Dangers of unscrewed oil cap?

[CaptCrispy]

I nearly made an enormous mistake a couple of days ago. Can anyone explain the probable outcome of taking off and flying with an unscrewed oil cap?

[stevelup]

Losing all your oil isn't ever going to have a great outcome...

[Dave Phillips]

At very best, a pi$$ed-off engineer who will need to spend a couple of hours cleaning everything firewall-forward.

[johnm]

Given that aeroengines mostly have an open crankcase breather is it really going to pump all its oil out of the filler tube? I'll go and ask an engineer I think.....

[Bill McCarthy]

Capt - can you give us a brief description of what led to you leave the cap loose - distracted or what ?

PS - you dipstick !!

[ffg]

Fess up time.

I once failed to check the oil before takeoff.

At the top of the climb I remember thinking, the viz is a bit hazy. Shortly after that I thought, some of the haze seems to be in the cockpit....

We got into a quick circuit and landed within 3-4 mins of takeoff.

No harm done, other than to my pride, which is no bad thing. The oil cap had been left in situ but not secured. It stayed there. I don't know how long it would have taken to empty the oil reservoir, but it was very obvious something was wrong, so unlikely I would have continued the flight. I seem to remember I put about 1.5 litres in to replenish.

It made a horrible mess which took about 1/2 hour to clean up, but we still went flying afterwards.

0-200, Jodel 1050.

[CaptCrispy]

It was during a few days in the UK with lots of cancelled slots due to weather. I did get a few flights done but the frustration was building.

The aircraft were coming back late from their student slots because everthing shifted due to bad weather and the three previous aircraft I flew (over 4 days I think) had to be refulled, two of them needed oil topping up as well. Nothing bad but quite unusual for three needing fuel and two needing oil all in a row for me.

On this particular day the (fourth) aircraft that I got also needed fuel and oil, it was late back, the weather was sure to get worse and I had to waste another 30 minutes doing fuel and oil. After refuelling and adding oil I did a last minute weather check and noted that if it begins to worsen I will fly a shorter safer route and/or return to the airfield; I then got myself seated. As I was doing the before engine start checks, I remembered I had topped up the oil; I knew I wanted to double check the oil level after topping it up, but could not actually remember securing the oil cap.

Luckily I remembered before doing anything important, but I don't like 'what if' questions without answers, which is why I posted.

As to why it happended, perhaps a combination of new pilot nerves (mainly weather related and the go/no go situation), a little rushing (keen to airborne while the weather allows) and distraction due to the nerves and rushing?

Yep - definately a dipstick!

[Bill McCarthy]

Thankyou.

[Mikey]

Used to fly a C152 with an oil cap that developed a tendency to unscrew during flight. We quickly had it fixed, but the one time I found it loose after landing all that was observed was a good sprinkling of oil under the cowling and a minor loss of oil. Not sure how long it was undone for, but I'm sure it could have been worse!

[Vince C]

The Gipsy Major in the Chippy has a seperate oil tank. I never managed to leave the oil filler undone, but I suspect with all the oil a Gipsy usually spews out in flight (especially if you aerobat it - when it actually reaches the tailcone sometimes) it wouldn't make a lot of difference if you did leave it loose. Except you might lose the cap/dipstick which is a lovely brass thing and probably difficult to replace.

[Jenny]

I managed to leave the oil cap off the Jungmann which has a separate oil tank... went for a half hour flight doing formation practice so very straight and level. Had intended to go and do some aeros after that but (luckily) my headset started to play up and make such an irritating noise that I landed.
Rather a mess over the back of the engine compartment and down the side and bottom of the aeroplane... probably lost less than half a litre but it looked much worse.
Spent ages (with about 20 people) searching the runway for the oil cap, but never found it

[Timothy]

An engineer left a filler cap off a C404 for me on a quick turnround once.

I was flying from Gatwick to Plymouth, and there was no obvious problem until about 20 miles to run to Plymouth, when a pax pointed out that the whole cowling and most of the centre section of the wing was covered in oil.

I shut down the engine and landed without incident at Plymouth, where I discovered the problem, cleaned up the mess and filled the oil.

Despite there being oil absolutely everywhere within a metre laterally, and 6 metres longitudinally from the engine, it took one litre to fill!

It would seem that oil is like blood. Very little of it goes a long way.

[Leighton CZ]

If you want to see what happens -- Open the filler oil cap on your car with the engine running -- but wear old clothes when you do !!
Timothy you were lucky, a freind of mine recently had a wrecked engine on one of his trucks, for this very reason, apart from the mess. It cost few thousand to replace the engine plus best part of another thousand to get the busted truck back to base.

[Peter Pan]

Fess up for me too. I took a flight from Barton to White Waltham in my 150 and left the oil filler / dipstick at Barton.....

Side of the a/c was covered in oil but again only took a litre to top the tank back up!

[CaptCrispy]

Thanks for all the feedback.

My initial thought was that I would see low oil pressure, then depending on how much is lost I would see increasing temperature. This combination (from the POH from memory) of low pressure and high temperature is a warning sign that an engine failure could be soon.

I really need (or want) to relearn the aeroplane technical subject.