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I watched this video on YouTube:

The video shows some pretty impressive take-offs in serious crosswind. Honestly, they looked even scarier than crosswind landings.

It also made me wonder: In such conditions, when there is significant yaw due to the crosswind, and paired with the high engine setting, isn't there a significant risk for compressor stalls? Are there some formulas for calculating maximum crosswind particularly for takeoffs, or something like that, taking into consideration engine performance/response?

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    $\begingroup$ When the aircraft yaws like that, it is yawing into the wind, so the relative airflow into the engines will be more direct. That shouldn't cause a compressor stall. $\endgroup$ – Ron Beyer Oct 19 '16 at 13:43
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    $\begingroup$ @RonBeyer Looks like an answer... $\endgroup$ – KorvinStarmast Oct 19 '16 at 16:40
  • $\begingroup$ I can't help but watch that video and go "wheee" $\endgroup$ – Simon Oct 19 '16 at 18:03
  • $\begingroup$ The main issue with crosswinds is actually when it is sitting on the ground. As Ron mentioned, the crosswind component will be much higher then. $\endgroup$ – fooot Oct 19 '16 at 20:45
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The general FAA regulation on turbine engines on airliners is § 25.939

§ 25.939 Turbine engine operating characteristics.

(a) Turbine engine operating characteristics must be investigated in flight to determine that no adverse characteristics (such as stall, surge, or flameout) are present, to a hazardous degree, during normal and emergency operation within the range of operating limitations of the airplane and of the engine.

(b) [Reserved]

(c) The turbine engine air inlet system may not, as a result of air flow distortion during normal operation, cause vibration harmful to the engine.

The FAA has published Advisory Circular 25.939-1 which provides more detail as to how this regulation should be met. The takeoff phase is critical for safety, so the FAA requires testing to show that:

No adverse engine operating characteristics (mild, moderate, or severe) should exist after the power setting phase (normally completed by 60 to 80 knots) of the takeoff procedure through attainment of the enroute configuration and climb to 1,500 ft. above the airport.

The "adverse operating characteristics" are defined in more detail earlier in the AC. So to answer the question, no, it is required by law that jet engines have no issue with takeoffs in crosswinds. The faster an aircraft is moving, the less the crosswind airspeed component is. Once the aircraft is flying, aside from control inputs or changes in the atmosphere, the air stream comes from straight ahead.

The highest amount of relative crosswind will actually occur while the aircraft is sitting on the ground. Note that unlike the takeoff phase:

Taxiing: No adverse engine operating characteristics (mild, moderate, or severe) should exist during taxiing except for operation in crosswinds and tailwinds where mild adverse operating characteristics are acceptable.

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    $\begingroup$ You should probably preface this nice answer with a short, bolded, "no, for an aircraft that conforms with certification requirements." $\endgroup$ – KorvinStarmast Oct 20 '16 at 2:27
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Crosswind can decrease the "stall margin", but that does not necessarily increase the risk of a stall. If you look at a typical compressor map (e.g. https://en.wikipedia.org/wiki/Compressor_map), there is a line called the stall line or surge line. Operation above this line will result in a compressor stall. Normally, the compressor will be operated well below this line, so that the probability of stall is zero. Stall margin describes how far away the operating line is from the stall line. During a crosswind, the flow into the inlet is distorted, which may decrease the stall line (see for example Aircraft Propulsion Systems Technology and Design By Gordon C. Oates). This would decrease the available stall margin. However, the engine manufacturer will know how much the stall line drops for a given crosswind speed (e.g. by running test in an intentional crosswind condition), and will account for that in the engine design. Therefore, even though the stall margin is decreased, a sufficient amount of stall margin is still available, therefore the risk of stall is still essentially zero.

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    $\begingroup$ You are correct that I was not precise. What I was trying to avoid is the fact that "increased risk" can be an emotionally charged phrase with negative connotations and I try to avoid saying it when there is a chance it could be taken out of context. Although it is technically correct to say that the risk of stall increases when the stall margin drops, we are still talking about rare events. E.g. maybe it's the difference between 1 in a million and 3 in a million. Technically yes the probability is increased, but effectively it is very small. $\endgroup$ – Daniel K Dec 18 '16 at 22:18

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