Narrative:

Upon initial descent for approach to destination airport; when throttle was pulled back; there was no response in manifold pressure. Gauges indicated full throttle. Cycling of throttle gave no change; throttle was stuck at full. PIC engaged spouse (also a private pilot) to maximize crew resource management. PIC's spouse examined operator's manual for emergency procedure for loss of throttle control at full power. No procedure exists. Troubleshooting by PIC and ensuing discussion with spouse resulted in a plan for landing as safely as possible. Gear was dropped and 10 degrees of flaps extended; resulting in an airspeed of 115 KIAS. (Normal landing speed is 65 KIAS.) further flaps could not be used due to speed in excess of 100 KIAS. Radio call to airport unicom at 15 miles out for field advisory and again at 5 miles out to alert to intent for wide pattern and low angle fast approach. Low angle approach decision in attempt to minimize any additional airspeed. Airport advisory indicated right quarter crosswind 6 KTS gusting to 15 KTS. In pattern calls were made to alert any other traffic. Runway length 3000 ft; more than three times normal landing roll (at 65 KIAS) was felt to be adequate. Planned alternate field runway was also only 3300 ft. Other airports were not considered since it was unknown how much more quickly fuel was being consumed at full throttle. Nearest potential runways significantly longer than 3000 ft not involved class B airspace or more highly congested residential areas were felt to be possibly out of range for more than one attempted approach due to maximum fuel consumption rate. Decision to maintain engine power as long as possible (rather than early shutdown and use of gliding landing due to: 1) congested residential area and rising terrain beneath pattern and final approach; and 2) minimize risk of crash landing by maintaining the option for a go-around. Two approaches attempted with prop RPM backed off maximum possible and engine was shut off on final approach when field was considered made. Immediately upon touch-down (105 KIAS) flaps were retracted and yoke was pushed forward with slight aileron deflection due to crosswind. Due to speed and resulting lift; brakes did not have maximum effectiveness; this made even braking extremely difficult and possibility for ground loop. When approaching end of runway; decision was made to veer to grass to assist slowing aircraft as there was a road; a jogging/bicycle trail; and a gravel pit just beyond the end of the runway; in that order. Taxiway light was struck by slowing; spinning prop as aircraft exited runway. Grass slowed aircraft significantly but aircraft continued to climb embankment onto road. The PIC looked both ways; and traffic was observed to be already stopped in both directions. Maximum braking applied once of road resulting in aircraft coming to rest with nose gear just off pavement onto gravel shoulder opposite or runway; main gear were still on the road pavement. PIC immediately set brakes and exited aircraft to control traffic after ensuring other two aircraft occupants were without injury. Airport personnel were immediately on the scene to assist in rolling aircraft back to taxiway for towing to FBO. Local police and fire were on scene within five to ten minutes. There were no injuries to three occupants of aircraft; nor anybody on the ground. The only damage on the ground was the single taxiway light. Due to prop strike to taxiway light; prop must be replaced and engine torn down for inspection. Once towed to FBO; aircraft a&P removed cowling to examine throttle cable. The nut on the bolt holding the end of the throttle cable was missing; and there was no cotter key to hold the nut in place. The result was the throttle cable coming completely disconnected from the throttle; with spring holding throttle in full power position. Further considerations: a full throttle landing is not taught nor practiced nor considered in training. Nor is it covered in the owner's manual. The procedures in this case were; literally; invented on the fly. Three times normal landing distance was inadequate in this scenario; due to the lift generated by excessive landing speed and brake ineffectiveness. Divert to a runway at least five times; or even perhaps six times landing distance is suggested if possible; this can be a difficult decision when fuel flow rate is unknown and potentially significantly greater than normal. Also; decision was made in this case to keep engine running due to heavily populated area to approach end of runway; in an attempt to avoid misjudged distance and crash landing short among houses or on rising terrain leading to approach end of runway; as well as giving option for a go-around if necessary - as it was twice in this scenario. Ideally; in less populated area with significantly longer runway; consideration should be given to engine shut-down earlier in the final approach; even as early as when abeam the numbers. Although an event like this is rare; it is recommended that it be discussed in private pilot training. Finally; there is speculation as to the missing cotter key on the throttle cable nut. Three options come to mind: the key sheared off; it vibrated out; or it was not inserted on the aircraft's annual inspection. The former two possibilities are highly unlikely; leaving the most likely reason for the missing cotter key being its omission on the previous annual inspection; completed ten month earlier.

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Original NASA ASRS Text

Title: C172 pilot reports throttle stuck at full power at 2500 FT. A power on approach is made with gear down and 10 degrees of flaps at 115 KTS. Engine was shutdown on short final and touch down occurred at 105 KTS. Aircraft could not be stopped on 3000 FT runway and ends up on public road with minimal damage and no injuries.

Narrative: Upon initial descent for approach to destination airport; when throttle was pulled back; there was no response in manifold pressure. Gauges indicated full throttle. Cycling of throttle gave no change; throttle was stuck at full. PIC engaged spouse (also a private pilot) to maximize crew resource management. PIC's spouse examined operator's manual for emergency procedure for loss of throttle control at full power. No procedure exists. Troubleshooting by PIC and ensuing discussion with spouse resulted in a plan for landing as safely as possible. Gear was dropped and 10 degrees of flaps extended; resulting in an airspeed of 115 KIAS. (Normal landing speed is 65 KIAS.) Further flaps could not be used due to speed in excess of 100 KIAS. Radio call to airport UNICOM at 15 miles out for field advisory and again at 5 miles out to alert to intent for wide pattern and low angle fast approach. Low angle approach decision in attempt to minimize any additional airspeed. Airport advisory indicated right quarter crosswind 6 KTS gusting to 15 KTS. In pattern calls were made to alert any other traffic. Runway length 3000 FT; more than three times normal landing roll (at 65 KIAS) was felt to be adequate. Planned alternate field runway was also only 3300 FT. Other airports were not considered since it was unknown how much more quickly fuel was being consumed at full throttle. Nearest potential runways significantly longer than 3000 FT not involved Class B airspace or more highly congested residential areas were felt to be possibly out of range for more than one attempted approach due to maximum fuel consumption rate. Decision to maintain engine power as long as possible (rather than early shutdown and use of gliding landing due to: 1) congested residential area and rising terrain beneath pattern and final approach; and 2) minimize risk of crash landing by maintaining the option for a go-around. Two approaches attempted with prop RPM backed off maximum possible and engine was shut off on final approach when field was considered made. Immediately upon touch-down (105 KIAS) flaps were retracted and yoke was pushed forward with slight aileron deflection due to crosswind. Due to speed and resulting lift; brakes did not have maximum effectiveness; this made even braking extremely difficult and possibility for ground loop. When approaching end of runway; decision was made to veer to grass to assist slowing aircraft as there was a road; a jogging/bicycle trail; and a gravel pit just beyond the end of the runway; in that order. Taxiway light was struck by slowing; spinning prop as aircraft exited runway. Grass slowed aircraft significantly but aircraft continued to climb embankment onto road. The PIC looked both ways; and traffic was observed to be already stopped in both directions. Maximum braking applied once of road resulting in aircraft coming to rest with nose gear just off pavement onto gravel shoulder opposite or runway; main gear were still on the road pavement. PIC immediately set brakes and exited aircraft to control traffic after ensuring other two aircraft occupants were without injury. Airport personnel were immediately on the scene to assist in rolling aircraft back to taxiway for towing to FBO. Local police and fire were on scene within five to ten minutes. There were no injuries to three occupants of aircraft; nor anybody on the ground. The only damage on the ground was the single taxiway light. Due to prop strike to taxiway light; prop must be replaced and engine torn down for inspection. Once towed to FBO; aircraft A&P removed cowling to examine throttle cable. The nut on the bolt holding the end of the throttle cable was missing; and there was no cotter key to hold the nut in place. The result was the throttle cable coming completely disconnected from the throttle; with spring holding throttle in full power position. Further considerations: A full throttle landing is not taught nor practiced nor considered in training. Nor is it covered in the owner's manual. The procedures in this case were; literally; invented on the fly. Three times normal landing distance was inadequate in this scenario; due to the lift generated by excessive landing speed and brake ineffectiveness. Divert to a runway at least five times; or even perhaps six times landing distance is suggested if possible; this can be a difficult decision when fuel flow rate is unknown and potentially significantly greater than normal. Also; decision was made in this case to keep engine running due to heavily populated area to approach end of runway; in an attempt to avoid misjudged distance and crash landing short among houses or on rising terrain leading to approach end of runway; as well as giving option for a go-around if necessary - as it was twice in this scenario. Ideally; in less populated area with significantly longer runway; consideration should be given to engine shut-down earlier in the final approach; even as early as when abeam the numbers. Although an event like this is rare; it is recommended that it be discussed in private pilot training. Finally; there is speculation as to the missing cotter key on the throttle cable nut. Three options come to mind: the key sheared off; it vibrated out; or it was not inserted on the aircraft's annual inspection. The former two possibilities are highly unlikely; leaving the most likely reason for the missing cotter key being its omission on the previous annual inspection; completed ten month earlier.

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.