Narrative:

A new turn coordinator had been installed in the aircraft, and I wanted to check the magnetic compass. I had been told that a compass rose was available on the airport at the north end of the airport ramp. I called the airport office at about XA30 local on jul/wed/98, to confirm that the compass rose was available, and received permission to use it. At about XB00 I taxied from the hangar to the east ramp and called lincoln ground with a request to taxi to the compass rose on the airport ramp. Ground control cleared me to taxi to the guard ramp where I was escorted to the compass rose by an airport 'follow-me' vehicle. The compass rose consisted of concrete segments arranged in a radial pattern from the center. At the exact center was a circular segment about 1 ft in diameter. The entire compass rose was crowned such that it was slightly higher at the center than at the edges. I approached the compass rose from the south, lined up on the n-s line of the rose, and taxied north along the line to assure accurate alignment between the aircraft and the compass rose. As I approached the center of the compass rose, I noticed the circular concrete segment at the exact center was lower than the adjacent segments and contained a pool of water. I judged the depth of water and total depth of the center segment to be 1/2 inch or less and safe to taxi across. As the nosewheel crossed the center segment, the nose of the aircraft dropped and I heard a faint, but distinct ching- ching as the propeller struck the concrete. I did not feel any vibration from the impact and engine RPM and performance was unaffected. Propeller noise changed slightly after the impact, but I did not notice any other changes. I continued to check the magnetic compass at other headings, but avoided the center segment on subsequent headings. When I had finished checking the compass, I contacted lincoln ground with a request to return to the east ramp. I was escorted from the compass rose to the end of the airport ramp by the airport follow-me vehicle. Lincoln ground then cleared me to the east ramp, and I returned to my hangar. At the time of the propeller strike, I suspected that damage to the propeller would be barely noticeable. However, when I examined the propeller at the hangar, damage to both tips was evident. 1 tip was straight, but had lost some metal, possibly 1/4 inch. The other tip was slightly bent and had lost more metal than the first tip, possibly as much as 1/2 inch. This problem was caused by a combination of my misjudgement of the depth of the center segment, and the somewhat deteriorated condition of the compass rose. It could also have been avoided by better awareness on my part of propeller clrncs and taxi hazards. It could have been avoided by better maintenance of the compass rose. Another consideration for safety is what I learned about propeller strikes. First, evidence that a strike has occurred can be remarkably small (only the faint, but distinct ching-ching sound). Second, my initial impression that damage would be barely noticeable was obviously mistaken. Callback conversation with reporter revealed the following information: pilot stated he had only reported the incident to his insurance agent located on lnk airport. He said the compass rose did not have any signs concerning usage. The pavement area at the compass rose where the incident occurred had about 1/2 inch of water and a very slight indentation on the center section. He said it did not appear damaged in any way. He also said the compass rose was not very large but big enough to accommodate an aircraft as big as a king air. This was his first experience using a compass rose and he does not know if its construction is nonstandard. He said there was almost no indication his propeller had struck the ground except for a slight 'ching' sound. Back at the hangar he found that his aircraft had sustained substantial damage to the propeller blades. The slight noise he heard would not have stopped him from taking off and considered himself lucky that he wasn't going out on a flight.

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Original NASA ASRS Text

Title: PLT AT LNK ARPT TAXIES TO COMPASS ROSE AND BECAUSE OF THE LAYOUT OF THE COMPASS ROSE AREA, THE ACFT'S PROP TOUCHES THE GND AND SUSTAINS DAMAGE.

Narrative: A NEW TURN COORDINATOR HAD BEEN INSTALLED IN THE ACFT, AND I WANTED TO CHK THE MAGNETIC COMPASS. I HAD BEEN TOLD THAT A COMPASS ROSE WAS AVAILABLE ON THE ARPT AT THE N END OF THE ARPT RAMP. I CALLED THE ARPT OFFICE AT ABOUT XA30 LCL ON JUL/WED/98, TO CONFIRM THAT THE COMPASS ROSE WAS AVAILABLE, AND RECEIVED PERMISSION TO USE IT. AT ABOUT XB00 I TAXIED FROM THE HANGAR TO THE E RAMP AND CALLED LINCOLN GND WITH A REQUEST TO TAXI TO THE COMPASS ROSE ON THE ARPT RAMP. GND CTL CLRED ME TO TAXI TO THE GUARD RAMP WHERE I WAS ESCORTED TO THE COMPASS ROSE BY AN ARPT 'FOLLOW-ME' VEHICLE. THE COMPASS ROSE CONSISTED OF CONCRETE SEGMENTS ARRANGED IN A RADIAL PATTERN FROM THE CTR. AT THE EXACT CTR WAS A CIRCULAR SEGMENT ABOUT 1 FT IN DIAMETER. THE ENTIRE COMPASS ROSE WAS CROWNED SUCH THAT IT WAS SLIGHTLY HIGHER AT THE CTR THAN AT THE EDGES. I APCHED THE COMPASS ROSE FROM THE S, LINED UP ON THE N-S LINE OF THE ROSE, AND TAXIED N ALONG THE LINE TO ASSURE ACCURATE ALIGNMENT BTWN THE ACFT AND THE COMPASS ROSE. AS I APCHED THE CTR OF THE COMPASS ROSE, I NOTICED THE CIRCULAR CONCRETE SEGMENT AT THE EXACT CTR WAS LOWER THAN THE ADJACENT SEGMENTS AND CONTAINED A POOL OF WATER. I JUDGED THE DEPTH OF WATER AND TOTAL DEPTH OF THE CTR SEGMENT TO BE 1/2 INCH OR LESS AND SAFE TO TAXI ACROSS. AS THE NOSEWHEEL CROSSED THE CTR SEGMENT, THE NOSE OF THE ACFT DROPPED AND I HEARD A FAINT, BUT DISTINCT CHING- CHING AS THE PROP STRUCK THE CONCRETE. I DID NOT FEEL ANY VIBRATION FROM THE IMPACT AND ENG RPM AND PERFORMANCE WAS UNAFFECTED. PROP NOISE CHANGED SLIGHTLY AFTER THE IMPACT, BUT I DID NOT NOTICE ANY OTHER CHANGES. I CONTINUED TO CHK THE MAGNETIC COMPASS AT OTHER HEADINGS, BUT AVOIDED THE CTR SEGMENT ON SUBSEQUENT HEADINGS. WHEN I HAD FINISHED CHKING THE COMPASS, I CONTACTED LINCOLN GND WITH A REQUEST TO RETURN TO THE E RAMP. I WAS ESCORTED FROM THE COMPASS ROSE TO THE END OF THE ARPT RAMP BY THE ARPT FOLLOW-ME VEHICLE. LINCOLN GND THEN CLRED ME TO THE E RAMP, AND I RETURNED TO MY HANGAR. AT THE TIME OF THE PROP STRIKE, I SUSPECTED THAT DAMAGE TO THE PROP WOULD BE BARELY NOTICEABLE. HOWEVER, WHEN I EXAMINED THE PROP AT THE HANGAR, DAMAGE TO BOTH TIPS WAS EVIDENT. 1 TIP WAS STRAIGHT, BUT HAD LOST SOME METAL, POSSIBLY 1/4 INCH. THE OTHER TIP WAS SLIGHTLY BENT AND HAD LOST MORE METAL THAN THE FIRST TIP, POSSIBLY AS MUCH AS 1/2 INCH. THIS PROB WAS CAUSED BY A COMBINATION OF MY MISJUDGEMENT OF THE DEPTH OF THE CTR SEGMENT, AND THE SOMEWHAT DETERIORATED CONDITION OF THE COMPASS ROSE. IT COULD ALSO HAVE BEEN AVOIDED BY BETTER AWARENESS ON MY PART OF PROP CLRNCS AND TAXI HAZARDS. IT COULD HAVE BEEN AVOIDED BY BETTER MAINT OF THE COMPASS ROSE. ANOTHER CONSIDERATION FOR SAFETY IS WHAT I LEARNED ABOUT PROP STRIKES. FIRST, EVIDENCE THAT A STRIKE HAS OCCURRED CAN BE REMARKABLY SMALL (ONLY THE FAINT, BUT DISTINCT CHING-CHING SOUND). SECOND, MY INITIAL IMPRESSION THAT DAMAGE WOULD BE BARELY NOTICEABLE WAS OBVIOUSLY MISTAKEN. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: PLT STATED HE HAD ONLY RPTED THE INCIDENT TO HIS INSURANCE AGENT LOCATED ON LNK ARPT. HE SAID THE COMPASS ROSE DID NOT HAVE ANY SIGNS CONCERNING USAGE. THE PAVEMENT AREA AT THE COMPASS ROSE WHERE THE INCIDENT OCCURRED HAD ABOUT 1/2 INCH OF WATER AND A VERY SLIGHT INDENTATION ON THE CTR SECTION. HE SAID IT DID NOT APPEAR DAMAGED IN ANY WAY. HE ALSO SAID THE COMPASS ROSE WAS NOT VERY LARGE BUT BIG ENOUGH TO ACCOMMODATE AN ACFT AS BIG AS A KING AIR. THIS WAS HIS FIRST EXPERIENCE USING A COMPASS ROSE AND HE DOES NOT KNOW IF ITS CONSTRUCTION IS NONSTANDARD. HE SAID THERE WAS ALMOST NO INDICATION HIS PROP HAD STRUCK THE GND EXCEPT FOR A SLIGHT 'CHING' SOUND. BACK AT THE HANGAR HE FOUND THAT HIS ACFT HAD SUSTAINED SUBSTANTIAL DAMAGE TO THE PROP BLADES. THE SLIGHT NOISE HE HEARD WOULD NOT HAVE STOPPED HIM FROM TAKING OFF AND CONSIDERED HIMSELF LUCKY THAT HE WASN'T GOING OUT ON A FLT.

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.