How Long Will the Engine Run with Fuel Selector OFF

[Hector]

3 hours ago, Seth said: How do you know and please share your experience?

Not sure how Hector found out, but...

I tested my C's both position during a demo flight.  I taxied quite a distance to find that there wasn't a both position in a Mooney. 

There are supposed to be detents that would have given a hint.  But there weren't any of those either.

Best regards,

-a-

I flew down to Miami (KTMB) for the weekend and while tying down the Mooney after fueling I noticed a fuel drip from the fuel pump. About a drop every 8 seconds. Made a mental note to send the pump in for overhaul when I returned home next day. Not wanting to let the plane sit overnight dripping fuel I placed the fuel selector valve in the off position thinking it would eventually stop dripping. Early next morning got to the airport, did a quick preflight (did not pull the ring to check the sump nor checked the position of the selector valve) jumped in and started the engine. Within a minute or so I had the ATIS and was calling ground for taxi instructions. Started taxing out of Landmark when the engine quit right at the entrance to their ramp blocking all traffic. Checked the mixture, turned the pump on (which sounded a little strange with no fuel), hit the starter.....nothing. Now the ground controller is asking what's going on and I have no clue. I'm thinking there is something wrong with the pump because it's making a different noise than usual. Go through the starting checklist again while watching the Landmark guys approach ready to tow my ass out of the way when it finally clicked and it all made sense. With the fuel selector valve now on the engine started with no problems. The main lesson learned was nothing about the selector valve, but how a hurried, half-ass preflight inspection lead to a problem than under different circumstances could have cost me a lot more than some embarrassment. Also, if you are going to use a checklist, you must read it "deliberately" thinking about each step and not just go through the motions.

[Guest]

5 hours ago, Hector said:

I flew down to Miami (KTMB) for the weekend and while tying down the Mooney after fueling I noticed a fuel drip from the fuel pump. About a drop every 8 seconds. Made a mental note to send the pump in for overhaul when I returned home next day. Not wanting to let the plane sit overnight dripping fuel I placed the fuel selector valve in the off position thinking it would eventually stop dripping. Early next morning got to the airport, did a quick preflight (did not pull the ring to check the sump nor checked the position of the selector valve) jumped in and started the engine. Within a minute or so I had the ATIS and was calling ground for taxi instructions. Started taxing out of Landmark when the engine quit right at the entrance to their ramp blocking all traffic. Checked the mixture, turned the pump on (which sounded a little strange with no fuel), hit the starter.....nothing. Now the ground controller is asking what's going on and I have no clue. I'm thinking there is something wrong with the pump because it's making a different noise than usual. Go through the starting checklist again while watching the Landmark guys approach ready to tow my ass out of the way when it finally clicked and it all made sense. With the fuel selector valve now on the engine started with no problems. The main lesson learned was nothing about the selector valve, but how a hurried, half-ass preflight inspection lead to a problem than under different circumstances could have cost me a lot more than some embarrassment. Also, if you are going to use a checklist, you must read it "deliberately" thinking about each step and not just go through the motions.

One clue that the selector was off should have been a lack of fuel pressure when you turned on the pump.  I catch some of my maintenance guys in the same mistake right after annual, some catch it quickly, some don't.

I was taught to look for the an appropriate reaction when something is changed, like a switch. Another thing was to start the plane without a headset on, lots of things to be heard while starting.

Clarence

 

[Shadrach]

On March 1, 2016 at 5:43 PM, M20F said:

If  I run for example left tank dry, land, refill left, start on the right, and the flip to the left it coughs and sputters a fair amount.  It doesn't die and after 4-5 seconds its smooth again.  That may be just coincidental to mine but your results may not always be the same.

I was thinking about this and the difference is likely that running a tank dry puts air in the system where as cutting fuel with selector likely causes a vacuum in the line for stern the selector and the mechanical fuel pump.

[carusoam]

The O didn't get a fuel pressure gauge.  FF is a pretty good alternative...

Best regards,

-a-

[Andy95W]

Not sure about the fuel injected engines, but I just checked this today before flying my M20C.

Fuel selector off, Electric Fuel pump on.  Pump definitely had a different sound than normal. No fuel pressure indication, just like Clarence said.

Engine started just fine, 1000 rpm, leaned for ground operation.  No fuel pressure indication.

1 minute: engine starts to stumble.

1 minute 10 seconds- engine is so rough I switch to right tank.  Engine smoothed out within 2 seconds, got normal fuel pressure indication in about 5 seconds.

Lesson learned for me: don't attempt a takeoff within 1 minute of engine start or tank switch.

[Bob]

Years ago a Mooney departed Clow airport lifted off and slid into an intersection, marked by the red "X", below.  I remember the reports at the time that included an interview from the mechanic that was the first aviation knowledgeable person on the scene and he arrived just after the impact.  The mechanic stated that he found the fuel selector in the off position or "between tanks".  The Mooney, N5641Q, departed 18 on a 3300ft runway at 1C5. Lifted off and lost power.  If I remember properly, the pilot said that he fueled and switched tanks before departing.

The accident ended very well, the plane missed all the late rush hour cars, only hit a parkway tree with the wingtip and both pilot and passenger had only minor injuries.

Hope this give one real scenario for this thread.  Unfortunately I am unable to share the NTSB report. The very interesting thing is that the NTSB report is now missing.  A Google search also offer almost no help.  https://www.google.com/?gws_rd=ssl#q=n5641q+ntsb  This is not a suggestion for a conspiracy theory, I did read the report years ago.  I understand that my above information is contradicted in this link, however what I added has come from my memory of the NTSB report and at the same time I wanted to share one of the few news reports still available on the net.  http://www.mysuburbanlife.com/2008/09/18/two-injured-in-bolingbrook-plane-crash/z51wffn/?page=1

[Cyril Gibb]

On 2016-04-06 at 11:39 PM, N1395W said:

Not sure about the fuel injected engines, but I just checked this today before flying my M20C.

Fuel selector off, Electric Fuel pump on.  Pump definitely had a different sound than normal. No fuel pressure indication, just like Clarence said.

Engine started just fine, 1000 rpm, leaned for ground operation.  No fuel pressure indication.

1 minute: engine starts to stumble.

1 minute 10 seconds- engine is so rough I switch to right tank.  Engine smoothed out within 2 seconds, got normal fuel pressure indication in about 5 seconds.

Lesson learned for me: don't attempt a takeoff within 1 minute of engine start or tank switch.

I was curious about the engine run with an injected engine because it doesn't have a fuel bowl to extend the fuel time.  When I change tanks, I do it as quickly as possible, maybe a 2 second process, without seeing any variation on fuel pressure.

I tried it on my M20F today at cruise.  I turned off the fuel selector and the fuel pressure didn't move for about 8 seconds.  For the next 8 seconds or so, the pressure started to slowly drop until the engine power dropped off just after the needle went below the green pressure range.  So on my plane, there's no discernible engine power reduction until about 16 seconds, give or take a few.  For an injected engine, you wouldn't be able to takeoff in that short a time.

 

[Andy95W]

Did you try running it at idle with fuel off just to see worst case scenario?

Single pilot, light fuel load, I bet my takeoff roll is less than 16 seconds.

[Cyril Gibb]

9 hours ago, N1395W said:

Did you try running it at idle with fuel off just to see worst case scenario?

Single pilot, light fuel load, I bet my takeoff roll is less than 16 seconds.

The 16 seconds was at cruise in flight, about 9 GPH.  At full rich takeoff power, The fuel flow is about 18 GPH.

The absolutely worst case (and really really dumb) scenario would be to line up, shut the fuel off and hit the throttle immediately. The engine should  lose power in less than 10 seconds.  No way I'd be off the ground in that time.  If the fuel was shut off in the taxi beforehand, even less so.  Unless it was a super short taxi and zero runup, I doubt you'd even be able to start the takeoff roll.

Good question though.  Next time at an uncontrolled field with a longish runway I'll try the lineup, shutoff and roll timing.

 

[Guest]

I don't know how one could start the engine, taxi out, warm the engine, do anything like a real run up check of the engine and make it to a runway to attempt a takeoff let alone get airborne with the fuel selector off.  

If you're able to get airborne with the selector off, you missed a few steps along the way.

Clarence