GA twin taxied over a recessed drain and the right propeller hit the ground.

Attributes
ACN	196578
Time
Date	199112
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : lgb
State Reference	CA
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : sfo
Operator	general aviation : instructional
Make Model Name	Small Aircraft, Low Wing, 2 Eng, Retractable Gear
Flight Phase	ground other : taxi
Flight Plan	VFR
Person 1
Affiliation	Other
Function	instruction : instructor
Qualification	pilot : cfi
Experience	flight time last 90 days : 120 flight time total : 1380 flight time type : 20
ASRS Report	196578
Person 2
Affiliation	Other
Function	instruction : trainee
Qualification	pilot : private
Events
Anomaly	other anomaly other
Independent Detector	other flight crewa
Resolutory Action	none taken : detected after the fact
Consequence	other
Supplementary
Primary Problem	Airport
Air Traffic Incident	other
Situations
Airport	other physical facility

Narrative:

While taxiing back to the FBO my student adjusted to the right for an aircraft outbound from the flying school. Both aircraft were in communications with ground control. As we adjusted to the right but still on the taxiway we taxied over a (sewer) drain and in the process the right propeller contacted the ground taking off 1/4 inch of propeller tip. Apparently the drain was recessed enough so that the propeller clearance was reduced causing the propeller strike. In the future I will be careful not to taxi over any drains or uneven terrain even if it is on a taxiway. I incorrectly assumed that because the drain was on a navigable taxiway it would have been constructed to tolerances allowing such clearance.

Original NASA ASRS Text

Title: GA TWIN TAXIED OVER A RECESSED DRAIN AND THE R PROP HIT THE GND.

Narrative: WHILE TAXIING BACK TO THE FBO MY STUDENT ADJUSTED TO THE R FOR AN ACFT OUTBOUND FROM THE FLYING SCHOOL. BOTH ACFT WERE IN COMS WITH GND CTL. AS WE ADJUSTED TO THE R BUT STILL ON THE TAXIWAY WE TAXIED OVER A (SEWER) DRAIN AND IN THE PROCESS THE R PROP CONTACTED THE GND TAKING OFF 1/4 INCH OF PROP TIP. APPARENTLY THE DRAIN WAS RECESSED ENOUGH SO THAT THE PROP CLRNC WAS REDUCED CAUSING THE PROP STRIKE. IN THE FUTURE I WILL BE CAREFUL NOT TO TAXI OVER ANY DRAINS OR UNEVEN TERRAIN EVEN IF IT IS ON A TAXIWAY. I INCORRECTLY ASSUMED THAT BECAUSE THE DRAIN WAS ON A NAVIGABLE TAXIWAY IT WOULD HAVE BEEN CONSTRUCTED TO TOLERANCES ALLOWING SUCH CLRNC.

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.