Narrative:

I was the captain and the pilot flying. Upon arrival at ZZZZ; the AWOS was out of service (no NOTAM was issued) and my first officer retrieved the weather from ZZZ1; about 20 miles away. Weather conditions at ZZZ were very similar; sky clear; visibility unrestricted; winds 280 at 15 knots. We called the airport in sight at about ten miles out; and cancelled our IFR flight plan with approach. Runway xx/yy is the longest runway at ZZZ; with 5000 ft of pavement available. A visual approach was conducted to runway yy at ZZZ; with final approach speed held between vref +10 and vref +15 due to minor wind gusts. Touchdown was normal for a light crosswind; left(upwind) wheel first; about 1000 ft down the runway. The ship's autospoilers were armed; and immediately after touchdown the first officer called 'boards are up' indicating their deployment. I then actuated the thrust reversers; and she called 'two unlocks...right deployed.' the piggyback lockout was still engaged; confirming her callouts that one thrust reversers was not deployed; and keeping both engines at idle thrust. Not having thrust reversers; I began heavy application of the wheel brakes roughly 2500 ft down the runway; and the aircraft began drifting right of centerline. I applied increasing amounts of left rudder in an attempt to maintain the centerline; however; the aircraft continued yawing to the right even with full left rudder and maximum left brake. At roughly 6-8 seconds after the right thrust reverser deployed; the first officer called 'left reverser deployed;' and I began applying reverse thrust. With both reversers deployed; the aircraft slowed very quickly; however; the right yawing moment was still present and the right main landing gear left the right edge of the runway about 4300 ft down the runway; and at roughly 40 KTS. The aircraft came to a stop with the right main gear partially sunk in the sandy dirt shoulder of the runway; approximately 10-12 inches off the pavement; and the nose wheel and left main gear both on the runway. We called the local FBO for a tug to pull us back on the runway; and shut down the aircraft. I was suspecting a blown tire on the right side; and a visual inspection of the landing gear was made. All four main tires looked normal; but curiously wheels #1; 3 & 4 were very hot (too hot to touch); while wheel #2 (left inboard) was cool. A subsequent walk down the runway showed three very distinct skid marks from the #1; 3 & 4 tires; but no skid marks from tire #2. Fortunately; no part of the aircraft ever came in contact with the ground; or runway lighting; etc; a subsequent inspection of the aircraft showed no damage to the landing gear; gear doors; right flap; or right wing. It is my suspicion that the #2 brake failed; resulting in twice as much braking action on the right side of the aircraft; which coupled with the asymmetrical thrust reversers deployment caused the uncommanded yaw to the right. The aircraft was grounded and turned over to maintenance. A review of the maintenance logs indicated that tires #1 and #4 had been changed the previous evening; and that the thrust reverser's had been written up in the past four months for intermittent slow deployment. The brakes were inspected and found to be serviceable; but at their wear limits per the learjet maintenance manual. Brakes on all four wheels were changed; along with tires #2 and #3 and the nose tire; which had skidded to the right. My estimate of contributing factors are: #1 tire brand new; while #2 tire had been in service for two months (note this is acceptable per the learjet maintenance manual). Possible air in the brake lines from the previous day's maintenance. Brake ineffectiveness due to worn pads. #2 thrust reversers deployment 6-8 seconds after #1 thrust reversers deployment. 15 KT crosswind from the left.

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Original NASA ASRS Text

Title: Lear 55 flight crew reports departing right edge of runway after landing due to asymmetrical thrust reverser deployment and minimal braking on one wheel on the left side.

Narrative: I was the Captain and the pilot flying. Upon arrival at ZZZZ; the AWOS was out of service (no NOTAM was issued) and my First Officer retrieved the weather from ZZZ1; about 20 miles away. Weather conditions at ZZZ were very similar; sky clear; visibility unrestricted; winds 280 at 15 knots. We called the airport in sight at about ten miles out; and cancelled our IFR flight plan with Approach. Runway XX/YY is the longest runway at ZZZ; with 5000 FT of pavement available. A visual approach was conducted to Runway YY at ZZZ; with final approach speed held between Vref +10 and Vref +15 due to minor wind gusts. Touchdown was normal for a light crosswind; left(upwind) wheel first; about 1000 FT down the runway. The ship's autospoilers were armed; and immediately after touchdown the First Officer called 'boards are up' indicating their deployment. I then actuated the thrust reversers; and she called 'two unlocks...right deployed.' The piggyback lockout was still engaged; confirming her callouts that one thrust reversers was not deployed; and keeping both engines at idle thrust. Not having thrust reversers; I began heavy application of the wheel brakes roughly 2500 FT down the runway; and the aircraft began drifting right of centerline. I applied increasing amounts of left rudder in an attempt to maintain the centerline; however; the aircraft continued yawing to the right even with full left rudder and maximum left brake. At roughly 6-8 seconds after the right thrust reverser deployed; the First Officer called 'left reverser deployed;' and I began applying reverse thrust. With both reversers deployed; the aircraft slowed very quickly; however; the right yawing moment was still present and the right main landing gear left the right edge of the runway about 4300 FT down the runway; and at roughly 40 KTS. The aircraft came to a stop with the right main gear partially sunk in the sandy dirt shoulder of the runway; approximately 10-12 inches off the pavement; and the nose wheel and left main gear both on the runway. We called the local FBO for a tug to pull us back on the runway; and shut down the aircraft. I was suspecting a blown tire on the right side; and a visual inspection of the landing gear was made. All four main tires looked normal; but curiously wheels #1; 3 & 4 were very hot (too hot to touch); while wheel #2 (left inboard) was cool. A subsequent walk down the runway showed three very distinct skid marks from the #1; 3 & 4 tires; but no skid marks from tire #2. Fortunately; no part of the aircraft ever came in contact with the ground; or runway lighting; etc; a subsequent inspection of the aircraft showed no damage to the landing gear; gear doors; right flap; or right wing. It is my suspicion that the #2 brake failed; resulting in twice as much braking action on the right side of the aircraft; which coupled with the asymmetrical thrust reversers deployment caused the uncommanded yaw to the right. The aircraft was grounded and turned over to maintenance. A review of the maintenance logs indicated that tires #1 and #4 had been changed the previous evening; and that the thrust reverser's had been written up in the past four months for intermittent slow deployment. The brakes were inspected and found to be serviceable; but at their wear limits per the Learjet Maintenance Manual. Brakes on all four wheels were changed; along with tires #2 and #3 and the nose tire; which had skidded to the right. My estimate of contributing factors are: #1 tire brand new; while #2 tire had been in service for two months (note this is acceptable per the Learjet Maintenance Manual). Possible air in the brake lines from the previous day's maintenance. Brake ineffectiveness due to worn pads. #2 thrust reversers deployment 6-8 seconds after #1 thrust reversers deployment. 15 KT crosswind from the left.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.