# Tag Info

50

Interesting question. Purely empirically, it is the lift-to-drag ratio you are looking for. If you take this value as given for any particular aircraft, you have a direct answer for how much more effective wings are. It is the ratio of the lift to the total drag. The engine only needs to overcome the drag. With L/D equal to unity you would need the same ...

29

With regard to energy expenditure and power, for a given amount of force that is to be produced by accelerating an air mass, more power is required when you accelerate a small air mass in each period of time than when you accelerate a large air mass. This is because the force is proportional to the change in momentum of the air mass, whereas the power is ...

27

In a traditional aircraft the majority of the power from the engine is used to keep the aircraft moving forward at a certain speed. Very little of that power is actually needed to create lift. Consider a simple paper airplane. It flies for a long time with no engine at all, until the drag on it causes it to slow down and if loses lift and descends to the ...

17

This is a case of divergent design, and you can't know the answer without asking why current aircraft are designed they way they are. Following the work of Col. John Boyd in the 1960's in developing the 'Energy-Maneuverability Theory', the U.S. and allies primarily designed combat aircraft and tactics around the idea that an aircraft's specific energy state ...

16

For the F135 engine in this photo, thrust in hover is only about one per cent less than maximum thrust, if Pratt & Whitney's data sheet is to be believed. Maximum Thrust Class 41,000 lbs ... Hover Thrust 40,650 lbs The Hawker Harrier's maximum thrust was about 20,280 pounds. An approximation of its maximum vertical thrust at low airspeed is given by ...

14

Historically, flaps and control surfaces were moved manually: The pilot would move a stick, a control column or pedals, and pulleys or pushrods would transfer this force to the control surfaces. To do this with engines was physically impossible. With the introduction of hydraulics, large enough forces for tilting engines were available for the first time. ...

14

Part 1 - TVC Perception The US also ran several programs with TVC: F-15 STOL/MTD and ACTIVE. F-16 VISTA / MATV. AVEN: F-18 HARV (High Alpha Research Vehicle). Overview pdf. F-22 (almost 200 produced) X-31. X-36. (Yaw only.) X-44 MANTA (proposed F-22 variant) (All photos from their respective wiki pages except ...

13

The direction of rotation of the propeller introduces an asymmetry which designers try to mitigate by adding more asymmetries. Specifically, a right-turning tractor propeller (clockwise from the pilot's viewpoint) will swirl the propeller wake in the same direction which adds a negative sideslip angle on the vertical tail (which sticks up into the upper half ...

13

Could you create an aircraft using an jet engine/propeller/ducted fan on a gimbal? Sure you 'could'; it is feasible by the laws of physics. But just because you can does not mean that you should. Setting up multiple points of lift on a manned aircraft seems like a good idea with a lot of advantages but is a Pandora's Box of problems, the not the least of ...

12

Yes, on airships. The Zeppelin NT can rotate its two forward and one rear propellers to create lift instead of thrust, a capability of particular value when the airship descends in an atmosphere with a strong temperature gradient. From this page about the Zeppelin NT: The two forward propellors swivel to 120° and the aft one to 90°, and a fixed aft ...

10

Maybe wings never mattered... Altitude: The answer depends a bit on the design of the craft in terms of control surfaces/wings. Atmospheric reentry begins at the Karman line at an altitude of 100 km (62.14 mi / ~ 54 nautical mi) (327,360 feet) above the surface. Which is generally when air resistance starts to matter but that does not mean control surfaces ...

10

The standard equation applies to any coordinated level turn (so that the G felt is "straight down" to an occupant of the aircraft, in an aircraft frame of reference). Matters not how it's all achieved - flaps, high-lift devices, helo rotor, thrust vectoring, whatever... a coordinated level turn at "this" bank will take "this" ...

9

The F-35 has what is called the Rolls-Royce LiftSystem. This Contains one lift fan in the middle of the aircraft, and a rotating jet exhaust to provide vertical thrust, and two rotating nozzles to provide stability. The pilot pushes a button, and doors on the aircraft open for the lift fan, while the exhaust nozzle rotates downward. The pilot controls the ...

9

No, it cannot, at least there is no reason for it to do so... A) The stick while in "hover mode" does not control the pitch/roll of the aircraft, but the forward/lateral position of the aircraft. This means that the aircraft can only shoot forward in a level attitude, it can't pitch up/down to hit a target. B) When in "hover" mode, the landing gear are ...

8

With thrust vectoring you no longer turn (as in: the wing creates the force that accelerates you in the desired direction) but you do post-stall maneuvering. Next, you need to distinguish between highest instantaneous turn rate (trading altitude for higher rate) and continuous turn rate (which is limited by the available thrust in most cases). Turn rate ...

7

As previously seen in a comment section, there are two main schools of thought: The dimensionality indicates the actuation Degree of Freedom (1D has 1 DoF per exhaust vector, 2D has 2). The dimensionality indicates the aircraft attitudes that can be affected (2 exhaust vectors with 1 DoF each can affect pitch and roll, hence this would be a 2D thrust ...

6

Thrust vectoring allows to control an aircraft when the airflow over its control surfaces has separated. Before thrust vectoring, the range of angles of attack in which an aircraft could be controlled was rather restricted. With the X-31, it was for the first time possible to control a completely stalled aircraft, which enabled much quicker maneuvering in ...

6

Thrust vectoring isn't controlled by the pilot directly, except being able to turn it on or off in various circumstances. If it is on, the aircraft computers control the vectoring based on external conditions, the state of the aircraft and control input.

6

Sure you could, but why would you want to? There's no inherent benefit to be had in vectoring thrust as opposed to using control surfaces. It doesn't simplify things to any extent, it just makes things complicated in other ways. In order to have effective roll control you'd need to space motors out on the wings which could vector in line with the center of ...

6

This statement is using "plane" in the mathematical-geometric sense, which is of course very confusing when we talk about a part of a "plane" in the "flying machine" sense. So, a "one-plane" thrust vectoring nozzle can only move up and down or left and right (typically up and down). So, this gives you pitch control using the thrust, without requiring ...

6

A 90 degree bend in a pipe where the radius of the bend is of order ~one pipe diameter creates the same pressure drop as a length of that same pipe of order ~ten to fifteen times the pipe diameter.

5

While in case most VTOL aircraft, the rotors are tilted, one unique case is the Curtis Wright X-19, which had what the company called tilt-propellers. Curtis Wright at that point was a propeller manufacturer and its designers made the aircraft around the propeller. Image from warbirdinformationexchange.org This in turn, was developed from the X-100 Image ...

4

A very important reason is stagnation. US aircraft development has pretty much stopped cold in the mid-late 1980s, with just the F-22 and F-35 entering production since, and those decades overdue. Meanwhile, the Soviets created and fielded all the types you mention. At the time the current operational generation of US aircraft entered service, TV simply ...

4

If we ignore the losses, maintaining the aircraft at a given altitude requires no power, since no work is done on it. It does, however, require a force, and you seem to confuse force and power. The term efficiency has no meaning (at least no well-defined meaning) when talking about forces. For example, I can hold a weight of 20 kg in my hand, and I could ...

3

Engines (let's say piston engines) do not provide lift. Engines drive wings. Each blade of a propeller is a wing. Each wing (at same size, airfoil, angle of attack, relative speed, altitude) provides the same amount of lift. Both devices below provide the same lift, one flies straight forward, other flies in circle. One is a plane, other is a propeller. ...

3

Some planes have this designed into the engine mounts to offset the more pronounced left turning tendencies of larger engines. "Large" in this case is a 400/500 series Lycoming or Continental. Googling "Bonanza canted engine" will turn up more information than you could ever need and you can probably substitute "bonanza" out for any other model of common ...

3

Gimbaled thrust in 'rocket speak', is equivalent to vectored thrust in 'aviation speak'. Many modern military aircraft use thrust vectoring in order to improve performance, particularly in tight turns, the F22 being an example. The harrier and the F35 also use thrust vectoring to enable VTOL (vertical take off and landing) and/or STOL (short take off and ...

3

An aircraft traditionally has three "degrees of freedom" in aerodynamic maneuverability; pitch, yaw and roll. The number of "dimensions" of thrust vectoring relates directly to how many degrees of freedom can be manipulated using only the vectored engine thrust. Therefore, 2D vectoring allows control over two degrees of freedom (typically pitch plus either ...

3

No, for several reasons What you want is to compensate for the additional lift from downward deflected flaps at the back of a flying wing with vectored thrust. As @Sean points out this will not bring a noticeable net benefit if the lengthwise location of both forces is similar. But that is not all. Besides the force equilibrium around the flying wing you ...

2

In short, yes; the ability to vector thrust to the sides of the aircraft, inducing yaw, does provide an advantage in maneuvering over pitch-only vectoring. Consider the Su-30 "SM" and "MK" variants, which have 3D thrust vectoring. Here's a Su-30 at an airshow (I'm unsure of the exact variant) performing a range of post-stall aerobatics: https://www.youtube....

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