I remember the SP I took training had a clear limit of, I think it was 17 knots, but the old one I am flying now has this legendary demonstrated sentence instead. Same is true for 152s - the "ordinary" ones have a limit, but the F Aerobats have no sentence limiting crosswind. So, it depends on the correct POH wether it is legal to land and within stated operational limits or not - in the end.
I believe this to be not correct;
Unless the crosswind "limitation" is specified in Section 2, limitations (or the earlier format equivalent), there is no limitation. There is a stated demonstrated capability, that is not legally limiting. The pilot may attempt a landing in as great a crosswind as they choose, and be legal.
The prevailing design requirement reads:
Sec. 23.233
Directional stability and control.
(a) There may be no uncontrollable ground or water looping tendency in 90 degree cross winds, up to a wind velocity of 0.2 VS0, at any speed at which the airplane may be expected to be operated on the ground or water.
(b) A landplane must be satisfactorily controllable, without exceptional piloting skill or alertness, in power-off landings at normal landing speed, without using brakes or engine power to maintain a straight path.
(c) The airplane must have adequate directional control during taxiing.
As can be seen, the strength of the crosswind which must be demonstrated is based upon the stall speed. But also note that this "demonstrated" value is based piloting without exceptional skill or alertness.
It is also noteworthy that the design requirements for limitations do not mention crosswinds at all - there is no requirement to state a crosswind "limitation".
Sec. 23.1583
Operating limitations.
(a) Airspeed limitations. Information necessary for the marking of the airspeed limits on the
indicator as required in Sec. 23.1545 must be furnished, including VA and VLO. The significance of each limitation and of the color coding must be explained.
(b) Powerplant limitations. Information must be furnished to explain the powerplant limitations and to allow marking the instruments under Sec. 23.1549.
(c) Weight. The airplane flight manual must include--
(1) The maximum weight;
(2) The empty weight and center of gravity location;
(3) The useful load; and
(4) The composition of the useful load, including the total weight of fuel and oil with full tanks.
(d) Load distribution. The established center of gravity limits must be furnished. If the available loading space is adequately placarded or arranged so that no reasonable distribution of the useful load listed in paragraph (c) of this section will result in a center of gravity outside of the stated limits, the Airplane Flight Manual (where required) need not include any information other than the statement of center of gravity limits. In other cases, the manual must include enough information to indicate loading combinations that will keep the center of gravity within established limits.
(e) Maneuvers . The following authorized maneuvers, appropriate airspeed limitations, and unauthorized maneuvers must be furnished as prescribed in this section.
(1) Normal category airplanes. For normal category airplanes, acrobatic maneuvers, including spins, are unauthorized. If the airplane has been shown to be "characteristically incapable of spinning" under Sec. 23.221(d), a statement to this effect must be entered. Other normal category airplanes must be placarded against spins.
(2) Utility category airplanes. For utility category airplanes, authorized maneuvers shown in the type flight tests must be furnished, together with recommended entry speeds. No other maneuver is authorized. If the airplane has been shown to be "characteristically incapable of spinning" under Sec. 23.221(d), a statement to this effect must be entered.
(3) Acrobatic category airplanes. For acrobatic category airplanes, the approved flight maneuvers shown in the type flight tests must be included, together with recommended entry speeds. A placard listing the use of the controls required to recover from spinning maneuvers must be in the cockpit.
(f) Flight load factor. The positive limit load factors, in g's, must be furnished.
(g) Flight crew. If a flight crew of more than one is required for safety, the number and functions of the minimum flight crew must be furnished.
(h) Kinds of operation. The kinds of operation (such as VFR, IFR, day, or night) in which the airplane may or may not be used, and the meteorological conditions under which it may or may not be used, must be furnished. Any installed equipment that affects any operating limitation must be listed and identified as to operational function.
(i) If the unusable fuel supply in any tank exceeds five percent of the tank capacity, or one gallon, whichever is greater, information, showing that the fuel remaining in the tank when the quantity indicator reads "zero" cannot be safely used in flight, must be furnished. This information must be in the Airplane Flight Manual (if provided) and on a placard.
The owner of the aircraft may have more restrictive rules, and that is their prerogative as the owner, but the pilot is
legal to attempt a landing at any crosswind value (not exceeding a limitation), and the aircraft would be insured to do that, as long as the pilot was duly authorized to fly it.
Yes, mechanical turbulence can greatly affect the capability of an aircraft and pilot, and acting as a crosswind, even more.
I have taken off my 150 in 37G43 knots at a 45 degree angle for an emergency flight. I did not attempt to land back on the same runway, I selected a different aerodrome, with the runway right into the wind.