Envoy Air Flight 4028

The accident occurred when the left wingtip of United Airlines flight 2333 (UA2333), N480UA, an Airbus A320-232 collided with the right horizontal stabilizer and elevator of Envoy Airlines flight 4028 (ENY4028), N317TB, an Embraer ERJ-175 (which was stationary) while taxiing to the gate after landing at Chicago O’Hare International Airport (ORD), Chicago, Illinois. There were no reported injuries to passengers or crew on either airplane. ENY4028 sustained substantial damage to its elevator and horizontal stabilizer (Figure 1) and UA2333 sustained minor damage to its left winglet.

Figure 1. Left photo shows damage to ENY4028 right horizontal stabilizer and the right photo shows the damaged right elevator. (Source: Envoy Airlines) Statements from the Envoy Airlines flight crew indicated that ORD was experiencing a winter weather storm with heavy snow falling for several hours and the taxiways were covered in snow making the taxi center lines difficult to see. Statements from the United Airlines flight crew also indicated that the taxiways were completely snow-covered, obscuring centerlines, taxiway edges, and several taxiway signs.

According to the Envoy Airlines flight crew, flight ENY4028 conducted a single-engine taxi from gate L20 to runway 9R with engine No. 1 (left) operating, and auxiliary power unit (APU) in use. The airplane was taxiing northbound on taxiway U, when the flight crew attempted to turn the airplane left onto taxiway K. As the airplane started the left turn, it began to skid. The captain applied the brakes to prevent further movement and asked the first officer (FO) to start the No. 2 (right) engine in an attempt to regain control. While the FO started the engine, the captain informed air traffic control (ATC) of their situation and requested and received approval to remain stopped while they attempted to reposition the aircraft. Shortly thereafter, the flight crew felt the airplane being struck by an external object, and the nose moved from right to left about 5°. The FO looked to the right and observed a United Airlines Airbus that had just taxied behind them and continued forward.

According to statements from the United Airlines flight crew, they conducted an uneventful landing on runway 9C and proceeded to taxi toward gate C26, with reported visibility of ¼ mile with heavy snowfall. Once northbound on taxiway U, they observed ENY4028 attempting to make a left turn onto taxiway K. During the turn, the airplane appeared to slide slightly before continuing forward and then stopping. The flight crew elected to hold their position initially since ENY4028 appeared to partially block their path.

Once they were stationary, the captain visually cleared the left side of the airplane, and the FO visually cleared the right side of the airplane, and a sidestep maneuver was performed. The FO indicted that he verified verbally with the captain that they had clearance around the ENY4028. The captain confirmed. The flight crew indicated that they taxied forward at a very slow speed due to the restricted visibility and degraded taxiway conditions, closely monitoring the left wingtip for clearance. They observed their left wing pass the tailpipe of ENY4028 without issue. Shortly thereafter, they experienced a slight vibration. Their initial assessment was that they may have run over accumulated snow or debris on the taxiway, so they continued toward the gate.

Ground control advised UA2333 that another airplane reported possible contact with them from behind and asked whether they had noticed anything. UA2333’s flight crew advised ground control of experiencing a vibration. They asked ground control whether they preferred they stop or continue to the gate and were instructed to continue and advise of any observed damage. They arrived at the gate, deplaned normally, immediately contacted maintenance, and wrote an entry into the logbook. After the flight crew walked outside, they noticed the lower left winglet was damaged.

The automated weather reported at ORD at 1424 included visibility of ¼ statute mile in heavy snow and freezing fog.

The impact between UA2333 left winglet and ENY4028 tail resulted in a fractured winglet for UA2333 and damage to the ENY4028 right horizontal stabilizer and elevator. ENY4028’s elevator sustained a fractured tip cap and deformation to the trailing edge outboard end. ENY4028’s right horizontal stabilizer had a puncture about 20 inches long by 4 inches wide with fracture damage and deformation to the skin, 3 stringers and 1 rib. This damage adversely affected the structural strength and flight characteristics requiring a major repair or replacement and was considered substantial. The damage to the UAL2333 left winglet was considered minor.

Verbatim NTSB analysis and probable cause from the NTSB dataset