Oil cap left off in flight -whoops

[jrwilson]

Forgot the oil cap on my 231 on an hour flight. New plane with different cap/dipstick combo.

when I landed I noticed oil dripping off the tail and realized cap was off.  Looks like I dumped about 1 qt.  temps were fine (<180) and pressure was good (45 -47).  I didn't see any oil in the cowling, virtually none.  No oil at all around the filler tube.

where did the oil come from?  Did the pressure difference with the cap off suck it out the breather?  I cleaned up the mess and flew back.  Got back and oil was still dripping off the tail, though I admittedly wasn't able to clean the belly well at first.

this jusnt an unrelated coincidence is it?  Since there was no oil in the cowling and none around the cap area?  Was something else possibly going wrong?

temps and pressures were all good and no overboost on takeoff, never went above 36" mp (intercooled).

any ideas?

[Guest]

Higher pressure above the cylinders, where the oil filler is in your 231 could certainly pressurize the crankcase enough to vent oil out the breather.

Clarence

[cliffy]

Yup it makes a mess.  Saw it happen on a Navajo once. Messy to say the least. 

Had it happen in a 727 once also. Maint. added oil to #2  Dumped it all but 3/4 of a gallon in 10 mins. 

Returned and they found the cap in the bottom of the cowl. 

[jrwilson]

Higher pressure above the cylinders, where the oil filler is in your 231 could certainly pressurize the crankcase enough to vent oil out the breather.

Clarence

Would the pressurized crankcase cause any damage anywhere?

[Guest]

No, it won't have caused any harm to your engine, unless it ran very low on oil.

Clarence

[PTK]

You know your crancase pressurizes just fine and bresther works!

Edited September 7, 2015 by PTK

[Shadrach]

Higher pressure above the cylinders, where the oil filler is in your 231 could certainly pressurize the crankcase enough to vent oil out the breather.

Clarence

One of my partners did a 2.5 hr XC with the dipstick lying across the accessory case. No visable loss of oil on the plane or on the dipstick (when he put it back in).

[N33GG]

Years ago, I came in late night from a long flight in a Piper Saratoga and taxied up to the FBO to get fuel and some oil added.  Line man that serviced plane had been there and never made a mistake in decades.  When he finished, I got in and taxied to my hangar... just a couple minutes max.  He had left the dipstick in but not screwed in.  In that short time, I had oil all over the plane. What a mess.

[Guest]

One of my partners did a 2.5 hr XC with the dipstick lying across the accessory case. No visable loss of oil on the plane or on the dipstick (when he put it back in).

Different in a K model versus your F model.  On the K the oil filler spout is ahead of the rear baffle in the high pressure area, where on most four cylinder Lycomings it's behind the rear baffle in a low pressure area.

Clarence

[jrwilson]

Different in a K model versus your F model.  On the K the oil filler spout is ahead of the rear baffle in the high pressure area, where on most four cylinder Lycomings it's behind the rear baffle in a low pressure area.

Clarence

your responses on this topic have been very helpful and appreciated

[Guest]

Glad I can help.

Clarence

[chrisk]

Many years ago I forgot to put the oil cap on in a rental 172.  In a half hour flight, it dumped 2 quarts of oil onto the side of the plane.   Nothing says student pilot like landing with a huge oil streak down the side of the plane.  Once was enough.  I always check the oil cap before every flight. I don't care if I get a little dirt on my hands.  Anyway, your not the first, and will not be the last.

That said, other have forgotten the fuel cap and lost several gallons of fuel. --So I for one really like those anti siphon  flaps in my 231, even if it some times makes the fuel caps stick.  And I really enjoy it when the line guy opens the cap and declares the tank is full.  I've gotten really funny looks when I tell them to top it off anyway.  As soon as they put the fueling nozzle on anti siphon flap, all the fuel drops.

[RobertGary1]

Where are you leaving the dip stick and you forget it? I place it on the open oil door, it helps to keep it from rolling off but also the open door should get attention. After a detailed preflight I will stand back and do a quick "sanity" look at the plane. Kinds of a "forest through the trees" review.

 

-Robert