PPRuNe Forums - Should I take the longer runway

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As SLF, one reason I'm comforted to have humans upfront is that they could potentially recognize that seemingly minor issue are actually the first signs of something serious. As I result, I like the idea of a lower-thrust takeoff with a higher V1 giving more time for that recognition to occur. So I have no idea if a longer runway is safer, but if I knew you were taking one, I'd feel better.

It is interesting that the assumed reason for rejecting a take off generally appears to be an engine failure. In 11 thousand (Perf. A) flights or so I have rejected about half a dozen. Only one was a high speed reject, the rest were at a relatively low speed. But not one was due to an engine failure. I think this is quite typical for most pilots in so much that you rarely stop for an engine failure, it is normally something else.

So diving back in, in a very amateurish way, unless our performance calculations have a "Safety Quotient" against each performance calculation, you can never determine which is the safer. I believe it is far too easy assume that a greater performance margin equal a greater safety margin, but this is too simplistic because it only assumes an engine failure. There is more to it than that. So unless I'm given that information, I'll stick to my company's guidelines and operational preferences.

PM

The original post:

Quote:

So it is decided to use the longer runway. The only thing is that with the longer runway a derate and ATM thrust reduction is used for the takeoff along with a different flap setting.

Without including a bunch of variables such as the longer runway covers weather changes, payload adjustments, etc.......How much advantage have you gained by using the longer runway. Is the reduced thrust takeoff negating most or all of the advantage that the longer runway offers?

Because of the derate/Flex, the TORR/TODR on the longer runway will be longer than that off TOGA take off on the shorter runway but it will meet all regulatory requirements of take off. As GR stated using flex produces better performance than that of TOGA at that OAT because although the engine power is same the TAS at lower actual OAT is less due to higher air density. Since there is limit of 25% to 40% on Flex the advantage of using longer runway is not totally negated. Off course lower EGT results in reduced maintenance costs. That is the very purpose of flex take off. Flex take off uses more fuel than TOGA. All companies want Flex and lower thrust reduction altitudes for reducing fuel cost and only weather, wind shear is valid reason to use TOGA when Flex is possible.