NTSB Factual Report

1. HISTORY OF FLIGHT

On September 25, 2010, about 2018 Eastern daylight time (EDT), Atlantic Southeast Airlines flight 4951 (N133EV), a Bombardier, Inc. CL-600-2D24 (Regional Jet Series 900), landed at John F. Kennedy International Airport (JFK), Jamaica, New York with the right main landing gear (MLG) retracted. The flight was enroute from Hartsfield-Jackson Atlanta International Airport (ATL), Atlanta, Georgia to Westchester County Airport, White Plains, New York (HPN) when it diverted due to a gear unsafe warning. The 60 passengers and 4 crew evacuated the airplane on Runway 31R, with no injuries reported. The scheduled domestic passenger flight was being conducted under the provisions of 14 Code of Federal Regulations, Part 121 on an instrument flight rules flight plan.

According to the flight crew, the flight from Atlanta to Westchester County Airport was normal. However, when the crew commanded the landing gear down while on approach to landing, the right hand MLG disagree message was annunciated. The crew determined that the right MLG was not down and locked. The normal and alternate extension methods failed to extend the right MLG.

After speaking with airline maintenance, the flight crew decided to declare an emergency and divert to John F. Kennedy International Airport. The crew landed on Runway 31 Right with the nose and left main landing gears normally extended and locked but the right main landing gear not extended. During the landing roll, the slats and flaps on the right wing contacted the runway.

Once the airplane stopped on the runway, the passengers and crew vacated the airplane through the forward passenger door. No injuries were reported and the aircraft did not experience any fire or other post landing concerns.

2. DAMAGE TO AIRPLANE

The airplane was moved from the runway to a maintenance hangar for the investigation. The right side of the airplane was lifted off the ground and supported by wooden pallets and jacks. The on-scene examination documented abrasion damage to the inboard and outboard flaps on the right wing, the right aileron control surface, the number two and three leading edge slats and fittings on the right wing, leading edge, spar, skins, and panels of right hand winglet, and the auxiliary spar. In addition, a gouge was noted on the left side of the fuselage.

The on-scene examination found/determined that the right MLG door was caught inside the right fuselage wheel fairing and was jammed.

3. AIRCRAFT INFORMATION

The airplane was a Bombardier, Inc. Regional Jet Series 900, CL-600-2D24, registration N133EV, and serial number 15222. At the time of the incident, at the time of the incident, the airplane had accumulated 4,047 hours and 2,792 cycles.

The airplane was powered by two CF 34 - 8C5 engines (s/n 194803 194812, engine 1 and 2 respectively)

4. METEOROLOGICAL INFORMATION

At the time of the incident landing, the airport was under night time conditions with clear skies, visibility of 10 miles, and dry runway conditions.

5. AIDS TO NAVIGATION

No reported problems.

6. COMMUNICATIONS

Communications were normal and not considered significant.

7. AIRPORT INFORMATION

The flight was originally scheduled to land at Westchester County Airport, White Plains, New York, but instead diverted to John F. Kennedy International Airport, New York, New York (JFK) after the flight crew received the gear unsafe warning. The airplane landed on Runway 31 Right at JFK, with no significant damage to the runway reported.

After the passengers were removed, the airplane was towed to a maintenance hangar.

8. FLIGHT RECORDERS

The flight recorders were removed and downloaded following the incident.

9. TEST AND RESEARCH

During the investigation of the incident a landing gear "swing" test was conducted. With the airplane lifted off the floor, the right main landing gear was released from the wheel fairing. The gear swung to a down and locked condition. The airplane's landing gear was then cycled, and when commanded up using the flight deck landing gear handle, the right main gear again became jammed inside the fuselage wheel fairing. When the gear was then commanded down, the right main gear would not extend.

The NTSB has investigated a previous, similar event; previously, another CRJ-900 experienced a similar event at Chicago, Illinois. On December 15, 2008, a Bombardier CL-600-2C10 (CRJ-700), registration N511MJ, operated by Mesa Airlines, Inc. and doing business as Air Shuttle Flight 7164, sustained minor damage during a landing gear emergency at Chicago O'Hare International Airport. The Title 14 Code of Federal Regulations Part 121 passenger flight had departed O'Hare enroute to South Bend Regional Airport, South Bend, Indiana. During the landing approach to South Bend, the landing gear "Gear Disagree" warning message appeared. The flight crew performed the appropriate emergency checklists without success. The flight returned to O'Hare and an emergency landing was conducted on runway 28. The airplane landed with a fully extended nose and right main landing gear, but the left main gear was not extended.

Following the December 2008 event, Bombardier issued Service Letter CRJ700/705/900-SL-32-039. The Service Letter included a fleet inspection recommendation. The letter indicated that

"Improper positioning of the door (possibly due to rigging) could result in extra pressure on the seal / premature wear of the rubber covering the metallic stiffener thus causing the metal stiffener to be exposed. This condition could potentially result contact with the MLG Door and in restricted movement of the main landing gear during extension."

The recommended interim action by Bombardier was an inspection of the body fairing seal common to the door. If the seal was worn "to the point the inner metallic seal stiffener is clearly visible", the operator was recommended to either replace the damaged seal and rig the door per AMM TASK 32-12-01-220-801 or removed the MLG inboard door per a Configuration Deviation List.

10. ADDITIONAL INFORMATION

On 18 October 2010 Transport Canada issued Airworthiness Directive CF-2010-36, Subject "Main Landing Gear Door – Fairing Seal Interference", Applicable to Bombardier, Inc. Models CL-600-2C10 (serial numbers 10003 and subsequent) and CL-600-2D15 and CL-600-2D24, (serial numbers 15001 and subsequent). The AD was effective upon receipt.

The AD instructed the following corrective actions (dependent on the airplane model serial number):

1. Required a detailed inspection of the MLG fairing and seal, MLG door and adjacent structures as per Bombardier Alert Service Bulletin A670BA-32-030, dated 18 October 2010, titled Landing Gear – Main Landing Gear (MLG) and Doors Inspection of the MLG Inboard Doors and MLG Fairing, or later provisions as approved by Transport Canada.

2. The AD required repeat inspections each 600 hours (of air time).

NTSB Probable Cause

The probable cause of the incident was the restriction of the right main landing gear door against the fuselage wheel well body fairing which prevented the extension of the right main landing gear.