Narrative:

At approximately XA00 hours (local time) while on a localizer approach to runway 34 at ZZZ, I deviated from the instrument approach procedure due to gyro instrument failure (vacuum) which caused some disorientation on my part. While on a flight from ZZZ1 to ZZZ, I chose to make a localizer approach into runway 34 at drake field. I was on localizer, a little below the GS about 1 mi from the touchdown zone. My wife (passenger) was looking out the windows to see ground (we were in the clouds). My wife hollered 'trees.' I was watching the aircraft instruments. Upon her exclamation, I gave full throttle and pulled back on the yoke. I heard the noise of scraping tree tops on the aircraft. I looked back at my instruments and the aircraft attitude indicator had tumbled and my directional gyro was spinning to the right and taking the aircraft with it. I disconnected the autoplt and gave left aileron and kept climbing. I turned on the aircraft's back-up vacuum and used the aircraft bank and turn coordinator and altitude indicator to continue a straight climb out. I contacted tower and declared a missed approach. Tower turned me back over to approach. Approach asked my heading. I informed approach I did not know my heading because I had a loss of vacuum pressure. Approach told me to keep wings level and continue climbing to 5000 ft, which I did. After a while, the aircraft's attitude indicator and directional gyro began working correctly with the auxiliary back-up. I informed approach that I had hit the tree tops on my approach and that the aircraft's instruments were now working correctly. I turned off the back-up vacuum and the vacuum stayed up on original vacuum. (I had just had a new vacuum pump installed 3 days prior to this incident.) I was vectored by approach to ZZZ2 with a fly-by of the tower to check to insure the aircraft gear were down. I had raised the gear on missed approach and had lowered them again on approach to ZZZ2. Tower informed me that the gear appeared to be down, but that fire apparatus personnel said the left one appeared to be not completely down. I informed tower that I would make a slow and soft landing, which I did successfully. I taxied to the FBO and a mechanic looked at the gear and said they were not damaged and that the aircraft, in his opinion, was airworthy. He removed some tree limbs and leaves from the gear but insisted that there was no damage to the gear. The 2 far (outboard) panels of the right wing were damaged by the encounter with the tree tops. Callback conversation with reporter revealed the following information: reporter states that there was no instrument failure prior to the time that he added power and commenced climbing after striking the tree tops. He stated that he was just too low and that it won't happen again because he will err on the high side from now on. He also stated that he was not sure about his altitude and distance at the time the aircraft struck the trees, but that it may have been more than 1 mi out and was certainly below 600 ft. Reporter states that the WX was reported as 1700 ft broken when he started the approach but that, during the approach, he was advised that the ceiling had dropped to 300 ft overcast with 2-3 mi visibility in rain. He states that he elected to continue the approach. Reporter states that a mechanic checked both vacuum system after the flight and that there was nothing wrong with their operation and he was unable to duplicate the problem experienced in-flight.

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Original NASA ASRS Text

Title: M20 PLT STRIKES TREE TOPS ON LDA DME APCH AND EXPERIENCES PRIMARY VACUUM SYS FAILURE ON MISSED APCH.

Narrative: AT APPROX XA00 HRS (LCL TIME) WHILE ON A LOC APCH TO RWY 34 AT ZZZ, I DEVIATED FROM THE INST APCH PROC DUE TO GYRO INST FAILURE (VACUUM) WHICH CAUSED SOME DISORIENTATION ON MY PART. WHILE ON A FLT FROM ZZZ1 TO ZZZ, I CHOSE TO MAKE A LOC APCH INTO RWY 34 AT DRAKE FIELD. I WAS ON LOC, A LITTLE BELOW THE GS ABOUT 1 MI FROM THE TOUCHDOWN ZONE. MY WIFE (PAX) WAS LOOKING OUT THE WINDOWS TO SEE GND (WE WERE IN THE CLOUDS). MY WIFE HOLLERED 'TREES.' I WAS WATCHING THE ACFT INSTS. UPON HER EXCLAMATION, I GAVE FULL THROTTLE AND PULLED BACK ON THE YOKE. I HEARD THE NOISE OF SCRAPING TREE TOPS ON THE ACFT. I LOOKED BACK AT MY INSTS AND THE ACFT ATTITUDE INDICATOR HAD TUMBLED AND MY DIRECTIONAL GYRO WAS SPINNING TO THE R AND TAKING THE ACFT WITH IT. I DISCONNECTED THE AUTOPLT AND GAVE L AILERON AND KEPT CLBING. I TURNED ON THE ACFT'S BACK-UP VACUUM AND USED THE ACFT BANK AND TURN COORDINATOR AND ALT INDICATOR TO CONTINUE A STRAIGHT CLBOUT. I CONTACTED TWR AND DECLARED A MISSED APCH. TWR TURNED ME BACK OVER TO APCH. APCH ASKED MY HDG. I INFORMED APCH I DID NOT KNOW MY HDG BECAUSE I HAD A LOSS OF VACUUM PRESSURE. APCH TOLD ME TO KEEP WINGS LEVEL AND CONTINUE CLBING TO 5000 FT, WHICH I DID. AFTER A WHILE, THE ACFT'S ATTITUDE INDICATOR AND DIRECTIONAL GYRO BEGAN WORKING CORRECTLY WITH THE AUX BACK-UP. I INFORMED APCH THAT I HAD HIT THE TREE TOPS ON MY APCH AND THAT THE ACFT'S INSTS WERE NOW WORKING CORRECTLY. I TURNED OFF THE BACK-UP VACUUM AND THE VACUUM STAYED UP ON ORIGINAL VACUUM. (I HAD JUST HAD A NEW VACUUM PUMP INSTALLED 3 DAYS PRIOR TO THIS INCIDENT.) I WAS VECTORED BY APCH TO ZZZ2 WITH A FLY-BY OF THE TWR TO CHK TO INSURE THE ACFT GEAR WERE DOWN. I HAD RAISED THE GEAR ON MISSED APCH AND HAD LOWERED THEM AGAIN ON APCH TO ZZZ2. TWR INFORMED ME THAT THE GEAR APPEARED TO BE DOWN, BUT THAT FIRE APPARATUS PERSONNEL SAID THE L ONE APPEARED TO BE NOT COMPLETELY DOWN. I INFORMED TWR THAT I WOULD MAKE A SLOW AND SOFT LNDG, WHICH I DID SUCCESSFULLY. I TAXIED TO THE FBO AND A MECH LOOKED AT THE GEAR AND SAID THEY WERE NOT DAMAGED AND THAT THE ACFT, IN HIS OPINION, WAS AIRWORTHY. HE REMOVED SOME TREE LIMBS AND LEAVES FROM THE GEAR BUT INSISTED THAT THERE WAS NO DAMAGE TO THE GEAR. THE 2 FAR (OUTBOARD) PANELS OF THE R WING WERE DAMAGED BY THE ENCOUNTER WITH THE TREE TOPS. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THAT THERE WAS NO INST FAILURE PRIOR TO THE TIME THAT HE ADDED PWR AND COMMENCED CLBING AFTER STRIKING THE TREE TOPS. HE STATED THAT HE WAS JUST TOO LOW AND THAT IT WON'T HAPPEN AGAIN BECAUSE HE WILL ERR ON THE HIGH SIDE FROM NOW ON. HE ALSO STATED THAT HE WAS NOT SURE ABOUT HIS ALT AND DISTANCE AT THE TIME THE ACFT STRUCK THE TREES, BUT THAT IT MAY HAVE BEEN MORE THAN 1 MI OUT AND WAS CERTAINLY BELOW 600 FT. RPTR STATES THAT THE WX WAS RPTED AS 1700 FT BROKEN WHEN HE STARTED THE APCH BUT THAT, DURING THE APCH, HE WAS ADVISED THAT THE CEILING HAD DROPPED TO 300 FT OVCST WITH 2-3 MI VISIBILITY IN RAIN. HE STATES THAT HE ELECTED TO CONTINUE THE APCH. RPTR STATES THAT A MECH CHKED BOTH VACUUM SYS AFTER THE FLT AND THAT THERE WAS NOTHING WRONG WITH THEIR OP AND HE WAS UNABLE TO DUPLICATE THE PROB EXPERIENCED INFLT.

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.