What is your fuel minimum?

[201er]

What is the absolute minimum amount of fuel you will take off with no matter how close you fly? Land with? What kind of Mooney and what's the climb and cruise fuel flows? What do you use to verify that minimum fuel?

[201er]

I want to start by saying that my minimums tend to be fluid and not rigid because each day and flight can vary. Some flights are sketchy and it would be crazy not to have a lot of extra fuel and some flights are a near sure-shot (like around the pattern or the airport next door). Furthermore, my own personal condition, proficiency, and gut feeling can vary. I evaluate my minimums on a flight by flight basis.

Another reason it is hard for me to answer is because it depends very much on where the fuel is. I'd be far more worried about having 16 gallons with about 8 a side than to have 14 gallons all in one tank.

Another factor is how confident I am in my fuel measurements (especially because I have extended range tanks). If I just pumped a certain amount of gas into a dry tank and dipped it, I would be a lot more confident in that measurement error than if I had just run the tanks from 100 gallons down to 20 gallons with multiple fuel additions along the way.

My typical minimum is that I don't want to be expecting to arrive at any airport with less than 20 gallons and at least 15 of them being on one side and be on that side when landing. If weather is sketchy or I'm not at my best or anything else, it goes up from there. So my usual, not giving it a whole lotta thought, minimum for a takeoff for a very short flight would be 25 gallons.

However, if talking about an absolute minimum and a good confidence that the fuel is only at or above my measurement (known error), I suppose that if I were forced to take 3 of Marauder's favorite girls around the pattern one time in perfect circumstances (big airport, not much traffic, good wx), I could be convinced to go to arrive with 10 gallons (all on one side) and depart with not less than 15 gallons on one side. In other words, when there's less than 15 in the fullest tank, I don't care what's in the other tank, it doesn't even count.

I am horrified to think that by the FAA definition, it could be legal to takeoff a J with what, 7 gallons? 2 gallons for a 5 minute flight and a reserve of 5 gallons (30 minutes at 10gph)!? Not saying I want any more rules imposed to control this. Maybe in some ultralight with a 1 hour total endurance, a half hour is a generous reserve. But in our planes, 5 gallons can just get magically lost out of a seep, vent leak, and some generous sumping!

I fly a '78 J. Typically burning 18gph on takeoff, 9gph in cruise. So even arriving with 10 gallons is over an "hour" reserve.

That said, I rarely even see 20 gallons remaining. With 100 gallon tanks, it's not uncommon to depart full fuel for a cross country and be topping it off after arriving with 35. I like to have generous alternate options and not to be relying on myself not to do something stupid.

Edited May 22, 2017 by 201er

[Godfather]

I also fly with 100 gallon tanks and have landed with as little as 11 (2 and 9).  Even if it is a short hop I make sure 25 gals are available.  The R can really burn the fuel but on short hops I'm pulling back on the go stick after 2-3 mins. 

[Hank]

My nearest fuel is 10.4 nm away. I took off once with just under 10 gal, and had to sit and wait almost an hour for the only person working on Saturday morning to come back and fill me up  (full serve only , $3.35). It wasn't worth the risk to try going another 15 nm to the next field. When they are closed, my other option is about 20 nm the other direction, across a 40,000+ acre lake, so I'd never go there that low.

My minimum landing is one hour (9 gal). I've made two long flight where I had between 11 and 12 gal remaining, have no desire to be airborne longer. Departing partial fuel is routine--stick the tanks before departure, plan to have fuel required plus an hour. 

Like Mike, I burn 9 gal/hour, but I have no problem taking off with less than 25 gal (half tanks for me!). Apparently flying a tanker has affected his risk perception . . . .

[carusoam]

One hour per side... easy math/time keeping this way.

Back in the day, I liked pushing the limits of engineering time studies around the traffic pattern. I found the limitation where the attitude of the plane points down hill on final approach.  Point more down hill, the engine goes silent, as fuel runs away from the pick-up...

Short on dough, lacking instrumentation, and being really intelligent, isn't a very good combination... 

Don't push the limits because you are smart. The limit may move closer to you while you are watching something else...

Best regards,

-a-

 

[gsxrpilot]

I'm with @201er in that I like my fuel all together in one tank rather than split between two tanks. The last flight I made in my 252 was with 15 gallons in the Left tank. The right tank was completely dry. And I know that as it had just been stripped but not yet resealed. The flight was only about 15 minutes, takeoff to landing.

So I'll say 15 gal is probably my minimum but I need that in one tank. 7 in one tank and 8 in the other won't get it done. I need a minimum of 15 gal in one of my two tanks.

[Skates97]

If I'm not going far (pattern work, practice area, 30 minute hop to a local airport) I will take off as long as I have at least 10-15 in one tank. If it is any decent distance I am taking off with full tanks or ensuring at least a 1hr fuel reserve.

[Rick Junkin]

1 hour ago, 201er said:

What is the absolute minimum amount of fuel you will take off with no matter how close you fly? Land with? What kind of Mooney and what's the climb and cruise fuel flows? What do you use to verify that minimum fuel?

Minimum take off fuel: 24G split evenly left and right. The M20M TLS POH has a note that takeoff has not been demonstrated with less than 12G in the selected tank. Therefore, I want at least 12G in my selected tank, and 12G in my "backup" tank. I've only had the airplane for a year, but the least fuel I've taken off with is 36G split 20/16 left and right according to the external gauges on each wing. I've verified the accuracy of those gauges, and they are +/-1G. And I cross-check them with my fuel burn for each sortie.

Minimum landing fuel: 12G in a single tank. I don't have a reference for this, but my reasoning is that if I have to go around, I need at least the minimum demonstrated take off fuel in one tank and have it selected. And then stick the next landing. I nominally flight plan to land with at least 20 gallons. All that being said, if I got myself into a corner on fuel while airborne... well, like all of you, I'd do what I had to.

M20M TLS climb fuel flow is 26GPH at 34/2400, cruise for me is 16.5-17.0 at 28/2400 and 120ROP. Of course that means that if I take off with only 24G, and stay VFR, I'm only legally going about 150 miles, and hardly making it around the pattern to land with my customary 20G.

Cheers,
Rick

 

[aaronk25]

Land with no less than 10g on board in ideal weather conditions. My take off fuel load reflects the necessity to land with 10g.

In poor conditions I want 20 gallons on board at time of landing but this is fluid based on many items.


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[Bob - S50]

I don't know how to vote.  My minimum fuel is to have enough to get to my destination and land with 10 gallons.  So what's my minimum fuel for takeoff?  Practically speaking, the plane never sits in the hangar with less than 30 gallons by agreement among the partners.

[epsalant]

Great question.  I agree with 201er that "it depends".  Weather is a HUGE factor.  I also want to point out that

THERE IS NO SUCH THING AS "JUST FLYING IN THE PATTERN".

When someone else in the pattern lands and gets a flat tire in the middle of the runway (or worse) you are going elsewhere...

So it also depends on distance to nearest alternate...you did inquire about that airport in your briefing to make sure no unsafe conditions there, right ?

Where I fly (KLDJ) there are tons of airports close by.  Also depends on certainty of amount of fuel.  Fuel totallizers are great, but depend on accurate user input.

I am more confident if, e.g. I see 25 gallons of fuel in a tank than if the fuel totally tells me there is a 26 gallons that I can't measure because it's 13 in each tank...

[Pritch]

On Friday 4 miles south of KRDD (Redding, CA) a Cessna crash landed from running out of fuel.  The only time you have to much fuel is if you are on FIRE.  I personally will never go below 35 gal. The older I get the more cautious I get.

Pritch

 

[RLCarter]

2 hours ago, Bob - S50 said:

I don't know how to vote.  My minimum fuel is to have enough to get to my destination and land with 10 gallons.

I agree, depends on the mission

[201er]

39 minutes ago, Pritch said:

The only time you have to much fuel is if you are on FIRE.

Or overweight and don't make it off the runway or worse yet just barely make it off and then spin in!

[neonbjb]

Absolute minimum for me is to get there + VFR minimum at climb fuel burn (~16GPH in my C at my home altitude) - so 8 gallons if I'm just going to do a pattern hop. I would never go that low if it wasn't for my fuel flow gauge though.

[Mooneymite]

I was flying a tail-dragger and kind of stretched my min fuel once.  When I landed, the airport manager told me they had plenty of fuel, but no method of delivering it....the fuel truck was broken.

This experience makes me consider what I would feel comfortable with if I had to go to an alternate airport for fuel.

There are few things on earth that move as fast as fuel gauge needles as they approach 'E'.

[75_M20F]

15 hours ago, gsxrpilot said:

I'm with @201er in that I like my fuel all together in one tank rather than split between two tanks. The last flight I made in my 252 was with 15 gallons in the Left tank. The right tank was completely dry. And I know that as it had just been stripped but not yet resealed. The flight was only about 15 minutes, takeoff to landing.

So I'll say 15 gal is probably my minimum but I need that in one tank. 7 in one tank and 8 in the other won't get it done. I need a minimum of 15 gal in one of my two tanks.

What's the reason for wanting all the fuel in one tank vs having fuel in two tanks? Is it due to concern of running one dry at a critical moment?

It would seem you are giving up some redundancy.

(I will also add that I never land with less then 1 hr per side. So 2 hrs of fuel total)

Edited May 22, 2017 by Mooney_Mike

[gsxrpilot]

2 minutes ago, Mooney_Mike said:

What's the reason for wanting all the fuel in one tank vs having fuel in two tanks? Is it due to concern of running one dry at a critical moment?

It would seem you are giving up some redundancy.

(I will also add that I never land with less then 1 hr per side. So 2 hrs of fuel total)

Generally I would always fly with fuel in both tanks. But towards the end of a long trip, I believe 10 gallons in one tank is safer, more useable, etc, then 5 gal Left and 5 gal Right. The tank is less likely to suck air in a turn, I've got more margin for error of quantity calculation, etc. Bottom line is that if I'm down to my last 10 gallons, I'd like it to be all in one tank rather than some in one tank and some in the other.

[75_M20F]

Just now, gsxrpilot said:

Generally I would always fly with fuel in both tanks. But towards the end of a long trip, I believe 10 gallons in one tank is safer, more useable, etc, then 5 gal Left and 5 gal Right. The tank is less likely to suck air in a turn, I've got more margin for error of quantity calculation, etc. Bottom line is that if I'm down to my last 10 gallons, I'd like it to be all in one tank rather than some in one tank and some in the other.

Okay, that makes sense if one is trying to maximize range.

[RobertGary1]

4 hours ago, Pritch said:

On Friday 4 miles south of KRDD (Redding, CA) a Cessna crash landed from running out of fuel.  The only time you have to much fuel is if you are on FIRE.  I personally will never go below 35 gal. The older I get the more cautious I get.

Pritch

 

That's such a cessna thing to say. In 20 years I can probably remember each time I've ever filed my Mooney to the top. I like to fly fast. 

-Robert

[RobertGary1]

13 minutes ago, gsxrpilot said:

Generally I would always fly with fuel in both tanks. But towards the end of a long trip, I believe 10 gallons in one tank is safer, more useable, etc, then 5 gal Left and 5 gal Right. The tank is less likely to suck air in a turn, I've got more margin for error of quantity calculation, etc. Bottom line is that if I'm down to my last 10 gallons, I'd like it to be all in one tank rather than some in one tank and some in the other.

Lake Aero reporter an off field landing due to a bad seal in the selector sucking air as a pilot let one tank get too low. I won't go below 2-3 in a tank. 

[M20F]

Generally it is full tanks or 10 gallons to go buy fuel which is 30 mins away.  When you are buying 55+ gallons a $1 a gallon adds up.  If it is borderline I will put in 5 gallons of expensive gas just to be safe. 

[MBDiagMan]

I guess I am still just a grass roots taildragger guy.  Even though my Cessna 140 has EXCELLENT wing root mechanical fuel gauges, I have used a stick in the tanks before almost every flight I have ever made in her.  I brought that same old fashioned mentality to the Mooney.  I made a fuel stick right away and if the tank is not full to the brim, I use the stick.  The fuel gauges in the Mooney are pretty bad, so the fuel stick is mandatory AFAIAC.

[Raptor05121]

This should be a percentage, not gallons.

Of course a 120 gallon Acclaim won't take off with 5-10 gallons, but my 48 gallon C model, that is quite normal for a 10 minute hop for cheaper fuel

[gsxrpilot]

12 minutes ago, MBDiagMan said:

I guess I am still just a grass roots taildragger guy.  Even though my Cessna 140 has EXCELLENT wing root mechanical fuel gauges, I have used a stick in the tanks before almost every flight I have ever made in her.  I brought that same old fashioned mentality to the Mooney.  I made a fuel stick right away and if the tank is not full to the brim, I use the stick.  The fuel gauges in the Mooney are pretty bad, so the fuel stick is mandatory AFAIAC.

A stick was the only fuel gauge I ever used with my C.