This is a very simple pattern, easily adjustable to fit and looks good with variegated yarn.
Yarn: I have used slightly over 1 ball of Gedifra Fashion Trend Color in colour 4567 (roughly about 100yards). This is very inconvenient unless you already have some of that yarn as left-overs (I had, so going over 1 ball made no difference). Any Sport weight yarn suitable for US 6-8 (4.00-5.00mm) will work.
Gauge: 15st x 20rs (10cm x 10cm/ 4inch x 4inch)
Needles: 4-5mm (US 6-8) circulars. I knit using magic loop, but you can chose to work with DPN or any length of circulars.
Size: 56cm (standard) adjust by adding removing pattern repeats
Pattern: [3K, 3P]*
Also you need crochet hook (same size as your needles) and extra yarn for cast on (try to use same type as your hat yarn).
With crochet hook cast on 84sts (28 pattern repeats). Change to needles and your hat yarn: [K3, P3] x 14. Carefully enclose the ring (take care not to twist). Now continue knitting in your pattern for 12cm (here 24rows).
Note: Knit 3 rows keeping the pattern after each decrease row!
Start decreasing in the P3 regions of the pattern only. P2tog first two sts in every following purl region (i.e. K3, P2tog, P1, K3, P3). You now have 77sts.
Repeat decreases with the P3 regions you have not decreased last time. You will now have 70sts left and pattern will be [K3, P2] x 14.
Repeat decreases as above until you have [K3, P1] x 14 pattern and 56sts.
Decrease as above but now with SKPO (sl1, k1, psso) instead of P2tog; first by decreasing P1, then K3. Continue until you will have 14K sts left. SKPO every second sts in one row, so you have only 7sts left. Cut yarn and with either crochet hook or needle close and secure those sts. You now have main body of the hat.
To make the helmet, remove waste cast on and put a needle through all stitches, you will now work in opposite direction from previous knitting!
Using markers, select 33 front sts (starting and finishing with P3); this will be your forehead region.
Row1 (RS): Join the yarn just in front of your first marker; P1, P2tog, cast off front 27 sts, P2tog, P1, finish the row following the pattern. You will now knit only the ear flops and the back having both right and wrong sides.
Row 2 (WS): SKPO, work the pattern until last 2 sts, K2tog
Row 3: SKPO, work the pattern until last 2 sts, K2tog.
You now have 15 sts of first ear flop (K3, P3, K3, P3, K3), 21sts of the back and 15sts of second ear flop (K3, P3, K3, P3, K3).
Knit following pattern for 7 more rows and close the back 21sts leaving only ear flop regions to be worked separately. You might wish to make the back region longer, mine is 5cm longer.
Ear flops are knitted using the same decreases method as in the main body of the hat. Keep decreasing until you have only 3 sts remaining, K3tog and secure the end.
That’s it! You have your own helmet hat! Mine took under 2hrs from initial measurements to the end result ;)