Switch Tanks, Switch Tanks, Switch Tanks!

[FloridaMan]

On 6/17/2018 at 11:06 AM, DAVIDWH said:

A few years ago there was an FAA accident report of a pilot running a tank dry then switching tanks. Engine never restarted and pilot was killed.

FAA  findings were blocked injectors due to bottom tank debris sucked in from dry tank. 

Personally,  I stopped doing it after reading this report.

Were there no screens anywhere in the fuel system!?

Next time you've got a tank that's pretty low, look through your fuel cap towards the bulkhead and you can see your fuel pickup. It looks like this. Note the screen; it's hard to see with the image contrast:

That's the first line of defense against contaminants. Also note how high it is from the bottom of the tank and truly how much water has to be in the tank to get it into your fuel system. Your drain has to be really screwed or sealant on your bulkheads must really not allow anything to pass under them to allow water into that pickup. 

Then, inside your fuel servo there's a finer screen that would catch things that either made it through the pickup or were introduced elsewhere:

If a contaminant made it through that screen, it would pass easily through the injectors. Either someone left screens out in that accident airplane, the contaminant that clogged the injectors originated from within or past the fuel servo, or the cause of the accident was not blocked injectors. 

[jaylw314]

On ‎6‎/‎17‎/‎2018 at 11:55 AM, Mooneymite said:

I agree that we don't, but just as airline pilots are trained in CRM, I think that GA pilots can learn it too.  CRM is not just about a co-pilot.  It is a systematic inclusion of all one's resources.

Single pilot CRM.....what a concept!

Here's a start

[squeaky.stow]

On 6/17/2018 at 1:34 PM, Mooneymite said:

Every time the discussion of running out of fuel comes up, I think about how few Jets run out of gas.  Not to say it doesn't happen, but it's rare.  At the airlines, it is extremely rare and usually the result of a long chain of events which may not have had anything to do with fuel planning at all.

Is this just a matter of experience, or are there other factors?

Experience certainly helps but it really comes down to 3 things:

1) Incredibly accurate fuel planning. At my airline (yes, the one of Gimli Glider fame) the planned fuel burn calculated by our flight planning system is usually accurate to about 100kg on a 10 hour flight that will burn about 50,000 kg of fuel.

2) Extremely accurate fuel Totalizers. The "cost to carry" excess fuel is a big deal in the airline world, so we carry exactly what we need and no more. That translates to destination + alternate + legal reserves plus a statistically determined "contingency fuel" for unforeseen events. Then we add deviation fuel in minutes of additional burn for known weather or ATC delays.

3) SOPs. Airline pilots live and die by SOPs. You have an estimated and a minimum fuel quantity at every waypoint on your flight plan which you monitor throughout the flight. If your burn exceeds your plan, you spot it early and come up with a plan. You always have an out, and you exercise it when it is required. 

All of the above can be applied to my Mooney. The only difference is the somewhat lower degree of accuracy of items 1 & 2, which can be compensated for by adhering strictly to item 3. Most GA fuel exhaustion accidents I have read about were the result of either not having a fuel plan, or failing to follow it. 

Minor trivia note: Years ago I was instructing in the 767 simulator and we had to review the dual engine failure drill as part of the recurrent training scenario. I made some comment about it being good training but extremely unlikely that it would ever happen. "I mean, have any of you ever had a dual flameout?" I asked. The Captain was a quiet and very competent old guy, very close to retirement. He smiled and said, "Actually, yes I have." 

His name was Maurice Quintal. Everyone at Air Canada knows the name Bob Pearson, the famous Captain of the Gimli Glider, but few remembered the name of his FO. It was Maurice. 

[FloridaMan]

Not to blow too much sunshine: I tout the efficiency and range of Mooneys as a safety factor over cherokees and 172s. Most Mooneys carry at least six hours of fuel and travel fairly quickly, meaning winds affect them less and an hour of extra gas can get you a lot further than other light GA singles. Compared to a Cherokee 180 that may carry four hours of fuel, a 25kt headwind can consume your reserves and if your destination is socked in can make it tough to reach your alternate. 

[kortopates]

7 hours ago, Antares said:

Were there no screens anywhere in the fuel system!?

Next time you've got a tank that's pretty low, look through your fuel cap towards the bulkhead and you can see your fuel pickup. It looks like this. Note the screen; it's hard to see with the image contrast:

That's the first line of defense against contaminants. Also note how high it is from the bottom of the tank and truly how much water has to be in the tank to get it into your fuel system. Your drain has to be really screwed or sealant on your bulkheads must really not allow anything to pass under them to allow water into that pickup. 

Then, inside your fuel servo there's a finer screen that would catch things that either made it through the pickup or were introduced elsewhere:

If a contaminant made it through that screen, it would pass easily through the injectors. Either someone left screens out in that accident airplane, the contaminant that clogged the injectors originated from within or past the fuel servo, or the cause of the accident was not blocked injectors. 

Nice photo's of the screens. But recognize not all fuel servo's have a screen. For example the TSIO-360's don't. But we all have a gascolator and a very tight mesh final screen in the fuel divider which will capture anything larger than piece of lint sized debris which is why many if not most blocked injectors occur from maintenance rather than debris that traveled through the fuel system. 

[HRM]

8 hours ago, steingar said:

I never take off without at least an hour in both tanks.  For me to change I have to unbuckle my seat belt, lean all the way over and hunt around for the switch.  I sit with the seat full forward, and can't see it with the belt on.  I've done it in flight, but I have the autopilot or my passenger fly the aircraft while I do.  I will definitely never attempt it in IMC without the autopilot engaged, I have to take my eyes off everything and bend all the way over, wonderful way to induce spatial disorientation.  

I'll go with partial tankfuls for buzzing around the Delta (KBPT), but for any cross country, full tanks only. One of the great things about being an aging pilot is the automatic three-hour time limiter that forces landing. No audible alarm, just a gentle, increasing urgency that enforces a landing procedure long before the fuel tanks are emptied.

[carusoam]

Harley, great silent alarm... but it is followed up by a pretty soggy urgent reminder... 

Nice in tank pics, Antares!

Grear Gimli glider training / relevant story, Squeaky...

Mooneys are getting similar fuel quantity accuracy lately...  One part digital FF / totalizer technology for knowing how much was used... and the other part Cies digital fuel gauges...very accurate at knowing how much is on board...

Combining the FF, amount of fuel, and the GPS distance to the destination... Mooney pilots are getting better at keeping extra fuel in the tanks...

Thanks to MS, we are aware of these really cool devices (Cies) and fixing the old devices too... seen how to install them (Terry), got a feel for their accuracy (Marauder), I even have somebody supplying insight for how to do this on my plane (Deb)...

Best regards,

-a-

[gsxrpilot]

12 hours ago, skydvrboy said:

What is this simpler process?  My process (not that it is approved by anyone anywhere) is to run 15 - 30 minutes off my right tank (just to make sure fuel doesn't dump w/expansion), then switch to the left.  I run that tank until it has 10 gallons of fuel left, which becomes my reserve.  I then switch back to the right tank, knowing that if it ever runs out, I it's time to put it down and get fuel, ASAP.  I also don't switch tanks prior to landing unless I am getting low in my right tank.  Fuel management is one reason I do this, but the other is that my plane tends to roll to the left.  By intentionally creating an imbalance in the tanks, it doesn't take as much control input to fly straight.

Your process is pretty simple... and fairly close to what I do. 

I do everything based on gallons used, to minimize switching tanks, and never to be switching tanks in the pattern or on approach.

Start on the left tank and burn 15 or 20 gal (35 gal tanks). Then switch to the right and run it all the way dry. Switch back to the left where I have 15 gal and should be on the descent to land. Obviously there are variations to this if I'm not going as far. I will switch to the fullest tank either at top of descent or within 10K ft of the ground. But I never change tanks more than twice during any flight and often only once.

I'll flip this procedure left to right occasionally.

Benefits I see to this procedure:
Upon landing with an empty tank, filling that tank will give me an EXACT value of useable fuel. (I really only care about useable fuel when in cruise attitude in flight, that's when it matters)
I learn what my gauges read as the tank is going dry.
I know what the engine sounds like and syptoms of fuel starvation.
Gain the confidence that fuel starvation from one tank is not a cause for panic and build muscle memory to switch tanks as soon as those symptoms appear.
Landing with 10 gal all in one tank is more comfortable than landing with 5 gal in each tank.
Basing the procedure on gallons and not on time has me paying closer attention to fuel and removes an additional variable from the equation.
The math is also simpler... 

I like to go far and especially when solo, like to see how far I can go non-stop. It's just what I enjoy. This procedure has allowed me to go much further with much more confidence in my fuel situation. I expect to know anytime I pull up to the pump, to 1/2 gal per tank, what it will take.

[glafaille]

I agree with gsxrpilot.

I use a similar procedure:  Run one tank for the first hour including taxi and climb, switch to second tank and run that one dry, switch back to the first tank which now has 1 hr and 30 min fuel remaining.  I should be in a descent to my destination when I make the final switch.  

With fuel at the tabs I use the same procedure except the intial switch is done at the top of climb.  This way I am left with 1 hr and 30 min in the initial tank, just like before.  Any time I switch back to the first tank I should be very close to my destination, (within 30 min).

Edited June 20, 2018 by glafaille

[sgrooves]

As someone who has never let my tanks run dry, or had an in-flight shutdown, is the procedure just switching the tank with the boost pump on? If you get to the tank late and the engine dies, is switching tanks with some boost enough to get it started again (assuming the prop is still windmilling)? Or do you need to get the mags back to start?

[gsxrpilot]

16 minutes ago, sgrooves said:

As someone who has never let my tanks run dry, or had an in-flight shutdown, is the procedure just switching the tank with the boost pump on? If you get to the tank late and the engine dies, is switching tanks with some boost enough to get it started again (assuming the prop is still windmilling)? Or do you need to get the mags back to start?

I've found this varies with altitude. When I flew an M20C, I never used the electric pump to restart in the air. The engine quits, just reach down and switch tanks, and the engine immediately comes back to life.

With my Turbo 252, I generally need a bit of Low Boost pump if restarting above about 15K ft. The further up in the flight levels, the more boost I typically need to restart. Below 12K I've never used any boost when restarting. 

Having said all of that... I've NEVER used any boost pump or other pump when just switching tanks in any Mooney at any altitude. Evidently some POH's say to turn on the pump when switching tanks, other POH's leave that step out. Since the engine comes back to life so quickly after running a tank dry and the engine quits, there doesn't seem to me to be any reason to run any pump during the same procedure when the engine IS running.

Anyway... that's my experience.  It's a 1000 hours between an M20C and an M20K with a few hours in E, F's, J's, Ovations, and Acclaims.  I know, I know... that's still rookie territory for some old timers on this board. 

[skydvrboy]

43 minutes ago, gsxrpilot said:

Since the engine comes back to life so quickly after running a tank dry and the engine quits, there doesn't seem to me to be any reason to run any pump during the same procedure when the engine IS running.

I was wondering the same thing.  I learned in a Piper Warrior and was taught to always flip the boost pump on, then change tanks.  That was the same procedure for switching tanks or engine problem.  That habit carried over to my Mooney, flip the switch, change the tank.  I've always wondered if it was necessary as the engine comes back to life immediately upon switching tanks.  On the other hand, it only takes about a second to flip the switch first, so I can't see any concern with doing it that way unless there is a problem with running the boost pump dry?

[gsxrpilot]

Those boost pumps don't last forever. So I don't use it when it doesn't make sense to use it. I'm not sure if my concerns are valid, but I just haven't found a reason to use it.

[Hank]

Me, too--never used the fuel pump when switching tanks, just lean down and turn it. Run dry once, engine quit running at 9500 msl--airplane pitched down strongly to maintain trimmed airspeed; switched tanks and it immediately restarted. Almost run dry once, just a cough or two on descent, switched and immediately smooth. I don't wait to be "over and airport" either--how hard is it to switch back to the other tank, figure remaining endurance and look for a good airport with fuel?

[jaylw314]

29 minutes ago, gsxrpilot said:

Those boost pumps don't last forever. So I don't use it when it doesn't make sense to use it. I'm not sure if my concerns are valid, but I just haven't found a reason to use it.

Does the engine driven fuel pump suffer if it is pumping air? 

[carusoam]

That procedure must have been written based on some extension of theory.... 

There are a couple of things possibly going on under some circumstances...

• air bubbles and vapor bubbles entering the fuel line...
• Something else may have caused the FF to stop... mechanical fuel pump failing?

 

• The engine is pulling the fuel at a high rate and then it is pulling a mixture of fuel, vapor and air... would running the two fuel pumps aid in getting fuel flowing again, reduce vapor, or get rid of air bubbles?
• flipping the tank selector valve quickly between two full tanks... the engine will never know it happened under normal conditions...

Also keep in mind there is a fuel return line on some Continental fuel systems... excess fuel pumped by the electric pump may return some air, vapor, or fuel back to the tank(?).  This is known from hot start techniques setting up for having empty fuel lines...

I usually follow the procedure on this and watch the FF gauge as well...

PP thoughts only, Not a mechanic or CFI...

Best regards,

-a-

[Skates97]

28 minutes ago, Hank said:

Me, too--never used the fuel pump when switching tanks, just lean down and turn it. Run dry once, engine quit running at 9500 msl--airplane pitched down strongly to maintain trimmed airspeed; switched tanks and it immediately restarted. Almost run dry once, just a cough or two on descent, switched and immediately smooth. I don't wait to be "over and airport" either--how hard is it to switch back to the other tank, figure remaining endurance and look for a good airport with fuel?

Same here, I just switch tanks and keep an eye on the fuel pressure to make sure it stays constant.

[jaylw314]

1 hour ago, gsxrpilot said:

I've found this varies with altitude. When I flew an M20C, I never used the electric pump to restart in the air. The engine quits, just reach down and switch tanks, and the engine immediately comes back to life.

With my Turbo 252, I generally need a bit of Low Boost pump if restarting above about 15K ft. The further up in the flight levels, the more boost I typically need to restart. Below 12K I've never used any boost when restarting. 

Having said all of that... I've NEVER used any boost pump or other pump when just switching tanks in any Mooney at any altitude. Evidently some POH's say to turn on the pump when switching tanks, other POH's leave that step out. Since the engine comes back to life so quickly after running a tank dry and the engine quits, there doesn't seem to me to be any reason to run any pump during the same procedure when the engine IS running.

Anyway... that's my experience.  It's a 1000 hours between an M20C and an M20K with a few hours in E, F's, J's, Ovations, and Acclaims.  I know, I know... that's still rookie territory for some old timers on this board. 

I'm guessing when you switch tanks, while the switch is in between tanks the pressure in the fuel lines start dropping, with maybe the possibility of cavitating or introducing air?  Seems unlikely if you switch quickly enough though.

[N201MKTurbo]

1 hour ago, jaylw314 said:

I'm guessing when you switch tanks, while the switch is in between tanks the pressure in the fuel lines start dropping, with maybe the possibility of cavitating or introducing air?  Seems unlikely if you switch quickly enough though.

With a lycoming fuel pump, the pump actually contains a bit of fuel. When you are between tanks no fuel flows into the pump and the spring pushes the fuel out of the chamber. As the spring gets longer it’s pressure gets lower. When the fuel is flowing again the pressure comes back to its normal value. That’s why the pressure dips when you switch tanks.

[Seth]

On 6/17/2018 at 9:05 AM, N201MKTurbo said:

On my ATP checkride in that gawd awful Seneca. The examiner discreetly reached down between the seats and shut the fuel off to one of the engines. When it quite I reached down and switched tanks which turned the fuel back on. 

He was a bit mad and said he wanted to see how I would handle an engine failure. I said I did.

An instructor did that on my first twin training ride in a Seminole.  I guess it happened to him too!

I LOVED your verbal response.

-Seth

[N201MKTurbo]

28 minutes ago, Seth said:

An instructor did that on my first twin training ride in a Seminole.  I guess it happened to him too!

I LOVED your verbal response.

-Seth

Yes, he lost the sense of surprise. I did the skill on my timeline not his.

[29-0363]

 

 

A very sobering story to remind pilots that the fuel you pumped in the day before might not be there next morning.

The pilot of the Lancair had built the aircraft as an owner-builder. He and his passenger had intended to fly from Perth, Western Australia to an airshow at Mangalore, Victoria. On the day prior to the accident, the aircraft arrived early in the afternoon at Aldinga, South Australia, where it was refuelled in preparation for the next leg of the flight. The pilot and passenger then stayed overnight with a friend. The following morning, the aircraft departed for Murray Bridge, South Australia in order to meet up with another aircraft for the remaining flight to Mangalore.

When the aircraft was 3 km to the north-east of Aldinga aerodrome, witnesses heard the engine surge and lose power. The aircraft was then seen to enter a spin and crash into a dry creek bed. Both occupants were fatally injured. The accident was not considered to be survivable.

Traces of aviation fuel were found on the ground at the accident site under the wing fuel tanks. There was no evidence that a significant quantity of fuel had been released during the impact. There had been no post-impact fire.

The investigation established that the aircraft had been refuelled the previous day at Aldinga to a capacity of approximately 80L. It was operating within weight and balance limitations, close to its maximum weight, and close to the aft limit of its centre of gravity. There was no evidence to suggest that the aircraft was not airworthy prior to the accident, nor was there any indication that either the pilot or the passenger had been incapacitated immediately before the accident.

The aircraft utilised three fuel tanks: one was located in each wing below the level of the engine, while the third fuel tank was located in the fuselage, above the level of the engine. The engine could be fed with fuel directly from any one of these.

It was the pilot's normal policy to use fuel from the fuselage tank when priming the carburettor prior to starting the engine, and then to select a wing fuel tank once the engine had been started. During the flight from Western Australia, only the wing fuel tanks had been filled at all refuelling ports except for Ceduna, where it was not possible to ascertain how the aircraft had been refuelled. Investigation revealed that at the time of the accident, the low-fuel warning light for the fuselage tank was illuminated, indicating that only a small quantity of fuel remained in that tank.

The investigation found that aviation fuel had been spilled on the ground, chemically burning the grass, at the aircraft's overnight parking location at Aldinga aerodrome. The shape of the burnt grass area was consistent with fuel having been spilled over the sides of a 20 L fuel drum. Police reported that fuel had been stolen on other occasions from aircraft at Aldinga aerodrome. A road near the aerodrome was regularly used for car racing, and it is possible that fuel was siphoned overnight from the aircraft's fuel tanks.

[Skates97]

1 hour ago, 29-0363 said:

A very sobering story to remind pilots that the fuel you pumped in the day before might not be there next morning.

Even if I know how much fuel what was in my plane when I locked it up in my hangar I always dip the tanks and check it before the next time I fly. It doesn't take long to verify actual fuel during pre-flight and I can see no reason not to.

[EricJ]

We sometimes fly to Desert Center when we have a race event at the adjacent Chuckwalla Valley Raceway, which is a fairly remote private field with not very much air traffic.   My friend had 10 gallons (two five gallon jugs) taken from one wing overnight the last time we were there.   The dumbest part is that the track sells 95 and 101 octane unleaded and 110 octane leaded on site.  So it's just cheap bastards willing to endanger somebody else.

I just put in an EDM-900 and CiES senders, which makes it a lot easier to detect that kind of stuff.

Thieves suck.  Really sorry to see that it went so badly for somebody.

[steingar]

My M20c has brand newgas caps thanks to a Mooneyspace denizen. They are the stiffest caps I’ve ever seen. To get them open I have to pry with a screwdriver (wrapped in a towel). And I still check the tanks before every flight.