Elm tower controller expressed concern regarding successive IFR spacing utilizing visual separation.

Attributes
ACN	642156
Time
Date	200412
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : elm.airport
State Reference	NY
Altitude	msl single value : 2600
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : elm.tracon tower : elm.tower
Operator	general aviation : personal
Make Model Name	Cessna 210 Centurion / Turbo Centurion 210C, 210D
Operating Under FAR Part	Part 91
Flight Phase	climbout : initial ground : maintenance
Route In Use	departure : on vectors
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : elm.tracon tower : elm.tower
Operator	general aviation : personal
Make Model Name	Skylane 182/RG Turbo Skylane/RG
Operating Under FAR Part	Part 91
Flight Phase	climbout : initial
Route In Use	departure : on vectors
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : local
Qualification	controller : radar
Experience	controller military : 5 controller radar : 1.5 controller supervisory : 1
ASRS Report	642156
Person 2
Affiliation	government : faa
Function	controller : departure
Events
Anomaly	conflict : airborne less severe
Independent Detector	atc equipment : conflict alert other controllera
Resolutory Action	controller : issued alert
Miss Distance	horizontal : 6000 vertical : 500
Supplementary
Problem Areas	ATC Human Performance
Primary Problem	ATC Human Performance

Narrative:

A C182 was first for departure, C210 was second. The aircraft were treated as the same type. The C182 was slower than anticipated on departure, and the C210 was much faster. While visual separation was used by the local controller and then diverging courses and no separation loss occurred, this situation was potentially dangerous. Controllers must take the possibility of similar aircraft reacting differently than anticipated because of weight (I believe the C182 was heavy, and the C210 light) and other factors. And giving the C210 a little extra room before clearing that aircraft for departure would have prevented this situation.

Original NASA ASRS Text

Title: ELM TWR CTLR EXPRESSED CONCERN REGARDING SUCCESSIVE IFR SPACING UTILIZING VISUAL SEPARATION.

Narrative: A C182 WAS FIRST FOR DEP, C210 WAS SECOND. THE ACFT WERE TREATED AS THE SAME TYPE. THE C182 WAS SLOWER THAN ANTICIPATED ON DEP, AND THE C210 WAS MUCH FASTER. WHILE VISUAL SEPARATION WAS USED BY THE LCL CTLR AND THEN DIVERGING COURSES AND NO SEPARATION LOSS OCCURRED, THIS SIT WAS POTENTIALLY DANGEROUS. CTLRS MUST TAKE THE POSSIBILITY OF SIMILAR ACFT REACTING DIFFERENTLY THAN ANTICIPATED BECAUSE OF WT (I BELIEVE THE C182 WAS HVY, AND THE C210 LIGHT) AND OTHER FACTORS. AND GIVING THE C210 A LITTLE EXTRA ROOM BEFORE CLRING THAT ACFT FOR DEP WOULD HAVE PREVENTED THIS SIT.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.