Oil Pressure after Start Up 30 secs ?????

[Guest Ginger]

The ATC Flying Traing Manual says

 

“After engine start , it is most important to check that the oil pressure rises within thirty seconds. Then the procedure ….. “

 

 

My question is, why thirty seconds ??

 

 

I have also seen it in the check list provided by the flying school.

 

 

In my experience even 10 seconds to gain full oil pressure is a very long time for a modern motor

 

If it was anywhere as long as 30 seconds (even if it evetually did gain pressure), I would consider the bearings completely shot or there are other very serious problems.

 

I definitely would not fly with such a motor.

 

I note that the 912-S Rotax motor, specifies 10 seconds and the Operations manual for the Evector Sportstar also specifies 10 seconds.

 

 

So where does the 30 seconds come from?

 

 

Is tradition or does it apply to other other motors ?

 

 

If it is from other motors why doesn’t it cause excessive wear? After all susburban myth is that that most of the wear in motors comes from the first few second after start when everything is cold and nothing is being properly lubricated.

 

Ginger

 

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[facthunter]

Time for oil pressure rise.

 

This is a serviceability thing where you give the engine enough time to prove/disprove the oil system as operational. It does not imply that this is normal. You always abide (operate ) within the parameters laid down in the POH for aircraft type, or engine manufacturer.

 

Some of the older motors, ie Gipsy major, if they had been sitting unused for a while would drain most of the oil from the oil system. Because the engines ran close fitting white-metal bearings they had relatively small oil flow rate oil systems, (smaller oil pumps) it took a lot longer to expell the air from the oilways and get full oil pressure up, so 30 seconds was a realistic "limit", before you start to react and shut the engine down. This would be an excessive time for a modern engine with bigger bearing clearances, more critical bearing alloys being used and higher volume oil pumps. The hydraulic lifters do not like being operated without oil supply to help them "pump-up", so the engine should not be started up with higher than recommended engine RPM's initially. Nev.

 

 

[Yenn]

30 seconds is a very long time and I certainly would have shut down before then with my Jab motor or a Rotax. If I don't see movement as my eyes scan from outside to the gauges I would be starting to worry immediately. I have lost oil pressure in flight, due to a wire coming adrift, so now I always look for the gauges to just flick as I turn the master switch on, that at least confirms that the gauge will work so no pressure indicated is really NO pressure.

 

 

[geoffreywh]

Some of us have older engines (Continental 0-200)....When I first got my aeroplane It would take a minute to see oil pressure on the mechanical oil pressure gauge. As the engine had (only) 1200 hours on it you would have to assume that the engine was fine..I was not happy with that and changed the oil to a multigrade type (aviation) instead of 50w (with manufacturers approval) Now it take just 30 odd seconds to see the correct pressure on the gauge. The result you get will depend on where the sender is located and if it is an electrical sender or the old capillary tube type... For modern engines 30 sec. is TOO long....for 1950's designs 30 secs is fine...

 

 

[Guest Ginger]

Oil pressure delay on engine start up

 

Thanks Geoff,

 

As you confirm the 30secs is probably tradition starting from the older engines.

 

In the case checklists provived by instructors, they really should be made specific to the particualar training aircraft/motor. For a Sporstar/Rotax combination the flying school should provide appropriate specific post start checklist which qotes the (10secs) from those manuals together with a note to check the figures for other aircraft.

 

A trivial edit is required to page 39 of the Aviation Theory Centre The Flying Training Manual but I have already raised the matter with the authors. In the case the Jim Davis PPL book page 177, 30 seconds has been quoted but related to Lycoming and Continental.

 

I have not checked the Jabiru manual but being a modern motor but expect it to be in the region of 10 secs as well.

 

Ginger

 

 

[facthunter]

Oil Indications.

 

The oil pressure transmitter is a notoriously unreliable instrument, and would fail more times than the system it is monitoring, IF your LIFE was dependent on the engine keeping going, then you MAY have to ignore the indication. A FAILED sender, usually reads nothing, as distinct from a situation where the oil pressure may still be there but fluctuating or reading LOW (related to a high temp. often).

 

The more reliable (and older system) is a capillary tube, with a small internal bore. This leads to a sluggish reaction to giving an indication on COLD start-up. The reason the bore is so small is to cope with the situation when the pipe breaks and would empty a lot of oil quite quickly out of the engine,and into the cockpit or engine compartment. It does have the advantage of working without relying on electrical power. The indication of SOME oil pressure at start-up is confirmation of functionality, and after a while it will register the correct figure.

 

It should be remembered that the main cause of no oil pressure would have to be ,not putting oil in the engine, and this should be a seperate check pre-flight.. Nev

 

 

[old man emu]

After all susburban myth is that that most of the wear in motors comes from the first few second after start when everything is cold and nothing is being properly lubricated. Ginger

 

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If you are very concerned that you engine oil has drained to the sump while the aircraft has been sitting unused from week to week, why not grab hold of the lump of wood or metal that spins around at one end of the engine, and pull it through a dozen or so times, or maybe more. It's not hard work, and it might not get the oil pressure up to operating level, but at least it will get the oil moving on its journey through the engine.

 

Old Man Emu

 

 

[Guest Nelson Smith]

Hi all,

 

Jab engine was taking around 30 secs to raise oil press. Traced to faulty non return valve in oil filter (solid lifter engine)

 

Nelson

 

 

[Guest check-in]

I am running an older Jabiru solid lifter engine and have stayed with Aeroshell 15W-50 even in the summer, as I firmly believe most damage occurs at start up if there is no oil pressure, so the lower viscosity must be a good thing.

 

When starting from cold I do these steps: 1. With ignition OFF and throttle fully closed, pull the prop through 8 compressions (to check that there IS compression!). 2. Run the electric fuel pump for about 3 seconds, then pump OFF. 3. With ignition still OFF, crank engine on starter for about 2 seconds (this gets the oil pumping). 4 Ignition on and start - idle at 1000 to 1100 rpm for the first minute or so before idling at 1200. The oil temp takes forever to rise above 50 C so once the cylinder temps are about mid-range (about 250F) I run it to 2000 RPM, check the ignition and continue to takeoff asap, preferably increasing to full power straight from the 2000 rpm ignition check. I am usually airborne within 5 to 6 minutes of start-up in the hot weather, 10 minutes in cold weather.

 

I have never had to use choke and the oil pressure indicates instantly the engine fires. Compressions all feel good. Plugs indicate it runs a bit rich, but I don't mind that either. So far so good with this elderly Jabiru engine.

 

 

[Yenn]

I lost oil pressure once while airborne. As luck would have it I lost oil temp at the same time, so I concluded that there was an electrical problem, no need to panic and made a quick return to the airstrip. I know it is not connected to start up but is a similar problem. having engine instruments all on the same circuit works.

 

 

[Guest check-in]

Yenn

 

Good analysis on your part - the likelihood of losing pressure AND temp simultaneously is so remote as to be virtually impossible (unless all the oil went instantly overboard!). But loss of electrical power to the instruments is a good enough reason to land at the nearest suitable airfield anyway. However I would not see that situation as justification for a landing anywhere other than on a good airfield for as long as the engine was still running OK.

 

Off thread, I know, but does the new human factors training teach this type of risk management? Also to recognize gauge zero versus electrical zero? It's so long since I did any basic theory I have lost touch with what is being taught these days.