Fuel calculations -taxi

[funvee]

When flight planning and doing W&B, is there a spot in the poh that has taxi fuel allowances to use?

I know that on the W&B app I use it suggested 2G but I have no idea how it came to that number.

Thanks,

Shawn

[DS1980]

Half gallon per cylinder for non turbo engines. One gallon per cylinder for turbo engines. This also includes run up. This is what Richard Collins used for decades and it seemed to work well.

[larryb]

I allow 5 gallons for start, taxi, takeoff, and climb to 10,000 feet. That means I calculate the full length flight at cruise and add 5 to get the total.

[David Mazer]

I use only 2 gal for startup, runup, and taxi.  Then I use a climb burn (23 gph for my 6 cylinder turbo charged 305 hp engine).  Then I use a cruise and descent burn rate.  My calculations on fltplan.com are never a whole gallon off.

[funvee]

Half gallon per cylinder for non turbo engines. One gallon per cylinder for turbo engines. This also includes run up. This is what Richard Collins used for decades and it seemed to work well.

I guess the 2 g that the app was suggesting is using this calc, I assume this is just .... startup, run up and taxi with nothing for fuel to climb.

That's very helpful thanks,

[funvee]

I allow 5 gallons for start, taxi, takeoff, and climb to 10,000 feet. That means I calculate the full length flight at cruise and add 5 to get the total.

I like that this way includes the climb fuel... I'm going to try it using this one today to see how the numbers work out.

Thanks!

[N601RX]

With an injected motor well leaned 2gph is what I see durring taxi. If full rich it is around 3.5.

[romair]

I lean to about 1.7gph at around 1000 rpms right after start, then during taxi I advance the throttle as needed for taxi. I usually don't need to significantly change the mixture during taxi until I get to do my ground run.

[xftrplt]

I agree, 2 g/h taxi.  Runup?  Generally don't do them.

[DAVIDWH]

Hmmn, did you say no runup? 

 

Years ago on takeoff in a Cessna 310 about 1/2 way down the runway, aircraft started a gradual then a more solid pull to the right.

 

MP on the money, engine screaming power, just a little more left rudder needed, then as nearing the grass, pulled power,

 

skidded brakes, blew a tire, and finally screeched to a stop, totally confused by what had just happened. (Trust me, things can happen fast at full power)

 

After a rather lengthy trip to tie down, called A&P and waited. Ed jumped in, started engines, did A&P magic, jumped out and

announced the prop govenor on the starboard engine was defective.

 

To this day, haven't missed another runup.

[pinerunner]

With an injected motor well leaned 2gph is what I see durring taxi. If full rich it is around 3.5.

I see this too. Approxiamately 2 GPH during taxi and no one taxi's for an hour (do they?). Runup is pretty quick so not that much more burnt. I did some take-offs and landings including climbing to about 3000 ft (short local flight), starting with a full tank and refilling at the end. I came to the conclusion that I used approximately 2 gallons for each takeoff and landing along with a short climb. Now I have fuel flow and know I'm burning about 18 GPH full rich during take-off so 6 min would be only 1.8 gallons without pulling back the power or leaning at all. that predicts pretty much the same ballpark number of 2 gallons and taxi shouldn't use much at small airports.

[funvee]

With an injected motor well leaned 2gph is what I see durring taxi. If full rich it is around 3.5.

Per hour?? Or did you mean 2 gallon total for taxi/run up? I used the 2g number today and it all seemed to jive well.

[carusoam]

My flat 6 starts and taxis at 2.2 to 2.4 gph @1,000rpm ( measured in an io-550(N))

To include take-off you would need to add 15 seconds or so of 28gph. I'll have to collect more data to improve accuracy to this statement.

If you fly a P51, it may use more....

If you fly an M20C, a couple of pumps on the throttle prior to start is probably a tea spoonful and then similar to the flat six above.

In real world flying, I would expect these values to be within the error of the more important fuel burns during climb and cruise followed by descent and then finally taxiing.

Best regards,

-a-

[pinerunner]

Per hour?? Or did you mean 2 gallon total for taxi/run up? I used the 2g number today and it all seemed to jive well.

2 Gallons per hour for taxiing with leaning for taxi of course. I think you'll find if you fill up,then do a taxi/run up, then go right back to the pump without flying, it'll take a lot less than 2 gallons to fill it back up.

[201er]

When flight planning and doing W&B, is there a spot in the poh that has taxi fuel allowances to use?

Now that depends if you gotta hold for IFR clearance or just get up and go! But honestly, either way it doesn't matter because the amount is so negligible and I'd never be cutting my fuel at destination so close that I'd have to count it. How many minutes you spend at full power play a far greater role than what you spend taxiing. Worst case scenario is maybe like 30 minutes total for a flight which isn't even 1 full gallon.

[Awful_Charlie]

I use 2 gallons for the first start/warm-up/taxi/run-up of the day, and then 1 gallon for subsequent legs.  Rarely happens, but if it's more than one leg in the day, but seperated by several hours, then can consider 2 gallons for the subseqnt run up, but if 1 gallon is making the difference between a 'go' and 'no go' then it's time to get more fuel anyway.

[xftrplt]

Hmmn, did you say no runup?

After a rather lengthy trip to tie down, called A&P and waited. Ed jumped in, started engines, did A&P magic, jumped out and

announced the prop govenor on the starboard engine was defective.

I suspected some feathers would get ruffled by that comment.

However, a twin is a horse of a different color. In a non-feathering single, the prop fails to flat pitch, in twins, I believe, it's generally the other way.

At my home drone, a 5k foot strip at 3k MSL, advancing the power on the turbo slowly, things just don't happen that fast. I also have the mags monitored by an electronic tach. Having flown many high-performance jets--fighters, turbo-props, and air transports--I know that events can happen quickly. Essentially, their "run up" is on the roll. So is mine, generally.

I'm not presuming to tell others how to fly, only stating my preference in my aircraft.

Blue skies.

[fantom]

Cute trap, Dave....just to see if people were paying attention, I assume. Might have mentioned you were referring to a twin turbo.

 

 

I suspected some feathers would get ruffled by that comment.

 

[Shadrach]

I don't do a traditional run-up either... I check continuity on the mags and prop while I'm taxing out or sitting at the hold short.

 

Many many years ago, I had a coil in the left mag that would only short above 2200 RPM. Normal Ground run-up showed no anomalies, but I noticed abnormally high EGTs in climb. Once established in cruise, I tried to lean to peak EGT and got a something close to or higher than 1700df. Did a mag check in flight and sure enough left mag was dead. Landed the plane and was only able to duplicate it by running up to full power with the brakes locked. mag would go off line at about 2250. I see little utility in running the plane up to 1750 or whatever is recommended for a run-up. I taxi with the engine very lean and get a nice drop on one mag at 1000RPM. Same with the Prop Gov. 1000 RPM, pull the prop, Push back in as the RPMs drop. That tells me just as much as I'd get from bead blasting my prop with pebbles at 1750rpm while sitting stationary.  I do my Mag checks when they're really working hard...at WOT in cruise.