Date: 201403
Local time of day: 1201-1800
Location: ZZZZ.Airport, FO
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Challenger CL604
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Test Flight / Demonstration
Flight phase: Landing
Aircraft component: Flap Control (Trailing & Leading Edge)
Component problem: Malfunctioning
Reporter organization: Personal
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Training / Qualification; Confusion; Situational Awareness; Communication Breakdown
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Aircraft Aircraft Damaged; Flight Crew Landed in Emergency Condition; General Maintenance Action
Contributing factors: Procedure; Staffing; Aircraft; Human Factors
Primary problem: Human Factors

Narrative: As part of the 48 month check; aircraft was required to do an ADG (Air Driven Generator) drop test; to simulate total loss of aircraft power in flight; and ascertain the serviceability of the back up ADG. The Maintenance Organization told us an Engineer would go with us for the test. We were supposed to just takeoff; do one visual circuit at the airport; drop the ADG and return for landing. We departed from Runway 03 and climbed to 2;400 FT. On the downwind leg; we asked the Engineer how he wanted the test conducted and it was agreed that generators 1 and 2 should be taken off. The ADG deployed successfully. On base leg; however; we could not get more than flaps 20 (which was the flaps we took off with and had chosen not to retract). We did the approach at flaps 20 speed of 160 KTS and only slowed down just prior to touchdown. After landing; only the left reverser deployed; we did not have ground spoilers; nose wheel steering and the anti-skid. This necessitated the application of maximum braking on the landing rollout; which resulted in the blow out of the four main tires. Aircraft was stopped on the runway and did not sustain any damage apart from the blown tires. There was no injury to the three crew on board. Roles were not clearly spelt out between the pilots and the Engineer on board before the commencement of the flight. The pilots assumed the Engineer was on board to talk us through the flight test; since we did not know other things he needed to see that necessitated his coming on the flight test. The Engineer later said he did not know the pilots were expecting any inputs from him; so there was a communication gap. Flight crew should have relied on the QRH; rather assume the Engineer was on board to talk us through the flight test.




Synopsis: When a regular line flight crew was utilized to perform a required simulated failure of the AC electric system for a regular periodic maintenance check; a Maintenance Engineer was assigned to accompany them. When there was no comprehensive briefing as to how to perform the check it was conducted using TLAR (That Looks About Right) methodology which resulted in the loss of multiple systems for landing. Four main gear tires blew out when max braking was applied after the spoilers failed to deploy; one reverser failed to operate and the landing had had to have been made with only 20 degrees of flaps extended.