Crash-aerien 26 APR 2003 d'un Sino Swearingen SJ30-2 N138BF - Loma Alta, TX
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Statuts:Enquête Officielle
Date:samedi 26 avril 2003
Type/Sous-type:Silhouette image of generic SJ30 model; specific model in this crash may look slightly different
Sino Swearingen SJ30-2
Compagnie:Sino Swearingen
Immatriculation: N138BF
Numéro de série: 002
Année de Fabrication: 2000
Heures de vol:284
Moteurs: 2 Williams International FJ44-2A
Equipage:victimes: 1 / à bord: 1
Passagers:victimes: 0 / à bord: 0
Total:victimes: 1 / à bord: 1
Dégats de l'appareil: Détruit
Conséquences: Written off (damaged beyond repair)
Lieu de l'accident:16 km (10 milles) N of Loma Alta, TX (   Etats-Unis d'Amérique)
Phase de vol: En cours de manoeuvre (MNV)
Aéroport de départ:San Antonio International Airport, TX (SAT/KSAT), Etats-Unis d'Amérique
Aéroport de destination:San Antonio International Airport, TX (SAT/KSAT), Etats-Unis d'Amérique
N138BF was the first of two conforming prototypes of the SJ30-2 business jet. The aircraft departed San Antonio for flight test number 231 for flight flutter certification. The first flutter mission, flight test number 230, was flown one day earlier with the same pilot onboard. The pilot terminated the flight after an uncommanded roll to the left, and a subsequent discrepancy was noticed between his displayed airspeeds and those reported by a chase plane pilot. After takeoff, the airplane climbed to 39,000 feet and set up for a shallow dive along a 090-degree track. This time no problems were noted. The airplane subsequently turned back to the west and began to climb back to 39,000 feet to set up for another dive to the flight test point along a 270-degree magnetic track. This run also was uneventful. The pilot was then cleared to the next test point. However, the pilot did not acknowledge the clearance, but instead, reported that the airplane was rolling to the right, and he couldn't stop it. About 30,000 feet, the test airplane began rolling to the right. The rolling maneuver appeared to be stable, and continued unchanged until ground impact. The airplane rolled about 7 times during a 49-second timeframe, from about 30,500 feet until a near-vertical ground impact.
Although the manufacturers engineering analysis (which did not include any high-speed wind tunnel testing) had predicted positive lateral stability up to Mach 0.90, lateral control was lost during the accident flight below that speed. After the accident, the company conducted high-speed wind tunnel tests, and found that lateral stability decreased with increasing Mach and angle of attack (AOA). Lateral stability became negative (unstable) above Mach 0.83, and rudder input intended to augment lateral trim above a certain Mach could aggravate the situation.

Probable Cause:

PROBABLE CAUSE: "The manufacturer's incomplete high-Mach design research, which resulted in the airplane becoming unstable and diverging into a lateral upset."

Accident investigation:
Investigating agency: NTSB
Status: Investigation completed
Duration: 1 year and 11 months
Accident number: IAD03MA049
Download report: Summary report



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