Narrative:

Following radar vectors to the ILS runway 36 at dca, we were established on the localizer several mi south of the oxonn marker, descending to 2500 ft MSL. The GS was just becoming alive from above. We were solid IMC at the time. The aircraft was configured with 7 degrees flaps, on autoplt, and at 170 KTS assigned. We were advised that we were following a fokker 100, 3 mi ahead. We began to experience a slight amount of turbulence. Abruptly, the act (ce-650) rolled approximately 50 degrees to the right. My hand was on the control wheel. I immediately disconnected the autoplt and applied full left aileron and some rudder to counteract the roll. The aircraft responded, slowly at first, to the control input and then returned to level flight. I have flown numerous military and civilian transport category aircraft (currently also fly a gulfstream 4) and I have had several wake turbulence encounters over 30 yrs of flying. This was the worst encounter I have ever had. I am convinced that lack of a quick, appropriate, response would have resulted in inverted flight, in the WX, at 2500 ft AGL/MSL. Evidently the fokker was descending on the GS from a point further out than our point of intercept. As we approached the GS from below, we encountered the wake turbulence from the preceding fokker. 1) it appears that, at 3 mi in trail of a fokker 100, the wake turbulence is quite significant, especially for a citation sized aircraft, and that 3 mi separation may not be sufficient. 2) it also appears to be more prudent for a smaller aircraft landing at an air carrier airport to delay descent as much as practical so as to intercept the GS as far out (high) as possible to preclude flying under an air carrier aircraft descending on the GS. Callback conversation with reporter revealed the following: the reporter was flying a cessna citation III (ce- 650) and was following a fokker F-100 air carrier aircraft. The WX conditions were not too bad, and they anticipated that they would be sent on a circling approach to runway 33 after they broke out on their approach to runway 36. The F-100 was 3 mi ahead of them on a long straight in and his aircraft was turned in on a left base behind the F-100. His aircraft was descending to 2500 ft assigned as he turned towards final and intercepted the localizer. At 2700 ft in the descent there were a few little nibbles of turbulence and then a rapid roll to the right to about 50-60 degrees of bank. The reporter used full left aileron and some rudder during the roll, but it still progressed to that point and then normal flight resumed. By the time the reporter found himself in smooth air he was also on the GS so he then continued the approach staying 1 DOT high. Once the F-100 broke out the controller sent that aircraft to runway 33 and the reporter's aircraft continued to runway 36. The remainder of the approach was normal.

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Original NASA ASRS Text

Title: WAKE TURB -- THIS CORP CESSNA CE-650 ENCOUNTERED THE WAKE OF AN ACR FOKKER F-100 WHILE ON APCH TO RWY 36 AT DCA.

Narrative: FOLLOWING RADAR VECTORS TO THE ILS RWY 36 AT DCA, WE WERE ESTABLISHED ON THE LOC SEVERAL MI S OF THE OXONN MARKER, DSNDING TO 2500 FT MSL. THE GS WAS JUST BECOMING ALIVE FROM ABOVE. WE WERE SOLID IMC AT THE TIME. THE ACFT WAS CONFIGURED WITH 7 DEGS FLAPS, ON AUTOPLT, AND AT 170 KTS ASSIGNED. WE WERE ADVISED THAT WE WERE FOLLOWING A FOKKER 100, 3 MI AHEAD. WE BEGAN TO EXPERIENCE A SLIGHT AMOUNT OF TURB. ABRUPTLY, THE ACT (CE-650) ROLLED APPROX 50 DEGS TO THE R. MY HAND WAS ON THE CTL WHEEL. I IMMEDIATELY DISCONNECTED THE AUTOPLT AND APPLIED FULL L AILERON AND SOME RUDDER TO COUNTERACT THE ROLL. THE ACFT RESPONDED, SLOWLY AT FIRST, TO THE CTL INPUT AND THEN RETURNED TO LEVEL FLT. I HAVE FLOWN NUMEROUS MIL AND CIVILIAN TRANSPORT CATEGORY ACFT (CURRENTLY ALSO FLY A GULFSTREAM 4) AND I HAVE HAD SEVERAL WAKE TURB ENCOUNTERS OVER 30 YRS OF FLYING. THIS WAS THE WORST ENCOUNTER I HAVE EVER HAD. I AM CONVINCED THAT LACK OF A QUICK, APPROPRIATE, RESPONSE WOULD HAVE RESULTED IN INVERTED FLT, IN THE WX, AT 2500 FT AGL/MSL. EVIDENTLY THE FOKKER WAS DSNDING ON THE GS FROM A POINT FURTHER OUT THAN OUR POINT OF INTERCEPT. AS WE APCHED THE GS FROM BELOW, WE ENCOUNTERED THE WAKE TURB FROM THE PRECEDING FOKKER. 1) IT APPEARS THAT, AT 3 MI IN TRAIL OF A FOKKER 100, THE WAKE TURB IS QUITE SIGNIFICANT, ESPECIALLY FOR A CITATION SIZED ACFT, AND THAT 3 MI SEPARATION MAY NOT BE SUFFICIENT. 2) IT ALSO APPEARS TO BE MORE PRUDENT FOR A SMALLER ACFT LNDG AT AN ACR ARPT TO DELAY DSCNT AS MUCH AS PRACTICAL SO AS TO INTERCEPT THE GS AS FAR OUT (HIGH) AS POSSIBLE TO PRECLUDE FLYING UNDER AN ACR ACFT DSNDING ON THE GS. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: THE RPTR WAS FLYING A CESSNA CITATION III (CE- 650) AND WAS FOLLOWING A FOKKER F-100 ACR ACFT. THE WX CONDITIONS WERE NOT TOO BAD, AND THEY ANTICIPATED THAT THEY WOULD BE SENT ON A CIRCLING APCH TO RWY 33 AFTER THEY BROKE OUT ON THEIR APCH TO RWY 36. THE F-100 WAS 3 MI AHEAD OF THEM ON A LONG STRAIGHT IN AND HIS ACFT WAS TURNED IN ON A L BASE BEHIND THE F-100. HIS ACFT WAS DSNDING TO 2500 FT ASSIGNED AS HE TURNED TOWARDS FINAL AND INTERCEPTED THE LOC. AT 2700 FT IN THE DSCNT THERE WERE A FEW LITTLE NIBBLES OF TURB AND THEN A RAPID ROLL TO THE R TO ABOUT 50-60 DEGS OF BANK. THE RPTR USED FULL L AILERON AND SOME RUDDER DURING THE ROLL, BUT IT STILL PROGRESSED TO THAT POINT AND THEN NORMAL FLT RESUMED. BY THE TIME THE RPTR FOUND HIMSELF IN SMOOTH AIR HE WAS ALSO ON THE GS SO HE THEN CONTINUED THE APCH STAYING 1 DOT HIGH. ONCE THE F-100 BROKE OUT THE CTLR SENT THAT ACFT TO RWY 33 AND THE RPTR'S ACFT CONTINUED TO RWY 36. THE REMAINDER OF THE APCH WAS NORMAL.

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.