Date: 201307
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Dawn
Aircraft: EMB ERJ 145 ER/LR
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
Airspace: Class B ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: Squat Switch
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Anomaly: Aircraft Equipment Problem Critical
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed As Precaution; Flight Crew Returned To Departure Airport; General Declared Emergency
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Immediately after takeoff; we received an LG AIR/GROUND FAIL on the EICAS and the landing gear would not retract. We ran the appropriate checklists (LG AIR/GROUND FAIL and the checklist for non-retraction of the landing gear); which directed us to land at the nearest suitable airport. We briefed the Flight Attendant and told her that the landing would likely seem relatively normal; however; there was a chance we could have a longer landing roll if spoilers/thrust reversers failed to deploy. We told her that we anticipated coming to a complete stop on the runway; checking with her that everyone was down; and then proceeding to the gate. If for any reason we felt that we were going to be unable to stop on the runway; we'd command 'brace' over the PA; in which case she should start using brace commands; however; felt it was unlikely that would occur. We declared an emergency; since this was an unusual situation and that there was a potential for compromised stopping ability. We requested the longest runway; took the QRH corrections into account for landing distance; and discussed possible issues; such as if the touchdown protection released brakes below 10 KTS (hence checking our ability to come to a complete stop on the runway); hot brakes; etc. I made two announcements during the event over the PA. The first was to confirm the unusual noise to the passengers (gear was still down) and that we would be running the appropriate checklists for a few minutes and the second was that we would be conducting a return to the airport for this condition. We made assurances with the passengers that while this was an unusual situation; the gear is down and locked and we can't retract it...thus; it's in its normal position for landing. We landed uneventfully. The condition remained after touchdown. Thrust reversers and spoilers did not deploy. We came to a complete stop with brakes only. The Flight Attendant confirmed everyone was seated after we came to a stop on the runway; we checked brake temperatures and then conducted a normal taxi to the gate; guarding the emergency brake throughout in case the touchdown protection was to release them. The maintenance logbook did show that a strut repack (if memory serves) had been conducted recently; so we're not sure if that procedure resulted in a problem with the WOW sensors. The landing was not an overweight landing.The most obvious undesired aircraft state was the inability to raise the landing gear and the inability to deploy thrust reversers and spoilers after landing. Also; we were getting numerous takeoff configuration warnings (when trim was out of the green range). We elected to reduce power and climb slower so we could run the checklists without the distraction of the takeoff configuration system. Since the gear was down and locked; we were also stuck in takeoff power; which was another reason we elected to have power reduced to avoid exceeding the 5 minute limit if we didn't have to. We were fairly light and the plane climbed just fine without being in the detent; especially considering we were only climbing to 5;000 FT. All and all; I think we handled the situation well. We had positive transfer of controls when necessary; flying pilot flew while the pilot not flying handled the checklists. There was some confusion in finding the appropriate checklists; so I transferred controls to the First Officer for a bit while I looked for the procedures; etc; and had him fly while I talked to Operations and Maintenance. We took our time. We knew we had plenty of fuel; just had ATC vector us while we attended to the various checklists and performance planning.After-the-fact; we discussed whether we should have manually selected the flight spoilers after touchdown to get some spoiler assistance. I had thought that the condition would clear after touchdown; thinking it was failed on the flight side; since we didn't have any unusual indications prior to takeoff; but that wasn't the case. The checklist didn't call for using flight spoilers after touchdown; so we just stuck to the checklist; but didn't know if this was something worth consideration for the training department/standards. Perhaps after touchdown calling for spoilers and having the pilot not flying opening them.




Synopsis: EMB145 Captain experiences LG AIR/GROUND FAIL on takeoff which prevents the landing gear from retracting. QRH procedures are complied with; an emergency is declared and flight returns to the departure airport.