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I've recently learned of the Bell Boeing V-22 Osprey and it appears to be a very advanced and useful vehicle. I can instantly think of reasons why the Osprey would be successful such as:

1) It can take off in small places and land in small places unlike planes
2) It can hover
3) It can turn into a plane and fly fast
4) It can pick up things like cars without the need to carry it inside like planes
5) It can easily fly sideways and backwards

So my questions are:

1) Why hasn't the Osprey advanced/been successful. For example how the F-15 went to the F-16 then the F-35 etc.
2) What made Boeing choose to have rotors instead of the faster jet engine?

The only possible reasons I can think of are things such as:

1) Stealth/noise, the Osprey requires large rotors and probably makes double the noise as a helicopter or plane would make
2) Maintenance costs, a helicopter requires more maintenance than a plane, I'd think the Osprey requires more maintenance than a helicopter or plane
3) Cost, the Osprey probably costs more than an average plane or helicopter

Though I'm not sure of the real main reason as surely those reasons can be fixed.

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    $\begingroup$ This question is somewhat broad and your questions seem to be based on misunderstandings. It's difficult to see where to start with an answer. $\endgroup$ – Dan Hulme Oct 31 '15 at 16:47
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    $\begingroup$ Whose to say it hasn't been successful? It has had a number of crashes, but it's in fairly widespread use, as far as I know. As far as why it hasn't been replaced, it's a relatively new aircraft. Most of them were delivered in the 2000s. Compare with the B-52s that were delivered in the 60s and are still flying or the F-15s that were delivered in the 70s and are still flying. $\endgroup$ – reirab Oct 31 '15 at 17:14
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    $\begingroup$ Can you explain in what way "the F-15 went to the F-16 then the F-35 etc."? $\endgroup$ – JulianHzg Oct 31 '15 at 17:26
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    $\begingroup$ The F-16 is not a development from the F-15. The F-15 was developed by McDonnell Douglas while the F-16 was developed by competitor General Dynamics, with a lot of overlap in the timelines. $\endgroup$ – JulianHzg Oct 31 '15 at 19:00
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    $\begingroup$ "The F-(number) are just different versions of the same plane." No they're not. Not even slightly. The "F" just means "fighter". If you look at the F-15 and F-16 on Wikipedia, you'll see that they're completely different planes, completely unrelated to each other. The F-15 is a two-engined air superiority fighter built by McDonnell Douglas (now part of Boeing); the F-16 is a significantly smaller, single-engined multi-role fighter built by General Dynamics (now part of Lockheed Martin). $\endgroup$ – David Richerby Oct 31 '15 at 19:13
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Why was the Bell Boeing V-22 Osprey not worked on more?

The Osprey idea is an old one and it never worked well. For example, I have found a patent form 1921 (see the picture) for a flying machine that has some common points with the Osprey. Large diameter propellers are not efficient for planes and small rotors are not suitable for helicopters. A hybrid, like Osprey, has the advantage of not needing a runway to land or take off but at the same time, once in the air, it has to pay the price of using two inefficient propellers for flying hundreds of kilometers. Also, if it is used more as a helicopter the rotors are not as efficient as the ones of a true helicopter.

Traian Vuia Helicopter Flying machine, authour Traian Vuia, April 1921.

Boeing V-22 Osprey Bell Boeing V-22 Osprey

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The Osprey has arguably been quite successful considering the circumstances. As Energizer777 points out, the basic idea is not new, and there were many engineering challenges to create a viable aircraft. That these challenges were solved and the plane is now in production and active service seems to be a pretty big success. Also, this has all happened relatively recently. The V-22 first flew in 1989 while the F-15 and F-16 both date back to the early 1970's (and are still in active service). The challenges in refining the design pushed introduction of the V-22 out until 2007. The design just hasn't had enough time to mature past the first successful application. You might consider the civilian tilt-rotor AW609, currently targeted for certification in 2017, as the next advancement of the design.

Props/rotors are more efficient than a jet engine at low speeds. Given that the slow and vertical portions of the flight are very important to the design, this decision makes sense. The prop wash also flows over the wing, allowing the wing to be more effective with a short span. Using turboshaft engines rather than jets also allows one engine to drive both rotors if the other engine fails, making single engine operation easier.

You are right about the drawbacks of the design. The V-22 is noisy and not as agile has a helicopter in slow flight. Maintenance requirements are high and were certainly an issue early on in the introduction to service. And upfront costs are also more than a helicopter or airplane of comparable size. However, the capabilities you listed first are worth these added costs, at least to those that have purchased/ordered the V-22.

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It doesn't need to be updated

It already does everything the Marines need it to do. Replacing it would be expensive for no reason.

The other aircraft you mention, F-15, F-16, F-35, F-22 are a little different - the F-35 is replacing the F-18/F-16. The F-18 replaced the F-14. The F-22 is mostly a replacement for the F-15. Why? Because these get outdated.

The USAF's potential enemies build a fighter that can beat the F-15, so you build a fighter that can beat their new one. Repeat. This has happened since the dawn of the fighter aircraft.

Transport aircraft, however... what would you improve? It's already about as fast as it's going to get without a lot of money being spent, and as capable.

Quite simply, there's no need to replace it yet. That doesn't mean it's been unsuccessful.

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  • $\begingroup$ To add, the MV-22B is mostly a replacement for helos (namely the CH-46E and CH-53E), to which the MV-22B is generally superior: greater combat radius, almost doubled cruise speed / shorter transit time, good payload, and much higher cruise altitude, putting it above most MANPADS and AAA. Consequently, the V-22 can get things done faster and with less risk, being less vulnerable for less time each mission. $\endgroup$ – Hephaestus Aetnaean Jan 12 '17 at 12:46
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I'd argue that it's been quite successful. Think various comments have cleared that up, as well as modifying your definition of "successful."

A necessary forerunner to it was the XV-15. Yes, there were earlier aircraft, but this didn't work well until smaller turboprop engines, with sufficient power density became available. Prior to that, the engines were usually located in the fuselage and had driveshafts carrying the power to the nacelles on the wingtips. These were heavy and prone to failure.

As for why the Osprey has props/rotors instead of jets, let's talk about thrust and power. To get off the ground, you need more thrust than you have weight. Typically, if you're going to do VTOL, you need 110% as much. So a 2,000 pound aircraft needs at least 2,200 pounds of thrust to takeoff vertically, much less hover. Hover requires even more.

There are multiple ways to make thrust:

  • grab a relatively small amount of air mass and accelerate the heck out of it. This is what turbojets and afterburning low-bypass turbofans do, as found in most fighter planes. There will be high-speed jet efflux, high temperatures and comparatively high fuel consumption with this route. The Harrier does this, as does the F-35B. Neither can do it for very long, though (significant fuel consumption), and you don't want to be anywhere nearby, on the ground, when they do it (noisy, windy, hot). If you need to go FAST, you need to do this.
  • grab a relatively large amount of air mass and accelerate it a little bit. This is what the rotor does on a helicopter and, to a lesser degree, a propeller on an airplane. The rotor/prop wash has nowhere near the intensity of a jet engine's exhaust. There's also less heat and much less fuel consumption. But you can't go as fast (speed is limited by the airspeed of the rotor/prop wash).
  • somewhere in between. High bypass turbofans on modern jetliners grab more air than turbojets, but less than props/rotors, and they accelerate the air more than a prop/rotor but less than a turbojet. Lower fuel consumption than the turbojet and less noise but higher speed than a prop/rotor.

If they could've done it with a single rotor, and found a way to angle that forward for "airplane" mode, they'd have done so; a single, large rotor would be more efficient than a pair of smaller rotors. The simplest mechanism they could develop, which would provide the capabilities of both airplane and helicopter, was a twin-engine design. You get a faster cruise speed and a longer range than any helicopter in the inventory and a broader flight envelope than any airplane (VTOL and hover).

Additionally, you need a degree of agility for maneuvering in hover. So you need the ability to change the thrust vectors while hovering; the "airplane" flight controls (ailerons, elevators and rudder) are useless in this mode. To accomplish this, the props/rotors have collective and cyclic controls like a helicopter. If you flatten the pitch on the forward part of the rotation, that will change the thrust vector to push down-and-aft, instead of just down. Coordinate this between the two engines and you have translation forward/aft, side-to-side and pivot, just like a helicopter.

To my knowledge, no one has succeeded in making a jet engine which can do this.

A jet-engined variant would likely need some kind of 2D thrust vectoring, downstream of the actual engine. There are existing examples of this:

  • The F-22 does 1D thrust vectoring (each engine nozzle can pitch up/down). Used differentially, this can augment pitch AND roll.
  • The Su-35 does something similar to the F-22
  • The F-35B, as mentioned, does limited 1D thrust vectoring for STOVL
  • Some advanced Mig-29s do full 2D thrust vectoring with both nozzles
  • The F-16 VISTA demonstrator did full 2D thrust vectoring
  • The X-31 also had basic 2D thrust vectoring, due to some deflector "paddles" aft of the engine. This is similar to the directional vanes used on the original V-2 rocket.

Assuming someone can come up with a usable 2D thrust vectoring system, mounted to the aft end of high-bypass turbofan (all the mentioned examples are turbojets, lower-bypass turbofans or rockets), it might be possible to do a jet-powered variant, at some point in the future.

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    $\begingroup$ Well reasoned, however, I take umbrage with your thrust vectoring comments. I would say that thrust vectoring is NOT still quite experimental. We have several discussion here, here, and notably on 2 line-use fighters here. $\endgroup$ – FreeMan Jan 13 '16 at 17:09
  • $\begingroup$ Excellent feedback @FreeMan. I've modified the section about the thrust vectoring, including some links. $\endgroup$ – Meower68 Jan 13 '16 at 23:27
  • $\begingroup$ The F-35B... does limited 1D thrust vectoring. The F-35B actually has "3D" TVC in hover mode. The rear nozzle can wiggle forward/aft/left/right, the roll posts provide roll control, and the lift fan's thrust can also be vectored somewhat. In a hover, the F-35B can basically translate forward/back/left/right and turn in place. (Oh, sorry, I thought this was posted today, not last year.) $\endgroup$ – Hephaestus Aetnaean Jan 12 '17 at 12:31

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