US officials are investigating left main landing gear failures on two types of Bombardier regional jets on two separate occasions this week, incidents that left the aircraft damaged but did not result in any passenger injuries.

In the first case, an Air Wisconsin CRJ-200 enroute from Norfolk to Philadelphia flying for US Airways with no passengers landed with its left main gear retracted on Runway 27L at the Philadelphia International Airport. Air Wisconsin could not be immediately reached as to the cause of the original delay or the status of the investigation.

Pilots announced the problem to air traffic controllers and spent more than an hour in Philadelphia airspace attempting to correct the issue. Ultimately unable to extend the gear, the pilots landed with the left gear up, skidding to a halt on the runway and closing the airport for one hour.

Mechanics lifted the aircraft's left wing with a crane and freed the gear so that aircraft could be towed to the maintenance facility where National Transportation Safety Board officials were to begin an investigation, according to an FAA spokeswoman. Damage is "minor" and limited to the left wing and left wingtip, says FAA.

The second gear failure involved a Mesa Airlines CRJ-700 flying as United Express experiencing a left main gear collapse on rollout after landing on Runway 28 at the Chicago O'Hare International Airport. None of the 28 passengers and four crew were injured.

Pilots had earlier departed O'Hare for South Bend, Indiana, when they received an "unsafe gear" indication light in the cockpit and returned to Chicago to land, says an FAA spokeswoman. Passengers evacuated the plane using the front stairs. Mesa could not be immediately reached for comment.

Source: Air Transport Intelligence news