, and appropriate 
airborne equipment. 

(See PARALLEL RUNWAYS.) 
(Refer to AIM.) 

SIMULTANEOUS OFFSET INSTRUMENT 
APPROACH (SOIA)

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 An instrument landing 

system comprised of an ILS PRM, RNAV PRM or 
GLS PRM approach to one runway and an offset 
LDA PRM with glideslope or an RNAV  PRM or 
GLS PRM approach utilizing vertical guidance to 
another where parallel runway spaced less than 3,000 
feet and at least 750 feet apart. The approach courses 
converge by 2.5 to 3 degrees. Simultaneous close 
parallel PRM approach procedures apply up to the 
point where the approach course separation becomes 
3,000 feet, at the offset MAP. From the offset MAP 
to the runway threshold, visual separation by the 
aircraft conducting the offset approach is utilized. 

(Refer to AIM) 

SIMULTANEOUS (PARALLEL) DEPENDENT 
APPROACHES- An approach operation permitting 
ILS/RNAV/GLS approaches to adjacent parallel 
runways where prescribed diagonal spacing must be 
maintained.  Aircraft are not permitted to pass each 
other during simultaneous dependent operations. 
Integral parts of a total system ATC procedures, and 
appropriate airborne and ground based equipment. 

SINGLE DIRECTION ROUTES

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 Preferred IFR 

Routes which are sometimes depicted on high 
altitude en route charts and which are normally flown 
in one direction only. 

(See PREFERRED IFR ROUTES.) 
(Refer to CHART SUPPLEMENT U.S.) 

SINGLE FREQUENCY APPROACH

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 A service 

provided under a letter of agreement to military 
single-piloted turbojet aircraft which permits use of 

a single UHF frequency during approach for landing. 
Pilots will not normally be required to change 
frequency from the beginning of the approach to 
touchdown except that pilots conducting an en route 
descent are required to change frequency when 
control is transferred from the air route traffic control 
center to the terminal facility. The abbreviation 
“SFA” in the DOD FLIP IFR Supplement under 
“Communications” indicates this service is available 
at an aerodrome. 

SINGLE-PILOTED AIRCRAFT

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 A military 

turbojet aircraft possessing one set of flight controls, 
tandem cockpits, or two sets of flight controls but 
operated by one pilot is considered single-piloted by 
ATC when determining the appropriate air traffic 
service to be applied. 

(See SINGLE FREQUENCY APPROACH.) 

SKYSPOTTER

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 A pilot who has received 

specialized training in observing and reporting 
inflight weather phenomena. 

SLASH

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 A radar beacon reply displayed as an 

elongated target. 

SLDI

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(See SECTOR LIST DROP INTERVAL.) 

SLOW TAXI

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 To taxi a float plane at low power or 

low RPM. 

SMALL UNMANNED AIRCRAFT SYSTEM 
(sUAS)– An unmanned aircraft weighing less than 55 
pounds on takeoff, including everything that is on 
board or otherwise attached to the aircraft. 

SN

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(See SYSTEM STRATEGIC NAVIGATION.) 

SPACE

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BASED ADS

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B (SBA)

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 A constellation of 

satellites that receives ADS

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B Out broadcasts and 

relays that information to the appropriate surveil-
lance facility. The currently deployed SBA system is 
only capable of receiving broadcasts from 1090ES

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equipped aircraft, and not from those equipped with 
only a universal access transceiver (UAT). Also, 
aircraft with a top

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of

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fuselage

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mounted transponder 

antenna (required for TCAS II installations) will be 
better received by SBA, especially at latitudes below 
45 degrees. 

(See AUTOMATIC DEPENDENT 

SURVEILLANCE

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BROADCAST.) 

(See AUTOMATIC DEPENDENT 

SURVEILLANCE

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BROADCAST OUT.) 

SPACE LAUNCH AND REENTRY AREA

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Locations where commercial space launch and/or 

PCG S

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