Apologies if this is outside the scope of the forum (please remove if so)
The Bae Strix has a rather different method VTOL and transitioning to forward flight that I can’t quite get my head around as it appears to not have tilting motors or wings and I cant see how its done purely with differential thrust…any thoughts? (specifically the initial take off where it goes from sat tail down to vertical, the rest of the flight profile makes sense but that part confuses me)
Edited your post to show the embedded YouTube player.
For future reference, you need only the YT URL, not the hyperlink.
So, just :
https://www.youtube.com/watch?v=g9DgqOuG3a8
…rather than …
[https://www.youtube.com/watch?v=g9DgqOuG3a8](https://www.youtube.com/watch?v=g9DgqOuG3a8).
Thankyou, I se you edited the title also…making it more descripitive
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It’s quite simple really, so simple that even the DJI FPV Drone does the same when flown in Normal or Sport Mode.
When taking off the from rotors produce the greater thrust until the propellors are parallel with the ground, then it takes off just like any auto levelling drone. In forward level flight the rear rotors produce greater thrust to keep the fuselage level.
With the high angle of attack when on the ground I expect the drone could function as STOL platform as well if there’s a reason for quick deployment and landing.
+1 what Nidge said 
It is such a simple idea It makes the tilt wings / tilt rotors look clumsy. Thanks for introducing it here, the problem is now I want one …
… with rockets. 
Or a Pitts Special with added jets …
I dont think its that simple. The rear wheels arent a fixed pivot point so even with weight on them and brakes on, the thrust angle at the start of rotation would see a great amount of forward thrust initially.
I can’t see that it would simply pivot without travelling forward.
Thanks DeanoG60
It’s relatively simple …
Just reverse the rear props or more likely rotate the rear blades to give a little reverse thrust. I’d go with variable blades as BAE have been working with theses since the early 30’s, variables also make a lot of sense in terms of flight and power management.
Nick I just came in to say I thought of a possible solution but you’ve already said it…reverse the rear motors whilst powering up the front untill vertical attitude is attained.
I doubt variable cyclic pitch (ala helicopter) is used as it just makes things so mechanically complicated when its not really needed with a quad motor aircraft
Not discounted variable pitch as in an aeroplane prop though perhaps you mean that? though I still think its unlikely due the complexity/efficiency gain ratio not being enough of a reward
Thanks for the input all
The props will already have variable pitch, just adding a few degrees of rotation to slightly negative on the rear props isn’t much of a job to engineer in. You also get the advantage of not having to brake the rear motors down before spinning them up again. Keeping the same rotation and spinning the props to a negative pitch maintains momentum, the negatice effect wouldn’t be huge as the props would be running very inefficiently in terms of air moving but in terms of power eaten on a launch cycle it works better.
Variable pitch is going to be useda as it can be used to improve efficiency across a wider range of operational conditions. Fixed pitch is only optimised for a tight range of conditions (air speed, air density, prop speed) and for this you want to run as close to optimal as you can to extend range or loitering.
Cyclic pitch wouldn’t be needed, though I could imagine using it to produce an insanely agile drone, as the longitudinal axis of force is a constant. I have RC helicopters with flybarless heads, the system is mechanically simple but electonically complex. If you take the cyclic out of the variable it’s just a proven electro-mechanical system.
Where did you see that Nick?
One of the aircraft I fly has a variable pitch prop so Im aware of their use arguement but don’t see much worthwhile gain in this application
(Don’t forget Electric motors have a very wide torque band and can produce useable power over a far wider rpm range than IC engines which somewhat reduces the advantages of variable pitch when using electric motors though of course any fixed pitch prop will always have maximum efficiency at one certain RPM)