Weren’t they escorted by gunships in Vietnam?
For missions where you expect to encounter opposition the unarmed helos would be accompanied by helo gunships, or for larger high enough priority missions, USAF CAS aircraft.
For missions where you don’t expect to encounter opposition, usually not. Not all cargo or troop movements are into the teeth of the enemy.
Helos in particular are very range and payload limited. Putting a couple guns and gunners on a UH-1 pretty well ate up its entire cargo / troop carrying capacity. So self-protection was mostly impractical.
UH-60s and the larger Viet Nam era helos like early CH-47s were/are more capable, but the weapons vs. payload tradeoff is still pretty steep.
I just realized I lost an entire section of my original post, where I briefly described (with cites) how and where the decision process works re: what airlift request gets what airframe assigned to it. Ugh.
To make a shortened long story even shorter, there are Air Operations Centers that have staffs who look at airlift requests, determine how many/how much/how far/how fast, and assign airframes to missions as available. No ground force commander gets on the radio and specifically requests an Osprey to move his/her people & stuff (or specifically requests an A-10 for CAS, for that matter). Having said that, some missions will require specific capabilities that can only be fulfilled by specific airframes; for example, you’re not inserting a 4-man recon team into a tight landing zone with a MV-22 or CH-53E - they’re both far too big and noisy for that mission. You’re also not going to do a heliborne artillery raid with a Huey - it simply lacks the power to external-lift a M777 howitzer, a pallet of ammo slung under the gun, and a gun crew as passengers
MV-22s work independently more often that not; they are their own squadrons, after all.
Where they work together with CH-53Es (and Hueys, Cobras, Harriers, and the occasional KC-130J) is when the MV-22 squadron has those additional aircraft added to create a “composite squadron”, which makes up the Aviation Combat Element of a Marine Expeditionary Unit. Doctrinally, this is still basically the same setup that the USMC was doing with Phrogs (H-46) for decades before the Osprey was dreamed up.
A/c of the same type are naturally in their own squadrons for administrative, training, etc reasons. But the good points you made earlier in that post, and final sentence is the telling weakness IMO of the MV-22 concept v the cost.
It’s basically doing the role of the H-46, better obviously. But doing it in a revolutionarily different way is limited by the mission itself, ie the limited degree of tactical need to carry very light infantry much further than helo’s can, and the tie to the H-53 (still mortifying to have written H-54, which was my favorite a/c pretty much as a kid, and civilian S-64’s still a cool firefighting tool) and its limitations, in order to carry along any kind of heavy equipment to even a ‘normal’ light infantry standard.
A cool capability for limited cases where the speed and range is really key, but I doubt those are really enough to justify the cost as well as various limitations which revolve mainly around the high disk loading, inherent (the ring vortex state problem, rappelling and dust limits etc). The USMC has been gamely trying to overcome these as you’d expect, but it’s another ‘tax’ on the concept as actually realized, besides the H-53/V-22 mismatch, which is not a minor thing IMO. Then there’s been outright problems not inherent to the concept: it wasn’t that well executed a program even by general US DoD standards.
IMO if one could decide with hindsight, though of course one can’t, cancelling the V-22, or upholding Cheney’s original cancellation decision as SecDef (not to get sidetracked on him with politics as VP) would be a no brainer. But now it’s here, I don’t see a reason to stop producing it, and no contradiction in those positions IMO. Also MV-22’s could perhaps be converted to ASW, AEW, etc a/c to fill out the capability of big deck amphibs as small carriers, then there’s the actual programs to use them as refueling a/c as well as purchase COD versions. So too late now.
LSL, it’s that time again:
“CAS?”
ETA:
Corry**,
“COD?”
CAS = Close Air Support
COD = Carrier Onboard Delivery
ASW = Anti-Submarine Warfare
AEW = Airborne Early Warning
The military loves their TLAs. 
Sorry to repeat, Carrier On-board Delivery, the planes which deliver critical supplies to aircraft carriers underway at sea by landing on them. The USN plans to procure Ospreys as CMV-22B’s for this mission, to replace conventional carrier capable C-2 Greyhound a/c which now do it (a relative of the E-2 Airborne Early Warning a/c).
For the record, I agree with nearly all your objections to the V-22.
Back in the '90s when I was a Marine -53 mechanic & crewmember, the same things were being said: "They’re too fast to be escorted by anything in the MEU ACE** but Harriers, and they’re too slow for Harriers to efficiently fly with them!"; “Same payload as an H-60, twice the speed, but 4x (at that time) the cost!”; “Far too complicated for Marines to maintain in the field!”; etc. I felt back then that an H-60 variant (basically, an Army Black Hawk but with blade & tail fold and a rotor brake, which is pretty close to the airframe the Navy ended up buying a decade later as the MH-60S) would have been a good fit for the HMM** mission set, and **far **cheaper than a new design of any kind, since the H-60 training & logistics pipeline already existed within the Navy.
Acronym decoder:
*- Marine Expeditionary Unit
**- Air Combat Element
***- designator for Marine Medium Helicopter squadrons, back when they still flew the CH-46. Now that they fly the MV-22, they are designated VMMs - Marine Medium Tiltrotor squadrons.
How much bother would air-refueling have been for helicopters instead of the V-22 program? It wouldn’t have given them the same speed and payload but would have made range practically unlimited at much lower cost, no?
Are turboprops better than turbofans for V/STOL capability?
You can’t conduct refueling clandestinely nor in contested airspace nor over enemy troops. It isn’t a drop-in replacement for greater inherent vehicle range.
Your second question doesn’t really make much sense. It’s seeking a reductionist answer to a holistic question.
For vertical lift it’s far more power-efficient to use a turboshaft to generate torque to turn a low speed rotor than it is to use a turbojet to provide direct thrust-based lift.
But the rest of the vehicle mission may not permit the limitations rotors bring. Or may not permit turbojets.
Hence all the creative ideas for tiltrotors, compound helicopters, stopped rotor helos, turbofans shaft-driving lift fans plus direct exhaust lift, etc., all trying to get the best of both worlds. Which so far work, sorta, at the expense of complexity and, well, expense.
There have been air-refueling-equipped US helicopters for a few decades - USAF HH-60 rescue helicopters, Army MH-60 and MH-47 special operations helicopters, USMC CH-53E assault transport helicopters, and USN MH-53E minesweeping helicopters.
However…
Specific difficulties with HAAR (Helicopter Air to Air Refueling) include:
Altitude - helicopters can only go so high before they have to reduce airspeed, due to the aerodynamics of their rotor systems; they also lose engine power with altitude. Consequently, the tanker has to descend thousands of feet below their normal flying altitudes, while the helicopter has to climb well out of theirs, and they meet somewhere in the middle.
Airspeed - The tanker has to slow down to speeds normally associated with final approach & landing, while the helicopter has to keep it’s speed up close to (but not at) it’s maximum speed in order to keep the tanker from stalling & crashing. As a general rule, large fixed-wing aircraft aren’t deliberately flown close to their stalling speeds unless the landing gear is down and there’s a runway in very close proximity to their flight path.
Also, the factors that LSLGuy mentioned. HAAR is not a quiet operation, and it’s slow, so that noise signature will be present for a while… which, in a tactical situation, is A Bad Thing.
Right now, the only fixed-wing aircraft in the US inventory that can be a tanker for HAAR are C-130 variants. The KC-135 and KC-10 can’t safely slow down enough for helicopters to overtake them, and their “jet wash” (generic term for the disturbed air behind and below a large jet with flaps & slats extended and a high power setting) would prevent the helicopter from making contact with the refueling drogue*. The MV-22 is being tested as a tanker with a palletized, roll-on/roll-off AR system, but it’s fuel offload capacity as a tanker is limited due to it’s (relatively) small lifting capability.
*- the MV-22 and CV-22 are now approved for HAAR with the KC-10 in normal operations. This happened after I was out of the jet, so I can’t speak to any specific restrictions there may be on the tanker (specifically, gross weight limitations to accommodate the preferred refueling speed of the V-22).