Citation Excel (C560XL)
Air Traffic Control Fully Certified
Other / Unknown
ATC Issue All Types; Inflight Event / Encounter Wake Vortex Encounter
General None Reported / Taken
Procedure
Working South Local (land 28C depart 22L) west flow (new runway and configuration since Oct 2013); I had numerous Heavy cargo jets landing 28C. A B747 had just passed over Runway 22L; I cleared an EMB135 for takeoff. We have been told that departing 22L we do not need to worry about the wake turbulence from heavy arrivals to 28C; because aircraft will just not rotate prior to or at the point of wake turbulence. I gave clearance to the Citation Excel (ORD departure arriving MDW) to line up and wait. I asked the Citation what was his planned rotation point due to the fact that a Heavy Jet had just landed Runway 28C; his response was 5;000 foot mark; I cleared the Citation for takeoff; and the Citation delayed his departure roll; my best guess is 30 to 45 seconds. I observed the Citation airborne maybe 15-25 FT at Y4 (Y4 is just past the intersection of Runway 28C center line and Runway 22L). I reported a possible wake turbulence error immediately. The amount of time to the wake turbulence may have been 2 minutes. The problem that I see is we have been told that 'Wake turbulence at this intersection is not an issue'; aircraft will rotate past the point of this intersection. And I have no guarantees that any aircraft will not rotate prior to this intersection. My thought was to ask the pilot where his planned rotation point would be and if that gave me a reasonable assurance that wake turbulence was no factor then I would proceed as instructed by the designers of this operation. I was aware of the fact that it is approximately 2;900 FT to this intersection; and have seen many aircraft rotate in less distance; commercial and private Aircraft. I once worked a B747 that rotated in less than 2;500 FT and was at 5;000 FT 2 miles west of the field. I have seen B757s on test flights do the same. Recommendation; I am not sure with all the planning that has gone into this new runway configuration there is not a good remedy for this; other than waiting the required 2 minutes for 22L departures that may rotate prior to this intersection.
ORD Controller voiced concern regarding a facility policy that indicates 'Wake Turbulence' is not a factor during the west flow operation because of expected rotation locations.