TCA flight 781 departed Tampa, Florida for Montreal at 1551 hours. Excepting for a malfunction of a cabin supercharger, the flight was normal until approaching for a let down on runway 28 at Montreal International Airport. It was found at that time that the left main undercarriage would not extend. The aircraft remained airborne for about three hours while various means of extending the undercarriage were attempted. All attempts at extension were unsuccessful and at 22:59 hours, after emergency precautions were taken, the aircraft was landed with all wheels retracted on runway 24R at Montreal International Airport. The aircraft was damaged but none of the passengers or crew were injured. Probable Causes The undercarriage did not retract properly because internal leakage prevented full extension of the oleo leg. Friction forces between the tyres and doors prevented opening of the door and extension of the undercarriage.