Narrative:

While waiting to take off from runway 04L in ewr; the captain and I noticed that we were directly behind a 757. We both talked about having had wake turbulence upsets (from which we'd recovered; but were still unexpected and potentially dangerous) behind 757s in the past after receiving takeoff clearances with minimum separation; and agreed that we would ask for some extra time if ATC tried to have us takeoff too soon after the 757. I started a timer when the 757 started its roll (before lining up on runway 4L as directed); and sure enough; 56 seconds later; we were cleared for takeoff. We asked for extra time for wake turbulence separation; so tower cancelled our takeoff clearance. We called back after two minutes after the departure of the 757; and; after an aircraft crossed the runway downfield; tower then granted our clearance. After takeoff; tower suggested that we ask for extra time sooner; as he would have to fill out paperwork for the rejected clearance.the major threat is unusual attitudes resulting from being in the wake of a near-heavy aircraft. Because we waited to take off; we did not experience this unusual attitude scenario today. From a safety perspective; I think we made the best choice for the situation. From a procedures perspective; we could have asked tower for extra spacing when we were first told to line up on the runway; instead of after getting the takeoff clearance. We suspected tower might clear us more quickly than we'd like; but we did not know for sure; and we didn't know this would cause them any hassle.if wake turbulence separation seems insufficient; in the future; I could ask for extra spacing earlier; before getting the takeoff clearance - while receiving the line up and wait clearance seems ideal. However; based on my prior experience of an upset behind a 757; I think we made the right call; and it might behoove the company or even the FAA to increase spacing minimums between near-heavies and trailing rjs.

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Original NASA ASRS Text

Title: EMB-145 First Officer reported that requesting additional wait time prior to departure behind a B757 resulted in a canceled takeoff clearance.

Narrative: While waiting to take off from Runway 04L in EWR; the Captain and I noticed that we were directly behind a 757. We both talked about having had wake turbulence upsets (from which we'd recovered; but were still unexpected and potentially dangerous) behind 757s in the past after receiving takeoff clearances with minimum separation; and agreed that we would ask for some extra time if ATC tried to have us takeoff too soon after the 757. I started a timer when the 757 started its roll (before lining up on Runway 4L as directed); and sure enough; 56 seconds later; we were cleared for takeoff. We asked for extra time for wake turbulence separation; so Tower cancelled our takeoff clearance. We called back after two minutes after the departure of the 757; and; after an aircraft crossed the runway downfield; Tower then granted our clearance. After takeoff; Tower suggested that we ask for extra time sooner; as he would have to fill out paperwork for the rejected clearance.The major threat is unusual attitudes resulting from being in the wake of a near-heavy aircraft. Because we waited to take off; we did not experience this Unusual Attitude Scenario today. From a safety perspective; I think we made the best choice for the situation. From a procedures perspective; we could have asked Tower for extra spacing when we were first told to line up on the runway; instead of after getting the takeoff clearance. We suspected Tower might clear us more quickly than we'd like; but we did not know for sure; and we didn't know this would cause them any hassle.If wake turbulence separation seems insufficient; in the future; I could ask for extra spacing earlier; before getting the takeoff clearance - while receiving the line up and wait clearance seems ideal. However; based on my prior experience of an upset behind a 757; I think we made the right call; and it might behoove the company or even the FAA to increase spacing minimums between near-heavies and trailing RJs.

Data retrieved from NASA's ASRS site 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.