A CE550 was allowed to descend 15 NM behind an MD11 at FL240 and encountered severe wake turbulence.

Attributes
ACN	732545
Time
Date	200703
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : opf.airport
State Reference	FL
Altitude	msl single value : 24000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zma.artcc
Operator	general aviation : corporate
Make Model Name	Citation II S2/Bravo
Operating Under FAR Part	Part 91
Flight Phase	descent : intermediate altitude
Route In Use	arrival star : fisel
Flight Plan	IFR
Aircraft 2
Controlling Facilities	artcc : zma.artcc
Operator	common carrier : air carrier
Make Model Name	MD-11
Operating Under FAR Part	Part 121
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : atp pilot : commercial
Experience	flight time last 90 days : 75 flight time total : 6500 flight time type : 500
ASRS Report	732545
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	inflight encounter : wake turbulence
Independent Detector	other flight crewa other flight crewb
Resolutory Action	none taken : detected after the fact
Supplementary
Problem Areas	Environmental Factor ATC Human Performance Aircraft
Primary Problem	Ambiguous

Narrative:

Miami ARTCC tends to keep slower aircraft at a higher altitude and allow faster aircraft to pass underneath ignoring the usual crossing altitudes and descent profiles. On 3/wed/2007 at about XA00 local time; while being vectored on the FISEL2 arrival ATC was asking most all aircraft to change their descent rates and crossing altitudes. This happens a lot when ATC gets busy. They vectored a heavy md-11 underneath us and then descended us below the md-11. Even though we were about 15 miles behind the md-11 we hit severe wake turbulence; no one was hurt as all passenger were buckled in. If ATC allows aircraft to fly the arrival as published this situation would be better.

Original NASA ASRS Text

Title: A CE550 WAS ALLOWED TO DESCEND 15 NM BEHIND AN MD11 AT FL240 AND ENCOUNTERED SEVERE WAKE TURB.

Narrative: MIAMI ARTCC TENDS TO KEEP SLOWER ACFT AT A HIGHER ALTITUDE AND ALLOW FASTER ACFT TO PASS UNDERNEATH IGNORING THE USUAL CROSSING ALTITUDES AND DESCENT PROFILES. ON 3/WED/2007 AT ABOUT XA00 LOCAL TIME; WHILE BEING VECTORED ON THE FISEL2 ARR ATC WAS ASKING MOST ALL ACFT TO CHANGE THEIR DESCENT RATES AND CROSSING ALTITUDES. THIS HAPPENS A LOT WHEN ATC GETS BUSY. THEY VECTORED A HEAVY MD-11 UNDERNEATH US AND THEN DESCENDED US BELOW THE MD-11. EVEN THOUGH WE WERE ABOUT 15 MILES BEHIND THE MD-11 WE HIT SEVERE WAKE TURB; NO ONE WAS HURT AS ALL PAX WERE BUCKLED IN. IF ATC ALLOWS ACFT TO FLY THE ARR AS PUBLISHED THIS SITUATION WOULD BE BETTER.

Data retrieved from NASA's ASRS site as of January 2009 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.