During takeoff and landing, what is the temperature of flap linkages in passenger or fighter jet aircraft?

  • 4
    $\begingroup$ Unless a linkage was directly in an exhaust flow, it would be the same temperature as the ambient air, no? How would it be anything different? $\endgroup$
    – John K
    Dec 13 '20 at 15:38
  • $\begingroup$ During takeoff flap opens to provide lift.so is there any possibility of temperature rise due to high pressure during flap fully extended position? $\endgroup$ Dec 13 '20 at 17:21
  • 3
    $\begingroup$ No you need to be well past 200 kt for any kind of significant compressibility temperature rise, and that's only around leading edges. $\endgroup$
    – John K
    Dec 13 '20 at 18:13
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    $\begingroup$ Pooja, You might like to give some idea of what prompted the question. In case your question arose while trying to understand some related phenomenon it would be nice if you added something about that. You may like to read up on the terms TAT (Total air Temperature), OAT on ground, and SAT inflight, here. $\endgroup$
    – skipper44
    Dec 13 '20 at 20:01
  • $\begingroup$ Thanx John.Will u please tell me the temperature rise around leading edges. $\endgroup$ Dec 14 '20 at 5:12

Components like linkages on a wing flap system can be considered to be the local ambient temperature, subject to some lag if the plane is moving between large temperature changes, because of the time for the components to soak.

So a plane descending from 40000 ft after a cruise at that altitude may have components cold-soaked to ambient, say -40C, and if the airplane descends to 3000 ft to start an approach, where the temperature is +10C, by the time the airplane is at 3000 ft the components can be expected to be a bit cooler than ambient because of the lag time for the components to fully absorb the heat of the warmer lower temperatures. How much lag would depend on a lot of factors, like the amount of exposure to the freestream, and things like heat being drawn toward cold fuel just ahead of the component.

This was a significant problem in fact on the CRJ200 program, because the screw jack flap actuators were sensitive to extreme cold and like to jam, and a good cold soak at high altitude followed by a quick descent and extension at low altitude, where it was still really cold down low (winter), could leave them still cold enough to have the system fail while still at zero. There was a big AD related to it.


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