Narrative:

On mar/sun/97, I observed a commuter aircraft descend below published minimum altitude to approach minimums outside the OM (final approach fix) in instrument WX conditions (ceiling 700 ft overcast, visibility 2 mi). I have observed similar occurrences (descent below published minimum altitude, 2600 ft) outside the (OM) final approach fix on approximately 2 dozen occasions. Problem description: the akr airport is located approximately 7 mi n-nw of the akron canton airport. The akr airport has a localizer runway 25 and an NDB runway 25 approach. One component of these approachs is the akr outer compass locator (LOM), co- located non-directional beacon and 75 MHZ OM, located slightly east of the akron canton ILS runway 19 localizer and approximately 5 mi n-ne of the derby OM (see attached approach plates and chart). It appears that occasionally aircraft on the ILS runway 19 approach to akron canton receive an OM indication (flashing blue light, aural tone) from the akr LOM approximately 5 mi north of the derby OM and erroneously commence descent at this point, approximately 5 mi prematurely. In addition to terrain and obstruction clearance considerations, this premature descent also causes the aircraft to penetrate the traffic pattern at the akron fulton airport. In the last occurrence, the aircraft was approximately 900 ft below the published minimum altitude for crossing the final approach fix (derby OM). In essence, the aircraft descended to approach minimums outside the final approach fix. When questioned by myself, the pilot reported that he had received 2 separate OM indications. I have observed approximately 2 dozen similar occurrences in the last 4 yrs. I believe that they were all due to the reception of the OM signal from the akr outer compass locator, which is interpreted as the derby OM signal. The OM signals and indications are identical and are not idented. I believe that consideration should be given to decommissioning the OM portion of the akr outer compass locator to prevent a reoccurrence of this situation. Callback conversation with reporter revealed the following information: reporter stated that the system was flight checked about a yr ago and everything was reported to operations normally. Reporter indicated a note was added to the approach plate about receiving the OM. Reporter said he has observed 2 GA aircraft back to back on approach begin the early descent. Reporter feels the problem occurs as a result of some unusual combination of events and to no particular aircraft type or equipment. Reporter is unaware of plans to make any changes to this problem. Reporter reiterated his feeling that the OM for the other airport should be shut down since there are other ways to identify the final approach fix for that airport. Reporter indicated the airport is non twred and the approach is used primarily for practice approachs.

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Original NASA ASRS Text

Title: RPTED SIT OF A COMMUTER ACFT MAKING EARLY DSCNT ON THE ILS RWY 19 APCH PRIOR TO THE OM. ACFT MAY BE PICKING UP THE OM FOR AN ADJACENT ARPT. PLTDEV.

Narrative: ON MAR/SUN/97, I OBSERVED A COMMUTER ACFT DSND BELOW PUBLISHED MINIMUM ALT TO APCH MINIMUMS OUTSIDE THE OM (FINAL APCH FIX) IN INST WX CONDITIONS (CEILING 700 FT OVCST, VISIBILITY 2 MI). I HAVE OBSERVED SIMILAR OCCURRENCES (DSCNT BELOW PUBLISHED MINIMUM ALT, 2600 FT) OUTSIDE THE (OM) FINAL APCH FIX ON APPROX 2 DOZEN OCCASIONS. PROB DESCRIPTION: THE AKR ARPT IS LOCATED APPROX 7 MI N-NW OF THE AKRON CANTON ARPT. THE AKR ARPT HAS A LOC RWY 25 AND AN NDB RWY 25 APCH. ONE COMPONENT OF THESE APCHS IS THE AKR OUTER COMPASS LOCATOR (LOM), CO- LOCATED NON-DIRECTIONAL BEACON AND 75 MHZ OM, LOCATED SLIGHTLY E OF THE AKRON CANTON ILS RWY 19 LOC AND APPROX 5 MI N-NE OF THE DERBY OM (SEE ATTACHED APCH PLATES AND CHART). IT APPEARS THAT OCCASIONALLY ACFT ON THE ILS RWY 19 APCH TO AKRON CANTON RECEIVE AN OM INDICATION (FLASHING BLUE LIGHT, AURAL TONE) FROM THE AKR LOM APPROX 5 MI N OF THE DERBY OM AND ERRONEOUSLY COMMENCE DSCNT AT THIS POINT, APPROX 5 MI PREMATURELY. IN ADDITION TO TERRAIN AND OBSTRUCTION CLRNC CONSIDERATIONS, THIS PREMATURE DSCNT ALSO CAUSES THE ACFT TO PENETRATE THE TFC PATTERN AT THE AKRON FULTON ARPT. IN THE LAST OCCURRENCE, THE ACFT WAS APPROX 900 FT BELOW THE PUBLISHED MINIMUM ALT FOR XING THE FINAL APCH FIX (DERBY OM). IN ESSENCE, THE ACFT DSNDED TO APCH MINIMUMS OUTSIDE THE FINAL APCH FIX. WHEN QUESTIONED BY MYSELF, THE PLT RPTED THAT HE HAD RECEIVED 2 SEPARATE OM INDICATIONS. I HAVE OBSERVED APPROX 2 DOZEN SIMILAR OCCURRENCES IN THE LAST 4 YRS. I BELIEVE THAT THEY WERE ALL DUE TO THE RECEPTION OF THE OM SIGNAL FROM THE AKR OUTER COMPASS LOCATOR, WHICH IS INTERPRETED AS THE DERBY OM SIGNAL. THE OM SIGNALS AND INDICATIONS ARE IDENTICAL AND ARE NOT IDENTED. I BELIEVE THAT CONSIDERATION SHOULD BE GIVEN TO DECOMMISSIONING THE OM PORTION OF THE AKR OUTER COMPASS LOCATOR TO PREVENT A REOCCURRENCE OF THIS SIT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT THE SYS WAS FLT CHKED ABOUT A YR AGO AND EVERYTHING WAS RPTED TO OPS NORMALLY. RPTR INDICATED A NOTE WAS ADDED TO THE APCH PLATE ABOUT RECEIVING THE OM. RPTR SAID HE HAS OBSERVED 2 GA ACFT BACK TO BACK ON APCH BEGIN THE EARLY DSCNT. RPTR FEELS THE PROB OCCURS AS A RESULT OF SOME UNUSUAL COMBINATION OF EVENTS AND TO NO PARTICULAR ACFT TYPE OR EQUIP. RPTR IS UNAWARE OF PLANS TO MAKE ANY CHANGES TO THIS PROB. RPTR REITERATED HIS FEELING THAT THE OM FOR THE OTHER ARPT SHOULD BE SHUT DOWN SINCE THERE ARE OTHER WAYS TO IDENT THE FINAL APCH FIX FOR THAT ARPT. RPTR INDICATED THE ARPT IS NON TWRED AND THE APCH IS USED PRIMARILY FOR PRACTICE APCHS.

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.