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54 votes
Accepted

Are wings any more efficient at creating lift, versus orienting the engine's thrust downwards?

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 ...
Martin's user avatar
  • 2,766
33 votes

Can you identify this fighter aircraft?

It's a Russian YAK-141 This was the VTOL prototype meant to compete with the Harrier and perform carrier-based work (note: edited for clarity) Designers from the Yakovlev bureau found out, that ...
Machavity's user avatar
  • 6,213
29 votes

Are wings any more efficient at creating lift, versus orienting the engine's thrust downwards?

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 ...
David K's user avatar
  • 1,306
29 votes

Are wings any more efficient at creating lift, versus orienting the engine's thrust downwards?

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. ...
Trevor_G's user avatar
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25 votes
Accepted

Why aren't tilting propellers used as an alternative for ailerons or elevators?

It isn't done because a moving control surfaces is easier to design and build than an engine mount that rotates. Plus the associated structure needed to accommodate the thrust, p-factor, and ...
Romeo_4808N's user avatar
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21 votes
Accepted

Could a VTOL aircraft use a helipad for landing/taking off?

Not necessarily The two key elements are aircraft mass, and how that mass is kept aloft. You can probably get a Chinook onto the landing pad of a cruise liner, but you would want to check first if the ...
GremlinWranger's user avatar
19 votes
Accepted

How does the F-35B not flip over during transition?

To try and change lift by changing fan blade speed would be too slow to modify the lift for "tiny" and "delicate" changes in how the plane hovers. Like a helicopter, the F-35 is ...
Albert D. Kallal's user avatar
18 votes

How much thrust is lost through a curved exhaust nozzle?

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 ... ...
Camille Goudeseune's user avatar
17 votes

How does the F-35B not flip over during transition?

Your assumptions (constant thrust for both lift fan and exhaust) are wrong. From wikipedia: "For pitch control, the areas of exhaust nozzle and LiftFan inlet are varied conversely to change the ...
Sanchises's user avatar
  • 13.4k
14 votes

How does the F-35B not flip over during transition?

From what is available on the internet, the F35B's lift fan is more than just a simple shrouded fan. There is at least some variable guide vanes functioning as nozzle. So to answer your question, no, ...
Meatball Princess's user avatar
14 votes

How do you stay stable when landing / taking off an F-35 during a VTOL landing/takeoff?

The F-35-B STOVL variant of the Lockheed-Martin F-35 Lightning II gets its V/STOL / STOVL capabilities from the Rolls-Royce LiftSystem, which consists of four main components: The Three Bearing ...
Jörg W Mittag's user avatar
11 votes

How does the F-35 hover?

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 ...
BarrowWight's user avatar
10 votes
Accepted

How do you stay stable when landing / taking off an F-35 during a VTOL landing/takeoff?

The tail rotor of a helicopter is primarily there to counteract the torque of the main rotor. The F-35's lift fan is counter-rotating such that it cancels its own torque. In addition to the lift fan, ...
Rob McDonald's user avatar
  • 13.5k
9 votes

Why does the US Marine Corps fly the Harrier, a VTOL or operationally STOVL aircraft?

Because when selecting aircraft the requirements were for close air-support and to be able to operate from amphibious assault ships like the USS Tarawa and the USS Nassua. These ships have very small ...
Ron Beyer's user avatar
  • 36.2k
8 votes

Could wing tilting be a mechanism for VTOL and high angle of attack for jetliners?

What you describe is called a tiltwing. It has wing-mounted engines which swivel with the wing so their thrust points up for the VTOL mode. Building a tiltwing airliner will face two challenges: ...
Peter Kämpf's user avatar
8 votes

Why is the F-35B's elevator not in neutral position when in vertical flight mode?

In this video you can see it better I think: I drew on a screenshot of the video from the side where you can see the air moving under the aircraft. Compare this to ...
Jan's user avatar
  • 2,398
7 votes

What is the difference in VTOL technology between British Aerospace Harrier II and F-35B?

the F35 has a ton of electronics that the Harrier could only dream about, but I will focus on propulsion differences. The biggest is that the F35B uses a separate lift fan in front of the engine, ...
Pilothead's user avatar
  • 20.7k
7 votes

Why didn't we see many VTOL aircraft in the history of aircraft development?

VTOL (and STOVL) are concepts which were conceived as a result of not having large aircraft carriers or the space for a long runway. The primary feature of these aircraft is to enable them to take off ...
bjelleklang's user avatar
  • 4,165
7 votes

Can you identify this fighter aircraft?

Russian YAK-141 aka YAK-41 VTOL (vertical takeoff and landing). https://en.wikipedia.org/wiki/Yakovlev_Yak-141
Tinynumbers's user avatar
7 votes

How does the Urbanaero flying car move forward?

It would fly forward the same way a quadcopter does: have the aft motor controller increase current, thereby increasing aft fan lift, creating a pitching moment downward and moving the fan arcs out ...
Romeo_4808N's user avatar
  • 74.1k
7 votes

Could a VTOL aircraft use a helipad for landing/taking off?

You mention air forces but don't specifically restrict the question to current military types, so considering commercial VTOL aircraft this is exactly what Joby and other air taxi companies are ...
Pilothead's user avatar
  • 20.7k
6 votes
Accepted

Why does the V-22 Osprey have twin stabilizers?

The V-22 was designed to be operated by the US Marine Corps on-board US aircraft carriers. Any airplane that operates off of a carrier has to be relatively compact in order to be able to fit onto the ...
GdD's user avatar
  • 54k
6 votes

How does the V22 Osprey manage such high rotor speeds without shock waves?

The Osprey's engines drive the rotors at 412 RPM in heli mode or 333 RPM in forward-flight mode, according to this article. With a rotor radius of 5.8m, that puts the tip velocity at 250m/s, or about ...
aerobot's user avatar
  • 865
6 votes
Accepted

Can a VTOL jet such as the Harrier enter a Vortex Ring State?

The main problem with VRT is the airflow through the rotor which is disturbed because it is ingesting its own downwash. The large area of air accelerated downwards keeps being sucked back in to the ...
Koyovis's user avatar
  • 61.8k
6 votes

Carrier VTOL takeoff or not?

The rolling takeoff is a STOVL or Short Takeoff and Vertical Landing operation. The F-35B is too heavy to hover with full fuel and a warload, but can use its vertical lift system to augment lift ...
Romeo_4808N's user avatar
  • 74.1k
6 votes

What are the disadvantages of a Tail providing lift? (tandem-wings included)

A lifting tail just means lower static stability. You are correct, flying in the downwash of the wing makes the tail less efficient. But that does not mean it is all bad: Since downwash increases ...
Peter Kämpf's user avatar
6 votes

How much thrust is lost through a curved exhaust nozzle?

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.
niels nielsen's user avatar
6 votes

Different Engine/Prop Sizes on Same Wing/Single Craft?

The Bird Innovator was an American four-engined executive amphibious airplane modified from a Consolidated PBY Catalina by the Bird Corporation. During the late 1960s Forrest Bird and his Bird ...
Mike Sowsun's user avatar
  • 37.8k
6 votes

Portable VTOL Startup

15 minutes is not very long in flying, and that level of endurance would only be acceptable for a motorglider. You want an hour at minimum, and that still only makes it an amusement device. Electric ...
John K's user avatar
  • 132k

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