Narrative:

We were operating as flight xyz from lax to bos. We were sequenced by ground control to follow a B747-400. When tower gave the B747 their takeoff clearance, we started timing from the beginning of their takeoff roll. We were cleared into position and hold on runway 25R. After 50 seconds, the B747 became airborne. An E120 was cleared to cross the runway downfield. Immediately after the E120 cleared, we were given our takeoff clearance, that was 1 min 10 seconds after the B747 started their roll. We refused and told controller that we wanted 2 mins for wake turbulence avoidance. Controller was very upset at our refusal, saying that we did have standard wake turbulence separation of 5 NM (absolutely not -- the aircraft was only airborne for approximately 20-30 seconds!), and that we should have told him beforehand of our request for 2 mins separation. Why? With all the information on wake turbulence nowadays, shouldn't it be automatic to receive 5 NM and/or 2 mins separation? Controller made us taxi down on runway 25R and exit on taxiway F for resequencing (which we did). This sort of pilot pushing will one day result in a serious accident when a crew is not willing to take a delay and suffers the consequences of wake turbulence encounter at very low altitude.

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Original NASA ASRS Text

Title: AN A320 FLT IS TOLD TO CLR THE RWY AND BE RESEQUENCED FOR TKOF. THE CREW HAD REFUSED A TKOF CLRNC WITH LESS THAN 2 MINS AND LESS THAN 5 MI BEHIND A DEP B747-400 THAT HAD LIFTED OFF THE RWY JUST 30 SECONDS PRIOR TO TKOF CLRNC AT LAX, CA.

Narrative: WE WERE OPERATING AS FLT XYZ FROM LAX TO BOS. WE WERE SEQUENCED BY GND CTL TO FOLLOW A B747-400. WHEN TWR GAVE THE B747 THEIR TKOF CLRNC, WE STARTED TIMING FROM THE BEGINNING OF THEIR TKOF ROLL. WE WERE CLRED INTO POS AND HOLD ON RWY 25R. AFTER 50 SECONDS, THE B747 BECAME AIRBORNE. AN E120 WAS CLRED TO CROSS THE RWY DOWNFIELD. IMMEDIATELY AFTER THE E120 CLRED, WE WERE GIVEN OUR TKOF CLRNC, THAT WAS 1 MIN 10 SECONDS AFTER THE B747 STARTED THEIR ROLL. WE REFUSED AND TOLD CTLR THAT WE WANTED 2 MINS FOR WAKE TURB AVOIDANCE. CTLR WAS VERY UPSET AT OUR REFUSAL, SAYING THAT WE DID HAVE STANDARD WAKE TURB SEPARATION OF 5 NM (ABSOLUTELY NOT -- THE ACFT WAS ONLY AIRBORNE FOR APPROX 20-30 SECONDS!), AND THAT WE SHOULD HAVE TOLD HIM BEFOREHAND OF OUR REQUEST FOR 2 MINS SEPARATION. WHY? WITH ALL THE INFO ON WAKE TURB NOWADAYS, SHOULDN'T IT BE AUTOMATIC TO RECEIVE 5 NM AND/OR 2 MINS SEPARATION? CTLR MADE US TAXI DOWN ON RWY 25R AND EXIT ON TXWY F FOR RESEQUENCING (WHICH WE DID). THIS SORT OF PLT PUSHING WILL ONE DAY RESULT IN A SERIOUS ACCIDENT WHEN A CREW IS NOT WILLING TO TAKE A DELAY AND SUFFERS THE CONSEQUENCES OF WAKE TURB ENCOUNTER AT VERY LOW ALT.

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.