pilotbear - just gently, I'm afraid you're misinformed, and
gpn01 - you're not getting his/her point. What you're talking of is the downwind turn myth. It's the subject of many vitriolic discussions (just use search). Smarter people than I can prove it is not so mathematically - it's not intuitive (and I had to be convinced)
Might I quietly suggest that in the interests of topic drift we leave the downwind turn debate out of this thread? Perhaps a different thread, or have a read of previous wars on the subject!
Regarding the turnback - I think most would be somewhat suprised by:
1) how many knots you'll loose pitching from a normal climb angle even if you identify (and accept) the engine failure immediately
2) how much altitude you'll loose in making a 180 turn.
As someone else said, go high, go play. Figure out the numbers for your aeroplane - pulling the throttle to idle should be sufficient for a ballpark figure. But make sure you do verify airspeed well above stall before you start the turn.
Obviously the viable turnback alt will depend hugely on your particular aeroplane - on the right day you can make a complete circuit and land in the same direction as takeoff from 300 ft in a glider, to the other extreme some a/c wouldn't make it from 1500ft overhead - it all depends.
Kyprianos Biris - I would suggest that if you need 12-1300ft from abeam the numbers you could make your circuit a bit closer (depending on local traffic regs). General good practise would be to fly a circuit such that you can get to a runway from any point in the circuit.
Going back to the gliders (I fly both), there's a demo they do - spin off a (simulated) winch launch failure:
Pitch for a typical climb angle with speed, as the airspeed drops to winch launch speed, you declare the failure, and commence your pitch down. On reaching a 'normal' glinding attitude, you commence a turn. All of a sudden the world is full of rapidly revolving fields.
Why? Because the wing continues to fly throug the pushover (typically around 0G - fairly aggressive) because it is unloaded. As you level it gets re-loaded and instantly transitions to a mushing stall state, without the usual paraphenalia of progressing towards the stall. Next control you move tips the whole thing into a spin.
Indications are a low airspeed, and an abnormaly rearward stick position for the gliding attitude.
Apologies for the essay
