ACFT EQUIP PROB -- BI-PLANE PLT LOSES PART OF 1 PROP BLADE AND THEN MAKES AN EMER LNDG.

Narrative

DURING CRUISE WBOUND AT 3500 FT MSL I HEARD A LOUD BANG. THE ACFT STARTED TO VIOLENTLY VIBRATE. I PULLED BACK THE THROTTLE THEN TURNED OFF THE SWITCH TO GND THE MAGNETOS STOPPING THE ENG. THE VIBRATION CONTINUED SO I PULLED THE NOSE UP UNTIL THE PROP STOPPED TURNING. THE VIBRATION STOPPED. I THEN MADE A PRECAUTIONARY LNDG IN A HAY FIELD. UPON INSPECTION I FOUND THAT THE AIR INTAKE SCOOP BRACKET HAD BROKEN; HIT THE PROP; AND THAT THE PROP HAD LOST ABOUT 11 1/2 INCHES OFF ONE END. THE LNDG CAUSED NO DAMAGE TO THE ACFT; THE FIELD OR ANY PERSON. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE PLT WAS FLYING A WACO UPF-7 WHEN THE AIR INTAKE SCOOP SUPPORT ROD ON THE R SIDE OF THE SCOOP BROKE AND STRUCK THE PROP. THE METAL PROP THEN PULLED THE REMAINDER OF THE SCOOP FORWARD SEPARATING IT FROM THE ACFT AND BREAKING 11 1/2 INCHES FROM ONE OF THE PROP BLADES. THE RESULTING VIBRATION CAUSED MORE DAMAGE TO THE ENG AND ITS MOUNTS. THE RPTR SAID THAT HE WAS UNABLE TO SEE HIS INSTS UNTIL HE COULD GET THE PROP STOPPED. THE AIRFRAME ALSO NEEDS TO BE INSPECTED AND HIS HULL INSURANCE COMPANY HAS AGREED TO AN EXTENSIVE REPAIR PROGRAM.