How Long Will the Engine Run with Fuel Selector OFF

[22 others]

Some time ago, "a friend" managed to start-up and taxi with the fuel selector in the OFF position.  For whatever reason, he didn't notice until run-up. So he switched to a tank, waited a few minutes for that "Never Again..." feeling to go away, and then rechecked everything.

So how long does it take to starve the engine of fuel with the selector in the OFF position?  I know it'll run at least long enough to reach the runway. Anybody tested this before?

[CJpilot316]

In a 172, within a minute or two of startup.

[carusoam]

Long enough you won't immediately associate the action with the result...

This primarily happens to people transitioning from a Cessna, using old check lists, and the Mooney has worn out detents in the fuel selector...

1) there is no both position.

2) the pilot doesn't feel any detents.  Assumed there is one in the middle.

3) the old check list doesn't mention putting the fuel selector in place until doing the run-up.

 

This comes from my first lesson learned flying my old M20C. I went for a test ride and quickly learned the value of transition training from a qualified CFI.

Solutions

1) Get some transition training.  This was just the first thing that got missed.  There are others...

2) get the fuel selector overhauled.  LASAR rebuilds these and puts the detents back.

3) Update and follow the checklist.  He found it once, don't let it happen to your friend again.

 

The real important question isn't how long it takes for the fuel to run out, but how long it takes for the flow to return....

Sound familiar?

I am only a PP, not a CFI.

Best regards,

-a-

[Marauder]

Some time ago, "a friend" managed to start-up and taxi with the fuel selector in the OFF position.  For whatever reason, he didn't notice until run-up. So he switched to a tank, waited a few minutes for that "Never Again..." feeling to go away, and then rechecked everything.

So how long does it take to starve the engine of fuel with the selector in the OFF position?  I know it'll run at least long enough to reach the runway. Anybody tested this before?

I can tell you what I experienced. It was the reason I changed my checklist to include the "fullest" tank a couple of times.

I got distracted as I was doing the pre-start checklist. I had started moving the handle and let go of it to help a passenger with their seat belt. It ended up in the "off" position.

It was after a warm start. It started, I did a systems check including a quick mag check. I entered the runway and got to around 50 KIAS when it quit. So, my guess, 2 maybe 3 minutes.

Sent from my iPad using Tapatalk

[carusoam]

Marauder has given an excellent example of a 'distraction' how it happens to all pilots and what the possible results can be.

22O, see if your friend can recount what the details are of what happened.  It will help somebody around here, I'm sure...

Best regards,

-a-

[aviatoreb]

I have fuel to fullest tank on both the before taxi part of the check list and the check list for the hold short at runway part of the check list.

I use the first appearance of the fuel to fullest where I interpret it as to move the fuel selector to the fullest tank (or the one I want the engine to draw from on take off) and generally to check it is right.  Then I start taxi to hold short.  

At the hold short, I am taught to never touch the fuel since a problem it might induce might only appear shortly after take-off - the absolute worst time.  So I take that "fuel to fullest tank" at the hold short to mean simply to look down at it and to check all is right.

I like Josh how you said, "waited a few minutes for that "Never Again..." feeling to go away"  .... cute the way you worded it.  But right on.  That is the thing to do if you find the fuel is not drawing from the right place at the hold short.  Not to switch it then immediately launch.

[neilpilot]

Back in 2011 a local attorney picked up his C182 after having a BRS installed.  He took off with his fuel selector OFF and reportedly got to 300-400 AGL before the engine quit. He had critical injuries but survived.  C182 was totaled.  He used the BRS before the check cleared on his purchase.

http://www.thekathrynreport.com/2011/06/developing-plane-down-in-holly-springs.html

[Hank]

I read an Accident Report about the time I bought my plane, from a field I visit most years. Henderson Field, Wallace SC. Some poor soul had the selector Off, taxied out and too off. The field is generous length (3500'? 4000? I forget), and he went down in the trees of the end.

As a new pilot and a new Mooney pilot, this got my attention. He also had a C model. 

Time remaining will vary with throttle position. It's much faster to dry in cruise than while taxiing. 

Can't look these things up right now, just what I remember. 

[larryb]

I never touch the fuel selector on the ground. If I land on fullest tank it will still be fullest on takeoff. But I still check it with the checklist during run up.

[steingar]

I check first thing when I start my preflight and don't touch it again.  If the tank had gas when I looked at it it has gas when I'm taking off.

[Hank]

My checklist has Fullest Tank on Pre-Start. Even if only fullest, I still make sure it turns. 

[jetdriven]

Carbureted airplanes may run a while before starving of fuel, but the IO-360A in our J shuts down in about 3 seconds at cruise power if you turn the fuel selector off

Edited February 16, 2016 by jetdriven

[1964-M20E]

My check list has it 3 times, cabin pre-flight, before starting, and before run up, but it is one I generated from the original in the POH.  So as long as I do not pay it lip service and actually check it I should be good.  Like another said I land on fullest tanks and leave it there and usually I am getting fuel as well.

I also recommend not changing tanks after the run up you know the present tank is providing fuel.

[neilpilot]

40 minutes ago, larryb said:

 

I never touch the fuel selector on the ground. If I land on fullest tank it will still be fullest on takeoff. But I still check it with the checklist during run up.

Don't you drain the sump on the fuel selector during pre-flight (on the ground)?  As I understand the procedure, you need to pull the drain for both right and left.

[Hank]

5 minutes ago, 1964-M20E said:

My check list has it 3 times, cabin pre-flight, before starting, and before run up, but it is one I generated from the original in the POH.  So as long as I do not pay it lip service and actually check it I should be good.  Like another said I land on fullest tanks and leave it there and usually I am getting fuel as well.

I also recommend not changing tanks after the run up you know the present tank is providing fuel.

I don't move the fuel selector after I start moving on the ground. I've departed on a low tank before VFR, and climb 2000' or more before changing  (depending on how much was in the tank).

[M20F]

I set tank as part of pre-start checklist as I want to ensure the fuel is good.  Switching the tank right before take off changes you from a tank you know was good, full, and working to an unproven tank.  Likewise if there is a real need to change tank prior to landing I do it as part of my descent checklist, not on final as part of a GUMPS.  

[M20F]

One additional thing I reccomend is turning your fuel off with the engine running at least once.  This will give you an approximate as to what the line holds but also verify the fuel actually shuts off.  I have flown a fair number of planes that the fuel shutoff doesn't fully shut the fuel down.  

[N201MKTurbo]

When I was young and foolish, I let the airport owner use my plane.

He called one day and said that the engine quit right after takeoff. Well, he kind of crashed it a little bit. He landed back on the runway (with 5 people in the plane) with the right and nose wheels off the side of the runway. The propeller hit the asphalt and threw a chunk through the tail cone.

I had been turning the fuel selector off after every flight (I don't remember why). I figure he had to have started the plane up and immediately taxied to the runway and taken off without a run up. At that airport that could have been done in about 20 seconds. I asked him about that and he denied it, but others at the airport said that is exactly what he did. To say the least I got the keys back from him. His insurance paid for the repairs. I actually turned it into an overhaul, so I came out ahead. It cost about 10 AMUs (1986) to fix the damage.

The bottom line is the engine will run for about 20-30 sec with the selector turned off.

[Bob_Belville]

2 hours ago, jetdriven said:

Carbureted airplanes may run a while before starving of fuel, but the IO-360A in our J shuts down in about 3 seconds at cruise power if you turn the fuel selector off

Well, @ idle/taxi RPM it might run a long enough to get to the runway but like Byron's J my E will start sputtering in less than 15 seconds at cruise. I recently got caught in the middle of a tank switch by ATC or some other distraction. No big deal but there's not much time. 

[aviatoreb]

4 hours ago, neilpilot said:

Back in 2011 a local attorney picked up his C182 after having a BRS installed.  He took off with his fuel selector OFF and reportedly got to 300-400 AGL before the engine quit. He had critical injuries but survived.  C182 was totaled.  He used the BRS before the check cleared on his purchase.

http://www.thekathrynreport.com/2011/06/developing-plane-down-in-holly-springs.html

How horrible and horribly ironic.

[22 others]

This happened about a year ago, and in this case, I turned the selector to off when I put the bird up a few nights prior, which was unusual. (I don't do that any more) There was no mechanical problem i.e. worn detents etc. Not sure how I missed it in the pre-flight, but I did. 

I suspect that I would have discovered the mistake soon after take-off when the big fan added more drag than thrust.  That'd sure be a bone-head way to go, and I wanted to share my mistake in case it will be helpful to someone else.

The weather's supposed to be awesome this weekend. I might take go time how long it takes for the fuel to stop flowing to the engine. Just to satisfy my curiousity.

[N601RX]

I think the run time will vary considerably between fuel injection and carb as well as between different makes.  Fuel injection will cut off quickly as pressure drops, while the carb continues to run on what is in the bowl as well as from any fuel draining down from the fuel pump and line. Some makes even have the gasolator the firewall so there could easily be several ounces available. 19gph comes out to about .3 gallons per minute.  

[Hector]

At idle it takes a minute or two for a carbureted M20C. Don't ask how I know.

[DXB]

It makes sense to me that the answer here would be longer for carb'd engines with  float bowl reservoirs than fuel injected.  It would be interesting to kill the engine this way at cruise power (on the ground, of course) with an engine monitor that you could then pull the data from.  In theory, fuel pressure and fuel flow annunciators should give some decent interval of warning, at least in the carb'd setting, before the bowl empties and the engine quits?  This would also be nice warning right after the tank empties and might also be a tool to run one tank completely dry intentionally on a carb'd plane  to maximize range without having to deal with the stumble while you switch tanks?

On a related note, my C STILL has intermittent issues with the fuel pressure dropping to 0.0 in climb at WOT after I turn off the boost pump.  I've come up with detailed trouble shooting lists and begged a good MSC and one other shop to investigate, only to get the same response: "meh...carbed low wing planes do that."   What reassures me more is that when I pull the data off the JPI in every case, the WOT fuel flow doesn't budge when fuel pressure goes to zero.  I've only gone a max of 30 seconds with the 0 FP reading before I noticed and turned the boost pump back on, so the bowl might not empty, but the fuel flow should have dropped if pressure was really zero.  I think it's just that the pressure transducer sits much higher than the main fuel line and/or there is intermittent vapor lock in the fuel pressure line.   Sample FF vs FP trace below.   

[carusoam]

Nice detailed data, Dev.

The second part of this equation is fun...

You have hit on all the weird things that can happen to run out of fuel prior to take-off.  The M20C (and others) may do something else to you in a similar fashion...

When you have used most of the fuel out of both tanks, the fuel level indicators may be bobbing around less than reliably.  You select what looks to be the most full (or decide to leave it on the one you have been using).  In the traffic pattern everything is going swimmingly... Until you drop the nose.

The fuel pick-up is placed for the safety of departure.  It unports when you lower the nose.  Same procedure...maintain airspeed, switch tanks, fuel pump on, maintain airspeed...   Now how long does it take to get fuel to the carb..?

Its OK to be a CB, but don't be a CB while at the fuel pump.  Throw in an extra gallon or two in each side... Even on a really short post Maintenace flight.

Reliable FF connected to a totalizer is brilliant.  My next plane will have those digital fuel level devices as well.

Best regards,

-a-