setting engine optima for take off

[Zacke]

Interesting how the guy in the following video is setting his engine for optimum take off performance (starting 15:25): https://www.youtube.com/watch?v=ENJdG41NxEo

I always wondered about the additional scale on the fuel flow gauge but never performed that pre T/O procedures. Seems to be quite logic and gives some safety concerning t/o performance and maybe preserves rpm from jumping over the red mark.

Do you perform that before before t/o? Any general/technical comments on that?

Thanks in advance,
Zacke

[AKar]

As a general technical advice, I'd say: don't!

For regular sea-level takeoff, you'd want all three levers full forward, always. That's how the engine is designed to be operated, and also how it should be adjusted to perform correctly.

It should be noted and fully understood that at rated power, the full-rich mixture is very much on the rich side. Opening of the throttle fully introduces additional enrichment of the mixture. Retarding either the throttle or the mixture lever from the full-forward positions deprives the engine from the fuel it needs.

The specified fuel flow for O-540-A at sea level rated power is approximately 23.7 USG/h, something you'd not want to be under of. I am not quite sure on what the given figures in the fuel flow gauge in this installation are based on. Note that leaning from the specified fuel flow means that you exceed the rated power while providing the engine with less cooling.

In what comes to the RPM, there are no reasons whatsoever to back off from the redline. The engine is designed and rated to operate at 2575 RPM. I don't know about the Comanche, but many RL installations don't reach the rated RPM at standstill but require some forward speed to do so. Regardless of when the propeller starts governing, it should be adjusted to the proper redline setting, and must not overspeed except transiently with very small exceedance (this is actually specified: less than 10 % for less than 3 seconds is allowed under the category of "momentary overspeed"). If the engine, for any reason, sustains RPM above the redline, it is not fit for flight and maintenance action should immediately take place.

Taking off from high-elevation airfield is, of course, a subject of its own.

-Esa

[Zacke]

Thx again!

[AKar]

Just one more thing.

I'd avoid full-power, or any very high power static run-ups unless really necessary. These are hard on the engine due to lack of proper cooling from the airflow, and require a mindset prepared for several things that can go wrong - not to be found in checklists! Setting up the levers for "optimum takeoff" should not make up a necessary case, or your margins are way too pushed already.

-Esa

[DHenriques_]

Just one more thing.

I'd avoid full-power, or any very high power static run-ups unless really necessary. These are hard on the engine due to lack of proper cooling from the airflow, and require a mindset prepared for several things that can go wrong - not to be found in checklists! Setting up the levers for "optimum takeoff" should not make up a necessary case, or your margins are way too pushed already.

-Esa

I never did full power run ups unless it was a maintenance check and the tail was tied down. A Mustang will actually jump the chocks over 40 inches.
Best full power check is immediately after takeoff power is applied. All good pilots develop an "instant scan" capability that checks the appropriate engine gauges and indicators as power is applied for takeoff.
Dudley Henriques

[AKar]

Just one more thing.

I'd avoid full-power, or any very high power static run-ups unless really necessary. These are hard on the engine due to lack of proper cooling from the airflow, and require a mindset prepared for several things that can go wrong - not to be found in checklists! Setting up the levers for "optimum takeoff" should not make up a necessary case, or your margins are way too pushed already.

-Esa

I never did full power run ups unless it was a maintenance check and the tail was tied down. A Mustang will actually jump the chocks over 40 inches.
Best full power check is immediately after takeoff power is applied. All good pilots develop an "instant scan" capability that checks the appropriate engine gauges and indicators as power is applied for takeoff.
Dudley Henriques

Yeah, indeed even many humble Cessnas with higher-end engines will not be held still by many, if not most kind of chocks. And even if restrained, if anything goes wrong (a loss of restraint, skidding wheel on one side, loose objects flying around, a leak of flammable liquid develops...the list goes on!), it takes extraordinary presence of mind to catch the developing situation immediately if not mentally prepared. Even in controlled maintenance run-up situations.

-Esa