Totally agree with you ericferret, the Piper PA28 service Manual states the vac pump should be changed at 1000 hrs OR at engine overhaul - it doesn't say whatever occurs first. I've known vac pumps fail within 50hrs from fitment.
If you maintain your aircraft to LAMS or LAMP then you have to abide by this, the airframe manufacturers servicing procedures and ADs, nothing else is mandatory.
I know companies that change privately owned aircraft vac pumps, overhaul FP props and carry out 500hr magneto inspections but not on their own fleet of training aircraft.
500hr magneto inspections are another good one. My CAA surveyor gave me a hard time for not doing them and implied that they were mandatory - till I pointed out they were not. Again the Piper SM, for instance is 'or change at engine overhaul'. I asked them for statistical evidence to prove that 500hr mag inspections made them last longer which he must have to insist that I do it - I'm still waiting 4 months on. He cited a case of a Mooney accident which suffered (single drive, dual mag) mag failure - I politely pointed out that the tragic, fatal accident occurred during the second take-off after the mag had been off for a 500hr inspection....
Minor point, in Lycoming Service Intruction 1009AS that engines should be overhauled in their twelfth year, not tenth if they haven't reached TBO first.
Another interesting bit in the latest GASIL highlights a statement in LAMS and LAMP in the 'how to do a Check A' section about turning engines over or running them during periods of inactivity due to say cruddy weather. LAMS says:
"If the aeroplane has not been regularly used, ensure before resumption of flying that:
a) either (i) the engine has been turned weekly or run fortnightly; or
(ii) the manufacturer’s recommendations have been complied with;"
Many will read the GASIL and and think that (i) might be good advice but goes against what Lycoming specifically say in their Service Letter L180B concerning periods of inactivity (and Ltycoming are the most common light aircraft engine in use):
"Pulling engines through by hand when the aircraft is not run or flown for a week or so is not recommended. Pulling the engine through by hand prior to start or to minimize rust and corrosion does more harm than good. The cylinder walls, piston, rings, cam and cam follower only receive splash and vapor lubrication. When the prop is pulled through by hand, the rings wipe oil from cylinder walls. The cam load created by the valve train wipes oil off the cam and followers. After two or three times of pulling the engine through by hand without engine starts, the cylinders, cam and followers are left without a proper oil film. Starting engines without proper lubrication can cause scuffing and scoring of parts resulting in excessive wear."
As for running, you need to fly the machine to get the engine hot enough to boil off any water/moisture, ground running isn't sufficiaent. SL180B again:
"Engine temperature and length of operating time are very important in controlling rust and corrosion. The desired flight time for air cooled engines is at least one continuous hour at oil temperatures of 165°F to 200°F at intervals not to exceed 30 days, depending on location and storage conditions. This one hour does not include taxi, take-off and landing time. If recommended oil temperatures are not obtainable, contact aircraft manufacturer for availability of oil cooler winterization plates."
Hopefully it might not snow tomorrow and I can go fly my machine and burn the water off!
PS I don't think the AAIB bulletin concerning the fatal Arrow accident which started off the vac pump comments has actually been releared into the public domain, contrary to what is said in the GASIL.
Last edited by smarthawke; 23rd March 2008 at 20:51.