Determining the maximum endurance speed

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10540

Leaning is never a way to true economy. Concentrating solely on engine management rather than trip management is looking at an isolated point rather than the whole picture.

In pure engine management overleaning will reduce the life of the engine and hence make a mockery of the bits of fuel saved.

Correct and conservative leaning for a given power setting is important but greater savings overall are made by trip management.

Trip management for me is selecting the best levels to fly at considering winds TAS etc.

Aircraft vary but the principals are the same. There is a whole lot more to look at than purely engine management.

Take a ferry in a jet. We are required not only to fly for range but to save the ferry company money.

That will mean firstly flying high, getting up high as quickly as possible as with jet engines the fuel flows drop considerably as the aircraft climbs into the high 30s.

Weight and climb rate to cruise ie how long you are at max power in the climb to get to your desired level.

Can you get to your desired level? step climbs, carrying less fuel on shorter trips etc. They all come into the equation.

Then flying a fuel flow and accepting the N1 that produces. Obviously the more you reduce the more the speed reduces until you get into a negative situation.

Then we bring in the winds. Tailwinds and we can reduce to maintain a groundspeed. Headwinds and its a compromise between higher thrust settings and reasonable fuel flows.

Remember we loose more flying a headwind on recipricol legs than you would gain with the tailwind.

Question is it better to fly lower levels with lower headwinds and higher fuel burns or accept higher headwinds with lower fuel burns?

Descent in a jet it is better to stay high for as long as possible and then to fly fuel flows in the descent.

While I appreciate that jets and pistons are very different animals the principals of fuel management being more important to trip management are clear and while not all the principals are relevant many are.

I know a Seneca five owner who has had to renew his engines early because of overleaning to save a few litres of fuel. There are far bigger savings by concentrating more on trip management especially regarding winds, weight, levels, climbing, descending, power and speed management etc.

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