Narrative:

On 06/fri/04 at approximately XA35 local at ZZZ airport I was the nfp captain. The fp, also captain with my company, on takeoff runway xx at about 80 KT call-out, the aircraft began drifting and then abruptly veered to the left. The PF released the nosewheel steering control and used right rudder and aileron to gain back control and return to the near centerline by lift-off. Aircraft apparently contacted two runway light stanchions causing a large dent in the lear 35's left tip tank. This went unnoticed by the flight and cabin crew who neither felt or heard anything unusual. After successful completion of takeoff and landing 40 mins later at ZZZ1 we were made aware of some undetermined strike of some nature on left tip tank. We then phoned both the ZZZ1 and ZZZ control towers to inquire about any reported FOD or runway lights etc that had been damaged. We were told by both towers that at our request runways had been checked and no reported damage was found. We then suspected an airborne strike of an undetermined nature. Again we called both towers and gave them our cell phone # and proceeded to a laboratory for a voluntary drug and alcohol test. While returning to the airport we received a call from the supervisor at the ZZZ tower informing us that the state had discovered two damaged runway lights. At that point of apparent unexplainable drifting/veering action I quickly mentally reviewed possibilities of left main gear flat tire, a hung-up break, or FOD, or possible flight control problem with trim or rudder. Because of previous history with learjet steering problems. I felt that was the best possible explanation. An abort takeoff in my opinion at that time would have caused a severe accident. Instead the corrective action included stronger rudder and aileron input. Additionally, the PF released nosewheel steering. After careful review of all factors surrounding this incident I believe that the nosewheel steering on this aircraft could be modified and a look at how many similar learjet steering problems have been reported to NASA or the learjet factory. Callback conversation with reporter revealed the following information: the reporter stated the airplane nosewheel steering was tested on the ground at low speed and high speed and found malfunctioning. The reporter said the steering box and steering servo was replaced. The reporter stated the learjet 35 steering system is too sensitive and hard to adjust at high speeds. The reporter said many service difficulty reports have been sent to the manufacturer on the nosewheel steering system. Supplemental information from acn 620032: I feel the nosewheel steering system in lear 20/30 series could have a better steering authority system for adjustments/fine tuning. I've experienced many steering issues with the current system causing occurrences in the takeoff roll to veer from centerline.

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Original NASA ASRS Text

Title: A LEARJET 35 ON TKOF ROLL AT 80 KTS BEGAN DRIFTING TO THE L THEN ABRUPTLY VEERED TO THE L STRIKING TWO RWY LIGHTS.

Narrative: ON 06/FRI/04 AT APPROX XA35 LCL AT ZZZ ARPT I WAS THE NFP CAPT. THE FP, ALSO CAPT WITH MY COMPANY, ON TKOF RWY XX AT ABOUT 80 KT CALL-OUT, THE ACFT BEGAN DRIFTING AND THEN ABRUPTLY VEERED TO THE L. THE PF RELEASED THE NOSEWHEEL STEERING CTL AND USED R RUDDER AND AILERON TO GAIN BACK CTL AND RETURN TO THE NEAR CTRLINE BY LIFT-OFF. ACFT APPARENTLY CONTACTED TWO RWY LIGHT STANCHIONS CAUSING A LARGE DENT IN THE LEAR 35'S L TIP TANK. THIS WENT UNNOTICED BY THE FLT AND CABIN CREW WHO NEITHER FELT OR HEARD ANYTHING UNUSUAL. AFTER SUCCESSFUL COMPLETION OF TKOF AND LNDG 40 MINS LATER AT ZZZ1 WE WERE MADE AWARE OF SOME UNDETERMINED STRIKE OF SOME NATURE ON L TIP TANK. WE THEN PHONED BOTH THE ZZZ1 AND ZZZ CTL TWRS TO INQUIRE ABOUT ANY RPTED FOD OR RWY LIGHTS ETC THAT HAD BEEN DAMAGED. WE WERE TOLD BY BOTH TWRS THAT AT OUR REQUEST RWYS HAD BEEN CHKED AND NO RPTED DAMAGE WAS FOUND. WE THEN SUSPECTED AN AIRBORNE STRIKE OF AN UNDETERMINED NATURE. AGAIN WE CALLED BOTH TWRS AND GAVE THEM OUR CELL PHONE # AND PROCEEDED TO A LABORATORY FOR A VOLUNTARY DRUG AND ALCOHOL TEST. WHILE RETURNING TO THE ARPT WE RECEIVED A CALL FROM THE SUPVR AT THE ZZZ TWR INFORMING US THAT THE STATE HAD DISCOVERED TWO DAMAGED RWY LIGHTS. AT THAT POINT OF APPARENT UNEXPLAINABLE DRIFTING/VEERING ACTION I QUICKLY MENTALLY REVIEWED POSSIBILITIES OF L MAIN GEAR FLAT TIRE, A HUNG-UP BREAK, OR FOD, OR POSSIBLE FLT CTL PROB WITH TRIM OR RUDDER. BECAUSE OF PREVIOUS HISTORY WITH LEARJET STEERING PROBS. I FELT THAT WAS THE BEST POSSIBLE EXPLANATION. AN ABORT TKOF IN MY OPINION AT THAT TIME WOULD HAVE CAUSED A SEVERE ACCIDENT. INSTEAD THE CORRECTIVE ACTION INCLUDED STRONGER RUDDER AND AILERON INPUT. ADDITIONALLY, THE PF RELEASED NOSEWHEEL STEERING. AFTER CAREFUL REVIEW OF ALL FACTORS SURROUNDING THIS INCIDENT I BELIEVE THAT THE NOSEWHEEL STEERING ON THIS ACFT COULD BE MODIFIED AND A LOOK AT HOW MANY SIMILAR LEARJET STEERING PROBS HAVE BEEN RPTED TO NASA OR THE LEARJET FACTORY. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE AIRPLANE NOSEWHEEL STEERING WAS TESTED ON THE GND AT LOW SPEED AND HIGH SPEED AND FOUND MALFUNCTIONING. THE RPTR SAID THE STEERING BOX AND STEERING SERVO WAS REPLACED. THE RPTR STATED THE LEARJET 35 STEERING SYS IS TOO SENSITIVE AND HARD TO ADJUST AT HIGH SPEEDS. THE RPTR SAID MANY SERVICE DIFFICULTY RPTS HAVE BEEN SENT TO THE MANUFACTURER ON THE NOSEWHEEL STEERING SYS. SUPPLEMENTAL INFO FROM ACN 620032: I FEEL THE NOSEWHEEL STEERING SYSTEM IN LEAR 20/30 SERIES COULD HAVE A BETTER STEERING AUTHORITY SYSTEM FOR ADJUSTMENTS/FINE TUNING. I'VE EXPERIENCED MANY STEERING ISSUES WITH THE CURRENT SYSTEM CAUSING OCCURRENCES IN THE TKOF ROLL TO VEER FROM CTRLINE.

Data retrieved from NASA's ASRS site as of July 2007 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.