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Old 2nd Aug 2007, 17:16
  #934 (permalink)  
Mad (Flt) Scientist
 
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I suspect those Boeing LDR data are OEM data, unapproved by the FAA, as with much wet/slippery data.

As grunf says, the regs prohibit taking credit for the decel effects of any device which is dependent upon engine operation. So no "certified" distance should include TRs.

25.125(f) If any device is used that depends on the operation of any engine, and if the landing distance would be noticeably increased when a landing is made with that engine inoperative, the landing distance must be determined with that engine inoperative unless the use of compensating means will result in a landing distance not more than that with each engine operating.
Though I will take a slight disagreement about the statement "wet runways, included!". Bizarre though it may seem, especially in light of this and other incidents, 25.125, even at the latest reg, makes ZERO reference to anything other than a dry runway. There are NO Part 25 requirements for landing performance on wet or slippery runways.
One could argue that 25.1301 and 1309(a) required the raw ability to stop on a wet runway (the brakes must "perform their intended function"), but that's a qualitative requirement, not quantitative. 25.735 is about design and redundancy, not brake performance really.

And Part 121 requires a VERY arbitrary 15% planning margin over the dry planned distances for wet - a margin which may bear little or no relationship to the actual degradation in stopping performance on a wet or slippery runway....
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