interesting point about sump drain from accident

[craigsteffen]

[i'm going to split my typing over a couple of posts; I typed this out this morning and then lost the post because I hadn't kept a copy.]

I just joined MAPA, and I got the November issue with me welcome packet a couple of days ago.

The accident report is interesting.  They ran out of fuel, apparently because the sump drain didn't close properly.  The NTSB analysis, and the following article both talk about following the correct procedure, which is to drain the sumps and then check it during the walk-around pre-flight to make sure it's stopped draining.

What I find interesting is that section of the pre-flight in the POHs that I have is that it changes depending on the year.  In the 1969 and later manuals, the pre-flight section says:

1. Ignition Switch--OFF.  Master Switch--ON to check outside lights, then OFF.  Fuel Selector Drain--Selector handle on R; pull ring and hold for five seconds.  Repeat procedure with selector handle on L.

Then there's the instructions for the walk-around check, which includes draining the tank sumps in steps 6 and 8.

...to be continued...

[craigsteffen]

In the pre-1968 manuals, it has a different order.  First it has the steps for the walk-around preflight, including checking the sumps in steps 9 and 15. 

THEN it has the "Entering the Airplane" section, which includes

Drain the fuel selector valve on the floorboard and turn the selector to the proper tank.  Be sure the draink returns to "OFF" position and that the pull ring is properly positioned in the cavity provided.

So this has you draining the sump AFTER you get in the airplane for the last time; so with no opportunity to check to make sure that the drain valve closed.

[craigsteffen]

Which brings up some interesting points.

If they guy in the accident have been flying an older airplane where checking the sump drain wasn't part of the checklist, would the pilot been less at fault.  (Not my real question, just an interesting regulational/legal/insurance question.)

Which makes the point that there should be certain absolutes about your checklists.  One is that when you drain a sump, you should check VISUALLY that the draink has stopped draining.  This is trivial in a Cessna or Piper, because you're next to each drain as you drain it.  In a Mooney it's a matter of draining it from inside and THEN checking that it stopped outside.  Another absolute might be that you drain the tank sumps first, and then the center/main one.  Neither one of these checklists fulfills both requirements.  An argument for always making your own I guess.

 

[Mac201]

In the 92 MSE POH, the sumps are drained after all exterior checks and then entering the cockpit.  I was concerned about this and started to reverse the procedure to before the exterior checks.  Then I remembered that if you drain the sump before sumping the tanks you could draw water into the fuel lines.  So, I have stayed with the POH procedure.

[craigsteffen]

Quote: Mac201

In the 92 MSE POH, the sumps are drained after all exterior checks and then entering the cockpit.  I was concerned about this and started to reverse the procedure to before the exterior checks.  Then I remembered that if you drain the sump before sumping the tanks you could draw water into the fuel lines.  So, I have stayed with the POH procedure.

[jax88]

Yep, great argument for making your own checklist.  As previously stated, get in, do the in-cabin pre-flight stuff, then do the outside stuff.  Need to check all three sump drains, as I discovered my right one dripping after sumping once.

[carusoam]

Always make sure they all stop dripping.  Small bits and pieces are always trying to hold the drains open.   It is probably a good idea to carry a spare.  It can really be annoying trying to flush out a wing sump that has a tiny spec stuck in it.

Never trust anything to stop dripping without seeing it yourself.  (where's crash n burn now???)

Best regards,

-a-

[craigsteffen]

Quote: carusoam

Always make sure they all stop dripping.  Small bits and pieces are always trying to hold the drains open.   It is probably a good idea to carry a spare.  It can really be annoying trying to flush out a wing sump that has a tiny spec stuck in it.

[carusoam]

Craig,

Spare quick drain for the tank sumps.  I am not sure if it is on the list for things you need your mechanic to sign off.  They are unique enough that not all mechanics have the right part in stock.  I became familiar with these parts during owner assisted annuals.

It is a simple cleanable drain with a "rubber" seal on it.  Hand torque is all that is required to properly return it in place.  If the tank is full it can be a challenge.  But nobody said it should be full when you change the part out.

From observation, I have seen a qualified mechanic remove a quick drain and replace it with a new one.  Some fuel does fall into the bucket below the wing.  I don't recommend working with fuel this way though....

The drain can easily be held open, or removed, to fill the catch bucket.   When the tank is empty, you can probably take all the time you need to clean out the same quick drain that you removed......

If you are skilled enough to operate a quick drain, than you are skilled enough to remove and replace one.  Check with your mechanic for technical details and legal requirements.

How many sump drains and belly drains are on the C172 you are flying?

Best regards,

-a-

[MooneyMitch]

Hi -a-.

In my experience with the F391 flush drain valves, I do believe the package does state not to attempt to clean, but simply replace.  That could be the legal system speaking, or the manuf. for that matter.  But, given how infrequent these little devils do acutally begin to leak, and their relatively low price of approx. $20, it might be good just to go ahead and replace.   Also, as someone else stated, just have one or two in your little travel tool kit just in case your away.

Also, remember the gorgeous F model that was burned up [earlier this year I believe] that was in the shop during fuel tank draining?  I agree with you about not handling fuel without the proper methods.  It just takes one spark and oh my! 

Happy Mooney loving and flying to you.