Barry Bennett
Member
- Joined
- Sep 17, 2018
- Messages
- 22
- Reaction score
- 3
I own a 1975 PA 28R 200 (Arrow II) and 2 days ago I took off to fly 4 practice instrument approaches from KSEE in San Diego Class Bravo. Weather was VFR inland but there was a marine layer along the coast that topped around 2100’ MSL. Everything checked out during pre-flight and run-up so I departed to the west and was immediately vectored to intercept the ILS into KMYF. I shot the approach, went missed and was cleared direct to hold at OCN prior to the VOR-A approach into KOKB.
About the time I reached the coast above a solid marine layer, the VAC light on the panel came on and my vacuum/suction gauge dropped to zero.
I was VFR on top and flying with the TruTrack autopilot slaved to the Garmin 430 WAAS so this was not an emergency situation. I then pulled the handle to activate the Precise SVS II stand by vacuum system. The needle on the suction gauge immediately went up to 4.5 inches of mercury but after less than a minute, dropped back to zero.
I returned to my home base with incident and the aircraft is now in the hands of my A&P but wanted to share my experience and a few thoughts I have on this.
I have always had terrible luck but the odds of the primary and stand by vacuum systems failing at the same time are too phenomenal to accept. I am not familiar with the routing of the vacuum lines or whether the hoses for the two are merged into one hose that goes to the panel but initially, that‘s what I suspected and figured there is a Y coupling that failed or disconnected from the line leading to the panel.
After I got home, I researched the system and discovered there have been cases of this stand-by system failing due to failed shuttle control valves. I then read comments from pilots stating the system will only function at 2100 RPM‘s or less and the lower the RPM’s, the better it works. I had no idea and the thought of having to pull power to drop the RPM’s after a vacuum failure in IMC isn’t my idea of a good time.
I also found two separate Airworthiness Directives ( 99-24-10 and 2005-11-05 ) that MAY pertain to my AC. I say “may” because I am not sure of the exact model of Precise system I have. AD 99-24-10 calls for an update to the Aircraft Flight Manual/POH, and repetitive inspections of the components. AD 2005-11-05 requires an update to the supplement in the Aircraft Flight Manual /POH and the installation of placard(s). I need to research my AC logbooks to check for inspections but it doesn’t appear my previous A&P was aware of these AD’s because I do not have a placard as required.
I’ve been flying since 1984 and this was my first ever vacuum failure. I’m glad it happened while VFR because I got a little partial panel experience, realized the approach certified WAAS GPS and autopilot was worth ever penny and discovered discrepancies that should have been corrected years ago.
If any of you have similar systems in your AC, I recommend checking to ensure any applicable AD’s have been complied with.
About the time I reached the coast above a solid marine layer, the VAC light on the panel came on and my vacuum/suction gauge dropped to zero.
I was VFR on top and flying with the TruTrack autopilot slaved to the Garmin 430 WAAS so this was not an emergency situation. I then pulled the handle to activate the Precise SVS II stand by vacuum system. The needle on the suction gauge immediately went up to 4.5 inches of mercury but after less than a minute, dropped back to zero.
I returned to my home base with incident and the aircraft is now in the hands of my A&P but wanted to share my experience and a few thoughts I have on this.
I have always had terrible luck but the odds of the primary and stand by vacuum systems failing at the same time are too phenomenal to accept. I am not familiar with the routing of the vacuum lines or whether the hoses for the two are merged into one hose that goes to the panel but initially, that‘s what I suspected and figured there is a Y coupling that failed or disconnected from the line leading to the panel.
After I got home, I researched the system and discovered there have been cases of this stand-by system failing due to failed shuttle control valves. I then read comments from pilots stating the system will only function at 2100 RPM‘s or less and the lower the RPM’s, the better it works. I had no idea and the thought of having to pull power to drop the RPM’s after a vacuum failure in IMC isn’t my idea of a good time.
I also found two separate Airworthiness Directives ( 99-24-10 and 2005-11-05 ) that MAY pertain to my AC. I say “may” because I am not sure of the exact model of Precise system I have. AD 99-24-10 calls for an update to the Aircraft Flight Manual/POH, and repetitive inspections of the components. AD 2005-11-05 requires an update to the supplement in the Aircraft Flight Manual /POH and the installation of placard(s). I need to research my AC logbooks to check for inspections but it doesn’t appear my previous A&P was aware of these AD’s because I do not have a placard as required.
I’ve been flying since 1984 and this was my first ever vacuum failure. I’m glad it happened while VFR because I got a little partial panel experience, realized the approach certified WAAS GPS and autopilot was worth ever penny and discovered discrepancies that should have been corrected years ago.
If any of you have similar systems in your AC, I recommend checking to ensure any applicable AD’s have been complied with.
