|37000 Feet||Browse and search NASA's
Aviation Safety Reporting System
|Local Time Of Day||0601 To 1200|
|Locale Reference||atc facility : iah|
|Altitude||agl bound lower : 0|
agl bound upper : 0
|Operator||common carrier : air carrier|
|Make Model Name||Medium Large Transport, Low Wing, 2 Turbojet Eng|
|Affiliation||company : air carrier|
|Function||flight crew : captain|
oversight : pic
|Qualification||pilot : atp|
|Experience||flight time last 90 days : 200|
flight time total : 5000
|Anomaly||other anomaly other|
|Independent Detector||other flight crewa|
|Resolutory Action||none taken : anomaly accepted|
|Consequence||faa : reviewed incident with flight crew|
|Air Traffic Incident||other|
The medium large transport has a nasty detent in the throttle quadrant at +/- 15% above idle (power lever position). Two potential problems: 1) pilot may believe he is operating in idle while in effect he is not. 2) during landing roll, pilot will not be able to activate reversers until he realizes he is not in idle power. Asking around, nobody is able to explain why the detent is there in the first place. A typical airline pilot may operate both medium large transport series. The older medium large transport does not have the detent. Suggestion: eliminate detent in the throttle quadrant of the medium large transport. Callback conversation with reporter revealed the following: advised reporter this was an original design feature to insure the engine would spool up rapidly on a go around. Was later found that the engine could meet the certification requirements when allowed to go to ground idle. Apparently the model aircraft they are operating were modified at some time and this quadrant was installed. ASRS is not in a position to do anything reference this problem, but suggested he take it up with his management.
Original NASA ASRS Text
Title: FLT IDLE DETENT ON THE THROTTLE QUADRANT GETS IN THE WAY AT TIMES, ESPECIALLY WHEN REVERSING SINCE GND IDLE IS REQUIRED TO REVERSE THE ENGINES.
Narrative: THE MLG HAS A NASTY DETENT IN THE THROTTLE QUADRANT AT +/- 15% ABOVE IDLE (PWR LEVER POS). TWO POTENTIAL PROBS: 1) PLT MAY BELIEVE HE IS OPERATING IN IDLE WHILE IN EFFECT HE IS NOT. 2) DURING LNDG ROLL, PLT WILL NOT BE ABLE TO ACTIVATE REVERSERS UNTIL HE REALIZES HE IS NOT IN IDLE PWR. ASKING AROUND, NOBODY IS ABLE TO EXPLAIN WHY THE DETENT IS THERE IN THE FIRST PLACE. A TYPICAL AIRLINE PLT MAY OPERATE BOTH MLG SERIES. THE OLDER MLG DOES NOT HAVE THE DETENT. SUGGESTION: ELIMINATE DETENT IN THE THROTTLE QUADRANT OF THE MLG. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: ADVISED RPTR THIS WAS AN ORIGINAL DESIGN FEATURE TO INSURE THE ENG WOULD SPOOL UP RAPIDLY ON A GO AROUND. WAS LATER FOUND THAT THE ENG COULD MEET THE CERTIFICATION REQUIREMENTS WHEN ALLOWED TO GO TO GND IDLE. APPARENTLY THE MODEL ACFT THEY ARE OPERATING WERE MODIFIED AT SOME TIME AND THIS QUADRANT WAS INSTALLED. ASRS IS NOT IN A POS TO DO ANYTHING REF THIS PROB, BUT SUGGESTED HE TAKE IT UP WITH HIS MGMNT.
Data retrieved from NASA's ASRS site as of August 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.