Narrative:

I departed a local airport (wst/westerly, ri) bound for gon (groton/new london, ct). Departing wst I contacted providence approach, as local rules dictate, to request the 'practice' ILS-5 approach into gon. I was given radar vectors to final approach and once 3.5 mi outside of pinet, the FAF, I was cleared for the approach and told to contact tower. I contacted tower when told to do so, and tower told me to report pinet intersection inbound. I acknowledged this request, and that was the tower's last understandable transmission. At pinet I contacted tower and heard 'garble' as a reply, so I told tower they were 'garbled' and 'unreadable.' this occurred twice, once at pinet and once approximately 30 seconds later. I then updated my position reports on tower frequency approximately every mi, and 'short final,' until touchdown. Pinet is approximately 6 mi out and I twice received light signals from tower. The same light signals were given twice. The signal was a very quick green flash followed by a very quick white flash. 1 signal occurred at approximately 5 mi out and the other at approximately 3.5-4 mi out. When I was approximately 2 mi out, I requested a steady green signal from tower if cleared to land. I never received any further acknowledgement. Even though I was not cleared to land properly from tower, I did land because I was confused with tower's light gun signals. The alternating green/white is not a signal known to FARS or local custom. I therefore assumed 1 or 2 things: there is traffic ahead and I shall get a steady green shortly. -- Or -- I am cleared to land. Providence approach was aware this was a full stop and I assumed this information was passed to tower. Long and short: the tower's confusing light signals made for a hectic situation when it could have been handled smoothly with proper light gun signals.

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Original NASA ASRS Text

Title: SMA ON FINAL RECEIVED GARBLED COM. SO STATES, THEN RECEIVES VERY CONFUSING LIGHT SIGNALS.

Narrative: I DEPARTED A LCL ARPT (WST/WESTERLY, RI) BOUND FOR GON (GROTON/NEW LONDON, CT). DEPARTING WST I CONTACTED PROVIDENCE APCH, AS LCL RULES DICTATE, TO REQUEST THE 'PRACTICE' ILS-5 APCH INTO GON. I WAS GIVEN RADAR VECTORS TO FINAL APCH AND ONCE 3.5 MI OUTSIDE OF PINET, THE FAF, I WAS CLRED FOR THE APCH AND TOLD TO CONTACT TWR. I CONTACTED TWR WHEN TOLD TO DO SO, AND TWR TOLD ME TO RPT PINET INTXN INBOUND. I ACKNOWLEDGED THIS REQUEST, AND THAT WAS THE TWR'S LAST UNDERSTANDABLE XMISSION. AT PINET I CONTACTED TWR AND HEARD 'GARBLE' AS A REPLY, SO I TOLD TWR THEY WERE 'GARBLED' AND 'UNREADABLE.' THIS OCCURRED TWICE, ONCE AT PINET AND ONCE APPROX 30 SECONDS LATER. I THEN UPDATED MY POS RPTS ON TWR FREQ APPROX EVERY MI, AND 'SHORT FINAL,' UNTIL TOUCHDOWN. PINET IS APPROX 6 MI OUT AND I TWICE RECEIVED LIGHT SIGNALS FROM TWR. THE SAME LIGHT SIGNALS WERE GIVEN TWICE. THE SIGNAL WAS A VERY QUICK GREEN FLASH FOLLOWED BY A VERY QUICK WHITE FLASH. 1 SIGNAL OCCURRED AT APPROX 5 MI OUT AND THE OTHER AT APPROX 3.5-4 MI OUT. WHEN I WAS APPROX 2 MI OUT, I REQUESTED A STEADY GREEN SIGNAL FROM TWR IF CLRED TO LAND. I NEVER RECEIVED ANY FURTHER ACKNOWLEDGEMENT. EVEN THOUGH I WAS NOT CLRED TO LAND PROPERLY FROM TWR, I DID LAND BECAUSE I WAS CONFUSED WITH TWR'S LIGHT GUN SIGNALS. THE ALTERNATING GREEN/WHITE IS NOT A SIGNAL KNOWN TO FARS OR LCL CUSTOM. I THEREFORE ASSUMED 1 OR 2 THINGS: THERE IS TFC AHEAD AND I SHALL GET A STEADY GREEN SHORTLY. -- OR -- I AM CLRED TO LAND. PROVIDENCE APCH WAS AWARE THIS WAS A FULL STOP AND I ASSUMED THIS INFO WAS PASSED TO TWR. LONG AND SHORT: THE TWR'S CONFUSING LIGHT SIGNALS MADE FOR A HECTIC SIT WHEN IT COULD HAVE BEEN HANDLED SMOOTHLY WITH PROPER LIGHT GUN SIGNALS.

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.