Learjet 23

The crew departed Puebla-Hermanos Serdán-Huejotzingo Airport on a positioning flight to Atlangatepec. On approach to runway 01, the crew made a low pass over the runway then initiated a go-around procedure followed by a circuit in an attempt to land on runway 19. On final approach in limited visibility due to the night and low clouds, the aircraft impacted the water surface and crashed in the Atlanga lagoon. The aircraft sank by a depth of about 30 metres some 800 metres short of runway threshold. Both pilots were killed.

On March 4, 1998, at 1350 hours Pacific standard time, a Learjet 23, N37BL, was substantially damaged when it landed gear up at the Oakdale, California, airport. The airline transport pilot and check pilot, the sole occupants, were not injured and no property damage occurred. The flight was operating under 14 CFR Part 91 on a familiarization and training flight. Visual meteorological conditions prevailed and no flight plan was filed. The pilot stated in his report "the landing gear was never extended and the aircraft was landed with the gear retracted."

A lineman noted parking brake (p/b) was set before flight. Pilots began takeoff on 5,147 feet runway with 10 knots crosswind. A witness said aircraft rotated for takeoff about 4,500 feet down runway and lifted off about 50 feet later. Reportedly, it remained low and slow (20-60 feet agl) after lift-off, then banked (rocked) left and right in nose high attitude, settled, hit trees and crashed abt 200 feet beyond runway. One person said aircraft went out of control before impact; another said it was 'in or on the edge of stalled flight.' Examination showed rotational damage occurred in both engines during impact. The braking systems had evidence that p/b control valve was partially on; brake torque tube contained heat blueing. On this early model (Learjet 23/sn: 23-45a), p/b had to be released by depressing brake pedals first; pilot handbook did not address this. On later models (sn: 23-050 and up), p/b needed only to be moved 'off.' Investigations showed left seat pilot had training in later models (Learjet 24/25); but only a biennial flight review was noted in the model 23. Company dispatcher said no training would have been performed on accident flight (with passenger aboard). Aircraft was about 430 lbs over max weight limit. All three occupants were killed.

The pilot had computed landing performance information for a landing on a wet runway with anti-skid; sufficient runway surface was available. Touchdown was normal, however during the braking process, the airplane started to fishtail and the pilot believed that the anti-skid system had failed. Therefore, the pilot turned the antiskid system off and continued the rollout with normal braking. The airplane went off the departure end of runway 05 and sustained substantial damage. Performance data indicated more runway surface was required for a safe landing on a wet runway without anti-skid assistance. The braking sequence of events described by the pilot resembled dynamic hydroplaning where there was a complete loss of braking effectiveness rather than an anti-skid malfunction. An examination of the airplane failed to disclose any mechanical problems.

At 0515 est, the flight was cleared for takeoff on a flight from Ypsilanti, MI to Louisville, KY. About 17 minutes later, the flight crew began to display indications of a deterioration of their ability to control the aircraft. At 1st, they deviated from instruments to hold west of the Findlay VOR at FL220. As the flight continued and was cleared to FL270, the crew displayed confusion about magnetic headings and basic instruments. At 1048 est, the aircraft deviated from the en route heading and the wrong heading was read back after a heading correction was given. Also, the aircraft continued climbing (to FL291), then radar and radio contact were lost at 0551 est. The controller noted the pilot's speech was slurred and some portions of the conversation were unintelligible. Subsequently, the aircraft crashed in a steep dive. No preimpact part failure was verified, though impact forces and post-crash fire resulted in extensive damage of the aircraft. The aircraft was equipped with oxygen and pressurization system. No audible warning was noted on ATC recordings to indicate the cabin altitude had exceeded 10,000 feet, though the aircraft was equipped with such a device. Both pilots were killed.

For unknown reasons, the twin engine aircraft belly landed at Lisbon-Portela de Sacavém Airport and slid for few dozen meters before coming to rest. Both pilots were uninjured while the aircraft was damaged beyond repair.

After landing at the aircraft's manufacturer facility with an asymmetric fuel condition and an inoperative yaw damper the crew elected to continue the flight to their destination without correcting the deficiencies. Enroute the captain informed air traffic controllers that he had fuel coming from one tank and that he doubted that had fuel available to reach his destination. The controller cleared the aircraft to land at a March AFB, the nearby airport. As the aircraft turned onto the final approach it rolled inverted and impacted the ground inverted short of runway 32. Both pilots were killed.

On approach to Guatemala City-La Aurora Airport, the crew encountered poor weather conditions and limited visibility. It is believed he also encountered engine problems when the aircraft struck tree tops and crashed few km short of runway. A crew member was rescued while two other occupants were killed. The flight was operated on behalf of DHL Airways.