Fixed wing aircraft control via engine gimble

[mheslep]

It has been some time since I sat through basic aircraft dynamics, so I hope to check some conclusions about the topic. Clearly rockets and missiles have maintained stable flight via gimble of the engines. My understanding has been that designing, say, jet aircraft in this way (i.e. forgoing control of flight surfaces) has not been feasible because doing so at cruise speed sharply change the angle-of-attack and stall the compressor air flow (among other difficulties).

Now however the possibility of non-air breathing, in the atmosphere propulsion looms. In such a future, can the ubiquitous big tail and elevators and their drag be discarded, replaced by gimbled propulsion? It seems to me that practically the answer is still no, because a fixed wing aircraft with no tail would have the center of pressure (CP) well forward of the center-mass, unlike a wingless rocket, and then in the event of propulsion failure, even for a moment, such an aircraft would become violently unstable.

 

[Astronuc]

Gimbled propulsion (thrust vectoring) on an aircraft is going to be more complicated than a fixed engine.

Harriers and F-22 Raptor use thrust vectoring, but I think it depends on the mission of the aircraft. The V-22 Osprey is a different application with fixed engines/props on rotating wings. Certainly, unbalanced thrust, or failure of one engine would be a significant concern and consideration.

Here is a discussion on the topic - http://en.wikipedia.org/wiki/Thrust_vectoring

For commercial aircraft, I suspect it depends on how much lift will come from the airflow across the wings versus vectoring the thrust from the engine.

 

[mheslep]

Thanks for the comment Astronuc.

Yes, as the Wiki page indicates, aside from the Osprey, fixed wind aircraft that use some form of thrust vectoring do so by deflecting the thrust, not via gimbled engines. The Osprey does rotate its engines, but only in one plane. Unlike rockets, all these aircraft rely on move-able aerodynamic surfaces for basic control, though apparently some obtain extreme maneuverability (i.e. high angles of attack) by adding thrust vectoring.

Like rockets, any aircraft that relied on gimbled propusion for aero-control I suspect must have its propulsion in one location, to the aft.

 

[mheslep]

Phys.org also has a re-print mention of the idea of gimballed propulsion for aircraft, in a what-if piece for 2050 aircraft.

Once electric aircraft are established, the next step will be to integrate a gimballed propulsion system, one that can provide thrust in any direction. This will remove the need for the elevators, rudders, and tailplane control surfaces that current designs require, but which add significant mass and drag.