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Jet slams into hangar in California during run-up
A jet was on a ramp undergoing a routine engine run-up test when it rolled into the hangar. (www.cnn.com) 更多...
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"brakes - I knew there was something I missed on the checklist"
Actually, you are not far from the truth.... If my analysis is correct I know what happened. They were doing a check and one of them is to pull the WOW CB's (Weight Off Wheels). But the step they missed is to turn off the Anti-Skid first. To prevent pilots from landing with their brakes set, the Anti Skid removes the brakes (parking brakes included)and since it said they were doing a power run... The rest is history.
My guess is, they didn't turn on the 3 A&B pumps before start up and thought they set the park brake. These pumps are stand alone electric and provide N/W steering, gear uppy downy and brakes, as well as flight control redundancy. Normally on for takeoff and landing, start up and taxi. The prox. (proximity) switches are not normally pulled for ground runs, if memory serves me correctly, so as not to disable the brakes. I think they had it chocked, thought the brakes were set, and when it jumped the chocks it was off to the races and into a hangar. With both engines running you have 1&2 A pumps (engine driven) that power the inboard and outboard brakes. They would have had brakes after engine start from 1&2 A pumps. If you get the idea that a Challenger has a somewhat complicated hydraulic system, you would be right. There are 6 hydraulic pumps. Hydraulically drive flight controls, no manual reversion. Chime in here Preach, if you care to, I believe the CRJ has a very similar system.
I disagree, as the brake pressure would have bleed off gradually. 3B is to be run all the time and 3A as required. The CRJ and a Challenger are the same plane. One is corporate one is airline. When they pull the WOW without turning the AntiSkid off it will release the brakes. They were probably at FULL Power and then pulled the breaker and the ride begins.. You know the rest. As far as the breakers being pulled on ground runs, it depends on what checks you are running. If you are at IDLE, you have to pull the WOW breakers to test the HIGH IDLE. Once off the ground, the engines idle at a much higher rate. Running as much power as they were running, the chocks did not mean much.... Personally I feel that they HYD system is fairly simple. System 1 and 2 are flight controls primarily and 3 is for the gear/brakes/steering. However, system 3 also backs up all the primary flight controls. Pump 3A in auto mode comes on with flaps at greater than 0 degrees.
For the sake of agreeing to disagree, lets just say that I do have a CL60 type rating in my pocket and an A&P next to that. Tomato, tomoto, Bombardier calls them proximity or target type switches. In the hangar we used to put a piece of aluminum tape on them to do a trick me in flight test without jacking the airplane. Just pulling the breakers didn't do it all. Regardless, I will concede to your vast and superior knowledge, and comment that the ground test crew evidently didn't take the proper precautions for a high power ground test run and the results speak for themselves. By the way, my checklist, in front of me calls for all B pumps off in the climb section. As for a simple hydraulic system, not so. Hence the clean up on the 300. Too much weight.
If I am reading you right that would be an impossible scenario and here is why.There are 6 PROX Sensors, 3 of the 6 and 1 on each gear would have been already failed or marked. Further more they would have has a Prox System Fault. Also keep in mind that they would have never had any brakes, so unless they did this intentionally they would have never developed the speed to penetrate the building. Basically 2 sensors on each main gear would have had to fail at the same exact time. If that would not have happened they would have had a PROX SYSTEM FAULT and it would not have indicated Weight Off Wheels (or Air Mode) and released the brakes. If the PSEU had failed then it would again not allowed i to Weight Off Wheels configuration.
I have been a CRJ Mechanic (200 and 900) for 3 years now and currently working Maintenance Controller Position plus the fact of 28 years of Airline/Avionics/Electrical experience all in the part 121 arena may explain why I would call it fairly simple to understand and track... At least it is for me.
The only plausible thing that can come into mind is High Power with Anti Skid turned on. I am really interested to find out what the FDR and CVR says. American Eagle had one on an ERJ slide on ice into a hangar, blocking in 6 planes for several days because of door damage. Cause: Mechanics were talking and looking at Playboy Magazines and did not realize they were moving. Please look at: http://www.airdisaster.com/photos/n714bz/photo.shtml for an example of what getting distracted while thinking the plane is not moving :) Look at all 7 images.
I have been a CRJ Mechanic (200 and 900) for 3 years now and currently working Maintenance Controller Position plus the fact of 28 years of Airline/Avionics/Electrical experience all in the part 121 arena may explain why I would call it fairly simple to understand and track... At least it is for me.
The only plausible thing that can come into mind is High Power with Anti Skid turned on. I am really interested to find out what the FDR and CVR says. American Eagle had one on an ERJ slide on ice into a hangar, blocking in 6 planes for several days because of door damage. Cause: Mechanics were talking and looking at Playboy Magazines and did not realize they were moving. Please look at: http://www.airdisaster.com/photos/n714bz/photo.shtml for an example of what getting distracted while thinking the plane is not moving :) Look at all 7 images.
Didn't say they taped the targets,said we did on occasion for certain CAMP cards. Readily concede that your maintenance background is stronger than mine, but might also postulate that when we did high power runs, we also had light airplanes. Use big chocks, and don't aim the airplane at a hangar. And follow the cards to the letter, no matter how many times you have done it. And from the other end of the deal, I have more than once looked up to realize the airplane was moving after engine start, with a firm conviction that the brakes were set. The human side of aviation.
For the prox sensor to pick that up, it would have to be with in 50 thousandths of an inch (.050"). It would have to had been a target inserted into it, and then it would have had to be the correct type of metal.
This A/C with the brakes on can sustain running at full power with out moving. We do this routinely for power assurance runs, Engine Trimming, ETC.
This A/C with the brakes on can sustain running at full power with out moving. We do this routinely for power assurance runs, Engine Trimming, ETC.
