Narrative:

We were vectored across the final approach course twice and were asked for substantial speed changes. I believe this was to meet required spacing from jet traffic in front of us. While crossing the final approach course the second time, jet traffic was called to us by ATC and we maintain visibility contact. About the time we crossed the localizer a severe bang was heard and felt. Both pilot and copilot hit their heads very hard on the headliner and the aircraft momentarily lost stability. We both thought we had experienced a midair collision. After stabilizing the aircraft on the localizer, altitude was at 2200-2300' MSL at a point where a 3000' MSL was required. The aircraft had lost 800-900' during the unstable encounter and we were in the process of recovering. ATC was unaware of the situation, except for the altitude problem, which they called out to us. The 3000' MSL altitude was restored within 1 min or so. We believe now that the unstable operation was caused by wake turbulence from the jet ahead of us whose path we crossed on the second vector across the ILS. I believe that ATC could have warned us about the jet significantly sooner so that we could maintain a higher profile when crossing the ILS. I suspect our altitude assignment was proper in a normal circumstance, but by crossing the ILS so closely behind the jet, we were forced to receive the wake turbulence. By the time we were aware of the traffic, it was too late to request an altitude or heading change.

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Original NASA ASRS Text

Title: SMA LOSES CONTROL WHEN WAKE TURBULENCE IS ENCOUNTERED.

Narrative: WE WERE VECTORED ACROSS THE FINAL APCH COURSE TWICE AND WERE ASKED FOR SUBSTANTIAL SPD CHANGES. I BELIEVE THIS WAS TO MEET REQUIRED SPACING FROM JET TFC IN FRONT OF US. WHILE XING THE FINAL APCH COURSE THE SECOND TIME, JET TFC WAS CALLED TO US BY ATC AND WE MAINTAIN VIS CONTACT. ABOUT THE TIME WE CROSSED THE LOC A SEVERE BANG WAS HEARD AND FELT. BOTH PLT AND COPLT HIT THEIR HEADS VERY HARD ON THE HEADLINER AND THE ACFT MOMENTARILY LOST STABILITY. WE BOTH THOUGHT WE HAD EXPERIENCED A MIDAIR COLLISION. AFTER STABILIZING THE ACFT ON THE LOC, ALT WAS AT 2200-2300' MSL AT A POINT WHERE A 3000' MSL WAS REQUIRED. THE ACFT HAD LOST 800-900' DURING THE UNSTABLE ENCOUNTER AND WE WERE IN THE PROCESS OF RECOVERING. ATC WAS UNAWARE OF THE SITUATION, EXCEPT FOR THE ALT PROB, WHICH THEY CALLED OUT TO US. THE 3000' MSL ALT WAS RESTORED WITHIN 1 MIN OR SO. WE BELIEVE NOW THAT THE UNSTABLE OPERATION WAS CAUSED BY WAKE TURB FROM THE JET AHEAD OF US WHOSE PATH WE CROSSED ON THE SECOND VECTOR ACROSS THE ILS. I BELIEVE THAT ATC COULD HAVE WARNED US ABOUT THE JET SIGNIFICANTLY SOONER SO THAT WE COULD MAINTAIN A HIGHER PROFILE WHEN XING THE ILS. I SUSPECT OUR ALT ASSIGNMENT WAS PROPER IN A NORMAL CIRCUMSTANCE, BUT BY XING THE ILS SO CLOSELY BEHIND THE JET, WE WERE FORCED TO RECEIVE THE WAKE TURB. BY THE TIME WE WERE AWARE OF THE TFC, IT WAS TOO LATE TO REQUEST AN ALT OR HDG CHANGE.

Data retrieved from NASA's ASRS site as of August 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.