fuel burn da40

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Re: fuel burn da40

by Colin » Fri Feb 23, 2018 7:15 pm

If you happen to make it into a warbird like a Mustang or Bearcat, do not go full throttle for the go around. You don't have the rudder authority yet to handle it (and the wheels are not on the ground, the way they are when you takeoff with full throttle).

Re: fuel burn da40

by gordsh » Fri Feb 23, 2018 4:45 pm

As I am still a student pilot I do a lot of circuits. When doing circuits my instructor instructed me to (1) leave the *fuel pump on (2) leave mixture full rich (3) leave prop full forward. The only time I every touch the mixture and prop is on x-country. *Once outside the circuit fuel pump is off as normal but in circuit its on.

Re: fuel burn da40

by CFIDave » Fri Feb 23, 2018 2:23 pm

I was not describing how to teach at a high altitude airport like in Colorado, where of course you don't use full mixture. And I agree that students must be taught to adjust the mixture after leaving the traffic pattern.
Rich wrote:The exception is a go-around, of course.
You just described why it's essential that we teach students to move the red knob full forward (mixture to full rich), and the prop blue knob to full forward (max RPM) when throttling back abeam the numbers to begin descent in the pattern. The aircraft always needs to be configured for a potential go-around during landing, which requires immediate availability of full rich mixture and max RPM; the student should be able to simply put in full throttle to obtain maximum go-around horsepower. (A side benefit is that the engine is also properly configured for a touch-and-go landing, often useful when practicing with an instructor.)

Re: fuel burn da40

by Rich » Fri Feb 23, 2018 1:57 pm

The business of leaving full rich, in my experience, leads to pilots who have learned that using the mixture control is dangerous. When I was instructing I often ran into low-time pilots who were taught to never touch the mixture control. And where I did most of the instructing way back when, full rich was not appropriate for takeoff, especially in the summer months. AND using full rich mixture in the low-power phase more than necessary is more likely to treat you to lead buildup on the plugs.

The deal is you'll reduce power on downwind anyway. Just pull the mixture back 1/3 or so. I'm no longer in training, per se, but it is my practice to not enrich for full-stop landing at all. It stays where it was all the way to shutdown. The exception is a go-around, of course.

Re: fuel burn da40

by CFIDave » Fri Feb 23, 2018 1:37 pm

During flight training, teaching students to fly the traffic patterns is all about building muscle memory to learn *standard* actions and flows, all of which must take place in less than 5 minutes/circuit. IMHO, dropping the RPM even further or leaning the mixture on downwind just to save a tiny bit of fuel would only complicate that process. Leave the mixture full rich, bring RPM back to 2400, and upon reaching pattern altitude set manifold pressure to 19-20 inches to hold altitude on downwind.

Re: fuel burn da40

by Sandy » Fri Feb 23, 2018 9:41 am

Fuel flow depends on the horsepower (Hp) being generated, and Hp is directly related to engine RPM. As there is no reason to "speed" on your downwind leg, use the lowest RPM that you're comfortable with, and, certainly, no more than needed to maintain pattern altitude at a speed lower than your flap extension speed. Leaning on your downwind leg won't hurt, either.

Sandy

Re: fuel burn da40

by Rick » Thu Feb 22, 2018 2:57 pm

+1 on Dave's comment. Even if you ignore the initial purchase and installation cost, additional labor for the annual ICA maintenance would eat up any fuel savings. But in my opinion the performance boost is worth it. I've owned 2 DA40's, one with and one without PF, and the difference is very noticeable.

Re: fuel burn da40

by CFIDave » Thu Feb 22, 2018 2:09 pm

Install it for the increased performance, not to save money. I doubt it would ever pay for itself in fuel savings.

Re: fuel burn da40

by Ben2k99 » Thu Feb 22, 2018 1:55 am

Thanks guys. One more question: do you think installing a powerflow exhaust on an older DA40 would be worth the fuel savings alone?

Re: fuel burn da40

by CFIDave » Thu Feb 22, 2018 12:32 am

Assume 8-9 gph in a flight training environment as you described.

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