# XFY-1 Vertical take-off mechanics

Hi I saw this video the other day of an XFY-1 doing a vertical take-off and landing and moving left to right while hovering.

See the video Here.

After watching this I had a few questions on how this is accomplished.

1. How does the plane go from vertical to horizontal and from horizontal to vertical flight? Is this done by moving the elevators to their respective extremes.

2. How can the plane move left to right forward to back while in vertical mode? Is this done by some sort of helicopter rotor type of contruction in the props?

I am not sure if this is the right place to ask, neither am I an expert when it comes to planes or the engineering behind them (I just know the basics).

Would love to know how this works or resources that explain this, could not really find any myself :)

The plane takes off vertically, with the prop wash blowing over conventional control surfaces. To tilt forwards the pilot pushes the stick forward in the usual way to "lower" the elevators and tip the nose "down". As the plane tips progressively over, it progressively gains flying speed and lift transfers to the delta wings. At the same time, the elevators are brought back to the level for conventional flight. Landing is the same thing in reverse, with the elevators being raised.

Manoeuvring in vertical mode is again just the same, but only a small control movement is needed for a gentle tip in the right direction: elevators in one axis, rudders in the other. The elevators also act as ailerons, which allow the pilot to gently spin the plane round even when vertical.

• Transition must have been very difficult, and landing with a stiff wind short of impossible. No wonder only one prototype was ever flown... – xxavier Feb 14 '20 at 20:53
• Yes. The pilot's seat was on gimbals and swung forwards by 45 deg in vertical mode. But even so, flying it was so difficult that its test programme was abandoned part way through. – Guy Inchbald Feb 15 '20 at 10:46

The control surfaces are in the prop-wash, and so are effective even when the aircraft is standing still. To manoeuvre the aircraft all you do is tilt the fuselage, which tilts the prop and thus tilts the lift/thrust just like a helicopter does.

• just to make sure I understand correctly. So the plane is able to do all this just by using its elevators and rudder to tilt the fuselage in the desired direction. Right? – FutureCake Feb 14 '20 at 13:17
• I'm pretty sure the answer is "yes, right". I bet there was a second rudder on the down-projecting (ventral) vertical fin as well though you'd want to double-check that. And technically the elevators should be called "elevons" because they also have an aileron function. If there really were two rudders, then the rudders could also have been mixed for roll control and thus be "ruddervons" but my guess is that they didn't bother with the complexity that would entail. – quiet flyer Feb 14 '20 at 15:33
• I suppose you are aware that a similar plane developed at the same time had, rather than delta wings, straight wings located near the CG plus a big cruciform tail. Same basic principle. With the ailerons possibly not being in the propwash, it would be interesting to know exactly how roll control was accomplished while hovering-- elevons and/or ruddervons, despite the moment-arm for roll torque being much shorter than with the XFY-1? Could be grounds for another question... – quiet flyer Feb 14 '20 at 15:35
• It would be more correct to just call all the control surfaces "attitude control vanes" when in hover mode since they all perform the same function. Really no different from having control vanes in a rocket exhaust in a rocket that was able to hover. – John K Feb 14 '20 at 18:23
• @FutureCake Go look on YouTube for videos of R/C pattern (especially indoor pattern) aerobatic aircraft. Many of these can hover, maneuver, and transition into and out of hover without even a contra propeller system to cancel engine torque. They do it the same way -- using the conventional surfaces in prop wash to both cancel torque and vector thrust for low speed translation; they also have >>1 TWR so they can accelerate upward out of the hover to transition a bit more positively than the XFY-1 did. – Zeiss Ikon Feb 14 '20 at 20:30