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MV-22 Osprey Tiltrotor Aircraft MV-22 delivers a Humvee

Picture is from here.

Is any other force to lift the V22 other than its rotors? Is any possibility that the power plants their self are not generating thrust? I was just wondered that such short propellers can lift (especially when VTOL) the aircraft even with additional heavy humvee.

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    $\begingroup$ In horizontal flight, the wings generate all of the lifting force while the rotors are just used for thrust. $\endgroup$
    – Ron Beyer
    Sep 21, 2019 at 13:19

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The lift is provided by the rotors only. The rotors are powered by Rolls-Royce T406 engines, which are turboshafts: all useful generated turbine power is converted into shaft power for the rotors. Note that turboprops do convert some of the exhaust energy directly into propulsion thrust, turboshafts do not.

All helicopters can provide enough rotor thrust to lift their own weight plus that of (internal or external) payload. Wikipedia lists the max. VTOL weight as 23,859 kg, about the same as the CH-47 Chinook double rotor helicopter at 22,680 kg. The Chinook rotors are indeed longer and therefore require less power to generate the same amount of thrust: 4,590 kW for the V-22, 3,529 kW for the Chinook.

From the Wiki page of CH-47 Chinook

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  • $\begingroup$ The Chinook rotors are indeed longer and therefore require less power to generate the same amount of thrust: 4,590 kW for the V-22, 3,529 kW for the Chinook, is that mean that the V-22's is rotate faster? Do you know what is the rotor speed (RPM) for the V-22 when VTOL with the 23,859 kg load? $\endgroup$
    – AirCraft Lover
    Sep 21, 2019 at 9:52
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    $\begingroup$ Excellent illustration of lift gain in efficiency from higher aspect Chinook rotors! (over 25%!). The Osprey's shorter rotors are more suitable for faster forward flight. $\endgroup$
    – Robert DiGiovanni
    Sep 21, 2019 at 9:53
  • $\begingroup$ All turbine power is not converted to shaft power. The efficiency is not 100%, as all of the kinetic energy of the exhaust gas is not converted to shaft power. Some escapes and creates (neglible, as I stated in my answer) thrust. $\endgroup$
    – Jpe61
    Sep 21, 2019 at 11:00
  • $\begingroup$ @Jpe61 Your answer confuses turboprops with turboshafts. The exhaust heat causes problems for ships decks. A combustion engine obviously has an exhaust, the question in the OP was: does any of it contribute to the useful thrust, which is not the case. $\endgroup$
    – Koyovis
    Sep 22, 2019 at 0:55
  • $\begingroup$ @AirCraftLover The defining factor is the rotor tip speed, which needs to remain below the drag divergence speed. A rotor with smaller blades can and does turn faster. At a tip speed of M0.9 and a blade radius of 5.8m, rotation speed would be around 500 RPM. $\endgroup$
    – Koyovis
    Sep 22, 2019 at 1:19
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As in all turboprops, some thrust is derived from the turbine exhaust, but it's very little, compared with the big thrust of those enormous propellers...

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The engines do create some thrust (exhaust gasses), but it is of little significance. Most of the energy from the turbine engine is harvested to turn the propeller as explained on NASA website (for example): NASA: Turboprop Thrust

The exhaust of Osprey engine has actually proven to be quite problematic, as it damages the take-off platform: Wikipedia: Bell Boeing V-22 Osprey (see design section, last paragraph)

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  • $\begingroup$ What is the meaning of this phrase Due to the requirement for folding rotors, their 38-foot diameter is 5 feet less than optimal for vertical takeoff, resulting in high disk loading, especially the phrase 5 feet less than optimal for vertical takeoff? $\endgroup$
    – AirCraft Lover
    Sep 21, 2019 at 9:48
  • $\begingroup$ Longer blades are more efficient (this would make a great question itself), the Osprey cannot use any longer ones because the wing-engine-rotor combo has to be able to fold in for stowage during carrier operations. Picture here: images.app.goo.gl/oa2wzJkW26S1yKcH6 $\endgroup$
    – Jpe61
    Sep 21, 2019 at 11:07
  • $\begingroup$ I think, it is not the case. They use the current size was due to proper calculation. They could extended the wing if it is necessary. This video shows perfectly how it folded. youtube.com/watch?v=_45aUrES-j0. There is a bit more space that can be extended without extended the wing. $\endgroup$
    – AirCraft Lover
    Sep 21, 2019 at 11:54
  • $\begingroup$ Of course longer blade will be more efficient. But, the question is, why they used such short blades if (as I commented above) they still can extend? Of course there was reasons. $\endgroup$
    – AirCraft Lover
    Sep 21, 2019 at 11:56
  • $\begingroup$ On your first reply you said yourself they did proper calculation. If they did proper calculations, I bet they used the rotors the calculations told them to use. They were optimizing two things: VTOL performance and cruise performance. The result is what we see on V-22. And: 5 feet longer rotor blades = 5 feet longer wing = tail moves 5 feet backwards and wing takes 5 feet more room in the front as well. You end up with 10 feet longer aircraft. Maybe thats just a tad too long, I don't know. $\endgroup$
    – Jpe61
    Sep 21, 2019 at 15:42

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