Narrative:

After landing an small transport at an unclted strip (paved, asphalt, 4000 ft X 70) condition levers were placed in high idle (70 percent np), propellers were already at full forward, and maximum-reverse thrust was selected. Initial np spool up O.K. After approximately 1-2 seconds, the right engine roared loudly (almost reverberating) directional control with rudders/nose wheel was momentarily lost (yaw was to the left). Aircraft was displaced from runway centerline approximately 1/2 to 3/4 the width of the aircraft and passed through an area of broken asphalt and short/medium grass. Control was regained by placing power levers out of reverse and slowly merging the aircraft back on to the runway centerline. The yaw that was caused by the right engine apparently coming out of reverse momentarily, displaced the nose of the aircraft approximately 20-30 degrees left. Post landing inspection revealed one blade of the left propeller had suffered what appeared to be a rock strike at the leading edge tip. No other obvious damage to the airframe or landing gear. Initial checks of reverse problem at slow speeds did not produce the yaw effect that was encountered at the approximately roll-out speed of 65 KTS. Inspection of the fuel control rigging that followed found the right engine out of small transport manual limits and the reverse settings to be not in accordance with prescribed settings. Possibility was also raised, because of the poor rigging, that the carbon block momentarily was displaced in the beta ring causing the momentary loss of reverse control. The overspd problem was attributed to rigging also and possible faulty setting of the fuel topping governor. The pre-rigging reverse check found the right engine reverse maximum RPM set at 2050, which was 150 RPM greater than the prescribed 1900 in reverse. Flight safety manuals say this RPM would interfere with the reversing process.

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Original NASA ASRS Text

Title: LOSS OF ACFT CTL OCCURS AS RIGHT ENGINE ON SMT FAILS TO OPERATE IN REVERSE PROPERLY.

Narrative: AFTER LNDG AN SMT AT AN UNCLTED STRIP (PAVED, ASPHALT, 4000 FT X 70) CONDITION LEVERS WERE PLACED IN HIGH IDLE (70 PERCENT NP), PROPS WERE ALREADY AT FULL FORWARD, AND MAX-REVERSE THRUST WAS SELECTED. INITIAL NP SPOOL UP O.K. AFTER APPROX 1-2 SECS, THE R ENG ROARED LOUDLY (ALMOST REVERBERATING) DIRECTIONAL CTL WITH RUDDERS/NOSE WHEEL WAS MOMENTARILY LOST (YAW WAS TO THE L). ACFT WAS DISPLACED FROM RWY CTRLINE APPROX 1/2 TO 3/4 THE WIDTH OF THE ACFT AND PASSED THROUGH AN AREA OF BROKEN ASPHALT AND SHORT/MEDIUM GRASS. CTL WAS REGAINED BY PLACING PWR LEVERS OUT OF REVERSE AND SLOWLY MERGING THE ACFT BACK ON TO THE RWY CTRLINE. THE YAW THAT WAS CAUSED BY THE R ENG APPARENTLY COMING OUT OF REVERSE MOMENTARILY, DISPLACED THE NOSE OF THE ACFT APPROX 20-30 DEGS L. POST LNDG INSPECTION REVEALED ONE BLADE OF THE L PROP HAD SUFFERED WHAT APPEARED TO BE A ROCK STRIKE AT THE LEADING EDGE TIP. NO OTHER OBVIOUS DAMAGE TO THE AIRFRAME OR LNDG GEAR. INITIAL CHKS OF REVERSE PROB AT SLOW SPDS DID NOT PRODUCE THE YAW EFFECT THAT WAS ENCOUNTERED AT THE APPROX ROLL-OUT SPD OF 65 KTS. INSPECTION OF THE FUEL CTL RIGGING THAT FOLLOWED FOUND THE R ENG OUT OF SMT MANUAL LIMITS AND THE REVERSE SETTINGS TO BE NOT IAW PRESCRIBED SETTINGS. POSSIBILITY WAS ALSO RAISED, BECAUSE OF THE POOR RIGGING, THAT THE CARBON BLOCK MOMENTARILY WAS DISPLACED IN THE BETA RING CAUSING THE MOMENTARY LOSS OF REVERSE CTL. THE OVERSPD PROB WAS ATTRIBUTED TO RIGGING ALSO AND POSSIBLE FAULTY SETTING OF THE FUEL TOPPING GOVERNOR. THE PRE-RIGGING REVERSE CHK FOUND THE R ENG REVERSE MAX RPM SET AT 2050, WHICH WAS 150 RPM GREATER THAN THE PRESCRIBED 1900 IN REVERSE. FLT SAFETY MANUALS SAY THIS RPM WOULD INTERFERE WITH THE REVERSING PROCESS.

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.