---------------------------------------------------------- RV-List Digest Archive --- Total Messages Posted Sun 06/29/14: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:00 PM - Re: 70 psi compression (Thomas Sargent) 2. 09:11 PM - Baggage Door Assembly and Lift Strut Install (Matt Dralle) ________________________________ Message 1 _____________________________________ Time: 07:00:13 PM PST US Subject: Re: RV-List: 70 psi compression From: Thomas Sargent I repeated the measurement myself this afternoon after running the engine until cyl. head temp hit 400 deg. (not hard when it's 105 outside). I got all cylinders between 73 and 76. The guy who did the first, obviously wrong,measurement is definitely an old hand, I don't know what went wrong - I wasn't watching - but something certainly did.. On Thu, Jun 26, 2014 at 3:28 PM, Charlie England wrote: > > Even if you buy into the idea that a compression test is required during > the condition inspection, it doesn't mean you have to give it any weight in > your appraisal of the engine's health. :-) I suspect that Bill was saying > that more recent research has shown the traditional compression test to be > a very poor indicator of a cylinder's condition (unless, of course, it's > very very low and you can hear a 'breeze' blowing out the exhaust or > intake...). > > I've gotten a 75+ reading on a cylinder that had a broken ring, and a > low-70s reading followed the next year by a high-70s reading on the same > cylinder, when checked 'cold'. > > If you haven't done it already, I'd suggest reading everything you can > find by Mike Busch (writes for Sport Aviation, in addition to seminars, > webinars, etc). > > Charlie > (If your mechanic insists that he got an 88/80 reading, then in the > immortal words of Monty Python, 'Run away! Run away!' (from that mechanic). > > > On 6/26/2014 2:26 PM, Kelly McMullen wrote: > >> >> Not really. Until Appendix D of Part 43 gets re-written, compression >> tests are mandatory for both certified and experimental aircraft. Item (d) >> (3) of the appendix requires compression test, and AFAIK most all >> experimental operating limitations require condition inspect that meets >> requirements of Appendix D as a minimum. Yes, borescope is good addition to >> checking cylinder health, but FAA does not recognize it as a complete >> substitute. >> IF one gains the experience to get a cylinder to TDC there will be no >> force on the prop. But allowing it to go very many degrees either side of >> TDC generates a dangerous force in the prop. I position prop near TDC, dial >> up about 20psi while adjusting prop for minimum to no force at the prop, >> then bring the pressure on up to 80. I also make sure to hold prop such >> that if it got away from me it would hurt nothing. Especially keep rest of >> body besides hand outside the prop arc.I don't even pick up compression >> tester until I have prop in safe position. >> >> On 6/26/2014 8:27 AM, Bill Boyd wrote: >> >>> Be careful. Two-man job to do safely... 80 psi into one jug can be >>> deadly if the prop gets away from you and your noggin is in the way. >>> >>> IIRC, the trend in the "literature" is away from compression testing >>> altogether and toward boroscopy as a means of assessing engine health. >>> --kind of like internal like medicine... the old standards of screening >>> are giving way to the $$ passing-of-scopes $$ into various body cavities. >>> >>> -Stormy >>> >>> >>> On Thu, Jun 26, 2014 at 10:46 AM, Thomas Sargent >> > wrote: >>> >>> Well 88 may well be a mistake, but that's what the A&P said. He >>> seemed a bit baffled. I have my own compression tester now. I >>> will do it myself next time. >>> >>> >>> On Wed, Jun 25, 2014 at 8:11 PM, Linn Walters >>> > wrote: >>> >>> On 6/25/2014 9:44 PM, vanremog@aol.com >>> wrote: >>> >>>> Just a wild question since no one has asked it...How can one >>>> get an 88 psig aircraft bleed down type compression reading >>>> with 80 psig supplied air? >>>> >>> You can't if you use the differential gauge properly. I can >>> only surmise that 88 was a typo. >>> Linn >>> >>>> -----Original Message----- >>>> From: William Greenley >>>> >>>> To: rv-list >>>> >>>> Sent: Wed, Jun 25, 2014 4:26 pm >>>> Subject: RE: RV-List: 70 psi compression >>>> >>>> An 88 means something is wrong with the equipment or the >>>> methodology. The max is 80 with the standardized orifice. >>>> *From:*owner-rv-list-server@matronics.com >>>> >>>> [mailto:owner-rv-list-server@matronics.com >>>> ] *On Behalf Of >>>> *Thomas Sargent >>>> *Sent:* Wednesday, June 25, 2014 7:11 PM >>>> *To:* rv-list >>>> *Subject:* Re: RV-List: 70 psi compression >>>> Thanks for all the good information. >>>> >>>> Reading the Lycoming Service instructions, I should note that >>>> cyl#1 showed 88psi. I was doing the test as part of the >>>> annual inspection. Last year they were all in the 72 - 78 >>>> range I think. What does an anomalously high reading >>>> indicate? Off hand I would have guessed that the higher the >>>> better, but apparently not. Lyc. says more than 15psi >>>> difference is trouble. >>>> >>>> I think I need to repeat this whole test soon after actually >>>> flying the plane. >>>> >>>> I'm still finishing the annual, I haven't flown it for a >>>> couple weeks. >>>> >>>> >>>> > > -- Tom Sargent ________________________________ Message 2 _____________________________________ Time: 09:11:10 PM PST US From: Matt Dralle Subject: RV-List: Baggage Door Assembly and Lift Strut Install Continuing the construction of the new, new baggage door for the RV-8, I worked on the hinge at the top and riveted the whole thing together. I am very happy to report that the fit of the door is nearly perfect! Frankly, it is pretty amazing that something made out of bent sheet metal could fit that well. But alas, I'm not complaining. I spent a fair amount of time and a couple of tries on the top hinge to get the bottom edge of the door to line up perfectly with the bottom of the top fuselage skin. The door comes down and lines up perfectly along both the front and back edges as well as along the bottom as previously described. I'm so happy I redid this baggage door no less than three times to finally get a perfect one! Such is that story of this project it seems... The stock front baggage door on the RV-8 doesn't come with any means of holding it open other than your arm. Since I'd already experienced what happens when the latch pins are in the "latched" position and the door suddenly slams shut (dents and scratches), I really wanted to find a nice strut of some kind that would hold the door open, yet be relatively easy to install/replace/use. Some browsing in the McMaster-Carr on-line catalog turned up what turn out to be the absolute *perfect* part for the job. The strut unit is made for tool box lids and has pre-installed mounts on each end that work perfectly on the RV-8 baggage door with no modifications whatsoever. Incredible, really. The best part is that in operation, the strut will securely hold the door open AND closed! Its amazing actually! At about 2" from closed the geometry of the system has nearly zero pressure open/closed and then at the last 1" or so, slightly pulls the door down. Note that the latch pins are still needed to hold the door securely closed. Conversely, after about 3" open, there is enough push in the spring to gently open the door all the way and then hold it open very nicely. If you have an RV-8 and want a baggage door strut, look no further. This is the just ticket: McMaster-Carr Part Number:11615A14 Here is the on-line web page for the part: http://www.mcmaster.com/#11615A14 At $53.00 (circa 2014) its a little pricey, but its stainless steel, a spring - not hydraulic, and did I mention - works PERFECTLY on the RV-8 front baggage door! Buy one now! Next up is mounting the nylon blocks for the latch pins. Who knew this baggage door would turn into such a project! - Matt Dralle RV-8 #82880 N998RV "Ruby Vixen" http://www.mattsrv8.com - Matt's Complete RV-8 Construction Log http://www.mattsrv8.com/Mishap - Landing Mishap Rebuild Log http://www.youtube.com/MattsRV8 - Matt's RV-8 HDTV YouTube Channel Status: 172+ Hours TTSN - Rebuilding Fuselage After Landing Mishap... RV-6 #20916 N360EM "The Flyer" http://www.mattsrv6.com - Matt's RV-6 Revitalization Log Status: 200+ Hours Since Purchase - Upgrades Complete; Now In Full Flyer Mode Matt's Livermore Airport Live ATC Stream! Check out the live ATC stream directly from my hangar at the Livermore Airport. Includes both Tower and Ground transmissions. Archives too! 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