We’re back after a quick hiatus. I’ll be honest, I wasn’t sure how long it would be before I uploaded this part. And at one point was seriously scrapping the series because there was something I hadn’t considered. People might choose to write articles on the same subject as something I was working on, release it before me and essentially make all my hard work for nothing. But after having therapy time with EternalDarkness, I decided to just put it on the backburner for a week or two and heavily modify it before publishing.

Also, to clarify, when I say thrust vectoring, I mean an aircraft’s ability to manipulate the direction of thrust.

Background

So, you’ve got thrust to power your aircraft. But what if you see a brick wall appear in your way and need to slow down quickly? Or maybe you want to give the middle finger to physics and fly backwards? Or perhaps you’ve purchased a plane, but suddenly decide you actually wanted a helicopter instead.

Believe it or not, vectoring thrust is a very common thing. Not just on aircraft, but other modes of transport too. Said inferior transport types include boats with an outboard motor, hovercrafts and your bedroom pedestal fan… Although I generally advise using the latter as a mode of transport.

Squirrel Bedroom Desk Reveal

Anyway, you get the picture. Thrust vectoring is literally everywhere.

Reverse Thrust

I’m going to start with the most boring type of thrust vectoring. Reverse Thrust.

Scenario Time. You’re coming into land on a very long runway. You’re pretty relaxed about the whole situation as there’s ample room to come to a stop. But then you see it. Two men carrying a large sheet of glass across the runway. What do you do? Well, for a start fire Air Traffic Control for doing a god-awful job. But, most importantly, hit the reverse thrust lever.

Basically, reverse thrust is a great way of coming to a stop very quickly, which is why you’ll find a lot of airliners employing this method of braking. Also, fun fact, the reverse thrust system utilises what they call a “weight on wheels switch” to prevent accidental operation in the air, meaning reverse thrust can only be deployed when the wheels are on the ground.

There are many different ways of deflecting thrust in the opposite direction. And the 3 main types are depicted in the illustration below:

The Three Main Types of Reverse Thrust Mechanisms

V/STOL (Vertical/Short Take Off and Landing)

I’m going to break this section off into subheadings because there’s quite a bit of ground to cover.

Background

VTOL is what happens when a plane wants to sometimes identify as a helicopter. It’s a useful function, especially in areas that don’t have forgiving terrain. However, it is very important to note that VTOL isn’t on its own an engine type. It’s a system and by that, I mean if you were in forward flight and all the VTOL components of your engine either stopped working or casually fell off, you aircraft would likely be fine until you get to the landing site and find out it’s a helipad. Mistakes were made or challenge accepted are the only two outlooks one would have in that scenario.

So how do you get a plane to jump up and down with joy without dropping it from a crane onto a trampoline? Well you have to counteract the aircraft’s weight/mass. If your aircraft weight 1 kilogram, then you need a force that exceeds 1 kilogram in order to lift it up.

Tiltrotor/Tiltwing

This is arguably, in theory, the easiest way of achieving VTOL through thrust vectoring. You’re not really adding any additional engines. You’re essentially taking a helicopter and a prop plane and taking them to the Pokémon breeding centre.

As ever with most cool aerospace designs, it had its origins in World War II in the form of the Tilt Rotor Focke-Achgelis Fa 269. Unfortunately, the design never really made it passed the mock-up phase before being bombed out of existence.

A Small Focke-Achgelis Fa 269 Model

Enter the American company Bell, which the proceeded to milk the Tilt Rotor designs from 1955 for all they’re worth. Coincidently, they mainly specialise in helicopters. They came up with designs for the XV-3, XV-15, the iconic V-22 Osprey and its successor, the V-280 Valor.

The V-280 Valor

Tilt Wing designs don’t really get much love though, with the most famous probably being the LTV XC-142, which doesn’t really have the same ring to it as V-22. However, while initially more complex in it’s design, the tiltwing does actually offer some notable advantages over the tiltrotor:

• Less downforce is dispersed by the wing (some of the downforce on a Tilt Rotor strikes the wing, making it less efficient).
• Because the wing moves, the wings higher angle of attack in transition from vertical to forward flight generates more lift, thus decreasing stall speed and just overall making the transition a more pleasant experience.

The LTV XC-142

Tilt Jet

Tilt Jets are the unwanted child between true thrust vectoring nozzle jets and tilt rotors. There’s not really a whole lot to say about them apart from they would be your go-to choice if you wanted to use a tilt-rotor-like mechanism, but for an aircraft you wanted to go supersonic… You’ll never guess which company almost got their hands on a Tilt Jet.

Bell XF-109 concept

VTOL Thrust Vectoring Nozzles

Of course, as a UK resident, I now have to pay mandatory respect to our lord and saviour, the Hawker Siddeley Harrier. There are many ways one can vector thrust from horizontal to vertical using nozzles. The most notable for me is of course the nozzles on the Rolls-Royce Pegasus engine.

The Rolls-Royce Pegasus engine is a turbofan. For those that read my article on axial flow turbines you’ll know that the turbofan can have different compressor stages. For the first set of nozzles at the front, the air is taken from the Low-Pressure compressor stage, with the exhaust air being expelled from the rear nozzles.

Harrier Jump Jet

Of course, the Harrier isn’t the only aircraft that employs this method of VTOL. The happiest aircraft on the planet also uses a similar mechanism. Introducing, the X-32:

The Cure for Depression

The X-32 uses a similar concept to the Harrier, but it was more refined and was able to utilise an afterburner (unlike the Harrier). Unfortunately, the US government decided to change the Joint Strike Fighter Specifications after the prototype was made, giving the yet to be unveiled X-35 the edge, giving Lockheed chance to update their aircraft. This effectively penalised the X-32, which led to it losing to the X-35 (later F-35).

X-32 Production Mock-up (to the new specifications set by the government)

I don’t know about you guys but I’m pretty sour about that outcome (not that the F-35 is a bad plane, I just think it was very unfair). Speaking of the F-35:

The YAK -141 utilises a very unique nozzle design:

YAK-141 in VTOL Configuration

If that configuration seems familiar, it’s because it’s almost identical to that used on the F-35B. At least the nozzle design is (a lift fan is used on the F-35 in place of the 2 small jet engines on the YAK-141). It’s quite fun to watch though:

F-35B Nozzle Movement

2D and 3D Thrust Vectoring

So, you’ve got a plane. It’s a great design, but the laws of physics tell your plane “no” every time it wants to do a cool stunt. So, what do you do?

Slap some thrust vectoring nozzles on. This modification alone will make physics cry in the corner of your room and tell you to not talk to it.

Thrust vectoring comes in 2 flavours. F-22 and Vodka. F-22 is the 2D kind and allows your plane to do basic mouth dropping manoeuvres like this:

F-22 Putting Gymnasts to Shame

The Second variety of thrust vectoring is 3D. It’s basically extreme mode for pilots. While 2D thrust vectoring allows for thrust vectoring along the pitch axis (or if you’re weird maybe you make an engine that only does the roll or yaw axis), 3D thrust vectoring allows for vectoring simultaneously along the pitch, roll and yaw axis. Honestly, for this reason alone, I want to go to Russia:

The SU-35 Putting the F-22 to Shame

3D Thurst vectoring may look like a bit of a gimmick, but it can have a lot of useful features, such as rapidly reducing speed (to get behind an enemy), providing short take off capability, providing additional features for out turning an enemy jet (again, meaning you can get behind them faster) , retaining control at high altitudes, and of course, retaining agility at low speeds, which is important if you accidentally use up all your forward “energy” (ironically sometimes caused by using thrust vectoring).

There’s a bit of debate over whether thrust vectoring is relevant in the modern era of fighter jets, with it largely coming down to how optimistic you are about missile/radar technology and which aircraft you’re fighting against. But I think we can all agree it makes for a fantastic show. Plus, if we’re still giving fighter aircraft guns, why not give them moving nozzles too?

Conclusion

Thrust vectoring is everywhere and it’s here to stay. It provides up with useful properties to play with, from VTOL to defying gravity and allowing aircraft to brake harder and faster. It’s an essential in both the military and commercial markets and without it, life would be a little bit less fun.

Next Time

I may or may not make Tully very happy.

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