DeRated Take Offs

[az_gila]

Originally Posted by fodrv7

..............

As others have said, with a piston engine the reverse is true, for there is excess fuel fed at take-off power to keep the EGTs down. (see pic below) Reducing below about 80% removes the excess fuel. So you want to be either at 100% power or back around 70%.

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Pete.

Pete,
.....are you interpreting the picture correctly?

The line drawn is for minimum fuel flow.. that is with the correct leaning applied as per the operators manual.

Since Lycoming does not recommend leaning above 75% power, isn't the "step" in the graph the effect of the greater leaning allowed for continuous operation?

I don't believe it is anything actually inherent in how the engine works, just how the little red knob is used per the directions....

gil in Tucson

[fodrv7]

Gil,
You may well be right.
I had interpreted the graph differently, as the title of the graph is;
FUEL FLOW VS. PERCENTAGE POWER;
and so thought that the kink in the graph was the effect of the Fuel Injection unit as power was reduced.
If the graph is indeed the LIMIT of MINIMUM fuel flow to which should lean, then Lycoming should have put that in the title.
ie. MINIMUM ACCEPTABLE FUEL FLOW VS. PERCENTAGE POWER

I debated whether to include the graph in my post and in hindsight I should have left it out.

Thanks for bring it to my attention.
Pete.

[gmcjetpilot]

Originally Posted by daberges

The problem - I take off full power (Sensinich Prop/TMX320). I get to patten alt too fast at Vy / Vx. I am still over the runway. If I climb at 100 kts and get better visibility - I am still at patten alt before the first turn. I am getting climbs over 1500 fpm with the wind.

Anything near and over 100 Kts - the ride can get too uncomfortable with the turbulence. The aircraft came in at 1060 with me at 245 and half fuel.

I have heard of RVs taking off at as little 75 % power. Uses longer runway but climbs slower.

Just like a light 747 would do a derated T/O and Climb. (This gives better fuel efficiency and less engine wear)

That's a good problem to have. You'll get use to it. Approaching 800 feet pull the power back and level off. Even if you have to fly up-wind for a bit before turning crosswind leg, fine. Getting to pattern altitude over the end of the runway is normal and good.

Flying around slow planes in the pattern is always a pain. If you need to extend down wind you may be flying down wind too fast. You may want to get partial flaps out and fly slower as soon as you get to pattern altitude with slow planes in the traffic pattern.

You will have to get use to a fast plane and slow traffic. A great exercise is slow flight practice. Away from airport practice slow flight, with & with out partial flaps. When in the pattern as soon as you level off you may need a drastic power reduction and possibly add partial flaps before exceeding Vfe to follow slow planes. I just don't do touch and goes with slow planes if I can avoid it, but landing you can't help mix it up.

Fly the plane don't let it fly you. My term for the black knob on the panel we call the throttle is "The Rate of Events Control".

I would not be afraid or shy about fast climbs. Getting to pattern altitude is golden and goodness, but you need to control speed. Altitude and speed are life. Get all the altitude you can with full power, level off than pull the power back.

100 kt climb at 1500 fpm is just fine.

I take off full power almost always. You can pull the power back a little at 500 feet. If its smooth than use higher speed climb outs if traffic permits.

You are right Jets do use reduced thrust take offs when weight is lighter and runway/obstacles dictate, but these are twins. They are planned to fly on one engine, but you are right it saves fuel and wear.

If breaking in your engine I would not do any T/G's. If you do have a new engine you should go fly. Once broken in you can practice all the T/G's you want.

When I was CFI'ing years ago I would have the student use partial power to simulate density altitude and high gross, but its not like a C152/172 has lots of excess power. However when pulling power back even more (on a long runway of course) was a real eye opener. A lot of new pilots first time flying a heavy hot high density situation is after getting their ticket, so I tried to get them to realize HIGH DENS ALT is real.