ever lose a fuel cap in flight?

Well, Yesterday was a bummer. I had planned an overnight trip to Waterloo from Ottawa (about a 1.5 hour trip) to have dinner with some friends. The weather was looking good, high ceilings and good forecast for the return trip. Long story short, I had a tonne of things to do to get ready, and it took me most of the day. Plus I had to wait for enough of the runway to be plowed so I could get out (we'd gotten hit with a dumping of snow the night before). Finally, at 2:30pm, I was ready for takeoff (which would have me in Waterloo well in time for dinner). Smiling, I throttled up and took off. Within seconds I felt a bit of something like the left wing dipping a touch, which I thought was just a bump of turbulence. I looked to my left and saw a missing fuel cap and fuel spraying out. ****. I checked that I was on the other tank (I was), and proceeded to climb into a circuit for an immediate return. I speculate that the slight wing dip I felt was as the fuel cap blew off the drag profile in the area around the missing fuel cap was suddenly different.
I have no idea what happened to the cap. I remember checking them both before takeoff. I'm guessing that maybe with the cold weather the seals had dried out or contracted? Weird thing is, i've been flying in colder weather than that several times over the last month.
My lesson-learned, I ordered a replacement cap plus a spare, which I will keep in my emergency tool kit in the back of the plane, so I have a spare one when I'm away from base.
I was really bummed out not to make it to Waterloo, but perhaps this was fate keeping me from making that flight for some other reason unbeknownst to me.

I know a guy in a 6A who lost one. I do not recall the specifics.

As for your case, if there is a failure mode that I am not familiar with this could assist me in my never ending education process.

However, I have for years kept a spare fuel cap and assorted parts in the plane.

On a related note, what is the exact size of the fuel drains? Is it a 1/8 inch NPT? The reason is I want a spare in case I have a failure of one of those.

I lost a cap on my Cherokee 180 when my daughter forgot to put the cap back on after refueling and I didn't double check her either.

Fortunately, I noticed it on take off, flew a tight pattern, and landed. The fun was looking for it on the runway. It took awhile, but we found it. Fuel loss wasn't too bad.

Lost a fuel cap in a Long EZ

Fortunately the openings were expertly located by Rutan to miss the prop if that ever happened. I had just before lubricated the seal to help keep it from drying out with a small shot of silicone spray. That was enough to lose the friction on the rubber seal . Have a similar cap on my RV9 that is maintained quite tight with no lubricants. !

I tossed a "spare" cap on one day to go fly formation. About 5 minutes in to the flight I look over and the cap is sitting about a half inch high and fuel is pouring out. I broke off the flight and headed back. The cap turned around a few times but never left the airplane. It was latched but maybe was adjusted for a different flange. It was interesting to say the least.

I lost one immediately after take off one day after I forgot to flip the lock down. I saw it fly off out of the corner of my eye and realized immediately my error (after just refueling). Landed, found some aluminum speed tape, put a couple of layers over the hole and I was on my way.

I did not put the lever down on one cap during my preflight when someone came along and started talking to me. I was in my hangar on my home field. I took off from my home field for one circuit. When I landed and shut down, I saw that the cap was missing. Looking on the runway, it was about 75 feet down the runway from where I started my takeoff roll. I had already installed my spare cap from my tool kit when I retrieved the old one. Since the old one was polished and engraved, I put it back on the airplane.

This happened on the 2nd weekend of this year after I have flown the airplane more than 13 years and 2,400 hours. Yes it can happen to me. Like an old FAA inspector once told me. "In God we trust. Everything else we check."

Ron Lee said:

On a related note, what is the exact size of the fuel drains? Is it a 1/8 inch NPT? The reason is I want a spare in case I have a failure of one of those.

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Not sure about the size, but the common failure mode on these is a damaged o-ring. I ordered a couple extra ones and carry those with me on x-country flights.

WRT losing fuel caps, add "check fuel caps" to your engine-run up check list and USE THE CHECK LIST and you should avoid this problem.

erich

I have never lost one in fight but always take a look at the caps when doing a control check.

Also, I carry an extra cap (and quick drain) in my tool bag.

The thought of losing a cap is exactly why I did NOT have my N-number engraved on them, only the fuel requirements.

PS. Fuel lube on the O-ring will help increase the life of the rubber part and aid in securing the cap.

Ron Lee said:

I know a guy in a 6A who lost one. I do not recall the specifics.

As for your case, if there is a failure mode that I am not familiar with this could assist me in my never ending education process.

However, I have for years kept a spare fuel cap and assorted parts in the plane.

On a related note, what is the exact size of the fuel drains? Is it a 1/8 inch NPT? The reason is I want a spare in case I have a failure of one of those.

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Yes, 1/8" NPT. A plug will work just fine to get you home if you want to pick up something at the nearest home improvement store.

I lost a cap on a Comanche once...lost 14 GALLONS in one trip around the pattern!!

I'm willing to bet the cap is near where you rotated. Once the wing generates lift, the pressure on top of the wing would suck the cap right out if not locked down. Check that area, and I bet you'll find it...

Maintenance item

Operational checks and maintenance of fuel caps is on my Condition Inspection checklist so they get looked at every year. Proper tab tension, wear plate condition, tab shoulder wear condition, O-ring condition, and overall cap fit tension are critical. Both the stem seal and the large Viton O-ring should be lubricated with a film of Fuel Lube or EZ-Turn Lubricant.

A visual check of the caps is part of my pre-launch checklist. (CIGAR- "C" is for Controls & Caps). I can easily see them from the seat of any of the RV models (except -12).

Don't leave home without 'em...

As mentioned, check the snugness of the cap on pre-flight. When fueling, put the cap in your pocket, so there's no chance of putting it down and forgetting to put it back...you'll notice it in your pocket when you attempt to strap in. Have a spare on hand. I never lost one in the RV, but did in the Pitts once (negative G) due to degrading rubber and lack of pre-flight check. The cloud of fuel spray over the canopy got my attention.

Last year shortly after takeoff some motion caught my attention out at he left wing; sure enough, the cap had come off. The hole in the wing is behind the maximum thickness and the fuel level was only half-way so there was no fuel emerging.

The cap had been showing signs of coming loose previously and I thought I had fixed it with silicon grease to allow the plunger to pull up on the rubber donut without friction. My friend had had a similar loss of one cap on his plane. So I made two fiberglass-foam caps that fit the wing curvature with minimal gaps. They are fitted with screws that go through the center and farther along through a bar with a threaded hole in its center. This bar is wider than the opening so it has to be slipped through at an angle. The end of the screw below the bar is fitted with a metal lock-nut so that the travel through the bar is limited; it can't be unscrewed! I just loosen the screw and jiggle the cap around until it comes out of the hole. To close I angle the bar until it goes below the opening, and then tighten the screw to pull the cap securely into place. No more lost caps!

Many certificated airplanes use a cable or bead chain to contain the fuel caps, the disadvantage on the RV would be the retained caps may damage the visible wing surface when blown around.
Any thoughts?

some aircraft have their fuel caps attached to the tank via a small chain or similar.
my understanding however is that this is not to keep the cap from getting lost but rather for static grounding. in theory, a fuel cap in your hands that isn't grounded to the aircraft could cause a spark. however, with all the standard rv fuel caps (ungrounded) and the assumingly many refueling cycles, i think it's safe to say that this theory has very little merit. at least haven't heard about a flock of refueling accidents involving rv's...

that aside, losing a cap is probably one of the "classics", along with an unlocked canopy etc...
hasn't happened to me yet but may someday. just fly the airplane first.

we have the retrofit key-lock insert caps from the van's catalog installed and like them. first of all, they look nicer and secondly, chances are that you are holding the cap by holding the key and are more likely to reinstall them right after removing the fuel nozzle.

regards,
bernie

I lost a cap years ago on my RV4. The tanks were filled by the airport and I did not check to make sure that they were secure. I was twenty five miles away when I noticed it. This was about half way through my first 25 hours, on my first project! Fuel was streaming out of that tank but the other one was full so I was not worried about the amount of fuel that I had, but I did have 10 or 15 minutes to worry about sparks etc on the way back to the airport. When I went to land the runway was covered in seagulls and I admit that I was so distracted by the loss of the fuel cap and the consequences of having to go around that I let my speed get too slow. I caught it in time but it sure brought home what can happen when you focus on just one aspect of flight.
The birds walked off the runway as I was getting ready to go around and later we found the cap half way down the runway, on the centre line, undamaged.
There have been no lost caps in the last 16 years!

EZ Turn

If you use Fuel Lube in the northern climates, the caps will never come off in the winter! I think Mel suggested Lubriplate, and I have found that to be ideal here in Wintersota.......

I lost one at about 100' and 100 knots on departure from a fuel stop. In my peripheral vision, I noticed a dark object (I assumed a bird) zip by my left wing. When I looked, no bird, but no fuel cap either. I made a mental note of my position over the field immediately after realizing what happened.

I flew an abbreviated pattern, noticing that the tank spewed fuel at high angles of attack and didn't at lower angles of attack.

Then I landed, parked, and walked the runway starting at the point where I saw the cap depart. I found it off in the weeds beside the runway, slightly dinged, but useable. I continue to use that cap as a reminder.

BTW, I had assumed the fuel guy had replaced the cap and he assumed the opposite. My fault entirely.

23 years in Marine aviation - saw a number of gas caps come off. The worst I ever saw was an F/A-18 Hornet loose a cap off a center line drop tank on take off in the late 80's. Big fire ball when the fuel mist hit the afterburner. The pilot ejected safely.

I'm not suggesting this can or will happen to an RV. Easy to put it on your check list to check caps after run up.

Just a thought

Why dont aircraft use the same fuel tank caps as motercycles? They are made by the same company and I think have the same size opening.
You cant lose it. It will blow shut (almost) if left open. And it wont bounce around like a cap on a chain would.

Just a question.

Hey Phil

Yep, lost one about 15 hours into my test program. It was getting hard to open and close so I loosened the nut a little (too much, as it turns out). I did this on a warm (for January in Ottawa) day, probably around freezing. I went flying again the next week when it was -20. I got to 1000 AGL and just happened to be looking at the right tank when FLICK, off went the cap.

Sigh...

I bought two new caps from Vans (one replacement, one spare), and good thing too. The following fall I had flown down to Lindsay for breakfast and when replacing the left cap during my walkaround the pin in the cap sheared off. Thankfully the nut and shaft didn't fall into the tank and I managed to get it all out. I plunked in the spare and off I went.

Cheers

Thread Revival:

I have locking gas caps and leave the airplane keys in the cap while refueling. Dumb luck, but it's impossible to takeoff without the fuel caps on because my fuel cap key is on the same ring as the ignition. Do these caps routinely come off? Trying to determine if it's worth bringing a spare along.

Over 50 years ago I lost a tip tank cap on the first solo flight in a T-33, never will forget it. It cost me enough gig points to buy a case of beer when we graduated.

Everyone on the ground knew what was going on as I circled the field with fuel streaming out of that tank while burning the other side dry. Both had to be empty for landing. If not the procedure was to bail out, you did not land the T-bird with unbalanced tip tank fuel, the ailerons would not keep it level at low speed.

The cap came off because I did not secure it during the preflight. Just at the point my IP called me to the other side of the airplane to show me something and I skipped it. I wisely did not mention that to him when he met the flight. He was a good instructor and we got along fine, I should have caught it no matter the interruption.

Funny how you never forget somethings in life.

In my opinion, yes, you should carry one spare. Losing a cap is a really rare occurrence, but as I said my earlier post (3 years ago) I have had the latch pin shear off in a cap. Now, I don't know how the locking mechanism works on your cap, but if the pin through the latch shears off, can the cap still be secured to the tank?

I've replaced two sheared latch pins in ten years now. The second one happened in the hanger during a walkaround, so it wasn't a big deal. However, I did get to go flying anyway because I had a spare cap.

Cheers

David-aviator said:

Everyone on the ground knew what was going on as I circled the field with fuel streaming out of that tank while burning the other side dry. Both had to be empty for landing.

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Talk about penalty vectors. Great story!!

Spare Cap

I always carry a spare cap. They are cheap. Even if I don't need it, maybe another RV driver will!