Regional Jet 200 ER/LR (CRJ200)
Flight Crew Air Transport Pilot (ATP)
Workload; Distraction; Confusion; Communication Breakdown; Troubleshooting
Aircraft Equipment Problem Critical
Flight Crew FLC complied w / Automation / Advisory; Flight Crew Overcame Equipment Problem; Flight Crew Took Evasive Action; Flight Crew Returned To Departure Airport; General Declared Emergency; General Maintenance Action
Aircraft
We were cleared for takeoff and once airborne and making the positive rate call the Captain called for gear up like any normal standard takeoff. The gear seemed to raise fine; but when it got up it switched to the 3 white boxes like the gear was up then the dropped back down. The gear [was] continuously cycling up then falling back down. The uplocks never locked the gear up and the gear always would fall back down then try to raise up again. The GEAR DISAGREE WARNING MESSAGE would come on and when it would go up and show 3 white boxes then fall it would go away then re-appear. When the gear would come back down the boxes on the gear would show the dashed lines as it was in the unknown position. I pulled out the QRH and the Captain maintained control of the airplane and spoke on the radios. I followed the QRH exactly line for line and ran the GEAR DISAGREE Emergency checklist. The checklist had me emergency extend the gear. So I got up out of my seat and stood over the top of the gear handle and emergency extended the gear. I continued to follow the Emergency procedure and the gear eventually locked down with 3 green.   Every 8 seconds the gear would cycle up and would fall back down. The GEAR DISAGREE WARNING would not cancel either. I have never heard or seen of the gear doing this on takeoff. It was truly a new experience for me on this aircraft. It seemed as if the gear would not stay up and the uplocks failed or the hydraulics were not allowing it to go all the way up. I checked the hydraulic system pressures and quantity and it showed normal and fine with 3;000 PSI and 70% quantity on the Number 3 System and it showed 2;900 PSI with 90% quantity on the Number 2 System. It seemed as if everything was normal on the hydraulics; but the cycling of the gear was strange.   There was an undesired state with this event that I want to mention. As the airplanes gear was cycling up and down we were maintaining 180 KTS because the QRH told us to stay under 200 KTS. The airplane due to the gear cycling up and down was oscillating up and down staying within 10 KTS. It was like it would pitch up then pitch down like we were a bouncing ball. It was a very unique experience. This was challenging as I was out of the seat pulling the emergency gear extension handle.  We declared an emergency; spoke with Maintenance and Dispatch and returned to land at the departure airport with no further incident. We had Tower and the trucks tell us our gear was verified down and they were not able to see any known damage. We stopped after exiting the Runway and had the airplane inspected for damage by the Fire Chief. All was fine. We returned to the gate and deplaned and Maintenance met us at the gate.Communicating with ATC was difficult in this scenario because the GEAR DISAGREE WARNING would not cancel. It was extremely distracting and made the situation a bit more stressful with the WARNING going off continuously until we were able to run the QRH. We opted not to turn the DCUs on the First Officer's side off; so we could monitor the emergency better. I was kept busy and heads down with the checklist to focus too much on the outside. ATC took us 40-60 miles west of airport and climbed us to 4;000 FT to keep us clear of terrain. We had weather to the north; so the only place we could really go was west while trying to stay close to the airport. We were overweight and needed to burn fuel. So with a gear issue we wanted to make sure we were under the 47;000 LB landing weight before landing. We didn't know if the gear had been damaged; so we took the extra time to burn off some fuel.  I am truly baffled as to why the gear did this. I have seen the gear disagree warning due to a nose gear door; but to see the gear cycling up and down and the pitch and airspeed oscillations occurring from the cycling of the gear constantly was a new one for me. It made it a bit more stressful after having seen 4 or 5 gear disagrees on this airplane. This one especially stood out for me and I would love to know what happened under there to cause the gear to do that. Our training we receive is excellent to be able to handle these situations and I am thankful for that. I would love a follow up on the aircraft please!
The reporter stated that a valve was replaced which corrected the anomaly. He knew the replaced valve was not the landing gear selector valve; but he did not remember exactly which valve was replaced. During the cycling full up to full down; even when the gear was in the uplocks for the 8 seconds before another cycle began; the landing never indicated safely up nor safely locked down when temporarily extended. The white gear indication followed by the dashed line; unknown state; were the only indications displayed along with the very loud gear warning horn. The QRH Emergency Extension procedure placed the aircraft in a safe state for landing.
[Report narrative contained no additional information.]
With the gear handle up after takeoff; a CRJ-200 landing gear repeatedly and autonomously cycled full up to full down along with a continuous landing gear warning horn. The landing gear indications were three white boxes while up for 8 seconds; followed by dashed lines during the extension cycle. Safe gear indications followed execution of the QRH Emergency Gear Extension checklist.