1 letter:
.

2 letters:
ac, dc, go

3 letters:
aim, bid, cut, get, jog, toe

4 letters:
airt, asea, away, back, beat, bend, face, fall, flip, flux, gear, gyro, hang, head, home, lead, left, lobe, look, loud, make, mold, need, pile, pull, rise, roll, rook, show, skew, slew, slue, sock, soft, tack, take, turn, urge, vane, veer, work

5 letters:
about, ahead, along, arrow, aside, axial, block, bound, caaba, clack, curve, dodge, drive, forte, front, grain, guide, heave, kaaba, north, piano, plumb, point, press, qibla, ratch, rhumb, right, route, shank, shape, sharp, shear, sheer, shift, shoot, slice, south, steer, swing, trend, twist, venus

6 letters:
around, ascent, aslant, aslope, astray, battue, castle, charge, crossa, depart, direct, divert, drogue, exhort, headed, loudly, mihrab, motive, oblong, onward, pulley, rachet, radial, retral, return, skewed, sloped, softly, swerve, switch, u-turn, upwind, vector, volume, wheels

7 letters:
abreast, adverse, analogy, antapex, bearing, bidding, blinker, command, counsel, counter, cowlick, deflect, descent, diverge, endways, endwise, extreme, fissile, forward, go away, guiding, heading, leeward, mislead, monsoon, oblique, one-way, onwards, pointer, ratchet, reverse, seaward, sharply, simplex, slanted, sloping, tension, transit, turning, uncanny, upbound, urge on

8 letters:
air sock, attitude, backhand, backward, cogwheel, continue, contrary, destined, diagonal, directed, dislodge, dorsally, downwind, enfilade, forehand, forrader, forwards, frontage, guidance, gunpoint, homeward, indicate, ion beam, lee tide, longways, longwise, loudness, maneuver, ministry, misguide, negative, overlook, penitent, rearward, redirect, regulate, reversal, seawards, shifting, slanting, swastika, tailwind, tendency, two-lane, undercut, upstream, upstroke, windsock, windward

9 letters:
alternate, anaclinal, ascending, ascension, backhanda, backwards, broadwise, chandelle, clockwise, coastward, collision, commutate, crosswise, determine, dictation, dimension, directing, directive, downbound, flip-flop, following, forehanda, four-lane, glissando, gyroscope, influence, intensity, inversion, isotropic, kick turn, laterally, loxodrome, manoeuver, manoeuvre, microsome, misdirect, monocline, northerly, northward, rachet up, reversion, shingling, side-slip, sidelight, slantways, slantwise, turnabout, turn away, turn down, ventrally, wind cone, wind gage, wind sock, wind vane, worm gear, zone fire

10 letters:
air sleeve, anastalsis, anemometer, anemometry, anteriorly, antidromic, antitrades, backhanded, cataclinal, channelise, channelize, commutator, conducting, counseling, deflective, divergence, divergency, downstream, downstroke, field line, followinga, forehanded, fortemente, fortissimo, gear wheel, goniometer, hakenkreuz, inoic beam, isotropous, lengthways, lengthwise, monoclinal, motivation, nephoscope, northwards, opposition, pelvic fin, perversion, pianissimo, projection, reflection, refraction, refractive, reposition, retrograde, rhumb line, supervised, supervisor, swing door, tail rotor, tangential, three-lane, thwartwise, transverse, turnaround, vertically, wavelength, wind gauge

11 letters:
alternating, anemometric, anisotropic, breadthways, breadthwise, carriageway, clack valve, coming back, counselling, desexualise, desexualize, directional, directivity, interchange, knife pleat, lead astray, look across, look out on, meaningless, random walk, reciprocate, searchlight, seismograph, trafficator, translation, transversal, turn around, turn signal, ventral fin, very loudly, very softly, weathervane, wind sleeve

12 letters:
body english, broken-field, catty-corner, continuation, countermarch, curved shape, dramatically, horizontally, in the north, in the south, labanotation, leeward tide, pectoral fin, polarisation, polarization, pulley-block, ratchet down, to the north, to the south, weather vane

13 letters:
anemometrical, anticlockwise, backhand shot, clapper valve, clinical test, compass north, counter-drill, forehand shot, into the wind, line of force, look out over, nonmeaningful, northeastward, northwestward, ocean current, point the way, radio compass, reorientation, reversibility, running light, southeastward, southwestward, state of flux, straight line, swinging door, with the wind

14 letters:
clinical trial, differentially, directionality, direct current, disorientation, dorsoventrally, longitudinally, magnetic north, one-way street, toward the sea, transformation, traveling wave, turn indicator, unidirectional

15 letters:
angle of attack, backhand stroke, contraclockwise, coriolis effect, forehand stroke, great attractor, magnetic needle, maxwell's demon, northeastwardly, northwestwardly, odd-leg caliper, prevailing wind, southeastwardly, southwestwardly

16 letters:
against the wind, change of course, counterclockwise, direction finder, pianissimo assai

17 letters:
anti-torque rotor, close to the wind, fore-and-aft sail, foucault pendulum, good continuation

18 letters:
evolutionary trend, magnetic induction, magnetic intensity, radiation pressure

19 letters:
alternating current, change of direction, doctrine of analogy, law of continuation, move back and forth, newton's second law, ratchet screwdriver, travel purposefully

20 letters:
management personnel, rotational nystagmus, second law of motion, terrestrial guidance

21 letters:
magnetic flux density

23 letters:
magnetic field strength

25 letters:
post-rotational nystagmus

26 letters:
spiral ratchet screwdriver

27 letters:
acoustic radiation pressure

29 letters:
newton's second law of motion

30 letters:
corpuscular-radiation pressure