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Thread: preventive maintenance

  1. #1

    preventive maintenance

    I ran across the following and thought it was good info. Can't remember
    where I saw it but will look again and let you know if I find it. Seem
    to recall it was Grumman centric, but good advice for all (like Mike and
    Bob have been telling us all along!).

    -Rick Koch
    N2010A

    ---------------------------

    The best safeguard against mechanical failure is knowledge, inspection
    and preventative maintenance. Many owners view maintenance as an annual
    ritual, assuming that nothing goes seriously wrong between annual
    inspections. Nothing could be further from the truth. Throughout the
    year, it is our job to ensure that the aircraft remains airworthy. This
    includes things such as routine inspection, lubrication, AD compliance,
    transponder and IFR certification and ELT battery expiration. But, it is
    also our job to proactively maintain the aircraft over the long haul.

    The majority of our aircraft are getting quite old, and while only the
    wings, spar and engine are 'life limited', there are many components
    that should be replaced or refurbished proactively, due to their age.
    When I review reports of mechanical failure, some common areas stand
    out:

    1. Hoses - If your hoses are more than 5 years old, replace them.
    Hoses are probably the most commonly neglected maintenance item.

    2. Oil Analysis/Filter Inspection - If you are not currently
    performing oil analysis at each oil change, I recommend that you start.
    It is an excellent way to learn more about the health of your engine.

    3. Valve Guides - Our engines are particularly susceptible to early
    exhaust valve failure due to problems with the Valve/Valve Guide
    clearance. You may have heard of the "wobble check" to inspect for this
    problem. All Lycoming 0-320 and 0-360 engines should be inspected every
    500hrs. More frequently doesn't hurt either! Talk to your mechanic to
    learn more.

    4. Brake Lines - There are many reports of brake failure due to
    corrosion wear and fatigue of the rigid brake lines on our aircraft.
    Inspect them carefully. If they are original, have them replaced.

    5. Alternator Belt - Most cars have specified intervals for belt
    replacement, regardless of condition. Taking the same approach with your
    plane will help reduce the risk of an electrical failure.

    6. Control Cables - At our most recent convention, we learned first
    hand that control cables can fail if not carefully maintained and
    inspected on a regular basis. I recently had a discussion with the
    president of a major aircraft cable manufacturer on the topic of
    corrosion and fatigue. He had serious concerns about aircraft flying
    around with 25 year old cables.

    7. Throttle/Mixture/Carb Heat Cables - These should all be
    carefully inspected. If any of your engine controls are stiff, they
    should be repaired or replaced.

    8. Vacuum Pump - If you fly IFR, I strongly recommend that you
    replace your vacuum pump well before it's scheduled overhaul time.
    Vacuum pumps are not the most reliable component in the aircraft, and
    often fail without prior symptoms. The best protection, of course, is a
    backup system.

    These are only a few of the many things that we can do to increase the
    safety of our aircraft. The key to excellent maintenance is education. I
    strongly recommend that all owners get their own copy of the parts and
    maintenance manual for their aircraft. Reviewing these publications can
    be an excellent starting point to learn how our planes are put together.
    I also recommend that anyone unfamiliar with the mechanical details of
    the aircraft schedule some time with their mechanic for a 'maintenance
    checkout'. A typical flying checkout teaches pilots about the proper
    operation of a new aircraft. A 'maintenance checkout' can teach you all
    about the systems, proper maintenance and routine inspection of the
    aircraft.

    The FARs provide us with a baseline for keeping our aircraft airworthy
    by inspecting them on an annual basis. It's our responsibility, as
    owners and pilots, to take our maintenance to the next level so that our
    flying experience as safe and enjoyable as possible!

  2. #2

    preventive maintenance

    Yes this was on a Grumman site after the 2001 annual convention of Grumman
    owners in Cincinnati OH where a plane had a control cable failure and
    narrowly averted damage to the plane on landing.

    The advice is valid all the way across our Musketeers, and I have added
    comments to point that out.

    >--------------------------
    >The best safeguard against mechanical failure is knowledge, inspection
    >and preventative maintenance. Many owners view maintenance as an annual
    >ritual, assuming that nothing goes seriously wrong between annual
    >inspections. Nothing could be further from the truth. Throughout the
    >year, it is our job to ensure that the aircraft remains airworthy. This
    >includes things such as routine inspection, lubrication, AD compliance,
    >transponder and IFR certification and ELT battery expiration. But, it is
    >also our job to proactively maintain the aircraft over the long haul.

    Yes, the owner/pilot is responsible for the airworthiness of the plane on
    each flight. Too much gets deferred until annual that ought to be taken
    care of all year long. Look at FAR 43 appendix A subparagraph (c) for a
    list of items that the FAA deems "preventive maintenance" that you can do
    to maintain your plane without taking it to a mechanic.

    >The majority of our aircraft are getting quite old, and while only the
    >wings, spar and engine are 'life limited', there are many components
    >that should be replaced or refurbished proactively, due to their age.
    >When I review reports of mechanical failure, some common areas stand
    >out:

    Yes, we have 40+ year old Musketeers, and even the youngest 80's model is
    getting a little long in the tooth. We need a "preservation and
    restoration" mentality, not the attitude of the 70's and 80's that little
    can be wrong with the plane since its so new. We are all flying "antiques"
    and need to preserve and inspect them much more diligently because they are
    far from new, and in most cases have had many owners and the maintenance
    history is unknown.

    >1. Hoses - If your hoses are more than 5 years old, replace them.
    >Hoses are probably the most commonly neglected maintenance item.

    I see more ancient hoses than I care to mention. I've rescued a plane out
    of a pasture with cows standing around it because the oil cooler hoses had
    failed. Those with forward mounted oil coolers need to be particularly
    diligent in this, as the hoses run near the exhaust and get cooked. I've
    grabbed many a hose during annual and heard it crackle because the rubber
    liner was shot.

    Use a reputable Aeroquip hose shop for your replacements. I use Sacramento
    Skyranch. A FSDO in the northeast recently ruled that they don't think
    mechanics can make the hoses in the field, or at least not without
    thousands of dollars worth of hose assembling and testing equipment, so
    don't try to save a buck and get an uncertified hose, when you can get the
    real TSO approved hose from a certified shop for less money if you are
    paying your hose assembler by the hour.

    >2. Oil Analysis/Filter Inspection - If you are not currently
    >performing oil analysis at each oil change, I recommend that you start.
    >It is an excellent way to learn more about the health of your engine.

    I accept this as a good trend monitoring tool. Not a good "spot check", as
    one set of data points are not very useful. Be aware that the calibration
    lab to lab is significantly different, so you need to use the same lab for
    several samples before you can start to spot trends that mean anything.

    >3. Valve Guides - Our engines are particularly susceptible to early
    >exhaust valve failure due to problems with the Valve/Valve Guide
    >clearance. You may have heard of the "wobble check" to inspect for this
    >problem. All Lycoming 0-320 and 0-360 engines should be inspected every
    >500hrs. More frequently doesn't hurt either! Talk to your mechanic to
    >learn more.

    Sadly many mechanics, OK, MOST mechanics, have never heard of Lycoming SB
    388C, the current revision of the "valve wobble" procedure, and most
    certainly don't have the TOOL to properly check it. Aircraft Spruce sells
    the tool and Lycoming will fax you a copy of the SB if you call them. So
    why not get the tool and check yours out? A Grumman owner in the Northeast
    US is renting the Aircraft Spruce tool <jeff.simon@salesapproach.com> if
    you'd rather rent than own. The key is that we KNOW what causes stuck
    valves and broken valves on Lycoming parallel valve engines, and Lycoming
    has given us the information to evaluate our engines, so we can prevent
    these failures. Why would everyone not want to KNOW that their engine is
    in the "safe zone" when flying family and friends?

    >4. Brake Lines - There are many reports of brake failure due to
    >corrosion wear and fatigue of the rigid brake lines on our aircraft.
    >Inspect them carefully. If they are original, have them replaced.

    Fair enough, the Musketeer series has flex lines at the main gear. But,
    most that I see are original and 30+ years old. See item #1, replacement
    of flex hoses above. I'd say that you ought to consider giving your plane
    a new set of brake hoses if you can't find in the logs or on the data tag
    on the hose that its ever been replaced. (Another reason to have a
    certified hose shop make them, they come with a data plate showing
    manufacture date, so you can PROVE that they are not "old".)

    >5. Alternator Belt - Most cars have specified intervals for belt
    >replacement, regardless of condition. Taking the same approach with your
    >plane will help reduce the risk of an electrical failure.

    DUH. Your car's manual says 60,000 mile belt replacement. That is 4-5
    years for most cars. Even those that are not used deteriorate from
    weathering, so when is the last time you changed the alternator belt?

    >6. Control Cables - At our most recent convention, we learned first
    >hand that control cables can fail if not carefully maintained and
    >inspected on a regular basis. I recently had a discussion with the
    >president of a major aircraft cable manufacturer on the topic of
    >corrosion and fatigue. He had serious concerns about aircraft flying
    >around with 25 year old cables.

    Some foreign countries (Australia) have life limits on cables and they MUST
    be replaced after certain date, and they must be removed and inspected in
    the intervening years. We in the US have very lax rules on control cables,
    and I'll bet that virtually every Musketeer in the fleet is still using the
    OEM cables, and that they have never been removed from the pulleys and
    flexed to look for broken strands. I am currently working on a plane in
    which we are replacing every single strand of control cable, and I sure see
    lots of Musketeers that could stand to have the same thing done. There
    have been issues with the corrosive fumes from the battery in the tail cone
    damaging the cables aft of the baggage compartment. Had a look at yours
    recently?

    >7. Throttle/Mixture/Carb Heat Cables - These should all be
    >carefully inspected. If any of your engine controls are stiff, they
    >should be repaired or replaced.

    Amen. A friend lost his plane when the throttle cable disconnected from the
    carburetor and he landed 300 yards short of the runway at the airport he
    was trying to reach. He also took about a $20K hit on the insurance pay
    out. He had never upped his coverage to account for the increase in value
    of his plane in the 10 years he'd owned it, and when he went to replace it,
    he found that his insurance check would NOT buy him another one as nice as
    his plane!

    >8. Vacuum Pump - If you fly IFR, I strongly recommend that you
    >replace your vacuum pump well before it's scheduled overhaul time.
    >Vacuum pumps are not the most reliable component in the aircraft, and
    >often fail without prior symptoms. The best protection, of course, is a
    >backup system.

    At the very least, if you are going to fly IFR, you need a vacuum failure
    warning light. From the time of vacuum pump failure to the point at which
    the gyros are unusable, you have 60-90 seconds to transition to partial
    panel, cover the gyros, etc. If you KNEW at the instant of failure that
    you can no longer trust them, you'd be a lot better off than if you have to
    RECOGNIZE that something isn't right from the bogus gyro indications, and
    then get the plane back to straight and level with your inner ear telling
    you things you don't want to pay attention to.

    Precise Flight sells just the switch and warning light from their standby
    vacuum system for about $65. This is one of the best "insurance policies"
    you can buy for IFR flight, and it makes a handy Master Warning, since its
    a red "idiot light" on the panel when the engine is not running and the
    Master is on.

    I think that an article from me for a future issue of the BAC newsletter is
    the next step in this discussion.

    Bob Steward, A&P IA
    Birmingham, AL

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